Pulse bursts of geomagnetic pulsations in the frequency range of 0.2-7 Hz as a first signal of interaction between interplanetary shock waves and the magnetosphere

In this article, we analyze the possibility of determining the moment (T 0) of initial contact of the solar wind inhomogeneity with the magnetopause through a comparison of data on geomagnetic field variations registered by terrestrial and satellite magnetometers with high time resolution during sudden commencement (SC). Features of the contact between the interplanetary shock wave (ISW) and the magnetosphere on 23 April 2014 are analyzed. Statistical data on 11 SC events over the period of 19882012 are presented. The broadband electromagnetic pulse registered globally in the frequency range of 0.2-7 Hz was discovered to be a SC precursor. We assume that such a structure may result from the filtering effect of the ionospheric Alfvén resonator on MHD waves generated due to the ISW contact with the magnetopause.