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

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.

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

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.

Role of wave-particle resonance in turbulent transport in toroidal plasmas

The clear understanding of the wave-particle interaction and associated transport mechanism of different particle species in the drift wave instabilities is important for accurate modeling and predictions of the plasma confinement properties. Our global gyrokinetic simulations find that electron particle and heat transport decreases to a very low level, while ion heat transport level has no dramatic change when wave-particle resonance is suppressed in the collisionless trapped electron mode (CTEM) turbulence in the tokamak core. Similarly, ion heat transport in the self-consistent ion temperature gradient (ITG) turbulence simulation is qualitatively similar to that in the test-particle simulation using the static ITG turbulence fields. These simulation results show that electron transport is primarily driven by the wave-particle resonance in the CTEM turbulence, but the ion transport is mostly driven by the nonlinear wave-particle scattering in both the CTEM and ITG turbulence.

Particle-in-cell Simulation of 3He Enrichment in Solar Energetic Particle Events

3He enrichment is one distinctive feature of impulsive solar energetic particle events. This study is designed to investigate the process of plasma wave–particle resonance, which plays a key role in selectively accelerating heavy ions. We apply a 1.5 dimensional particle-in-cell simulation to model the electron-beam–plasma interaction that generates electron and ion cyclotron waves, namely proton and 4He cyclotron waves, whose dispersions are dependent on the magnetization parameter α = ω pe/Ωce and the temperature ratio τ = T e /T p . The background particles, e.g., 3He and 4He, resonate with the excited cyclotron waves and experience selective heating or acceleration. Specifically, the resonant modes of 3He ions lead to a more effective acceleration rate compared to those of the 4He ions. The simulation results provide a potential solution for understanding the abundance of heavy ions in the solar wind.

Mirror Mode Junctions as Sources of Radiation

Mirror modes in collisionless high-temperature plasmas represent macroscopic high-temperature quasi-superconductors with bouncing electrons in discrete-particle resonance with thermal ion-sound noise contributing to the ion-mode growth beyond quasilinear stability. In the semi-classical Ginzburg-Landau approximation the conditions for phase transition are reviewed. The quasi-superconducting state is of second kind causing a magnetically perforated plasma texture. Focussing on the interaction of mirror bubbles we apply semi-classical Josephson conditions and show that a mirror perforated plasma emits weak electromagnetic radiation which in the magnetosheath should be in the sub-millimeter, respectively, infrared range. This effect might be of astrophysical importance.

Analytical calculation of the orbital spectrum of the guiding centre motion in axisymmetric magnetic fields

Charged particle motion in axisymmetric toroidal magnetic fields is analysed within the context of the canonical Hamiltonian guiding centre theory. A canonical transformation to variables measuring the drift orbit deviation from a magnetic field line is introduced and an analytical transformation to action-angle variables is obtained, under a zero drift width approximation. The latter is used to provide compact formulas for the orbital spectrum of the drift motion, namely the bounce/transit frequencies as well as the bounce/transit averaged toroidal precession and gyration frequencies. These formulas are shown to have a remarkable agreement with numerically calculated full drift width frequencies and significant differences from standard analytical formulas based on a pendulum-like Hamiltonian description. The analytical knowledge of the orbital spectrum is crucial for the formulation of particle resonance conditions with symmetry-breaking perturbations and the study of the resulting particle, energy and momentum transport.