We study the parametric decay instability of parallel-propagating Alfvén waves in a low-beta plasma using one-dimensional fully kinetic simulations. We focus for the first time on the conversion of the energy stored in the initial Alfvén wave into particle internal energy, and on its partition between particle species. We show that compressible fluctuations generated by the decay of the pump wave into a secondary ion-acoustic mode and a reflected Alfvén wave contribute to the gain of internal energy via two distinct mechanisms. First, the ion-acoustic mode leads nonlinearly to proton trapping and proton phase-space mixing, in agreement with previous work based on hybrid simulations. Second, during the nonlinear stage, a compressible front of the fast type develops at the steepened edge of the backward Alfvén wave leading to a field-aligned proton beam propagating backwards at the Alfvén speed. We find that parametric decay heats preferentially protons, which gain approximately 50 % of the pump wave energy in the form of internal energy. However, we find that electrons are also energized and that they contribute to the total energy balance by gaining 10 % of the pump wave energy. By investigating energy partition and particle heating during parametric decay, our results contribute to the determination of the role of compressible and kinetic effects in wave-driven models of the solar wind.
The properties of traveling kinetic Alfvén waves (KAWs) and their role in energizing electrons in the inner magnetosphere during a geomagnetic storm are examined using measurements from the Van Allen Probes and Gyrofluid‐Kinetic Electron (GKE) model simulations. Traveling KAWs occur in the vicinity of energetic plasma injection fronts in association with magnetic field dipolarizations. The KAWs coincide with energized field‐aligned electrons at energies ≲1 keV. By using observational constraints and incorporating hot and cold electron populations, the GKE simulations are able to reproduce the observed energized electron distribution signatures. The modeling results demonstrate the crucial importance of cold electrons for best observational agreement. The results show that the electron response to KAWs can be substantially different for opposing current regions and are a sensitive function of the cold electron relative density.
more » « less- NSF-PAR ID:
- 10372453
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 49
- Issue:
- 15
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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