Time domain structures: What and where they are, what they do, and how they are made
Abstract
Time domain structures (TDS) (electrostatic or electromagnetic electron holes, solitary waves,
double layers, etc.) are ≥1ms pulses having significant parallel (to the background magnetic field) electric
fields. They are abundant through space and occur in packets of hundreds in the outer Van Allen radiation
belts where they produce magnetic-field-aligned electron pitch angle distributions at energies up to a
hundred keV. TDS can provide the seed electrons that are later accelerated to relativistic energies by whistlers
and they also produce field-aligned electrons that may be responsible for some types of auroras. These
field-aligned electron distributions result from at least three processes. The first process is parallel acceleration
by Landau trapping in the TDS parallel electric field. The second process is Fermi acceleration due to
reflection of electrons by the TDS. The third process is an effective and rapid pitch angle scattering resulting
from electron interactions with the perpendicular and parallel electric and magnetic fields of many TDS.
TDS are created by current-driven and beam-related instabilities and by whistler-related processes such as
parametric decay of whistlers and nonlinear evolution from oblique whistlers. New results on the temporal
relationship of TDS and particle injections, types of field-aligned electron pitch angle distributions produced
by TDS, the mechanisms for generation of field-aligned distributions by TDS, the maximum energies of
field-aligned electrons created by TDS in the absence of whistler mode waves, TDS generation by oblique
whistlers and three-wave-parametric decay, and the correlation between TDS and auroral particle precipitation,
are presented.
Origin : Publisher files allowed on an open archive
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