Venus Night Airglow: Ground-Based Detection of OH, Observations of O2 Emissions, and Photochemical Model

Details Venus Night Airglow: Ground-Based Detection of OH, Observations of O2 Emissions, and Photochemical Model Venus Night Airglow: Ground-Based Detection of OH, Observations of O2 Emissions, and Photochemical Model

Sep 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009dps....41.6301k&link_type=abstract

American Astronomical Society, DPS meeting #41, #63.01

Astronomy and Astrophysics

Astronomy

Scientific paper

Venus nightglow was observed at NASA IRTF using a high-resolution long-slit spectrograph CSHELL on 13/01/2009 and 21/06/2009, when Venus was near its maximum solar elongations and geocentric velocities. The instrument resolution element at resolving power of 4x104 is smaller than the Doppler shift, and careful subtraction of telluric emission and absorption lines can be made. The observations refer to LT=21:30 and 4:00 on Venus, respectively. Both total intensity of the O2 airglow at 1.27 mu and its rotational temperature are extracted from each observed spectrum. The observed O2 nightglow intensity is 0.7 MR at 21:30 and between 25°S and 25°N declining to 0.35 MR at 35°S and 35°N, and the temperature increases from 175±5 K near the equator to 210±5 K at ±35°. We have found a narrow window at 2.94 mu that covers the OH (1-0) P1(4.5) and (2-1) Q1(1.5) airglow lines. The detected line intensities are converted into the band intensities assuming the rotational temperature of 250 K from the VEX OH observations. The OH (1-0) band is 5.5±1.7 kR and 8.8±2.0 kR at LT = 21:30 and 4:00, respectively. The OH (2-1) band is 2.3±0.7 kR at 4:00. These intensities are weaker than those observed by VEX by a factor of 1.4-2. A photochemical model for the nightglow of O2, NO, and OH has been made. The model extends from 80 to 120 km and involves 54 reactions of 21 species with fluxes of O, N, and H at 120 km as input parameters. While the observed OH vibrational distribution is favorable for the nightglow excitation by O+HO2->OH*+O2, the model shows that the rate of H+O3->OH*+O2 is higher by an order of magnitude. The model agrees with the observations for preferential quenching of OH (v=4-9) to v=0-2 in collisions with CO2. This work is supported by PAST.

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