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Recently the Cassini Ultraviolet Imaging Spectrograph has revealed thepresence of N2 Vegard-Kaplan band emissions in Titan's dayglow limbobservation. We present model calculations for the production of various N2triplet states in the upper atmosphere of Titan. The Analytical Yield Spectratechnique is used to calculate steady state photoelectron fluxes in Titan'satmosphere, which are in agreement with those observed by the Cassini's CAPSinstrument. Considering direct electron impact excitation, inter-statecascading, and quenching effects, the population of different levels of N2triplet states are calculated under statistical equilibrium. Densities of allvibrational levels of each triplet state and volume production rates forvarious triplet states are calculated in the model. Vertically integratedoverhead intensities for the same date and lighting conditions as the reportedby UVIS observations for N2 VK, 1P, 2P, Wu-Benesch, and Reverse First Positivebands of N2 are found to be 132, 114, 19, 22, and 22 R, respectively. Overheadintensities are calculated for each vibrational transition of all the tripletband emissions of N2, which span a wider spectrum of wavelengths fromultraviolet to infrared. The calculated limb intensities of total and prominenttransitions of VK band are presented. The model limb intensity of VK emissionwithin the 150-190 nm wavelength region is in good agreement with the CassiniUVIS observed limb profile. An assessment of the impact of solar EUV flux onthe N2 triplet band emission intensity has been made by using three differentsolar flux models, viz., Solar EUV Experiment, SOLAR2000 model of Tobiska(2004), and HEUVAC model of Richards et al, (2006). The calculated N2 VK bandintensity at the peak of limb intensity due to S2K and HEUVAC solar flux modelsis a factor of 1.2 and 0.9, respectively, of that obtained using SEE solar EUVflux.

Production of N2 Vegard-Kaplan and other triplet band emissions in the dayglow of Titan