What is happening near S _q focus?

Rocket measurements of electron temperatures (T _e ) in the E region over Kagoshima Space Center, Japan, carried out in a series of experiments conducted from 1970 to 1988 are analysed in this paper. All the 13 flights whose results are presented here took place around 11 AM, close to the S _q current intensity maximum. Anomalously high electron temperatures associated with large increases of high energy tail electron population were observed whenever the estimated S _q current vortex was very close to the launch site. Such anomalous temperatures were observed only in local winter months. A mechanism for the anomalous heating is proposed based on the solsticial asymmetry of the S _q electric potentials and the resulting field-aligned current that could flow from winter to summer hemisphere.