First solar-terrestrial storms in cycle 24 of solar activity

The dynamics of the occurrence frequency and intensity of solar-terrestrial storms at the current solar cycle (cycle 24) onset (2007–2011) is considered. The storms were identified based on the moving semidiurnal average planetary index of activity, beginning from Ap* ≥ 30. It has been established that 12, 11, and 2 only moderate storms (Ap* = 30–49), which were randomly distributed during the year, were successively observed in the first three years. After a prolonged period without storms (August 2009–March 2010), a series of storms with mixed or only moderate activity, which were regularly distributed over the seasons (ecliptic longitudes) from April to August, started appearing beginning from the storm of April 1–6, 2010. This period followed the tendency toward the transformation of the slowly rotating four-sector structure (Large-Scale Open Solar Magnetic Field, LOSMF) from the two-sector structure (March 2010). The first storm in the new cycle (April 2010) was very powerful and originated owing to the successive destabilization of the complex of two magnetic filamentary ropes. It is interesting that the origination of a new LOSMF sector was associated with a 27-day interval, during which thermal neutrons appeared at Kamchatka and volcanoes erupted in Iceland, and a strong earthquake occurred in March 2011 in Japan when the Earth was located precisely in this sector.