Author name code: vlahos
ADS astronomy entries on 2022-09-14
author:"Vlahos, Loukas" 
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Title: Magnetic field spectral evolution in the inner heliosphere
Authors: Sioulas, Nikos; Huang, Zesen; Shi, Chen; Velli, Marco;
   Tenerani, Anna; Vlahos, Loukas; Bowen, Trevor A.; Bale, Stuart D.;
   Bonnell, J. W.; Harvey, P. R.; Larson, Davin; Pulupa, arc; Livi,
   Roberto; Woodham, L. D.; Horbury, T. S.; Stevens, Michael L.; Dudok
   de Wit, T.; MacDowall, R. J.; Malaspina, David M.; Goetz, K.; Huang,
   Jia; Kasper, Justin; Owen, Christopher J.; Maksimović, Milan; Louarn,
   P.; Fedorov, A.
Bibcode: 2022arXiv220902451S
Altcode:
  The radial evolution of the magnetic field fluctuations spectral
  index and its dependence on plasma parameters is investigated using
  a merged Parker Solar Probe ($PSP$) and Solar Orbiter ($SO$) dataset
  covering heliocentric distances between $0.06 ~ \lesssim R ~\lesssim
  1$ au. The spectrum is studied as a function of scale, normalized to
  the radially dependent ion inertial scale $d_{i}$. In the vicinity of
  the Sun, the magnetic spectrum inertial range is limited with a power
  law exponent $\alpha_{B}$ consistent with the Iroshnikov-Kraichman
  phenomenology of Alfvénic turbulence, $\alpha_{B} = -3/2$, independent
  of plasma parameters. The inertial range of turbulence grows with
  distance from the Sun, progressively extending to larger spatial
  scales, while at the same time steepening towards a Kolomogorov
  scaling, with a mean value of $\alpha_{B} =-5/3$. Highly alfvénic
  intervals seem to retain their near-Sun scaling and only show a minor
  steepening with distance. In contrast, intervals, where turbulence
  is characterized by large magnetic energy excess and no dominance of
  outwardly propagating Alfvénic fluctuations, appear to have spectra
  that steepen significantly with distance from the Sun, resulting in
  slightly anomalously steep inertial range slopes at $1~au$. Though
  generically slower solar wind streams exhibit steeper spectra, the
  correlation can be attributed to the underlying positive correlation
  between solar wind speed and alfvénicity, i.e. to the relatively rare
  occurrence of highly Alfvénic slow wind.

Title: Magnetic Field Intermittency in the Solar Wind: Parker Solar
    Probe and SolO Observations Ranging from the Alfvén Region up to 1 AU
Authors: Sioulas, Nikos; Huang, Zesen; Velli, Marco; Chhiber, Rohit;
   Cuesta, Manuel E.; Shi, Chen; Matthaeus, William H.; Bandyopadhyay,
   Riddhi; Vlahos, Loukas; Bowen, Trevor A.; Qudsi, Ramiz A.; Bale,
   Stuart D.; Owen, Christopher J.; Louarn, P.; Fedorov, A.; Maksimović,
   Milan; Stevens, Michael L.; Case, Anthony; Kasper, Justin; Larson,
   Davin; Pulupa, Marc; Livi, Roberto
Bibcode: 2022ApJ...934..143S
Altcode: 2022arXiv220600871S
  Parker Solar Probe (PSP) and SolO data are utilized to investigate
  magnetic field intermittency in the solar wind (SW). Small-scale
  intermittency (20-100 d <SUB> i </SUB>) is observed to radially
  strengthen when methods relying on higher-order moments are considered
  (SF<SUB> q </SUB>; SDK), but no clear trend is observed at larger
  scales. However, lower-order moment-based methods (e.g., partial
  variance of increments; PVI) are deemed more appropriate for examining
  the evolution of the bulk of coherent structures (CSs), PVI ≥ 3. Using
  PVI, we observe a scale-dependent evolution in the fraction of the data
  set occupied by CSs, f <SUB>PVI≥3</SUB>. Specifically, regardless
  of the SW speed, a subtle increase is found in f <SUB>PVI≥3</SUB>
  for ℓ = 20 d <SUB> i </SUB>, in contrast to a more pronounced radial
  increase in CSs observed at larger scales. Intermittency is investigated
  in relation to plasma parameters. Though, slower SW speed intervals
  exhibit higher f <SUB>PVI≥6</SUB> and higher kurtosis maxima, no
  statistical differences are observed for f <SUB>PVI≥3</SUB>. Highly
  Alfvénic intervals display lower levels of intermittency. The
  anisotropy with respect to the angle between the magnetic field
  and SW flow, Θ<SUB>VB</SUB> is investigated. Intermittency is
  weaker at Θ<SUB>VB</SUB> ≍ 0° and is strengthened at larger
  angles. Considering the evolution at a constant alignment angle, a
  weakening of intermittency is observed with increasing advection time
  of the SW. Our results indicate that the strengthening of intermittency
  in the inner heliosphere is driven by the increase in comparatively
  highly intermittent perpendicular intervals sampled by the probes with
  increasing distance, an effect related directly to the evolution of
  the Parker spiral.

Title: Statistical Analysis of Intermittency and its Association
    with Proton Heating in the Near-Sun Environment
Authors: Sioulas, Nikos; Velli, Marco; Chhiber, Rohit; Vlahos, Loukas;
   Matthaeus, William H.; Bandyopadhyay, Riddhi; Cuesta, Manuel E.; Shi,
   Chen; Bowen, Trevor A.; Qudsi, Ramiz A.; Stevens, Michael L.; Bale,
   Stuart D.
Bibcode: 2022ApJ...927..140S
Altcode: 2022arXiv220110067S
  We use data from the first six encounters of the Parker Solar Probe
  and employ the partial variance of increments (PVI) method to study the
  statistical properties of coherent structures in the inner heliosphere
  with the aim of exploring physical connections between magnetic field
  intermittency and observable consequences such as plasma heating and
  turbulence dissipation. Our results support proton heating localized
  in the vicinity of, and strongly correlated with, magnetic structures
  characterized by PVI ≥ 1. We show that, on average, such events
  constitute ≍19% of the data set, though variations may occur depending
  on the plasma parameters. We show that the waiting time distribution
  (WT) of identified events is consistent across all six encounters
  following a power-law scaling at lower WTs. This result indicates that
  coherent structures are not evenly distributed in the solar wind but
  rather tend to be tightly correlated and form clusters. We observe
  that the strongest magnetic discontinuities, PVI ≥ 6, usually
  associated with reconnection exhausts, are sites where magnetic
  energy is locally dissipated in proton heating and are associated
  with the most abrupt changes in proton temperature. However, due to
  the scarcity of such events, their relative contribution to energy
  dissipation is minor. Taking clustering effects into consideration,
  we show that smaller scale, more frequent structures with PVI between
  1 ≲ PVI ≲ 6 play a major role in magnetic energy dissipation. The
  number density of such events is strongly associated with the global
  solar wind temperature, with denser intervals being associated with
  higher T <SUB> p </SUB>.

Title: Particle heating and acceleration by reconnecting and
    nonreconnecting current sheets
Authors: Sioulas, Nikos; Isliker, Heinz; Vlahos, Loukas
Bibcode: 2022A&A...657A...8S
Altcode: 2021arXiv210708314S
  In this article, we study the physics of charged particle energization
  inside a strongly turbulent plasma, where current sheets naturally
  appear in evolving large-scale magnetic topologies, but they are
  split into two populations of fractally distributed reconnecting and
  nonreconnecting current sheets (CS). In particular, we implemented
  a Monte Carlo simulation to analyze the effects of the fractality
  and we study how the synergy of energization at reconnecting CSs
  and at nonreconnecting CSs affects the heating, the power-law high
  energy tail, the escape time, and the acceleration time of electrons
  and ions. The reconnecting current sheets systematically accelerate
  particles and play a key role in the formation of the power-law tail in
  energy distributions. On the other hand, the stochastic energization
  of particles through their interaction with nonreconnecting CSs can
  account for the heating of the solar corona and the impulsive heating
  during solar flares. The combination of the two acceleration mechanisms
  (stochastic and systematic), commonly present in many explosive events
  of various sizes, influences the steady-state energy distribution,
  as well as the transport properties of the particles in position- and
  energy-space. Our results also suggest that the heating and acceleration
  characteristics of ions and electrons are similar, the only difference
  being the time scales required to reach a steady state.

Title: Statistical analysis of intermittent structures and their
    implications on heating during the first six PSP encounters.
Authors: Sioulas, Nikos; Velli, Marco; Matthaeus, William; Vlahos,
   Loukas; Qudsi, Ramiz; Chhiber, Rohit; Bandyopadhyay, Riddhi; Bowen,
   Trevor; Stevens, Michael; Bale, Stuart
Bibcode: 2021AGUFMSH35C2098S
Altcode:
  We use high-resolution Parker Solar Probe data from the first six
  encounters to study the statistical properties of intermittent,
  coherent structures and investigate the physical connections between
  magnetic field intermittency and observable consequences such as solar
  wind dissipation and plasma heating. More specifically, the Partial
  Variance of Increments (PVI) method is employed to estimate the fraction
  of coherent structures in our dataset. We find that coherent structures
  constitute ~2.5 % of the entire dataset, roughly one-tenth of the value
  reported in the near-earth environment, indicating in-situ formation
  of intermittent magnetic field structures developed by the non-linear
  turbulent cascade. We move on to analyze waiting time distributions
  of identified events by imposing thresholds on the PVI time series. We
  show that the shape of the waiting time distribution strongly depends
  on the resolution of the magnetic field time series and the time-lag
  used to estimate the PVI time series. We proceed to analyze the
  contribution of coherent structures to the heating of the Solar Wind
  (SW). We find a positive correlation between proton temperature and
  PVI, indicating that proton heating is localized in the vicinity and
  strongly correlated with intermittent structures. More precisely,
  the strongest discontinuities in the magnetic field are associated
  with the most abrupt changes in proton temperature . Still, due to the
  scarcity of such events, their relative contribution to the dissipation
  of energy in the solar wind is minor. We propose that smaller scale,
  more frequent, magnetic field variations of PVI events in the range 2
  &lt; PVI&lt; 6, determine the global solar wind temperature. Finally,
  our results indicate that due to the low density of coherent structures
  in the young solar wind environment, intermittent heating is not as
  pronounced as in the outer part of the heliosphere.

Title: Are Nanoflares Responsible for Coronal Heating?
Authors: Vlahos, Loukas; Isliker, Heinz; Sioulas, Nikos
Bibcode: 2021arXiv210801722V
Altcode:
  Parker (1983) suggested a mechanism for the formation of current sheets
  (CSs) in the solar atmosphere. His main idea was that the tangling of
  coronal magnetic field lines by photospheric random flows facilitates
  the continuous formation of CSs in the solar atmosphere. This part
  of his idea represents one of the many ways by which the turbulent
  convection zone drives the formation of coherent structures and CSs
  in the solar atmosphere. Other mechanisms include emerging magnetic
  flux, interaction of current filaments, and explosive magnetic
  structures. However, there are two unproven assumptions in the initial
  idea of Parker for the coronal heating through nanoflares that must be
  re-examined. They are related to his suggestion that {ALL CSs formed
  are led to magnetic reconnection and that magnetic reconnection heats
  the plasma in the solar atmosphere. Let us discuss these two assumptions
  briefly in this short comment: (1) Are ALL coherent structures and CSs
  formed by the turbulent convection zone reconnecting? Does turbulence
  associated with non-reconnecting CSs play a role in the heating of
  the corona? (2) Does magnetic reconnection heat the plasma?

Title: Stochastic Turbulent Acceleration in a Fractal Environment
Authors: Sioulas, Nikos; Isliker, Heinz; Vlahos, Loukas
Bibcode: 2020ApJ...895L..14S
Altcode: 2020arXiv200502668S
  We analyze the stochastic acceleration of particles inside a fully
  developed turbulent plasma. It is well known that large-amplitude
  magnetic fluctuations and coherent structures in such an environment
  obey a fractal scaling, and our specific aim is to study for the first
  time the effects of the fractality of these environments on stochastic
  acceleration. We have shown that an injected Maxwellian energy
  distribution is heated and forms a high-energy tail in a very short
  time. Using standard parameters for the low solar corona, the injected
  Maxwellian distribution of electrons gets heated from the initial
  100 eV to 10 KeV, and the power-law index of the high-energy tail is
  about -2.3. The high-energy tail starts around 100 keV, and reaches
  10 MeV. The index of the power-law tail depends on the system size,
  and it is in good agreement with observed values for realistic system
  sizes. The heating and acceleration process is very fast (∼2 s). The
  reason why the acceleration time is so short is that the particles
  are trapped within small-scale parts of the fractal environment, and
  their scattering mean free path reduces drastically. The presence of
  small-scale activity also easily pulls particles from the thermal pool,
  so there is no need for a seed population. The mean square displacement
  in space and energy is superdiffusive for the high-energy particles.

Title: Superdiffusive stochastic Fermi acceleration in space and
    energy
Authors: Sioulas, N.; Isliker, H.; Vlahos, L.; Koumtzis, A.;
   Pisokas, Th
Bibcode: 2020MNRAS.491.3860S
Altcode: 2019MNRAS.tmp.2837S; 2019arXiv191107973S
  We analyse the transport properties of charged particles (ions
  and electrons) interacting with randomly formed magnetic scatterers
  (e.g. large-scale local 'magnetic fluctuations' or 'coherent magnetic
  irregularities' usually present in strongly turbulent plasmas), using
  the energization processes proposed initially by Fermi in 1949. The
  scatterers are formed by large-scale local fluctuations (δB/B ≈ 1)
  and are randomly distributed inside the unstable magnetic topology. We
  construct a 3D grid on which a small fraction of randomly chosen grid
  points are acting as scatterers. In particular, we study how a large
  number of test particles are accelerated and transported inside a
  collection of scatterers in a finite volume. Our main results are:
  (1) The spatial mean-square displacement &lt;(Δr)<SUP>2</SUP> &gt;
  inside the stochastic Fermi accelerator is superdiffusive, &lt; (Δ
  r)^2&gt; ∼ t^{a<SUB>r</SUB>}, with a<SUB>r</SUB> ∼ 1.2-1.6, for
  the high-energy electrons with kinetic energy (W) larger than 1 MeV,
  and it is normal (a<SUB>r</SUB> = 1) for the heated low-energy (W &lt;
  10 keV) electrons. (2) The transport properties of the high-energy
  particles are closely related with the mean-free path that the
  particles travel in-between the scatterers (λ<SUB>sc</SUB>). The
  smaller λ<SUB>sc</SUB> is, the faster the electrons and ions escape
  from the acceleration volume. (3) The mean displacement in energy
  &lt; Δ W&gt; ∼ t^{a<SUB>W</SUB>} is strongly enhanced inside the
  acceleration volume (a<SUB>W</SUB> = 1.5-2.5) for the high-energy
  particles compared to the thermal low-energy particles (a<SUB>W</SUB>
  = 0.4), I.e. high-energy particles undergo an enhanced systematic gain
  in energy. (4) The mean-square displacement in energy &lt;W<SUP>2</SUP>
  &gt; is superdiffusive for the high-energy particles and normal for
  the low-energy, heated particles.

Title: Particle Acceleration and Heating in Regions of Magnetic
    Flux Emergence
Authors: Isliker, H.; Archontis, V.; Vlahos, L.
Bibcode: 2019ApJ...882...57I
Altcode: 2019arXiv190704296I
  The interaction between emerging and pre-existing magnetic fields
  in the solar atmosphere can trigger several dynamic phenomena, such
  as eruptions and jets. A key element during this interaction is
  the formation of large-scale current sheets, and eventually their
  fragmentation that leads to the creation of a strongly turbulent
  environment. In this paper, we study the kinetic aspects of the
  interaction (reconnection) between emerging and ambient magnetic
  fields. We show that the statistical properties of the spontaneously
  fragmented and fractal electric fields are responsible for the
  efficient heating and acceleration of charged particles, which form a
  power-law tail at high energies on sub-second timescales. A fraction
  of the energized particles escapes from the acceleration volume, with
  a super-hot component with a temperature close to 150 MK, and with a
  power-law high-energy tail with an index between -2 and -3. We estimate
  the transport coefficients in energy space from the dynamics of the
  charged particles inside the fragmented and fractal electric fields, and
  the solution of a fractional transport equation, as appropriate for a
  strongly turbulent plasma, agrees with the test-particle simulations. We
  also show that the acceleration mechanism is not related to Fermi
  acceleration, and the Fokker-Planck equation is inconsistent and
  not adequate as a transport model. Finally, we address the problem
  of correlations between spatial transport and transport in energy
  space. Our results confirm the observations reported for high-energy
  particles (hard X-rays, type III bursts, and solar energetic particles)
  during the emission of solar jets.

Title: Introduction to the physics of solar eruptions and their
    space weather impact
Authors: Archontis, Vasilis; Vlahos, Loukas
Bibcode: 2019RSPTA.37790152A
Altcode: 2019arXiv190508361A
  The physical processes, which drive powerful solar eruptions, play an
  important role in our understanding of the Sun-Earth connection. In this
  Special Issue, we firstly discuss how magnetic fields emerge from the
  solar interior to the solar surface, to build up active regions, which
  commonly host large-scale coronal disturbances, such as coronal mass
  ejections (CMEs). Then, we discuss the physical processes associated
  with the driving and triggering of these eruptions, the propagation
  of the large-scale magnetic disturbances through interplanetary
  space and the interaction of CMEs with Earth's magnetic field. The
  acceleration mechanisms for the solar energetic particles related to
  explosive phenomena (e.g. flares and/or CMEs) in the solar corona
  are also discussed. The main aim of this Issue, therefore, is to
  encapsulate the present state-of-the-art in research related to the
  genesis of solar eruptions and their space-weather implications. <P
  />This article is part of the theme issue `Solar eruptions and their
  space weather impact'.

Title: Sources of solar energetic particles
Authors: Vlahos, Loukas; Anastasiadis, Anastasios; Papaioannou,
   Athanasios; Kouloumvakos, Athanasios; Isliker, Heinz
Bibcode: 2019RSPTA.37780095V
Altcode: 2019arXiv190308200V
  Solar energetic particles are an integral part of the physical processes
  related with space weather. We present a review for the acceleration
  mechanisms related to the explosive phenomena (flares and/or coronal
  mass ejections, CMEs) inside the solar corona. For more than 40 years,
  the main two-dimensional cartoon representing our understanding
  of the explosive phenomena inside the solar corona remained almost
  unchanged. The acceleration mechanisms related to solar flares and
  CMEs also remained unchanged and were part of the same cartoon. In this
  review, we revise the standard cartoon and present evidence from recent
  global magnetohydrodynamic simulations that support the argument that
  explosive phenomena will lead to the spontaneous formation of current
  sheets in different parts of the erupting magnetic structure. The
  evolution of the large-scale current sheets and their fragmentation
  will lead to strong turbulence and turbulent reconnection during solar
  flares and turbulent shocks. In other words, the acceleration mechanism
  in flares and CME-driven shocks may be the same, and their difference
  will be the overall magnetic topology, the ambient plasma parameters,
  and the duration of the unstable driver. <P />This article is part of
  the theme issue `Solar eruptions and their space weather impact'.

Title: Particle acceleration and heating in a turbulent solar corona
Authors: Vlahos, Loukas; Isliker, Heinz
Bibcode: 2019PPCF...61a4020V
Altcode: 2018arXiv180807136V
  Turbulence, magnetic reconnection, and shocks can be present
  in explosively unstable plasmas, forming a new electromagnetic
  environment, which we call here turbulent reconnection, and where
  spontaneous formation of current sheets takes place. We will show
  that the heating and the acceleration of particles is the result of
  the synergy of stochastic (second order Fermi) and systematic (first
  order Fermi) acceleration inside fully developed turbulence. The
  solar atmosphere is magnetically coupled to a turbulent driver (the
  convection zone), therefore the appearance of turbulent reconnection
  in the solar atmosphere is externally driven. Turbulent reconnection,
  once it is established in the solar corona, drives the coronal heating
  and particle acceleration.

Title: Statistical Analysis of Individual Solar Active Regions
Authors: Kromyda, Garyfallia; Vlahos, Loukas
Bibcode: 2018IAUS..335....3K
Altcode:
  In the last decades, numerous observational and computational studies
  have shown that the global flare distribution is a power-law with
  a slope less than 2. In these studies, active regions are treated
  as statistically indistinguishable. To test this, we identify and
  separately analyze the flares produced by ten individual active
  regions (2006-2016). In five regions, we find a single power-law
  distribution, with a slope of a &lt; 2. In the other five, we find a
  broken double power-law distribution, with slopes a<SUB>1</SUB> &lt;
  2 and a<SUB>2</SUB> &gt; 2.

Title: Diffusive shock acceleration and turbulent reconnection
Authors: Garrel, Christian; Vlahos, Loukas; Isliker, Heinz; Pisokas,
   Theophilos
Bibcode: 2018MNRAS.478.2976G
Altcode: 2018arXiv180505143G; 2018MNRAS.tmp.1205G
  Diffusive shock acceleration (DSA) cannot efficiently accelerate
  particles without the presence of self-consistently generated or
  pre-existing strong turbulence (δB/B∼ 1) in the vicinity of the
  shock. The problem we address in this article is: if large-amplitude
  magnetic disturbances are present upstream and downstream of a shock
  then Turbulent Reconnection (TR) will set in and will participate
  not only in the elastic scattering of particles but also in their
  heating and acceleration. We demonstrate that large-amplitude magnetic
  disturbances and Unstable Current Sheets (UCS), spontaneously formed
  in the strong turbulence in the vicinity of a shock, can accelerate
  particles as efficiently as DSA in large-scale systems and on long
  time scales. We start our analysis with `elastic' scatterers upstream
  and downstream and estimate the energy distribution of particles
  escaping from the shock, recovering the well-known results from the DSA
  theory. Next we analyse the additional interaction of the particles
  with active scatterers (magnetic disturbances and UCS) upstream and
  downstream of the shock. We show that the asymptotic energy distribution
  of the particles accelerated by DSA/TR has very similar characteristics
  with the one due to DSA alone, but the synergy of DSA with TR is much
  more efficient: The acceleration time is an order of magnitude shorter
  and the maximum energy reached two orders of magnitude higher. We claim
  that DSA is the dominant acceleration mechanism in a short period before
  TR is established, and then strong turbulence will dominate the heating
  and acceleration of the particles. In other words, the shock serves
  as the mechanism to set up a strongly turbulent environment, in which
  the acceleration mechanism will ultimately be the synergy of DSA and TR.

Title: Synergy of Stochastic and Systematic Energization of Plasmas
    during Turbulent Reconnection
Authors: Pisokas, Theophilos; Vlahos, Loukas; Isliker, Heinz
Bibcode: 2018ApJ...852...64P
Altcode: 2017arXiv171203517P
  The important characteristic of turbulent reconnection is that it
  combines large-scale magnetic disturbances (δ B/B∼ 1) with randomly
  distributed unstable current sheets (UCSs). Many well-known nonlinear
  MHD structures (strong turbulence, current sheet(s), shock(s)) lead
  asymptotically to the state of turbulent reconnection. We analyze
  in this article, for the first time, the energization of electrons
  and ions in a large-scale environment that combines large-amplitude
  disturbances propagating with sub-Alfvénic speed with UCSs. The
  magnetic disturbances interact stochastically (second-order Fermi) with
  the charged particles and play a crucial role in the heating of the
  particles, while the UCSs interact systematically (first-order Fermi)
  and play a crucial role in the formation of the high-energy tail. The
  synergy of stochastic and systematic acceleration provided by the
  mixture of magnetic disturbances and UCSs influences the energetics
  of the thermal and nonthermal particles, the power-law index, and
  the length of time the particles remain inside the energy release
  volume. We show that this synergy can explain the observed very fast
  and impulsive particle acceleration and the slightly delayed formation
  of a superhot particle population.

Title: Particle Acceleration and Fractional Transport in Turbulent
    Reconnection
Authors: Isliker, Heinz; Pisokas, Theophilos; Vlahos, Loukas;
   Anastasiadis, Anastasios
Bibcode: 2017ApJ...849...35I
Altcode: 2017arXiv170908269I
  We consider a large-scale environment of turbulent reconnection
  that is fragmented into a number of randomly distributed unstable
  current sheets (UCSs), and we statistically analyze the acceleration
  of particles within this environment. We address two important cases
  of acceleration mechanisms when particles interact with the UCS:
  (a) electric field acceleration and (b) acceleration by reflection
  at contracting islands. Electrons and ions are accelerated very
  efficiently, attaining an energy distribution of power-law shape with
  an index 1-2, depending on the acceleration mechanism. The transport
  coefficients in energy space are estimated from test-particle simulation
  data, and we show that the classical Fokker-Planck (FP) equation fails
  to reproduce the simulation results when the transport coefficients
  are inserted into it and it is solved numerically. The cause for this
  failure is that the particles perform Levy flights in energy space,
  while the distributions of the energy increments exhibit power-law
  tails. We then use the fractional transport equation (FTE) derived
  by Isliker et al., whose parameters and the order of the fractional
  derivatives are inferred from the simulation data, and solving the FTE
  numerically, we show that the FTE successfully reproduces the kinetic
  energy distribution of the test particles. We discuss in detail the
  analysis of the simulation data and the criteria that allow one to
  judge the appropriateness of either an FTE or a classical FP equation
  as a transport model.

Title: Stochastic Fermi Energization of Coronal Plasma during
    Explosive Magnetic Energy Release
Authors: Pisokas, Theophilos; Vlahos, Loukas; Isliker, Heinz; Tsiolis,
   Vassilis; Anastasiadis, Anastasios
Bibcode: 2017ApJ...835..214P
Altcode: 2016arXiv161204246P
  The aim of this study is to analyze the interaction of charged particles
  (ions and electrons) with randomly formed particle scatterers (e.g.,
  large-scale local “magnetic fluctuations” or “coherent magnetic
  irregularities”) using the setup proposed initially by Fermi. These
  scatterers are formed by the explosive magnetic energy release
  and propagate with the Alfvén speed along the irregular magnetic
  fields. They are large-scale local fluctuations (δB/B ≈ 1) randomly
  distributed inside the unstable magnetic topology and will here be
  called Alfvénic Scatterers (AS). We constructed a 3D grid on which
  a small fraction of randomly chosen grid points are acting as AS. In
  particular, we study how a large number of test particles evolves inside
  a collection of AS, analyzing the evolution of their energy distribution
  and their escape-time distribution. We use a well-established method to
  estimate the transport coefficients directly from the trajectories of
  the particles. Using the estimated transport coefficients and solving
  the Fokker-Planck equation numerically, we can recover the energy
  distribution of the particles. We have shown that the stochastic Fermi
  energization of mildly relativistic and relativistic plasma can heat and
  accelerate the tail of the ambient particle distribution as predicted
  by Parker &amp; Tidman and Ramaty. The temperature of the hot plasma
  and the tail of the energetic particles depend on the mean free path
  (λ<SUB>sc</SUB>) of the particles between the scatterers inside the
  energization volume.

Title: Limits of applicability of the quasilinear approximation to
    the electrostatic wave-plasma interaction
Authors: Zacharegkas, Georgios; Isliker, Heinz; Vlahos, Loukas
Bibcode: 2016PhPl...23k2119Z
Altcode: 2016arXiv161103792Z
  The limitation of the Quasilinear Theory (QLT) to describe the diffusion
  of electrons and ions in velocity space when interacting with a spectrum
  of large amplitude electrostatic Langmuir, Upper and Lower hybrid waves,
  is analyzed. We analytically and numerically estimate the threshold
  for the amplitude of the waves above which the QLT breaks down, using
  a test particle code. The evolution of the velocity distribution,
  the velocity-space diffusion coefficients, the driven current, and
  the heating of the particles are investigated, for the interaction
  with small and large amplitude electrostatic waves, that is, in both
  regimes, where QLT is valid and where it clearly breaks down.

Title: An observationally-driven kinetic approach to coronal heating
Authors: Moraitis, K.; Toutountzi, A.; Isliker, H.; Georgoulis, M.;
   Vlahos, L.; Chintzoglou, G.
Bibcode: 2016A&A...596A..56M
Altcode: 2016arXiv160307129M; 2016arXiv160307129T
  <BR /> Aims: Coronal heating through the explosive release of magnetic
  energy remains an open problem in solar physics. Recent hydrodynamical
  models attempt an investigation by placing swarms of "nanoflares" at
  random sites and times in modeled one-dimensional coronal loops. We
  investigate the problem in three dimensions, using extrapolated coronal
  magnetic fields of observed solar active regions. <BR /> Methods: We
  applied a nonlinear force-free field extrapolation above an observed
  photospheric magnetogram of NOAA active region (AR) 11 158. We then
  determined the locations, energy contents, and volumes of "unstable"
  areas, namely areas prone to releasing magnetic energy due to locally
  accumulated electric current density. Statistical distributions of
  these volumes and their fractal dimension are inferred, investigating
  also their dependence on spatial resolution. Further adopting a
  simple resistivity model, we inferred the properties of the fractally
  distributed electric fields in these volumes. Next, we monitored the
  evolution of 10<SUP>5</SUP> particles (electrons and ions) obeying
  an initial Maxwellian distribution with a temperature of 10 eV,
  by following their trajectories and energization when subjected
  to the resulting electric fields. For computational convenience,
  the length element of the magnetic-field extrapolation is 1 arcsec,
  or 725 km, much coarser than the particles' collisional mean free
  path in the low corona (0.1-1 km). <BR /> Results: The presence of
  collisions traps the bulk of the plasma around the unstable volumes,
  or current sheets (UCS), with only a tail of the distribution gaining
  substantial energy. Assuming that the distance between UCS is similar
  to the collisional mean free path we find that the low active-region
  corona is heated to 100-200 eV, corresponding to temperatures exceeding
  2 MK, within tens of seconds for electrons and thousands of seconds for
  ions. <BR /> Conclusions: Fractally distributed, nanoflare-triggening
  fragmented UCS in the active-region corona can heat electrons and ions
  with minor enhancements of the local resistivity. This statistical
  result is independent from the nature of the extrapolation and the
  spatial resolution of the modeled active-region corona. This finding
  should be coupled with a complete plasma treatment to determine whether
  a quasi-steady temperature similar to that of the ambient corona can be
  maintained, either via a kinetic or via a hybrid, kinetic and fluid,
  plasma treatment. The finding can also be extended to the quiet solar
  corona, provided that the currently undetected nanoflares are frequent
  enough to account for the lower (compared to active regions) energy
  losses in this case.

