Resonance of Low-frequency Electromagnetic and Ion-sound Modes in the Solar Wind

Document Type

Article

Publication Date

6-1-2024

Abstract

Parker Solar Probe measurements have recently shown that coherent fast magnetosonic and Alfvén ion-cyclotron waves are abundant in the solar wind and can be accompanied by higher-frequency electrostatic fluctuations. In this Letter we reveal the nonlinear process capable of channelling the energy of low-frequency electromagnetic to higher-frequency electrostatic fluctuations observed on board Parker Solar Probe. We present Hall-MHD simulations demonstrating that low-frequency electromagnetic fluctuations can resonate with the ion-sound mode, which results in steepening of plasma density fluctuations, electrostatic spikes, and harmonics in the electric field spectrum. The resonance can occur around the wavenumber determined by the ratio between local sound and Alfvén speeds, but only in the case of oblique propagation to the background magnetic field. The resonance wavenumber, its width, and steepening timescale are estimated, and all indicate that the revealed two-wave resonance can frequently occur in the solar wind. This process can be a potential channel of energy transfer from cyclotron resonant ions producing the electromagnetic fluctuations to Landau resonant ions and electrons absorbing the energy of the higher-frequency electrostatic fluctuations.

Identifier

85194461857 (Scopus)

Publication Title

Astrophysical Journal Letters

External Full Text Location

https://doi.org/10.3847/2041-8213/ad4ba8

e-ISSN

20418213

ISSN

20418205

Issue

2

Volume

967

Grant

80NSSC22K1014

Fund Ref

National Aeronautics and Space Administration

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