Interstellar Dust at the Magnetic Wall of the Heliosphere. II

Abstract

Several sets of data show that small interstellar grains captured in interstellar magnetic fields draped over the heliosphere appear to polarize the light of nearby stars. The maximum polarization direction is offset in ecliptic longitude by about +35 from the upwind direction, and the polarization peak is enhanced for stars near the ecliptic plane. A band of weak polarization stretches through the southern ecliptic hemisphere to the downwind direction. The interstellar field at the heliosphere is directed towards l=105 deg, forming an angle of about 75 deg. with the inflowing gas. Grain alignment is stable in the low density LIC, and is disrupted about 600 times more slowly than in dense clouds. The polarization vanishes where the outer heliosheath magnetic fields become tangled or reconnect. The dust in the local cloud appears to be primarily olivines. The distribution of polarization depends on the solar cycle phase.