SOLAR-FLARE EFFECTS ON ZONAL AND MERIDIONAL CURRENTS AT THE EQUATORIAL ELECTROJET STATION, ANNAMALAINAGAR

During the normal electrojet period, a solar flare produces a positive change in the horizontal (H) field, negative changes in the eastward (Y) field and a negative change in the vertical (Z) field at a norther n electrojet station. On average, the Delta Y is about 40% of Delta H. During a counter electrojet period, Delta H, due to a solar flare, is negative and Delta Y and Delta Z are positive. During a partial count er electrojet period, Delta H may be smaller at equatorial stations co mpared with other low latitude stations, and Delta Y may be positive, or sometimes of very small magnitude. The observed change of Delta Y a t an electrojet station is suggested to be the combined effect of the flare on the associated Sq current system and on electrojet-related me ridional currents. These data confirm the seat of the equatorial merid ional current to be in the ionospheric E layer. (C) 1996 Elsevier Scie nce Ltd