ON HYPERVELOCITY IMPACT PHENOMENA OF MICRODUST AND NANO X-RAY FLARES IN COMETARY COMAE

Dust measurements on the Vega and Giotto probes to Comet Halley have s hown that dust particles of very small sizes (10-100 A) might be very abundant in cometary comas. A scenario of self-generation of such popu lation of very small grains (VSGs) via collisional interaction with th e cometary dust coma is considered here. If the VSGs can be charged to an electrostatic potential of greater than or similar to 10 V, they w ould be effectively trapped by electromagnetic interaction with the co metary plasma and the collisional erosion of the cometary dust coma wo uld be facilitated. In the case that a small fraction of the impact ki netic energy can be converted to soft X-ray emission, the resultant X- ray luminosity might reach 5-10% of the value observed by ROSAT thus p roviding a second component of the source mechanism. (C) 1997 Academic Press.