PREPRINT
C777C689-C6E4-48D5-A417-8D27B93549B7

Whistler Waves As a Signature of Converging Magnetic Holes in Space Plasmas

Wence Jiang, Daniel Verscharen, Hui Li, Chi Wang, Kristopher G. Klein
arXiv:2207.00273

Submitted on 1 July 2022

Abstract

Magnetic holes are plasma structures that trap a large number of particles in a magnetic field that is weaker than the field in its surroundings. The unprecedented high time-resolution observations by NASA's Magnetospheric Multi-Scale (MMS) mission enable us to study the particle dynamics in magnetic holes in the Earth's magnetosheath in great detail. We reveal the local generation mechanism of whistler waves by a combination of Landau-resonant and cyclotron-resonant wave-particle interactions of electrons in response to the large-scale evolution of a magnetic hole. As the magnetic hole converges, a pair of counter-streaming electron beams form near the hole's center as a consequence of the combined action of betatron and Fermi effects. The beams trigger the generation of slightly-oblique whistler waves. Our conceptual prediction is supported by a remarkable agreement between our observations and numerical predictions from the Arbitrary Linear Plasma Solver (ALPS). Our study shows that wave-particle interactions are fundamental to the evolution of magnetic holes in space and astrophysical plasmas.

Preprint

Comment: This manuscript was accepted by ApJ (AAS39526R1)

Subjects: Physics - Plasma Physics; Astrophysics - Earth and Planetary Astrophysics; Physics - Space Physics

URL: https://arxiv.org/abs/2207.00273