In this study, a magnetic dip event in which a small‐scale magnetic dip is embedded within a large‐scale magnetic dip is analyzed based on the observations of the Van Allen Probes. The small‐scale dip is contributed by a sharp electron injection at the energy range of 1 to 10 keV, but the large‐scale dip is contributed by a smooth proton injection at the energy range higher than 10 keV. The formation of dip caused by the suprathermal electrons is supported by the self‐consistent magnetic model. Moreover, the echoes of butterfly distributions of relativistic electrons at the energy range of 0.5 to 3.4 MeV is observed. The time separations of the neighboring butterfly distributions are comparable to the drift periods of the electrons at the different energies. We suggest that the potential nonadiabatic processes in response to the magnetic dips possibly account for the butterfly distribution echoes.
Measurements of plasma lines by the Arecibo incoherent scatter radar are known to have sharp striations in power, varying with the plasma frequency and magnetic aspect angle of the radar beam. We explain these power striations as the manifestation of a suprathermal electron population with peaks in energy at approximately 15, 25, and 45 eV. These energies correspond to sharp features in the photoelectron energy spectra measured by rockets and spacecraft. A new theory is developed to predict the plasma line power for an arbitrary, magnetized suprathermal distribution. The magnetization terms in this theory are shown to contribute substantially to the enhancement of plasma line power through inverse Landau and cyclotron damping of the suprathermal peaks. The theory is applied as a forward model to measurements obtained at Arecibo for different magnetic field aspect angles, showing general agreement with the data. At large magnetic aspect angles the theory reproduces the upper‐hybrid instability which can cause 150 km echoes. The developed theory allows for the suprathermal distribution at a given altitude to be probed across a wide range of energies and pitch angles.
more » « less NSFPAR ID:
 10375613
 Publisher / Repository:
 DOI PREFIX: 10.1029
 Date Published:
 Journal Name:
 Journal of Geophysical Research: Space Physics
 Volume:
 126
 Issue:
 2
 ISSN:
 21699380
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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