Interstellar magnetic field strength and dirty ice grains oriented by paramagnetic relaxation

A method of estimating the orientation parameter and the resulting galactic magnetic field consistent with the observed visual ratio of polarization to extinction has been given. The orientation has been considered in the sense of paramagnetic relaxation envisaged by Davis and Greenstein (1951) and by Jones and Spitzer (1967). It is assumed that the grains, cylindrical in shape, consist of a pair of distinct effective sizes with different number densities. The method has been applied to dirty ice grain as an illustration.