Field-aligned currents and convection patterns in the southern polar cap during stable northward, southward, and azimuthal IMF

摘要

Equivalent ionospheric current patterns are derived from ground-based geomagnetic observations for events on 11-12 November 1979 (B/sub z/0), 24 November 1981 (B/sub z/0), 10-11 January 1980 (B/sub y/ 0) and 25-26 November 1979 (B/sub y/0), when the corresponding IMF (interplanetary magnetic field) conditions remained stable. The 'radar scanning' technique was used to scan the southern polar cap with a chain of unmanned magnetometer stations placed from the cap border to the corrected geomagnetic pole approximately along geomagnetic meridian 110 degrees . During a stable southward IMF a result was obtained, a reversal of antisunward convection flow is identified, and an NBZ-like FAC (field-aligned current) system is restored in the central part of the southern polar cap. It is concluded that there may be an additional NBZ-like system poleward of -85 degrees , which is independent of the IMF and is generated by the quasiviscous interaction between solar-wind plasma and high-latitude lobes of the magnetospheric tail.