Magnetospheric dynamics and mass flow during the November 1993 storm

Abstract

The National Space Weather Program (NSWP) Storm that occurred in November 1993 is examined with the use of plasma and energetic‐particle measurements on three satellites in geosynchronous orbit. Geosynchronous orbit affords a powerful perspective on magnetospheric dynamics since both tail and dipole processes can be regularly seen, as well as nightside and dayside processes. The major magnetospheric regions analyzed before, during, and after this storm are the outer plasmasphere, the ion plasma sheet, the electron plasma sheet, and the outer electron radiation belt. Ionospheric outflows into the magnetosphere are also observed, and during the storm the magnetosheath and the low‐latitude boundary layer are both seen briefly. The geosynchronous observations indicate that prior to the storm the magnetosphere was very quiet and the outer plasmasphere was filled out to beyond geosynchronous orbit. Extremely large anisotropies were seen in the ion plasma sheet during a compression phase just prior to storm onset. During the storm's main phase the drainage of the outer plasmasphere to the dayside magnetopause was observed, a super dense ion plasma sheet was tracked moving around the dipole, and a superdense electron plasma sheet was seen. The anomalously large plasma pressure on the nightside led to a β > 1 situation at geosynchronous orbit. The β > 1 region spread around the dipole with the super dense ion plasma sheet. The magnetic‐field tilt angle at geosynchronous orbit indicated that strong cross‐tail currents were present very near the Earth. These currents appear to be associated with plasma diamagnetism. Geosynchronous observations indicate that magnetospheric convection was extremely strong. In the electron plasma sheet, severe spacecraft charging occurred. The density of relativistic electrons was observed to peak very early in the storm, whereas the flux of these relativistic electrons peaked much later in the aftermath of the storm.