Relation between the Geomagnetic Cosmic Ray Cutoff Rigidity and Solar Wind and Magnetosphere Parameters during the Storm of November 9–10, 2004: Analysis of Hysteresis Effects.

We calculated variations in the cosmic ray geomagnetic cutoff rigidity ΔR_ef during a complex two-stage magnetic storm on November 9–10, 2004, using calculations of particle trajectories in the model magnetic field of the magnetosphere. The response of ΔR_ef to changes in solar wind and magnetosphere parameters reflects the nonsmooth two-stage evolution of this storm. It is found that the curve of changing values that ΔR_ef take as a function of the studied parameters during the main phases of each stage of the storm does not coincide with the curve during the recovery phases, which is a sign of hysteresis. As a result, two hysteresis loops are formed, one for each stage of the storm of November 9–10, 2004. The ambiguous dependence of ΔR_ef values on the studied parameters, which change cyclically during the development of magnetospheric current systems and their subsequent relaxation, is responsible for the formation of the loops. The configuration of two loops similar to those characteristic of dielectric hysteresis seems to be related to the abrupt change from Bz > 0 to Bz < 0, which delimits the stages of the studied storm. [ABSTRACT FROM AUTHOR]