scholarly journals Particle acceleration with anomalous pitch angle scattering in 3D separator reconnection

2020 ◽  
Vol 635 ◽  
pp. A63
Author(s):  
A. Borissov ◽  
T. Neukirch ◽  
E. P. Kontar ◽  
J. Threlfall ◽  
C. E. Parnell
Keyword(s):  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Test Particle ◽  
Pitch Angle ◽  
High Energy ◽  
Energy Spectra ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
Angle Scattering ◽  
Particle Orbits

Context. Understanding how the release of stored magnetic energy contributes to the generation of non-thermal high energy particles during solar flares is an important open problem in solar physics. There is a general consensus that magnetic reconnection plays a fundamental role in the energy release and conversion processes taking place during flares. A common approach for investigating how reconnection contributes to particle acceleration is to use test particle calculations in electromagnetic fields derived from numerical magnetohydrodynamic (MHD) simulations of reconnecting magnetic fields. These MHD simulations use anomalous resistivities that are orders of magnitude larger than the Spitzer resistivity that is based on Coulomb collisions. The processes leading to such an enhanced resistivity should also affect the test particles, for example, through pitch angle scattering. This study explores the effect of such a link between the level of resistivity and its impact on particle orbits and builds on a previous study using a 2D MHD simulation of magnetic reconnection. Aims. This paper aims to extend the previous investigation to a 3D magnetic reconnection configuration and to study the effect on test particle orbits. Methods. We carried out orbit calculations using a 3D MHD simulation of reconnection in a magnetic field with a magnetic separator. The orbit calculations use the relativistic guiding centre approximation but, crucially, they also include pitch angle scattering using stochastic differential equations. The effects of varying the resistivity and the models for pitch angle scattering on particle orbit trajectories, final positions, energy spectra, final pitch angle distribution, and orbit duration are all studied in detail. Results. Pitch angle scattering widens highly collimated beams of unscattered orbit trajectories, allowing orbits to access previously unaccessible field lines; this causes final positions to spread along other topological structures which could not be accessed without scattering. Scattered orbit energy spectra are found to be predominantly affected by the level of anomalous resistivity, with the pitch angle scattering model only playing a role in specific, isolated cases. This is in contrast to the study involving a 2D MHD simulation of magnetic reconnection, where pitch angle scattering had a more noticeable effect on the energy spectra. Pitch scattering effects are found to play a crucial role in determining the pitch angle and orbit duration distributions.

scholarly journals Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification

2014 ◽  
Vol 32 (5) ◽  
pp. 507-518 ◽  
Author(s):  
S. S. Chang ◽  
B. B. Ni ◽  
J. Bortnik ◽  
C. Zhou ◽  
Z. Y. Zhao ◽  
...  
Keyword(s):  
Test Particle ◽  
Pitch Angle ◽  
Low Frequency ◽  
Resonant Scattering ◽  
High Energy ◽  
Whistler Waves ◽  
Energetic Electrons ◽  
High Energy Electrons ◽  
Angle Scattering ◽  
Vlf Waves

Abstract. Modulated high-frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low-frequency (ELF)/very low-frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high-energy electrons in the plasmasphere. By ray tracing the magnetospheric propagation of ELF/VLF emissions artificially generated at low-invariant latitudes, we evaluate the relativistic electron resonant energies along the ray paths and show that propagating artificial ELF/VLF waves can resonate with electrons from ~ 100 keV to ~ 10 MeV. We further implement test particle simulations to investigate the effects of resonant scattering of energetic electrons due to triggered monotonic/single-frequency ELF/VLF waves. The results indicate that within the period of a resonance timescale, changes in electron pitch angle and kinetic energy are stochastic, and the overall effect is cumulative, that is, the changes averaged over all test electrons increase monotonically with time. The localized rates of wave-induced pitch-angle scattering and momentum diffusion in the plasmasphere are analyzed in detail for artificially generated ELF/VLF whistlers with an observable in situ amplitude of ~ 10 pT. While the local momentum diffusion of relativistic electrons is small, with a rate of < 10−7 s−1, the local pitch-angle scattering can be intense near the loss cone with a rate of ~ 10−4 s−1. Our investigation further supports the feasibility of artificial triggering of ELF/VLF whistler waves for removal of high-energy electrons at lower L shells within the plasmasphere. Moreover, our test particle simulation results show quantitatively good agreement with quasi-linear diffusion coefficients, confirming the applicability of both methods to evaluate the resonant diffusion effect of artificial generated ELF/VLF whistlers.

scholarly journals Particle Orbits, Trapping, and Acceleration in a Filamentary Current Sheet Model

1994 ◽  
Vol 142 ◽  
pp. 719-728
Author(s):  
Bernhard Kliem
Keyword(s):  
Particle Acceleration ◽  
Electric Field ◽  
Test Particle ◽  
Solar Flares ◽  
Acceleration Of Particles ◽  
Acceleration Process ◽  
Two Dimensional ◽  
Magnetic Island ◽  
Particle Orbits ◽  
Island Dynamics

