GLE events in 24^th solar cycle

Polar Geophysical Institute, 184209 Apatity, 26A Academgorodok, RUSSIA

¹ Corresponding author: balabin@pgia.ru

Abstract

Started in 2009, the 24^th solar cycle is going to end. In 2015, the solar activity was at its maximum, turning down. According to many indices, this cycle turned out to be abnormal. For instance, in the previous, the 23^rd cycle, the index such as the number of solar spots was as high as 175, compared with that of the 24^th cycle, not exceeding 100. According to the number of GLE-events (ground level enhancement of solar cosmic rays, observed on neutron monitors), the current cycle also differs greatly from the previous ones. In the 23^rd cycle, the number of great GLE-events was as high as four, and that of small and moderate being five. In the 24^th cycle, only two GLE-events were recorded: GLE 71 (17.05.2012) и GLE 72 (10.09.2017), with the last event being of small amplitude (5%). The presence of the neutron monitors network data enables calculation of the energy spectrum and other parameters of solar cosmic rays. The GLEevents are processed by special technique developed at PGI. It is aimed at solving the inverse problem: based on the data from the world neutron monitors network, to obtain the parameters of solar cosmic rays energy spectra. Like the previous ones, GLE-events 71 and 72 were processed by this technique. The energetic spectra obtained were compared with those in other events of the previous cycles