Comparison of irregularity of polar magnetic substorm onsets with the magnetotail plasma dynamics within the hour interval

Comparisons of polar magnetic substorm onsets with the magnetotail plasma dynamics is performed. The hypothesis on unequally probable distribution of substorm onsets, particularly for the cases of absence of plasma acceleration in the magnetotail is well-grounded. The data obtained testify to the anthropogenic effect on substorm onsets the manifestation of which is related to the plasma dynamics in the plasma sheet