Observations of optical emissions from precipitation of energetic neutral atoms and ions from the ring current

Observations of N2+ 1 N, H Balmer β(HBaβ) and other emissions due to particle precipitation have been observed at two low‐latitude sites (Mt. Haleakala, Hawaii and Cachoeira Paulista, Brazil) and one mid‐latitude site (McDonald Observatory, Southwest Texas). Results are compared for magnetic storms of April 13, 1981 and July 14, 1982. The emissions have the characteristics appropriate to the precipitation into the thermosphere of energetic neutral atoms and/or ions originating in the ring current. These characteristics include high rotational/vibrational excitation of the N2+ 1 N bands and at times the occurrence of HBaβ emission with the same onset time as the N2+ 1 N emission and partial correlation with it afterward. The latitude variation shows a strong increase from low to mid latitudes. The strongest emissions occur in the evening to midnight local time period, and the storm time variations shows strongest emissions during main phases. The time variations of HBaβ and N2+ 1 N emissions indicate that there is more O/O+ precipitation than H/H+ precipitation in the latter part, and sometimes the whole durations of the precipitation events and the variations are consistent with H+ being lost from the inner ring current faster than other species, such as O+ and He+. Lower limits for the energy deposition rates for the strongest emissions at 40–45° dip latitude are 1–2 mWm−2 and for the strongest emissions at 12°S dip latitude, 0.05 mWm−2. Ionization production at its peak altitude somewhere above 110 km would be in the range from 10² cm−3 s−1 to a few times 10³ cm−3 s−1 for the events in Texas, and from 100 to 10² cm−3 s−1 for the stronger events in Hawaii and Brazil.