MAGNETICALLY ENHANCED COAGULATION OF VERY SMALL IRON GRAINS - A CORRECTION OF THE ENHANCEMENT FACTOR DUE TO DIPOLE-DIPOLE INTERACTIONS

We correct an earlier effort to calculate the magnetically enhanced, c oagulation cross section for very small iron grains in the solar nebul a. None of the equations derived is completely satisfactory and severa l problems with regard to the initial assumptions in the derivation ar e discussed. Our most conservative estimates for the enhancement in th e coagulation cross section due to magnetic effects are factors of 10( 3) to 10(4), while more realistic values range from 10(5) to 10(7) or higher. We therefore conclude that magnetic dipole-dipole interactions could play a significant role in the initial stages of plantesimal ac cretion in protosellar nebulae. (C) 1995 Academic Press, Inc.