  Many chondrules are found to be surrounded by a fine grained rim. Supposedly,
these rims were acquired from dust accreted to the chondrules in a
protoplanetary disk. In numerical simulations we study the heat transfer in
illuminated bare and dust mantled chondrules. The calculations consider the
chondrule size, the dust mantle size, and the thermal conductivities of both
components as parameters. We calculate the photophoretic force and compare the
numerical results to analytical approximations. We give an expression to
quantify the photophoretic force on a spherical particle in the free molecular
regime to better than 2%. We describe the influence of a dust mantle on the
photophoretic strength by an effective thermal conductivity of the core-mantle
particle. The effective thermal conductivity significantly depends on the size
ratio between mantle and chondrule but not on the absolute sizes. It also
strongly depends on the thermal conductivity of the mantle with minor influence
of the thermal conductivity of the chondrule. The size ratio between rim and
chondrule in meteorites is found to vary systematically with overall size by
other authors. Based on this, our calculations show that a photophoretic size
sorting can occur for dust mantled chondrules in optically thin disks or at the
evolving inner edge of the solar nebula.
