IMF intensity and galactic cosmic ray modulation Original Research Article

We have studied the data strings for the interplanetary magnetic field intensity (B), and the neutron monitor (NM) annual mean hourly rates for the period 1964 to 1999, at different global sites. The median rigidity of detector response (Rm) to galactic cosmic ray (GCR) spectrum lies in the range of 10 GV to 33 GV. We relate the observed features of 11 year modulation to the time variations of B and the long term trend in its baseline which are not related to SSN. For example, the minimum GCR intensity for cycle 21 (maximum modulation) occurs in 1982 when B has a high value, 3 years away from SSN maximum. We confirm that the long term trend in the IMF time variations plays a significant role in controlling the recovery from 11 year GCR modulation.