Anomalous Doppler Shift in the Storm-time Midlatitude Red-line Emission

Monday, 15 December 2014
Brian Joseph Harding1, Jonathan J Makela1, Gary Bust2, John W Meriwether3, Rafael Mesquita3, Sam Sanders3, Aaron J Ridley4, Michael Castelaz5, Marco Ciocca6, Gregory Duane Earle7 and Nathaniel A Frissell7, (1)University of Illinois, Urbana, IL, United States, (2)John Hopkins University-Applied Physics Laboratory, Laurel, MD, United States, (3)Clemson University, Clemson, SC, United States, (4)Univ Michigan, Ann Arbor, MI, United States, (5)Pisgah Astronomical Research Institute, Rosman, NC, United States, (6)Eastern Kentucky University, Richmond, KY, United States, (7)Virginia Polytechnic Institute and State University, Blacksburg, VA, United States
Recent observations from a midlatitude network of ground-based Fabry-Perot interferometers (FPIs) have revealed an anomalous blueshift in the spectrum of the red-line 630.0-nm airglow emission looking to the zenith during the geomagnetic storm of 02 Oct 2013 [Makela et al., 2014]. Although the red-line emission is historically interpreted as an indicator of the thermospheric neutral wind at an altitude of 250 km, Makela et al. [2014] argue that the apparent sustained downward winds of 150 m/s are not physical and suggest that during a storm, the emission is contaminated by fast oxygen atoms created by charge exchange with precipitating oxygen ions. We extend this analysis to include every storm with adequate data quality in our FPI database and find that this anomalous blueshift is a persistent effect at midlatitudes. This complicates the interpretation of red-line data collected by FPIs during storm periods. We compare with the ionospheric response to these storms as estimated by an assmiliative model, IDA4D, in order to investigate the possible sources of contamination.

J. J. Makela, B. J. Harding, J. W. Meriwether, R. Mesquita, S. Sanders, A. J. Ridley, M. W. Castellez, M. Ciocca, G. D. Earle, N. A. Frissell, D. L. Hampton, A. J. Gerrard, J. Noto, and C. R. Martinis, “Storm time response of the mid-latitude thermosphere: Observations from a network of Fabry-Perot interferometers,” J. Geophys. Res. Sp. Phys., Jul. 2014. doi: 10.1002/2014JA019832