Interplanetary gas. XVII. an astrometric determination of solar wind velocities from orientations of ionic comet tails

A statistical analysis of ionic comet-tail position angles on the sky using no weights and no assumptions of coplanarity yields a model of the solar wind with mean properties of a radial bulk velocity w = 415 km s -1, azimuthal bulk velocity w = 6 km s - , polar bulk velocity w8 = 0 km s - 1, and an isotropic, peculiar velocity of about 40 km s - . These results and particularly the value for w are in accord with recent spacecraft results. Thus, the solar wind slows the solar rotation with an e-folding time comparable to the age of the Sun.