scholarly journals Interaction between long-period ULF waves and charged particle in the magnetosphere: theory and observations (overview)

2021 ◽  
Vol 7 (4) ◽  
pp. 33-66
Author(s):  
Dmitri Klimushkin ◽  
Pavel Mager ◽  
Maksim Chelpanov ◽  
Danila Kostarev
Keyword(s):  
Low Frequency ◽  
High Energy ◽  
Larmor Radius ◽  
Small Scale ◽  
Ulf Waves ◽  
Finite Larmor Radius ◽  
Long Period ◽  
Particle Resonance ◽  
Modulation Methods ◽  
High Energy Particles

The paper reviews the current state of the problem of interaction between long-period ultra-low-frequency (ULF) waves and high-energy particles. We consider elements of the theory of energy exchange between waves and particles, particle transport across magnetic shells under the influence of the electromagnetic field of a wave, the acceleration of radiation belt particles by both resonant and non-resonant mechanisms. We examine the mechanisms of generation of azimuthally-small-scale ULF waves due to instabilities arising from the wave–particle resonance. The cases of Alfvén, drift-compressional, and drift-mirror waves are analyzed. It is noted that due to the lack of a detailed theory of drift-mirror modes, the possibility of their existence in the magnetosphere cannot be taken as a proven fact. We summarize experimental data on the poloidal and compression ULF waves generated by unstable populations of high-energy particles. We investigate the mechanisms of modulation of energetic particle fluxes by ULF waves and possible observational manifestations of such modulation. Methods of studying the structure of waves across magnetic shells by recording fluxes of resonant particles with a finite Larmor radius are discussed.

scholarly journals Interaction between long-period ULF waves and charged particle in the magnetosphere: theory and observations (overview)

2021 ◽  
Vol 7 (4) ◽  
pp. 35-69
Author(s):  
Dmitri Klimushkin ◽  
Pavel Mager ◽  
Maksim Chelpanov ◽  
Danila Kostarev
Keyword(s):  
Low Frequency ◽  
High Energy ◽  
Larmor Radius ◽  
Small Scale ◽  
Ulf Waves ◽  
Finite Larmor Radius ◽  
Long Period ◽  
Particle Resonance ◽  
Modulation Methods ◽  
High Energy Particles

The paper reviews the current state of the problem of interaction between long-period ultra-low-frequency (ULF) waves and high-energy particles. We consider elements of the theory of energy exchange between waves and particles, particle transport across magnetic shells under the influence of the electromagnetic field of a wave, the acceleration of radiation belt particles by both resonant and non-resonant mechanisms. We examine the mechanisms of generation of azimuthally-small-scale ULF waves due to instabilities arising from the wave–particle resonance. The cases of Alfvén, drift-compressional, and drift-mirror waves are analyzed. It is noted that due to the lack of a detailed theory of drift-mirror modes, the possibility of their existence in the magnetosphere cannot be taken as a proven fact. We summarize experimental data on the poloidal and compression ULF waves generated by unstable populations of high-energy particles. We investigate the mechanisms of modulation of energetic particle fluxes by ULF waves and possible observational manifestations of such modulation. Methods of studying the structure of waves across magnetic shells by recording fluxes of resonant particles with a finite Larmor radius are discussed.

scholarly journals Reduced models accounting for parallel magnetic perturbations: gyrofluid and finite Larmor radius–Landau fluid approaches

2016 ◽  
Vol 82 (6) ◽  
Author(s):  
E. Tassi ◽  
P. L. Sulem ◽  
T. Passot
Keyword(s):  
Fluid Model ◽  
Collisionless Plasma ◽  
Low Frequency ◽  
Wave Model ◽  
Plasma Phys ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Closure Relation ◽  
Reduced Models ◽  
Finite Larmor Radius

