Probing Heliospheric Asymmetries with an MHD-kinetic Model

TL;DR

This paper uses a sophisticated MHD-kinetic model to analyze heliospheric asymmetries caused by the interstellar magnetic field, incorporating recent Voyager and other observational data to improve understanding of the local interstellar medium.

Contribution

It introduces a detailed MHD-kinetic model to study heliospheric asymmetries and the effects of secondary hydrogen atoms on LISM properties and deflections.

Findings

Secondary hydrogen atoms modify LISM properties and cause shock-free deceleration at the heliopause.

Hydrogen atom deflection occurs both in the ISMF-LISM velocity plane and perpendicular to it.

Radio emission data can help constrain the interstellar magnetic field direction.

Abstract

New solar wind data from the Voyager 1 and Voyager 2 spacecraft, together with the SOHO SWAN measurements of the direction that neutral hydrogen enters into the inner heliosheath and neutral helium measurements provided by multiple observations are expected to provide more reliable constraints on the ionization ratio of the local interstellar medium (LISM) and the direction and magnitude of the interstellar magnetic field (ISMF). In this paper we use currently the most sophisticated numerical model of the heliospheric interface, which is based on an MHD treatment of the ion flow and kinetic modeling of neutral particles, to analyze an ISMF-induced asymmetry of the heliosphere in the presence of the interplanetary magnetic field and neutral particles. It is shown that secondary hydrogen atoms modify the LISM properties leading to its shock-free deceleration at the heliopause. We determine the deflection of hydrogen atoms from their original trajectory in the unperturbed LISM and show that it occurs not only in the plane defined by the ISMF and LISM velocity vectors, but also, to a lesser extent, perpendicular to this plane. We also consider the possibility of using 2-3 kHz radio emission data to further constrain the ISMF direction.