Disturbed magnetosphere on November 7-8, 2004 and variations of cosmic ray cutoff rigidity: latitude effects

We have studied the latitude behavior of cosmic ray cutoff rigidity and their sensitivity to Bz and By components of the interplanetary magnetic field and geomagnetic activity indices Dst and K p for different phases of the November 7-8, 2004 strong magnetic storm. Cutoff rigidities have been calculated using two methods: the spectrographic global survey method in which the cutoff rigidity is determined from observational data, acquired by the neutron monitor network, and the method in which particle trajectories are calculated numerically in a model magnetic field of the magnetosphere. We have found that the sensitivity of observed cutoff rigidities to Dst changes with latitude (threshold rigidity of stations) is in antiphase with changes in the sensitivity to By . During the recovery phase of the storm, the Dst correlation with By is significantly greater than that with Bz , and the K p correlation with Bz is greater than that with By . The By component is shown to be a predominant driver of the current systems that determine the Dst evolution during the recovery phase.