Filtering of the interstellar dust flow near the heliopause: the importance of secondary electron emission for the grain charging

The deflection of interstellar dust grains in the magnetic field near the heliopause depends on their surface electric charge. We study the electric charging of the grains with emphasis on the secondary electron emission because of its importance in the hot plasma environment near the heliopause. We correct previous models of the secondary electron emission that overestimate the electric charge of dust near the heliopause. Our model calculations of the grain charge, when combined with results from in situ measurements of interstellar dust in the heliosphere, place an upper limit on the magnetic field strength. We find that the detection of interstellar dust with mass of 10−18 kg indicates the component of the magnetic field perpendicular to the interstellar dust flow to be less than 0.4 nT.