Impact of solar EUV flux on CO Cameron band and CO2+ UV doublet emissions in the dayglow of Mars

Abstract

This study is aimed at making a calculation about the impact of the two most commonly used solar EUV flux models -- SOLAR2000 (S2K) of \cite{Tobiska04} and EUVAC model of \cite{Richards94} -- on photoelectron fluxes, volume emission rates, ion densities and CO Cameron and CO${}_2^{+}$ UV doublet band dayglow emissions on Mars in three solar activity conditions: minimum, moderate, and maximum. Calculated limb intensities profiles are compared with SPICAM/Mars Express and Mariner observations. Analytical yield spectrum (AYS) approach has been used to calculate photoelectron fluxes in Martian upper atmosphere. Densities of prominent ions and CO molecule in excited triplet a${}^3\Pi$ state are calculated using major ion-neutral reactions. Volume emission rates of CO Cameron and CO${}_2^{+}$ UV doublet bands have been calculated for dif{}ferent observations (Viking condition, Mariner and Mars Express SPICAM observations) on Mars. For the low solar activity condition, dayglow intensities calculated using the S2K model are $\sim$40% higher than those calculated using the EUVAC model. During high solar activity, due to the higher EUV fluxes at wavelengths below 250 Å in the EUVAC model, intensities calculated using EUVAC model are slightly higher ($\sim$20%) than those calculated using S2K model. Irrespective of the solar activity condition, production of Cameron band due to photodissociative excitation of CO${}_2$ is around 50% higher when S2K model is used. Altitude of peak limb brightness of CO Cameron and CO${}_2^{+}$ UV doublet band is found to be independent of solar EUV flux models. Calculated limb intensities of CO Cameron and CO${}_2^{+}$ UV doublet bands are on an average a factor of $\sim$2 and $\sim$1.5, respectively, higher than the SPICAM Mars Express observation, while they are consistent with the Mariner observations.

27 Pages, 12 Figures; Planetary and Space Science, 2011

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• The radiative lifetime of metastable CO ($a^3\Pi ,v=0$)
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• On the Solar EUV Deposition in the Inner Comae of Comets with Large Gas Production Rates
• Model calculation of N2 Vegard-Kaplan band emissions in Martian dayglow
• Calculations of N2 triplet states vibrational populations and band emissions in Venusian dayglow
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Cited by in corpus (4)

• CO Cameron band and CO2+ UV doublet emissions in the dayglow of Venus: Role of CO in the Cameron band production
• Forbidden atomic oxygen emissions in the Martian dayside upper atmosphere
• CO+ first-negative band emission: A tracer for CO in the Martian upper atmosphere
• Model for Nitric oxide and its dayglow emission in the Martian upper atmosphere using NGIMS/MAVEN measured neutral and ion densities