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Abstract Using measurements from the Van Allen Probes, we show that field‐aligned fluxes of electrons energized by dispersive Alfvén waves (DAWs) are prominent in the inner magnetosphere during active conditions. These electrons have preferentially field‐aligned anisotropies from 1.2 to>2 at energies ranging from tens of electron volts to several kiloelectron volts (keV), with largest values being coincident with magnetic field dipolarizations. Comparisons reveal that DAW energy densities and Poynting fluxes are strongly correlated with precipitating electron energies and energy fluxes and also O+ion outflow energies. These observations yield empirical inner magnetosphere relations between the DAW and electron inputs and the O+ion outflow response, providing important constraints for models. They also suggest that DAWs play an important role in enhancing field‐aligned electron input into the ionosphere that facilitates the outflow and subsequent energization of O+ions in the wave fields into the inner magnetosphere.
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MMS Observations of the Multiscale Wave Structures and Parallel Electron Heating in the Vicinity of the Southern Exterior Cusp
Abstract Understanding the physical mechanisms responsible for the cross‐scale energy transport and plasma heating from solar wind into the Earth's magnetosphere is of fundamental importance for magnetospheric physics and for understanding these processes in other places in the universe with comparable plasma parameter ranges. This paper presents observations from the Magnetosphere Multiscale (MMS) mission at the dawn‐side high‐latitude dayside boundary layer on February 25, 2016 between 18:55 and 20:05 UT. During this interval, MMS encountered both the inner and outer boundary layers with quasiperiodic low frequency fluctuations in all plasma and field parameters. The frequency analysis and growth rate calculations are consistent with the Kelvin‐Helmholtz instability (KHI). The intervals within the low frequency wave structures contained several counter‐streaming, low‐ (0–200 eV) and mid‐energy (200 eV–2 keV) electrons in the loss cone and trapped energetic (70–600 keV) electrons in alternate intervals. The counter‐streaming electron intervals were associated with large‐magnitude field‐aligned Poynting fluxes. Burst mode data at the large Alfvén velocity gradient revealed a strong correlation between counter streaming electrons, enhanced parallel electron temperatures, strong anti‐field aligned wave Poynting fluxes, and wave activity from sub‐proton cyclotron frequencies extending to electron cyclotron frequency. Waves were identified as Kinetic Alfvén waves but their contribution to parallel electron heating was not sufficient to explain the >100 eV electrons.
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- Award ID(s):
- 1707521
- PAR ID:
- 10375106
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 126
- Issue:
- 3
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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