Particle simulation of supersonic convection in the protostellar nebula

Abstract

For the simulation of compressible convection and a possible description of inner processes in meteorites a new algorithm for particle-in-cell methods in particle simulation is developed, which allows a direct description of the inner pressure by use of individual particle temperatures and therefore a description of gas dynamics without the approximations of perturbation theory. The simulation of nonadiabatic processes in superadiabatic stratified atmospheres leads to the self-organization of convection cells and to supersonic convection and instationary shock front systems for high Rayleigh numbers Ra > 5 × 10 5 as they are received by other numerical methods. The transport of material through shock fronts yields much faster temperature and pressure changes than ordinary convective transport in the subsonic range. Tracing the values of state along the pathlines shows that fast entropy increases occur either within shock fronts or due to local dissipation in turbulences. Transport through shock front systems results in multiple rapid temperature changes per cycle. Investigations on the local convective structure of the protostellar nebula with a simple radiative transfer and standard opacities and accretion rates indicate supersonic convection and multiple shock front systems in the outer layers of the solar nebula due to radiative cooling. Supersonic convection provides a very effective mechanism of dissipation for the protostellar nebula and makes a contribution to the discussion on the turbulent structure of the protostellar nebula and to the formation of chrondrules.