FAST observations in the downward auroral current region: Energetic upgoing electron beams, parallel potential drops, and ion heating

C. W. Carlson, J. P. McFadden, R. E. Ergun, M. Temerin, W. Peria, F. S. Mozer, D. M. Klumpar, E. G. Shelley, W. K. Peterson, E. Moebius, R. Elphic, R. Strangeway, Cynthia A Cattell, R. Pfaff

Research output: Contribution to journalArticle

250 Scopus citations

Abstract

Observations of plasma particles and fields by the FAST satellite find evidence of acceleration of intense upgoing electron beams by quasi-static parallel electric fields. The beam characteristics include a broad energy spectrum with peak energies between 100 eV and 5 keV, perpendicular temperatures less than 1 eV, and fluxes greater than 109/cm2sec. Diverging electrostatic shocks associated with the beams have integrated potentials that match the beam energy. These beams are found in regions of downward Birkeland current and account for the total field-aligned current when they are present. The most energetic ion conics in the auroral zone are found coincident with these beams, in agreement with the model for "trapped" conics. The measured particle densities of the electron beams and associated ion conics are approximately equal and typically range from 1 to 10 cm-3, with no evidence for additional cold density. The beams are seen frequently at altitudes between 2000 and 4000 km in the winter auroral zone. Their probability of occurrence has a strong dependence on season and altitude and is similar to that for upgoing ion beams in the adjacent upward current regions. This similarity suggests that the density and scale height of ionospheric ions play an important role in the formation of both types of beams.

Original languageEnglish (US)
Pages (from-to)2017-2020
Number of pages4
JournalGeophysical Research Letters
Volume25
Issue number12
DOIs
StatePublished - Jan 1 1998

Fingerprint Dive into the research topics of 'FAST observations in the downward auroral current region: Energetic upgoing electron beams, parallel potential drops, and ion heating'. Together they form a unique fingerprint.

Cite this