Title: Contributions of the Cherenkov Telescope Array (CTA) to
    the 6th International Symposium on High-Energy Gamma-Ray Astronomy
    (Gamma 2016)
Authors: CTA Consortium, The; :; Abchiche, A.; Abeysekara, U.; Abril,
   Ó.; Acero, F.; Acharya, B. S.; Adams, C.; Agnetta, G.; Aharonian,
   F.; Akhperjanian, A.; Albert, A.; Alcubierre, M.; Alfaro, J.; Alfaro,
   R.; Allafort, A. J.; Aloisio, R.; Amans, J. -P.; Amato, E.; Ambrogi,
   L.; Ambrosi, G.; Ambrosio, M.; Anderson, J.; Anduze, M.; Angüner,
   E. O.; Antolini, E.; Antonelli, L. A.; Antonucci, M.; Antonuccio,
   V.; Antoranz, P.; Aramo, C.; Aravantinos, A.; Araya, M.; Arcaro, C.;
   Arezki, B.; Argan, A.; Armstrong, T.; Arqueros, F.; Arrabito, L.;
   Arrieta, M.; Asano, K.; Ashley, M.; Aubert, P.; Singh, C. B.; Babic,
   A.; Backes, M.; Bais, A.; Bajtlik, S.; Balazs, C.; Balbo, M.; Balis,
   D.; Balkowski, C.; Ballester, O.; Ballet, J.; Balzer, A.; Bamba,
   A.; Bandiera, R.; Barber, A.; Barbier, C.; Barcelo, M.; Barkov,
   M.; Barnacka, A.; Barres de Almeida, U.; Barrio, J. A.; Basso, S.;
   Bastieri, D.; Bauer, C.; Becciani, U.; Becherini, Y.; Becker Tjus,
   J.; Beckmann, V.; Bednarek, W.; Benbow, W.; Benedico Ventura, D.;
   Berdugo, J.; Berge, D.; Bernardini, E.; Bernardini, M. G.; Bernhard,
   S.; Bernlöhr, K.; Bertucci, B.; Besel, M. -A.; Beshley, V.; Bhatt,
   N.; Bhattacharjee, P.; Bhattacharyya, W.; Bhattachryya, S.; Biasuzzi,
   B.; Bicknell, G.; Bigongiari, C.; Biland, A.; Bilinsky, A.; Bilnik,
   W.; Biondo, B.; Bird, R.; Bird, T.; Bissaldi, E.; Bitossi, M.;
   Blanch, O.; Blasi, P.; Blazek, J.; Bockermann, C.; Boehm, C.; Bogacz,
   L.; Bogdan, M.; Bohacova, M.; Boisson, C.; Boix, J.; Bolmont, J.;
   Bonanno, G.; Bonardi, A.; Bonavolontà, C.; Bonifacio, P.; Bonnarel,
   F.; Bonnoli, G.; Borkowski, J.; Bose, R.; Bosnjak, Z.; Böttcher, M.;
   Bousquet, J. -J.; Boutonnet, C.; Bouyjou, F.; Bowman, L.; Braiding,
   C.; Brantseg, T.; Brau-Nogué, S.; Bregeon, J.; Briggs, M.; Brigida,
   M.; Bringmann, T.; Brisken, W.; Bristow, D.; Britto, R.; Brocato, E.;
   Bron, S.; Brook, P.; Brooks, W.; Brown, A. M.; Brügge, K.; Brun, F.;
   Brun, P.; Brun, P.; Brunetti, G.; Brunetti, L.; Bruno, P.; Buanes,
   T.; Bucciantini, N.; Buchholtz, G.; Buckley, J.; Bugaev, V.; Bühler,
   R.; Bulgarelli, A.; Bulik, T.; Burton, M.; Burtovoi, A.; Busetto,
   G.; Buson, S.; Buss, J.; Byrum, K.; Cadoux, F.; Calvo Tovar, J.;
   Cameron, R.; Canelli, F.; Canestrari, R.; Capalbi, M.; Capasso, M.;
   Capobianco, G.; Caproni, A.; Caraveo, P.; Cardenzana, J.; Cardillo,
   M.; Carius, S.; Carlile, C.; Carosi, A.; Carosi, R.; Carquín, E.;
   Carr, J.; Carroll, M.; Carter, J.; Carton, P. -H.; Casandjian, J. -M.;
   Casanova, S.; Casanova, S.; Cascone, E.; Casiraghi, M.; Castellina,
   A.; Castroviejo Mora, J.; Catalani, F.; Catalano, O.; Catalanotti,
   S.; Cauz, D.; Cavazzani, S.; Cerchiara, P.; Chabanne, E.; Chadwick,
   P.; Chaleil, T.; Champion, C.; Chatterjee, A.; Chaty, S.; Chaves, R.;
   Chen, A.; Chen, X.; Chen, X.; Cheng, K.; Chernyakova, M.; Chiappetti,
   L.; Chikawa, M.; Chinn, D.; Chitnis, V. R.; Cho, N.; Christov, A.;
   Chudoba, J.; Cieślar, M.; Ciocci, M. A.; Clay, R.; Colafrancesco,
   S.; Colin, P.; Colley, J. -M.; Colombo, E.; Colome, J.; Colonges, S.;
   Conforti, V.; Connaughton, V.; Connell, S.; Conrad, J.; Contreras,
   J. L.; Coppi, P.; Corbel, S.; Coridian, J.; Cornat, R.; Corona,
   P.; Corti, D.; Cortina, J.; Cossio, L.; Costa, A.; Costantini, H.;
   Cotter, G.; Courty, B.; Covino, S.; Covone, G.; Crimi, G.; Criswell,
   S. J.; Crocker, R.; Croston, J.; Cuadra, J.; Cumani, P.; Cusumano,
   G.; Da Vela, P.; Dale, Ø.; D'Ammando, F.; Dang, D.; Dang, V. T.;
   Dangeon, L.; Daniel, M.; Davids, I.; Davids, I.; Dawson, B.; Dazzi,
   F.; de Aguiar Costa, B.; De Angelis, A.; de Araujo Cardoso, R. F.;
   De Caprio, V.; de Cássia dos Anjos, R.; De Cesare, G.; De Franco,
   A.; De Frondat, F.; de Gouveia Dal Pino, E. M.; de la Calle, I.;
   De Lisio, C.; de los Reyes Lopez, R.; De Lotto, B.; De Luca, A.; de
   Mello Neto, J. R. T.; de Naurois, M.; de Oña Wilhelmi, E.; De Palma,
   F.; De Persio, F.; de Souza, V.; Decock, G.; Decock, J.; Deil, C.;
   Del Santo, M.; Delagnes, E.; Deleglise, G.; Delgado, C.; Delgado, J.;
   della Volpe, D.; Deloye, P.; Detournay, M.; Dettlaff, A.; Devin, J.;
   Di Girolamo, T.; Di Giulio, C.; Di Paola, A.; Di Pierro, F.; Diaz,
   M. A.; Díaz, C.; Dib, C.; Dick, J.; Dickinson, H.; Diebold, S.;
   Digel, S.; Dipold, J.; Disset, G.; Distefano, A.; Djannati-Ataï, A.;
   Doert, M.; Dohmke, M.; Domínguez, A.; Dominik, N.; Dominique, J. -L.;
   Dominis Prester, D.; Donat, A.; Donnarumma, I.; Dorner, D.; Doro,
   M.; Dournaux, J. -L.; Downes, T.; Doyle, K.; Drake, G.; Drappeau,
   S.; Drass, H.; Dravins, D.; Drury, L.; Dubus, G.; Ducci, L.; Dumas,
   D.; Dundas Morå, K.; Durand, D.; D'Urso, D.; Dwarkadas, V.; Dyks,
   J.; Dyrda, M.; Ebr, J.; Edy, E.; Egberts, K.; Eger, P.; Egorov, A.;
   Einecke, S.; Eisch, J.; Eisenkolb, F.; Eleftheriadis, C.; Elsaesser,
   D.; Elsässer, D.; Emmanoulopoulos, D.; Engelbrecht, C.; Engelhaupt,
   D.; Ernenwein, J. -P.; Escarate, P.; Eschbach, S.; Espinoza, C.;
   Evans, P.; Fairbairn, M.; Falceta-Goncalves, D.; Falcone, A.; Fallah
   Ramazani, V.; Fantinel, D.; Farakos, K.; Farnier, C.; Farrell, E.;
   Fasola, G.; Favre, Y.; Fede, E.; Fedora, R.; Fedorova, E.; Fegan, S.;
   Ferenc, D.; Fernandez-Alonso, M.; Fernández-Barral, A.; Ferrand, G.;
   Ferreira, O.; Fesquet, M.; Fetfatzis, P.; Fiandrini, E.; Fiasson, A.;
   Filipčič, A.; Filipovic, M.; Fink, D.; Finley, C.; Finley, J. P.;
   Finoguenov, A.; Fioretti, V.; Fiorini, M.; Fleischhack, H.; Flores,
   H.; Florin, D.; Föhr, C.; Fokitis, E.; Fonseca, M. V.; Font, L.;
   Fontaine, G.; Fontes, B.; Fornasa, M.; Fornasa, M.; Förster, A.;
   Fortin, P.; Fortson, L.; Fouque, N.; Franckowiak, A.; Franckowiak,
   A.; Franco, F. J.; Freire Mota Albuquerque, I.; Freixas Coromina,
   L.; Fresnillo, L.; Fruck, C.; Fuessling, M.; Fugazza, D.; Fujita, Y.;
   Fukami, S.; Fukazawa, Y.; Fukuda, T.; Fukui, Y.; Funk, S.; Furniss, A.;
   Gäbele, W.; Gabici, S.; Gadola, A.; Galindo, D.; Gall, D. D.; Gallant,
   Y.; Galloway, D.; Gallozzi, S.; Galvez, J. A.; Gao, S.; Garcia, A.;
   Garcia, B.; García Gil, R.; Garcia López, R.; Garczarczyk, M.;
   Gardiol, D.; Gargano, C.; Gargano, F.; Garozzo, S.; Garrecht, F.;
   Garrido, L.; Garrido-Ruiz, M.; Gascon, D.; Gaskins, J.; Gaudemard,
   J.; Gaug, M.; Gaweda, J.; Gebhardt, B.; Gebyehu, M.; Geffroy, N.;
   Genolini, B.; Gerard, L.; Ghalumyan, A.; Ghedina, A.; Ghislain, P.;
   Giammaria, P.; Giannakaki, E.; Gianotti, F.; Giarrusso, S.; Giavitto,
   G.; Giebels, B.; Gieras, T.; Giglietto, N.; Gika, V.; Gimenes, R.;
   Giomi, M.; Giommi, P.; Giordano, F.; Giovannini, G.; Girardot, P.;
   Giro, E.; Giroletti, M.; Gironnet, J.; Giuliani, A.; Glicenstein,
   J. -F.; Gnatyk, R.; Godinovic, N.; Goldoni, P.; Gomez, G.; Gonzalez,
   M. M.; González, A.; Gora, D.; Gothe, K. S.; Gotz, D.; Goullon, J.;
   Grabarczyk, T.; Graciani, R.; Graham, J.; Grandi, P.; Granot, J.;
   Grasseau, G.; Gredig, R.; Green, A. J.; Green, A. M.; Greenshaw, T.;
   Grenier, I.; Griffiths, S.; Grillo, A.; Grondin, M. -H.; Grube, J.;
   Grudzinska, M.; Grygorczuk, J.; Guarino, V.; Guberman, D.; Gunji, S.;
   Gyuk, G.; Hadasch, D.; Hagedorn, A.; Hagge, L.; Hahn, J.; Hakobyan,
   H.; Hara, S.; Hardcastle, M. J.; Hassan, T.; Hatanaka, K.; Haubold,
   T.; Haupt, A.; Hayakawa, T.; Hayashida, M.; Heller, M.; Heller,
   R.; Helo, J. C.; Henault, F.; Henri, G.; Hermann, G.; Hermel, R.;
   Herrera Llorente, J.; Herrera Llorente, J.; Herrero, A.; Hervet,
   O.; Hidaka, N.; Hinton, J.; Hirai, W.; Hirotani, K.; Hnatyk, B.;
   Hoang, J.; Hoffmann, D.; Hofmann, W.; Holch, T.; Holder, J.; Hooper,
   S.; Horan, D.; Hörandel, J.; Hörbe, M.; Horns, D.; Horvath, P.;
   Hose, J.; Houles, J.; Hovatta, T.; Hrabovsky, M.; Hrupec, D.; Huet,
   J. -M.; Huetten, M.; Hughes, G.; Hui, D.; Humensky, T. B.; Hussein,
   M.; Iacovacci, M.; Ibarra, A.; Ikeno, Y.; Illa, J. M.; Impiombato,
   D.; Inada, T.; Incorvaia, S.; Infante, L.; Inome, Y.; Inoue, S.;
   Inoue, T.; Inoue, Y.; Iocco, F.; Ioka, K.; Iori, M.; Ishio, K.;
   Ishio, K.; Israel, G. L.; Iwamura, Y.; Jablonski, C.; Jacholkowska,
   A.; Jacquemier, J.; Jamrozy, M.; Janecek, P.; Janiak, M.; Jankowsky,
   D.; Jankowsky, F.; Jean, P.; Jegouzo, I.; Jenke, P.; Jimenez, J. J.;
   Jingo, M.; Jingo, M.; Jocou, L.; Jogler, T.; Johnson, C. A.; Jones,
   M.; Josselin, M.; Journet, L.; Jung, I.; Kaaret, P.; Kagaya, M.;
   Kakuwa, J.; Kalekin, O.; Kalkuhl, C.; Kamon, H.; Kankanyan, R.;
   Karastergiou, A.; Kärcher, K.; Karczewski, M.; Karkar, S.; Karn, P.;
   Kasperek, J.; Katagiri, H.; Kataoka, J.; Katarzyński, K.; Kato, S.;
   Katz, U.; Kawanaka, N.; Kaye, L.; Kazanas, D.; Kelley-Hoskins, N.;
   Kersten, J.; Khélifi, B.; Kieda, D. B.; Kihm, T.; Kimeswenger, S.;
   Kisaka, S.; Kishida, S.; Kissmann, R.; Klepser, S.; Kluźniak, W.;
   Knapen, J.; Knapp, J.; Knödlseder, J.; Koch, B.; Köck, F.; Kocot,
   J.; Kohri, K.; Kokkotas, K.; Kokkotas, K.; Kolitzus, D.; Komin, N.;
   Kominis, I.; Kong, A.; Konno, Y.; Kosack, K.; Koss, G.; Kossatz, M.;
   Kowal, G.; Koyama, S.; Kozioł, J.; Kraus, M.; Krause, J.; Krause, M.;
   Krawzcynski, H.; Krennrich, F.; Kretzschmann, A.; Kruger, P.; Kubo, H.;
   Kudryavtsev, V.; Kukec Mezek, G.; Kuklis, M.; Kuroda, H.; Kushida, J.;
   La Barbera, A.; La Palombara, N.; La Parola, V.; La Rosa, G.; Laffon,
   H.; Lahmann, R.; Lakicevic, M.; Lalik, K.; Lamanna, G.; Landriu,
   D.; Landt, H.; Lang, R. G.; Lapington, J.; Laporte, P.; Le Fèvre,
   J. -P.; Le Flour, T.; Le Sidaner, P.; Lee, S. -H.; Lee, W. H.; Lees,
   J. -P.; Lefaucheur, J.; Leffhalm, K.; Leich, H.; Leigui de Oliveira,
   M. A.; Lelas, D.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J. -P.;
   Leonard, R.; Leoni, R.; Lessio, L.; Leto, G.; Leveque, A.; Lieunard,
   B.; Limon, M.; Lindemann, R.; Lindfors, E.; Linhoff, L.; Liolios,
   A.; Lipniacka, A.; Lockart, H.; Lohse, T.; Łokas, E.; Lombardi, S.;
   Longo, F.; Lopatin, A.; Lopez, M.; Loreggia, D.; Louge, T.; Louis,
   F.; Louys, M.; Lucarelli, F.; Lucchesi, D.; Lüdecke, H.; Luigi, T.;
   Luque-Escamilla, P. L.; Lyard, E.; Maccarone, M. C.; Maccarone, T.;
   Maccarone, T. J.; Mach, E.; Madejski, G. M.; Madonna, A.; Magniette,
   F.; Magniez, A.; Mahabir, M.; Maier, G.; Majumdar, P.; Majumdar, P.;
   Makariev, M.; Malaguti, G.; Malaspina, G.; Mallot, A. K.; Malouf,
   A.; Maltezos, S.; Malyshev, D.; Mancilla, A.; Mandat, D.; Maneva, G.;
   Manganaro, M.; Mangano, S.; Manigot, P.; Mankushiyil, N.; Mannheim, K.;
   Maragos, N.; Marano, D.; Marchegiani, P.; Marcomini, J. A.; Marcowith,
   A.; Mariotti, M.; Marisaldi, M.; Markoff, S.; Martens, C.; Martí,
   J.; Martin, J. -M.; Martin, L.; Martin, P.; Martínez, G.; Martínez,
   M.; Martínez, O.; Martynyuk-Lototskyy, K.; Marx, R.; Masetti, N.;
   Massimino, P.; Mastichiadis, A.; Mastroianni, S.; Mastropietro, M.;
   Masuda, S.; Matsumoto, H.; Matsuoka, S.; Matthews, N.; Mattiazzo, S.;
   Maurin, G.; Maxted, N.; Maxted, N.; Maya, J.; Mayer, M.; Mazin, D.;
   Mazziotta, M. N.; Mc Comb, L.; McCubbin, N.; McHardy, I.; Medina,
   C.; Mehrez, F.; Melioli, C.; Melkumyan, D.; Melse, T.; Mereghetti,
   S.; Merk, M.; Mertsch, P.; Meunier, J. -L.; Meures, T.; Meyer, M.;
   Meyrelles, J. L., jr; Miccichè, A.; Michael, T.; Michałowski, J.;
   Mientjes, P.; Mievre, I.; Mihailidis, A.; Miller, J.; Mineo, T.;
   Minuti, M.; Mirabal, N.; Mirabel, F.; Miranda, J. M.; Mirzoyan, R.;
   Mitchell, A.; Mizuno, T.; Moderski, R.; Mognet, I.; Mohammed, M.;
   Moharana, R.; Mohrmann, L.; Molinari, E.; Molyneux, P.; Monmarthe,
   E.; Monnier, G.; Montaruli, T.; Monte, C.; Monteiro, I.; Mooney, D.;
   Moore, P.; Moralejo, A.; Morello, C.; Moretti, E.; Mori, K.; Morris,
   P.; Morselli, A.; Moscato, F.; Motohashi, D.; Mottez, F.; Moudden,
   Y.; Moulin, E.; Mueller, S.; Mukherjee, R.; Munar, P.; Munari, M.;
   Mundell, C.; Mundet, J.; Muraishi, H.; Murase, K.; Muronga, A.; Murphy,
   A.; Nagar, N.; Nagataki, S.; Nagayoshi, T.; Nagesh, B. K.; Naito,
   T.; Nakajima, D.; Nakajima, D.; Nakamori, T.; Nakayama, K.; Nanni,
   J.; Naumann, D.; Nayman, P.; Nellen, L.; Nemmen, R.; Neronov, A.;
   Neyroud, N.; Nguyen, T.; Nguyen, T. T.; Nguyen Trung, T.; Nicastro, L.;
   Nicolau-Kukliński, J.; Niederwanger, F.; Niedźwiecki, A.; Niemiec,
   J.; Nieto, D.; Nievas-Rosillo, M.; Nikolaidis, A.; Nikołajuk, M.;
   Nishijima, K.; Nishikawa, K. -I.; Nishiyama, G.; Noda, K.; Noda,
   K.; Nogues, L.; Nolan, S.; Northrop, R.; Nosek, D.; Nöthe, M.;
   Novosyadlyj, B.; Nozka, L.; Nunio, F.; Oakes, L.; O'Brien, P.; Ocampo,
   C.; Occhipinti, G.; Ochoa, J. P.; OFaolain de Bhroithe, A.; Oger, R.;
   Ohira, Y.; Ohishi, M.; Ohm, S.; Ohoka, H.; Okazaki, N.; Okumura, A.;
   Olive, J. -F.; Olszowski, D.; Ong, R. A.; Ono, S.; Orienti, M.; Orito,
   R.; Orlati, A.; Osborne, J.; Ostrowski, M.; Ottaway, D.; Otte, N.;
   Öttl, S.; Ovcharov, E.; Oya, I.; Ozieblo, A.; Padovani, M.; Pagano,
   I.; Paiano, S.; Paizis, A.; Palacio, J.; Palatka, M.; Pallotta, J.;
   Panagiotidis, K.; Panazol, J. -L.; Paneque, D.; Panter, M.; Panzera,
   M. R.; Paoletti, R.; Paolillo, M.; Papayannis, A.; Papyan, G.; Paravac,
   A.; Paredes, J. M.; Pareschi, G.; Park, N.; Parsons, D.; Paśko, P.;
   Pavy, S.; Pech, M.; Peck, A.; Pedaletti, G.; Pe'er, A.; Peet, S.;
   Pelat, D.; Pepato, A.; Perez, M. d. C.; Perri, L.; Perri, M.; Persic,
   M.; Persic, M.; Petrashyk, A.; Petrucci, P. -O.; Petruk, O.; Peyaud,
   B.; Pfeifer, M.; Pfeiffer, G.; Piano, G.; Pieloth, D.; Pierre, E.;
   Pinto de Pinho, F.; García, C. Pio; Piret, Y.; Pisarski, A.; Pita,
   S.; Platos, Ł.; Platzer, R.; Podkladkin, S.; Pogosyan, L.; Pohl,
   M.; Poinsignon, P.; Pollo, A.; Porcelli, A.; Porthault, J.; Potter,
   W.; Poulios, S.; Poutanen, J.; Prandini, E.; Prandini, E.; Prast, J.;
   Pressard, K.; Principe, G.; Profeti, F.; Prokhorov, D.; Prokoph, H.;
   Prouza, M.; Pruchniewicz, R.; Pruteanu, G.; Pueschel, E.; Pühlhofer,
   G.; Puljak, I.; Punch, M.; Pürckhauer, S.; Pyzioł, R.; Queiroz,
   F.; Quel, E. J.; Quinn, J.; Quirrenbach, A.; Rafighi, I.; Rainò, S.;
   Rajda, P. J.; Rameez, M.; Rando, R.; Rannot, R. C.; Rataj, M.; Ravel,
   T.; Razzaque, S.; Reardon, P.; Reichardt, I.; Reimann, O.; Reimer,
   A.; Reimer, O.; Reisenegger, A.; Renaud, M.; Renner, S.; Reposeur,
   T.; Reville, B.; Rezaeian, A.; Rhode, W.; Ribeiro, D.; Ribeiro Prado,
   R.; Ribó, M.; Richards, G.; Richer, M. G.; Richtler, T.; Rico, J.;
   Ridky, J.; Rieger, F.; Riquelme, M.; Ristori, P. R.; Rivoire, S.; Rizi,
   V.; Roache, E.; Rodriguez, J.; Rodriguez Fernandez, G.; Rodríguez
   Vázquez, J. J.; Rojas, G.; Romano, P.; Romeo, G.; Roncadelli, M.;
   Rosado, J.; Rose, J.; Rosen, S.; Rosier Lees, S.; Ross, D.; Rouaix,
   G.; Rousselle, J.; Rovero, A. C.; Rowell, G.; Roy, F.; Royer, S.;
   Rubini, A.; Rudak, B.; Rugliancich, A.; Rujopakarn, W.; Rulten,
   C.; Rupiński, M.; Russo, F.; Russo, F.; Rutkowski, K.; Saavedra,
   O.; Sabatini, S.; Sacco, B.; Sadeh, I.; Saemann, E. O.; Safi-Harb,
   S.; Saggion, A.; Sahakian, V.; Saito, T.; Sakaki, N.; Sakurai, S.;
   Salamon, A.; Salega, M.; Salek, D.; Salesa Greus, F.; Salgado, J.;
   Salina, G.; Salinas, L.; Salini, A.; Sanchez, D.; Sanchez-Conde, M.;
   Sandaker, H.; Sandoval, A.; Sangiorgi, P.; Sanguillon, M.; Sano, H.;
   Santander, M.; Santangelo, A.; Santos, E. M.; Santos-Lima, R.; Sanuy,
   A.; Sapozhnikov, L.; Sarkar, S.; Satalecka, K.; Satalecka, K.; Sato,
   Y.; Savalle, R.; Sawada, M.; Sayède, F.; Schanne, S.; Schanz, T.;
   Schioppa, E. J.; Schlenstedt, S.; Schmid, J.; Schmidt, T.; Schmoll,
   J.; Schneider, M.; Schoorlemmer, H.; Schovanek, P.; Schubert, A.;
   Schullian, E. -M.; Schultze, J.; Schulz, A.; Schulz, S.; Schure, K.;
   Schussler, F.; Schwab, T.; Schwanke, U.; Schwarz, J.; Schweizer, T.;
   Schwemmer, S.; Schwendicke, U.; Schwerdt, C.; Sciacca, E.; Scuderi,
   S.; Segreto, A.; Seiradakis, J. -H.; Sembroski, G. H.; Semikoz, D.;
   Sergijenko, O.; Serre, N.; Servillat, M.; Seweryn, K.; Shafi, N.;
   Shalchi, A.; Sharma, M.; Shayduk, M.; Shellard, R. C.; Shibata, T.;
   Shigenaka, A.; Shilon, I.; Shum, E.; Sidoli, L.; Sidz, M.; Sieiro, J.;
   Siejkowski, H.; Silk, J.; Sillanpää, A.; Simone, D.; Simpson, H.;
   Singh, B. B.; Sinha, A.; Sironi, G.; Sitarek, J.; Sizun, P.; Sliusar,
   V.; Sliusar, V.; Smith, A.; Sobczyńska, D.; Sol, H.; Sottile, G.;
   Sowiński, M.; Spanier, F.; Spengler, G.; Spiga, R.; Stadler, R.;
   Stahl, O.; Stamerra, A.; Stanič, S.; Starling, R.; Staszak, D.;
   Stawarz, Ł.; Steenkamp, R.; Stefanik, S.; Stegmann, C.; Steiner, S.;
   Stella, C.; Stephan, M.; Stergioulas, N.; Sternberger, R.; Sterzel, M.;
   Stevenson, B.; Stinzing, F.; Stodulska, M.; Stodulski, M.; Stolarczyk,
   T.; Stratta, G.; Straumann, U.; Stringhetti, L.; Strzys, M.; Stuik,
   R.; Sulanke, K. -H.; Suomijärvi, T.; Supanitsky, A. D.; Suric, T.;
   Sushch, I.; Sutcliffe, P.; Sykes, J.; Szanecki, M.; Szepieniec, T.;
   Szwarnog, P.; Tacchini, A.; Tachihara, K.; Tagliaferri, G.; Tajima,
   H.; Takahashi, H.; Takahashi, K.; Takahashi, M.; Takalo, L.; Takami,
   S.; Takata, J.; Takeda, J.; Talbot, G.; Tam, T.; Tanaka, M.; Tanaka,
   S.; Tanaka, T.; Tanaka, Y.; Tanci, C.; Tanigawa, S.; Tavani, M.;
   Tavecchio, F.; Tavernet, J. -P.; Tayabaly, K.; Taylor, A.; Tejedor,
   L. A.; Telezhinsky, I.; Temme, F.; Temnikov, P.; Tenzer, C.; Terada,
   Y.; Terrazas, J. C.; Terrier, R.; Terront, D.; Terzic, T.; Tescaro,
   D.; Teshima, M.; Teshima, M.; Testa, V.; Tezier, D.; Thayer, J.;
   Thornhill, J.; Thoudam, S.; Thuermann, D.; Tibaldo, L.; Tiengo,
   A.; Timpanaro, M. C.; Tiziani, D.; Tluczykont, M.; Todero Peixoto,
   C. J.; Tokanai, F.; Tokarz, M.; Toma, K.; Tomastik, J.; Tomono, Y.;
   Tonachini, A.; Tonev, D.; Torii, K.; Tornikoski, M.; Torres, D. F.;
   Torres, M.; Torresi, E.; Toso, G.; Tosti, G.; Totani, T.; Tothill, N.;
   Toussenel, F.; Tovmassian, G.; Toyama, T.; Travnicek, P.; Trichard,
   C.; Trifoglio, M.; Troyano Pujadas, I.; Trzeciak, M.; Tsinganos, K.;
   Tsujimoto, S.; Tsuru, T.; Uchiyama, Y.; Umana, G.; Umetsu, Y.; Upadhya,
   S. S.; Uslenghi, M.; Vagelli, V.; Vagnetti, F.; Valdes-Galicia, J.;
   Valentino, M.; Vallania, P.; Valore, L.; van Driel, W.; van Eldik,
   C.; van Soelen, B.; Vandenbroucke, J.; Vanderwalt, J.; Vasileiadis,
   G.; Vassiliev, V.; Vázquez, J. R.; Vázquez Acosta, M. L.; Vecchi,
   M.; Vega, A.; Vegas, I.; Veitch, P.; Venault, P.; Venema, L.; Venter,
   C.; Vercellone, S.; Vergani, S.; Verma, K.; Verzi, V.; Vettolani,
   G. P.; Veyssiere, C.; Viana, A.; Viaux, N.; Vicha, J.; Vigorito,
   C.; Vincent, P.; Vincent, S.; Vink, J.; Vittorini, V.; Vlahakis, N.;
   Vlahos, L.; Voelk, H.; Voisin, V.; Vollhardt, A.; Volpicelli, A.; von
   Brand, H.; Vorobiov, S.; Vovk, I.; Vrastil, M.; Vu, L. V.; Vuillaume,
   T.; Wagner, R.; Wagner, R.; Wagner, S. J.; Wakely, S. P.; Walstra, T.;
   Walter, R.; Walther, T.; Ward, J. E.; Ward, M.; Warda, K.; Warren,
   D.; Wassberg, S.; Watson, J. J.; Wawer, P.; Wawrzaszek, R.; Webb,
   N.; Wegner, P.; Weiner, O.; Weinstein, A.; Wells, R.; Werner, F.;
   Wetteskind, H.; White, M.; White, R.; Więcek, M.; Wierzcholska, A.;
   Wiesand, S.; Wijers, R.; Wilcox, P.; Wild, N.; Wilhelm, A.; Wilkinson,
   M.; Will, M.; Will, M.; Williams, D. A.; Williams, J. T.; Willingale,
   R.; Wilson, N.; Winde, M.; Winiarski, K.; Winkler, H.; Winter, M.;
   Wischnewski, R.; Witt, E.; Wojcik, P.; Wolf, D.; Wood, M.; Wörnlein,
   A.; Wu, E.; Wu, T.; Yadav, K. K.; Yamamoto, H.; Yamamoto, T.; Yamane,
   N.; Yamazaki, R.; Yanagita, S.; Yang, L.; Yelos, D.; Yoshida, A.;
   Yoshida, M.; Yoshida, T.; Yoshiike, S.; Yoshikoshi, T.; Yu, P.;
   Zabalza, V.; Zaborov, D.; Zacharias, M.; Zaharijas, G.; Zajczyk,
   A.; Zampieri, L.; Zandanel, F.; Zanmar Sanchez, R.; Zaric, D.;
   Zavrtanik, D.; Zavrtanik, M.; Zdziarski, A.; Zech, A.; Zechlin, H.;
   Zhao, A.; Zhdanov, V.; Ziegler, A.; Ziemann, J.; Ziętara, K.; Zink,
   A.; Ziółkowski, J.; Zitelli, V.; Zoli, A.; Zorn, J.; Żychowski, P.
Bibcode: 2016arXiv161005151C
Altcode:
  List of contributions from the Cherenkov Telescope Array (CTA)
  Consortium presented at the 6th International Symposium on High-Energy
  Gamma-Ray Astronomy (Gamma 2016), July 11-15, 2016, in Heidelberg,
  Germany.

Title: Complexity methods applied to turbulence in plasma astrophysics
Authors: Vlahos, L.; Isliker, H.
Bibcode: 2016EPJST.225..977V
Altcode: 2016arXiv160300394V
  In this review many of the well known tools for the analysis of
  Complex systems are used in order to study the global coupling of the
  turbulent convection zone with the solar atmosphere where the magnetic
  energy is dissipated explosively. Several well documented observations
  are not easy to interpret with the use of Magnetohydrodynamic (MHD)
  and/or Kinetic numerical codes. Such observations are: (1) The size
  distribution of the Active Regions (AR) on the solar surface, (2) The
  fractal and multi fractal characteristics of the observed magnetograms,
  (3) The Self-Organised characteristics of the explosive magnetic
  energy release and (4) the very efficient acceleration of particles
  during the flaring periods in the solar corona. We review briefly
  the work published the last twenty five years on the above issues
  and propose solutions by using methods borrowed from the analysis
  of complex systems. The scenario which emerged is as follows: (a)
  The fully developed turbulence in the convection zone generates and
  transports magnetic flux tubes to the solar surface. Using probabilistic
  percolation models we were able to reproduce the size distribution and
  the fractal properties of the emerged and randomly moving magnetic flux
  tubes. (b) Using a Non Linear Force Free (NLFF) magnetic extrapolation
  numerical code we can explore how the emerged magnetic flux tubes
  interact nonlinearly and form thin and Unstable Current Sheets (UCS)
  inside the coronal part of the AR. (c) The fragmentation of the UCS
  and the redistribution of the magnetic field locally, when the local
  current exceeds a Critical threshold, is a key process which drives
  avalanches and forms coherent structures. This local reorganization of
  the magnetic field enhances the energy dissipation and influences the
  global evolution of the complex magnetic topology. Using a Cellular
  Automaton and following the simple rules of Self Organized Criticality
  (SOC), we were able to reproduce the statistical characteristics of
  the observed time series of the explosive events, (d) finally, when
  the AR reaches the turbulently reconnecting state (in the language of
  the SOC theory this is called SOC state) it is densely populated by UCS
  which can act as local scatterers (replacing the magnetic clouds in the
  Fermi scenario) and enhance dramatically the heating and acceleration
  of charged particles.

Title: Particle Acceleration and Heating by Turbulent Reconnection
Authors: Vlahos, Loukas; Pisokas, Theophilos; Isliker, Heinz; Tsiolis,
   Vassilis; Anastasiadis, Anastasios
Bibcode: 2016ApJ...827L...3V
Altcode: 2016arXiv160405234V
  Turbulent flows in the solar wind, large-scale current sheets, multiple
  current sheets, and shock waves lead to the formation of environments
  in which a dense network of current sheets is established and sustains
  “turbulent reconnection.” We constructed a 2D grid on which a number
  of randomly chosen grid points are acting as scatterers (I.e., magnetic
  clouds or current sheets). Our goal is to examine how test particles
  respond inside this large-scale collection of scatterers. We study
  the energy gain of individual particles, the evolution of their energy
  distribution, and their escape time distribution. We have developed a
  new method to estimate the transport coefficients from the dynamics
  of the interaction of the particles with the scatterers. Replacing
  the “magnetic clouds” with current sheets, we have proven that the
  energization processes can be more efficient depending on the strength
  of the effective electric fields inside the current sheets and their
  statistical properties. Using the estimated transport coefficients
  and solving the Fokker-Planck (FP) equation, we can recover the energy
  distribution of the particles only for the stochastic Fermi process. We
  have shown that the evolution of the particles inside a turbulent
  reconnecting volume is not a solution of the FP equation, since the
  interaction of the particles with the current sheets is “anomalous,”
  in contrast to the case of the second-order Fermi process.

Title: The Major Geoeffective Solar Eruptions of 2012 March 7:
    Comprehensive Sun-to-Earth Analysis
Authors: Patsourakos, S.; Georgoulis, M. K.; Vourlidas, A.; Nindos,
   A.; Sarris, T.; Anagnostopoulos, G.; Anastasiadis, A.; Chintzoglou,
   G.; Daglis, I. A.; Gontikakis, C.; Hatzigeorgiu, N.; Iliopoulos, A. C.;
   Katsavrias, C.; Kouloumvakos, A.; Moraitis, K.; Nieves-Chinchilla, T.;
   Pavlos, G.; Sarafopoulos, D.; Syntelis, P.; Tsironis, C.; Tziotziou,
   K.; Vogiatzis, I. I.; Balasis, G.; Georgiou, M.; Karakatsanis, L. P.;
   Malandraki, O. E.; Papadimitriou, C.; Odstrčil, D.; Pavlos, E. G.;
   Podlachikova, O.; Sandberg, I.; Turner, D. L.; Xenakis, M. N.; Sarris,
   E.; Tsinganos, K.; Vlahos, L.
Bibcode: 2016ApJ...817...14P
Altcode:
  During the interval 2012 March 7-11 the geospace experienced a
  barrage of intense space weather phenomena including the second
  largest geomagnetic storm of solar cycle 24 so far. Significant
  ultra-low-frequency wave enhancements and relativistic-electron dropouts
  in the radiation belts, as well as strong energetic-electron injection
  events in the magnetosphere were observed. These phenomena were
  ultimately associated with two ultra-fast (&gt;2000 km s<SUP>-1</SUP>)
  coronal mass ejections (CMEs), linked to two X-class flares launched
  on early 2012 March 7. Given that both powerful events originated from
  solar active region NOAA 11429 and their onsets were separated by less
  than an hour, the analysis of the two events and the determination
  of solar causes and geospace effects are rather challenging. Using
  satellite data from a flotilla of solar, heliospheric and magnetospheric
  missions a synergistic Sun-to-Earth study of diverse observational
  solar, interplanetary and magnetospheric data sets was performed. It was
  found that only the second CME was Earth-directed. Using a novel method,
  we estimated its near-Sun magnetic field at 13 R<SUB>⊙</SUB> to be
  in the range [0.01, 0.16] G. Steep radial fall-offs of the near-Sun
  CME magnetic field are required to match the magnetic fields of the
  corresponding interplanetary CME (ICME) at 1 AU. Perturbed upstream
  solar-wind conditions, as resulting from the shock associated with the
  Earth-directed CME, offer a decent description of its kinematics. The
  magnetospheric compression caused by the arrival at 1 AU of the shock
  associated with the ICME was a key factor for radiation-belt dynamics.

