Intensities of the Martian N2 electron-impact excited dayglow emissions

• Published in: Geophysical research letters 2013-06, Vol.40 (11), p.2529-2533
• Main Authors: Fox, Jane L., F. Hać, Nicholas E.
• Format: Article
• Language: English
• Subjects: Emissions; Mars; Mars dayglow; Mars thermosphere models; martian airglow; nitrogen emissions; Spacecraft
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/grl.50435

The first N2 emissions in the Martian dayglow were detected by the SPICAM UV spectrograph on board the Mars Express spacecraft. Intensities of the (0,5) and (0,6) Vegard‐Kaplan bands were found to be about one third of those predicted more than 35 years ago. The Vegard‐Kaplan band system arises from the transition from the lowest N2 triplet state (A3Σu+;v′) to the electronic ground state (X1Σg+;v″). It is excited in the Martian dayglow by direct electron‐impact excitation of the ground N2(X) state to the A state and by excitation to higher triplet states that populate the A state by cascading. Using revised data, we compute here updated intensities of several of the bands in the N2 triplet systems and those involving the a1Πg state, the upper state of the Lyman‐Birge‐Hopfield bands. We find that the predicted limb intensities for the (0,5) and (0,6) Vegard‐Kaplan bands are consistent with the measured values. Key Points We have computed the intensities of 15 band systems of N2 on Mars The intensities of the VK emissions agree with SPICAM limb profiles Our calculations do not require that the mixing ratio of N2 be reduced