Nondiffusive Pitch‐Angle Scattering of a Distribution of Energetic Particles by Coherent Whistler Waves
Abstract
Whether or not coherent magnetospheric whistler waves play important roles in the pitch‐angle scattering of energetic particles is a crucial question in magnetospheric physics. The interaction of a thermal distribution of energetic particles with coherent whistler waves is thus investigated. The distribution is prescribed by the Maxwell‐Jüttner distribution, which is a relativistic generalization of the Maxwell‐Boltzmann distribution. Coherent whistler waves are modeled by circularly polarized waves propagating parallel to the background magnetic field. It is shown that for parameters relevant to magnetospheric chorus, a significant fraction (1–5%) of the energetic particle population undergoes drastic, nondiffusive pitch‐angle scattering by coherent chorus. The scaling of this fraction with the wave amplitude may also explain the association of relativistic microbursts to large‐amplitude chorus. A much improved condition for large pitch‐angle scattering is presented that is related to, but may or may not include the exact resonance condition depending on the particle's initial conditions. The theory reveals a critical mechanism not contained in the widely used second‐order trapping theory.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 01, 2020
- Source ID
- 10.1029/2020ja027796
Entities
People
- Paul M. Bellan
- Young Dae Yoon
Organizations
- Air Force Office of Scientific Research
- California Institute of Technology
- National Science Foundation