Contribution of intermittent temperature peaks to the generation of the
solar wind flow
J. Geophys. Res., 104, 17033, 1999
R. Grappin, A. Mangeney, S.J. Schwartz, W.C. Feldman
Abstract
Observations of frequent, intermittent, density, velocity and
temperature variations, called jets, in the solar corona have led some
authors to propose these jets as possible acceleration mechanims for
the fast solar wind seen
at large distances. In the search of possible dynamical
effects, we look here at the implications of intermittent temperature
fluctuations at the coronal level on the subsonic and supersonic solar wind
properties, in a spherically symmetric (single fluid) wind with
polytropic index close to unity, and no magnetic field.
Sudden temperature pulses are applied periodically at the
coronal level, with no pressure variation, the velocity being free. One
finds that a) the advected perturbations take the form of a mixture of
upward propagating shock waves and advected pressure equilibrium
structures b) the mean temperature increases due to the larger
expansion rate of the fluid with peak temperature. As a result, a main
part of the wind flow at large distance appears to be generated by
intermittent coronal events with peak temperature. We propose thus to
reduce the discrepancy between the fast wind speed observed at one
AU and the observed coronal temperature by taking into account not
the average temperature, but the peak coronal temperature, still to be
determined.