Implications of Solar Magnetograms for the Drifts of Cosmic Rays

Abstract

While gradient and curvature drifts are well-established elements of the propagation of cosmic rays in the heliospheric magnetic field, their perturbation by the Solar activity-induced largescale distortions of dipole-like field configurations even during Solar minima and by magnetic turbulence is an open problem. Various empirical or phenomenological approaches have been suggested to quantify these effects so that they can be straightforwardly incorporated in modulation models covering the 22-year periodicity (including the sign) of Solar activity. These approaches, however, either lack clear physics-based parametrizations (e.g., in terms of the tilt-angle of the heliospheric current sheet) or have been shown to be incompatible with measurements (like a dependence on the normalized turbulence level δB/B). We propose here a new approach to the treatment of drifts over an entire Solar cycle including maximum periods, which is based on Solar magnetograms. This not only provides a physics-based approach to the reduction of drifts during Solar activity maxima but also a treatment that is fully consistent with those MHD models of the Solar wind and the embedded heliospheric magnetic field that exploit Solar magnetograms as inner boundary conditions.