A case study of subauroral ion drift velocity jets by means of dynamics explorer-2 and intercosmos bulgaria-1300 satellites data

Abstract

Satellites INTERCOSMOS “Bulgaria-1300” (ICB-1300) and Dynamics Explorer-2 (DE-2) were launched close together early in August 1981. The satellite data base from both DE-2 and ICB-1300 covers almost a two years period. Data from both satellites were used to examine the longitudinal behavior of a few selected simultaneous subauroral ion drift (SAID) events in the late evening and earlier morning hours of magnetic local time (MLT). SAID velocity jets occur as a narrow region at the equatorward edge of the auroral oval in the westward direction in the evening hours, simultaneously in both hemispheres. It is shown, that the polward component of the DC electric field measured from ICB-1300 corresponds well to the ion drift velocity jets observed in the Ion Drift Meter (IDM) on DE-2 with some longitudinal extent of more than three hours MLT in the evening sector. In a specific case (orbit 705 of ICB-1300), we observe downward current associated with a SAID event of about 1.8 μA/m 2, corresponding to the previously reported current measurements on DE-2 (orbit 796) of about 2.1 μA/m 2. The simultaneous SAID observation taken in the earlier morning hours of the ion drift velocity distribution, shows an existence of velocity jets up to 0130 MLT.