The physics of the Harang discontinuity
- Boston Univ., MA (USA)
- Rice Univ., Houston, TX (USA)
Absent a source of energetic ions at the flanks of the tail, the westward gradient/curvature drift of E {times} B-convecting plasma results in the depletion of energetic ions from the dawnside of the plasma sheet. This dawnside depletion effect means that, on average, the duskside of the plasma sheet will have higher ion temperatures, pressures, and flux tube contents, and hence, stronger westward cross-tail drift current than the dawnside. The resulting cross-tail divergence of drift current must find closure by means of Birkland currents connecting to the ionosphere. Tailward and poleward of the inner edge region, the divergence of cross-tail current requires upward current from the ionosphere. In the ionosphere, current closure requires electric fields that are directed toward the center of the upward current, i.e., directed equatorward on the poleward side, poleward on the equatorward side. This is precisely the nature of the Harang discontinuity. The region poleward of the Harang discontinuity maps well out into the plasma sheet and provides an eastward component of E {times} B drift to oppose the westward gradient/curvature drift of the ions. This helps keep the flow of plasma sheet ions directed toward the inner plasma sheet, rather than toward the dusk flank of the tail, a point originally made by Atkinson. The region equatorward of the Harang discontinuity maps close to the inner edge of the plasma sheet and results in westward E {times} B drift, increasing the westward flow of plasma azimuthally around the duskside of the inner magnetosphere and toward the dayside magnetopause. Although this scenario can be understood qualitatively, runs were carried out using the Rice convection model (RCM) to examine the ionospheric-magnetospheric coupling implications of this dawnside depletion effect. These runs confirm the above scenario, generally.
- OSTI ID:
- 5188252
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 96:A2; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
HARANG DISCONTINUITY
AURORAL ZONES
EARTH MAGNETOSPHERE
ELECTRIC FIELDS
ION DRIFT
ION TEMPERATURE
IONOSPHERE
MAGNETOPAUSE
MAGNETOTAIL
MATHEMATICAL MODELS
PLASMA DRIFT
PLASMA SHEET
AURORAL OVAL
EARTH ATMOSPHERE
PLANETARY IONOSPHERES
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena