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- Title
A Case Study of Nonresonant Mode 3‐s ULF Waves Observed by MMS.
- Authors
Wang, Shan; Chen, Li‐Jen; Ng, Jonathan; Bessho, Naoki; Le, Guan; Fung, Shing F.; Gershman, Daniel J.; Giles, Barbara L.
- Abstract
The nature of the 3‐s ultralow frequency (ULF) wave in the Earth's foreshock region and the associated wave‐particle interaction are not yet well understood. We investigate the 3‐s ULF waves using Magnetospheric Multiscale (MMS) observations. By combining the plasma rest frame wave properties obtained from multiple methods with the instability analysis based on the velocity distribution in the linear wave stage, the ULF wave is determined to be due to the ion/ion nonresonant mode instability. The interaction between the wave and ions is analyzed using the phase relationship between the transverse wave fields and ion velocities and using the longitudinal momentum equation. During the stage when ULF waves have sinusoidal waveforms up to |dB|/|B0| ~ 3, where dB is the wave magnetic field and B0 is the background magnetic field, the wave electric fields perpendicular to B0 do negative work to solar wind ions; along B0, a longitudinal electric field develops, but the V × B force is stronger and leads to solar wind ion deceleration. During the same wave stage, the backstreaming beam ions gain energy from the transverse wave fields and get deceleration along B0 by the longitudinal electric field. The ULF wave leads to electron heating, preferentially in the direction perpendicular to the local magnetic field. Secondary waves are generated within the ULF waveforms, including whistler waves near half of the electron cyclotron frequency, high‐frequency electrostatic waves, and magnetosonic whistler waves. The work improves the understanding of the nature of 3‐s ULF waves and the associated wave‐particle interaction. Key Points: A 3‐s ULF wave event observed by MMS in a foreshock region is determined to be due to the nonresonant ion beam instabilitySolar wind ions lose energies to the transverse wave field and are decelerated along the background magnetic field by the Lorentz forceThe ULF wave leads to electron heating and excites secondary waves
- Subjects
MAGNETOSPHERE; IONOSPHERE; BIOENERGETICS; ELECTRIC fields; MAGNETISM
- Publication
Journal of Geophysical Research. Space Physics, 2020, Vol 125, Issue 11, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2020JA028557