Magneto-rotation experiments of micron-sized particles dispersed in a diffused gas medium oriented to reproduce the dust alignment in the interstellar region

Abstract

The magneto-rotations were detected for graphite single-crystal grains dispersed in the diffused gas media for the first time in the pressure range between 300 Pa to 10 5 Pa at a temperature, T = 293 K. Full alignment wasachieved at a field intensity of 14 mT for the graphite crystal of 3 x 10 - 1 2 grms in weight at 300 Pa. The results were consistent with the Langevin theory, in which the balance between field-induced anisotropy energy and the thermal agitation energy were assumed to drive the process. The achieved experimental procedure provides a technical basis to reproduce the magnetic alignment in the diffused and low temperature condition of the star-formation region, considering that the contemporary experiments on magneto-rotation are performed on particles suspended in the liquid media. The experiments at low temperatures below 160 K can be performed only in the gas medium. The field intensity to achieve magnetic alignment is expected to be considerably small at molecular cloud temperature, due to the decrease of thermal agitation energy and due to the temperature dependence of the paramagnetic anisotropy following the Curie-Weiss law.