Energetic ions as remote probes of X type neutral lines in the geomagnetic tail

Journal Article · Wed Jul 01 04:00:00 EDT 1992 · Journal of Geophysical Research; (United States)

OSTI ID:7258974

Speiser, T W ^[1]; Martin, Jr, R F ^[2]

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1. Univ. of Colorado, Boulder (United States) NOAA, Boulder, CO (United States)
2. Illinois State Univ., Normal (United States)

Martin and Speiser (1988) have predicted ridges in the velocity space distribution function as a signature of the interaction of energetic ions with an X type neutral line in the geomagnetic tail. In this paper the authors study the properties of these ridges as the observation point is moved relative to the X line, as phase angle is varied, and the effect of the ridges on initial distributions with a loss cone. With the ridges, one can remotely sense not only the presence of an X line, but also, potentially, the distance from the X line, whether the observer is earthward or tailward of the X line, and the vertical position within the current sheet. An initially tailward flowing distribution causes asymmetries in distributions earthward versus tailward of the neutral line. These asymmetries are due to the fact that part of the distribution below the ridge comes from initially earthward (tailward) particles when the modeling point is earthward (tailward) of the neutral line. The accelerated beam is not predicted inside the current sheet at x = L but close to the sheet center a perpendicular bulk flow is predicted. Spatially, the ridge is found to move to larger pitch angles as the observation point approaches the neutral line in the plasma sheet boundary layer. As the observation point moves toward the current sheet center, the ridge stays at about the same pitch angle, but then tends to be diminished very near the center where a perpendicular bulk flow is found. Chaotic pitch angle scattering can fill even a relatively large (10{degree}), initially empty loss cone. Thus chaotic pitch angle scattering may be a dominant mechanism to produce nightside proton isotropy in the auroral zones, as suggested by Sergeev et al. (1983).

• OSTI ID: 7258974
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 97:A7; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
AURORAL ZONES
BARYONS
DISTRIBUTION
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELEMENTARY PARTICLES
FERMIONS
HADRONS
INTERACTIONS
IONIC COMPOSITION
ISOTROPY
LOSS CONE
MAGNETOTAIL
NUCLEONS
PLASMA SHEET
PLASMA WAVES
PROBES
PROTONS
SCATTERING
SPATIAL DISTRIBUTION