Ratio of mean free paths normal and parallel to IMF for the Nagoya muon telescope
2019 July 22
The galactic cosmic ray (GCR) solar diurnal anisotropy (SDA) data of Nagoya vertical muon telescope (NagV-MT) are used to compute the ratio () of GCR free paths normal and parallel to the mean interplanetary magnetic field (IMF) B. They are compared to the corresponding values for the neutron monitors (NMs) of the global network, computed earlier, for three sunspot cycles (21-23) and parts of the other two (19, 24). Current modulation theories do not provide any guidance for the value and rigidity dependence of α. We use a flat heliospheric current sheet and master equations derived by Ahluwalia and Dorman  for computing using SDA data for NagV-MT. Preliminary results for its rigidity dependence and correlation with solar activity for positive (p) and negative (n) polarity intervals of B at 1 AU are noted. Results challenge the validity of old results and conceptual understanding of GCR modulation processes in the heliosphere.