Reduced models are derived for a strongly magnetized collisionless plasma at scales which are large relative to the electron thermal gyroradius and in two asymptotic regimes. One corresponds to cold ions and the other to far sub-ion scales. By including the electron pressure dynamics, these models improve the Hall reduced magnetohydrodynamics (MHD) and the kinetic Alfvén wave model of Boldyrev et al. (2013 Astrophys. J., vol. 777, 2013, p. 41), respectively. We show that the two models can be obtained either within the gyrofluid formalism of Brizard (Phys. Fluids, vol. 4, 1992, pp. 1213–1228) or as suitable weakly nonlinear limits of the finite Larmor radius (FLR)–Landau fluid model of Sulem and Passot (J. Plasma Phys., vol 81, 2015, 325810103) which extends anisotropic Hall MHD by retaining low-frequency kinetic effects. It is noticeable that, at the far sub-ion scales, the simplifications originating from the gyroaveraging operators in the gyrofluid formalism and leading to subdominant ion velocity and temperature fluctuations, correspond, at the level of the FLR–Landau fluid, to cancellation between hydrodynamic contributions and ion finite Larmor radius corrections. Energy conservation properties of the models are discussed and an explicit example of a closure relation leading to a model with a Hamiltonian structure is provided.

scholarly journals Diffusion and radiation in magnetized collisionless plasmas with small-scale Whistler turbulence

2016 ◽  
Vol 82 (2) ◽  
Author(s):  
Brett D. Keenan ◽  
Mikhail V. Medvedev
Keyword(s):  
Numerical Study ◽  
High Energy ◽  
High Energy Density ◽  
Larmor Radius ◽  
Small Scale ◽  
Collisionless Plasmas ◽  
Correlation Scale ◽  
Scale Turbulence ◽  
Solar Plasmas ◽  
High Energy Density Plasmas

Magnetized high-energy-density plasmas can often have strong electromagnetic fluctuations whose correlation scale is smaller than the electron Larmor radius. Radiation from the electrons in such plasmas – which markedly differs from both synchrotron and cyclotron radiation – is tightly related to their energy and pitch-angle diffusion. In this paper, we present a comprehensive theoretical and numerical study of particle transport in cold, ‘small-scale’ Whistler-mode turbulence and its relation to the spectra of radiation simultaneously produced by these particles. We emphasize that this relation is a superb diagnostic tool of laboratory, astrophysical, interplanetary and solar plasmas with a mean magnetic field and strong small-scale turbulence.

scholarly journals Landau fluid closures with nonlinear large-scale finite Larmor radius corrections for collisionless plasmas

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
P. L. Sulem ◽  
T. Passot
Keyword(s):  
Large Scale ◽  
Fluid Model ◽  
Low Frequency ◽  
Larmor Radius ◽  
Large Temperature ◽  
Ion Cyclotron Resonance ◽  
Finite Larmor Radius ◽  
Collisionless Plasmas ◽  
Kinetic Effects ◽  
Linear Kinetic Theory

With the aim to develop a tool for simulating turbulence in collisionless magnetized plasmas, fluid models retaining low-frequency kinetic effects such as Landau damping and finite Larmor radius (FLR) corrections are discussed. It turns out that, in the absence of ion-cyclotron resonance, the dispersion and damping of kinetic Alfvén waves at scales as small as a fraction of the ion Larmor radius are accurately reproduced when using fluid estimates of the non-gyrotropic moments, at leading-order within a large-scale asymptotics. Differently, evaluations based on the low-frequency linear kinetic theory are necessary in regimes of large temperature anisotropies, and in particular in the presence of the mirror instability. Combining both descriptions leads to a new Landau fluid model retaining large-scale FLR nonlinearities, while reproducing the linear dynamics of low-frequency modes at the sub-ionic scales.

