Some initial ISEE-1 results on the ring current composition and dynamics during the magnetics storm of December 11, 1977

On December 11, 1977 the ISEE-1 spacecraft traversed the equatorial magnetosphere in the prenoon and dawn sectors during the early recovery phase of a magnetic storm with peak DST of -125 gamma. Along the dayside leg O(+) was comparable to or exceeded H(+) in number density in the energy range 0.1-17 keV. The velocity distribution of O(+) showed a characteristic dispersion, consistent with the ions being transported to the dayside from the dusk to midnight sector. The high-energy slope of the H(+) and O(+) distribution functions showed different radial dependence, with the slope of H(+) being consistent with a harder component carrying most of the energy density.