OBSERVATIONS OF CONVECTION VORTICES IN THE AFTERNOON SECTOR USING THESUPERDARN HF RADARS

Observation of convection vortices using the new SuperDARN HF radars a re presented. The velocity field derived from the overlapping fields o f view of the new HF radars at Kapuskasing, Ontario, and Saskatoon, Sa skatchewan, Canada, often image the portion of the convection pattern near the convection reversal boundary. Observations from near the conv ection reversal boundary in the afternoon sector of October 22, 1993, showed two convection vortices evolving within the field of view of bo th radars. The first vortex appeared at about 2120 UT and the second a t about 2145 UT: 1446 MLT and 1512 MLT, respectively. The vortices wer e roughly 900 km in diameter and moved tailward with a velocity of abo ut 600 m/s. At the times the vortices were observed by the radars, gro und-based magnetometers of the CANOPUS and MACCS chains show transient deflections of near 100 nT, and the GOES 6 and GOES 7 satellite magne tometers showed significant decreases in the magnetospheric magnetic f ield strength. Data from the Geotail satellite magnetometer lagged by an appropriate time interval indicated that there were southward turni ngs of the interplanetary magnetic field that coincided with the decre ases of magnetospheric magnetic field strength, The observations diffe r in many respects from previously published vortex observations. It i s theorized that the vortices were caused by the Kelvin-Helmholtz inst ability at the inner edge of the low-latitude boundary layer.