By explicitly taking into account effects of Alfvén waves,
I derive from a simple energetics argument a fundamental relation which
predicts solar wind (SW) speeds in the
vicinity of the earth from physical properties on the sun.
Kojima et al. recently found from their observations
that a ratio of surface magnetic field strength to an expansion factor of
open magnetic flux tubes is a good indicator of the SW speed.
I show by using the derived relation that this nice correlation is an
evidence of the Alfvén wave which accelerates SW in expanding flux tubes.
The observations further require that fluctuation amplitudes of magnetic
field lines at the surface should be almost universal in different coronal
holes, which needs to be tested by future observations.
Authors: Takeru K. Suzuki
Publication Status: ApJL, 640, L75 (astro-ph/0602062)
Last Modified: 2006-03-14 18:47