Letter to the Editor

Constraints on the heliospheric magnetic field variation during the Maunder Minimum from cosmic ray modulation modelling

¹ Institut für Astrophysik und Extraterrestrische Forschung der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: kscherer@astro.uni-bonn.de
² Institut für Theoretische Physik IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany e-mail: hf@tp4.rub.de

Corresponding author: K. Scherer, kscherer@astro.uni-bonn.de

Received: 6 October 2003
Accepted: 24 November 2003

Abstract

Using a dynamic multifluid model of the global heliosphere (Bonn model) we found, that the variation of the heliospheric interface and the corresponding cosmic ray modulation can not be made responsible for the increase of the mean cosmic ray flux during the Maunder Minimum. This is because the diffusion coefficients of cosmic rays required to simulate their flux increase need an “intrinsic” time variation, i.e. one that can be attributed to the solar or heliospheric magnetic field, thus, to the solar dynamo. Our study of the diffusion coefficients constrains the decrease in the strength of the solar magnetic field during the Maunder Minimum to about a factor of 4.