SOURCE EFFECT ON GEOMAGNETIC INDUCTION VECTORS IN THE FENNOSCANDIAN AURORAL REGION

Geomagnetic induction vectors were calculated at the IMAGE magnetomete r stations in Fennoscandia using hundreds of four-hour events of quiet time variations, and of magnetic storms due to eastward and westward electrojets. Quiet time vectors were found to be very similar to those calculated previously using a set of carefully selected plane wave ev ents. Due to the source effect during electrojet events, the average d irection of the induction vectors may rotate tens of degrees compared to the quiet time. The length generally increases tens of percent, but at the stations MAS and SOR near the electrojet and highly-conducting anomalies, a decrease is observed. If the quiet time induction vector is longer than about 0.50 then the source effect does not affect the direction of the vector remarkably even if the length may change consi derably. If the conductivity anomaly is weaker (quiet time vector shor ter than about 0.30) then the source effect dominates near the electro jet (PEL, MUG, KEV, KIL), but is less important farther away (NUR, OUJ ). If a large number of magnetically quiet events are available of loc al morning hours, no special reduction of the source effect is needed in the research area.