On the solar poloidal magnetic field as one of the main factors for maximum GCR intensity for the last five sunspot minima

Abstract

The conditions in the heliosphere are considered during the minimum phase of the sunspot cycle when the intensity of galactic cosmic rays (GCRs) attains its maximum at the Earth. These times of maximum GCR intensity are determined for the last five sunspot minima, including the present one. From the quantitative correlation between the heliospheric factors important to the modulation of GCRs in the heliosphere and the index of high-latitude photospheric magnetic field (all determined corresponding to times of GCR intensity maxima) the conclusion is made that the poloidal magnetic field of the Sun is one of the main governing factors for these heliospheric characteristics. Following this up, the dependence of proton spectra near the Earth on the index as mentioned above for the last five sunspot minima, 21/22 to 24/25, is calculated, also taking into account the strength of the heliospheric magnetic field and the tilt of the heliospheric current sheet, the solar wind speed and the position of the termination shock as the observable factors depending on the high-latitude photospheric magnetic field. The calculations are discussed with special attention paid to the comparison of spectra for the current and previous sunspot minimaa. The conclusion is made on the general dependence of GCR spectra on the poloidal magnetic field of the Sun.