Ultraviolet Remote Sensing of Nitric Oxide in the Thermosphere Using the TIMED/GUVI Instrument

Nitric Oxide (NO) plays an important role in both the chemistry and energetics of the upper atmosphere and the ionosphere. It participates in several important chemical reactions that determine trace gas and ion distributions in the lower thermosphere and mesosphere. In addition, it is an important source of cooling, particularly during geomagnetically active times (see for example Mlynczak et al.). The NO concentration in the lower thermosphere is highly variable and depends on energetic inputs into the thermosphere, most notably soft X-rays and energetic particle precipitation (see for example Swaminathan et al.). Thus, any reasonably accurate description of the chemistry and dynamics of the lower thermosphere needs to include a good estimate of the global distribution of NO. The GUVI instrument on the TIMED spacecraft has been systematically acquiring down looking Far Ultraviolet (FUV) spectra since 2008. These data provide global coverage daily in the 120-200nm spectral range. These spectra contain emission from the epsilon bands of NO, which is primarily produced by solar fluorescence during the day (see for example Meier). In this work, we present maps of the epsilon band emission for selected periods of time that demonstrate the morphology of the NO response to solar and geomagnetic activity. References: Mlynczak, M., et al., GRL 30, 21, 2100, doi:10.1029/2003GL017693, 2003. Meier, R.R., SSR 58, 1-185, 1991 Swaminathan, P.K., et al., JGR 103, 11579,1998