High-latitude peculiarities of the geomagnetic SI impulse propagation meridional velocity during sharp decrease of solar wind density

The geomagnetic manifestation of sudden impulse (SI) caused by a sharp decrease of the solar wind dynamic pressure due to the plasma density reduction is considered. The observational data of the magnetometer world network have been analysed. The propagation velocities of the SI signal in the meridional direction by using data of the horizontal component of geomagnetic field in the high-latitude region have been calculated. It is found that at a sharp decrease of the solar wind density the meridional propagation of the SI signal is in the northern direction. In this case, on the day side the propagation velocity is constant but there is a tendency of its increasing in the MLT morning sector. It has been established that the meridional propagation velocity of the SI signal at a sharp decrease of the solar wind density depends on the geomagnetic latitude, i.e. with the rise of latitude the velocity in the auroral zone decreases and in the polar cap it increases.