Large-scale structure of solar wind and geomagnetic phenomena

Abstract

In this work I propose a method for determining the solar wind parameters at distances from the Sun more than 1AU. The method is based on formulas for the scintillation indices and spectra for the interplanetary plasma with the large-scale flow structure. According to the results of observations of scintillations performed at the Ukrainian decameter radio telescope UTR-2, I analyzed the structure of the solar wind flows at different periods of the 23–24th solar cycles. The results of the work reveal that the speed of solar wind flows, which cause moderate geomagnetic storms with Ap≤66, was 590±40km/s. This is on average lower than that for the quasi-stationary fast solar wind, but higher than that for the slow solar wind. Solar wind disturbances which triggered geomagnetic storms showed a noticeable growth of solar wind velocity within a wider range of helio-latitudes comparing with disturbances which did not trigger geomagnetic storms. These results can be used to improve methods of forecasting magnetic storms on Earth.