Title: CTA Contributions to the 34th International Cosmic Ray
    Conference (ICRC2015)
Authors: CTA Consortium, The; :; Abchiche, A.; Abeysekara, U.; Abril,
   Ó.; Acero, F.; Acharya, B. S.; Actis, M.; Agnetta, G.; Aguilar,
   J. A.; Aharonian, F.; Akhperjanian, A.; Albert, A.; Alcubierre,
   M.; Alfaro, R.; Aliu, E.; Allafort, A. J.; Allan, D.; Allekotte,
   I.; Aloisio, R.; Amans, J. -P.; Amato, E.; Ambrogi, L.; Ambrosi, G.;
   Ambrosio, M.; Anderson, J.; Anduze, M.; Angüner, E. O.; Antolini, E.;
   Antonelli, L. A.; Antonucci, M.; Antonuccio, V.; Antoranz, P.; Aramo,
   C.; Aravantinos, A.; Argan, A.; Armstrong, T.; Arnaldi, H.; Arnold, L.;
   Arrabito, L.; Arrieta, M.; Arrieta, M.; Asano, K.; Asorey, H. G.; Aune,
   T.; Singh, C. B.; Babic, A.; Backes, M.; Bais, A.; Bajtlik, S.; Balazs,
   C.; Balbo, M.; Balis, D.; Balkowski, C.; Ballester, O.; Ballet, J.;
   Balzer, A.; Bamba, A.; Bandiera, R.; Barber, A.; Barbier, C.; Barceló,
   M.; Barnacka, A.; Barres de Almeida, U.; Barrio, J. A.; Basso, S.;
   Bastieri, D.; Bauer, C.; Baushev, A.; Becciani, U.; Becherini, Y.;
   Becker Tjus, J.; Beckmann, V.; Bednarek, W.; Benbow, W.; Benedico
   Ventura, D.; Berdugo, J.; Berge, D.; Bernardini, E.; Bernhard, S.;
   Bernlöhr, K.; Bertucci, B.; Besel, M. -A.; Bhatt, N.; Bhattacharjee,
   P.; Bhattachryya, S.; Biasuzzi, B.; Bicknell, G.; Bigongiari, C.;
   Biland, A.; Billotta, S.; Bilnik, W.; Biondo, B.; Bird, T.; Birsin,
   E.; Bissaldi, E.; Biteau, J.; Bitossi, M.; Blanch Bigas, O.; Blasi,
   P.; Boehm, C.; Bogacz, L.; Bogdan, M.; Bohacova, M.; Boisson, C.;
   Boix Gargallo, J.; Bolmont, J.; Bonanno, G.; Bonardi, A.; Bonifacio,
   P.; Bonnoli, G.; Borkowski, J.; Bose, R.; Bosnjak, Z.; Bottani, A.;
   Böttcher, M.; Bousquet, J. -J.; Boutonnet, C.; Bouyjou, F.; Braiding,
   C.; Brandt, L.; Brau-Nogué, S.; Bregeon, J.; Bretz, T.; Briggs,
   M.; Brigida, M.; Bringmann, T.; Brisken, W.; Brocato, E.; Brook, P.;
   Brown, A. M.; Brun, P.; Brunetti, G.; Brunetti, L.; Bruno, P.; Bryan,
   M.; Buanes, T.; Bucciantini, N.; Buchholtz, G.; Buckley, J.; Bugaev,
   V.; Bühler, R.; Bulgarelli, A.; Bulik, T.; Burton, M.; Burtovoi, A.;
   Busetto, G.; Buson, S.; Buss, J.; Byrum, K.; Cameron, R.; Camprecios,
   J.; Canelli, F.; Canestrari, R.; Cantu, S.; Capalbi, M.; Capasso, M.;
   Capobianco, G.; Caraveo, P.; Cardenzana, J.; Carius, S.; Carlile, C.;
   Carmona, E.; Carosi, A.; Carosi, R.; Carr, J.; Carroll, M.; Carter,
   J.; Carton, P. -H.; Caruso, R.; Casandjian, J. -M.; Casanova, S.;
   Cascone, E.; Casiraghi, M.; Castellina, A.; Catalano, O.; Catalanotti,
   S.; Cavazzani, S.; Cazaux, S.; Cefalà, M.; Cerchiara, P.; Cereda,
   M.; Cerruti, M.; Chabanne, E.; Chadwick, P.; Champion, C.; Chaty,
   S.; Chaves, R.; Cheimets, P.; Chen, A.; Chen, X.; Chernyakova, M.;
   Chiappetti, L.; Chikawa, M.; Chinn, D.; Chitnis, V. R.; Cho, N.;
   Christov, A.; Chudoba, J.; Cieślar, M.; Cillis, A.; Ciocci, M. A.;
   Clay, R.; Cohen-Tanugi, J.; Colafrancesco, S.; Colin, P.; Colombo,
   E.; Colome, J.; Colonges, S.; Compin, M.; Conforti, V.; Connaughton,
   V.; Connell, S.; Conrad, J.; Contreras, J. L.; Coppi, P.; Corbel, S.;
   Coridian, J.; Corona, P.; Corti, D.; Cortina, J.; Cossio, L.; Costa,
   A.; Costantini, H.; Cotter, G.; Courty, B.; Covino, S.; Covone, G.;
   Crimi, G.; Criswell, S. J.; Crocker, R.; Croston, J.; Cusumano, G.;
   Da Vela, P.; Dale, Ø.; D'Ammando, F.; Dang, D.; Daniel, M.; Davids,
   I.; Dawson, B.; Dazzi, F.; de Aguiar Costa, B.; De Angelis, A.; de
   Araujo Cardoso, R. F.; De Caprio, V.; De Cesare, G.; De Franco, A.;
   De Frondat, F.; de Gouveia Dal Pino, E. M.; de la Calle, I.; De La
   Vega, G. A.; de los Reyes Lopez, R.; De Lotto, B.; De Luca, A.; de
   Mello Neto, J. R. T.; de Naurois, M.; de Oña Wilhelmi, E.; De Palma,
   F.; de Souza, V.; Decock, G.; Deil, C.; Del Santo, M.; Delagnes, E.;
   Deleglise, G.; Delgado, C.; della Volpe, D.; Deloye, P.; Depaola, G.;
   Detournay, M.; Dettlaff, A.; Di Girolamo, T.; Di Giulio, C.; Di Paola,
   A.; Di Pierro, F.; Di Sciascio, G.; Díaz, C.; Dick, J.; Dickinson, H.;
   Diebold, S.; Diez, V.; Digel, S.; Dipold, J.; Disset, G.; Distefano,
   A.; Djannati-Ataï, A.; Doert, M.; Dohmke, M.; Domainko, W.; Dominik,
   N.; Dominis Prester, D.; Donat, A.; Donnarumma, I.; Dorner, D.; Doro,
   M.; Dournaux, J. -L.; Doyle, K.; Drake, G.; Dravins, D.; Drury, L.;
   Dubus, G.; Dumas, D.; Dumm, J.; Durand, D.; D'Urso, D.; Dwarkadas,
   V.; Dyks, J.; Dyrda, M.; Ebr, J.; Echaniz, J. C.; Edy, E.; Egberts,
   K.; Egberts, K.; Eger, P.; Einecke, S.; Eisch, J.; Eisenkolb, F.;
   Eleftheriadis, C.; Elsässer, D.; Emmanoulopoulos, D.; Engelbrecht,
   C.; Engelhaupt, D.; Ernenwein, J. -P.; Errando, M.; Eschbach, S.;
   Etchegoyen, A.; Evans, P.; Fairbairn, M.; Falcone, A.; Fantinel, D.;
   Farakos, K.; Farnier, C.; Farrell, E.; Farrell, S.; Fasola, G.; Fegan,
   S.; Feinstein, F.; Ferenc, D.; Fernandez, A.; Fernandez-Alonso, M.;
   Ferreira, O.; Fesquet, M.; Fetfatzis, P.; Fiasson, A.; Filipčič, A.;
   Filipovic, M.; Fink, D.; Finley, C.; Finley, J. P.; Finoguenov, A.;
   Fioretti, V.; Fiorini, M.; Firpo Curcoll, R.; Fleischhack, H.; Flores,
   H.; Florin, D.; Föhr, C.; Fokitis, E.; Font, L.; Fontaine, G.; Fontes,
   B.; Forest, F.; Fornasa, M.; Förster, A.; Fortin, P.; Fortson, L.;
   Fouque, N.; Franckowiak, A.; Franco, F. J.; Frankowski, A.; Frega,
   N.; Freire Mota Albuquerque, I.; Freixas Coromina, L.; Fresnillo,
   L.; Fruck, C.; Fuessling, M.; Fugazza, D.; Fujita, Y.; Fukami, S.;
   Fukazawa, Y.; Fukuda, T.; Fukui, Y.; Funk, S.; Gäbele, W.; Gabici,
   S.; Gadola, A.; Galante, N.; Gall, D. D.; Gallant, Y.; Galloway, D.;
   Gallozzi, S.; Gao, S.; Garcia, B.; García Gil, R.; Garcia López,
   R.; Garczarczyk, M.; Gardiol, D.; Gargano, C.; Gargano, F.; Garozzo,
   S.; Garrecht, F.; Garrido, D.; Garrido, L.; Gascon, D.; Gaskins,
   J.; Gaudemard, J.; Gaug, M.; Gaweda, J.; Geffroy, N.; Gérard, L.;
   Ghalumyan, A.; Ghedina, A.; Ghigo, M.; Ghislain, P.; Giannakaki, E.;
   Gianotti, F.; Giarrusso, S.; Giavitto, G.; Giebels, B.; Giglietto,
   N.; Gika, V.; Gimenes, R.; Giomi, M.; Giommi, P.; Giordano, F.;
   Giovannini, G.; Giro, E.; Giroletti, M.; Giuliani, A.; Glicenstein,
   J. -F.; Godinovic, N.; Goldoni, P.; Gomez Berisso, M.; Gomez Vargas,
   G. A.; Gonzalez, M. M.; González, A.; González, F.; González
   Muñoz, A.; Gothe, K. S.; Gotz, D.; Grabarczyk, T.; Graciani, R.;
   Grandi, P.; Grañena, F.; Granot, J.; Grasseau, G.; Gredig, R.;
   Green, A. J.; Green, A. M.; Greenshaw, T.; Grenier, I.; Grillo, A.;
   Grondin, M. -H.; Grube, J.; Grudzinska, M.; Grygorczuk, J.; Guarino,
   V.; Guberman, D.; Gunji, S.; Gyuk, G.; Hadasch, D.; Hagedorn, A.;
   Hahn, J.; Hakansson, N.; Hamer Heras, N.; Hanabata, Y.; Hara, S.;
   Hardcastle, M. J.; Harris, J.; Hassan, T.; Hatanaka, K.; Haubold,
   T.; Haupt, A.; Hayakawa, T.; Hayashida, M.; Heller, M.; Heller, R.;
   Henault, F.; Henri, G.; Hermann, G.; Hermel, R.; Herrera Llorente, J.;
   Herrero, A.; Hervet, O.; Hidaka, N.; Hinton, J.; Hirai, W.; Hirotani,
   K.; Hoard, D.; Hoffmann, D.; Hofmann, W.; Hofverberg, P.; Holch, T.;
   Holder, J.; Hooper, S.; Horan, D.; Hörandel, J. R.; Hormigos, S.;
   Horns, D.; Hose, J.; Houles, J.; Hovatta, T.; Hrabovsky, M.; Hrupec,
   D.; Huet, J. -M.; Hütten, M.; Humensky, T. B.; Huovelin, J.; Huppert,
   J. -F.; Iacovacci, M.; Ibarra, A.; Idźkowski, B.; Ikawa, D.; Illa,
   J. M.; Impiombato, D.; Incorvaia, S.; Inome, Y.; Inoue, S.; Inoue,
   T.; Inoue, Y.; Iocco, F.; Ioka, K.; Iori, M.; Ishio, K.; Israel,
   G. L.; Jablonski, C.; Jacholkowska, A.; Jacquemier, J.; Jamrozy,
   M.; Janecek, P.; Janiak, M.; Jankowsky, F.; Jean, P.; Jeanney, C.;
   Jegouzo, I.; Jenke, P.; Jimenez, J. J.; Jingo, M.; Jingo, M.; Jocou,
   L.; Jogler, T.; Johnson, C. A.; Journet, L.; Juffroy, C.; Jung,
   I.; Kaaret, P. E.; Kagaya, M.; Kakuwa, J.; Kalekin, O.; Kalkuhl, C.;
   Kankanyan, R.; Karastergiou, A.; Kärcher, K.; Karczewski, M.; Karkar,
   S.; Karn, P.; Kasperek, J.; Katagiri, H.; Kataoka, J.; Katarzyński,
   K.; Katz, U.; Kaufmann, S.; Kawanaka, N.; Kawashima, T.; Kazanas,
   D.; Kelley-Hoskins, N.; Kellner-Leidel, B.; Kendziorra, E.; Kersten,
   J.; Khélifi, B.; Kieda, D. B.; Kihm, T.; Kisaka, S.; Kissmann, R.;
   Klepser, S.; Kluźniak, W.; Knapen, J.; Knapp, J.; Knödlseder, J.;
   Köck, F.; Kocot, J.; Kodakkadan, A.; Kodani, K.; Kohri, K.; Kojima,
   T.; Kokkotas, K.; Kolitzus, D.; Komin, N.; Kominis, I.; Konno, Y.;
   Kosack, K.; Koss, G.; Koul, R.; Kowal, G.; Koyama, S.; Kozioł,
   J.; Kraus, M.; Krause, J.; Krause, M.; Krawzcynski, H.; Krennrich,
   F.; Kretzschmann, A.; Kruger, P.; Kubo, H.; Kudryavtsev, V.; Kukec
   Mezek, G.; Kushida, J.; Kuznetsov, A.; La Barbera, A.; La Palombara,
   N.; La Parola, V.; La Rosa, G.; Laffon, H.; Lagadec, T.; Lahmann,
   R.; Lalik, K.; Lamanna, G.; Landriu, D.; Landt, H.; Lang, R. G.;
   Languignon, D.; Lapington, J.; Laporte, P.; Latovski, N.; Law-Green,
   D.; Le Fèvre, J. -P.; Le Flour, T.; Le Sidaner, P.; Lee, S. -H.; Lee,
   W. H.; Leffhalm, K.; Leich, H.; Leigui de Oliveira, M. A.; Lelas,
   D.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J. -P.; Leonard, R.;
   Leoni, R.; Lessio, L.; Leto, G.; Leveque, A.; Lieunard, B.; Limon,
   M.; Lindemann, R.; Lindfors, E.; Liolios, A.; Lipniacka, A.; Lockart,
   H.; Lohse, T.; Loiseau, D.; Łokas, E.; Lombardi, S.; Longo, F.;
   Longo, G.; Lopatin, A.; Lopez, M.; López-Coto, R.; López-Oramas,
   A.; Loreggia, D.; Louge, T.; Louis, F.; Lu, C. -C.; Lucarelli, F.;
   Lucchesi, D.; Lüdecke, H.; Luque-Escamilla, P. L.; Luz, O.; Lyard,
   E.; Maccarone, M. C.; Maccarone, T. J.; Mach, E.; Madejski, G. M.;
   Madonna, A.; Mahabir, M.; Maier, G.; Majumdar, P.; Makariev, M.;
   Malaguti, G.; Malaspina, G.; Mallot, A. K.; Maltezos, S.; Mancilla,
   A.; Mandat, D.; Maneva, G.; Manigot, P.; Mankushiyil, N.; Mannheim,
   K.; Maragos, N.; Marano, D.; Marchegiani, P.; Marcomini, J. A.;
   Marcowith, A.; Mariotti, M.; Marisaldi, M.; Markoff, S.; Marszałek,
   A.; Martens, C.; Martí, J.; Martin, J. -M.; Martin, P.; Martínez, G.;
   Martínez, M.; Martínez, O.; Marx, R.; Massimino, P.; Mastichiadis,
   A.; Mastroianni, S.; Mastropietro, M.; Masuda, S.; Matsumoto, H.;
   Matsuoka, S.; Mattiazzo, S.; Maurin, G.; Maxted, N.; Maya, J.; Mayer,
   M.; Mazin, D.; Mazureau, E.; Mazziotta, M. N.; Mc Comb, L.; McCann,
   A.; McCubbin, N.; McHardy, I.; McKay, R.; McKinney, K.; Meagher, K.;
   Medina, C.; Mehrez, F.; Melioli, C.; Melkumyan, D.; Melo, D.; Melse,
   T.; Mereghetti, S.; Mertsch, P.; Meyer, M.; Meyrelles, J. L., jr;
   Miccichè, A.; Michałowski, J.; Micolon, P.; Mientjes, P.; Mignot,
   S.; Mihailidis, A.; Mineo, T.; Minuti, M.; Mirabal, N.; Mirabel, F.;
   Miranda, J. M.; Mirzoyan, R.; Mistò, A.; Mitchell, A.; Mizuno, T.;
   Moderski, R.; Mognet, I.; Mohammed, M.; Moharana, R.; Molinari, E.;
   Monmarthe, E.; Monnier, G.; Montaruli, T.; Monte, C.; Monteiro, I.;
   Moore, P.; Moralejo Olaizola, A.; Morello, C.; Moretti, E.; Mori,
   K.; Morlino, G.; Morselli, A.; Mottez, F.; Moudden, Y.; Moulin, E.;
   Mrusek, I.; Mueller, S.; Mukherjee, R.; Munar-Adrover, P.; Mundell,
   C.; Muraishi, H.; Murase, K.; Muronga, A.; Murphy, A.; Nagataki,
   S.; Nagayoshi, T.; Nagesh, B. K.; Naito, T.; Nakajima, D.; Nakamori,
   T.; Nakayama, K.; Naumann, D.; Nayman, P.; Nellen, L.; Nemmen, R.;
   Neronov, A.; Neustroev, V.; Neyroud, N.; Nguyen, T.; Nicastro,
   L.; Nicolau-Kukliński, J.; Niederwanger, F.; Niedźwiecki, A.;
   Niemiec, J.; Nieto, D.; Nievas, M.; Nikolaidis, A.; Nishijima, K.;
   Nishikawa, K. -I.; Noda, K.; Nogues, L.; Nolan, S.; Northrop, R.;
   Nosek, D.; Nozka, L.; Nunio, F.; Oakes, L.; O'Brien, P.; Occhipinti,
   G.; O'Faolain de Bhroithe, A.; Ogino, M.; Ohira, Y.; Ohishi, M.; Ohm,
   S.; Ohoka, H.; Okumura, A.; Olive, J. -F.; Olszowski, D.; Ong, R. A.;
   Ono, S.; Orienti, M.; Orito, R.; Orlati, A.; Orlati, A.; Osborne, J.;
   Ostrowski, M.; Otero, L. A.; Ottaway, D.; Otte, N.; Oya, I.; Ozieblo,
   A.; Padovani, M.; Pagano, I.; Paiano, S.; Paizis, A.; Palacio, J.;
   Palatka, M.; Pallotta, J.; Panagiotidis, K.; Panazol, J. -L.; Paneque,
   D.; Panter, M.; Panzera, M. R.; Paoletti, R.; Paolillo, M.; Papayannis,
   A.; Papyan, G.; Paravac, A.; Paredes, J. M.; Pareschi, G.; Park, N.;
   Parsons, D.; Paśko, P.; Pavy, S.; Arribas, M. Paz; Pech, M.; Peck,
   A.; Pedaletti, G.; Peet, S.; Pelassa, V.; Pelat, D.; Peres, C.;
   Perez, M. d. C.; Perri, L.; Persic, M.; Petrashyk, A.; Petrucci,
   P. -O.; Peyaud, B.; Pfeifer, M.; Pfeiffer, G.; Piano, G.; Pichel,
   A.; Pieloth, D.; Pierbattista, M.; Pierre, E.; Pinto de Pinho, F.;
   García, C. Pio; Piret, Y.; Pita, S.; Planes, A.; Platino, M.; Platos,
   Ł.; Platzer, R.; Podkladkin, S.; Pogosyan, L.; Pohl, M.; Poinsignon,
   P.; Ponz, J. D.; Porcelli, A.; Potter, W.; Poulios, S.; Poutanen,
   J.; Prandini, E.; Prast, J.; Preece, R.; Profeti, F.; Prokhorov, D.;
   Prokoph, H.; Prouza, M.; Proyetti, M.; Pruchniewicz, R.; Pueschel,
   E.; Pühlhofer, G.; Puljak, I.; Punch, M.; Pyzioł, R.; Queiroz,
   F.; Quel, E. J.; Quinn, J.; Quirrenbach, A.; Racero, E.; Räck,
   T.; Rafalski, J.; Rafighi, I.; Rainò, S.; Rajda, P. J.; Rameez, M.;
   Rando, R.; Rannot, R. C.; Rataj, M.; Rateau, S.; Ravel, T.; Ravignani,
   D.; Razzaque, S.; Reardon, P.; Reimann, O.; Reimer, A.; Reimer, O.;
   Reitberger, K.; Renaud, M.; Renner, S.; Reposeur, T.; Rettig, R.;
   Reville, B.; Rhode, W.; Ribeiro, D.; Ribó, M.; Richards, G.; Richer,
   M. G.; Rico, J.; Ridky, J.; Rieger, F.; Ringegni, P.; Ristori, P. R.;
   Rivière, A.; Rivoire, S.; Roache, E.; Rodeghiero, G.; Rodriguez,
   J.; Rodriguez Fernandez, G.; Rodríguez Vázquez, J. J.; Rogers, T.;
   Rojas, G.; Romano, P.; Romay Rodriguez, M. P.; Romeo, G.; Romero,
   G. E.; Roncadelli, M.; Rose, J.; Rosen, S.; Rosier Lees, S.; Ross,
   D.; Rossiter, P.; Rouaix, G.; Rousselle, J.; Rovero, A. C.; Rowell,
   G.; Roy, F.; Royer, S.; Różańska, A.; Rudak, B.; Rugliancich,
   A.; Rulten, C.; Rupiński, M.; Russo, F.; Rutkowski, K.; Saavedra,
   O.; Sabatini, S.; Sacco, B.; Saemann, E. O.; Saggion, A.; Saha, L.;
   Sahakian, V.; Saito, K.; Saito, T.; Sakaki, N.; Salega, M.; Salek, D.;
   Salgado, J.; Salini, A.; Sanchez, D.; Sanchez, F.; Sanchez-Conde, M.;
   Sandaker, H.; Sandoval, A.; Sangiorgi, P.; Sanguillon, M.; Sano, H.;
   Santander, M.; Santangelo, A.; Santos, E. M.; Santos-Lima, R.; Sanuy,
   A.; Sapozhnikov, L.; Sarkar, S.; Satalecka, K.; Savalle, R.; Sawada,
   M.; Sayède, F.; Schafer, J.; Schanne, S.; Schanz, T.; Schioppa, E. J.;
   Schlenstedt, S.; Schlickeiser, R.; Schmidt, T.; Schmoll, J.; Schneider,
   M.; Schovanek, P.; Schubert, A.; Schultz, C.; Schultze, J.; Schulz,
   A.; Schulz, S.; Schure, K.; Schussler, F.; Schwab, T.; Schwanke, U.;
   Schwarz, J.; Schweizer, T.; Schwemmer, S.; Schwendicke, U.; Schwerdt,
   C.; Segreto, A.; Seiradakis, J. -H.; Sembroski, G. H.; Semikoz, D.;
   Serre, N.; Servillat, M.; Seweryn, K.; Shafi, N.; Sharma, M.; Shayduk,
   M.; Shellard, R. C.; Shibata, T.; Shiningayamwe Pandeni, K.; Shukla,
   A.; Shum, E.; Sidoli, L.; Sidz, M.; Sieiro, J.; Siejkowski, H.; Silk,
   J.; Sillanpää, A.; Simone, D.; Singh, B. B.; Sinha, A.; Sironi, G.;
   Sitarek, J.; Sizun, P.; Slyusar, V.; Smith, A.; Smith, J.; Sobczyńska,
   D.; Sol, H.; Sottile, G.; Sowiński, M.; Spanier, F.; Spengler, G.;
   Spiga, D.; Stadler, R.; Stahl, O.; Stamatescu, V.; Stamerra, A.;
   Stanič, S.; Starling, R.; Stawarz, Ł.; Steenkamp, R.; Stefanik, S.;
   Stegmann, C.; Steiner, S.; Stella, C.; Stergioulas, N.; Sternberger,
   R.; Sterzel, M.; Stevenson, B.; Stinzing, F.; Stodulska, M.; Stodulski,
   M.; Stolarczyk, T.; Straumann, U.; Strazzeri, E.; Stringhetti, L.;
   Strzys, M.; Stuik, R.; Sulanke, K. -H.; Supanitsky, A. D.; Suric, T.;
   Sushch, I.; Sutcliffe, P.; Sykes, J.; Szanecki, M.; Szepieniec, T.;
   Szwarnog, P.; Tacchini, A.; Tachihara, K.; Tagliaferri, G.; Tajima, H.;
   Takahashi, H.; Takahashi, K.; Takahashi, M.; Takalo, L.; Takami, H.;
   Talbot, G.; Tammi, J.; Tanaka, M.; Tanaka, S.; Tanaka, T.; Tanaka, Y.;
   Tanci, C.; Tarantino, E.; Tavani, M.; Tavecchio, F.; Tavernet, J. -P.;
   Tayabaly, K.; Tejedor, L. A.; Telezhinsky, I.; Temme, F.; Temnikov, P.;
   Tenzer, C.; Terada, Y.; Terrier, R.; Tescaro, D.; Teshima, M.; Testa,
   V.; Tezier, D.; Thayer, J.; Thomas, V.; Thornhill, J.; Thuermann,
   D.; Tibaldo, L.; Tibolla, O.; Tiengo, A.; Tijsseling, G.; Timpanaro,
   M. C.; Tluczykont, M.; Todero Peixoto, C. J.; Tokanai, F.; Tokarz, M.;
   Toma, K.; Toma, K.; Tomastik, J.; Tomono, Y.; Tonachini, A.; Tonev,
   D.; Torii, K.; Tornikoski, M.; Torres, D. F.; Torres, M.; Torresi, E.;
   Toscano, S.; Toso, G.; Tosti, G.; Totani, T.; Tothill, N.; Toussenel,
   F.; Tovmassian, G.; Townsley, C.; Toyama, T.; Travnicek, P.; Trifoglio,
   M.; Troyano Pujadas, I.; Troyano Pujadas, I.; Trzeciak, M.; Tsinganos,
   K.; Tsubone, Y.; Tsuchiya, Y.; Tsujimoto, S.; Tsuru, T.; Uchiyama, Y.;
   Umana, G.; Umetsu, Y.; Underwood, C.; Upadhya, S. S.; Uslenghi, M.;
   Vagnetti, F.; Valdes-Galicia, J.; Vallania, P.; Vallejo, G.; Valore,
   L.; van Driel, W.; van Eldik, C.; van Soelen, B.; Vandenbroucke, J.;
   Vanderwalt, J.; Vasileiadis, G.; Vassiliev, V.; Vázquez Acosta,
   M. L.; Vecchi, M.; Vegas, I.; Veitch, P.; Venema, L.; Venter, C.;
   Vercellone, S.; Vergani, S.; Verma, K.; Verzi, V.; Vettolani, G. P.;
   Viana, A.; Vicha, J.; Videla, M.; Vigorito, C.; Vincent, P.; Vincent,
   S.; Vink, J.; Vittorini, V.; Vlahakis, N.; Vlahos, L.; Voelk, H.;
   Vogler, P.; Voisin, V.; Vollhardt, A.; Volpicelli, A.; Vorobiov,
   S.; Vovk, I.; Vu, L. V.; Wagner, R.; Wagner, R. M.; Wagner, R. G.;
   Wagner, S. J.; Wakely, S. P.; Walter, R.; Walther, T.; Ward, J. E.;
   Ward, M.; Warda, K.; Warwick, R.; Wassberg, S.; Watson, J.; Wawer,
   P.; Wawrzaszek, R.; Webb, N.; Wegner, P.; Weinstein, A.; Weitzel, Q.;
   Wells, R.; Werner, F.; Werner, M.; Wetteskind, H.; White, M.; White,
   R.; Więcek, M.; Wierzcholska, A.; Wiesand, S.; Wijers, R.; Wild, N.;
   Wilhelm, A.; Wilkinson, M.; Will, M.; Williams, D. A.; Williams, J. T.;
   Willingale, R.; Winde, M.; Winiarski, K.; Winkler, H.; Wischnewski,
   R.; Wojcik, P.; Wolf, D.; Wood, M.; Wörnlein, A.; Wu, E.; Wu, T.;
   Yadav, K. K.; Yamamoto, H.; Yamamoto, T.; Yamazaki, R.; Yanagita, S.;
   Yang, L.; Yebras, J. M.; Yelos, D.; Yeung, W.; Yoshida, A.; Yoshida,
   T.; Yoshiike, S.; Yoshikoshi, T.; Yu, P.; Zabalza, V.; Zabalza, V.;
   Zacharias, M.; Zaharijas, G.; Zajczyk, A.; Zampieri, L.; Zandanel,
   F.; Zanin, R.; Zanmar Sanchez, R.; Zavrtanik, D.; Zavrtanik, M.;
   Zdziarski, A.; Zech, A.; Zechlin, H.; Zhao, A.; Ziegler, A.; Ziemann,
   J.; Ziętara, K.; Ziółkowski, J.; Zitelli, V.; Zoli, A.; Zurbach,
   C.; Żychowski, P.
Bibcode: 2015arXiv150805894C
Altcode:
  List of contributions from the CTA Consortium presented at the 34th
  International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague,
  The Netherlands.

Title: Particle acceleration in regions of magnetic flux emergence:
    a statistical approach using test-particle- and MHD-simulations
Authors: Vlahos, Loukas; Archontis, Vasilis; Isliker, Heinz
Bibcode: 2014cosp...40E3539V
Altcode:
  We consider 3D nonlinear MHD simulations of an emerging flux tube, from
  the convection zone into the corona, focusing on the coronal part of
  the simulations. We first analyze the statistical nature and spatial
  structure of the electric field, calculating histograms and making
  use of iso-contour visualizations. Then test-particle simulations are
  performed for electrons, in order to study heating and acceleration
  phenomena, as well as to determine HXR emission. This study is done by
  comparatively exploring quiet, turbulent explosive, and mildly explosive
  phases of the MHD simulations. Also, the importance of collisional and
  relativistic effects is assessed, and the role of the integration time
  is investigated. Particular aim of this project is to verify the quasi-
  linear assumptions made in standard transport models, and to identify
  possible transport effects that cannot be captured with the latter. In
  order to determine the relation of our results to Fermi acceleration
  and Fokker-Planck modeling, we determine the standard transport
  coefficients. After all, we find that the electric field of the MHD
  simulations must be downscaled in order to prevent an un-physically
  high degree of acceleration, and the value chosen for the scale factor
  strongly affects the results. In different MHD time-instances we find
  heating to take place, and acceleration that depends on the level of
  MHD turbulence. Also, acceleration appears to be a transient phenomenon,
  there is a kind of saturation effect, and the parallel dynamics clearly
  dominate the energetics. The HXR spectra are not yet really compatible
  with observations, we have though to further explore the scaling of
  the electric field and the integration times used.

Title: Particle acceleration in solar active regions being in the
    state of self-organized criticality.
Authors: Vlahos, Loukas
Bibcode: 2014cosp...40E3540V
Altcode:
  We review the recent observational results on flare initiation and
  particle acceleration in solar active regions. Elaborating a statistical
  approach to describe the spatiotemporally intermittent electric field
  structures formed inside a flaring solar active region, we investigate
  the efficiency of such structures in accelerating charged particles
  (electrons and protons). The large-scale magnetic configuration in the
  solar atmosphere responds to the strong turbulent flows that convey
  perturbations across the active region by initiating avalanche-type
  processes. The resulting unstable structures correspond to small-scale
  dissipation regions hosting strong electric fields. Previous research
  on particle acceleration in strongly turbulent plasmas provides
  a general framework for addressing such a problem. This framework
  combines various electromagnetic field configurations obtained by
  magnetohydrodynamical (MHD) or cellular automata (CA) simulations, or
  by employing a statistical description of the field’s strength and
  configuration with test particle simulations. We work on data-driven 3D
  magnetic field extrapolations, based on a self-organized criticality
  models (SOC). A relativistic test-particle simulation traces each
  particle’s guiding center within these configurations. Using the
  simulated particle-energy distributions we test our results against
  observations, in the framework of the collisional thick target model
  (CTTM) of solar hard X-ray (HXR) emission and compare our results with
  the current observations.

Title: A statistical study of current-sheet formation above solar
    active regions based on selforganized criticality
Authors: Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M.;
   Anastasiadis, A.; Toutountzi, A.
Bibcode: 2013hell.conf...16D
Altcode:
  We treat flaring solar active regions as physical systems having
  reached the self-organized critical state. Their evolving magnetic
  configurations in the low corona may satisfy an instability criterion,
  related to the excession of a specific threshold in the curl of the
  magnetic field. This imposed instability criterion implies an almost
  zero resistivity everywhere in the solar corona, except in regions where
  magnetic-field discontinuities and. hence, local currents, reach the
  critical value. In these areas, current-driven instabilities enhance
  the resistivity by many orders of magnitude forming structures which
  efficiently accelerate charged particles. Simulating the formation
  of such structures (thought of as current sheets) via a refined SOC
  cellular-automaton model provides interesting information regarding
  their statistical properties. It is shown that the current density in
  such unstable regions follows power-law scaling. Furthermore, the size
  distribution of the produced current sheets is best fitted by power
  laws, whereas their formation probability is investigated against
  the photospheric magnetic configuration (e.g. Polarity Inversion
  Lines, Plage). The average fractal dimension of the produced current
  sheets is deduced depending on the selected critical threshold. The
  above-mentioned statistical description of intermittent electric
  field structures can be used by collisional relativistic test particle
  simulations, aiming to interpret particle acceleration in flaring active
  regions and in strongly turbulent media in astrophysical plasmas. The
  above work is supported by the Hellenic National Space Weather Research
  Network (HNSWRN) via the THALIS Programme.

Title: A Data-Driven, Integrated Flare Model Based on Self-Organized
    Criticality
Authors: Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M.
Bibcode: 2013hell.conf....7D
Altcode:
  We interpret solar flares as events originating in solar active regions
  having reached the self-organized critical state, by alternatively
  using two versions of an "integrated flare model" - one static and
  one dynamic. In both versions the initial conditions are derived
  from observations aiming to investigate whether well-known scaling
  laws observed in the distribution functions of characteristic flare
  parameters are reproduced after the self-organized critical state
  has been reached. In the static model, we first apply a nonlinear
  force-free extrapolation that reconstructs the three-dimensional
  magnetic fields from two-dimensional vector magnetograms. We then locate
  magnetic discontinuities exceeding a threshold in the Laplacian of the
  magnetic field. These discontinuities are relaxed in local diffusion
  events, implemented in the form of cellular-automaton evolution
  rules. Subsequent loading and relaxation steps lead the system to
  self-organized criticality, after which the statistical properties of
  the simulated events are examined. In the dynamic version we deploy an
  enhanced driving mechanism, which utilizes the observed evolution of
  active regions, making use of sequential vector magnetograms. We first
  apply the static cellular automaton model to consecutive solar vector
  magnetograms until the self-organized critical state is reached. We
  then evolve the magnetic field inbetween these processed snapshots
  through spline interpolation, acting as a natural driver in the dynamic
  model. The identification of magnetically unstable sites as well as
  their relaxation follow the same rules as in the static model after each
  interpolation step. Subsequent interpolation/driving and relaxation
  steps cover all transitions until the end of the sequence. Physical
  requirements, such as the divergence-free condition for the magnetic
  field vector, are approximately satisfied in both versions of the
  model. We obtain robust power laws in the distribution functions of
  the modelled flaring events with scaling indices in good agreement
  with observations. We therefore conclude that well-known statistical
  properties of flares are reproduced after active regions reach
  self-organized criticality. The significant enhancement in both the
  static and the dynamic integrated flare models is that they initiate
  the simulation from observations, thus facilitating energy calculation
  in physical units. Especially in the dynamic version of the model,
  the driving of the system is based on observed, evolving vector
  magnetograms, allowing for the separation between MHD and kinetic
  timescales through the assignment of distinct MHD timestamps to each
  interpolation step.

Title: Particle Acceleration in a Statistically Modeled Solar
    Active-Region Corona
Authors: Toutounzi, A.; Vlahos, L.; Isliker, H.; Dimitropoulou, M.;
   Anastasiadis, A.; Georgoulis, M.
Bibcode: 2013hell.conf....8T
Altcode:
  Elaborating a statistical approach to describe the spatiotemporally
  intermittent electric field structures formed inside a flaring solar
  active region, we investigate the efficiency of such structures
  in accelerating charged particles (electrons). The large-scale
  magnetic configuration in the solar atmosphere responds to the strong
  turbulent flows that convey perturbations across the active region by
  initiating avalanche-type processes. The resulting unstable structures
  correspond to small-scale dissipation regions hosting strong electric
  fields. Previous research on particle acceleration in strongly turbulent
  plasmas provides a general framework for addressing such a problem. This
  framework combines various electromagnetic field configurations obtained
  by magnetohydrodynamical (MHD) or cellular automata (CA) simulations,
  or by employing a statistical description of the field's strength
  and configuration with test particle simulations. Our objective is to
  complement previous work done on the subject. As in previous efforts,
  a set of three probability distribution functions describes our
  ad-hoc electromagnetic field configurations. In addition, we work on
  data-driven 3D magnetic field extrapolations. A collisional relativistic
  test-particle simulation traces each particle's guiding center
  within these configurations. We also find that an interplay between
  different electron populations (thermal/non-thermal, ambient/injected)
  in our simulations may also address, via a re-acceleration mechanism,
  the so called `number problem'. Using the simulated particle-energy
  distributions at different heights of the cylinder we test our results
  against observations, in the framework of the collisional thick target
  model (CTTM) of solar hard X-ray (HXR) emission. The above work is
  supported by the Hellenic National Space Weather Research Network
  (HNSWRN) via the THALIS Programme.

Title: Sun-to-Earth Analysis of a Major Geoeffective Solar Eruption
    within the Framework of the
Authors: Patsourakos, S.; Vlahos, L.; Georgoulis, M.; Tziotziou,
   K.; Nindos, A.; Podladchikova, O.; Vourlidas, A.; Anastasiadis, A.;
   Sandberg, I.; Tsinganos, K.; Daglis, I.; Hillaris, A.; Preka-Papadema,
   P.; Sarris, M.; Sarris, T.
Bibcode: 2013hell.conf...10P
Altcode:
  Transient expulsions of gigantic clouds of solar coronal plasma into
  the interplanetary space in the form of Coronal Mass Ejections (CMEs)
  and sudden, intense flashes of electromagnetic radiation, solar flares,
  are well-established drivers of the variable Space Weather. Given the
  innate, intricate links and connections between the solar drivers and
  their geomagnetic effects, synergistic efforts assembling all pieces
  of the puzzle along the Sun-Earth line are required to advance our
  understanding of the physics of Space Weather. This is precisely the
  focal point of the Hellenic National Space Weather Research Network
  (HNSWRN) under the THALIS Programme. Within the HNSWRN framework,
  we present here the first results from a coordinated multi-instrument
  case study of a major solar eruption (X5.4 and X1.3 flares associated
  with two ultra-fast (&gt;2000 km/s) CMEs) which were launched early
  on 7 March 2012 and triggered an intense geomagnetic storm (min Dst
  =-147 nT) approximately two days afterwards. Several elements of
  the associated phenomena, such as the flare and CME, EUV wave, WL
  shock, proton and electron event, interplanetary type II radio burst,
  ICME and magnetic cloud and their spatiotemporal relationships and
  connections are studied all way from Sun to Earth. To this end, we
  make use of satellite data from a flotilla of solar, heliospheric and
  magnetospheric missions and monitors (e.g., SDO, STEREO, WIND, ACE,
  Herschel, Planck and INTEGRAL). We also present our first steps toward
  formulating a cohesive physical scenario to explain the string of the
  observables and to assess the various physical mechanisms than enabled
  and gave rise to the significant geoeffectiveness of the eruption.

