The S1 Shell and Interstellar Magnetic Field and Gas near the Heliosphere

TL;DR

This study models the Loop I superbubble as two magnetic shells with the Sun embedded in the S1 shell, analyzing interstellar magnetic field data and interstellar material distribution near the heliosphere.

Contribution

It presents a viable model of the local interstellar medium as two magnetic subshells of Loop I, linking magnetic field structure with interstellar material distribution near the Sun.

Findings

The S1 shell model aligns with local interstellar magnetic field data.

CaII column densities correlate with interstellar radiation field strength.

The magnetic symmetry of Loop I matches the CMB dipole symmetry.

Abstract

Many studies of the Loop I magnetic superbubble place the Sun at the edges of the bubble. One recent study models the polarized radio continuum of Loop I as two magnetic shells with the Sun embedded in the rim of the 'S1' shell. If the Sun is in such a shell, it should be apparent in both the local interstellar magnetic field and the distribution of nearby interstellar material. The properties of these subshells are compared to optical polarization data that trace the nearby interstellar magnetic field (ISMF), and the distribution of interstellar FeII and CaII within about 55 pc of the Sun. The result is that a model of Loop I as composed of two magnetic subshells is a viable description of the distribution of nearby low density ISM. Column densities of the recombinant ion CaII are found to increase with the strength of the interstellar radiation field, rather than with star distance or total pathlength through the two magnetic subshells. As found earlier, the symmetry of the dipole moment of the cosmic microwave background corresponds to the symmetries of the heliosphere and local ISMF (to within 10 degrees).