Incoherent scatter radar observations of the auroral zone ionosphere during the total solar eclipse of July 10, 1972

Observations of the behavior of the auroral zone ionosphere were made with the incoherent scatter radar at Chatanika, Alaska, during the total solar eclipse of July 10, 1972. The radar beam intersected the approximate center of the eclipse shadow at a height of 400 km. The electron temperature decreased by more than 1200°K, and the ion temperature decreased by approximately 100°K near eclipse totality. Electron concentrations in the E and lower F regions decreased by 50%. Concentrations above the F layer peak decreased slightly, but there was no net change in ionization at the F layer maximum. Apparently, downward diffusion of upper F region ionization was just adequate to balance the loss processes at the layer maximum. An estimate of the heat input to the electron gas at 340 km showed that this quantity fell to about 25% of its background value during totality. Control radar data for the eclipse observations were obtained on July 9, 11, and 12, 1972, along with supporting vertical incidence ionosonde and magnetometer data acquired near College, Alaska.