Title: CTA contributions to the 33rd International Cosmic Ray
    Conference (ICRC2013)
Authors: CTA Consortium, The; :; Abril, O.; Acharya, B. S.; Actis, M.;
   Agnetta, G.; Aguilar, J. A.; Aharonian, F.; Ajello, M.; Akhperjanian,
   A.; Alcubierre, M.; Aleksic, J.; Alfaro, R.; Aliu, E.; Allafort,
   A. J.; Allan, D.; Allekotte, I.; Aloisio, R.; Amato, E.; Ambrosi,
   G.; Ambrosio, M.; Anderson, J.; Angüner, E. O.; Antonelli, L. A.;
   Antonuccio, V.; Antonucci, M.; Antoranz, P.; Aravantinos, A.; Argan,
   A.; Arlen, T.; Aramo, C.; Armstrong, T.; Arnaldi, H.; Arrabito, L.;
   Asano, K.; Ashton, T.; Asorey, H. G.; Aune, T.; Awane, Y.; Baba, H.;
   Babic, A.; Baby, N.; Bähr, J.; Bais, A.; Baixeras, C.; Bajtlik, S.;
   Balbo, M.; Balis, D.; Balkowski, C.; Ballet, J.; Bamba, A.; Bandiera,
   R.; Barber, A.; Barbier, C.; Barceló, M.; Barnacka, A.; Barnstedt,
   J.; Barres de Almeida, U.; Barrio, J. A.; Basili, A.; Basso, S.;
   Bastieri, D.; Bauer, C.; Baushev, A.; Becciani, U.; Becerra, J.;
   Becerra, J.; Becherini, Y.; Bechtol, K. C.; Becker Tjus, J.; Beckmann,
   V.; Bednarek, W.; Behera, B.; Belluso, M.; Benbow, W.; Berdugo, J.;
   Berge, D.; Berger, K.; Bernard, F.; Bernardino, T.; Bernlöhr, K.;
   Bertucci, B.; Bhat, N.; Bhattacharyya, S.; Biasuzzi, B.; Bigongiari,
   C.; Biland, A.; Billotta, S.; Bird, T.; Birsin, E.; Bissaldi, E.;
   Biteau, J.; Bitossi, M.; Blake, S.; Blanch Bigas, O.; Blasi, P.;
   Bobkov, A.; Boccone, V.; Böttcher, M.; Bogacz, L.; Bogart, J.;
   Bogdan, M.; Boisson, C.; Boix Gargallo, J.; Bolmont, J.; Bonanno,
   G.; Bonardi, A.; Bonev, T.; Bonifacio, P.; Bonnoli, G.; Bordas,
   P.; Borgland, A.; Borkowski, J.; Bose, R.; Botner, O.; Bottani, A.;
   Bouchet, L.; Bourgeat, M.; Boutonnet, C.; Bouvier, A.; Brau-Nogué, S.;
   Braun, I.; Bretz, T.; Briggs, M.; Brigida, M.; Bringmann, T.; Britto,
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   Krause, J.; Krawzcynski, H.; Krennrich, F.; Krepps, A.; Kretzschmann,
   A.; Krobot, R.; Krueger, P.; Kubo, H.; Kudryavtsev, V. A.; Kushida,
   J.; Kuznetsov, A.; La Barbera, A.; La Palombara, N.; La Parola, V.;
   La Rosa, G.; Lacombe, K.; Lamanna, G.; Lande, J.; Languignon, D.;
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   T.; Le Padellec, A.; Lee, S. -H.; Lee, W. H.; Lefèvre, J. -P.; Leich,
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   R.; Leopold, D. J.; Lerch, T.; Lessio, L.; Leto, G.; Lieunard, B.;
   Lieunard, S.; Lindemann, R.; Lindfors, E.; Liolios, A.; Lipniacka,
   A.; Lockart, H.; Lohse, T.; Lombardi, S.; Longo, F.; Lopatin, A.;
   Lopez, M.; López-Coto, R.; López-Oramas, A.; Lorca, A.; Lorenz,
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   M. C.; Maccarone, T. J.; Madejski, G. M.; Madhavan, A.; Mahabir, M.;
   Maier, G.; Majumdar, P.; Malaguti, G.; Malaspina, G.; Maltezos, S.;
   Manalaysay, A.; Mancilla, A.; Mandat, D.; Maneva, G.; Mangano, A.;
   Manigot, P.; Mannheim, K.; Manthos, I.; Maragos, N.; Marcowith, A.;
   Mariotti, M.; Marisaldi, M.; Markoff, S.; Marszałek, A.; Martens,
   C.; Martí, J.; Martin, J. -M.; Martin, P.; Martínez, G.; Martínez,
   F.; Martínez, M.; Massaro, F.; Masserot, A.; Mastichiadis, A.;
   Mathieu, A.; Matsumoto, H.; Mattana, F.; Mattiazzo, S.; Maurer, A.;
   Maurin, G.; Maxfield, S.; Maya, J.; Mazin, D.; Mc Comb, L.; McCann,
   A.; McCubbin, N.; McHardy, I.; McKay, R.; Meagher, K.; Medina, C.;
   Melioli, C.; Melkumyan, D.; Melo, D.; Mereghetti, S.; Mertsch, P.;
   Meucci, M.; Meyer, M.; Michałowski, J.; Micolon, P.; Mihailidis,
   A.; Mineo, T.; Minuti, M.; Mirabal, N.; Mirabel, F.; Miranda, J. M.;
   Mirzoyan, R.; Mistò, A.; Mizuno, T.; Moal, B.; Moderski, R.; Mognet,
   I.; Molinari, E.; Molinaro, M.; Montaruli, T.; Monte, C.; Monteiro, I.;
   Moore, P.; Moralejo Olaizola, A.; Mordalska, M.; Morello, C.; Mori,
   K.; Morlino, G.; Morselli, A.; Mottez, F.; Moudden, Y.; Moulin, E.;
   Mrusek, I.; Mukherjee, R.; Munar-Adrover, P.; Muraishi, H.; Murase, K.;
   StJ. Murphy, A.; Nagataki, S.; Naito, T.; Nakajima, D.; Nakamori, T.;
   Nakayama, K.; Naumann, C.; Naumann, D.; Naumann-Godo, M.; Nayman, P.;
   Nedbal, D.; Neise, D.; Nellen, L.; Neronov, A.; Neustroev, V.; Neyroud,
   N.; Nicastro, L.; Nicolau-Kukliński, J.; Niedźwiecki, A.; Niemiec,
   J.; Nieto, D.; Nikolaidis, A.; Nishijima, K.; Nishikawa, K. -I.;
   Noda, K.; Nolan, S.; Northrop, R.; Nosek, D.; Nowak, N.; Nozato, A.;
   Oakes, L.; O'Brien, P. T.; Ohira, Y.; Ohishi, M.; Ohm, S.; Ohoka, H.;
   Okuda, T.; Okumura, A.; Olive, J. -F.; Ong, R. A.; Orito, R.; Orr, M.;
   Osborne, J. P.; Ostrowski, M.; Otero, L. A.; Otte, N.; Ovcharov, E.;
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   G.; Ponz, J. D.; Potter, W.; Poutanen, J.; Prandini, E.; Prast,
   J.; Preece, R.; Profeti, F.; Prokoph, H.; Prouza, M.; Proyetti, M.;
   Puerto-Giménez, I.; Pühlhofer, G.; Puljak, I.; Punch, M.; Pyzioł,
   R.; Quel, E. J.; Quesada, J.; Quinn, J.; Quirrenbach, A.; Racero, E.;
   Rainò, S.; Rajda, P. J.; Rameez, M.; Ramon, P.; Rando, R.; Rannot,
   R. C.; Rataj, M.; Raue, M.; Ravignani, D.; Reardon, P.; Reimann,
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   O.; Sacco, B.; Saemann, E. O.; Saggion, A.; Sahakian, V.; Saito, K.;
   Saito, T.; Saito, Y.; Sakaki, N.; Sakonaka, R.; Salini, A.; Sanchez,
   F.; Sanchez-Conde, M.; Sandoval, A.; Sandaker, H.; Sant'Ambrogio, E.;
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   Scapin, V.; Scarcioffolo, M.; Schafer, J.; Schanz, T.; Schlenstedt,
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   A.; Schure, K.; Schussler, F.; Schwab, T.; Schwanke, U.; Schwarz,
   J.; Schwarzburg, S.; Schweizer, T.; Schwemmer, S.; Schwendicke, U.;
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   N.; Sobczyńska, D.; Sol, H.; Sottile, G.; Sowiński, M.; Spanier,
   F.; Spiga, D.; Spyrou, S.; Stamatescu, V.; Stamerra, A.; Starling,
   R. L. C.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Steiner, S.;
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   Stringhetti, L.; Suarez, A.; Suchenek, M.; Sugawara, R.; Sulanke,
   K. -H.; Sun, S.; Supanitsky, A. D.; Suric, T.; Sutcliffe, P.; Sykes,
   J. M.; Szanecki, M.; Szepieniec, T.; Szostek, A.; Tagliaferri, G.;
   Tajima, H.; Takahashi, H.; Takahashi, K.; Takalo, L.; Takami, H.;
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   M.; Tavernet, J. -P.; Tejedor, L. A.; Telezhinsky, I.; Temnikov, P.;
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   D.; Thayer, J.; Thuermann, D.; Tibaldo, L.; Tibaldo, L.; Tibolla,
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   C. J.; Tokanai, F.; Tokarz, M.; Toma, K.; Tonachini, A.; Torii, K.;
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   Tosti, G.; Totani, T.; Toussenel, F.; Tovmassian, G.; Travnicek, P.;
   Treves, A.; Trifoglio, M.; Troyano, I.; Tsinganos, K.; Ueno, H.; Umana,
   G.; Umehara, K.; Upadhya, S. S.; Usher, T.; Uslenghi, M.; Vagnetti, F.;
   Valdes-Galicia, J. F.; Vallania, P.; Vallejo, G.; van Driel, W.; van
   Eldik, C.; Vandenbrouke, J.; Vanderwalt, J.; Vankov, H.; Vasileiadis,
   G.; Vassiliev, V.; Veberic, D.; Vegas, I.; Vercellone, S.; Vergani,
   S.; Verzi, V.; Vettolani, G. P.; Veyssière, C.; Vialle, J. P.;
   Viana, A.; Videla, M.; Vigorito, C.; Vincent, P.; Vincent, S.; Vink,
   J.; Vlahakis, N.; Vlahos, L.; Vogler, P.; Voisin, V.; Vollhardt, A.;
   von Gunten, H. -P.; Vorobiov, S.; Vuerli, C.; Waegebaert, V.; Wagner,
   R.; Wagner, R. G.; Wagner, S.; Wakely, S. P.; Walter, R.; Walther,
   T.; Warda, K.; Warwick, R. S.; Wawer, P.; Wawrzaszek, R.; Webb, N.;
   Wegner, P.; Weinstein, A.; Weitzel, Q.; Welsing, R.; Werner, M.;
   Wetteskind, H.; White, R. J.; Wierzcholska, A.; Wiesand, S.; Wilhelm,
   A.; Wilkinson, M. I.; Williams, D. A.; Willingale, R.; Winde, M.;
   Winiarski, K.; Wischnewski, R.; Wiśniewski, Ł.; Wojcik, P.; Wood,
   M.; Wörnlein, A.; Xiong, Q.; Yadav, K. K.; Yamamoto, H.; Yamamoto,
   T.; Yamazaki, R.; Yanagita, S.; Yebras, J. M.; Yelos, D.; Yoshida,
   A.; Yoshida, T.; Yoshikoshi, T.; Yu, P.; Zabalza, V.; Zacharias, M.;
   Zajczyk, A.; Zampieri, L.; Zanin, R.; Zdziarski, A.; Zech, A.; Zhao,
   A.; Zhou, X.; Zietara, K.; Ziolkowski, J.; Ziółkowski, P.; Zitelli,
   V.; Zurbach, C.; Zychowski, P.
Bibcode: 2013arXiv1307.2232C
Altcode:
  Compilation of CTA contributions to the proceedings of the 33rd
  International Cosmic Ray Conference (ICRC2013), which took place in
  2-9 July, 2013, in Rio de Janeiro, Brazil

Title: Dynamic data-driven integrated flare model based on
    self-organized criticality
Authors: Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M. K.
Bibcode: 2013A&A...553A..65D
Altcode:
  Context. We interpret solar flares as events originating in active
  regions that have reached the self-organized critical state. We describe
  them with a dynamic integrated flare model whose initial conditions
  and driving mechanism are derived from observations. <BR /> Aims: We
  investigate whether well-known scaling laws observed in the distribution
  functions of characteristic flare parameters are reproduced after
  the self-organized critical state has been reached. <BR /> Methods:
  To investigate whether the distribution functions of total energy,
  peak energy, and event duration follow the expected scaling laws,
  we first applied the previously reported static cellular automaton
  model to a time series of seven solar vector magnetograms of the NOAA
  active region 8210 recorded by the Imaging Vector Magnetograph on May
  1 1998 between 18:59 UT and 23:16 UT until the self-organized critical
  state was reached. We then evolved the magnetic field between these
  processed snapshots through spline interpolation, mimicking a natural
  driver in our dynamic model. We identified magnetic discontinuities
  that exceeded a threshold in the Laplacian of the magnetic field after
  each interpolation step. These discontinuities were relaxed in local
  diffusion events, implemented in the form of cellular automaton
  evolution rules. Subsequent interpolation and relaxation steps
  covered all transitions until the end of the processed magnetograms'
  sequence. We additionally advanced each magnetic configuration that
  has reached the self-organized critical state (SOC configuration)
  by the static model until 50 more flares were triggered, applied
  the dynamic model again to the new sequence, and repeated the same
  process sufficiently often to generate adequate statistics. Physical
  requirements, such as the divergence-free condition for the magnetic
  field, were approximately imposed. <BR /> Results: We obtain robust
  power laws in the distribution functions of the modeled flaring events
  with scaling indices that agree well with observations. Peak and total
  flare energy obey single power laws with indices -1.65 ± 0.11 and
  -1.47 ± 0.13, while the flare duration is best fitted with a double
  power law (-2.15 ± 0.15 and -3.60 ± 0.09 for the flatter and steeper
  parts, respectively). <BR /> Conclusions: We conclude that well-known
  statistical properties of flares are reproduced after active regions
  reach the state of self-organized criticality. A significant enhancement
  of our refined cellular automaton model is that it initiates and further
  drives the simulation from observed evolving vector magnetograms, thus
  facilitating energy calculation in physical units, while a separation
  between MHD and kinetic timescales is possible by assigning distinct
  MHD timestamps to each interpolation step.

Title: Introducing the CTA concept
Authors: Acharya, B. S.; Actis, M.; Aghajani, T.; Agnetta, G.;
   Aguilar, J.; Aharonian, F.; Ajello, M.; Akhperjanian, A.; Alcubierre,
   M.; Aleksić, J.; Alfaro, R.; Aliu, E.; Allafort, A. J.; Allan, D.;
   Allekotte, I.; Amato, E.; Anderson, J.; Angüner, E. O.; Antonelli,
   L. A.; Antoranz, P.; Aravantinos, A.; Arlen, T.; Armstrong, T.;
   Arnaldi, H.; Arrabito, L.; Asano, K.; Ashton, T.; Asorey, H. G.; Awane,
   Y.; Baba, H.; Babic, A.; Baby, N.; Bähr, J.; Bais, A.; Baixeras, C.;
   Bajtlik, S.; Balbo, M.; Balis, D.; Balkowski, C.; Bamba, A.; Bandiera,
   R.; Barber, A.; Barbier, C.; Barceló, M.; Barnacka, A.; Barnstedt, J.;
   Barres de Almeida, U.; Barrio, J. A.; Basili, A.; Basso, S.; Bastieri,
   D.; Bauer, C.; Baushev, A.; Becerra, J.; Becherini, Y.; Bechtol, K. C.;
   Becker Tjus, J.; Beckmann, V.; Bednarek, W.; Behera, B.; Belluso,
   M.; Benbow, W.; Berdugo, J.; Berger, K.; Bernard, F.; Bernardino, T.;
   Bernlöhr, K.; Bhat, N.; Bhattacharyya, S.; Bigongiari, C.; Biland,
   A.; Billotta, S.; Bird, T.; Birsin, E.; Bissaldi, E.; Biteau, J.;
   Bitossi, M.; Blake, S.; Blanch Bigas, O.; Blasi, P.; Bobkov, A.;
   Boccone, V.; Boettcher, M.; Bogacz, L.; Bogart, J.; Bogdan, M.;
   Boisson, C.; Boix Gargallo, J.; Bolmont, J.; Bonanno, G.; Bonardi,
   A.; Bonev, T.; Bonifacio, P.; Bonnoli, G.; Bordas, P.; Borgland,
   A.; Borkowski, J.; Bose, R.; Botner, O.; Bottani, A.; Bouchet, L.;
   Bourgeat, M.; Boutonnet, C.; Bouvier, A.; Brau-Nogué, S.; Braun, I.;
   Bretz, T.; Briggs, M.; Bringmann, T.; Brook, P.; Brun, P.; Brunetti,
   L.; Buanes, T.; Buckley, J.; Buehler, R.; Bugaev, V.; Bulgarelli, A.;
   Bulik, T.; Busetto, G.; Buson, S.; Byrum, K.; Cailles, M.; Cameron,
   R.; Camprecios, J.; Canestrari, R.; Cantu, S.; Capalbi, M.; Caraveo,
   P.; Carmona, E.; Carosi, A.; Carr, J.; Carton, P. -H.; Casanova,
   S.; Casiraghi, M.; Catalano, O.; Cavazzani, S.; Cazaux, S.; Cerruti,
   M.; Chabanne, E.; Chadwick, P.; Champion, C.; Chen, A.; Chiang, J.;
   Chiappetti, L.; Chikawa, M.; Chitnis, V. R.; Chollet, F.; Chudoba, J.;
   Cieślar, M.; Cillis, A.; Cohen-Tanugi, J.; Colafrancesco, S.; Colin,
   P.; Colome, J.; Colonges, S.; Compin, M.; Conconi, P.; Conforti, V.;
   Connaughton, V.; Conrad, J.; Contreras, J. L.; Coppi, P.; Corona, P.;
   Corti, D.; Cortina, J.; Cossio, L.; Costantini, H.; Cotter, G.; Courty,
   B.; Couturier, S.; Covino, S.; Crimi, G.; Criswell, S. J.; Croston,
   J.; Cusumano, G.; Dafonseca, M.; Dale, O.; Daniel, M.; Darling, J.;
   Davids, I.; Dazzi, F.; De Angelis, A.; De Caprio, V.; De Frondat,
   F.; de Gouveia Dal Pino, E. M.; de la Calle, I.; De La Vega, G. A.;
   de los Reyes Lopez, R.; De Lotto, B.; De Luca, A.; de Mello Neto,
   J. R. T.; de Naurois, M.; de Oliveira, Y.; de Oña Wilhelmi, E.;
   de Souza, V.; Decerprit, G.; Decock, G.; Deil, C.; Delagnes, E.;
   Deleglise, G.; Delgado, C.; Della Volpe, D.; Demange, P.; Depaola,
   G.; Dettlaff, A.; Di Paola, A.; Di Pierro, F.; Díaz, C.; Dick, J.;
   Dickherber, R.; Dickinson, H.; Diez-Blanco, V.; Digel, S.; Dimitrov,
   D.; Disset, G.; Djannati-Ataï, A.; Doert, M.; Dohmke, M.; Domainko,
   W.; Dominis Prester, D.; Donat, A.; Dorner, D.; Doro, M.; Dournaux,
   J. -L.; Drake, G.; Dravins, D.; Drury, L.; Dubois, F.; Dubois, R.;
   Dubus, G.; Dufour, C.; Dumas, D.; Dumm, J.; Durand, D.; Dyks, J.;
   Dyrda, M.; Ebr, J.; Edy, E.; Egberts, K.; Eger, P.; Einecke, S.;
   Eleftheriadis, C.; Elles, S.; Emmanoulopoulos, D.; Engelhaupt, D.;
   Enomoto, R.; Ernenwein, J. -P.; Errando, M.; Etchegoyen, A.; Evans,
   P.; Falcone, A.; Fantinel, D.; Farakos, K.; Farnier, C.; Fasola,
   G.; Favill, B.; Fede, E.; Federici, S.; Fegan, S.; Feinstein, F.;
   Ferenc, D.; Ferrando, P.; Fesquet, M.; Fiasson, A.; Fillin-Martino,
   E.; Fink, D.; Finley, C.; Finley, J. P.; Fiorini, M.; Firpo Curcoll,
   R.; Flores, H.; Florin, D.; Focke, W.; Föhr, C.; Fokitis, E.; Font,
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   N.; Franckowiak, A.; Fransson, C.; Fraser, G.; Frei, R.; Albuquerque,
   I. F. M.; Fresnillo, L.; Fruck, C.; Fujita, Y.; Fukazawa, Y.; Fukui,
   Y.; Funk, S.; Gäbele, W.; Gabici, S.; Gabriele, R.; Gadola, A.;
   Galante, N.; Gall, D.; Gallant, Y.; Gámez-García, J.; García, B.;
   Garcia López, R.; Gardiol, D.; Garrido, D.; Garrido, L.; Gascon,
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   Ghedina, A.; Ghigo, M.; Giannakaki, E.; Gianotti, F.; Giarrusso, S.;
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   E.; Giuliani, A.; Glanzman, T.; Glicenstein, J. -F.; Godinovic, N.;
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   J.; Kuznetsov, A.; La Barbera, A.; La Palombara, N.; La Parola, V.;
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   Lombardi, S.; Lopatin, A.; Lopez, M.; López-Coto, R.; López-Oramas,
   A.; Lorca, A.; Lorenz, E.; Lubinski, P.; Lucarelli, F.; Lüdecke, H.;
   Ludwin, J.; Luque-Escamilla, P. L.; Lustermann, W.; Luz, O.; Lyard,
   E.; Maccarone, M. C.; Maccarone, T. J.; Madejski, G. M.; Madhavan,
   A.; Mahabir, M.; Maier, G.; Majumdar, P.; Malaguti, G.; Maltezos, S.;
   Manalaysay, A.; Mancilla, A.; Mandat, D.; Maneva, G.; Mangano, A.;
   Manigot, P.; Mannheim, K.; Manthos, I.; Maragos, N.; Marcowith, A.;
   Mariotti, M.; Marisaldi, M.; Markoff, S.; Marszałek, A.; Martens, C.;
   Martí, J.; Martin, J. -M.; Martin, P.; Martínez, G.; Martínez, F.;
   Martínez, M.; Masserot, A.; Mastichiadis, A.; Mathieu, A.; Matsumoto,
   H.; Mattana, F.; Mattiazzo, S.; Maurin, G.; Maxfield, S.; Maya, J.;
   Mazin, D.; Mc Comb, L.; McCubbin, N.; McHardy, I.; McKay, R.; Medina,
   C.; Melioli, C.; Melkumyan, D.; Mereghetti, S.; Mertsch, P.; Meucci,
   M.; Michałowski, J.; Micolon, P.; Mihailidis, A.; Mineo, T.; Minuti,
   M.; Mirabal, N.; Mirabel, F.; Miranda, J. M.; Mirzoyan, R.; Mizuno,
   T.; Moal, B.; Moderski, R.; Mognet, I.; Molinari, E.; Molinaro,
   M.; Montaruli, T.; Monteiro, I.; Moore, P.; Moralejo Olaizola,
   A.; Mordalska, M.; Morello, C.; Mori, K.; Mottez, F.; Moudden, Y.;
   Moulin, E.; Mrusek, I.; Mukherjee, R.; Munar-Adrover, P.; Muraishi,
   H.; Murase, K.; Murphy, A.; Nagataki, S.; Naito, T.; Nakajima, D.;
   Nakamori, T.; Nakayama, K.; Naumann, C.; Naumann, D.; Naumann-Godo,
   M.; Nayman, P.; Nedbal, D.; Neise, D.; Nellen, L.; Neustroev, V.;
   Neyroud, N.; Nicastro, L.; Nicolau-Kukliński, J.; Niedźwiecki, A.;
   Niemiec, J.; Nieto, D.; Nikolaidis, A.; Nishijima, K.; Nolan, S.;
   Northrop, R.; Nosek, D.; Nowak, N.; Nozato, A.; O'Brien, P.; Ohira,
   Y.; Ohishi, M.; Ohm, S.; Ohoka, H.; Okuda, T.; Okumura, A.; Olive,
   J. -F.; Ong, R. A.; Orito, R.; Orr, M.; Osborne, J.; Ostrowski, M.;
   Otero, L. A.; Otte, N.; Ovcharov, E.; Oya, I.; Ozieblo, A.; Padilla,
   L.; Paiano, S.; Paillot, D.; Paizis, A.; Palanque, S.; Palatka, M.;
   Pallota, J.; Panagiotidis, K.; Panazol, J. -L.; Paneque, D.; Panter,
   M.; Paoletti, R.; Papayannis, A.; Papyan, G.; Paredes, J. M.; Pareschi,
   G.; Parks, G.; Parraud, J. -M.; Parsons, D.; Paz Arribas, M.; Pech,
   M.; Pedaletti, G.; Pelassa, V.; Pelat, D.; Perez, M. d. C.; Persic,
   M.; Petrucci, P. -O.; Peyaud, B.; Pichel, A.; Pita, S.; Pizzolato, F.;
   Platos, Ł.; Platzer, R.; Pogosyan, L.; Pohl, M.; Pojmanski, G.; Ponz,
   J. D.; Potter, W.; Poutanen, J.; Prandini, E.; Prast, J.; Preece, R.;
   Profeti, F.; Prokoph, H.; Prouza, M.; Proyetti, M.; Puerto-Gimenez, I.;
   Pühlhofer, G.; Puljak, I.; Punch, M.; Pyzioł, R.; Quel, E. J.; Quinn,
   J.; Quirrenbach, A.; Racero, E.; Rajda, P. J.; Ramon, P.; Rando, R.;
   Rannot, R. C.; Rataj, M.; Raue, M.; Reardon, P.; Reimann, O.; Reimer,
   A.; Reimer, O.; Reitberger, K.; Renaud, M.; Renner, S.; Reville, B.;
   Rhode, W.; Ribó, M.; Ribordy, M.; Richer, M. G.; Rico, J.; Ridky,
   J.; Rieger, F.; Ringegni, P.; Ripken, J.; Ristori, P. R.; Riviére,
   A.; Rivoire, S.; Rob, L.; Roeser, U.; Rohlfs, R.; Rojas, G.; Romano,
   P.; Romaszkan, W.; Romero, G. E.; Rosen, S.; Rosier Lees, S.; Ross,
   D.; Rouaix, G.; Rousselle, J.; Rousselle, S.; Rovero, A. C.; Roy,
   F.; Royer, S.; Rudak, B.; Rulten, C.; Rupiński, M.; Russo, F.; Ryde,
   F.; Sacco, B.; Saemann, E. O.; Saggion, A.; Sahakian, V.; Saito, K.;
   Saito, T.; Saito, Y.; Sakaki, N.; Sakonaka, R.; Salini, A.; Sanchez,
   F.; Sanchez-Conde, M.; Sandoval, A.; Sandaker, H.; Sant'Ambrogio,
   E.; Santangelo, A.; Santos, E. M.; Sanuy, A.; Sapozhnikov, L.;
   Sarkar, S.; Sartore, N.; Sasaki, H.; Satalecka, K.; Sawada, M.;
   Scalzotto, V.; Scapin, V.; Scarcioffolo, M.; Schafer, J.; Schanz,
   T.; Schlenstedt, S.; Schlickeiser, R.; Schmidt, T.; Schmoll, J.;
   Schovanek, P.; Schroedter, M.; Schultz, C.; Schultze, J.; Schulz,
   A.; Schure, K.; Schwab, T.; Schwanke, U.; Schwarz, J.; Schwarzburg,
   S.; Schweizer, T.; Schwemmer, S.; Segreto, A.; Seiradakis, J. -H.;
   Sembroski, G. H.; Seweryn, K.; Sharma, M.; Shayduk, M.; Shellard,
   R. C.; Shi, J.; Shibata, T.; Shibuya, A.; Shum, E.; Sidoli, L.; Sidz,
   M.; Sieiro, J.; Sikora, M.; Silk, J.; Sillanpää, A.; Singh, B. B.;
   Sitarek, J.; Skole, C.; Smareglia, R.; Smith, A.; Smith, D.; Smith,
   J.; Smith, N.; Sobczyńska, D.; Sol, H.; Sottile, G.; Sowiński, M.;
   Spanier, F.; Spiga, D.; Spyrou, S.; Stamatescu, V.; Stamerra, A.;
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   S.; Stergioulas, N.; Sternberger, R.; Sterzel, M.; Stinzing, F.;
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   Tibaldo, L.; Tibolla, O.; Tiengo, A.; Tluczykont, M.; Todero Peixoto,
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   M.; Torres, D. F.; Torres, M.; Tosti, G.; Totani, T.; Toussenel, F.;
   Tovmassian, G.; Travnicek, P.; Trifoglio, M.; Troyano, I.; Tsinganos,
   K.; Ueno, H.; Umehara, K.; Upadhya, S. S.; Usher, T.; Uslenghi, M.;
   Valdes-Galicia, J. F.; Vallania, P.; Vallejo, G.; van Driel, W.; van
   Eldik, C.; Vandenbrouke, J.; Vanderwalt, J.; Vankov, H.; Vasileiadis,
   G.; Vassiliev, V.; Veberic, D.; Vegas, I.; Vercellone, S.; Vergani,
   S.; Veyssiére, C.; Vialle, J. P.; Viana, A.; Videla, M.; Vincent, P.;
   Vincent, S.; Vink, J.; Vlahakis, N.; Vlahos, L.; Vogler, P.; Vollhardt,
   A.; von Gunten, H. -P.; Vorobiov, S.; Vuerli, C.; Waegebaert, V.;
   Wagner, R.; Wagner, R. G.; Wagner, S.; Wakely, S. P.; Walter, R.;
   Walther, T.; Warda, K.; Warwick, R.; Wawer, P.; Wawrzaszek, R.; Webb,
   N.; Wegner, P.; Weinstein, A.; Weitzel, Q.; Welsing, R.; Werner, M.;
   Wetteskind, H.; White, R.; Wierzcholska, A.; Wiesand, S.; Wilkinson,
   M.; Williams, D. A.; Willingale, R.; Winiarski, K.; Wischnewski, R.;
   Wiśniewski, Ł.; Wood, M.; Wörnlein, A.; Xiong, Q.; Yadav, K. K.;
   Yamamoto, H.; Yamamoto, T.; Yamazaki, R.; Yanagita, S.; Yebras,
   J. M.; Yelos, D.; Yoshida, A.; Yoshida, T.; Yoshikoshi, T.; Zabalza,
   V.; Zacharias, M.; Zajczyk, A.; Zanin, R.; Zdziarski, A.; Zech, A.;
   Zhao, A.; Zhou, X.; Ziętara, K.; Ziolkowski, J.; Ziółkowski, P.;
   Zitelli, V.; Zurbach, C.; Żychowski, P.; CTA Consortium
Bibcode: 2013APh....43....3A
Altcode: 2013APh....43....3C
  The Cherenkov Telescope Array (CTA) is a new observatory for very
  high-energy (VHE) gamma rays. CTA has ambitions science goals, for which
  it is necessary to achieve full-sky coverage, to improve the sensitivity
  by about an order of magnitude, to span about four decades of energy,
  from a few tens of GeV to above 100 TeV with enhanced angular and energy
  resolutions over existing VHE gamma-ray observatories. An international
  collaboration has formed with more than 1000 members from 27 countries
  in Europe, Asia, Africa and North and South America. In 2010 the CTA
  Consortium completed a Design Study and started a three-year Preparatory
  Phase which leads to production readiness of CTA in 2014. In this paper
  we introduce the science goals and the concept of CTA, and provide an
  overview of the project.

Title: Current Fragmentation and Particle Acceleration in Solar Flares
Authors: Cargill, P. J.; Vlahos, L.; Baumann, G.; Drake, J. F.;
   Nordlund, Å.
Bibcode: 2013pacp.book..223C
Altcode:
  No abstract at ADS

Title: Turbulence, Magnetic Reconnection in Turbulent Fluids and
    Energetic Particle Acceleration
Authors: Lazarian, A.; Vlahos, L.; Kowal, G.; Yan, H.; Beresnyak,
   A.; de Gouveia Dal Pino, E. M.
Bibcode: 2013pacp.book..557L
Altcode:
  No abstract at ADS

Title: Current Fragmentation and Particle Acceleration in Solar Flares
Authors: Cargill, P. J.; Vlahos, L.; Baumann, G.; Drake, J. F.;
   Nordlund, Å.
Bibcode: 2012SSRv..173..223C
Altcode: 2012SSRv..tmp...36C
  Particle acceleration in solar flares remains an outstanding problem in
  plasma physics and space science. While the observed particle energies
  and timescales can perhaps be understood in terms of acceleration
  at a simple current sheet or turbulence site, the vast number of
  accelerated particles, and the fraction of flare energy in them, defies
  any simple explanation. The nature of energy storage and dissipation
  in the global coronal magnetic field is essential for understanding
  flare acceleration. Scenarios where the coronal field is stressed by
  complex photospheric motions lead to the formation of multiple current
  sheets, rather than the single monolithic current sheet proposed by
  some. The currents sheets in turn can fragment into multiple, smaller
  dissipation sites. MHD, kinetic and cellular automata models are used to
  demonstrate this feature. Particle acceleration in this environment thus
  involves interaction with many distributed accelerators. A series of
  examples demonstrate how acceleration works in such an environment. As
  required, acceleration is fast, and relativistic energies are readily
  attained. It is also shown that accelerated particles do indeed
  interact with multiple acceleration sites. Test particle models also
  demonstrate that a large number of particles can be accelerated, with a
  significant fraction of the flare energy associated with them. However,
  in the absence of feedback, and with limited numerical resolution,
  these results need to be viewed with caution. Particle in cell models
  can incorporate feedback and in one scenario suggest that acceleration
  can be limited by the energetic particles reaching the condition for
  firehose marginal stability. Contemporary issues such as footpoint
  particle acceleration are also discussed. It is also noted that the
  idea of a "standard flare model" is ill-conceived when the entire
  distribution of flare energies is considered.

Title: Turbulence, Magnetic Reconnection in Turbulent Fluids and
    Energetic Particle Acceleration
Authors: Lazarian, A.; Vlahos, L.; Kowal, G.; Yan, H.; Beresnyak,
   A.; de Gouveia Dal Pino, E. M.
Bibcode: 2012SSRv..173..557L
Altcode: 2012SSRv..tmp...90L; 2012SSRv..tmp...86L; 2012arXiv1211.0008L
  Turbulence is ubiquitous in astrophysics. It radically changes
  many astrophysical phenomena, in particular, the propagation and
  acceleration of cosmic rays. We present the modern understanding of
  compressible magnetohydrodynamic (MHD) turbulence, in particular its
  decomposition into Alfvén, slow and fast modes, discuss the density
  structure of turbulent subsonic and supersonic media, as well as other
  relevant regimes of astrophysical turbulence. All this information is
  essential for understanding the energetic particle acceleration that we
  discuss further in the review. For instance, we show how fast and slow
  modes accelerate energetic particles through the second order Fermi
  acceleration, while density fluctuations generate magnetic fields
  in pre-shock regions enabling the first order Fermi acceleration of
  high energy cosmic rays. Very importantly, however, the first order
  Fermi cosmic ray acceleration is also possible in sites of magnetic
  reconnection. In the presence of turbulence this reconnection gets
  fast and we present numerical evidence supporting the predictions of
  the Lazarian and Vishniac (Astrophys. J. 517:700-718, 1999) model of
  fast reconnection. The efficiency of this process suggests that magnetic
  reconnection can release substantial amounts of energy in short periods
  of time. As the particle tracing numerical simulations show that the
  particles can be efficiently accelerated during the reconnection,
  we argue that the process of magnetic reconnection may be much more
  important for particle acceleration than it is currently accepted. In
  particular, we discuss the acceleration arising from reconnection as
  a possible origin of the anomalous cosmic rays measured by Voyagers
  as well as the origin cosmic ray excess in the direction of Heliotail.

