The Effect of Magnetic Field Dissipation in the Inner Heliosheath: Reconciling Global Heliosphere Model and Voyager Data

TL;DR

This paper introduces a phenomenological magnetic dissipation term in global heliosphere models to reconcile the discrepancy between simulated and observed magnetic field profiles in the inner heliosheath, aligning models with Voyager data.

Contribution

It proposes a new macroscopic dissipation mechanism to account for magnetic energy loss due to unresolved current sheet dynamics in global models.

Findings

Reduces artificial magnetic pile-up in models.

Aligns simulated magnetic field and density with Voyager data.

Shifts termination shock position outward.

Abstract

Global ideal magnetohydrodynamic models of the heliosphere typically predict a greatly exaggerated magnetic field pile-up in the inner heliosheath (IHS), the region between the termination shock and heliopause. However, Voyager 1 and 2 observations show only a gradual increase throughout this region. This mismatch is largely attributed to the simplified assumption of a unipolar solar magnetic field in many global models, which neglects the complex, folded structure of the heliospheric current sheet (HCS). The IHS, especially at low heliolatitudes, contains these compressed sector boundaries, widely considered prime locations for magnetic dissipation via reconnection. To align global model simulations with observations without incurring the prohibitive computational cost of resolving the kinetic-scale current sheet, this work introduces a phenomenological term into the magnetic field induction equation. This term captures the macroscopic effect of magnetic energy dissipation due to unresolved HCS dynamics. It is designed to mitigate the artificial magnetic pile-up, preserve the topological integrity of the magnetic field lines, and avoid explicit magnetic diffusion. This study demonstrates that incorporating a phenomenological dissipation term into global heliospheric models helps to resolve the longstanding discrepancy between simulated and observed magnetic field profiles in the IHS. The proposed mechanism reduces exaggerated magnetic energy (converts it into thermal energy), aligns model output with Voyager measurements of both magnetic field and proton density, and produces the outward shift in termination shock position and a reduction of the IHS thickness. We found that the characteristic time for magnetic field dissipation of about 6 years provides improved agreement with Voyager data in the IHS.