IONOSPHERIC CURRENT SYSTEMS ON DAYS OF LOW EQUATORIAL DELTA-H

Examination of the day to day variability in the equatorial electrojet strength, in the Indian region, shows that certain quiet days (A(p) l ess than or equal to 6) are characterized by an abnormally low magnitu de of the jet strength. Geomagnetic field data (H-component) on these abnormal jet days along with the normal jet days From equatorial and l ow latitude stations are subjected to the statistical methodology of P rincipal Component Analysis. Results suggest that the contributions to the diurnal variations on such abnormal days could be accounted for b y an additional noon-time field. The contributing factors for the obse rved spatial distribution of the additional fields that are responsibl e for the changes in low latitude dynamo currents are discussed. (C) 1 998 Elsevier Science Ltd. All rights reserved.