Constraints on high-speed solar wind structure near its coronal base: a ULYSSES perspective.

Abstract

Ulysses plasma data at high heliographic latitudes were studied to develop constraints on the structure of the corona at the base of the high-speed solar wind. Salient features of the flow poleward of +/-60° revealed: 1) low variances of all bulk flow parameters, 2) parameter values that agree with those measured during high-speed conditions in the ecliptic plane when all are scaled to 1AU, 3) the continuous presence of two interpenetrating proton streams that are not resolved in velocity space, 4) a single alpha-particle beam that travels at a speed that is close to the local Alfven speed faster than the primary proton beam, 5) a proton temperature that is a factor of 2.4 times that of the electrons, and 6) a constant helium abundance that averages 4.4%, about half that inferred from helioseismic data in the solar convection zone. These data are combined with a host of other remote-sensing solar data and solar wind data to develop support for a model of a well-mixed solar atmosphere that is driven by reconnection-generated plasma-jet transients. In this model, acceleration of the solar wind to its terminal speed is complete within a heliocentric distance of about 5R_s_.