Interactions Between the Ionosphere and the Magnetosphere for Sq and L Variations


  • S. Matsushita


After a short discussion of the dynamo theory for producing electric current systems for Sq and L variations, results of mapping these dynamo-region electrostatic fields into the magnetosphere are briefly presented. The mapped electrostatic fields, together with the earth's main magnetic field, produce drift motions of magnetospheric plasma particles. Using the same but reversed mapping procedure, magnetospheric electrostatic field effects on the dynamo region are discussed. Highly localized geomagnetic variations during relatively quiet periods can be explained by this effect. Also a possibility of producing Sq-type electric currents in the dynamo region by the magnetospheric electrostatic fields caused by motions in the plasmasphere is examined. This magnetospheric effect on Sq may be greater than other effects due to magnetospheric electric currents (such as magnetopause, tail, and quiet-ring currents). It is concluded that future direct measurements of electrostatic fields (or electrostatic drifts) may determine which of the two mechanisms (dynamo action or plasmaspheric motions) is the major cause of the production of the ionospheric Sqcurrent system, although the dynamo action seems to be the main cause of L variation.