Title: Design concepts for the Cherenkov Telescope Array CTA: an
    advanced facility for ground-based high-energy gamma-ray astronomy
Authors: Actis, M.; Agnetta, G.; Aharonian, F.; Akhperjanian,
   A.; Aleksić, J.; Aliu, E.; Allan, D.; Allekotte, I.; Antico, F.;
   Antonelli, L. A.; Antoranz, P.; Aravantinos, A.; Arlen, T.; Arnaldi,
   H.; Artmann, S.; Asano, K.; Asorey, H.; Bähr, J.; Bais, A.; Baixeras,
   C.; Bajtlik, S.; Balis, D.; Bamba, A.; Barbier, C.; Barceló, M.;
   Barnacka, A.; Barnstedt, J.; Barres de Almeida, U.; Barrio, J. A.;
   Basso, S.; Bastieri, D.; Bauer, C.; Becerra, J.; Becherini, Y.;
   Bechtol, K.; Becker, J.; Beckmann, V.; Bednarek, W.; Behera, B.;
   Beilicke, M.; Belluso, M.; Benallou, M.; Benbow, W.; Berdugo, J.;
   Berger, K.; Bernardino, T.; Bernlöhr, K.; Biland, A.; Billotta, S.;
   Bird, T.; Birsin, E.; Bissaldi, E.; Blake, S.; Blanch, O.; Bobkov,
   A. A.; Bogacz, L.; Bogdan, M.; Boisson, C.; Boix, J.; Bolmont,
   J.; Bonanno, G.; Bonardi, A.; Bonev, T.; Borkowski, J.; Botner, O.;
   Bottani, A.; Bourgeat, M.; Boutonnet, C.; Bouvier, A.; Brau-Nogué, S.;
   Braun, I.; Bretz, T.; Briggs, M. S.; Brun, P.; Brunetti, L.; Buckley,
   J. H.; Bugaev, V.; Bühler, R.; Bulik, T.; Busetto, G.; Buson, S.;
   Byrum, K.; Cailles, M.; Cameron, R.; Canestrari, R.; Cantu, S.;
   Carmona, E.; Carosi, A.; Carr, J.; Carton, P. H.; Casiraghi, M.;
   Castarede, H.; Catalano, O.; Cavazzani, S.; Cazaux, S.; Cerruti,
   B.; Cerruti, M.; Chadwick, P. M.; Chiang, J.; Chikawa, M.; Cieślar,
   M.; Ciesielska, M.; Cillis, A.; Clerc, C.; Colin, P.; Colomé, J.;
   Compin, M.; Conconi, P.; Connaughton, V.; Conrad, J.; Contreras, J. L.;
   Coppi, P.; Corlier, M.; Corona, P.; Corpace, O.; Corti, D.; Cortina,
   J.; Costantini, H.; Cotter, G.; Courty, B.; Couturier, S.; Covino,
   S.; Croston, J.; Cusumano, G.; Daniel, M. K.; Dazzi, F.; de Angelis,
   A.; de Cea Del Pozo, E.; de Gouveia Dal Pino, E. M.; de Jager, O.;
   de La Calle Pérez, I.; de La Vega, G.; de Lotto, B.; de Naurois,
   M.; de Oña Wilhelmi, E.; de Souza, V.; Decerprit, B.; Deil, C.;
   Delagnes, E.; Deleglise, G.; Delgado, C.; Dettlaff, T.; di Paolo,
   A.; di Pierro, F.; Díaz, C.; Dick, J.; Dickinson, H.; Digel, S. W.;
   Dimitrov, D.; Disset, G.; Djannati-Ataï, A.; Doert, M.; Domainko,
   W.; Dorner, D.; Doro, M.; Dournaux, J. -L.; Dravins, D.; Drury, L.;
   Dubois, F.; Dubois, R.; Dubus, G.; Dufour, C.; Durand, D.; Dyks,
   J.; Dyrda, M.; Edy, E.; Egberts, K.; Eleftheriadis, C.; Elles, S.;
   Emmanoulopoulos, D.; Enomoto, R.; Ernenwein, J. -P.; Errando, M.;
   Etchegoyen, A.; Falcone, A. D.; Farakos, K.; Farnier, C.; Federici,
   S.; Feinstein, F.; Ferenc, D.; Fillin-Martino, E.; Fink, D.; Finley,
   C.; Finley, J. P.; Firpo, R.; Florin, D.; Föhr, C.; Fokitis, E.;
   Font, Ll.; Fontaine, G.; Fontana, A.; Förster, A.; Fortson, L.;
   Fouque, N.; Fransson, C.; Fraser, G. W.; Fresnillo, L.; Fruck, C.;
   Fujita, Y.; Fukazawa, Y.; Funk, S.; Gäbele, W.; Gabici, S.; Gadola,
   A.; Galante, N.; Gallant, Y.; García, B.; García López, R. J.;
   Garrido, D.; Garrido, L.; Gascón, D.; Gasq, C.; Gaug, M.; Gaweda,
   J.; Geffroy, N.; Ghag, C.; Ghedina, A.; Ghigo, M.; Gianakaki, E.;
   Giarrusso, S.; Giavitto, G.; Giebels, B.; Giro, E.; Giubilato, P.;
   Glanzman, T.; Glicenstein, J. -F.; Gochna, M.; Golev, V.; Gómez
   Berisso, M.; González, A.; González, F.; Grañena, F.; Graciani,
   R.; Granot, J.; Gredig, R.; Green, A.; Greenshaw, T.; Grimm, O.;
   Grube, J.; Grudzińska, M.; Grygorczuk, J.; Guarino, V.; Guglielmi,
   L.; Guilloux, F.; Gunji, S.; Gyuk, G.; Hadasch, D.; Haefner, D.;
   Hagiwara, R.; Hahn, J.; Hallgren, A.; Hara, S.; Hardcastle, M. J.;
   Hassan, T.; Haubold, T.; Hauser, M.; Hayashida, M.; Heller, R.; Henri,
   G.; Hermann, G.; Herrero, A.; Hinton, J. A.; Hoffmann, D.; Hofmann,
   W.; Hofverberg, P.; Horns, D.; Hrupec, D.; Huan, H.; Huber, B.; Huet,
   J. -M.; Hughes, G.; Hultquist, K.; Humensky, T. B.; Huppert, J. -F.;
   Ibarra, A.; Illa, J. M.; Ingjald, J.; Inoue, Y.; Inoue, S.; Ioka, K.;
   Jablonski, C.; Jacholkowska, A.; Janiak, M.; Jean, P.; Jensen, H.;
   Jogler, T.; Jung, I.; Kaaret, P.; Kabuki, S.; Kakuwa, J.; Kalkuhl,
   C.; Kankanyan, R.; Kapala, M.; Karastergiou, A.; Karczewski, M.;
   Karkar, S.; Karlsson, N.; Kasperek, J.; Katagiri, H.; Katarzyński, K.;
   Kawanaka, N.; Kȩdziora, B.; Kendziorra, E.; Khélifi, B.; Kieda, D.;
   Kifune, T.; Kihm, T.; Klepser, S.; Kluźniak, W.; Knapp, J.; Knappy,
   A. R.; Kneiske, T.; Knödlseder, J.; Köck, F.; Kodani, K.; Kohri,
   K.; Kokkotas, K.; Komin, N.; Konopelko, A.; Kosack, K.; Kossakowski,
   R.; Kostka, P.; Kotuła, J.; Kowal, G.; Kozioł, J.; Krähenbühl,
   T.; Krause, J.; Krawczynski, H.; Krennrich, F.; Kretzschmann, A.;
   Kubo, H.; Kudryavtsev, V. A.; Kushida, J.; La Barbera, N.; La Parola,
   V.; La Rosa, G.; López, A.; Lamanna, G.; Laporte, P.; Lavalley, C.;
   Le Flour, T.; Le Padellec, A.; Lenain, J. -P.; Lessio, L.; Lieunard,
   B.; Lindfors, E.; Liolios, A.; Lohse, T.; Lombardi, S.; Lopatin,
   A.; Lorenz, E.; Lubiński, P.; Luz, O.; Lyard, E.; Maccarone, M. C.;
   Maccarone, T.; Maier, G.; Majumdar, P.; Maltezos, S.; Małkiewicz,
   P.; Mañá, C.; Manalaysay, A.; Maneva, G.; Mangano, A.; Manigot,
   P.; Marín, J.; Mariotti, M.; Markoff, S.; Martínez, G.; Martínez,
   M.; Mastichiadis, A.; Matsumoto, H.; Mattiazzo, S.; Mazin, D.; McComb,
   T. J. L.; McCubbin, N.; McHardy, I.; Medina, C.; Melkumyan, D.; Mendes,
   A.; Mertsch, P.; Meucci, M.; Michałowski, J.; Micolon, P.; Mineo,
   T.; Mirabal, N.; Mirabel, F.; Miranda, J. M.; Mirzoyan, R.; Mizuno,
   T.; Moal, B.; Moderski, R.; Molinari, E.; Monteiro, I.; Moralejo, A.;
   Morello, C.; Mori, K.; Motta, G.; Mottez, F.; Moulin, E.; Mukherjee,
   R.; Munar, P.; Muraishi, H.; Murase, K.; Murphy, A. Stj.; Nagataki,
   S.; Naito, T.; Nakamori, T.; Nakayama, K.; Naumann, C.; Naumann, D.;
   Nayman, P.; Nedbal, D.; Niedźwiecki, A.; Niemiec, J.; Nikolaidis,
   A.; Nishijima, K.; Nolan, S. J.; Nowak, N.; O'Brien, P. T.; Ochoa,
   I.; Ohira, Y.; Ohishi, M.; Ohka, H.; Okumura, A.; Olivetto, C.; Ong,
   R. A.; Orito, R.; Orr, M.; Osborne, J. P.; Ostrowski, M.; Otero, L.;
   Otte, A. N.; Ovcharov, E.; Oya, I.; Oziȩbło, A.; Paiano, S.; Pallota,
   J.; Panazol, J. L.; Paneque, D.; Panter, M.; Paoletti, R.; Papyan,
   G.; Paredes, J. M.; Pareschi, G.; Parsons, R. D.; Paz Arribas, M.;
   Pedaletti, G.; Pepato, A.; Persic, M.; Petrucci, P. O.; Peyaud,
   B.; Piechocki, W.; Pita, S.; Pivato, G.; Płatos, Ł.; Platzer,
   R.; Pogosyan, L.; Pohl, M.; Pojmański, G.; Ponz, J. D.; Potter,
   W.; Prandini, E.; Preece, R.; Prokoph, H.; Pühlhofer, G.; Punch,
   M.; Quel, E.; Quirrenbach, A.; Rajda, P.; Rando, R.; Rataj, M.;
   Raue, M.; Reimann, C.; Reimann, O.; Reimer, A.; Reimer, O.; Renaud,
   M.; Renner, S.; Reymond, J. -M.; Rhode, W.; Ribó, M.; Ribordy,
   M.; Rico, J.; Rieger, F.; Ringegni, P.; Ripken, J.; Ristori, P.;
   Rivoire, S.; Rob, L.; Rodriguez, S.; Roeser, U.; Romano, P.; Romero,
   G. E.; Rosier-Lees, S.; Rovero, A. C.; Roy, F.; Royer, S.; Rudak, B.;
   Rulten, C. B.; Ruppel, J.; Russo, F.; Ryde, F.; Sacco, B.; Saggion, A.;
   Sahakian, V.; Saito, K.; Saito, T.; Sakaki, N.; Salazar, E.; Salini,
   A.; Sánchez, F.; Sánchez Conde, M. Á.; Santangelo, A.; Santos,
   E. M.; Sanuy, A.; Sapozhnikov, L.; Sarkar, S.; Scalzotto, V.; Scapin,
   V.; Scarcioffolo, M.; Schanz, T.; Schlenstedt, S.; Schlickeiser, R.;
   Schmidt, T.; Schmoll, J.; Schroedter, M.; Schultz, C.; Schultze, J.;
   Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schweizer, T.; Seiradakis,
   J.; Selmane, S.; Seweryn, K.; Shayduk, M.; Shellard, R. C.; Shibata,
   T.; Sikora, M.; Silk, J.; Sillanpää, A.; Sitarek, J.; Skole, C.;
   Smith, N.; Sobczyńska, D.; Sofo Haro, M.; Sol, H.; Spanier, F.; Spiga,
   D.; Spyrou, S.; Stamatescu, V.; Stamerra, A.; Starling, R. L. C.;
   Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Steiner, S.; Stergioulas,
   N.; Sternberger, R.; Stinzing, F.; Stodulski, M.; Straumann, U.;
   Suárez, A.; Suchenek, M.; Sugawara, R.; Sulanke, K. H.; Sun, S.;
   Supanitsky, A. D.; Sutcliffe, P.; Szanecki, M.; Szepieniec, T.;
   Szostek, A.; Szymkowiak, A.; Tagliaferri, G.; Tajima, H.; Takahashi,
   H.; Takahashi, K.; Takalo, L.; Takami, H.; Talbot, R. G.; Tam, P. H.;
   Tanaka, M.; Tanimori, T.; Tavani, M.; Tavernet, J. -P.; Tchernin, C.;
   Tejedor, L. A.; Telezhinsky, I.; Temnikov, P.; Tenzer, C.; Terada,
   Y.; Terrier, R.; Teshima, M.; Testa, V.; Tibaldo, L.; Tibolla, O.;
   Tluczykont, M.; Todero Peixoto, C. J.; Tokanai, F.; Tokarz, M.; Toma,
   K.; Torres, D. F.; Tosti, G.; Totani, T.; Toussenel, F.; Vallania,
   P.; Vallejo, G.; van der Walt, J.; van Eldik, C.; Vandenbroucke, J.;
   Vankov, H.; Vasileiadis, G.; Vassiliev, V. V.; Vegas, I.; Venter, L.;
   Vercellone, S.; Veyssiere, C.; Vialle, J. P.; Videla, M.; Vincent,
   P.; Vink, J.; Vlahakis, N.; Vlahos, L.; Vogler, P.; Vollhardt, A.;
   Volpe, F.; von Gunten, H. P.; Vorobiov, S.; Wagner, S.; Wagner,
   R. M.; Wagner, B.; Wakely, S. P.; Walter, P.; Walter, R.; Warwick,
   R.; Wawer, P.; Wawrzaszek, R.; Webb, N.; Wegner, P.; Weinstein, A.;
   Weitzel, Q.; Welsing, R.; Wetteskind, H.; White, R.; Wierzcholska,
   A.; Wilkinson, M. I.; Williams, D. A.; Winde, M.; Wischnewski, R.;
   Wiśniewski, Ł.; Wolczko, A.; Wood, M.; Xiong, Q.; Yamamoto, T.;
   Yamaoka, K.; Yamazaki, R.; Yanagita, S.; Yoffo, B.; Yonetani, M.;
   Yoshida, A.; Yoshida, T.; Yoshikoshi, T.; Zabalza, V.; Zagdański,
   A.; Zajczyk, A.; Zdziarski, A.; Zech, A.; Ziȩtara, K.; Ziółkowski,
   P.; Zitelli, V.; Zychowski, P.
Bibcode: 2011ExA....32..193A
Altcode: 2011ExA...tmp..121A; 2010arXiv1008.3703C
  Ground-based gamma-ray astronomy has had a major breakthrough with
  the impressive results obtained using systems of imaging atmospheric
  Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge
  potential in astrophysics, particle physics and cosmology. CTA is
  an international initiative to build the next generation instrument,
  with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV
  range and the extension to energies well below 100 GeV and above 100
  TeV. CTA will consist of two arrays (one in the north, one in the south)
  for full sky coverage and will be operated as open observatory. The
  design of CTA is based on currently available technology. This document
  reports on the status and presents the major design concepts of CTA.

Title: Recent Advances in Understanding Particle Acceleration
    Processes in Solar Flares
Authors: Zharkova, V. V.; Arzner, K.; Benz, A. O.; Browning, P.;
   Dauphin, C.; Emslie, A. G.; Fletcher, L.; Kontar, E. P.; Mann, G.;
   Onofri, M.; Petrosian, V.; Turkmani, R.; Vilmer, N.; Vlahos, L.
Bibcode: 2011SSRv..159..357Z
Altcode: 2011SSRv..tmp..156Z; 2011SSRv..tmp..249Z; 2011SSRv..tmp..232Z;
   2011arXiv1110.2359Z; 2011SSRv..tmp..278Z
  We review basic theoretical concepts in particle acceleration,
  with particular emphasis on processes likely to occur in regions of
  magnetic reconnection. Several new developments are discussed, including
  detailed studies of reconnection in three-dimensional magnetic field
  configurations (e.g., current sheets, collapsing traps, separatrix
  regions) and stochastic acceleration in a turbulent environment. Fluid,
  test-particle, and particle-in-cell approaches are used and results
  compared. While these studies show considerable promise in accounting
  for the various observational manifestations of solar flares, they
  are limited by a number of factors, mostly relating to available
  computational power. Not the least of these issues is the need to
  explicitly incorporate the electrodynamic feedback of the accelerated
  particles themselves on the environment in which they are accelerated. A
  brief prognosis for future advancement is offered.

Title: Simulating flaring events in complex active regions driven
    by observed magnetograms
Authors: Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M. K.
Bibcode: 2011A&A...529A.101D
Altcode: 2011arXiv1102.2352D
  Context. We interpret solar flares as events originating in active
  regions that have reached the self organized critical state, by using
  a refined cellular automaton model with initial conditions derived
  from observations. <BR /> Aims: We investigate whether the system,
  with its imposed physical elements, reaches a self organized critical
  state and whether well-known statistical properties of flares,
  such as scaling laws observed in the distribution functions of
  characteristic parameters, are reproduced after this state has been
  reached. <BR /> Methods: To investigate whether the distribution
  functions of total energy, peak energy and event duration follow
  the expected scaling laws, we first applied a nonlinear force-free
  extrapolation that reconstructs the three-dimensional magnetic
  fields from two-dimensional vector magnetograms. We then locate
  magnetic discontinuities exceeding a threshold in the Laplacian of the
  magnetic field. These discontinuities are relaxed in local diffusion
  events, implemented in the form of cellular automaton evolution
  rules. Subsequent loading and relaxation steps lead the system to
  self organized criticality, after which the statistical properties
  of the simulated events are examined. Physical requirements, such
  as the divergence-free condition for the magnetic field vector, are
  approximately imposed on all elements of the model. <BR /> Results:
  Our results show that self organized criticality is indeed reached
  when applying specific loading and relaxation rules. Power-law indices
  obtained from the distribution functions of the modeled flaring events
  are in good agreement with observations. Single power laws (peak and
  total flare energy) are obtained, as are power laws with exponential
  cutoff and double power laws (flare duration). The results are also
  compared with observational X-ray data from the GOES satellite for our
  active-region sample. <BR /> Conclusions: We conclude that well-known
  statistical properties of flares are reproduced after the system
  has reached self organized criticality. A significant enhancement
  of our refined cellular automaton model is that it commences the
  simulation from observed vector magnetograms, thus facilitating
  energy calculation in physical units. The model described in this
  study remains consistent with fundamental physical requirements,
  and imposes physically meaningful driving and redistribution rules.

Title: Simulating Flaring Events via an Intelligent Cellular Automata
    Mechanism
Authors: Dimitropoulou, M.; Vlahos, L.; Isliker, H.; Georgoulis, M.
Bibcode: 2010ASPC..424...28D
Altcode:
  We simulate flaring events through a Cellular Automaton (CA) model,
  in which, for the first time, we use observed vector magnetograms as
  initial conditions. After non-linear force free extrapolation of the
  magnetic field from the vector magnetograms, we identify magnetic
  discontinuities, using two alternative criteria: (1) the average
  magnetic field gradient, or (2) the normalized magnetic field curl
  (i.e. the current). Magnetic discontinuities are identified at the
  grid-sites where the magnetic field gradient or curl exceeds a specified
  threshold. We then relax the magnetic discontinuities according to
  the rules of Lu and Hamilton (1991) or Lu et al. (1993), i.e. we
  redistribute the magnetic field locally so that the discontinuities
  disappear. In order to simulate the flaring events, we consider
  several alternative scenarios with regard to: (1) The threshold
  above which magnetic discontinuities are identified (applying low,
  high, and height-dependent threshold values); (2) The driving process
  that occasionally causes new discontinuities (at randomly chosen grid
  sites, magnetic field increments are added that are perpendicular (or
  may-be also parallel) to the existing magnetic field). We address the
  question whether the coronal active region magnetic fields can indeed
  be considered to be in the state of self-organized criticality (SOC).

Title: Local re-acceleration and a modified thick target model of
    solar flare electrons
Authors: Brown, J. C.; Turkmani, R.; Kontar, E. P.; MacKinnon, A. L.;
   Vlahos, L.
Bibcode: 2009A&A...508..993B
Altcode: 2009arXiv0909.4243B
  Context: The collisional thick target model (CTTM) of solar hard
  X-ray (HXR) bursts has become an almost “standard model” of
  flare impulsive phase energy transport and radiation. However, it
  faces various problems in the light of recent data, particularly the
  high electron beam density and anisotropy it involves.<BR /> Aims: We
  consider how photon yield per electron can be increased, and hence fast
  electron beam intensity requirements reduced, by local re-acceleration
  of fast electrons throughout the HXR source itself, after injection.<BR
  /> Methods: We show parametrically that, if net re-acceleration rates
  due to e.g. waves or local current sheet electric (E) fields are a
  significant fraction of collisional loss rates, electron lifetimes, and
  hence the net radiative HXR output per electron can be substantially
  increased over the CTTM values. In this local re-acceleration thick
  target model (LRTTM) fast electron number requirements and anisotropy
  are thus reduced. One specific possible scenario involving such
  re-acceleration is discussed, viz, a current sheet cascade (CSC) in a
  randomly stressed magnetic loop.<BR /> Results: Combined MHD and test
  particle simulations show that local E fields in CSCs can efficiently
  accelerate electrons in the corona and and re-accelerate them after
  injection into the chromosphere. In this HXR source scenario, rapid
  synchronisation and variability of impulsive footpoint emissions can
  still occur since primary electron acceleration is in the high Alfvén
  speed corona with fast re-acceleration in chromospheric CSCs. It is
  also consistent with the energy-dependent time-of-flight delays in
  HXR features.<BR /> Conclusions: Including electron re-acceleration in
  the HXR source allows an LRTTM modification of the CTTM in which beam
  density and anisotropy are much reduced, and alleviates theoretical
  problems with the CTTM, while making it more compatible with radio and
  interplanetary electron numbers. The LRTTM is, however, different in
  some respects such as spatial distribution of atmospheric heating by
  fast electrons.

Title: The correlation of fractal structures in the photospheric
    and the coronal magnetic field
Authors: Dimitropoulou, M.; Georgoulis, M.; Isliker, H.; Vlahos, L.;
   Anastasiadis, A.; Strintzi, D.; Moussas, X.
Bibcode: 2009A&A...505.1245D
Altcode: 2009arXiv0908.3950D
  Context: This work examines the relation between the fractal properties
  of the photospheric magnetic patterns and those of the coronal
  magnetic fields in solar active regions. <BR />Aims: We investigate
  whether there is any correlation between the fractal dimensions of
  the photospheric structures and the magnetic discontinuities formed in
  the corona. <BR />Methods: To investigate the connection between the
  photospheric and coronal complexity, we used a nonlinear force-free
  extrapolation method that reconstructs the 3d magnetic fields using 2d
  observed vector magnetograms as boundary conditions. We then located
  the magnetic discontinuities, which are considered as spatial proxies
  of reconnection-related instabilities. These discontinuities form
  well-defined volumes, called here unstable volumes. We calculated
  the fractal dimensions of these unstable volumes and compared them
  to the fractal dimensions of the boundary vector magnetograms. <BR
  />Results: Our results show no correlation between the fractal
  dimensions of the observed 2d photospheric structures and the
  extrapolated unstable volumes in the corona, when nonlinear force-free
  extrapolation is used. This result is independent of efforts to
  (1) bring the photospheric magnetic fields closer to a nonlinear
  force-free equilibrium and (2) omit the lower part of the modeled
  magnetic field volume that is almost completely filled by unstable
  volumes. A significant correlation between the fractal dimensions of
  the photospheric and coronal magnetic features is only observed at the
  zero level (lower limit) of approximation of a current-free (potential)
  magnetic field extrapolation. <BR />Conclusions: We conclude that
  the complicated transition from photospheric non-force-free fields
  to coronal force-free ones hampers any direct correlation between
  the fractal dimensions of the 2d photospheric patterns and their
  3d counterparts in the corona at the nonlinear force-free limit,
  which can be considered as a second level of approximation in this
  study. Correspondingly, in the zero and first levels of approximation,
  namely, the potential and linear force-free extrapolation, respectively,
  we reveal a significant correlation between the fractal dimensions of
  the photospheric and coronal structures, which can be attributed to the
  lack of electric currents or to their purely field-aligned orientation.

Title: The Solar Flare: A Strongly Turbulent Particle Accelerator
Authors: Vlahos, L.; Krucker, S.; Cargill, P.
Bibcode: 2009LNP...778..157V
Altcode:
  The topics of explosive magnetic energy release on a large scale
  (a solar flare) and particle acceleration during such an event are
  rarely discussed together in the same article. Many discussions of
  magnetohydrodynamic (MHD) mod- eling of solar flares and/or CMEs
  have appeared (see [143] and references therein) and usually address
  large-scale destabilization of the coronal mag- netic field. Particle
  acceleration in solar flares has also been discussed exten- sively
  [74, 164, 116, 166, 87, 168, 95, 122, 35] with the main emphasis being
  on the actual mechanisms for acceleration (e.g., shocks, turbulence,
  DC electric fields) rather than the global magnetic context in which
  the acceleration takes place.

Title: Solar and Stellar Active Regions
Authors: Vlahos, Loukas
Bibcode: 2009ASSP....8..423V
Altcode: 2009chas.book..423V
  No abstract at ADS

Title: Turbulence in Space Plasmas by Peter Cargill, Loukas
Vlahos. Lecture Notes in Physics, Vol. 778. Berlin: Springer, 2009.
Authors: Cargill, Peter; Vlahos, Loukas
Bibcode: 2009LNP...778.....C
Altcode:
  No abstract at ADS

Title: Hard X-ray emission from the solar corona
Authors: Krucker, S.; Battaglia, M.; Cargill, P. J.; Fletcher, L.;
   Hudson, H. S.; MacKinnon, A. L.; Masuda, S.; Sui, L.; Tomczak, M.;
   Veronig, A. L.; Vlahos, L.; White, S. M.
Bibcode: 2008A&ARv..16..155K
Altcode: 2008A&ARv.tmp....8K
  This review surveys hard X-ray emissions of non-thermal electrons in the
  solar corona. These electrons originate in flares and flare-related
  processes. Hard X-ray emission is the most direct diagnostic of
  electron presence in the corona, and such observations provide
  quantitative determinations of the total energy in the non-thermal
  electrons. The most intense flare emissions are generally observed
  from the chromosphere at footpoints of magnetic loops. Over the years,
  however, many observations of hard X-ray and even γ-ray emission
  directly from the corona have also been reported. These coronal sources
  are of particular interest as they occur closest to where the electron
  acceleration is thought to occur. Prior to the actual direct imaging
  observations, disk occultation was usually required to study coronal
  sources, resulting in limited physical information. Now RHESSI has
  given us a systematic view of coronal sources that combines high
  spatial and spectral resolution with broad energy coverage and high
  sensitivity. Despite the low density and hence low bremsstrahlung
  efficiency of the corona, we now detect coronal hard X-ray emissions
  from sources in all phases of solar flares. Because the physical
  conditions in such sources may differ substantially from those of
  the usual “footpoint” emission regions, we take the opportunity
  to revisit the physics of hard X-radiation and relevant theories of
  particle acceleration.

Title: Imprints of cosmic strings on the cosmological gravitational
    wave background
Authors: Kleidis, K.; Papadopoulos, D. B.; Verdaguer, E.; Vlahos, L.
Bibcode: 2008PhRvD..78b4027K
Altcode: 2008arXiv0806.2999K
  The equation which governs the temporal evolution of a gravitational
  wave (GW) in curved space-time can be treated as the Schrödinger
  equation for a particle moving in the presence of an effective
  potential. When GWs propagate in an expanding universe with constant
  effective potential, there is a critical value (k<SUB>c</SUB>) of the
  comoving wave number which discriminates the metric perturbations into
  oscillating (k&gt;k<SUB>c</SUB>) and nonoscillating (k&lt;k<SUB>c</SUB>)
  modes. As a consequence, if the nonoscillatory modes are outside the
  horizon they do not freeze out. The effective potential is reduced
  to a nonvanishing constant in a cosmological model which is driven
  by a two-component fluid, consisting of radiation (dominant) and
  cosmic strings (subdominant). It is known that the cosmological
  evolution gradually results in the scaling of a cosmic-string
  network and, therefore, after some time (Δτ) the Universe becomes
  radiation dominated. The evolution of the nonoscillatory GW modes
  during Δτ (while they were outside the horizon), results in the
  distortion of the GW power spectrum from what it is anticipated in
  a pure radiation model, at present-time frequencies in the range
  10<SUP>-16</SUP>Hz&lt;f≲10<SUP>5</SUP>Hz.

Title: Solar and Stellar Active Regions:Cosmic laboratories for the
    study of Complexity
Authors: Vlahos, Loukas
Bibcode: 2008arXiv0803.3158V
Altcode:
  Solar active regions are driven dissipative dynamical systems. The
  turbulent convection zone forces new magnetic flux tubes to rise
  above the photosphere and shuffles the magnetic fields which are
  already above the photosphere. The driven 3D active region responds
  to the driver with the formation of Thin Current Sheets in all scales
  and releases impulsively energy, when special thresholds are met,
  on the form of nano-, micro-, flares and large scale coronal mass
  ejections. It has been documented that active regions form self
  similar structures with area Probability Distribution Functions
  (PDF's) following power laws and with fractal dimensions ranging from
  $1.2-1.7$. The energy release on the other hand follows a specific
  energy distribution law $f(E_T)\sim E_T^{-a}$, where $a \sim 1.6-1.8$
  and $E_T$ is the total energy released. A possible explanation for the
  statistical properties of the magnetogrms and the energy release by
  the active region is that the magnetic field formation follows rules
  analogous to \textbf{percolating models}, and the 3D magnetic fields
  above the photosphere reach a \textbf{Self Organized Critical (SOC)
  state}. The implications of these findings on the acceleration of
  energetic particles during impulsive phenomena will briefly be outlined.

Title: Dynamo Effects in Magnetized Ideal Plasma Cosmologies
Authors: Kleidis, Kostas; Kuiroukidis, Apostolos; Papadopoulos,
   Demetrios; Vlahos, Loukas
Bibcode: 2008IJMPA..23.1697K
Altcode: 2007arXiv0712.4239K
  The excitation of cosmological perturbations in an anisotropic
  cosmological model and in the presence of a homogeneous magnetic
  field has been studied, using the ideal magnetohydrodynamic
  (MHD) equations. In this case, the system of partial differential
  equations which governs the evolution of the magnetized cosmological
  perturbations can be solved analytically. Our results verify that
  fast-magnetosonic modes propagating normal to the magnetic field,
  are excited. But, what is most important, is that, at late times, the
  magnetic-induction contrast (δB/B) grows, resulting in the enhancement
  of the ambient magnetic field. This process can be particularly favored
  by condensations, formed within the plasma fluid due to gravitational
  instabilities.

Title: Gravitomagnetic Instabilities in Anisotropically Expanding
    Fluids
Authors: Kleidis, Kostas; Kuiroukidis, Apostolos; Papadopoulos,
   Demetrios B.; Vlahos, Loukas
Bibcode: 2008IJMPA..23.4467K
Altcode: 2008arXiv0806.4362K
  Gravitational instabilities in a magnetized Friedman-Robertson-Walker
  (FRW) universe, in which the magnetic field was assumed to be too
  weak to destroy the isotropy of the model, are known and have been
  studied in the past. Accordingly, it became evident that the external
  magnetic field disfavors the perturbations' growth, suppressing the
  corresponding rate by an amount proportional to its strength. However,
  the spatial isotropy of the FRW universe is not compatible with
  the presence of large-scale magnetic fields. Therefore, in this
  paper we use the general-relativistic version of the (linearized)
  perturbed magnetohydrodynamic equations with and without resistivity,
  to discuss a generalized Jeans criterion and the potential formation of
  density condensations within a class of homogeneous and anisotropically
  expanding, self-gravitating, magnetized fluids in curved space-time. We
  find that, for a wide variety of anisotropic cosmological models,
  gravitomagnetic instabilities can lead to subhorizontal, magnetized
  condensations. In the nonresistive case, the power spectrum of the
  unstable cosmological perturbations suggests that most of the power is
  concentrated on large scales (small k), very close to the horizon. On
  the other hand, in a resistive medium, the critical wave-numbers so
  obtained, exhibit a delicate dependence on resistivity, resulting in
  the reduction of the corresponding Jeans lengths to smaller scales
  (well bellow the horizon) than the nonresistive ones, while increasing
  the range of cosmological models which admit such an instability.

Title: Magnetohydrodynamics and Plasma Cosmology
Authors: Kleidis, Kostas; Kuiroukidis, Apostolos; Papadopoulos,
   Demetrios; Vlahos, Loukas
Bibcode: 2007IJTP...46.2283K
Altcode: 2005gr.qc....12131K; 2007IJTP..tmp..132K; 2007IJTP..tmp..208K
  We study the linear magnetohydrodynamic (MHD) equations, both in the
  Newtonian and the general-relativistic limit, as regards a viscous
  magnetized fluid of finite conductivity and discuss instability
  criteria. In addition, we explore the excitation of cosmological
  perturbations in anisotropic spacetimes, in the presence of an ambient
  magnetic field. Acoustic, electromagnetic (e/m) and fast-magnetosonic
  modes, propagating normal to the magnetic field, can be excited,
  resulting in several implications of cosmological significance.

Title: Summary of Joint Discussion 1
Authors: Vlahos, Loukas
Bibcode: 2007HiA....14..104V
Altcode:
  We review the main ideas discussed during the meeting and propose
  methods for a new generation of space accelerators

Title: Excitation of MHD waves in magnetized anisotropic cosmologies
Authors: Kuiroukidis, A.; Kleidis, K.; Papadopoulos, D. B.; Vlahos, L.
Bibcode: 2007A&A...471..409K
Altcode: 2007arXiv0705.2194K
  The excitation of cosmological perturbations in an anisotropic
  cosmological model and in the presence of a homogeneous magnetic
  field was studied, using the resistive magnetohydrodynamic (MHD)
  equations. We have shown that fast-magnetosonic modes, propagating
  normal to the magnetic field, grow exponentially and saturate at high
  values, due to the resistivity. We also demonstrate that Jeans-like
  instabilities can be enhanced inside a resistive fluid and that the
  formation of condensations influence the growing magnetosonic waves.

Title: High energy particle transport in stochastic magnetic fields
    in the solar corona
Authors: Gkioulidou, M.; Zimbardo, G.; Pommois, P.; Veltri, P.;
   Vlahos, L.
Bibcode: 2007A&A...462.1113G
Altcode:
  Aims:We study energetic particle transport in the solar corona in the
  presence of magnetic fluctuations by analyzing the motion of protons
  injected at the center of a model coronal loop. <BR />Methods: We
  set up a numerical realization of magnetic turbulence, in which the
  magnetic fluctuations are represented by a Fourier expansion with
  random phases. We perform test particle simulations by varying the
  turbulence correlation length λ, the turbulence level, and the proton
  energy. Coulomb collisions are neglected. <BR />Results: For large λ,
  the ratio ρ/λ (with ρ the Larmor radius) is small, and the magnetic
  moment is conserved. In this case, a fraction of the injected protons,
  which grow with the fluctuation level, are trapped at the top of the
  magnetic loop, near the injection region, by magnetic mirroring due to
  the magnetic fluctuations. The rest of the protons propagate freely
  along B, corresponding to nearly ballistic transport. Decreasing λ,
  that is, increasing the ratio ρ/λ, the magnetic moment is no longer
  well conserved, and pitch angle diffusion progressively sets in. Pitch
  angle diffusion leads to a decrease in the trapped population and
  progressively changes proton transport from ballistic to superdiffusive,
  and finally, for small λ, to diffusive. <BR />Conclusions: .Particle
  mirroring by magnetic turbulence makes for compact trapping regions. The
  particle dynamics inside the magnetic loop is non-Gaussian and the
  statistical description of transport properties requires the use of
  such ideas as the Lévy random walk.

Title: Magnetic Complexity, Fragmentation, Particle Acceleration
    and Radio Emission from the Sun
Authors: Vlahos, Loukas
Bibcode: 2007LNP...725...15V
Altcode:
  The most popular flare model used to explain the energy release,
  particle acceleration and radio emission is based on the following
  assumptions: (1) The formation of a current sheet above a magnetic loop,
  (2) The stochastic acceleration of particles in the current sheet at
  the helmet of the loop, (3) the transport and trapping of particles
  inside the flaring loop. We review the observational consequences of the
  above model and try to generalize by putting forward a new suggestion,
  namely assuming that a complex active region driven by the photospheric
  motions forms naturally a large number of stochastic current sheets that
  accelerate particles, which in turn can be trapped or move along complex
  field line structures. The emphasis will be placed on the efficiency and
  the observational tests of the different models proposed for a flare.

Title: Particle Acceleration in a Three-Dimensional Model of
    Reconnecting Coronal Magnetic Fields
Authors: Cargill, Peter J.; Vlahos, Loukas; Turkmani, Rim; Galsgaard,
   Klaus; Isliker, Heinz
Bibcode: 2007sdeh.book..249C
Altcode:
  No abstract at ADS

Title: Interaction of gravitational waves with strongly magnetized
    plasmas
Authors: Isliker, Heinz; Sandberg, Ingmar; Vlahos, Loukas
Bibcode: 2006PhRvD..74j4009I
Altcode: 2006astro.ph..3828I
  We study the interaction of a gravitational wave (GW) with a plasma
  that is strongly magnetized. The GW is considered a small disturbance,
  and the plasma is modeled by the general relativistic analogue of the
  induction equation of ideal MHD and the single fluid equations. The
  equations are specified to two different cases, first to Cartesian
  coordinates and a constant background magnetic fields, and second to
  spherical coordinates together with a background magnetic field that
  decays with the inverse radial distance. The equations are derived
  without neglecting any of the nonlinear interaction terms, and the
  nonlinear equations are integrated numerically. We find that for
  strong magnetic fields of the order of 10<SUP>15</SUP>G the GW excites
  electromagnetic plasma waves very close to the magnetosonic mode. The
  magnetic and electric field oscillations have very high amplitude, and a
  large amount of energy is absorbed from the GW by the electromagnetic
  oscillations, of the order of 10<SUP>23</SUP>erg/cm<SUP>3</SUP>
  in the case presented here, which, when assuming a relatively
  small volume in a star’s magnetosphere as an interaction region,
  can yield a total energy of at least 10<SUP>41</SUP>erg and may be
  up to 10<SUP>43</SUP>erg. The absorbed energy is proportional to
  B<SUB>0</SUB><SUP>2</SUP>, with B<SUB>0</SUB> the background magnetic
  field. The energizing of the plasma takes place on fast time scales
  of the order of milliseconds. Our results imply that the GW-plasma
  interaction is an efficient and important mechanism in magnetar
  atmospheres, most prominently close to the star, and, under very
  favorable conditions though, it might even be the primary energizing
  mechanism behind giant flares.

