MULTI-INSTRUMENT ANALYSIS OF THE IONOSPHERIC SIGNATURES OF A HOT FLOWANOMALY OCCURRING ON JULY 24, 1996

We present the analysis of a coordinated set of observations from the POLAR ultraviolet imager (UVI), ground magnetometers, incoherent scatt er radar, solar wind monitors, and the DMSP satellite, focused on a tr aveling convection vortex (TCV) event on July 24, 1996. Starting at ap proximately 1036 UT, ground magnetometers in Greenland and eastern Can ada observe pulsations consistent with the passing overhead of a serie s of TCV field-aligned current pairs. Azimuthal scans by the Sondrestr om incoherent scatter radar located near Kangerlussuaq (formerly Sondr estrom), Greenland, at this time show strong modulation in the strengt h and direction of ionospheric plasma flow. The magnetometer pulsation s grow in magnitude over the next hour, peaking in intensity at 1137 U T. Images from the UVI instrument show a localized intensification of auroral emissions over central and western Greenland at 1139 UT. Subse quent images show the intensification grow in strength and propagate w estward (tailward) until approximately 1158 UT, at which time the inte nsification fades, These observations are consistent with the westward passage of four pairs of TCVs over central Greenland. The intensifica tion of auroral emissions at 1139 UT is associated with the leading vo rtex of the fourth TCV pair, thought to be the result of an upward fie ld-aligned current. The modulated flow observed by the radar is the re sult of the strong electric fields associated with the field-aligned c urrent systems responsible for the impulsive TCV as they pass through the field of view of the radar. Measurements taken in the solar wind b y the Wind spacecraft suggest that a pressure change triggers the onse t of TCV activity. A subsequent sudden change in the orientation of th e interplanetary magnetic field produces a hot flow anomaly which form s at the bow shock. We believe that the interaction of the hot flow an omaly with the magnetopause intensified the fourth TCV pair and. produ ced the associated auroral brightening. DMSP particle data indicate th at the TCVs occur on field lines which map to the boundary plasma shee t-low latitude boundary layer interface. The ground observations assoc iated with the hot flow anomaly are the first of their kind and provid e a mechanism to tie an interplanetary magnetic field orientation chan ge into the existing theory that TCVs result from a deformation of the magnetopause.