The Hot Ion Composition, Energy, and Pitch Angle Characteristics Above the Auroral Zone Ionosphere

Abstract

At the time of the previous Nobel Symposium on Space Plasma Physics (Hultqvist and Stenflo, 1975), no ion composition measurements had been made in the auroral acceleration regions although some inferences about the gross characteristics of the ion source regions were possible from observations of precipitating hot 0+ ions (Johnson et al., 1975). The initial, and still the most comprehensive, ion composition measurements in and above the auroral acceleration regions were made with the S3-3 spacecraft at altitudes up to 8000 km from July 1976 to April 1979 (Sharp et al., 1982a). Composition data extending to higher altitudes, at high magnetic latitudes, are now becoming available from the PR0GN0Z-7 spacecraft for the period October, 1978 to June, 1979 (Hultqvist et al., 1979; Lundin et al., 1982a, b) and the Dynamics Explorer (DE) spacecraft launched in August, 1981 (Shelley et al., 1982). The ISEE-1 spacecraft, launched in October, 1977, has recently been providing ion composition data at a few Re in the auroral regions as a result of its gradual increase in orbital inclination (to 55° latitude in June, 1981) (Sharp et al., 1982b). Some ion composition measurements have also been made on rockets, but thusfar, they have been confined to altitudes below the principal auroral acceleration regions (Whalen, 1982).