Equatorial enhancement of SSC amplitudes: Solar activity dependence and effect of electric field.

Abstract

Characteristics of SSC amplitude at low and equatorial latitudes are studied using the data of 332 events observed simultaneously at three stations in the Indian region during the period [1958][1959][1960][1961][1962][1963][1964][1965][1966][1967][1968][1969][1970][1971][1972][1973]. It is shown that during daytime both SSC amplitude in H and its equatorial enhancement increase with increased solar activity. During nighttime also the SSC amplitudes are found to vary with solar activity. The daytime equatorial enhancement of SSC's, which is attributed to the currents in the ionospheric E -layer, shows much sharper variation with solar activity than that shown by conductivity in that layer or the jet current intensity. SSC's which occurred during partial counter electrojet events are examined to determine the effect of change in an ambient electric field on their amplitudes. It is found that a westward ambient electric field leads to a reduction in the equatorial enhancement.