ИСТИНА

Earlier, we showed that the Earth’s magnetosphere activity in the solar cycle depends from the dynamics of the solar wind β parameter (equal to the ratio of plasma pressure to magnetic pressure). At β~1, the chaotic mode is observed in the magnetosphere; at β>1, the periodic one. In this work the influence of the β parameter on the intensity and duration of geomagnetic storms is studied. For the analysis about 2000 magnetic storms, we used geomagnetic storm catalog taken from the World Data Center on Solar-Terrestrial Physics (Russia) (http://www.wdcb.ru/stp/geomag/geomagnetic_storms.ru.html) and the series of hourly values of the parameters of the Earth’s magnetosphere and solar wind from the OMNI database (https://spdf.gsfc.nasa.gov/pub/data/omni/low_res_omni/) from 1964 to 2010. The study was carried out by the method of superposed epochs on an interval of 10 days before and after the starting of the storm. The moment of the storm beginning was chosen as the reference mark to synchronize the sequences of the Earth’s magnetosphere or the solar wind parameters. The dynamics of the β parameter and Dst-index during the development of weak, moderate and strong magnetic storms is analyzed. It is shown that the dynamics of the Dst-index during a storms correlates with the dynamics of the β parameter regardless of the storm intensity. Moreover, in the main phase of the storm, the value of the parameter β ~ 1 at background values 2 <β <3. We note that the level of turbulent fluctuations in the solar wind reaches its maximum values exactly at β ~ 1. The obtained results indicate that solar wind turbulence plays a significant, and possibly a determinative role in the development of geomagnetic storms. This study was carried out with the financial support of state task no. 0144-2014-00116.