The Model Magnetic Configuration of the Extended Corona in the Solar Wind Formation Region

TL;DR

This paper develops an analytical magnetic field model of the solar corona and heliosphere, combining dipole, ring current, and quadrupole sources to describe the magnetic configuration during different solar activity phases.

Contribution

It introduces a superposition model of magnetic sources that accurately reproduces the solar magnetic field geometry from the corona to the heliosphere, including asymmetries.

Findings

Model matches observed magnetic field geometry during solar minimum.

Incorporates North-South asymmetry via quadrupole term.

Provides a useful interpolation for solar wind and cosmic ray studies.

Abstract

The coupling between small and large scale structures and processes on the Sun and in the heliosphere is important in the relation to the global magnetic configuration. Thin heliospheric current sheets play the leading role in this respect. The simple analytical model of the magnetic field configuration is constructed as a superposition of the three sources: 1) a point magnetic dipole in the center of the Sun, 2) a thin ring current sheet with the azimuthal current density j_{\varphi} ~ r^{-3} near the equatorial plane and 3) a magnetic quadrupole in the center of the Sun. The model reproduces, in an asymptotically correct manner, the known geometry of the field lines during the declining phase and solar minimum years near the Sun (the dipole term) as well as at large distances in the domain of the superalfvenic solar wind in the heliosphere, where the thin current sheet dominates and |B_{r}(\theta)|=const according to Ulysses observations (Balogh et al., 1995; Smith et al., 1995). The model with the axial quadrupole term is appropriate to describe the North-South asymmetry of the field lines. The model may be used as a reasonable analytical interpolation between the both extreme asymptotic domains (inside the region of the intermediate distances ~ (1-10)R_sun) when considering the problems of the solar wind dynamics and cosmic ray propagation theories.