Winds, wind-shears and plasma densities during the initial phase of a magnetic storm from equatorial latitudes

Abstract

Results of a sodium vapour release experiment carried out from SHAR (India), an equatorial rocket launching station, immediately after ( ≤2 h) a storm sudden commencement (SSC) during the initial phase of a magnetic storm, followed by electron density measurements are presented. Many of the relevant atmospheric parameters, namely, neutral winds and their altitude variation, the magnitude of the shears in them, the neutral temperature with altitude by spectroscopic methods, diffusion measurements on the released trail, clues on the turbopause level and the electron densities including the structures (irregularities) in them were obtained. The results of the temperature measurements carried out independently on the sodium trail by means of a ground-based Fabry-Perot spectrometer, operating on the sodium D 1 line, resonantly scattered by the trail have already been reported by us (Ranjan Guptaet al., 1986). In this paper the effects of the excess temperature reported earlier and the rest of the measured parameters on the electron density profiles are evaluated using models and compared with the measurements. The formation of sharp layers of ionization have been explained on the basis of the electro-dynamical processes associated with the wind shears at a location, close to the edge of the equatorial electrojet belt. The significance of the changes in the neutral composition due to the enhanced neutral temperature and the low turbopause level, in increasing the base-level plasma densities by a factor of 3-5 are demonstrated and the possible role of plasma dynamics discussed.