Title: Gyrokinetic electron acceleration in the force-free corona
    with anomalous resistivity
Authors: Arzner, K.; Vlahos, L.
Bibcode: 2006A&A...454..957A
Altcode: 2006astro.ph..4161A
  Aims.We numerically explore electron acceleration and coronal heating
  by dissipative electric fields.<BR /> Methods: .Electrons are traced
  in linear force-free magnetic fields extrapolated from SOHO/MDI
  magnetograms, endowed with anomalous resistivity (η) in localized
  dissipation regions where the magnetic twist ∇ × hat{{b}} exceeds a
  given threshold. Associated with η &gt; 0 is a parallel electric field
  {E} = η {j} that can accelerate runaway electrons. In order to gain
  observational predictions, we inject electrons inside the dissipation
  regions and follow them for several seconds in real time.<BR /> Results:
  .Precipitating electrons that leave the simulation system at height
  z = 0 are associated with hard X rays, and electrons that escape at
  height z ∼ 3× 10<SUP>4</SUP> km are associated with normal-drifting
  type IIIs at the local plasma frequency. A third, trapped population
  is related to gyrosynchrotron emission. Time profiles and spectra
  of all three emissions are calculated, and their dependence on the
  geometric model parameters and on η is explored. It is found that
  precipitation generally precedes escape by fractions of a second and
  that the electrons perform many visits to the dissipation regions
  before leaving the simulation system. The electrons impacting z =
  0 reach higher energies than the escaping ones, and non-Maxwellian
  tails are observed at energies above the largest potential drop across a
  single dissipation region. Impact maps at z = 0 show the tendency of the
  electrons to arrive at the borders of sunspots of one polarity.<BR />
  Conclusions: .Although the magnetograms used here belong to non-flaring
  times, so that the simulations refer to nanoflares and "quiescent"
  coronal heating, it is conjectured that the same process, on a larger
  scale, is responsible for solar flares.

Title: High Energy Particle Transport in Stochastic Magnetic Fields
    in Solar Coronal Loops
Authors: Gkioulidou, M.; Zimbardo, G.; Pammois, P.; Veltri, P.;
   Vlahos, L.
Bibcode: 2006ESASP.617E.152G
Altcode: 2006soho...17E.152G
  No abstract at ADS

Title: Particle Acceleration in a Three-Dimensional Model of
    Reconnecting Coronal Magnetic Fields
Authors: Cargill, Peter J.; Vlahos, Loukas; Turkmani, Rim; Galsgaard,
   Klaus; Isliker, Heinz
Bibcode: 2006SSRv..124..249C
Altcode: 2006SSRv..tmp..111C
  Particle acceleration in large-scale turbulent coronal magnetic fields
  is considered. Using test particle calculations, it is shown that
  both cellular automata and three dimensional MHD models lead to the
  production of relativistic particles on sub-second timescales with
  power law distribution functions. In distinction with the monolithic
  current sheet models for solar flares, particles gain energy by multiple
  interactions with many current sheets. Difficulties that need to be
  addressed, such as feedback between particle acceleration and MHD,
  are discussed.

Title: Particle acceleration in stochastic current sheets in stressed
    coronal active regions
Authors: Turkmani, R.; Cargill, P. J.; Galsgaard, K.; Vlahos, L.;
   Isliker, H.
Bibcode: 2006A&A...449..749T
Altcode:
  Aims.To perform numerical experiments of particle acceleration in the
  complex magnetic and electric field environment of the stressed solar
  corona.Methods.The magnetic and electric fields are obtained from a
  3-D MHD experiment that resembles a coronal loop with photospheric
  regions at both footpoints. Photospheric footpoint motion leads to
  the formation of a hierarchy of stochastic current sheets. Particles
  (protons and electrons) are traced within these current sheets
  starting from a thermal distribution using a relativistic test particle
  code.Results.In the corona the particles are subject to acceleration
  as well as deceleration, and a considerable portion of them leave the
  domain having received a net energy gain. Particles are accelerated to
  high energies in a very short time (both species can reach energies
  up to 100 GeV within 5 × 10<SUP>-2</SUP> s for electrons and 5
  × 10<SUP>-1</SUP> s for protons). The final energy distribution
  shows that while one quarter of the particles retain their thermal
  distribution, the rest have been accelerated, forming a two-part power
  law. Accelerated particles are either trapped within electric field
  regions of opposite polarities, or escape the domain mainly through
  the footpoints. The particle dynamics are followed in detail and it
  is shown how this dynamic affects the time evolution of the system
  and the energy distribution. The scaling of these results with time
  and length scale is examined and the Bremstrahlung signature of X-ray
  photons resulting from escaping particles hitting the chromosphere is
  calculated and found to have a main power law part with an index γ =
  - 1.8, steeper than observed. Possible resolutions of this discrepency
  are discussed.

Title: Acceleration of low energy charged particles by gravitational
    waves
Authors: Voyatzis, G.; Vlahos, L.; Ichtiaroglou, S.; Papadopoulos, D.
Bibcode: 2006PhLA..352..261V
Altcode: 2005astro.ph.12192V
  The acceleration of charged particles in the presence of a magnetic
  field and gravitational waves is under consideration. It is shown
  that the weak gravitational waves can cause the acceleration of low
  energy particles under appropriate conditions. Such conditions may
  be satisfied close to the source of the gravitational waves if the
  magnetized plasma is in a turbulent state.

Title: Stochastic Acceleration in Turbulent Electric Fields Generated
    by 3D Reconnection
Authors: Onofri, Marco; Isliker, Heinz; Vlahos, Loukas
Bibcode: 2006PhRvL..96o1102O
Altcode: 2006astro.ph..4192O
  Electron and proton acceleration in three-dimensional electric and
  magnetic fields is studied through test particle simulations. The fields
  are obtained by a three-dimensional magnetohydrodynamic simulation
  of magnetic reconnection in slab geometry. The nonlinear evolution
  of the system is characterized by the growth of many unstable modes
  and the initial current sheet is fragmented with formation of small
  scale structures. We inject at random points inside the evolving
  current sheet a Maxwellian distribution of particles. In a relatively
  short time (less than a millisecond) the particles develop a power-law
  tail. The acceleration is extremely efficient and the electrons absorb
  a large percentage of the available energy in a small fraction of the
  characteristic time of the MHD simulation, suggesting that resistive MHD
  codes are unable to represent the full extent of particle acceleration.

Title: The Effect of Coherent Structures on Stochastic Acceleration
    in MHD Turbulence
Authors: Arzner, Kaspar; Knaepen, Bernard; Carati, Daniele; Denewet,
   Nicolas; Vlahos, Loukas
Bibcode: 2006ApJ...637..322A
Altcode: 2005astro.ph..9717A
  We investigate the influence of coherent structures on particle
  acceleration in the strongly turbulent solar corona. By randomizing
  the Fourier phases of a pseudospectral simulation of isotropic
  magnetohydrodynamic (MHD) turbulence (Re~300) and tracing collisionless
  test protons in both the exact-MHD and phase-randomized fields, it is
  found that the phase correlations enhance the acceleration efficiency
  during the first adiabatic stage of the acceleration process. The
  underlying physical mechanism is identified as the dynamical MHD
  alignment of the magnetic field with the electric current, which
  favors parallel (resistive) electric fields responsible for initial
  injection. Conversely, the alignment of the magnetic field with the
  bulk velocity weakens the acceleration by convective electric fields
  -uXb at a nonadiabatic stage of the acceleration process. We point out
  that nonphysical parallel electric fields in random-phase turbulence
  proxies lead to artificial acceleration and that the dynamical MHD
  alignment can be taken into account on the level of the joint two-point
  function of the magnetic and electric fields and is therefore amenable
  to Fokker-Planck descriptions of stochastic acceleration.

Title: a Model of Quiet Time Particle Acceleration in Interplanetary
    Space
Authors: Lepreti, F.; Isliker, H.; Vlahos, L.; Petraki, K.
Bibcode: 2005ESASP.600E.130L
Altcode: 2005ESPM...11..130L; 2005dysu.confE.130L
  No abstract at ADS

Title: AFS dynamics in a short-lived active region
Authors: Zuccarello, F.; Battiato, V.; Contarino, L.; Romano, P.;
   Spadaro, D.; Vlahos, L.
Bibcode: 2005A&A...442..661Z
Altcode:
  In the framework of the study on active region emergence, we report the
  results obtained from the analysis of the short-lived (7 days) active
  region NOAA 10407. The data used were acquired during an observational
  campaign carried out with the THEMIS telescope in IPM mode in July 2003,
  coordinated with other ground- and space-based instruments (INAF-OACT,
  DOT, BBSO, MDI/SOHO, EIT/SOHO, TRACE). We determined the morphological
  and magnetic evolution of NOAA 10407, as well as the velocity fields
  associated with its magnetic structures. Within the limits imposed by
  the spatial and temporal resolution of the images analyzed, the first
  evidence of the active region formation is initially observed in the
  transition region and lower corona, and later on (i.e. after about 7
  h) in the inner layers, as found in a previous analysis concerning a
  long-lived, recurrent active region. The results also indicate that
  the AFS formed in the active region shows typical upward motion at
  the AFS's tops and downward motion at the footpoints. The velocity
  values relevant to the upward motions decrease over the evolution
  of the region, similarly to the case of the recurrent active region,
  while we notice an increasing trend in the downflow velocity during
  the early phases of the time interval analyzed by THEMIS. On the other
  hand, the AFS preceding legs show a higher downflow than the following
  ones, a result in contrast with that found in the long-lived active
  region. The chromospheric area overhanging the sunspot umbra shows an
  upward motion of ∼ 2 km s<SUP>-1</SUP>, while that above the pores
  shows a downward motion of ~4 km s<SUP>-1</SUP>.

Title: Galaxy Formation and Cosmic-Ray Acceleration in a Magnetized
    Universe
Authors: Vlahos, Loukas; Tsagas, Christos G.; Papadopoulos, Demetrios
Bibcode: 2005ApJ...629L...9V
Altcode: 2005astro.ph..6742V
  We study the linear magnetohydrodynamic behavior of a Newtonian
  cosmology with a viscous magnetized fluid of finite conductivity and
  generalize the Jeans instability criterion. The presence of the field
  favors the anisotropic collapse of the fluid, which in turn leads
  to further magnetic amplification and to enhanced current-sheet
  formation in the plane normal to the ambient magnetic field. When
  the currents exceed a certain threshold, the resulting electrostatic
  turbulence can dramatically amplify the resistivity of the medium
  (anomalous resistivity). This could trigger strong electric fields and
  subsequently the acceleration of ultra-high-energy cosmic rays during
  the formation of protogalactic structures.

Title: Quiet time particle acceleration in interplanetary space
Authors: Lepreti, F.; Isliker, H.; Petraki, K.; Vlahos, L.
Bibcode: 2005A&A...432.1049L
Altcode: 2004astro.ph.12214L
  We propose a model for the acceleration of charged particles in
  interplanetary space that appear during quiet time periods, that is, not
  associated with solar activity events like intense flares or coronal
  mass ejections. The interaction of charged particles with modeled
  turbulent electromagnetic fields, which mimic the fields observed in the
  interplanetary medium, is studied. The turbulence is modeled by means
  of a dynamical system, the Gledzer-Ohkitani-Yamada (GOY) shell model,
  which describes the gross features of the Navier-Stokes equations. The
  GOY model is used to build a 3D velocity field, which in turn is used
  to numerically solve the ideal magneto-hydrodynamic (MHD) induction
  equation, while the electric field is calculated from the ideal Ohm's
  law. Particle acceleration in such an environment is investigated by
  test particle simulations, and the resulting energy distributions are
  discussed and compared to observations of suprathermal electrons and
  ions during quiet periods in interplanetary space.

Title: Statistical Properties of Dissipative MHD Accelerators
Authors: Arzner, Kaspar; Vlahos, Loukas; Knaepen, Bernard; Denewet,
   Nicolas
Bibcode: 2005astro.ph..3147A
Altcode:
  We use exact orbit integration to investigate particle acceleration in
  a Gauss field proxy of magnetohydrodynamic (MHD) turbulence. Regions
  where the electric current exceeds a critical threshold are declared
  to be `dissipative' and endowed with super-Dreicer electric field
  ${\bf E}_\Omega = \eta {\bf j}$. In this environment, test particles
  (electrons) are traced and their acceleration to relativistic energies
  is studied. As a main result we find that acceleration mostly takes
  place within the dissipation regions, and that the momentum increments
  have heavy (non-Gaussian) tails, while the waiting times between
  the dissipation regions are approximately exponentially distributed
  with intensity proportional to the particle velocity. No correlation
  between the momentum increment and the momentum itself is found. Our
  numerical results suggest an acceleration scenario with ballistic
  transport between independent `black box' accelerators.

Title: Particle Acceleration in Stressed Coronal Magnetic Fields
Authors: Turkmani, R.; Vlahos, L.; Galsgaard, K.; Cargill, P. J.;
   Isliker, H.
Bibcode: 2005ApJ...620L..59T
Altcode:
  This Letter presents an analysis of particle acceleration in a
  model of the complex magnetic field environment in the flaring solar
  corona. A slender flux tube, initially in hydrodynamic equilibrium,
  is stressed by random photospheric motions. A three-dimensional
  MHD code is used to follow the stochastic development of transient
  current sheets. These processes generate a highly fragmented electric
  field, through which particles are tracked using a relativistic test
  particle code. It is shown that both ions and electrons are accelerated
  readily to relativistic energies in times of order 10<SUP>-2</SUP>
  s for electrons and 10<SUP>-1</SUP> s for protons forming power-law
  distributions in energy.

Title: Electron acceleration and radiation in evolving complex
    active regions
Authors: Anastasiadis, A.; Gontikakis, C.; Vilmer, N.; Vlahos, L.
Bibcode: 2004A&A...422..323A
Altcode:
  We present a model for the acceleration and radiation of solar
  energetic particles (electrons) in evolving complex active regions. The
  spatio - temporal evolution of active regions is calculated using a
  cellular automaton model, based on self-organized criticality. The
  acceleration of electrons is due to the presence of randomly placed,
  localized electric fields produced by the energy release process,
  simulated by the cellular automaton model. We calculate the resulting
  kinetic energy distributions of the particles and their emitted X-ray
  radiation spectra using the thick target approximation, and we perform a
  parametric study with respect to number of electric fields present and
  thermal temperature of the injected distribution. Finally, comparing
  our results with the existing observations, we find that they are in
  a good agreement with the observed X-ray spectra in the energy range
  100-1000 keV.

Title: On the distribution of magnetic energy storage in solar
    active regions
Authors: Fragos, T.; Rantsiou, E.; Vlahos, L.
Bibcode: 2004A&A...420..719F
Altcode:
  A two-dimensional probabilistic Cellular Automaton is used to model
  the appearance of active regions at the solar surface. We assume that
  two main competing processes control the magnetic field evolution
  at the solar surface (1) the magnetic field is locally enhanced by
  the flux emergence and/or the coalescence of emerged magnetic flux
  and (2) it is diminished by flux cancellation or diffusion. The flux
  emergence follows a basic percolation rule; it is more probable at the
  points were magnetic flux already exists. The magnetic field is also
  enhanced when magnetic fields of the same polarity collide. The flux
  cancellation is due either to the gradual diffusion of the magnetic
  field, when it is isolated, or to the partial release of energy when
  opposite magnetic field lines collide. The percolation model proposed
  in this article is capable of reproducing the statistical properties
  of the evolving active regions. The evolving simulated magnetograms,
  derived from our model, are used to estimate the 3-D magnetic fields
  above the photosphere using constant α force-free extrapolation
  techniques. Based on the above analysis we are able to estimate a
  variety of observed statistical characteristics, e.g. the size and flux
  distribution of the magnetic fields at the solar surface, the fractal
  dimension of the magnetic structures formed at the photosphere, the
  energy release frequency distribution, the waiting time distribution
  of the sporadic energy releases and the statistical properties of the
  steep horizontal magnetic field gradients in the extrapolated coronal
  magnetic field. Our main conclusion is that the photospheric driver
  plays a crucial role in the observed flare statistics, and the solar
  magnetograms, when interpreted properly, carry important statistical
  information for the solar coronal activity (coronal heating, flares,
  CME etc.).

Title: Particle Acceleration in an Evolving Network of Unstable
    Current Sheets
Authors: Vlahos, Loukas; Isliker, Heinz; Lepreti, Fabio
Bibcode: 2004ApJ...608..540V
Altcode: 2004astro.ph..2645V
  We study the acceleration of electrons and protons interacting with
  localized, multiple, small-scale dissipation regions inside an evolving,
  turbulent active region. The dissipation regions are unstable current
  sheets (UCSs), and in their ensemble they form a complex, fractal,
  evolving network of acceleration centers. Acceleration and energy
  dissipation are thus assumed to be fragmented. A large-scale magnetic
  topology provides the connectivity between the UCSs and in this way
  determines the degree of possible multiple acceleration. The particles
  travel along the magnetic field freely without losing or gaining energy
  until they reach a UCS. In a UCS, a variety of acceleration mechanisms
  are active, with the end result that the particles depart with a new
  momentum. The stochastic acceleration process is represented in the
  form of continuous-time random walk, which allows one to estimate the
  evolution of the energy distribution of the particles. It is found
  that under certain conditions, electrons are heated and accelerated to
  energies above 1 MeV in much less than 1 s. Hard X-ray and microwave
  spectra are calculated from the electrons' energy distributions, and
  they are found to be compatible with the observations. Ions (protons)
  are also heated and accelerated, reaching energies up to 10 MeV almost
  simultaneously with the electrons. The diffusion of the particles inside
  the active region is extremely fast (anomalous superdiffusion). Although
  our approach does not provide insight into the details of the specific
  acceleration mechanisms involved, its benefits are that it relates
  acceleration to the energy release, it well describes the stochastic
  nature of the acceleration process, and it can incorporate the flaring
  large-scale magnetic topology, potentially even its temporal evolution.

Title: Particle Acceleration in Multiple Dissipation Regions
Authors: Arzner, Kaspar; Vlahos, Loukas
Bibcode: 2004ApJ...605L..69A
Altcode: 2004astro.ph..2605A
  The sharp magnetic discontinuities that naturally appear in solar
  magnetic flux tubes driven by turbulent photospheric motions
  are associated with intense currents. Parker proposed that
  these currents can become unstable to a variety of microscopic
  processes, with the net result of dramatically enhanced resistivity
  and heating (nano-flares). The electric fields associated
  with such ``hot spots'' are also expected to enhance particle
  acceleration. We test this hypothesis by exact relativistic orbit
  simulations in strong random phase magnetohydrodynamic turbulence
  that is forming localized super-Dreicer Ohm electric fields
  (10<SUP>2</SUP>&lt;=E<SUB>Ω</SUB>/E<SUB>D</SUB>&lt;=10<SUP>5</SUP>)
  occurring in 2%-15% of the volume. It is found that these fields
  indeed yield a large amplification of acceleration of electrons and
  ions and can effectively overcome the injection problem. We suggest in
  this article that nanoflare heating will be associated with sporadic
  particle acceleration.

Title: On the Self-Similarity of Unstable Magnetic Discontinuities
    in Solar Active Regions
Authors: Vlahos, Loukas; Georgoulis, Manolis K.
Bibcode: 2004ApJ...603L..61V
Altcode:
  We investigate the statistical properties of possible magnetic
  discontinuities in two solar active regions over the course
  of several hours. We use linear force-free extrapolations to
  calculate the three-dimensional magnetic structure in the active
  regions. Magnetic discontinuities are identified using various selection
  criteria. Independently of the selection criterion, we identify large
  numbers of magnetic discontinuities whose free magnetic energies
  and volumes obey well-formed power-law distribution functions. The
  power-law indices for the free energies are in the range [-1.6,
  -1.35], in remarkable agreement with the power-law indices found in the
  occurrence frequencies of solar flare energies. This agreement and the
  strong self-similarity of the volumes that are likely to host flares
  suggest that the observed statistics of flares may be the natural
  outcome of a preexisting spatial self-organization accompanying the
  energy fragmentation in solar active regions. We propose a dynamical
  picture of flare triggering consistent with recent observations by
  reconciling our results with the concepts of percolation theory and
  self-organized criticality. These concepts rely on self-organization,
  which is expected from the fully turbulent state of the magnetic fields
  in the solar atmosphere.

Title: Impulsive Electron Acceleration by Gravitational Waves
Authors: Vlahos, Loukas; Voyatzis, George; Papadopoulos, Demetrios
Bibcode: 2004ApJ...604..297V
Altcode: 2003astro.ph.12151V
  We investigate the nonlinear interaction of a strong gravitational
  wave with the plasma during the collapse of a massive magnetized
  star and subsequent formation of a black hole or during the merging
  of neutron star binaries (the central engine). We found that under
  certain conditions this coupling may result in an efficient energy-space
  diffusion of particles. We suggest that the atmosphere created around
  the central engine is filled with three-dimensional magnetic neutral
  sheets (magnetic nulls). We demonstrate that the passage of strong
  pulses of gravitational waves through the magnetic neutral sheets
  accelerates electrons to very high energies. Superposition of many
  such short-lived accelerators, embedded inside a turbulent plasma,
  may be the source of the observed impulsive short-lived bursts. We
  conclude that in several astrophysical events, gravitational pulses
  may accelerate the tail of the ambient plasma to very high energies
  and become the driver for many types of astrophysical bursts.

Title: Energetic Particle Acceleration and Radiation in Evolving
    Complex Active Regions
Authors: Anastasiadis, A.; Gontikakis, C.; Vilmer, N.; Vlahos, L.
Bibcode: 2004hell.conf...71A
Altcode:
  No abstract at ADS

Title: Are Gamma Ray Bursts Driven by Gravitational Waves?
Authors: Vlahos, L.; Voyatzis, G.; Papadopoulos, D.
Bibcode: 2004BaltA..13..324V
Altcode: 2004OAst...13..324V
  We investigate the non-linear interaction of a strong gravitational wave
  with the plasma during the collapse of a massive magnetized star to form
  a black hole, or during the merging of neutron star binaries. We find
  that under certain conditions this coupling may result in an efficient
  energy space diffusion of particles. We suggest that the atmosphere
  created around the central engine is filled with 3-D magnetic neutral
  sheets (magnetic nulls). The passage of strong pulses of gravitational
  waves through the magnetic neutral sheets accelerates electrons to
  very high energies. We conclude that in several astrophysical events
  the gravitational pulses may accelerate the tail of the ambient
  plasma to very high energies and become the driver for many types of
  astrophysical bursts.

Title: Energy Release and Particle Acceleration in Complex Active
    Regions
Authors: Vlahos, L.
Bibcode: 2004cosp...35.1994V
Altcode: 2004cosp.meet.1994V
  Photospheric fluid flows and magnetic fields, magnetic energy
  release and particle acceleration have been treated so far as separate
  issues. In the widely used model the impulsive energy release (flares)
  is related to the 3D reconnection in current sheet(s), which are
  adjusted to simple magnetic topologies (magnetic loops). MHD turbulence
  generated from the reconnecting sheet fill the adjusted loop(s) and
  accelerate particles. We will review the strong and weak points of
  this scenario and attempt to generalized it, for complex and possibly
  more realistic magnetic topologies generated by the extrapolation of
  observed photospheric magnetic fields.

Title: Particle acceleration and radiation in an evolving active
    region based on a Cellular Automaton (CA) model
Authors: Anastasiadis, A.; Gontikakis, C.; Vilmer, N.; Vlahos, L.
Bibcode: 2002ESASP.506..265A
Altcode: 2002svco.conf..265A; 2002ESPM...10..265A
  We present a model for the acceleration and radiation of solar energetic
  particles (electrons) in an evolving active region. The spatio-temporal
  evolution of the active region is calculated using a Cellular Automaton
  (CA) model for the energy release process. The acceleration of particles
  is due to the presence of randomly placed, localized electric fields. We
  calculate the resulting kinetic energy distributions of the particles
  and the emitted radiation by performing a parametric study with respect
  to the trapping time of the injected distribution.

Title: The extended cellular automaton (X-CA) model for lolar flares
Authors: Isliker, H.; Anastasiadis, A.; Vlahos, L.
Bibcode: 2002ESASP.506..641I
Altcode: 2002svco.conf..641I; 2002ESPM...10..641I
  We have developed a new type of cellular automaton (CA) model, the
  extended CA (X-CA), for the study of solar flares. The X-CA model
  is consistent with the MHD approach, in contrast to the previously
  proposed CA models (classical CAs), it consistently yields all the
  relevant physical variables, and it successfully reproduces the
  observed distributions of total energy, peak flux, and duration of
  solar flares. We present and discuss the relevant plasma processes
  and set-up which are implemented by the X-CA model in the framework
  of a commonly accepted solar flare scenario.

Title: Acceleration and radiation model of solar energetic particles
    in an evolving active region
Authors: Anastasiadis, A.; Gontikakis, C.; Vilmer, N.; Vlahos, L.
Bibcode: 2002ESASP.505..337A
Altcode: 2002solm.conf..337A; 2002IAUCo.188..337A
  We present a model for the acceleration and radiation of solar energetic
  particles (electrons) in an evolving active region. The spatio-temporal
  evolution of the active region is calculated using a Cellular Automaton
  (CA) model for the energy release process. The acceleration of particles
  is due to the presence of randomly placed, localized electric fields. We
  calculate the resulting kinetic energy distributions of the particles
  by performing a parametric study with respect to the trapping time
  of the injected distribution. Our results show a power law or a power
  law with an exponential tail behavior for the resulting kinetic energy
  distribution, depending on the maximum trapping time of the injected
  particles in the acceleration volume. Finally we calculate the emitted
  radiation spectrum from the resulting energy distributions.

Title: Statistical properties of the evolution of solar magnetic
    fields
Authors: Vlahos, Loukas
Bibcode: 2002ESASP.505..105V
Altcode: 2002solm.conf..105V; 2002IAUCo.188..105V
  We are making an attempt to associate the formation and evolution
  of active regions with the heating and flaring of the plasmas in the
  solar atmosphere above the active region. The working hypothesis in
  our review is that "active regions are open dynamical systems away
  from equilibrium, driven by the turbulent convection zone". New
  magnetic loops emerge from the convection zone and are subject to
  surface diffusion (random motion), which leads to cancellation of
  magnetic energy when they collide with magnetic structures of opposite
  polarity. In the course of their evolution from birth to disappearance,
  active regions reach quickly the stage of Self-Organized Criticality
  (SOC), heat the corona by driving nano-flares, micro-flares and
  flares. We believe that the statistical properties of the active
  regions at the photosphere (size distribution, fractal dimension
  etc.) are correlated with the statistical properties of all aspects
  of solar activity (Ellerman Bombs, Bright Points, flares, particle
  acceleration, etc.). Surprisingly, all these phenomena share one common
  characteristic, they are self-similar and their statistical behaviour
  follows well defined power laws. This last point reinforces our belief
  that the solar atmosphere is coupled, through the magnetic field,
  with the convection zone, which drives all the observed activity at
  the photosphere, chromosphere, corona and interplanetary space.

Title: Statistical Properties of the Energy Release in Emerging and
    Evolving Active Regions
Authors: Vlahos, Loukas; Fragos, Tassos; Isliker, Heinz; Georgoulis,
   Manolis
Bibcode: 2002ApJ...575L..87V
Altcode: 2002astro.ph..7340V
  The formation and evolution of active regions are inherently complex
  phenomena. Magnetic fields generated at the base of the convection zone
  follow a chaotic evolution before reaching the solar surface. In this
  article, we use a two-dimensional probabilistic cellular automaton
  to model the statistical properties of the magnetic patterns formed
  on the solar surface and to estimate the magnetic energy released in
  the interaction of opposite polarities. We assume that newly emerged
  magnetic flux tubes stimulate the emergence of new magnetic flux in
  their neighborhood. The flux tubes move randomly on the surface of the
  Sun, and they cancel and release their magnetic energy when they collide
  with magnetic flux of opposite polarity, or diffuse into the ``empty''
  photosphere. We assume that cancellation of magnetic flux in collisions
  causes ``flares'' and determine the released energy as the difference in
  the square of the magnetic field flux (E~B<SUP>2</SUP>). The statistics
  of the simulated flares follow a power-law distribution in energy,
  f(E)~E<SUP>-a</SUP>, where a=2.2+/-0.1. The size distribution function
  of the simulated active regions exhibits a power-law behavior with index
  k~1.93+/-0.08, and the fractal dimension of the magnetized areas on
  the simulated solar surface is close to D<SUB>F</SUB>~1.42+/-0.12. Both
  quantities, D<SUB>F</SUB> and k, are inside the range of the observed
  values.

Title: Waves and instabilities in an anisotropic universe
Authors: Papadopoulos, D.; Vlahos, L.; Esposito, F. P.
Bibcode: 2002A&A...382....1P
Altcode: 2001astro.ph.10455P
  The excitation of low frequency plasma waves in an expanding anisotropic
  cosmological model that contains a magnetic field frozen into the matter
  and pointing in the longitudinal direction is discussed. Using the exact
  equations governing finite-amplitude wave propagation in hydromagnetic
  media within the framework of the general theory of relativity, we
  show that a spectrum of magnetized sound waves will be excited and
  form large-scale ``damped oscillations'' in the expanding universe. The
  characteristic frequency of the excited waves is slightly shifted away
  from the sound frequency and the shift depends on the strength of the
  primordial magnetic field. This magnetic field dependent shift may
  have an effect on the acoustic peaks of the CMB.

Title: MHD consistent cellular automata (CA) models. II. Applications
    to solar flares
Authors: Isliker, H.; Anastasiadis, A.; Vlahos, L.
Bibcode: 2001A&A...377.1068I
Altcode: 2001astro.ph..8365I
  In Isliker et al. (\cite{Isliker00b}), an extended cellular automaton
  (X-CA) model for solar flares was introduced. In this model, the
  interpretation of the model's grid-variable is specified, and the
  magnetic field, the current, and an approximation to the electric field
  are yielded, all in a way that is consistent with Maxwell's and the
  MHD equations. The model also reproduces the observed distributions of
  total energy, peak-flux, and durations. Here, we reveal which relevant
  plasma physical processes are implemented by the X-CA model and in what
  form, and what global physical set-up is assumed by this model when it
  is in its natural state (self-organized criticality, SOC). The basic
  results are: (1) On large-scales, all variables show characteristic
  quasi-symmetries: the current has everywhere a preferential direction,
  the magnetic field exhibits a quasi-cylindrical symmetry. (2) The
  global magnetic topology forms either (i) closed magnetic field lines
  around and along a more or less straight neutral line for the model in
  its standard form, or (ii) an arcade of field lines above the bottom
  plane and centered along a neutral line, if the model is slightly
  modified. (3) In case of the magnetic topology (ii), loading can
  be interpreted as if there were a plasma which flows predominantly
  upwards, whereas in case of the magnetic topology (i), as if there
  were a plasma flow expanding from the neutral line. (4) The small-scale
  physics in the bursting phase represent localized diffusive processes,
  which are triggered when a quantity which is an approximately linear
  function of the current exceeds a threshold. (5) The interplay of
  loading and bursting in the X-CA model can be interpreted as follows:
  the local diffusivity usually has a value which is effectively zero,
  and it turns locally to an anomalous value if the mentioned threshold
  is exceeded, whereby diffusion dominates the quiet evolution (loading),
  until the critical quantity falls below the threshold again. (6) Flares
  (avalanches) are accompanied by the appearance of localized, intense
  electric fields. A typical example of the spatio-temporal evolution of
  the electric field during a flare is presented. (7) In a variant on
  the X-CA model, the magnitude of the current is used directly in the
  instability criterion, instead of the approximately linear function
  of it. First results indicate that the SOC state persists and is only
  slightly modified: distributions of the released energy are still
  power-laws with slopes comparable to the ones of the non-modified X-CA
  model, and the large scale structures, a characteristic of the SOC
  state, remain unchanged. (8) The current-dissipation during flares is
  spatially fragmented into a large number of dissipative current-surfaces
  of varying sizes, which are spread over a considerably large volume,
  and which do not exhibit any kind of simple spatial organization as
  a whole. These current-surfaces do not grow in the course of time,
  they are very short-lived, but they multiply, giving rise to new
  dissipative current-surfaces which are spread further around. They show
  thus a highly dynamic temporal evolution.\ It follows that the X-CA
  model represents an implementation of the flare scenario of Parker
  (\cite{Parker93}) in a rather complete way, comprising aspects from
  small scale physics to the global physical set-up, making though some
  characteristic simplifications which are unavoidable in the frame-work
  of a CA.

Title: Fast magnetosonic waves driven by gravitational waves
Authors: Papadopoulos, D.; Stergioulas, N.; Vlahos, L.; Kuijpers, J.
Bibcode: 2001A&A...377..701P
Altcode: 2001astro.ph..7043P
  The propagation of a gravitational wave (GW) through a magnetized
  plasma is considered. In particular, we study the excitation of
  fast magnetosonic waves (MSW) by a gravitational wave, using the
  linearized general-relativistic hydromagnetic equations. We derive the
  dispersion relation for the plasma, treating the gravitational wave
  as a perturbation in a Minkowski background space-time. We show that
  the presence of gravitational waves will drive magnetosonic waves in
  the plasma and discuss the potential astrophysical implications.

Title: The study of solar flares with the extended cellular automaton
    (X-CA) model
Authors: Isliker, H.; Anastasiadis, A.; Vlahos, L.
Bibcode: 2001hell.confE..39I
Altcode:
  No abstract at ADS

Title: A cellular automaton model for the magnetic activity in
    accretion discs
Authors: Pavlidou, V.; Kuijpers, J.; Vlahos, L.; Isliker, H.
Bibcode: 2001A&A...372..326P
Altcode:
  In this paper we attempt, for the first time, to simulate the magnetic
  activity of an accretion disc using a probabilistic cellular automaton
  model. Our model is based on three free parameters, the probabilities of
  spontaneous and stimulated generation of magnetic flux above the surface
  of the disc (S<SUB>0</SUB>, and, respectively, P), and the probability
  of diffusive disappearance of flux below the surface (D). The model
  describes a changing collection of flux tubes which stick out of the
  disc and are anchored inside the disc at their foot-points. Magnetic
  flux tubes transfer angular momentum outwards at a rate which is
  analytically estimated for each single loop. Our model monitors the
  dynamic evolution of both the distribution of magnetic loops and the
  mass transfer which results from angular momentum transport due to
  this distribution. The energy release due to magnetic flaring is also
  recorded as a function of time and exhibits temporal fluctuations with
  power spectra that depend on the assumed emission-profile of single
  flaring loops: (i) for instantaneous emission, the power-spectra
  are flat at low frequencies and turn over at high frequencies to a
  power-law with index -0.3; (ii) for emission-profiles in the form
  of one-sided exponentials, the power-spectra exhibit clear power-law
  behaviour with index -1.7. Fluctuations with a power law index between
  -1 and -1.7 are observed in many systems undergoing accretion. We found
  that our approach allows steady accretion in a disc by the action
  of coronal magnetic flux tubes alone. If we express the effective
  viscosity caused by coronal loops in the usual Shakura-Sunyaev alpha
  parameter of viscosity, we find values which are in good agreement
  with observed values.

Title: MHD consistent cellular automata (CA) models. I. Basic features
Authors: Isliker, H.; Anastasiadis, A.; Vlahos, L.
Bibcode: 2000A&A...363.1134I
Altcode: 2001astro.ph..6111I
  A set-up is introduced which can be superimposed onto the existing
  solar flare cellular automata (CA) models, and which specifies the
  interpretation of the model's variables. It extends the CA models,
  yielding the magnetic field, the current, and an approximation to the
  electric field, in a way that is consistent with Maxwell's and the MHD
  equations. Applications to several solar flare CA models during their
  natural state (self-organized criticality (SOC)) show, among others,
  that (1) the magnetic field exhibits characteristic large-scale
  organization over the entire modeled volume; (2) the magnitude of
  the current seems spatially dis-organized, with no obvious tendency
  towards large-scale structures or even local organization; (3) bursts
  occur at sites with increased current, and after a burst the current
  is relaxed; (4) by estimating the energy released in individual bursts
  with the use of the current as Ohmic dissipation, it turns out that
  the power-law distributions of the released energy persist. The CA
  models, extended with the set-up, can thus be considered as models for
  energy-release through current-dissipation. The concepts of power-law
  loading and anisotropic events (bursts) in CA models are generalized
  to 3-D vector-field models, and their effect on the magnetic field
  topology is demonstrated.

Title: Particle-Acceleration and Radiation in the Turbulent Flow of
    a Jet
Authors: Manolakou, Konstantina; Anastasiadis, Anastasios; Vlahos,
   Loukas
Bibcode: 1999ptep.proc..333M
Altcode:
  We present a numerical model for electron acceleration and radiation
  inside the body of an extragalactic jet. We model the jet environment
  as a turbulent medium generating non-linear structures (eddies and/or
  shocks) through a cascading process. These structures act like in-situ
  accelerators for the electrons that are initially injected from the
  central engine. Two types of acceleration processes are considered:
  second order Fermi-acceleration and shock-drift acceleration,
  depending on the velocity of the turbulent eddies encountered. We
  study the modulation of the energy distribution of electrons in such an
  environment, by incorporating synchrotron radiation losses in the time
  intervals between successive interactions of the particles with the
  turbulent structures. By performing a parametric study with respect
  to the level of turbulent activity and the time intervals between
  interactions, we calculate the temporal evolution of the cut-off
  frequency of the synchrotron radiation spectrum of the particles and
  discuss our results in connection with recent observations.

