Phenomena of Hysteresis in the Cutoff Rigidity of Cosmic Rays during the Superstorm of November 7–8, 2004

• Published in: Geomagnetism and Aeronomy 2021-07, Vol.61 (4), p.483-491
• Main Authors: Ptitsyna, N. G., Danilova, O. A., Tyasto, M. I.
• Format: Article
• Language: English
• Subjects: Cosmic ray particles; Cosmic ray showers; Cosmic rays; Earth and Environmental Science; Earth Sciences; Geomagnetism; Geophysics/Geodesy; Hysteresis loops; Interplanetary magnetic field; Latitude; Magnetic fields; Magnetic storms; Magnetism; Magnetospheres; Parameters; Rigidity; Solar magnetic field; Solar wind; Solar wind velocity; Stiffness; Topology; Voyager 1 spacecraft; Wind speed; Wind velocities
• ISSN: 0016-7932; 1555-645X; 0016-7940
• DOI: 10.1134/S0016793221040137

The ability of cosmic rays to penetrate the magnetosphere is characterized by the rigidity of the geomagnetic cutoff R , i.e., the stiffness below which the particle flux is cutoff due to magnetic screening. During a magnetic storm, the topology of the magnetic field changes; this causes variations in the cutoff rigidity Δ R . The dependence of Δ R eff (which is calculated from the tracing of the trajectories of cosmic ray particles in a model magnetospheric field) on the parameters of the solar wind, the interplanetary magnetic field, and the magnetosphere during different phases of the strong magnetic storm on November 7–8, 2004 is considered. It is found that the trajectory of Δ R eff , i.e., the successive Δ R eff values with respect to the studied parameters, does not coincide with the trajectory in the recovery phase during the main phase: hysteresis loops form. Narrow hysteresis loops were obtained to relate Δ R eff to the geomagnetic index Dst and the solar wind velocity, while wide loops were obtained to relate it to the electromagnetic parameters. The shape of the hysteresis loops are indicative of a dependence on the latitude of observation: as the latitude increases, the loop area also increases for all studied parameters.