Propagation of Alfvén waves in ion-sound turbulent plasma

1971 ◽  
Vol 6 (2) ◽  
pp. 309-323 ◽  
Author(s):  
André Rogister
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Alfven Waves ◽  
Turbulent Plasma ◽  
Larmor Radius ◽  
Alfvén Waves ◽  
Sound Waves ◽  
Very High Frequency ◽  
Frequency Wave ◽  
Finite Larmor Radius

The propagation of low-frequency, large-scale (compared to the ion Larmor frequency Ωi and radius Ri), oblique Alfvén waves in a turbulent plasma is investigated in the framework of kinetic theory. The turbulent field is the statistical average of one-dimensional ion-sound waves of very high frequency and short wavelength (ω ≫ ΩiRe≫ λ). In the absence of resonant particle effects, and to first order in a finite Larmor radius expansion, it is shown that the turbulence can lead either to spatial diffusion (damping) or anti-diffusion (growth), with Bohm scaling, of the low frequency wave. Finite Larmor radius and frequency effects in the propagation of oblique Alfvén waves are simultaneously obtained for arbitrary β plasma; the results can easily be generalized, merely by deforming certain integration contours, to obtain the corresponding Landau decrement.

scholarly journals Excitation of low frequency oscillations in a planetary magnetosheath by supersonic shear flow

2011 ◽  
Vol 18 (2) ◽  
pp. 209-221 ◽  
Author(s):  
N. Borisov ◽  
M. Fränz
Keyword(s):  
Growth Rate ◽  
Low Frequency ◽  
Negative Energy ◽  
Larmor Radius ◽  
Coordinate Frame ◽  
Finite Larmor Radius ◽  
Oxygen Ions ◽  
Low Frequency Oscillations ◽  
Electrons And Ions ◽  
Component Plasma

Abstract. We show that the slow magnetosonic (SM) perturbations generated in the vicinity of the magnetopause, due to the excitation of the Kelvin-Helmholtz (K.-H.) instability in the case of a supersonic flow velocity, are transformed into fast magnetosonic (FM) waves which can propagate into the magnetosheath. Under the conditions discussed in this paper, the FM wave has negative energy in the stationary (magnetospheric) coordinate frame. Due to this the outgoing FM wave increases the growth rate of the K.-H. instability excited at the magnetopause. Within the linear theory, we investigate the influence of the excited FM wave on the growth rate of the K.-H. instability. Simultaneously we predict the transformation of the SM mode into kinetic Alfvén (KA) mode. Thus, in general, two types of waves with different polarizations (the KA wave and the FM wave) should appear in the magnetosheath due to the excitation of the K.-H. instability. At the same time, the SM perturbations are only present in the localized region where the K.-H. instability is excited. To correctly describe the excitation of waves, we use two-fluid (for electrons and ions) magnetohydrodynamics. This approach is more general than the ideal magnetohydrodynamics and allows us to take into account the effects associated with the finite Larmor radius of ions. Also it can be used to investigate the K.-H. instability in a multi-component plasma, or in the case where the frequency of perturbations is of the order of the gyrofrequency of oxygen ions which may occur, for example, at the magnetosheath of Mars.

Magnetohydrodynamic equations for plasmas with finite-Larmor-radius effects

1998 ◽  
Vol 60 (1) ◽  
pp. 133-149 ◽  
Author(s):  
IGOR O. POGUTSE ◽  
ANDREI I. SMOLYAKOV ◽  
AKIRA HIROSE
Keyword(s):  
Magnetic Field ◽  
Evolution Equations ◽  
Good Accuracy ◽  
Low Frequency ◽  
Momentum Balance ◽  
Larmor Radius ◽  
System Of Nonlinear Equations ◽  
Magnetohydrodynamic Equations ◽  
Finite Larmor Radius ◽  
Plasma Response

It is shown that the truncation of the infinite hierarchy of fluid equations obtained as moments of the Vlasov kinetic equation leads to a system of nonlinear equations that describe finite-Larmor-radius effects with good accuracy. Inertial terms in the momentum balance, viscosity and heat-flux evolution equations are crucial for a uniform description of the plasma response with an arbitrary Larmor radius. In the low-frequency ordering, the obtained equations are simplified by an expansion in the parameter 1/B, where B is the equilibrium magnetic field. The results of the second-order [Oscr ](1/B2) and the fourth-order [Oscr ](1/B4) closures are compared. It is shown that the accuracy of the description improves for higher-order closures.

