Electron temperature variations at the F2 layer peak height during the space weather month of September 1999 Original Research Article

Data from 23 ionospheric stations are used for September 1999 to produce the electron temperature, Te, at the F2 layer peak height, hmF2, on the base of empirical relation between Te and the electron density, Ne, at a given height for a given index of solar radio flux (Brace and Theis, 1978, 1984). Daily and monthly Te minimum, mean, and maximum are then evaluated for each station. Near the solar maximum monthly Te(min) is about 1470°K while the monthly Te(max), occurring during sunrise, varies with location in a wide range from 1900 to 3900°K. A new weighted scheme is suggested for forecast of magnetic activity 3 h in advance by accumulation of selected magnetic indices ranked by decreasing order for 12 hrs preceding given time of observation. By using the daily Te values, cold and hot ionospheric days during the month have been defined: the magnetic activity does not influence Te at low and equatorial latitudes while at mid-latitudes a high degree of correlation is found between the F2 peak plasma heating and weighted accumulation of the magnetic indices. The most important effect of Te heating at sunrise is observed at high latitudes during the recovery phase of magnetic storm and sub-storm.