High-resolution energetic particle measurements at 6. 6R/sub E/ 3. Low-energy electron anisotropies and short-term substorm predictions

Journal Article · Sun Oct 01 04:00:00 EDT 1978 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA083iA10p04863· OSTI ID:6270028

Baker, D N; Higbie, P R; Hones, Jr, E W; Belian, R D

Multiple detectors giving nearly complete 4..pi.. coverage of particle pitch angle distributions have provided high resolution measurements (in energy and time) of 30- to 300-keV electrons. Data from a spacecraft (1976-059A) in geostationary orbit show a remarkably consistent sequence of variations of the electron anisotropy before and during magnetospheric substorms. For periods typically 1--2 hours prior to the onset of substorms, electron distributions, peaked along the direction of the local magnetic field, are observed in the premidnight sector. These cigarlike anisotropies are accompanied by a local taillike magnetic field which may develop further during the event. At substorm onset an abrupt transition usually occurs from the cigar-shaped distributions to pancake-shaped distributions. This anisotropy sequence may be due to the buildup and subsequent release of stresses in the magnetotail; the cigar phase may also be due to associated processes at the dayside magnetopause causing a loss of 90/sup 0/ pitch angle particles. The present observations, based on approx.100 events, appear to provide a predictive tool for assessing the probability of occurrence of a substorm.

• Research Organization: University of California, Los Alamos Scientific Laboratory Los Alamos, New Mexico 87545
• OSTI ID: 6270028
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 83:A10; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANGULAR DISTRIBUTION
ANISOTROPY
CHARGED PARTICLE DETECTION
DETECTION
DISTRIBUTION
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
INCLINATION
KEV RANGE
LEPTONS
MAGNETIC BAYS
MAGNETOSPHERE
RADIATION DETECTION
TRAPPED ELECTRONS