MAGNETOSPHERIC CONTRIBUTION TO LOW-LATITUDE SQ VARIATION

Non-regular features noticed in the quiet-time diurnal variation of H component on 11 December, 1990 (A(p) = 2) and 12 December, 1990 (A(p) = 7) in comparison with the average quiet day variations at a chain of equatorial, low and mid-latitude locations in the Indian longitude zo ne are studied. Stations away from the equatorial electrojet influence exhibited a minimum in the H field around 1600 LT followed by a secon dary peak at 2100 LT. The globally observed anomalously enhanced varia tion in the ''H'' component at low and mid latitude is attributed to t he effect of field aligned current driven by the magnetospheric plasma convection even during relatively quiet intervals. Causative mechanis m to offset this peculiar feature, at equatorial locations is also dis cussed.