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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 36, issue 1
Ann. Geophys., 36, 13-24, 2018
https://doi.org/10.5194/angeo-36-13-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Ann. Geophys., 36, 13-24, 2018
https://doi.org/10.5194/angeo-36-13-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 09 Jan 2018

Regular paper | 09 Jan 2018

New insights for mesospheric OH: multi-quantum vibrational relaxation as a driver for non-local thermodynamic equilibrium

Konstantinos S. Kalogerakis1, Daniel Matsiev1, Philip C. Cosby2,*, James A. Dodd3, Stefano Falcinelli4, Jonas Hedin5,6, Alexander A. Kutepov7,8, Stefan Noll9,10,11, Peter A. Panka8, Constantin Romanescu6, and Jérôme E. Thiebaud6,12 Konstantinos S. Kalogerakis et al.
  • 1Center for Geospace Studies, SRI International, Menlo Park, California, USA
  • 2formerly at: Molecular Physics Laboratory, SRI International, Menlo Park, California, USA
  • 3Air Force Research Laboratory (AFRL), Space Vehicles Directorate, Kirtland Air Force Base, New Mexico, USA
  • 4Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy
  • 5Department of Meteorology (MISU), Stockholm University, Stockholm, Sweden
  • 6formerly at: Physical Sciences Division, SRI International, Menlo Park, California, USA
  • 7The Catholic University of America, Washington DC, USA
  • 8NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 9Institute for Astro- and Particle Physics, University of Innsbruck, Innsbruck, Austria
  • 10Institute of Physics, University of Augsburg, Augsburg, Germany
  • 11German Remote Sensing Data Center (DFD), German Aerospace Center (DLR), Oberpfaffenhofen, Germany
  • 12Aeris Technologies, Redwood City, California, USA
  • *retired

Abstract. The question of whether mesospheric OH(v) rotational population distributions are in equilibrium with the local kinetic temperature has been debated over several decades. Despite several indications for the existence of non-equilibrium effects, the general consensus has been that emissions originating from low rotational levels are thermalized. Sky spectra simultaneously observing several vibrational levels demonstrated reproducible trends in the extracted OH(v) rotational temperatures as a function of vibrational excitation. Laboratory experiments provided information on rotational energy transfer and direct evidence for fast multi-quantum OH(high-v) vibrational relaxation by O atoms. We examine the relationship of the new relaxation pathways with the behavior exhibited by OH(v) rotational population distributions. Rapid OH(high-v)+O multi-quantum vibrational relaxation connects high and low vibrational levels and enhances the hot tail of the OH(low-v) rotational distributions. The effective rotational temperatures of mesospheric OH(v) are found to deviate from local thermodynamic equilibrium for all observed vibrational levels. Dedicated to Tom G. Slanger in celebration of his 5 decades of research in aeronomy.

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The question of whether mesospheric rotational population distributions of vibrationally excited OH are in equilibrium with the local kinetic temperature has been debated over several decades. We examine the relationship of multi-quantum relaxation pathways with the behavior exhibited by OH(v) rotational population distributions and find that the effective rotational temperatures of mesospheric OH(v) deviate from local thermodynamic equilibrium for all observed vibrational levels.
The question of whether mesospheric rotational population distributions of vibrationally excited...
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