Ionospheric and magnetic observations at 1000 kilometers during the geomagnetic storm and aurora of May 25–26, 1967

Measurements of electron temperature and number density and of transverse magnetic disturbances obtained at 1000 kilometers before, during, and after the magnetic storm and aurora of May 25–26, 1967, are compared with visual observations of the aurora, and a degree of correlation is apparent. Throughout the latitudinal region of visual aurora the electron temperature and its latitudinal variations were much greater than are observed under quiet conditions. Temperatures in excess of 6500°K and temperature variations of greater than 500°K within less than 4 km along the satellite path were measured. Temperatures this high suggest a heat source other than auroral electron bombardment. The electron number density was also extremely structured through the region of visual aurora. Horizontal gradients were observed in which the number density changed by greater than 50% in less than 100 meters along the satellite path. The greatest number density measured was ∼6.5 × 10 4 /cm³ (at Λ = 53°). The magnetometer recorded a number of disturbances (as large as 306γ) in the region of unusual concentration and temperature behavior.