A model for intensity profiles of dust jets near the nucleus of comet Halley
1988; Elsevier BV; Volume: 76; Issue: 1 Linguagem: Inglês
10.1016/0019-1035(88)90140-6
ISSN1090-2643
AutoresW. F. Huebner, D. C. Boice, H. J. Reitsema, W. A. Delamere, Fred L. Whipple,
Tópico(s)Spacecraft and Cryogenic Technologies
ResumoIntensity profiles of jet-like dust features, associated with active regions on the nucleus, have been analyzed in the Halley Multicolour Camera (HMC) images from the Giotto spacecraft. The asymptotic behavior of an intensity profile at large distance from the nucleus (R > 100 km) can be modeled as if arising from a source located at a hypothetical point below the active source region. In this limit, the intensity decreases proportionally to 1R, as expected for free outflow, but reveals a strong flattening relative to an 1z profile near the nucleus, where z is the vertical distance above an extended, dust-producing source region. This flattening can be explained by geometrical effects based on the extended size and nonuniformity of an active region on the surface. A critical height, zc, is introduced to describe the geometrical effects that cause the flattening. This critical height is determined by the vertical distance of the hypothetical point source below the surface, but reflected outward from it. The model is consistent with the observations without invoking other mechanisms.
Referência(s)