Evidence for acceleration of outer zone electrons to relativistic energies by whistler mode chorus
We use plasma wave and electron data from the Combined Release and Radiation Effects Satellite (CRRES) to investigate the viability of a local stochastic electron acceleration mechanism to relativistic energies driven by gyroresonant interactions with whistler mode chorus. In particular, we...
| Main Authors: | , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2002-07-01
|
| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/20/967/2002/angeo-20-967-2002.pdf |
| Summary: | We use plasma wave and
electron data from the Combined Release and Radiation Effects Satellite (CRRES)
to investigate the viability of a local stochastic electron acceleration
mechanism to relativistic energies driven by gyroresonant interactions with
whistler mode chorus. In particular, we examine the temporal evolution of the
spectral response of the electrons and the waves during the 9 October 1990
geomagnetic storm. The observed hardening of the electron energy spectra over
about 3 days in the recovery phase is coincident with prolonged substorm
activity, as monitored by the <i>AE</i> index and enhanced levels of whistler
mode chorus waves. The observed spectral hardening is observed to take place
over a range of energies appropriate to the resonant energies associated with
Doppler-shifted cyclotron resonance, as supported by the construction of
realistic resonance curves and resonant diffusion surfaces. Furthermore, we
show that the observed spectral hardening is not consistent with
energy-independent radial diffusion models. These results provide strong
circumstantial evidence for a local stochastic acceleration mechanism,
involving the energisation of a seed population of electrons with energies of
the order of a few hundred keV to relativistic energies, driven by
wave-particle interactions involving whistler mode chorus. The results suggest
that this mechanism contributes to the reformation of the relativistic outer
zone population during geomagnetic storms, and is most effective when the
recovery phase is characterised by prolonged substorm activity. An additional
significant result of this paper is that we demonstrate that the lower energy
part of the storm-time electron distribution is in steady-state balance, in
accordance with the Kennel and Petschek (1966) theory of limited stably-trapped
particle fluxes.<br><br><b>Key words. </b>Magnetospheric physics
(storms and substorms, energetic particles, trapped) – Space plasma physics
(wave-particle interactions) |
|---|---|
| ISSN: | 0992-7689 1432-0576 |