D. Vokrouhlicky et M. Broz, An improved model of the seasonal Yarkovsky force for regolith-covered asteroid fragments, ASTRON ASTR, 350(3), 1999, pp. 1079-1084
We derive a new analytical solution for the seasonal Yarkovsky effect, the
mean-motion frequency mode of the recoil force due to reradiated sunlight,
on a spherical asteroid fragment. The body is assumed to have a thin low-co
nductivity (regolith-like) surface layer, covering a much more thermally co
nductive core. If the penetration depth of the seasonal thermal wave in the
low-conductivity surface material is larger than the regolith's geometrica
l thickness, the previous simplified solution assuming a homogeneous interi
or of the body might lead to wrong estimates on the intensity of the pertur
bing force. Our approach removes this problem and the results indicate: (i)
an increased seasonal mobility of 10-m sized and larger fragments with an
insulating surface layer, and (ii) a decreased seasonal mobility of meter-s
ized fragments with the same structure. These results may affect the accura
cy of simulations of meteorite and NEA transport to the Earth, as well as t
he dynamical evolution of some real small asteroids (e.g. 1566 Icarus).