Magnetospheric Response To The Ground-Level Enhancement Of Solar Cosmic Rays On May 2, 1998

The ground-level enhancement (GLE) of solar cosmic rays (SCR) on May 2, 1998, occurred against a strongly disturbed interplanetary medium the Earth's magnetosphere. The worldwide network of neutron monitors registered an intricate pattern of the increase profiles, which was analyzed using the asymptotic approach directions of solar protons calculated in terms of the geomagnetic field model of Tsyganenko [1989]. It was shown that the peculiarities of the increase profiles at different stations could be explained by an IMF direction deviating significantly from the Archimedean spiral and the bidirectional anisotropy of relativistic SCR, on the one hand, and by the specific conditions of penetration of solar protons into the disturbed magnetosphere, on the other. In the particular event under consideration, the anisotropic flux of relativistic solar protons recorded in the high-latitude afternoon sector at Oulu could have arrived from the noon magnetopause.