COSMIC-RAY CUTOFF RIGIDITIES IN THE TSYGANENKO MAGNETOSPHERIC FIELD MODEL AT MIDDLE LATITUDES

The cutoff rigidities of cosmic rays are determined in the magnetsophe ric magnetic field simulated by the model of external current system p roposed by Tsyganenko (1987) (Ts87) [Planet Space Sci. 35, 1347]. The diurnal variations of cosmic ray vertical cutoffs are obtained for the midlatitude stations Moscow, Irkutsk, Tbilisi and Alma-Ata, at the mo ment of summer solstice. The cutoffs received are compared with those obtained using the model by Tsyganenko and Usmanov (1982) (TsU82) [Pla net Space Sci. 30, 985] for K-p = 0, 2 and 4. The results show that th e differences between daily averaged geomagnetic cutoff rigidities in the magnetospheric fields of the Ts87 and TsU82 models are not more th an 0.03 GV. Copyright (C) 1996 Elsevier Science Ltd