Heliosphere for a wide range of interstellar magnetic field strengths as a source of energetic neutral atoms

TL;DR

This paper uses MHD simulations to explore how varying interstellar magnetic field strengths influence heliosphere structure and ENA fluxes, revealing a 'two-stream' configuration consistent with IBEX observations and the 'split tail' effect.

Contribution

It demonstrates that the heliosphere can exhibit a 'two-stream' structure across a range of magnetic field strengths, explaining observed ENA flux features.

Findings

Heliosphere shows a 'two-stream' structure for magnetic fields around 20 μG.

ENA fluxes exhibit a 'split tail' feature similar to IBEX data.

The 'split tail' effect is mainly caused by the solar wind's fast and slow components.

Abstract

Observations of the energetic neutral atoms (ENAs) of heliospheric origin by IBEX differ from expectations based on heliospheric models. It was proposed that the structure of the heliosphere may be similar to the "two-stream" model derived in 1961 by Parker for the case of strong interstellar magnetic field. Using MHD simulations, we examine possible structure of the heliosphere for a wide range of interstellar magnetic field strengths, with different choices of interstellar medium and solar wind parameters. For the model heliospheres, we calculate the fluxes of ENAs created in the inner heliosheath, and compare with IBEX observations. We find that the plasma flow in the model heliospheres for strong interstellar field ($\sim$20 $\mu$G) has a "two-stream" structure, which remains visible down to $\sim$5 $\mu$G. The obtained ENA flux distribution show the features similar to the "split tail" effect observed by IBEX. In our model, the main cause of this effect is the two component (fast and slow) solar wind structure.