SOLAR CONTROL OF THE DAY-TO-DAY VARIABILITY IN THE EQUATORIAL GEOMAGNETIC-FIELD

Utilizing a 2-month period of highly variable solar activity, the sola r control of the day-to-day changes in the geomagnetic signatures of i onospheric features have been studied for regions close to the equator ial electrojet and well away from it. Only solar X-rays seem to signif icantly influence the geomagnetic H and D components on such short tim e scales. Sunspots, though often utilized as an index of solar activit y, are not well correlated with ground magnetic field parameters on a daily basis, as pointed out by S Chapman and J Bartels [Geomagnetism, Vol. 1 (Clarendon Press, Oxford), 1940, 234, 376].