Satellite and ground-based measurements of the SAP-arc phenomena

Data of the Intercosmos 24 (IC 24) satellite and the ground-based complex optical and ionospheric measurements in the region of the stable auroral red (SAR)-arc are presented. Photometric observations were carried out at the Maimaga station (invariant latitude Lambda =56.5 degrees, geomagnetic longitude lambda(m)=200 degrees) and vertical incidence ionospheric soundings were made at Yakutsk (Lambda =55.6 degrees, lambda(m)=200 degrees) and Zhigansk (Lambda=60.4 degrees: lambda(m)=195 degrees) stations. It is shown that when SAR-arc arises for the interval similar to 15 min, the local minimum of the F-region electron density is formed, and in the ionograms typical signatures of the polarization jet or SAID are observed. Simultaneously, the height of the regular F2 layer increases. This evidences that strong electric field (E similar to 100 mV/m) exists at the F2 layer heights. In this case, in addition to the SAR-arc energy sources, the effect of the ion-frictional heating is turned out to be important. Simultaneous measurements aboard the IC-24 satellite at the altitudes similar to 500 km above the SAR-arc also show 3 divided by 5 times decreased electron density. The electron temperature elevates up to similar to 4500 K. At altitudes of 2400 km the ion density increases by 30 - 40 % and T-e rises up to 6300 K. (C) 1999 Elsevier Science Ltd. All rights reserved.