Strong cosmic ray cutoff rigidity decreases during great magnetospheric disturbances

Abstract

The theoretical and experimental cosmic ray cutoff rigidities during great magnetospheric disturbances in November 2004 and May 2005 have been determined. The theoretical geomagnetic cutoffs were calculated by the trajectory tracing method in the magnetic field of Tsyganenko’s magnetospheric model T03, which describes great magnetospheric disturbances (at Dst < 65 nT). The experimental geomagnetic cutoffs were determined by the spectrographic global survey method on the basis of the world network data. The cutoff rigidity decreases at Dst minima can reach 70–80% for theoretical cutoffs and ∼40% for experimental cutoffs at mid latitudes.