Gyrokinetic Simulation of Magnetic Compressional Modes in General Geometry

2011 ◽  
Vol 10 (4) ◽  
pp. 899-911 ◽  
Author(s):  
Peter Porazik ◽  
Zhihong Lin
Keyword(s):  
Balance Equation ◽  
Equations Of Motion ◽  
Low Frequency ◽  
Force Balance ◽  
Larmor Radius ◽  
Finite Larmor Radius ◽  
Phase Space Integration ◽  
General Geometry ◽  
Compressional Component ◽  
Force Balance Equation

AbstractA method for gyrokinetic simulation of low frequency (lower than the cyclotron frequency) magnetic compressional modes in general geometry is presented. The gyrokinetic-Maxwell system of equations is expressed fully in terms of the compressional component of the magnetic perturbation, δB∥, with finite Larmor radius effects. This introduces a “gyro-surface” averaging of δB∥ in the gyrocenter equations of motion, and similarly in the perpendicular Ampere’s law, which takes the form of the perpendicular force balance equation. The resulting system can be numerically implemented by representing the gyro-surface averaging by a discrete sum in the configuration space. For the typical wavelength of interest (on the order of the gyroradius), the gyro-surface averaging can be reduced to averaging along an effective gyro-orbit. The phase space integration in the force balance equation can be approximated by summing over carefully chosen samples in the magnetic moment coordinate, allowing for an efficient numerical implementation.

scholarly journals Escape of high-energy oxygen ions through magnetopause reconnection under northward IMF

2008 ◽  
Vol 26 (12) ◽  
pp. 3955-3966 ◽  
Author(s):  
S. Kasahara ◽  
H. Hasegawa ◽  
K. Keika ◽  
Y. Miyashita ◽  
M. N. Nishino ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Recovery Phase ◽  
High Energy ◽  
Larmor Radius ◽  
Closed Field ◽  
Escape Route ◽  
Finite Larmor Radius ◽  
Oxygen Ions ◽  
Field Lines

Abstract. During a storm recovery phase on 15 May 2005, the Geotail spacecraft repeatedly observed high-energy (>180 keV) oxygen ions in the dayside magnetosheath near the equatorial plane. We focused on the time period from 11:20 UT to 13:00 UT, when Geotail observed the oxygen ions and the interplanetary magnetic field (IMF) was constantly northward. The magnetic reconnection occurrence northward and duskward of Geotail is indicated by the Walén analysis and convective flows in the magnetopause boundary layer. Anisotropic pitch angle distributions of ions suggest that high-energy oxygen ions escaped from the northward of Geotail along the reconnected magnetic field lines. From the low-energy particle precipitation in the polar cap observed by DMSP, which is consistent with magnetic reconnection occurring between the magnetosheath field lines and the magnetospheric closed field lines, we conclude that these oxygen ions are of ring current origin. Our results thus suggest a new escape route of oxygen ions during northward IMF. In the present event, this escape mechanism is more dominant than the leakage via the finite Larmor radius effect across the dayside equatorial magnetopause.

scholarly journals Prospects for radio detection of stellar plasma beams

2020 ◽  
Vol 639 ◽  
pp. L7 ◽  
Author(s):  
H. K. Vedantham
Keyword(s):  
Atmospheric Chemistry ◽  
Low Frequency ◽  
High Energy ◽  
Radio Bursts ◽  
Particle Beams ◽  
Solar Particle Events ◽  
Stellar Flares ◽  
Radio Detection ◽  
Solar Eruptions ◽  
High Energy Particles

Violent solar eruptions are often accompanied by relativistic beams of charged particles. In the solar context they are referred to as solar particle events and are known to generate a characteristic swept-frequency radio burst. Due to their ionising potential, these beams influence atmospheric chemistry and habitability. Radio observations provide a crucial discriminant between stellar flares that do and do not generate particle beams. Here I use solar empirical data and semi-quantitative theoretical estimates to gauge the feasibility of detecting the associated radio bursts. My principal conclusion is that a dedicated search for swept frequency radio bursts on second timescales in existing low-frequency (ν ≲ 102 MHz) datasets, while technically challenging, will likely provide the evidence high-energy particles beams in Sun-like stars.

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