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S.R. Habbal (SAO), R. Woo (JPL), X. Li (SAO)
The solar wind mass flux, inferred from in situ measurements of the density and flow speed, is one of the conserved quantities that provides an inevitable constraint for solar wind models. In situ measurements have consistently shown that the mass flux in the fast solar wind does not vary by more than a factor of two. Typical values range from 1.5 \times 108~\rm cm-3 to 3~108~\rm cm-3 for wind speeds at or above 700 km/s. While the density measured in situ can vary by approximately a factor of two, the flow speed does not vary by more than 10 to 20% in the fast streams. We show in this paper that the variations in the mass flux in the fast solar wind are directly related to changes in the density at the Sun. This finding provides further support for the view recently proposed by Woo and Habbal that the coronal density extends almost radially outwards from the Sun, that this extension is reflected in in situ measurements, and that the quiet Sun is also a source of the fast solar wind in addition to coronal holes.
This work is supported in part by NASA grant NAG5-6215 to the Smithsonian Astrophysical Observatory.
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