Cross correlation between cosmic‐ray fluctuations and interplanetary magnetic‐field fluctuations

We present a study of the cross correlation between cosmic‐ray intensity fluctuations and the interplanetary magnetic field, using the low‐frequency limit of the theory of the interplanetary scintillations of cosmic rays. Cross‐spectral analysis of the flux of the Alert neutron monitor and simultaneous values of the interplanetary magnetic field components are presented which support the theory. A model of cosmic‐ray fluctuations is described, with effects of gradients and interplanetary sector structure dominating for very low frequencies (f ≲ 5×10 −6 Hz) and magnetic‐field induced interplanetary scintillations of cosmic rays dominating for higher frequencies.