Cusp current modeling: A systematic approach

Journal Article · Tue Mar 01 04:00:00 EST 1994 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/93JA03473· OSTI ID:29014

Mei, Y; Crooker, N U; Siscoe, G L ^[1]

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1. Univ. of California, Los Angeles, CA (United States)

The authors describe the achievement of a significant step in a program whose ultimate goal is a self-consistent model that matches cusp currents from both ionospheric and magnetospheric sources. Building on existing models, the mapping is confined to the vicinity of the cusp, simulating limited direct communication with the solar wind, as mandated by recent observations. The mapped area is then inserted into the dayside gap of a purely ionospheric expanding polar cap model. The resulting two-cell convection patterns have a pronounced kink in the antisunward flow contours at the poleward boundary of the cusp area, where it joins the expanding polar cap. A similar kink appears in the Heppner-Maynard empirical patterns; the model implies that it marks the boundary where the ionosphere takes control from the solar wind. The model serves as a first tool for identifying Birkeland current types and causes. Three types arise: (1) Currents border the open cusp like region 1 currents bordering a steady state, mini-polar cap. (2) Within the cusp, currents arise from curvature of the equipotentials which, when mapped to the magnetopause, correspond to flow directed away from the merging line, representing merging outflow. (3) The usual region 1 currents line the polar cap boundary along the flow reversals of the two convection cells as a result of polar cap expansion; they are the ionospheric response to the applied electric field. Thus the model predicts two types of region 1 currents, driven directly and indirectly by the solar wind, plus a set of pure cusp currents. Together they form the familiar overlapping pattern in the cusp region deduced from observations. 68 refs., 3 figs.

• OSTI ID: 29014
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A3 Vol. 99; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
EARTH MAGNETOSPHERE
ELECTRIC CURRENTS
ELECTRIC FIELDS
IONOSPHERE
MATHEMATICAL MODELS
POLAR CUSP
SOLAR WIND