Interplanetary Gas. XIV. on the Extent of Effective Corotation

The super-Alfvenic point or distance of effective corotation for the loss of angular momentum in the solar wind plasma is found by extrapolating observed plasma densities and velocities, and magnetic fields back toward the Sun. The result is approximately 20-40 Ro for quiet conditions, and possibly a larger value for disturbed conditions. This value is somewhat larger than the usual estimates made by extrapolating the solar surface field outward The theoretical treatment of Weber and Davis permits an estimate of the angular momentum carried by the plasma, and these estimates are consistent with the values of the tangential velocity of the solar-wind plasma at Earth inferred by Brandt from studies of Type I comet tails. Such effective corotation distances change the interpretation of Sun-Earth delay times, complicate the search for the solar M-regions, and imply an e-folding time for braking of solar rotation comparable to the age of the Sun.