Title: Flare Physics in Accretion Discs
Authors: Pavlidou, V.; Kuijpers, J.; Vlahos, L.; Isliker, H.
Bibcode: 1999ESASP.448..859P
Altcode: 1999mfsp.conf..859P; 1999ESPM....9..859P
  No abstract at ADS

Title: Particle-acceleration and radiation in the turbulent flow of
    a jet
Authors: Manolakou, K.; Anastasiadis, A.; Vlahos, L.
Bibcode: 1999A&A...345..653M
Altcode:
  We present a numerical model for electron acceleration and radiation
  inside the body of an extragalactic jet. We model the jet environment
  as a turbulent medium generating non-linear structures (eddies and/or
  shocks) through a cascading process. These structures act like in-situ
  accelerators for the electrons that are initially injected from the
  central engine. Two types of acceleration processes are considered:
  second order Fermi-acceleration and shock-drift acceleration,
  depending on the velocity of the turbulent eddies encountered. We
  study the modulation of the energy distribution of electrons in such an
  environment, by incorporating synchrotron radiation losses in the time
  intervals between successive interactions of the particles with the
  turbulent structures. By performing a parametric study with respect
  to the level of turbulent activity and the time intervals between
  interactions, we calculate the temporal evolution of the cut-off
  frequency of the synchrotron radiation spectrum of the particles and
  discuss our results in connection with recent observations.

Title: Derivation of Solar Flare Cellular Automata Models from a
    Subset of the Magnetohydrodynamic Equations
Authors: Vassiliadis, D.; Anastasiadis, A.; Georgoulis, M.; Vlahos, L.
Bibcode: 1998ApJ...509L..53V
Altcode:
  Cellular automata (CA) models account for the power-law distributions
  found for solar flare hard X-ray observations, but their physics
  has been unclear. We examine four of these models and show that
  their criteria and magnetic field distribution rules can be derived
  by discretizing the MHD diffusion equation as obtained from a
  simplified Ohm's law. Identifying the discrete MHD with the CA
  models leads to an expression for the resistivity as a function
  of the current on the flux tube boundary, as may be expected from
  current-driven instabilities. Anisotropic CA models correspond to a
  nonlinear resistivity η(J), while isotropic ones are associated with
  hyperresistivity η(▽<SUP>2</SUP>J). The discrete equations satisfy
  the necessary conditions for self-organized criticality (Lu): there
  is local conservation of a field (magnetic flux), while the nonlinear
  resistivity provides a rapid dissipation and relaxation mechanism. The
  approach justifies many features of the CA models that were originally
  based on intuition.

Title: Variability of the occurrence frequency of solar flares and
    the statistical flare
Authors: Georgoulis, Manolis K.; Vlahos, Loukas
Bibcode: 1998A&A...336..721G
Altcode:
  Self-Organised Criticality (SOC), embedded in cellular automata
  models, has been so far viewed as an attractive phenomenological
  approach for studying the statistical behaviour of flaring activity
  in solar active regions. Well-known statistical properties of flares,
  like the robust scaling laws seen in the distribution functions of
  characteristic parameters of the events, as well as correlations linking
  those parameters, are successfully reproduced by SOC models. Recent
  observations, however, challenge the flexibility of SOC, as they
  reveal a variation of the flaring power-law indices over short-time
  activity periods. The initial SOC models, based on a small-amplitude,
  constant external driver and isotropic instability criteria, appear
  inefficient to predict variable power-law indices. In this paper we
  introduce a SOC-type numerical model, with a number of modifications of
  the original SOC concept. We show that scaling laws and correlations
  between the events' characteristic parameters survive under the
  action of a highly variable driver. A variable driver initiates
  a variability in the resulting power-law indices. We reproduce
  qualitatively and quantitatively the statistics of flaring activity
  during the 154-day periodicity. Moreover, small-scale, anisotropic
  instability criteria imply the existence of a soft population of
  events, with statistical properties analogous to those attributed to
  the hypothetical nanoflares. We show that numerous small-scale events
  could be the dominant energy release mechanism in cases of quiescent
  coronal activity.

Title: A stochastic model for solar type III bursts
Authors: Isliker, H.; Vlahos, L.; Benz, A. O.; Raoult, A.
Bibcode: 1998A&A...336..371I
Altcode:
  A stochastic model for type III bursts is introduced, discussed,
  and compared to observations. The active region is assumed to be
  inhomogeneous, with a large number of emerging magnetic fibers. At
  their bases, random energy release events take place, in the course of
  which electrons are accelerated, travel along the fibers and eventually
  undergo the bump-on-tail instability. In the non-linear regime, the
  formed Langmuir waves induce strong turbulence in the ambient plasma,
  with secondary electrostatic waves appearing. Wave-wave scattering
  finally leads to the emission of transverse electro-magnetic waves at
  the fundamental and the harmonic of the local plasma-frequency. The
  superposition of the emissions from all the fibers yields a model
  spectrogram for type III bursts (flux as a function of frequency
  and time). Peak-flux distributions of the model are compared to the
  ones of five observations of type III bursts. It turns out that,
  in a statistical sense, the model is largely compatible with the
  observations: the majority of the observations can be considered
  generated by a process which corresponds with the presented model. The
  details of the different sub-processes constituting the model play no
  decisive role concerning the statistical properties of the generated
  spectrograms, to describe them approximately by randomizing the unknown
  elements is sufficient. Therewith, the correspondence of the model
  with the data is not unique. Likewise, intrinsic shortness of observed
  type III events does not allow a strict enough discrimination between
  different possible sub-processes of the model through statistical
  tests. With that, the conclusion is that the observations are compatible
  with a model which assumes (i) a randomly structured active region,
  (ii) a flare-particle acceleration-process which is fragmented into a
  large number of sub-processes, (iii) a distribution of the accelerated
  particles which is a random fraction of the ambient density and of
  power-law form with random index, and (iv) the fragmentary acceleration
  events to occur randomly in time, i.e. the temporal structure of
  type III events to be random, without any correlations between the
  individual bursts.

Title: Solar flare cellular automata interpreted as discretized
    MHD equations
Authors: Isliker, H.; Anastasiadis, A.; Vassiliadis, D.; Vlahos, L.
Bibcode: 1998A&A...335.1085I
Altcode:
  We show that the Cellular Automaton (CA) model for Solar flares of Lu
  and Hamilton (1991) can be understood as the solution to a particular
  partial differential equation (PDE), which describes diffusion in
  a localized region in space if a certain instability threshold is
  met, together with a slowly acting source term. This equation is
  then compared to the induction equation of MHD, the equation which
  governs the energy release process in solar flares. The similarities
  and differences are discussed. We make some suggestions how improved
  Cellular Automaton models might be constructed on the basis of MHD,
  and how physical units can be introduced in the existing respective
  Cellular Automaton models. The introduced formalism of recovering
  equations from Cellular Automata models is rather general and can be
  applied to other situations as well.

Title: Competition Model for the Formation and Evolution of Active
    Regions
Authors: Mylonas, N.; Vlahos, L.; Kluiving, R.
Bibcode: 1998ASPC..155...19M
Altcode: 1998sasp.conf...19M
  No abstract at ADS

Title: Formation of Active Regions: Observations and Theory (Invited
    review)
Authors: Vlahos, L.
Bibcode: 1998ASPC..155....3V
Altcode: 1998sasp.conf....3V
  No abstract at ADS

Title: Fundamental-Harmonic emission in a fibrous jet
Authors: Delouis, J. M.; Raoult, A.; Vlahos, L.
Bibcode: 1998cee..workE..34D
Altcode:
  We propose a type III emission model in the middle corona including
  both fundamental and harmonic radiation from a fibrous medium. We state
  that emitted fundamental and harmonic radiation have the intrinsic
  polarization corresponding to coronal field conditions, i.e.,close
  to 100% for fundamental radiation and close to 0% for harmonic
  radiation. The polarisation ratio of the resulting radiation is then
  due to the proportion of fundamental emission over total emission. This
  allows a new interpretation for spacial and spectral polarization
  properties of type III emission. It also gives a new explanation
  for Fundamental-Harmonic pairs of type III bursts. The Fundamental
  component and the Harmonic component appear as a mix of fundamental
  and harmonic radiation in different proportions. In this frame, most
  of abnomalous observational properties of Fondamental-Harmonic pairs
  (altitudes, frequency ratio, polarization) find a straightforward
  explanation. The model fits the polarisation diagrams established by
  the statistical study of (Dulk and Suzuki, 1990). This model is also
  in agrement with recent interplanetary stereo observations (Hoang
  et al.,1998) which show that type III radiation is emitted at both
  fundamental and harmonic modes.

Title: Electron Acceleration by Random DC Electric Fields
Authors: Anastasiadis, Anastasios; Vlahos, Loukas; Georgoulis,
   Manolis K.
Bibcode: 1997ApJ...489..367A
Altcode:
  We present a global model for the acceleration of electrons in the
  framework of the statistical flare model of Vlahos et al. In this model,
  solar flares are the result of an internal self-organized critical
  (SOC) process in a complex, evolving, and highly inhomogeneous active
  region. The acceleration of electrons is due to localized DC electric
  fields closely related to the energy-release process in the active
  region. Our numerical results for the kinetic energy distribution of
  accelerated electrons show a power-law or an exponential-law behavior,
  depending on the maximum trapping time of the energetic particles
  inside the acceleration volume.

Title: Variability of the Occurrence Frequency of Solar Flares and
    the Statistical Flare
Authors: Georgoulis, M. K.; Vlahos, L.
Bibcode: 1997jena.confE..39G
Altcode:
  Self-Organized Criticality (SOC) embedded in cellular automata
  models has been so far acknowledged as an adequate qualitative way
  of studying the statistical behaviour of flaring activity in solar
  active regions. These models are able of producing robust power
  laws featuring the frequency distributions of the events obtained,
  which are closely consistent with observations of flares, as well
  as much steeper power-law cut-offs, which may indicate the existence
  of the presently unobserved nanoflares. SOC models are based on the
  substantial concept that active regions are driven dissipative nonlinear
  dynamical systems. The role of the external driver is attributed to the
  feedback of magnetic flux that is injected to the system through the
  photospheric boundary and to the random shuffling of the footpoints
  of coronal loops taking place on the upper photosphere. In previous
  numerical studies, the driver used was an infinitesimal perturbation
  acting on localized magnetic topologies due to which avalanche-type
  instabilities were triggered. Furthermore, the resulting power-law
  indices were unique. Recent observations, however, have shown that
  the scaling indices of flares' frequency distributions are not kept
  constant during certain phases of the solar activity, such as the
  154-day periodicity. To tackle this problem we investigate the role of
  the driver used, by introducing a highly variable driving mechanism. We
  show that the variability of the driver induces a respective variability
  in the resulting power-law indices. The variability of the indices
  can be well represented by a linear dependence between them and
  the driver's scaling index for both "nanoflaring" and "flaring"
  activity. Furthermore, a first attempt of connecting the driver with
  certain statistical properties of active regions is introduced. The
  results stand closely in favor of the observations of flaring activity
  during the 154-day periodicity.

Title: Solar and Heliospheric Plasma Physics
Authors: Simnett, George M.; Alissandrakis, Constantine E.; Vlahos,
   Loukas
Bibcode: 1997LNP...489.....S
Altcode: 1997shpp.conf.....S
  This volume brings together theoretical ideas on the plasma physics of
  both hot and dense plasmas in the solar atmosphere and similar physics
  applied to the tenuous and cooler plasmas found in the heliosphere. It
  is complemented by recent observations. Helioseismology covers the
  solar interior and the neutrino problem. Solar and stellar activity
  cycles are addressed. The dynamics of magnetic flux tubes in the solar
  atmosphere and material flows through the chromosphere into the upper
  atmosphere are comprehensively reviewed. Energy release processes and
  the production of energetic particles are important to understanding
  events in the solar atmosphere and to the dynamics of the tenuous
  heliosphere. A glimpse of the future is offered by concluding chapters
  on new ground-based and space instrumentation.

Title: Energy Release in the Solar Corona
Authors: Bastian, Timothy S.; Vlahos, Loukas
Bibcode: 1997LNP...483...68B
Altcode: 1997cprs.conf...68B
  Energy release in the solar corona drives a wide variety of phenomena,
  including flares, filament/prominence eruptions, coronal mass ejections,
  solar particle events, as well as coronal heating and the solar
  wind. The basic physics of these phenomena and their relationship
  to each other remains a vigorous area of inquiry. The Working Group
  on Energy Release at Mont Evray directed its attention to recent
  observational and theoretical developments relevant to flares and
  coronal heating. Particular attention was given to the "fragmentation"
  of energy release in solar flares and its interpretation; to the
  statistics of the flare phenomenon and whether they can be understood in
  terms of "driven dissipative systems"; to quasisteady energy release
  and the problem of coronal heating; and to recent observations of
  flares and related phenomena.

Title: Coronal Heating by Nanoflares and the Variability of the
    Occurence Frequency in Solar Flares
Authors: Georgoulis, Manolis K.; Vlahos, Loukas
Bibcode: 1996ApJ...469L.135G
Altcode:
  It has been proposed that flares in the solar corona may well be
  a result of an internal self-organized critical (SOC) process in
  active regions. We have developed a cellular automaton SOC model
  that simulates flaring activity extending over an active sub-flaring
  background. In the resulting frequency distributions we obtain two
  distinct power laws. That of the weaker events is shorter and much
  steeper (power law with index ~=-3.26) than that of the intermediate
  and large events (power law with index ~=-1.73). The flatter power law
  is in close agreement with observations of flares. Weaker events are
  responsible for ~=90% of the total magnetic energy released, indicating
  a possible connection of nanoflares with coronal heating. Moreover,
  certain mechanisms cause the variability of the resulting indices
  and may provide answers to the problem of the variability of flares'
  occurrence frequency during the solar cycle.

Title: Cellular automaton models of solar flare occurence.
Authors: MacKinnon, A. L.; MacPherson, K. P.; Vlahos, L.
Bibcode: 1996A&A...310L...9M
Altcode:
  We describe a class of stochastic cellular automaton models for the
  occurence of the solar flares. "Flaring elements" of a deliberately
  unspecified nature are supposed to interact. A 1-D version of the
  model, capable of analytical description, conflicts in detail with
  the observations but indicates the quantitative success of such a
  picture. Minimal a priori assumptions are involved. The qualitative
  importance of such a model lies in the arbitrary means of communication
  between flaring elements.

Title: Competetion Model for the Evolution of solar active Regions
Authors: Mylonas, N.; Kluiving, R.; Vlahos, L.; Gergoulis, M.
Bibcode: 1996hell.conf...46M
Altcode:
  No abstract at ADS

Title: Are Flares the Result of a self-organisation Process in
    active Regions?
Authors: Georgoulis, M. K.; Vlahos, L.; Kluiving, R.
Bibcode: 1996hell.conf...52G
Altcode:
  No abstract at ADS

Title: The Acceleration and Transport of energetic Particles inside
    an evolving active Region
Authors: Anastasiadis, A.; Vlahos, L.
Bibcode: 1996hell.conf...59A
Altcode:
  No abstract at ADS

Title: Global Models for the Active Sun and the Statistics of Flares
Authors: Vlahos, L.
Bibcode: 1996ASPC...93..355V
Altcode: 1996ress.conf..355V
  No abstract at ADS

Title: Stochastic particle Acceleration in a strongly turbulent Flow
    of a Jet
Authors: Manolakou, C.; Anastasiadis, A.; Vlahos, L.
Bibcode: 1996hell.conf..445M
Altcode:
  No abstract at ADS

Title: The statistical flare.
Authors: Vlahos, L.; Georgoulis, M.; Kluiving, R.; Paschos, P.
Bibcode: 1995A&A...299..897V
Altcode:
  Solar and stellar flares are interpreted so far as an instability
  of a large scale magnetic neutral sheet. In this article, however,
  we assume that the active region is highly inhomogeneous: a large
  number of magnetic loops are simultaneously present interacting
  and randomly forming discontinuities in many independent points in
  space. These magnetic discontinuities release energy and force weaker
  discontinuities in their neighbourhood to release energy as well. This
  complex dynamical system releases constantly energy in the form of small
  and large scale explosions. Clustering of many discontinuities in the
  same area has the effect of larger scale explosions (flares). This
  type of flare with spatiotemporal fragmentation and clustering in
  small and large scale structures will be called here the statistical
  flare. The statistical flare is simulated using avalanche models
  originally introduced by Bak et al. (1988). Avalanche models applied
  so far to solar flares (Lu &amp; Hamilton 1991) were isotropic (the
  field was distributed equally to the closest neighbours of an unstable
  point). These models simulate relatively large events (microflares and
  flares). Here we introduce a more refined isotropic avalanche model
  as well as an anisotropic avalanche model (energy is distributed only
  among the unstable point and those neighbours that develop gradients
  higher than a critical value). The anisotropic model simulates
  better the smaller events (nanoflares): in contrast to the well-known
  results of the isotropic model (a power law with index ~-1.8 in the
  peak-luminosity distribution), the anisotropic model produces a much
  steeper power law with index ~-3.5. Finally, we introduce a mixed model
  (a combination of isotropic and anisotropic models) which gives rise
  to two distinct power-law regions in the peak-luminosity distribution,
  one with index ~-3.5 accounting for the small events, and one with index
  ~-1.8 accounting for large events. This last model therefore explains
  coronal heating as well as flaring. The three models introduced in this
  paper show length-scale invariant behaviour. Model-dependent memory
  effects are detected in the peak-luminosity time series produced by
  these models.

Title: Beam fragmentation and type III bursts.
Authors: Vlahos, L.; Raoult, A.
Bibcode: 1995A&A...296..844V
Altcode:
  We re-investigate the problem of electron beam propagation and the
  formation of type III bursts, assuming that the corona is inhomogeneous
  and the magnetic field is split in small independent fibers. We
  start by injecting in each fiber a beam with random characteristics
  (beam density, beam energy, etc.) and follow its non linear evolution
  during propagation. We add the contribution of N independent beams in
  each frequency and form the expected spectrum. We discuss the fine
  structure of type III bursts, the decimetric spikes associated with
  type III bursts and the formation of groups of type III bursts.

Title: Particle acceleration in the heliosphere
Authors: Vlahos, L.
Bibcode: 1995HiA....10..307V
Altcode:
  No abstract at ADS

Title: Acceleration and Radiation from a Complex Active Region
Authors: Vlahos, L.
Bibcode: 1995LNP...444..115V
Altcode: 1995cmer.conf..115V
  Active regions are treated in this review as a "paradigm" of a complex
  dynamical system. Active regions are formed by magnetic fibers escaping
  from the turbulent convection zone. Random movements of the feet of the
  fibers in the photosphere and emergence of new magnetic flux from the
  convection zone are responsible for the formation of neutral sheets
  and magnetic discontinuities inside the active region, which are the
  sites for magnetic dissipation. A simple model, based on the scenario
  of self organised criticality, reproduces many of the known flare
  characteristics. The same model is used to provide a large number of
  nanoflares, which can heat the corona. We also show that this complex,
  inhomogeneous active region, is an efficient accelerator and reproduce
  the observed dm spikes and type III bursts.

Title: Particle Acceleration in an Evolving Active Region by an
    Ensemble of Shock Waves
Authors: Anastasiadis, Anastasios; Vlahos, Loukas
Bibcode: 1994ApJ...428..819A
Altcode:
  We present a model for the acceleration and transport of energetic
  particles (electrons and ions) inside an active region. We propose
  that the agent for the acceleration is an ensemble of oblique shock
  waves, generated inside an evolving and constantly changing active
  region. The acceleration is based on the 'shock drift' mechanism, using
  the adiabatic treatment. The high-energy particles are losing energy via
  Coulomb collisions and radiation. We calculate the energy distribution
  of the particles, their acceleration time, and their maximum energy
  as a function of the number of shock waves present. The high-energy
  particles are transported inside a chaotic magnetic field and are
  reflected randomly when they meet a magnetic mirror point. Finally we
  compare our numerical results with the observations.

Title: Foreword
Authors: van den Oord, Bert; Kuijpers, Jan; Kuperus, Max; Benz, A. O.;
   Brown, J. C.; Einaudi, G.; Kuperus, M.; Raadu, M. A.; Trottet, G.;
   van den Oord, G. H. J.; Vlahos, L.; Zheleznyakov, V. V.; Wijburg,
   Marion; Fletcher, Lyndsay; Volwerk, Martin
Bibcode: 1994SSRv...68D..17V
Altcode:
  No abstract at ADS

Title: Theory of fragmented energy release in the Sun
Authors: Vlahos, Loukas
Bibcode: 1994SSRv...68...39V
Altcode:
  The magnetic energy released inside an active region is closely related
  to its formation and evolution. Following the evolution of a collection
  of flux tubes inside the convection zone and above the photosphere we
  can show that many nonlinear structures (current sheets, shock waves,
  double layers etc.) are formed. We propose in this review that coronal
  heating, flares and particle acceleration are due to the interaction of
  the plasma with these nonlinear structures. Approaching active regions
  as a driven complex dynamical system we can show that several coherent
  ensembles of the nonlinear structures will appear spontaneously. The
  statistical analysis of these structures is a major problem in solar
  physics. We can also show that many observed large scale structures
  are the result of the convolution of non-observable fragmentation in
  the energy release process.

Title: Galactic Dynamics and N-Body Simulations
Authors: Contopoulos, G.; Spyrou, N. K.; Vlahos, L.
Bibcode: 1994LNP...433.....C
Altcode: 1994gdnb.conf.....C
  This book provides an in-depth coverage of modern research on dynamical
  systems. The first part discusses stellar dynamics, integrable systems,
  the transition to chaos and instabilities in stellar dynamics as well
  as the dynamics of spiral galaxies. Models are given and compared
  with observations. The second part is devoted to the direct method
  of N-body simulations, to gas dynamics simulations and to galaxy
  formation. Special care is taken to give to a pedagogical presentation
  of the material which makes this a unique text well suited for graduate
  courses in astrophysics.

Title: Filamentation of magnetic structures and particle acceleration
    in solar and stellar flares
Authors: Vlahos, Loukas
Bibcode: 1993AdSpR..13i.161V
Altcode: 1993AdSpR..13..161V
  We review models for the evolution and energy release of active
  region magnetic fields. We propose that turbulent photospheric motions
  will break the active region magnetic field in small fibers (current
  carrying magnetic filaments) and we address the possibility that this
  type of magnetic topology may become the host of thousands of neutral
  sheets. We have subsequently analyzed the acceleration and transport
  of energetic particles in such an environment. Standard techniques
  such as stochastic or shock acceleration, E-field acceleration or
  coherent acceleration are reviewed on the basis of a ``statistical
  flare'' model, where many explosions are organised (self-organised
  when they reach a critical stage or externally driven by emerging flux
  or large scale photospheric flows around filaments) to create a flare
  (micro-flare or large flare).

Title: Particle acceleration by multiple shocks at the hot spots of
    extragalatic radio sources
Authors: Anastasiadis, A.; Vlahos, L.
Bibcode: 1993A&A...275..427A
Altcode:
  We present a model for the acceleration of energetic electrons by
  an ensemble of oblique shock waves at the hot spots of extended
  extragalactic radio sources. The energization of the electrons
  is based on the "shock drift" acceleration mechanism, using the
  adiabatic treatment, and electrons are subject to synchrotron losses
  as they travel between the shock fronts. We calculate numerically the
  energy distribution of electrons and the corresponding intensity of
  the radiation produced. We compare our results with the analytical
  solution of the Fokker-Planck equation. Our numerical and analytical
  results agree well with the existing observations.

Title: Transport Phenomena in Solar and Stellar Active Regions
Authors: Vlahos, L.
Bibcode: 1993sdtp.conf..235V
Altcode:
  No abstract at ADS

Title: High Energy Emission from Normal Stars
Authors: Vlahos, L.
Bibcode: 1993LNP...418..129V
Altcode: 1993ghea.conf..129V
  Introduction Energy Flow and Particle Acceleration Basic Concepts
  Spontaneous Emission Bremsstrahlung Emission Cyclotron and Synchrotron
  Emission Collective Plasma Emission Plasma Radiation Electron Cyclotron
  Maser Instability Observations Hard X-Ray Emission Radio Observations
  Summary and Conclusions References

Title: On the efficiency of electron cyclotron maser instability in
    solar flares
Authors: MacKinnon, A.; Vlahos, L.; Vilmer, N.
Bibcode: 1992A&A...256..613M
Altcode:
  We describe a simple model, designed to estimate the efficiency of
  the electron cyclotron maser (ECM) instability inside a magnetic
  trap. The emphasis in this model is on the energy loss associated
  with the formation of the loss cone distribution, rather than on the
  microscopic plasma physics. We find that the net radiation efficiency
  is low. Repeated mirroring does not greatly enhance the intrinsic
  efficiency, because of the energy lost from the corona in precipitating
  electrons. In consequence, absorption of ECM radiation is unlikely to
  be an important factor in understanding soft X-ray observations.

Title: Particle acceleration inside a 'gas' of shock waves
Authors: Anastasiadis, A.; Vlahos, L.
Bibcode: 1991A&A...245..271A
Altcode:
  A process by which shock waves are formed in jet flows or during
  supernovae explosions is presented. Particular attention is given to
  the short time scale evolution of N-shock wave-particle interaction. It
  is found that most of the energy released by the 'thermal' explosions
  will return to thermal energy via shock-shock interactions.

Title: An injection model for type III/V bursts in solar flares
Authors: Raoult, A.; Mangeney, A.; Vlahos, L.
Bibcode: 1990A&A...233..229R
Altcode:
  A possible interpretation of the injection of electrons and the
  correlation of hard X-ray and type III/V radio emission is presented. A
  possible model is also presented of the nonlinear excitation of ion
  sound fluctations from type III beams and the streaming of low-energy
  superthermal electrons inside a turbulent plasma. It is suggested that
  the high-energy electron stream, which generates type III bursts and the
  spiky X-ray component, excites intense plasma waves which nonlinearly
  drive ion density fluctuations. These fluctuations enhance the collision
  frequency of the streaming low-energy particles and force them to form
  a positive slope. This allows the 30 keV hot plasma to excite plasma
  waves in the same frequency range as type III bursts and to generate
  type V emission.

Title: Energetic Particles in Solar Flares: Observations Modeling
    and Acceleration Processes (Extended Abstract)
Authors: Trottet, G.; Vlahos, L.
Bibcode: 1990PDHO....7..184T
Altcode: 1990dysu.conf..184T; 1990ESPM....6..184T
  No abstract at ADS

Title: Particle Acceleration in Solar Flares
Authors: Vlahos, Loukas
Bibcode: 1989SoPh..121..431V
Altcode: 1989IAUCo.104..431V
  Particle acceleration during solar flares is a complex process where the
  main `actors' (Direct (D.C.) or turbulent electric fields) are hidden
  from us. It is easy to construct a successful particle accelertion
  model if we are allowed to impose on the flaring region arbitrary
  conditions (e.g., strength and scale length of the D.C. or turbulent
  electric fields), but then we have not solved the acceleration problem;
  we have simply re-defined it. We outline in this review three recent
  observations which indicate that the following physical processes may
  happen during solar flares: (1) Release of energy in a large number
  of microflares; (2) short time-scales; (3) small length scales;
  and (4) coherent radiation and acceleration sources. We propose
  that these new findings force us to reformulate the acceleration
  process inside a flaring active region assuming that a large number of
  reconnection sites will burst almost simultaneously. All the well-known
  acceleration mechanisms (electric fields, turbulent fields, shock waves,
  etc.) reviewed briefly here, can be used in a statistical model where
  each particle is gaining energy through its interaction with many
  small reconnection sites.

Title: Particle acceleration.
Authors: Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.;
   Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.;
   Ellison, D.; Evenson, P.; Forrest, D. J.; Holman, G.; Kane, S. R.;
   Kaufmann, P.; Kundu, M. R.; Lin, R. P.; MacKinnon, A.; Nakajima,
   H.; Pesses, M.; Pick, M.; Ryan, J.; Schwartz, R. A.; Smith, D. F.;
   Trottet, G.; Tsuneta, S.; van Hoven, G.
Bibcode: 1989epos.conf..127V
Altcode:
  Contents: 1. Introduction. 2. Phenomena associated with
  mildly-relativistic electrons. 3. Phenomena associated with ions and
  relativistic electrons in solar flares. 4. Theoretical studies of
  particle acceleration. 5. Achievements - outstanding questions.

Title: Particle acceleration and plasma heating at collisionless
    shocks in solar flares.
Authors: Cargill, P. J.; Vlahos, L.
Bibcode: 1989sasf.confP.325C
Altcode: 1989IAUCo.104P.325C; 1988sasf.conf..325C
  Recent observations suggest that the energy release in solar flares
  may occur in many small bursts. If these bursts give rise to plasma
  heating, a large number of collisionless shocks will be generated. These
  shocks can individually heat plasma and accelerate particles, but the
  interaction of particles with many shocks as well as of shocks with
  each other can give rise to further heating and acceleration.

Title: Dynamics of sub-relativistic electron beams in magnetic traps -
    A model for solar N-bursts
Authors: Hillaris, A.; Alissandrakis, C. E.; Vlahos, L.
Bibcode: 1988A&A...195..301H
Altcode:
  The dynamic evolution of mildly relativistic electrons (10 - 100 keV)
  injected into a model magnetic trap is studied numerically, using
  the drift approximation. Wave-particle interactions are neglected,
  since the beam plasma system is shown to be non-linearly decoupled
  in the range of parameters used in this study. The results from the
  simulation are used to interpret certain observational characteristics
  of the N-bursts observed by the Nançay radio spectrograph. N-bursts
  are believed to be the first direct radio evidence for mirror effects
  in solar magnetic loops.

Title: Narrow-bandwidth radiation processes in space and astrophysical
plasmas: a review.
Authors: Vlahos, L.
Bibcode: 1988imdk.conf..411V
Altcode:
  Energetic electrons "injected" or accelerated inside a dipole magnetic
  field radiate broad band electromagnetic radiation due to their fast
  gyration around the magnetic field (synchrotron emission). It is well
  known that trapped particles form two classes of unstable velocity
  distributions inside the magnetic trap: (1) a beam velocity distribution
  and (2) a loss cone velocity distribution. The author reviews the plasma
  radiation signatures from these two velocity distributions inside
  strongly magnetised plasmas and shows that a highly polarised narrow
  bandwidth signal should be expected from these magnetic traps. Such
  narrow bandwidth emission is observed in all known magnetic traps
  in space and astrophysical plasmas (e.g. Earth, Jupiter, solar and
  stellar atmospheres, pulsars, etc).

Title: Collisionless shock formation and the prompt acceleration of
    solar flare ions
Authors: Cargill, P. J.; Goodrich, C. C.; Vlahos, L.
Bibcode: 1988A&A...189..254C
Altcode:
  The formation mechanisms of collisionless shocks in solar flare plasmas
  are investigated. The priamry flare energy release is assumed to
  arise in the coronal portion of a flare loop as many small regions
  or 'hot spots' where the plasma beta locally exceeds unity. One
  dimensional hybrid numerical simulations show that the expansion of
  these 'hot spots' in a direction either perpendicular or oblique to
  the ambient magnetic field gives rise to collisionless shocks in a few
  Omega(i), where Omega(i) is the local ion cyclotron frequency. For
  solar parameters, this is less than 1 second. The local shocks are
  then subsequently able to accelerate particles to 10 MeV in less
  than 1 second by a combined drift-diffusive process. The formation
  mechanism may also give rise to energetic ions of 100 keV in the
  shock vicinity. The presence of these energetic ions is due either
  to ion heating or ion beam instabilities and they may act as a seed
  population for further acceleration. The prompt acceleration of ions
  inferred from the Gamma Ray Spectrometer on the Solar Maximum Mission
  can thus be explained by this mechanism.

Title: Evolution of the Axial Electron Cyclotron Maser Instability,
    with Applications to Solar Microwave Spikes
Authors: Vlahos, Loukas; Sprangle, Phillip
Bibcode: 1987ApJ...322..463V
Altcode:
  The nonlinear evolution of cyclotron radiation from streaming and
  gyrating electrons in an external magnetic field is analyzed. The
  nonlinear dynamics of both the fields and the particles are treated
  fully relativistically and self-consistently. The model includes
  a background plasma and electrostatic effects. The analytical
  and numerical results show that a substantial portion of the beam
  particle energy can be converted to electromagnetic wave energy at
  frequencies far above the electron cyclotron frequency. In general,
  the excited radiation can propagate parallel to the magnetic field
  and, hence, escape gyrothermal absorption at higher cyclotron
  harmonics. The high-frequency Doppler-shifted cyclotron instability
  can have saturation efficiencies far higher than those associated with
  well-known instabilities of the electron cyclotron maser type. Although
  the analysis is general, the possibility of using this model to explain
  the intense radio emission observed from the sun is explored in detail.

Title: Electron Cyclotron Harmonic Wave Acceleration
Authors: Karimabadi, H.; Menyuk, C. R.; Sprangle, P.; Vlahos, L.
Bibcode: 1987ApJ...316..462K
Altcode:
  A nonlinear analysis of particle acceleration in a finite bandwidth,
  obliquely propagating electromagnetic cyclotron wave is presented. It
  has been suggested by Sprangle and Vlahos in 1983 that the narrow
  bandwidth cyclotron radiation emitted by the unstable electron
  distribution inside a flaring solar loop can accelerate electrons
  outside the loop by the interaction of a monochromatic wave propagating
  along the ambient magnetic field with the ambient electrons. It is
  shown here that electrons gyrating and streaming along a uniform, static
  magnetic field can be accelerated by interacting with the fundamental
  or second harmonic of a monochromatic, obliquely propagating cyclotron
  wave. It is also shown that the acceleration is virtually unchanged when
  a wave with finite bandwidth is considered. This acceleration mechanism
  can explain the observed high-energy electrons in type III bursts.

Title: Electron Cyclotron Maser Emission from Solar Flares
Authors: Vlahos, Loukas
Bibcode: 1987SoPh..111..155V
Altcode:
  Energetic electrons, with energies 10-100 keV, accelerated during
  the impulsive phase of solar flares, sometimes encounter increasing
  magnetic fields as they stream towards the chromosphere. A consequence
  of the conservation of their magnetic moment is that the electrons with
  large initial pitch angle will be reflected at different heights from
  the atmosphere. Energetic electrons reflected below the transition
  zone will lose most of their energy to collisions and will never
  return to the corona. Thus, electrons reflected above the transition
  zone form a loss-cone velocity distribution which can be unstable to
  Electron Cyclotron Maser (ECM). The interaction of quasi-perpendicular
  shocks with the ambient coronal plasma will form a `ring' or `hollow
  beam' velocity distribution upstream of the shock. `Ring' velocity
  distributions are also unstable to the ECM instability. A review of the
  recent results on the theory of ECM will be presented. We will focus
  our discussion on the questions: (a) What are the characteristics of
  the linear growth rate of the ECM during solar flares? (b) How does
  the ECM saturate and what is its efficiency? (c) How does the ECM
  generated radiation modify the flare environment? Finally we will
  review the outstanding questions in the theory of ECM and we will
  relate the theoretical predictions to current observations.

Title: Phenomena Associated with Ions and Relativistic Electrons
Authors: Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.;
   Allisandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.;
   Ellison, D.; Evenson, P.; Forrest, D. J.; Holman, G.; Kane, S. R.;
   Kaufmann, P.; Kundu, M. R.; Lin, R. P.; MacKinnon, A.; Nakajima,
   H.; Pesses, M.; Pick, M.; Ryan, J.; Schwartz, R. A.; Smith, D. F.;
   Trottet, G.; Tsuneta, S.; van Hoven, G.
Bibcode: 1986epos.conf.2.30V
Altcode: 1986epos.confB..30V
  No abstract at ADS

Title: Modeling of ion acceleration through drift and diffusion at
    interplanetary shocks
Authors: Decker, R. B.; Vlahos, L.
Bibcode: 1986JGR....9113349D
Altcode:
  We describe a test particle simulation designed to study energetic
  charged particle acceleration at oblique fast-mode shocks when magnetic
  fluctuations exist upstream and downstream of the shock. The technique
  consists of integrating along exact particle orbits in a system where
  the angle θ<SUB>1</SUB> between the shock normal and mean upstream
  magnetic field, the level of magnetic fluctuations, and the energy
  of injected particles can assume a range of values. This allows us to
  study time-dependent shock acceleration under conditions not amenable
  to analytical techniques. To illustrate the capability of the numerical
  mode, we consider proton acceleration under conditions appropriate for
  interplanetary shocks near 1 AU, including large-amplitude transverse
  magentic fluctuations derived from power spectra of both ambient and
  shock associated MHD waves. <P />With all other parameters held fixed,
  protons injected at θ<SUB>1</SUB>=0° and θ<SUB>1</SUB>=60° shocks
  are accelerated from 10 keV to ~100 keV and ~1 MeV, repectively, within
  300 gyroperiods by a combination of the shock drift and first-order
  Fermi processes. The energy spectrum downstream of the 60° shock
  can be fit with two power laws, with spectral exponent γ=1.7 from 10
  keV to ~80 keV and γ=2.6 from ~ 80 keV to 800 keV. Results are also
  presented for the situation where the variance and upstream extent of
  the shock-associated waves at the 60° shock are reduced relative to
  the values used at the 0° shock.

