Tentative Identification of Interstellar Dust in the Magnetic Wall of the Heliosphere

Observations of the weak polarization of light from nearby stars, reported byTinbergen (1982), are consistent with polarization by small, radius <0.14microm, interstellar dust grains entrained in the magnetic wall of theheliosphere. The direction of maximum polarization is offset by ~35 deg fromthe heliosphere nose, and extends to low ecliptic latitudes. An offset is foundbetween the direction of the best aligned dust grains, and the upwind directionof the undeflected large interstellar grains seen by Ulysses and Galileo. Inthe aligned-grain region, the strength of polarization anti-correlates withecliptic latitude, indicating that the magnetic wall is predominantly atnegative ecliptic latitudes, which is consistent with predictions of Linde(1998). These data are consistent with an interstellar magnetic field tilt of60 deg with respect to the ecliptic plane, and parallel to the galactic plane.Interstellar dust grains captured in the heliosheath may also introduce a weak,but important, large scale contaminant for the cosmic microwave backgroundsignal with a symmetry consistent with the relative tilts of \Bis and theecliptic.Comment: Submitted to Astrophysical Journal Letter