Incoherent scatter observations at Millstone Hill were made during the importance 3B solar flare which occurred at 15:00 UT on 7 August 1972. Measurements were obtained of the electron density profile over the height range 125 to 1200 km, together with observations of the electron temperature, ion temperature, and vertical drift velociy above 225 km. The Ne(h) results showed electron density enhancements of nearly 100% at 125 km and 60% at 200 km; Ne enhancements were also observed throughout the topside, with the percentage enhancement increasing with height above 400 km. The total electron content up to 1200 km showed an increase of 3.8 × 1016 el m−2 (≃30%).

The temperature and drift data represent the first Thomson scatter measurements of these parameters during flare conditions. While the electron temperature results showed substantial increases at all altitudes examined, the ion temperatures were only slightly perturbed. The drift data provided the most interesting results. In response to the flare, a dramatic upward surge was observed in which the drifts increased nearly linearly with height over the height range 300 to 750 km.

In discussing the overall results obtained during this event, estimates are made of the flare-induced electrodynamic and thermal processes which contribute to the observed effects.