Title: Mechanisms for Particle Accleration in Flares
Authors: Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.;
   Allisandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.;
   Ellison, D.; Evenson, P.; Forrest, D. J.; Holman, G.; Kane, S. R.;
   Kaufmann, P.; Kundu, M. R.; Lin, R. P.; MacKinnon, A.; Nakajima,
   H.; Pesses, M.; Pick, M.; Ryan, J.; Schwartz, R. A.; Smith, D. F.;
   Trottet, G.; Tsuneta, S.; van Hoven, G.
Bibcode: 1986epos.conf.2.42V
Altcode: 1986epos.confB..42V
  No abstract at ADS

Title: Phenomena Associated with Mildly Relativistic Electrons
Authors: Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.;
   Allisandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.;
   Ellison, D.; Evenson, P.; Forrest, D. J.; Holman, G.; Kane, S. R.;
   Kaufmann, P.; Kundu, M. R.; Lin, R. P.; MacKinnon, A.; Nakajima,
   H.; Pesses, M.; Pick, M.; Ryan, J.; Schwartz, R. A.; Smith, D. F.;
   Trottet, G.; Tsuneta, S.; van Hoven, G.
Bibcode: 1986epos.conf..2.2V
Altcode: 1986epos.confB...2V
  No abstract at ADS

Title: Numerical Studies of Particle Acceleration at Turbulent,
    Oblique Shocks with an Application to Prompt Ion Acceleration during
    Solar Flares
Authors: Decker, R. B.; Vlahos, L.
Bibcode: 1986ApJ...306..710D
Altcode:
  In this paper we address the problem of charged particle acceleration
  at oblique, fast-mode collisionless MHD shock waves when magnetic
  turbulence exists in the regions upstream and downstream of the
  shock. Specifically, we consider how the acceleration rate depends upon
  the angle θ<SUB>1</SUB> between the shock normal and the mean upstream
  magnetic field. To handle the general situation where θ<SUB>1</SUB>,
  the turbulence level, the shock strength, and the energy of injected
  particles can assume a range of values, we perform fully relativistic,
  test particle simulations that involve integrating along particle
  phase space orbits in the shock turbulence system. As an application
  of the numerical code, we study proton acceleration at shocks
  under conditions appropriate to the lower solar corona to simulate
  prompt ion acceleration during solar flares. Particles undergo shock
  acceleration through a combination of the shock drift and first-order
  Fermi processes. For protons injected at 100 keV and left in the system
  for 500 gyroperiods (∼ 7 ms in a 50 G magnetic field) we obtain the
  following results: (1) the percentage of protons accelerated above
  10 MeV within 7 ms increases with increasing θ<SUB>1</SUB>, from 0%
  at θ<SUB>1</SUB> = 0° to a maximum of 9% at θ<SUB>1</SUB>= 60°
  (2) the case θ<SUB>1</SUB> = 75° produces the largest, most rapid
  energy gains, with ∼1% of the protons accelerated above 50 MeV;
  (3) for 45° &lt; θ<SUB>1</SUB> &lt; 75° , a separate proton
  population with energies between 100 keV and 10 MeV is produced
  during a superfast acceleration phase lasting only ∼ 10 gyroperiods
  (∼ 100 μs) after injection; (4) we compare the peak energy reached
  at O = 0 and energy spectrum produced at θ<SUB>1</SUB> = 75° with
  predictions from theoretical models, and find reasonable agreement,
  although discrepancies do exist. We discuss the implications of the
  numerical results as they pertain to time constraints and collisional
  loss processes during shock acceleration in the solar corona.

Title: Timescales for Shock Formation in Collisionless Plasmas
Authors: Cargill, P. J.; Goodrich, C. C.; Vlahos, L.
Bibcode: 1986BAAS...18..710C
Altcode:
  No abstract at ADS

Title: Nonlinear analysis of a relativistic beam-plasma cyclotron
    instability
Authors: Sprangle, P.; Vlahos, L.
Bibcode: 1986PhRvA..33.1261S
Altcode:
  A self-consistent set of nonlinear and relativistic wave-particle
  equations are derived for a magnetized beam-plasma system interacting
  with electromagnetic cyclotron waves. In particular, the high-frequency
  cyclotron mode interacting with a streaming and gyrating electron
  beam within a background plasma is considered in some detail. This
  interaction mode may possibly find application as a high-power source
  of coherent short-wavelength radiation for laboratory devices. The
  background plasma, although passive, plays a central role in this
  mechanism by modifying the dielectric properties in which the magnetized
  electron beam propagates. For a particular choice of the transverse
  beam velocity (i.e., the speed of light divided by the relativistic mass
  factor), the interaction frequency equals the nonrelativistic electron
  cyclotron frequency times the relativistic mass factor. For this choice
  of transverse beam velocity the detrimental effects of a longitudinal
  beam velocity spread is virtually removed. Power conversion efficiencies
  in excess of 18 percent are both analytically calculated and obtained
  through numerical simulations of the wave-particle equations. The
  quality of the electron beam, degree of energy and pitch angle spread,
  and its effect on the beam-plasma cyclotron instability is studied.

Title: Particle acceleration.
Authors: Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.;
   Allisandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.;
   Ellison, D.; Evenson, P.; Forrest, D. J.; Holman, G.; Kane, S. R.;
   Kaufmann, P.; Kundu, M. R.; Lin, R. P.; MacKinnon, A.; Nakajima,
   H.; Pesses, M.; Pick, M.; Ryan, J.; Schwartz, R. A.; Smith, D. F.;
   Trottet, G.; Tsuneta, S.; van Hoven, G.
Bibcode: 1986NASCP2439....2V
Altcode:
  Contents: 1. Introduction. 2. Phenomena associated with
  mildly-relativistic electrons: soft and hard X-ray source structure,
  location and development, microwave source structure, location and
  development, time structures and time delays in radio and hard X-rays,
  microwave rich flares, decimetric - metric observations and comparison
  with X-ray observations, discussion of models for X-ray and microwave
  emission. 3. Phenomena associated with ions and relativistic electrons:
  gamma-ray observations, neutron observations, implications of gamma-ray
  and neutron observations, interplanetary charged-particle observations,
  acceleration mechanisms. 4. Mechanisms for particle acceleration
  in flares: particle acceleration in reconnecting magnetic fields,
  electron acceleration along the magnetic field with sub-Dreicer electric
  fields, lower hybrid waves, Fermi acceleration and MHD turbulence,
  shock acceleration, acceleration of electrons by intense radio waves,
  preferential acceleration of heavy ions. 5. Achievements - outstanding
  questions.

Title: Theoretical studies on rapid fluctuations in solar flares.
Authors: Vlahos, Loukas
Bibcode: 1986NASCP2449..455V
Altcode: 1986rfsf.nasa..455V
  Rapid fluctuations in the emission of solar bursts may have many
  different origins. In two separate studies (Vlahos, Sharma, and
  Papadopulos, 1983, see Abstr. 34.073.209; Vlahos and Rowland, 1984,
  see Abstr. 38.073.055) the conditions for rapid fluctuations in solar
  flare driven emissions are analysed.

Title: Energetic Ion Acceleration at Collisionless Shocks
Authors: Decker, R. B.; Vlahos, L.
Bibcode: 1985ICRC....4..166D
Altcode: 1985ICRC...19d.166D
  An example is presented from a test particle simulation designed to
  study ion acceleration at oblique turbulent shocks. For conditions
  appropriate at interplanetary shocks near 1 AU, it is found that a
  shock with theta<SUB>B</SUB> n = 60 deg is capable of producing an
  energy spectrum extending from 10 keV to approx. 1 MeV in approx 1
  hour. In this case total energy gains result primarily from several
  separate episodes of shock drift acceleration, each of which occurs
  when particles are scattered back to the shock by magnetic fluctuations
  in the shock vicinity.

Title: Prompt acceleration of ions by oblique turbulent shocks in
    solar flares.
Authors: Decker, R. B.; Vlahos, L.
Bibcode: 1985ICRC....4...10D
Altcode: 1985ICRC...19d..10D
  Solar flares often accelerate ions and electrons to relativistic
  energies. The details of the acceleration process are not well
  understood, but until recently the main trend was to divide the
  acceleration process into two phases. During the first phase elctrons
  and ions are heated and accelerated up to several hundreds of keV
  simultaneously with the energy release. These mildly relativistic
  electrons interact with the ambient plasma and magnetic fields
  and generate hard X-ray and radio radiation. The second phase,
  usually delayed from the first by several minutes, is responsible for
  accelerating ions and electrons to relativistic energies. Relativistic
  electrons and ions interact with the solar atmosphere or escape from
  the Sun and generate gamma ray continuum, gamma ray line emission,
  neutron emission or are detected in space by spacecraft. In several
  flares the second phase is coincident with the start of a type 2 radio
  burst that is believed to be the signature of a shock wave. Observations
  from the Solar Maximum Mission spacecraft have shown, for the first
  time, that several flares accelerate particles to all energies nearly
  simultaneously. These results posed a new theoretical problem: How fast
  are shocks and magnetohydrodynamic turbulence formed and how quickly
  can they accelerate ions to 50 MeV in the lower corona? This problem
  is discussed.

Title: Electron cyclotron maser instability in the solar corona -
    The role of superthermal tails
Authors: Vlahos, L.; Sharma, R. R.
Bibcode: 1985ApJ...290..347V
Altcode:
  The effect of a superthermal component of electrons on the
  loss-cone-driven electron cyclotron maser instability is analyzed. It
  is found that for a superthermal tail with temperature about 10 KeV,
  the first harmonic (X- and O-mode) is suppressed for n(t)/n(r) of about
  1 (n/t/ and n/r/ are the densities of superthermal tail and loss-cone
  electrons) and the second harmonic (X- and O-modes) is suppressed
  for n(t)/n(r) less than about 0.1. A qualitative discussion on the
  formation of superthermal tails is presented and it is suggested that
  superthermal tails play an important role on the observed or available
  power, at microwave frequencies, from the electron cyclotron maser
  instability in the solar corona.

Title: Return currents in solar flares - Collisionless effects
Authors: Rowland, H. L.; Vlahos, L.
Bibcode: 1985A&A...142..219R
Altcode:
  If the primary, precipitating electrons in a solar flare are unstable to
  beam plasma interactions, it is shown that strong Langmuir turbulence
  can seriously modify the way in which a return current is carried
  by the background plasma. In particular, the return (or reverse)
  current will not be carried by the bulk of the electrons, but by a
  small number of high velocity electrons. For beam/plasma densities
  &gt;10<SUP>-3</SUP>, this can reduce the effects of collisions on the
  return current. For higher density beams where the return current could
  be unstable to current driven instabilities, the effects of strong
  turbulence anomalous resistivity is shown to prevent the appearance
  of such instabilities. Again in this regime, how the return current
  is carried is determined by the beam generated strong turbulence.

Title: The coalescence instability in solar flares
Authors: Tajima, T.; Brunel, F.; Sakai, J. -I.; Vlahos, L.; Kundu,
   M. R.
Bibcode: 1985IAUS..107..197T
Altcode:
  The nonlinear coalescence instability of current carrying solar loops
  can explain many of the characteristics of the solar flares such as
  their impulsive nature, heating and high energy particle acceleration,
  amplitude oscillations of electromagnetic and emission as well as the
  characteristics of two-dimensional microwave images obtained during
  a flare. The plasma compressibility leads to the explosive phase of
  loop coalescence and its overshoot results in amplitude oscillations
  in temperatures by adiabatic compression and decompression. It is
  noted that the presence of strong electric fields and super-Alfvenic
  flows during the course of the instability play an important role in
  the production of nonthermal particles. A qualitative explanation on
  the physical processes taking place during the nonlinear stages of
  the instability is given.

Title: Shock drift acceleration in the presence of waves
Authors: Decker, R. B.; Vlahos, L.
Bibcode: 1985JGR....90...47D
Altcode:
  Charged particle acceleration via the shock drift mechanism at
  quasi-perpendicular shocks has generally been analyzed by assuming
  uniform, time-independent conditions at and near the shock. We present
  results from a model designed to study how the shock drift mechanism
  is modified when wave activity is included in the shock's upstream and
  downstream vicinities. The technique involves numerically following
  test particle trajectories in the wave-shock system for predefined
  wave fields. In order to compare these results with those obtained
  in the scatter-free (i.e., nonwave) case, we restricted particles
  to a single shock encounter, which is here defined as the period
  during which the particle remains within a gyrodiameter of the
  shock. As a particular example, we injected ensembles of ions into a
  system consisting of a quasi-perpendicular shock moving through the
  interplanetary spectrum of ambient Alfvén waves. As compared with a
  single encounter in the scatter-free limit, the inclusion of waves (1)
  increases particle transmission through the shock, (2) produces broader
  energy distributions for reflected and transmitted particles, with
  high-energy tails at energies several times the maximum energy obtained
  in the scatter-free case and (3) reduces anisotropies, particularly of
  reflected particles, but does not eliminate them. Also, for the range
  of energies studied, it was found that the approximate invariance of
  the magnetic moment for particle interactions with quasi-perpendicular
  shocks is no longer valid when waves are present.

Title: Collisionless effects on beam-return current systems in
    solar flares
Authors: Vlahos, L.; Rowland, H. L.
Bibcode: 1985IAUS..107..521V
Altcode:
  A theoretical study of the beam-return current system (BRCS) in solar
  flares shows that the precipitating electrons modify the way in which
  the return current (RC) is carried by the background plasma. In
  particular it is found that the RC is not carried by the bulk of
  the electrons but by a small number of high-velocity electrons. For
  beam/plasma densities exceeding approximately 0.001, this can reduce
  the effects of collisions and heating by the RC. For higher-density
  beams, where the RC could be unstable to current-driven instabilities,
  the effects of strong turbulence anomalous resistivity prevent the
  appearance of such instabilities. The main conclusion is that the
  BRCS is interconnected, and that the beam-generated strong turbulence
  determines how the RC is carried.

Title: Electron precipitation in solar flares - Collisionless effects
Authors: Vlahos, L.; Rowland, H. L.
Bibcode: 1984A&A...139..263V
Altcode:
  A large fraction of the electrons which are accelerated during the
  impulsive phase of solar flares stream towards the chromosphere and
  are unstable to the growth of plasma waves. The linear and non-linear
  evolution of plasma waves as a function of time is analyzed with the
  use of a set of rate equations that follow in time the nonlinearly
  coupled system of plasma waves - ion fluctuations. As an outcome
  of the fast transfer of wave energy from the beam to the ambient
  plasma, non-thermal electron tails are formed which can stabilize the
  anomalous Doppler resonance instability that is responsible for the
  pitch angle scattering of the beam electrons. The authors estimate the
  non-collisional losses of the precipitating electrons and discuss the
  observational implications of their results.

Title: Predictions of lithium interactions with earth's bow shock
    in the presence of wave activity
Authors: Decker, R. B.; Lui, A. T. Y.; Vlahos, L.
Bibcode: 1984JGR....89.7331D
Altcode:
  The results of a test-particle simulation studying the movement
  of a lithium tracer ion injected upstream of the bow shock are
  reported. Wave activity consists of parallel and antiparallel
  propagating Alfven waves characterized by a frequency power spectrum
  within a frequency or range of amplitudes defined separately in the
  upstream and downstream regions. The results show that even a moderate
  level of wave activity can substantially change the results obtained
  in the absence of waves. Among the effects observed are: (1) increased
  ion transmission; (2) both the average energy gain and spread about
  the average are increased for transmitted and reflected particles;
  (3) the average final pitch angle for transmitted particles tends to
  90 deg, and the spread of reflected particles is reduced; and (4)
  the spatial dispersion of the ions on the bow shock after a single
  encounter is increased.

Title: Comparative study of the loss cone-driven instabilities in
    the low solar corona
Authors: Sharma, R. R.; Vlahos, L.
Bibcode: 1984ApJ...280..405S
Altcode:
  A comparative study of the loss cone-driven instabilities in the
  low solar corona is undertaken. The instabilities considered are the
  electron cyclotron maser, the whistler, and the electrostatic upper
  hybrid. It is shown that the first-harmonic extraordinary mode of the
  electron cyclotron maser instability is the fastest growing mode for
  strong magnetized plasma (the ratio of plasma frequency to cyclotron
  frequency being less than 0.35). For values of the ratio between 0.35
  and 1.0, the first-harmonic ordinary mode of the electron cyclotron
  maser instability dominates the emission. For ratio values greater
  than 1.0, no direct electromagnetic radiation is expected since
  other instabilities, which do not escape directly, saturate the
  electron cyclotron maser (the whistler or the electrostatic upper
  hybrid waves). It is also shown that the second-harmonic electron
  cyclotron maser emission never grows to an appreciable level. Thus, it
  is suggested that the electron cyclotron maser instability can be the
  explanation for the escape of the first harmonic from a flaring loop.

Title: Dynamic Development of Run-Away Tails in Flares
Authors: Moghaddam-Taaheri, E.; Vlahos, L.; Rowland, H. L.;
   Papadopoulos, K.
Bibcode: 1984BAAS...16..536M
Altcode:
  No abstract at ADS

Title: Particle Acceleration in Flares
Authors: Vlahos, L.
Bibcode: 1984BAAS...16..511V
Altcode:
  No abstract at ADS

Title: Electron Cyclotron Maser Instability: The Role of Superthermal
    Tails
Authors: Sharma, R. R.; Vlahos, L.
Bibcode: 1984BAAS...16..536S
Altcode:
  No abstract at ADS

Title: Collisionless Effects on Beam/Return Current Systems in Flares
Authors: Rowland, H. L.; Vlahos, L.
Bibcode: 1984BAAS...16R.544R
Altcode:
  No abstract at ADS

Title: Flare Induced Stimulated Electron Cyclotron Radiation
Authors: Sprangle, P.; Vlahos, L.; Papadopoulos, K.
Bibcode: 1984BAAS...16R.524S
Altcode:
  No abstract at ADS

Title: Particle acceleration.
Authors: Rosner, R.; Chupp, E. L.; Gloeckler, G.; Gorney, D. J.;
   Krimigis, S. M.; Mok, Y.; Ramaty, R.; Swift, D. W.; Vlahos, L.;
   Zweibel, E. G.
Bibcode: 1984NASRP1120....2R
Altcode:
  Contents: 1. Introduction. 2. Phenomenology: Solar flares. Acceleration
  processes in the interplanetary medium. Magnetospheric and
  ionospheric observations. Particle acceleration outside the solar
  system. 3. Theoretical particle acceleration mechanisms: Adiabatic
  compression, magnetic pumping, and diffusion. Acceleration in
  direct electric fields. Stochastic acceleration. Shock particle
  acceleration. Coherent wave acceleration. Injection. 4. The remaining
  questions.

Title: Stochastic three-wave interaction in flaring solar loops
Authors: Vlahos, L.; Sharma, R. R.; Papadopoulos, K.
Bibcode: 1983ApJ...275..374V
Altcode:
  A model is proposed for the dynamic structure of high-frequency
  microwave bursts. The dynamic component is attributed to beams of
  precipitating electrons which generate electrostatic waves in the
  upper hybrid branch. Coherent upconversion of the electrostatic
  waves to electromagnetic waves produces an intrinsically stochastic
  emission component which is superposed on the gyrosynchrotron continuum
  generated by stably trapped electron fluxes. The role of the density and
  temperature of the ambient plasma in the wave growth and the transition
  of the three wave upconversion to stochastic, despite the stationarity
  of the energy source, are discussed in detail. The model appears to
  reproduce the observational features for reasonable parameters of the
  solar flare plasma.

Title: Electron cyclotron wave acceleration outside a flaring loop
Authors: Sprangle, P.; Vlahos, L.
Bibcode: 1983ApJ...273L..95S
Altcode:
  A model for the secondary acceleration of electrons outside a flaring
  loop is proposed. The results suggest that the narrow bandwidth
  radiation emitted by the unstable electron distribution inside a
  flaring loop can become the driver for secondary electron acceleration
  outside the loop. It is shown that a system of electrons gyrating
  about and streaming along an adiabatically spatially varying, static
  magnetic field can be efficiently accelerated to high energies by an
  electromagnetic wave propagating along and polarized transverse to
  the static magnetic field. The predictions from our model appear to
  be in general agreement with existing observations.

Title: Solar microwave bursts — A review
Authors: Kundu, M. R.; Vlahos, L.
Bibcode: 1982SSRv...32..405K
Altcode:
  We review the observational and theoretical results on the physics of
  microwave bursts that occur in the solar atmosphere. We particularly
  emphasize the advances made in burst physics over the last few
  years with the great improvement in spatial and time resolution
  especially with instruments like the NRAO three element interferometer,
  Westerbork Synthesis Radio Telescope and more recently the Very Large
  Array (VLA). We review the observations on pre-flare build-up of an
  active region at centimeter wavelengths. In particular we discuss
  the observations that in addition to the active region undergoing
  brightness and polarization changes on time scales of the order
  of an hour before a flare, there can be a change of the sense of
  polarization of a component of the relevant active region situated
  at the same location as the flare, implying the emergence of a flux
  of reverse polarity at coronal levels. The intensity distribution
  of cm-λ bursts is similar to that of soft X-ray and hard X-ray
  bursts. Indeed, it appears that the flaring behavior of the Sun at cm
  wavelengths is similar to that of some other cosmic transients such
  as flare stars and X-ray bursters. We discuss three distinct phases
  in the evolution of cm bursts, namely, impulsive phase, post-burst
  phase, and gradual rise and fall. The radiation mechanism for the
  impulsive phase of the microwave burst is gyrosynchrotron emission
  from mildly relativistic electrons that are accelerated near the
  energy release site and spiral in the strong magnetic field in the
  low corona. The details of the velocity distribution function of the
  energetic electrons and its time evolution are not known. We review
  the spectral characteristics for two kinds of velocity distribution,
  e.g., Maxwellian and Maxwellian with a power law tail for the energetic
  electrons. In the post-burst phase the energetic electrons are gradually
  thermalized. The thermal plasma released in the energy release region
  as well as the expanded parts of the overheated upper chromosphere
  may alter the emission mechanism. Thus, in the post-burst phase,
  depending on the average density and temperature of the thermal plasma,
  the emission mechanism may change from gyrosynchrotron to collisional
  bremsstrahlung from a thermal plasma. The gradual rise and fall (GFR)
  burst represents the heating of a flare plasma to temperatures of the
  order of 10<SUP>6</SUP> K, in association with a flare or an X-ray
  transient following a filament disruption. We discuss the flux density
  spectra of centimeter bursts. The great majority of the bursts have a
  single spectral maximum, commonly around 6 cm-λ The U-shaped signature
  sometimes found in cm-dcm burst spectrum of large bursts is believed
  to a be a reflection of only the fact that there are two different
  sources of burst radiation, one for cm-λ and the other for dcm-λ,
  with different electron energy distributions and different magnetic
  fields. Observations of fine structures with temporal resolutionof 10
  100 ms in the intensity profiles of cm-λ bursts are described. The
  existence of such fine time structures imply brightness temperatures
  in burst sources of order 10<SUP>15</SUP> K; their interpretation
  in terms of gyrosynchrotron measuring or the coherent interaction
  of upper hybrid waves excited by percipitating electron beams in
  a flaring loop is discussed. High spatial resolution observations
  (a few seconds of arc to ∼ 1″ arc) are discussed, with special
  reference to the one- and two-dimensional maps of cm burst sources. The
  dominance of one sense of circular polarization in some weak 6 cm
  bursts and its interpretation in terms of energetic electrons confined
  in an asymmetric magnetic loop is discussed. Two-dimensional snapshot
  maps obtained with the VLA show that multi-peak impulsive 6 cm burst
  phase radiation originates from several arcades of loops and that the
  burst source often occupies a substantial portion of the flaring loop,
  and is not confined strictly to the top of the loop. This phenomenon
  is interpreted in terms of the trapping of energetic electrons due
  to anomalous doppler resonance instability and the characteristic
  scale length of the magnetic field variation along the loop. The VLA
  observations also indicate that the onset of the impulsive phase of a
  6 cm burst can be associated with the appearance of a new system of
  loops. The presence of two loop systems with opposite polarities or
  a quadrupole field configuration is reminiscent of flare models in
  which a current sheet develops in the interface between two closed
  loops. We provide an extensive review of the emission and absorption
  processes in thermal and non-thermal velocity distributions. Unlike
  the thermal plasma where absorption and emission are inter-related
  through Kirchoff's law, the radiation emitted from a small population
  of non-thermal electrons can be reabsorbed from the same electrons
  (self-absorption) or from the background (thermal) electrons through
  gyro-resonance absorption, and free-free absorption. We also suggest
  that the non-thermal electrons can be unstable and these instabilities
  can be the source of very high brightness temperature, fine structure
  (∼ 10 ms) pulsations. Finally in the last part of this review we
  present several microwave burst models-the magnetic trap model, the
  two-component model, thermal model and the flaring loop model and give
  a critical discussion of the strength and weakness of these models.

Title: A Model for the Simultaneous Release of Hard X-ray and Type
    III Bursts
Authors: Vlahos, L.; Sprangle, P.
Bibcode: 1982BAAS...14..874V
Altcode:
  No abstract at ADS

Title: The importance of plasma effects on electron-cyclotron
    maser-emission from flaring loops
Authors: Sharma, R. R.; Vlahos, L.; Papadopoulos, K.
Bibcode: 1982A&A...112..377S
Altcode:
  Electron cyclotron maser instability has been suggested as the cause
  of the observed short (10-20 msec), intense (an approximate brightness
  temperature of 10 to the 15th K) and up to 100% polarized microwave
  solar emission. It is shown that plasma effects and thermal cyclotron
  damping, ignored in previous theories, play an important role in
  controlling the frequency range of the emission. The radio emission is
  suppressed for ratios of the plasma frequency to the cyclotron frequency
  smaller than 0.4. An examination of the cyclotron damping, reveals that
  the maser action is suppressed unless a large fraction (i.e., over 10%)
  of the accelerated electrons participates in the emission process.

Title: Electron acceleration and radiation signatures in loop
    coronal transients
Authors: Vlahos, L.; Gergely, T. E.; Papadopoulos, K.
Bibcode: 1982ApJ...258..812V
Altcode:
  It is proposed that in loop coronal transients an erupting loop moves
  away from the solar surface, with a velocity exceeding the local Alfven
  speed, pushing against the overlying magnetic fields and driving a shock
  in the front of the moving part of the loop. Lower hybrid waves are
  excited at the shock front and propagate radially toward the center of
  the loop with phase velocity along the magnetic field that exceeds the
  thermal velocity. The lower hybrid waves stochastically accelerate the
  tail of the electron distribution inside the loop. The manner in which
  the accelerated electrons are trapped in the moving loop are discussed,
  and their radiation signature is estimated. It is suggested that plasma
  radiation can explain the power observed in stationary and moving type
  IV bursts.

Title: Radio imaging of solar flares using the very large array -
    New insights into flare process
Authors: Kundu, M. R.; Schmahl, E. J.; Velusamy, T.; Vlahos, L.
Bibcode: 1982A&A...108..188K
Altcode:
  An interpretation of VLA observations of microwave bursts is presented
  in an attempt to distinguish between certain models of flares. The VLA
  observations provide information about the pre-flare magnetic field
  topology and the existence of mildly relativistic electrons accelerated
  during flares. Examples are shown of changes in magnetic field topology
  in the hour before flares. In one case, new bipolar loops appear to
  emerge, which is an essential component of the model developed by
  Heyvaerts et al. (1977). In another case, a quadrupole structure,
  suggestive of two juxtaposed bipolar loops, appears to trigger the
  flare. Because of the observed diversity of magnetic field topologies
  in microwave bursts, it is believed that the magnetic energy must
  be dissipated in more than one way. The VLA observations are clearly
  providing means for sorting out the diverse flare models.

Title: Limitation the upconversion of ion sound to langmuir
    turbulence.
Authors: Vlahos, L.; Papadopoulos, K.
Bibcode: 1982ApJ...252L..75V
Altcode:
  The weak turbulence theory of Tsytovich, Stenflo and Wilhelmsson
  (1981) for evaluation of the nonlinear transfer of ion acoustic waves
  to Langmuir waves is shown to be limited in its region of validity
  to the level of ion acoustic waves. It is also demonstrated that,
  in applying the upconversion of ion sound to Langmuir waves for
  electron acceleration, nonlinear scattering should be self-consistently
  included, with a suppression of the upconversion process resulting. The
  impossibility of accelerating electrons by such a process for any
  reasonable physical system is thereby reaffirmed.

Title: Radiation signatures from a locally energized flaring loop
Authors: Emslie, A. G.; Vlahos, L.
Bibcode: 1980ApJ...242..359E
Altcode:
  The radiation signatures from a locally energized solar flare loop
  based on the physical properties of the energy release mechanisms
  were consistent with hard X-ray, microwave, and EUV observations for
  plausible source parameters. It was found that a suprathermal tail
  of high energy electrons is produced by the primary energy release,
  and that the number of energetic charged particles ejected into the
  interplanetary medium in the model is consistent with observations. The
  radiation signature model predicts that the intrinsic polarization of
  the hard X-ray burst should increase over the photon energy range of
  20 to 100 keV.

Title: Microwave emission from flaring magnetic loops
Authors: Vlahos, L.
Bibcode: 1980IAUS...86..173V
Altcode:
  Characteristics of the microwave emission from a flaring loop are
  discussed under the assumptions that (a) the magnetic energy is released
  into a small volume compared to the volume of the loop, and the rate at
  which magnetic energy is transformed into plasma energy is faster than
  the energy losses from the same volume; and (b) the bulk of the energy
  released goes into the heating of the plasma and heats primarily the
  electrons. A mechanism by which mildly relativistic electrons escape
  from the flaring loop to the upper corona is proposed.

Title: On the upconversion of ion-sound to Langmuir turbulence
Authors: Vlahos, L.; Papadopoulos, K.
Bibcode: 1979ApJ...234L.217V
Altcode:
  Consideration is given to the upconversion of ion sound waves to
  excited Langmuir waves in solar flares. It is shown that, due to
  the process of anomalous high-frequency resistivity in which the
  reabsorption of Langmuir waves in the presence of ion waves is enhanced,
  the upconversion of ion sound waves to Langmuir waves is impossible
  in the absence of suprathermal particles and when the electron drift
  velocity is less than the electron thermal velocity.

Title: Collective plasma effects associated with the continuous
    injection model of solar flare particle streams.
Authors: Vlahos, L.; Papadopoulos, K.
Bibcode: 1979ApJ...233..717V
Altcode:
  A modified continuous injection model for impulsive solar flares
  that includes self-consistent plasma nonlinearities based on the
  concept of marginal stability is presented. A quasi-stationary state
  is established, composed of a hot truncated electron Maxwellian
  distribution confined by acoustic turbulence on the top of the loop
  and energetic electron beams precipitating in the chromosphere. It
  is shown that the radiation properties of the model are in accordance
  with observations.

Title: An interpretation of the polarization structure of microwave
    bursts.
Authors: Kundu, M. R.; Vlahos, L.
Bibcode: 1979ApJ...232..595K
Altcode:
  High-spatial-resolution (a few seconds of arc) observations of
  microwave bursts have demonstrated that only the impulsive phase of
  the burst is polarized; one observes only one polarity in the burst
  source if it is weak (Alissandrakis and Kundu) and both polarities if
  it is intense (Enome et al.). These results are interpreted in terms
  of an asymmetrical bipolar field structure of the loop in which the
  energetic electrons responsible for the radiation are contained. The
  role of unequal field strengths at the feet of the loop on the number of
  electrons trapped and their pitch angle distribution are discussed in
  a specific model. Computations of the polarized intensity originating
  from each foot of the loop seem to be consistent with the observations
  at present available.

Title: Plasma properties and radiation signatures of current driven
    active region loops on the Sun
Authors: Vlahos, L.
Bibcode: 1979PhDT.........2V
Altcode:
  The average plasma density in the coronal part of a loop is higher than
  in its surroundings but the ratio of the plasma kinetic pressure to
  magnetic pressure is less than one. These loop-like magnetic field lines
  may act as the energy transport lines from the internal layers of the
  Sun's photosphere to the chromosphere and the corona where the energy
  is stored and suddenly released or slowly dissipated. The photospheric
  disturbances which are associated with steady currents along the
  potential magnetic field lines were studied in order to identify the
  radiation signatures of the current density and its profile as well as
  the size of the loop in which the current flows. Three basic phenomena
  in which the current supposedly plays an important role are examined:
  the sudden release of energy in small loop-like structures (flares); the
  heating of loops of different sizes by anomalous current dissipation;
  and the sudden erosion of large scale loops (coronal transients). It
  is concluded that (1) the current driven from the fluid motions in the
  photosphere can, under certain conditions, trigger the tearing mode
  instability in a finite volume at the top of a small loop which may
  result in a sudden local heating and a transient electron acceleration;
  (2) the heating of a loop by 'anomalous' dissipation of currents is
  not feasible if the currents are driven from the photosphere and (3)
  it appears that under certain conditions the current flowing along a
  very large loop can force a loop upwards.

Title: Plasma Properties and Radiation Signatures of Current Driven
    Active Region Loops on the Sun.
Authors: Vlahos, Loukas
Bibcode: 1979PhDT........33V
Altcode:
  Our present understanding of the various phenomena taking place in the
  Sun's atmosphere has radically changed over the past few years. Recent
  observations, primarily from Skylab, have confirmed the existence
  of small scale structures which in turn have put severe constraints
  on the homogeneous plain parallel models of the Sun's atmosphere
  traditionally used to analyze the observations. It is now generally
  accepted that the small scale magnetic fields are responsible for these
  structures. Generally speaking, three types of regions can be identified
  on the Sun depending on the dominant magnetic field structure, i.e. the
  coronal holes, where the magnetic field lines are diffuse, irregular
  and weak; and the active regions, which are characterized by strong
  closed magnetic field structures. We usually identify as loops the
  magnetic field structures connecting opposite magnetic polarities
  in the photosphere. The average plasma density in the coronal part
  of the loop is higher than in its surroundings but the ratio of the
  plasma kinetic pressure to magnetic pressure is less than one. These
  loop-like magnetic field lines may act as the energy transport lines
  from the internal layers of the Sun's photosphere to the chromosphere
  and the corona where the energy is stored and suddenly released or
  slowly dissipated. We focus our studies at the photospheric disturbances
  which are associated with steady currents along the potential magnetic
  field lines. The current density and its profile as well as the size of
  the loop in which the current flows have important radiation signatures
  which we have tried to identify in our study. We examine three basic
  phenomena in which the current supposedly plays an important role: The
  sudden release of energy in small loop-like structures (flares), the
  heating of loops of different sizes by anomalous current dissipation and
  the sudden eruption of large scale loops (coronal transients). Our main
  conclusions are the following:. (a) The current driven from the fluid
  motions in the photosphere can, under certain conditions, trigger the
  tearing mode instability in a finite volume at the top of a small loop
  (length L &gt; 10('9) cm). This may result in a sudden local heating and
  a transient electron acceleration. We studied the dynamical evolution
  of this "explosion" and analyzed its hard x-ray, EUV microwave and
  meter wavelength signatures for the impulsive phase (e.g. t &lt; 1-10
  sec). We have also investigated the microwave and soft x-ray emission
  of a typical flaring loop in the post-burst phase. (b) The heating of
  a loop by "anomalous" dissipation of currents is not feasible if the
  currents are driven from the photosphere. We showed that low frequency
  current -driven instabilities cannot be excited in large steady loops
  (L &gt; 10('10) cm). Further, we showed that if the current-driven low
  frequency instabilities are excited, several radiation signatures should
  be associated with the loop that is heated. (c) It appears that under
  certain conditions the current flowing along a very large loop (L &gt;
  10('11) cm) can force a loop upwards. We examined the interaction of
  the erupting loops with the surrounding magnetic field. We found that
  the loop could act as a piston driving and forming a magnetic shock
  at the front edge of the loop, if the expansion velocity is larger
  than the local Alfven velocity. Electrons are accelerated in the
  wake of the shock (e.g. in the interior of the loop) and subsequently
  trapped. We studied the dynamic evolution of the accelerated electrons
  and their radio signatures. We found that many of the observed radio
  bursts associated with coronal transients can easily be explained by
  this model.

