Electron content and topside plasma temperature studies at low latitudes during a period from sunspot minimum to sunspot maximum

Abstract

Total electron content results are presented for the period September 1963-August 1968 for Hong Kong (latitude 22.2°N, dip 30°). Diurnal, seasonal and long term solar variations of content have been determined. The 'winter anomaly' only becomes apparent as the solar cycle advances to a maximum. The peak content increased by a factor 2 and the minimum content by a factor 4 as the sunspot number increased from 5 to 120. Using bottomside ionogram information corresponding variations have been obtained of total equivalent and bottomside thickness, the average topside plasma temperature and the ratio of top to bottomside contents. From sunspot minimum to maximum no definite increase was observed of either the total equivalent thickness or plasma temperature. There was an apparent drop of 30 per cent in the ratio of top to bottomside content over the same period. The integrated production rate showed a definite solar activity dependence while the effective loss rate did not. A seasonal reversal of the effective loss rate was observed. Near sunspot minimum the loss rate was a maximum in winter while near sunspot maximum the maximum loss rate occurred in summer. © 1971.