Solar wind degradation of interplanetary dust

Abstract

The effect of the solar wind on the disposition of uncharged interplanetary dust particles is considered. The blow-out dimension determined in this fashion is about 10 −3 the dimension which exists for photon radiation pressure alone, and is therefore negligible. The solar wind also removes orbital momentum from the dust by collision, causing the dust to spiral inward. The relative orbital momentum of the wind to the dust is found using experimental data and Barker's Model. At 1 a.u. heliocentric, the outward directed plasma speed is taken to be 5·00 × 10 5 m/sec and the density 5 × 10 6 positive ions/m 3. The solar-wind-induced dust particle lifetime (in years) is then 18 × 10 5 r d ρ d ( R 2( R 2 – 0·00018) where r d and ρ d are dust particle radius and density respectively (MKS), and R is the dust particle's initial heliocentric distance in a.u. This compares favorably with earlier work of Whipple, provided his results are modified to account for the solar wind alpha particle component. Both Whipple's work and this paper are concerned with the extreme case of uncharged dust particles; as such, the times obtained are much greater than those resulting from Öpik's work with charged dust particles. Reality should lie between the two extremes. When the Poynting-Robertson effect and the solar wind are both applied, the dust removal time is changed from T = 7 × 10 5 r d ϵ d ( R 2, for the Poynting-Robertson effect alone, to T = 5 × 10 5 r d ρ d ( R 2).