Energetic oxygen precipitation as a source of vibrationally excited N₂⁺ in emissions observed at low latitudes

Observations have been made at Mt. Haleakala, Hawaii (dip lat.∼22°N) and Cachoeira Paulista, Brasil (dip lat.∼12°S) of emissions excited by particle precipitation during periods of magnetic activity. The first negative bands of N 2 + were found to have a high degree of vibrational excitation at both sites, and with the absence of emissions attributable to hydrogen and helium, this finding leads to the interpretation that the excitation was due to a flux of precipitating oxygen atoms or ions, more plausibly the former, produced by charge exchange of ring current O + ions with exospheric neutral constituents. More laboratory work is needed to properly interpret the data, but crude estimates of the associated energy deposition and ionization production fall in the range 10 −1 to 10 +1 mWm −2 , and 10 0 ‐10² cm −3 s −1 respectively.