Superthermal ion signatures of auroral acceleration processes

Journal Article · Fri Feb 01 04:00:00 EST 1985 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA090iA02p01611· OSTI ID:5887097

Moore, T E; Chappell, C R; Lockwood, M; Waite, Jr, J H

The retarding ion mass spectrometer on the Dynamics Explorer 1 spacecraft has generated a unique data set which documents, among other things, the occurrence of non-Maxwellian superthermal features in the auroral topside ionosphere distribution functions. In this paper, we provide a representative sampling of the observed features and their spatial morphology as observed at altitudes in the range from a few thousand kilometers to a few earth radii. At lower altitudes, these features appear at auroral latitudes separating regions of polar cap and subauroral light ion polar wind. The most common signature is the appearance of an upgoing energetic tail having conical lobes representing significant ion heat and number flux in all species, including O/sup +/. Transverse ion heating below the observation point at several thousand kilometers is clearly associated with O/sup +/ outflows. In some events observed, transverse acceleration apparently involves nearly the entire thermal plasma, the distribution function becomes highly anisotropic with T/sub perpendicular/>T/sub parallel/, and may actually develop a minimum at zero velocity, i.e., become a torus having as its axis the local magnetic field direction. At higher altitudes, the localized dayside source region appears as a field aligned flow which is dispersed tailward across the polar cap according to parallel velocity by antisunward convective flow, so that unflowing low energy O/sup +/ ions appear well within the polar cap region. While this flow can appear beamlike in a given location, the energy dispersion observed implies a very broad energy distribution at the source, extending from a few tenths of an eV to in excess of 50 eV.

• Research Organization: Space Science Laboratory, NASA Marshall Space Flight Center, Huntsville, Alabama 35812
• OSTI ID: 5887097
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 90:A2; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
AURORAL ZONES
BEAMS
CHARGED PARTICLES
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
EXPLORER SATELLITES
FUNCTIONS
ION BEAMS
ION DRIFT
ION TEMPERATURE
IONOSPHERE
IONS
OXYGEN IONS
PLANETARY IONOSPHERES
PLASMA ACCELERATION
SATELLITES