Formation of chondrules in radiative shock waves

Abstract

The formation of chondrules in the protoplanetary nebulae causes many questions concerning the formation process, the source of energy for melting the rims, and the composition of the origin material. The aim of this work is to explore the heating of the chondrule in a single precursor as is typical for radiation hydrodynamical shock waves. We take into account the gas-particle friction for the duration of the shock transition and calculate the heat conduction into the chondrules. These processes are located in the protoplanetary nebulae at a region around 2.5 AU, which is considered to be the most likely place of chondrule formation. The present models are a first step towards computing radiative shock waves occurring in a particle-rich environment. We calculated the shock waves using one-dimensional, time-independent equations of radiation hydrodynamics involving realistic gas and dust opacities and gas-particle friction. The evolution of spherical chondrules was followed by solving the heat conduction equation on an adaptive grid. The results for the shock-heating event are consistent with the cosmochemical constraints of chondrule properties. The calculations yield a relative narrow range for density or temperature to meet the requested heating rates of $R > 10^4\,K\, h^{-1}$ as extracted from cosmochemical constraints. Molecular gas, opacities with dust, and a protoplanetary nebula with accretion are necessary requirements for a fast heating process. The thermal structure in the far post-shock region is not fully consistent with experimental constraints on chondrule formation since the models do not include additional molecular cooling processes.