Electron resonant scattering by whistler‐mode waves is one of the most important mechanisms responsible for electron precipitation to the Earth's atmosphere. The temporal and spatial scales of such precipitation are dictated by properties of their wave source and background plasma characteristics, which control the efficiency of electron resonant scattering. We investigate these scales with measurements from the two low‐altitude Electron Losses and Fields Investigation (ELFIN) CubeSats that move practically along the same orbit, with along‐track separations ranging from seconds to tens of minutes. Conjunctions with the equatorial THEMIS mission are also used to aid our interpretation. We compare the variations in energetic electron precipitation at the same
Cherenkov radiation from a pulse of charge propagating along the magnetic field in a magnetized plasma is analyzed using theory and fluid‐kinetic simulations. Besides radiation into whistler modes, the subject of many previous investigations in laboratory and space, radiation can occur through extraordinary (X) modes. Theory and simulations demonstrate that X mode radiation efficiencies can be orders of magnitude higher than those into whistler modes. Test particle simulations of the dynamics of energetic electrons in the beam‐generated wavefield show that X modes can also induce pitch angle scattering much more efficiently than whistlers. While coherence effects associated with spreading of realistic beam pulses may limit the size of the X mode source region, a simple model of beam dynamics suggests that the size of this region could be substantial (hundreds of meters for ionospheric conditions). These results have potentially important implications for many problems, including understanding losses in the near‐Earth environment and radiation belt remediation.
more » « less- Award ID(s):
- 1707275
- NSF-PAR ID:
- 10374428
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 124
- Issue:
- 9
- ISSN:
- 2169-9380
- Page Range / eLocation ID:
- p. 7543-7552
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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