Anomalous auroral electron distributions due to an artificial ion beam in the ionosphere

Journal Article · Wed Sep 01 04:00:00 EDT 1982 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA087iA09p07569· OSTI ID:6573941

Moore, T E; Arnoldy, R L; Kaufmann, R L; Cahill, Jr, L J; Kintner, P M; Walker, D N

We report the results of an active experiment in which the auroral ionosphere was perturbed by the operation of an ion gun, which injected approximately 100 mA of 25 eV Ar/sup +/ ions at upgoing pitch angles over a discrete aururol arc. The gun was operated during five periods on the downleg of the flight as the payload descended from 200 km to 120 km altitude along the local magnetic field lines. A brief (<100 ms) negative payload potential excursion was observed at the onset of each gun operation, followed by quasi-steady conditions for the remainder of each period. The major steady effects were (1) the excitation of intense broad band electric field fluctuations, particularly at low frequencies 0--10 kHz, and (2) the appearance of streaming, and isotropic heating in different parts of superthermal electron velocity space. We have explored a scenario that appeals to such a wave spectrum as an obstacle to auroral parallel current and predicts this type of electron behavior. The waves are viewed as traps for the thermal electrons and scatterers of the faster electrons. In this scenario, electron runaway and streaming is expected between the trapping speed and the critical velocity for cyclotron interactions with the waves. These streaming electrons carry the current that would be carried by thermals of energetic electrons in the absence of the waves. Isotropic heating is expected near the critical speed where Doppler resonance occurs and is found near 12000 km/s (approx.50 v/sub t/e, where v/sub t/e is the electron thermal speed). It may be inferred that waves are excited primarily at wavelengths of several meters and longer. A current approx.1 ..mu..mA m/sup 2/ is carried by the streaming electrons. Energetic considerations suggest that the heated electrons derive their energy from an external source rather than from the ion beam itself; the auroral generator appears to be more than adequate.

• Research Organization: Space Science Center, University of New Hampshire, Durham, New Hampshire 03824
• OSTI ID: 6573941
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 87:A9; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
&amp; Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
BEAMS
DISTRIBUTION
DISTURBANCES
EARTH ATMOSPHERE
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
ION BEAMS
IONOSPHERE
LEPTONS
PLANETARY IONOSPHERES
SPATIAL DISTRIBUTION