A study on the effects of solar wind and interplanetary magnetic field on geomagnetic H-component during geomagnetic storms

During geomagnetic storms, the geomagnetic H component is depressed which is preceded by a sudden storm commencement (SSC) or not and this is categorized as sudden or gradual storms. Using the method of cross correlation analysis, we have studied the associations of geomagnetic H components at four low latitude stations at longitudinal separations of 145° - 215° with solar wind density and interplanetary magnetic field (IMF) B during the four most intense sudden and four most intense gradual geomagnetic storms in solar cycle 23. In addition to dawn-dusk responses, how the ionospheric and magnetospheric currents respond to these variations at low latitudes during geomagnetic storms will be determined. Results show that profiles of cross correlation coefficients against time lags were superposed and had peak associations at zero time lags during each event for both parameters. Also there was no dawn-dusk variation in the profiles which implies that the magnetosphere responds uniquely to sources of external origin during geomagnetic storms at low latitudes.. Key words: Geomagnetic storms, solar wind and interplanetary magnetic field (IMF) parameters, geomagnetic H components.