INVESTIGATION OF S3-2 SATELLITE DATA FOR LOCAL TIME-VARIATION OF ENERGETIC ELECTRON-PRECIPITATION

Data on precipitating electrons from the S3-2 satellite were investiga ted for local time variation at four L = 4 stations in the southern he misphere. The equatorial pitch angles of electrons mirroring at 100 km , assumed to be the edge of the bounce loss cone, are calculated for L = 4 using the International Geomagnetic Reference Field for the epoch of the S3-2 data, along with the variation in mirror altitude per deg ree of equatorial pitch angle. The largest obstacle to the investigati on was uneven sampling in terms of local time for all of the stations. However, this situation was improved upon by the use of S3-2 measurem ents at the conjugate locations of the four stations which provided ad ditional data on electrons in the southern hemisphere bounce loss cone . Evidence for an effect of the dawn-to-dusk geoelectric field was fou nd at two of the stations, Halley Bay and Siple, in the form of a mini mum in electron precipitation at dusk. However, the present study does not completely resolve the question of local time modulation of elect ron precipitation at L = 4 in the southern hemisphere. Furthermore, wh ile the average precipitation was lowest at the Kerguelen site, as wou ld be expected on the basis of drift loss cone (DLC) theories, the int ensity at that site exceeds the level that is expected on the basis of these DLC theories.