The capture of interstellar dust: the Lorentz force case

摘要

The capture of arbitrarily shaped interstellar dust in the Solar System is investigated. Electromagnetic radiation and gravitational forces of the Sun and Lorentz force generated by interplanetary magnetic field are considered. The capture conditions appear to be very sensitive to the particle shape. Non-spherical particles as well as their spherical equivalents are captured only when they are moving initially in the vicinity of ecliptic plane. Capture of non-charged non-spherical dust typically occurs in the region b < 100 R_(Sun), where R_(Sun) is solar radius and impact parameter b is defined as the smallest distance between the particle and the Sun if no forces existed. In contrast, charged particles are typically captured at b > 150 R_(Sun) The total amount of captured non-spherical sub-micron particles differs significantly from the corresponding amount of spherical dust grains. However, both amounts are comparable in the micron-sized range. It is shown that a certain mass of captured non-spherical particles may survive in the Solar System, while captured spherical ones hit the Sun or sublimate in its vicinity. Only a negligible amount of spherical particles can survive. Consideration of solar wind within around of 400 km s~(-1) yields that 20% of the captured non-spherical particles of the effective radius 0.4 μm survive; the corresponding percentage for particles of the radius 0.6 μm is 7%. The total mass of the surviving charged particles is about two orders of magnitude larger than the mass of the surviving non-charged particles. As a result, the sub-micron-sized particles are candidates to contribute to the density increase of the circumsolar dust cloud.