Energy deposition of protons in molecular nitrogen and applications to proton auroral phenomena

TLDR

The study extends a microscopic electron approach based on detailed collisional cross sections to model proton energy deposition in N₂ for auroral research. The method relies on detailed collisional cross sections to calculate proton energy deposition. Excitation efficiencies remain flat from 1 keV to 10 MeV for ionization but drop below 10 keV for excitation and dissociation because of charge exchange; Lyman‑α and Hα photon yields are highly sensitive to low‑energy hydrogen cross sections, exceed earlier estimates, and match Chubb & Hicks for the Lyman‑α/Lyman‑Birge‑Hopfield ratio, with total intensities shown for 4 keV and 1 MeV auroral energies.

Abstract

Motivated by proton auroral studies, we extend the microscopic approach developed for electrons, which is based on detailed collisional cross sections, to deal with the problem of proton energy deposition in N2. Our calculated excitation efficiencies, which include the contributions from charge exchange processes and secondary electrons, remain fairly constant from 1 kev to 10 Mev for the ionization states but vary considerably below 10 kev for excitation states and dissociation processes due to charge exchange effects. The estimates of the Lyman α and Hα photon production are found to be very sensitive to the low-energy hydrogen impact cross section. The Lyman α and Hα photon production tends to be higher than previous estimates of Eather. Good agreement with the results of Chubb and Hicks is obtained for the Lyman α/Lyman-Birge-Hopfield intensity ratio. Total intensities for a typical proton auroral energy of 4 kev and a polar glow aurora of 1 Mev are presented.