Midlatitude ionospheric temperatures during three magnetic storms in 1965

Incoherent (Thomson) scatter observations of F region densities and temperatures were made at Millstone Hill during magnetic storms that occurred in June, August, and September 1965. For the storms of August and September, we have been able to compare the average F region electron and ion temperatures observed in the first 24 hours of the storm with those of the preceding 24 hours. The June measurements, made during the first 48 hours of the storm, have been compared with the average behavior a year earlier and with measurements made on magnetically quiet days in July 1965. In all cases, it is found that there are no changes in electron temperature greater than 30% during the daytime for altitudes below 800 km. Nocturnal increases of electron temperature as large as 100% are sometimes found, but their occurrence is not directly related to the planetary magnetic index Kp. A decrease in NmaxF2 observed during part of one of the magnetic storms does not appear to have been caused by an increase in the loss coefficient resulting from a dependence on electron temperature.