Ionospheric traveling convection vortices observed near the polar cleft: A triggered response to sudden changes in the solar wind

Abstract

Analysis of 20‐second resolution magnetometer data from an array of temporary stations operated around Søndre Strømfjord, Greenland during the summer of 1986 shows the signatures of localized ionospheric traveling convection vortices. An example of an isolated event of this kind observed near 08 local time is presented in detail. This event consists of a twin vortex pattern of convection consistent with the presence of two field‐aligned current filaments separated by about 600 km in the east‐west direction. This system of currents is observed to move westward (tailward) past the array of stations at about 4 km/sec. The event is associated with relative quiet time ionospheric convection and occurs during an interval of northward IMF. It is, however, associated with a large fluctuation in both the Z and Y components of the IMF and with a large sudden decrease in the solar wind number density. The propagation of the system is inconsistent with existing models of FTE current systems, but nevertheless appears to be related to a readjustment of the magnetopause boundary to a sudden change in the solar wind dynamic pressure and/or to a change in reconnection brought about by a sudden reorientation of the IMF.

Occurrence statistics of magnetic impulsive events

“…A large portion of MIEs result as the magnetic signature of ionospheric traveling convection vortex (TCV) events as first demonstrated by Friis-Christensen et al (1988) and Glassmeier et al (1989). Potentially, MIEs can be caused by any of a long list of processes in the outer magnetosphere.…”

Travelling convection vortices in the ionosphere map to the central plasma sheet

“…As is evident from the analysis of the rotation of the convection vectors [see Fig. 4 of Friis-Christensen et al (1988)], the centres of the twinconvection vortex system pass just overhead the stations SKT and DYB at 1013-1014 UT. The vortex system travels from east to west and the locations of the leading vortex over these stations are marked (large circles) in Fig.…”

“…This famous event of Friis-Christensen et al (1988), appearing on the cover of the Geophysical Research Letters, was observed over western Greenland between 1005 and 1020 UT on 28 June 1986. As is evident from the analysis of the rotation of the convection vectors [see Fig.…”

“…1. a Geographic map of the magnetic stations (small filled squares) and the locations of the TCV centres for the event of Friis-Christensen et al (1988). In addition, the DMSP satellite trajectories are displayed and on these the detected precipitation boundaries are marked according to the legend in the figure.…”

“…The first event is the very first, defining TCV event described by Friis-Christensen et al (1988) in their pioneering paper. Next is the well-known event studied by Vogelsang et al (1993), unique in that the field-aligned currents of the TCV are inferred using the VIKING satellite measurements.…”