Behavior of the ionosphere and thermosphere at a southern midlatitude station during magnetic storms in early March 1995

Abstract

During the first six days of March 1995, measurements of the ionospheric electron density were made near Melbourne, Australia, with a digisonde and thermospheric winds, temperatures, and 6300‐Å emission rates were measured with a Fabry‐Perot interferometer. The ionograms were inverted to obtain electron density profiles and peak heights of the F2 layer (hmF2). This paper compares modeled and measured electron densities, airglow emission rates, and neutral temperatures. The measured peak electron density shows strong negative effects from magnetic storms and rapid recovery to normal levels afterward. The model daytime peak density is in good agreement with the measurements on the undisturbed days and also shows negative phases at the appropriate times. However, the model negative effects are not as strong as the measured negative effects. A new algorithm is introduced to bring the measured and modeled peak electron density into better agreement by adjusting the exospheric Tn and atomic oxygen density in the MSIS model. The modified Tn at 300 km altitude agrees reasonably well with both the standard MSIS model and the measured Tn before midnight local time. However, the modified Tn, like the measured Tn, has a tendency to increase after about 2200 LT. At night, adjustments to the MSIS model exospheric temperature and atomic oxygen density are generally small. There is reasonably good agreement between the relative variations of the measured and modeled emission rates. However, there is much more variability in the model intensities than in the measured intensities as a result of rapid movements in the height of the F2 layer.