Molecular Nitrogen Emissions Research Articles

Calculations of ultraviolet molecular nitrogen emissions from the aurora

Auroral UV molecular nitrogen emission energy calculations based on excitation and ionization cross sections

Absolute photometry of the aurora—II: Molecular nitrogen emission in the sunlit atmosphere

The absolute emission intensity of a sunlit aurora was determined for the 1.N.G. λ3914 band of N 2 + by subtracting the emission intensity originating in the dark atmosphere from the total measured intensity. The method is based on the constancy of the ratio of emission intensity of the oxygen green line O I λ5577 to the λ3914 emission in the dark atmosphere. The ion density of N 2+ is computed as a function of height from the emission rate per unit volume.

Absolute photometry of the aurora—I: The ionized molecular nitrogen emission and the oxygen green line in the dark atmosphere

A low latitude aurora was measured photometrically. Three prominent emission features, λ3914 band of 1.N.G. N 2+, λ5577 of O I and λ6300–6364 of O I, were isolated with narrow pass band filters and recorded continuously throughout the night in the meridian sweep. Absolute calibration was carried out, and corrections for the scattered light and atmospheric extinction were made. The absolute emission intensity for λ3914 and λ5577 is given at a selected zenith distance. The ratio of instantaneous intensities I(O)5577 to I(O)3914 was found to be essentially constant over an intensity range of three powers of ten and to be independent of the type of auroral form. The intensities and correlations obtained are consistent with the following excitation mechanisms. In the dark atmosphere the N 2+ is excited from ionizing collisions of incoming particles with atmospheric N 2. It is concluded that the O I λ5577 line results from secondary electrons, arising from the primary ionization process above, colliding inelastically with oxygen atoms.