AbstractTest particle orbits in the two-dimensional Fadeev equilibrium with a perpendicular electric field added are analyzed to show that impulsive bursty reconnection, which has been proposed as a model for fragmentary energy release in solar flares, may account also for particle acceleration to (near) relativistic energies within a fraction of a second. The convective electric field connected with magnetic island dynamics can play an important role in the acceleration process.Subject headings: acceleration of particles — MHD — plasmas — Sun: corona — Sun: flares

Large-scale particle acceleration during magnetic reconnection in solar flares

2020 ◽  
Author(s):  
Xiaocan Li ◽  
Fan Guo
Keyword(s):  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Power Law ◽  
Solar Flares ◽  
Large Scale ◽  
Magnetic Energy ◽  
High Energy ◽  
Macroscopic Model ◽  
Scale Particle ◽  
Reconnection Layer

&lt;p&gt;Magnetic reconnection is a primary driver of magnetic energy release and particle acceleration processes in space and astrophysical plasmas. Solar flares are a great example where observations have suggested that a large fraction of magnetic energy is converted into nonthermal particles and radiation. One of the major unsolved problems in reconnection studies is nonthermal particle acceleration. In the past decade or two, 2D kinetic simulations have been widely used and have identified several acceleration mechanisms in reconnection. Recent 3D simulations have shown that the reconnection layer naturally generates magnetic turbulence. Here we report our recent progresses in building a macroscopic model that includes these physics for explaining particle acceleration during solar flares. We show that, for sufficient large systems, high-energy particle acceleration processes can be well described as flow compression and shear. By means of 3D kinetic simulations, we found that the self-generated turbulence is essential for the formation of power-law electron energy spectrum in non-relativistic reconnection. Based on these results, we then proceed to solve an energetic particle transport equation in a compressible reconnection layer provided by high-Lundquist-number MHD simulations. Due to the compression effect, particles are accelerated to high energies and develop power-law energy distributions. The power-law index and maximum energy are both comparable to solar flare observations. This study clarifies the nature of particle acceleration in large-scale reconnection sites and initializes a framework for studying large-scale particle acceleration during solar flares.&lt;/p&gt;

scholarly journals Particle acceleration and the origin of the very high energy emission around black holes and relativistic jets

2020 ◽  
Vol 14 (S342) ◽  
pp. 13-18
Author(s):  
Elisabete M. de Gouveia Dal Pino ◽  
Grzegorz Kowal ◽  
Luis Kadowaki ◽  
Tania E. Medina-Torrejón ◽  
Yosuke Mizuno ◽  
...  
Keyword(s):  
Black Hole ◽  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
High Energy ◽  
Black Hole Binaries ◽  
Mhd Instabilities ◽  
Test Particles ◽  
Very High Energy ◽  
General Relativistic ◽  
Very High

AbstractParticle acceleration induced by fast magnetic reconnection may help to solve current puzzles related to the interpretation of the very high energy (VHE) and neutrino emissions from AGNs and compact sources in general. Our general relativistic-MHD simulations of accretion disk-corona systems reveal the growth of turbulence driven by MHD instabilities that lead to the development of fast magnetic reconnection in the corona. In addition, our simulations of relativistic MHD jets reveal the formation of several sites of fast reconnection induced by current-driven kink turbulence. The injection of thousands of test particles in these regions causes acceleration up to energies of several PeVs, thus demonstrating the ability of this process to accelerate particles and produce VHE and neutrino emission, specially in blazars. Finally, we discuss how reconnection can also explain the observed VHE luminosity-black hole mass correlation, involving hundreds of non-blazar sources like Perseus A, and black hole binaries.

MMS observations of explosive filamentary current within two adjacent ion scale flux ropes

2021 ◽  
Author(s):  
Yuchen Xiao ◽  
Shutao Yao ◽  
Ruilong Guo ◽  
Quanqi Shi ◽  
Anmin Tian ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Energy Dissipation ◽  
Magnetic Reconnection ◽  
Temporal Resolution ◽  
Pitch Angle ◽  
Angle Distribution ◽  
Pitch Angle Distribution ◽  
The Past ◽  
Flux Ropes ◽  
Spatio Temporal

&lt;p&gt;Flux ropes have attracted extensive attention due to their importance in studying instantaneous magnetic reconnection&amp;#160;over the past years. Recently, with the improvement of high spatio-temporal resolution measurements, kinetic-scale flux ropes have been detected. However, their generation&amp;#160;and energy energization are still unclear. In this study, electron-scale filamentary&amp;#160;currents&amp;#160;within&amp;#160;two adjacent ion scale flux ropes&amp;#160;are observed&amp;#160;using MMS data. We find that:&lt;/p&gt;&lt;p&gt;1. Intense and explosive filamentary currents in parallel and perpendicular directions are found inside the flux ropes.&lt;/p&gt;&lt;p&gt;2. The electron pitch angle distribution appears &quot;X&quot; like shape, and could be caused by the electron acceleration.&lt;/p&gt;&lt;p&gt;3. The filamentary current appears in the center of the &quot;X&quot; distribution.&lt;/p&gt;&lt;p&gt;The filamentary currents are important and are considered to be the evidence of secondary reconnection&amp;#160;[Wang et al.,&amp;#160;2020]. The&amp;#160;observations in our study are&amp;#160;important&amp;#160;to reveal the particle acceleration&amp;#160;and energy dissipation in&amp;#160;magnetic reconnection.&lt;/p&gt;

scholarly journals Flare particle acceleration in the interaction of twisted coronal flux ropes

