Evidence for an interstellar dust filament in the outer heliosheath

TL;DR

This paper presents evidence that a polarized starlight filament originates from aligned interstellar dust grains in the outer heliosheath, revealing insights into the magnetic field structure around the heliosphere.

Contribution

It identifies a polarization filament consistent with an origin in the outer heliosheath and links its properties to the local magnetic field and dust grain alignment, proposing a new observational signature.

Findings

Magnetic field aligns with the interstellar flow direction within 6.7 degrees.

The polarization filament is ordered with minimal turbulence.

The filament's axis is approximately 80 degrees from the BV plane.

Abstract

A recently discovered filament of polarized starlight that traces a coherent magnetic field is shown to have several properties that are consistent with an origin in the outer heliosheath of the heliosphere: (1) The magnetic field that provides the best fit to the polarization position angles is directed within 6.7+-11 degrees of the observed upwind direction of the flow of interstellar neutral helium gas through the heliosphere. (2) The magnetic field is ordered; the component of the variation of the polarization position angles that can be attributed to magnetic turbulence is small. (3) The axis of the elongated filament can be approximated by a line that defines an angle of 80+/-14 degrees with the plane that is formed by the interstellar magnetic field vector and the vector of the inflowing neutral gas (the "BV" plane). We propose that this polarization feature arises from aligned interstellar dust grains in the outer heliosheath where the interstellar plasma and magnetic field are deflected around the heliosphere. The proposed outer heliosheath location of the polarizing grains requires confirmation by modeling grain-propagation through three-dimensional MHD heliosphere models that simultaneously calculate torques on asymmetric dust grains interacting with the heliosphere.