SEASONAL-VARIATIONS IN THE LOW LATITUDE DYNAMO CURRENT SYSTEM NEAR SUNSPOT MAXIMUM

Strong seasonal variations in the equatorial dynamo-induced electric fields have been deduced from incoherent-scatter sounder data. These seasonal variations are studied in this paper using a dynamo model in conjunction with the thermospheric neutral wind system. The E-region dynamo system is studied using an equivalent mesh circuit model. The model contains a detailed magnetic field system, includes the influence of conjugate effects and employs a quadrature synthesis technique to fit experimental and theoretical results. The thermospheric wind system is restricted to two tidal modes; the first evanescent diurnal mode and the semidiurnal mode. The wind systems are converted to geomagnetic coordinates and global dynamo currents and electric fields are derived for equinox and solstice periods. It is shown that the post sunset enhancement in electric field can be explained by this simple E-region dynamo model. © 1979.