INSTABILITIES OF PROTOSTELLAR CORES - THE INFLUENCE OF ADAPTIVE GRIDSON INSTABILITIES OF 1ST PROTOSTELLAR CORES

It is shown that the destructive instabilities of first protostellar c ores as described by Balluch (1991c) are numerical artefacts. The inst abilities are caused by the implicit adaptive grid causing strong grid motion inside the core to resolve dust destruction fronts and thereby introducing advection errors. Test calculations using the numerical m ethod of Balluch were carried out with simplified constitutive relatio ns which avoid the kappa-mechanism that was made responsible for the i nstabilities. In these test calculations the grid motion is introduced artificially to demonstrate its influence. Thereby it was possible to reproduce the core explosions. It is also shown that using realistic material functions the destructive instabilities vanish if the opacity is removed from the grid equation. But luminosity variations upstream from the shock as predicted by the linear stability analysis by Ballu ch (1991b) are still present.