2018 ◽  
Vol 611 ◽  
pp. A40 ◽  
Author(s):  
J. Threlfall ◽  
A. W. Hood ◽  
P. K. Browning
Keyword(s):  
Particle Acceleration ◽  
Solar Flares ◽  
Three Dimensional ◽  
Coronal Loops ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
Uniform Background ◽  
Energy Gains ◽  
Particle Behaviour

Aim. The aim of this work is to investigate and characterise non-thermal particle behaviour in a three-dimensional (3D) magnetohydrodynamical (MHD) model of unstable multi-threaded flaring coronal loops.Methods. We have used a numerical scheme which solves the relativistic guiding centre approximation to study the motion of electrons and protons. The scheme uses snapshots from high resolution numerical MHD simulations of coronal loops containing two threads, where a single thread becomes unstable and (in one case) destabilises and merges with an additional thread.Results. The particle responses to the reconnection and fragmentation in MHD simulations of two loop threads are examined in detail. We illustrate the role played by uniform background resistivity and distinguish this from the role of anomalous resistivity using orbits in an MHD simulation where only one thread becomes unstable without destabilising further loop threads. We examine the (scalable) orbit energy gains and final positions recovered at different stages of a second MHD simulation wherein a secondary loop thread is destabilised by (and merges with) the first thread. We compare these results with other theoretical particle acceleration models in the context of observed energetic particle populations during solar flares.

Particle losses due to RF-enhanced pitch-angle scattering into velocity space loss regions

1984 ◽  
Vol 32 (2) ◽  
pp. 273-281 ◽  
Author(s):  
D. Anderson ◽  
M. Lisak
Keyword(s):  
Magnetic Field ◽  
Distribution Function ◽  
Pitch Angle ◽  
High Energy ◽  
Velocity Space ◽  
Rf Heating ◽  
Fusion Plasma ◽  
Angle Scattering ◽  
Heated Particle ◽  
Scattering Losses

The application of RF heating (ICRH or LHH) to a fusion plasma creates high-energy tails on the distribution function of the heated particle species. In the presence of loss regions in velocity space, e. g. due to particle drifts in the toroidal magnetic field ripple of a tokamak, the collisional pitch-angle scattering losses may be significantly enhanced. The present work assesses the importance of such RF-enhanced losses and explicit expressions are derived for the evolution of the loss fraction. In particular, for parameters typical of PLT we find that the loss fraction could rapidly reach high values.

Particle Acceleration at a Perpendicular Shock in the Limit of Weak Pitch-Angle Scattering

2008 ◽  
Author(s):  
J. Giacalone ◽  
Gang Li ◽  
Qiang Hu ◽  
Olga Verkhoglyadova ◽  
Gary P. Zank ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Pitch Angle ◽  
Angle Scattering

Electron pitch-angle diffusion driven by oblique whistler-mode turbulence

1971 ◽  
Vol 6 (3) ◽  
pp. 589-606 ◽  
Author(s):  
L. R. Lyons ◽  
R. M. Thorne ◽  
C. F. Kennel
Keyword(s):  
Wave Energy ◽  
Diffusion Coefficients ◽  
Pitch Angle ◽  
High Energy ◽  
Harmonic Number ◽  
General Description ◽  
Linear Diffusion ◽  
Whistler Mode ◽  
Angle Scattering ◽  
Cyclotron Harmonic

A general description of cyclotron harmonic resonant pitch-angle scattering is presented. Quasi-linear diffusion coefficients are prescribed in terms of the wave normal distribution of plasma wave energy. Numerical computations are performed for the specific case of relativistic electrons interacting with a band of low frequency whistler-mode turbulence. A parametric treatment of the wave energy distribution permits normalized diffusion coefficients to be presented graphically solely as a function of the electron pitch-angle.The diffusion coefficients generally decrease with increasing cyclotron harmonic number. Higher harmonic diffusion is insignificant at very small electron pitch-angles, but becomes increasingly important as the pitch-angle increases. One thus expected the rate of pitch-angle scattering to decrease with increasing electron energy, since the resonant value of the latter varies proportionately with harmonic number. This indicates that, in mirror-type magnet field geometrics, such as the Earth's radiation belts, the diffusion losses of high energy electrons are likely to be appreciably slower than those at low energy. Integration of the diffusion rates along a complete bounce orbit will be required to clarify this point, however, since the high-energy particles will be subject to more rapid first harmonic diffusion near their mirror points.

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