Experimental evidence for direct penetration of ulf-waves from solar wind and their possible effect on acceleration of radiation belt electrons

We analyzed the event of 12-19 March 2009 when the Earth's magnetosphere was flowed around by medium high-velocity solar wind flux carrying ULF-waves of millihertz range. The flux caused a weak magnetic storm (Dstmin = -28 nT). Since March 13, energetic electron fluxes up to relativistic energies began to increase in the magnetosphere. The comparison of spectra of ULF-oscillations observed in the solar wind, in the magnetosphere, and on the Earth's surface showed the stable common spectral peak in the range 3-4 mHz. This fact can be interpreted as an evidence for direct penetration of waves from the solar wind to the magnetosphere. Possible scenarios of a role of oscillations in accelerating electrons of both medium (Е > 0.6 MeV) and high (Е > 2.0 MeV) energies in the radiation belt are discussed. From the comparison of the analyzed event with the moderate magnetic storm of 21-22 January 2005 we can conclude about favourable conditions for analyzing the interaction between the solar wind and the magnetosphere during the deep minimum of solar activity.