Contribution of intermittent temperature peaks to the generation of the solar wind flow

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 mechanisms 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 (1) the advected perturbations take the form of a mixture of upward propagating shock waves and advected pressure equilibrium structures and (2) 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 1 AU and the observed coronal temperature by taking into account not the average temperature, but the peak coronal temperature, still to be determined.