A theory of dust comets. I. Model and equations
Abstract
A theory based on kinetic and fluid-dynamic concepts is formulated for the head and tail regions of dust comets. Dust particles having a wide distribution of sizes are assumed to be released from the comet nucleus in an essentially continuous manner in time during the period of distinctive cometary phenomena. The dust particles are accelerated radially outward from the nucleus by drag forces due to the expanding gas in the comet head. This interaction is found to occur only in a small inner head region, where gas densities are high and where the gas may be described as a continuum. In the tail region, the oniy significant forces assumed to act on the dust particles are solar gravity and pressure of solar radiation. The motion of the dust particles in dust tails is treated as a hypersonic, col- lision-free flow. Relatively simple expressions are derived for the surface density in such tails By com- parison of calculated distributions of surface density with measured distributions of light intensity, it is possible to determine the dust and head-gas emission rates as functions of time, the distribution of dust- particle sizes, and the emission velocity from the inner head region as a function of particle size and time. The theory is also capable of explaining observed non-radial dust-tail orientations
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1968
- DOI:
- 10.1086/149761
- Bibcode:
- 1968ApJ...154..327F