The variation of O/N2 (reference to N2 column density 1017 cm−2) and nitric oxide radiative emission flux exiting the thermosphere have been studied over the Northern Hemisphere during the superstorm event of 7–12 November 2004. The data have been obtained from Global Ultraviolet Imager (GUVI) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on board the National Aeronautics and Space Administration (NASA)'s Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite. The NO radiative flux is observed to show an anti‐correlation with O/N2 on a global scale. Both NO radiative flux and O/N2 ratio show equatorward motion with maximum penetration in western longitude sectors. A local variation of O, O2, and N2 densities have been calculated using NRLMSISE‐00 model over a midlatitude location (55°N,180°E). On a local scale, model calculated O/O2 and O/N2 ratios are found to follow the observations made by GUVI. The collisional excitation of NO with atomic oxygen is the most dominant process for the total cooling rate. The SABER‐retrieved NO cooling rate (CR) at a local site suggests an enhancement during the storm period with the peak emission rate closely correlated to the progression of the storm. The peak emission altitude of NO CR moves upward during the main phase of the storm. The NO abundance has been calculated by using cooling rate and Nitric Oxide Empirical Model (NOEM) model. Both these suggest a vary large (3–15 times) increase in NO density during the storm, which is required to account the changes in NO radiative flux. A similar kind of enhancement in NO abundance is also noticed in Student Nitric Oxide Explorer observations during intense geomagnetic storms.

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The nitric oxide (NO) radiative emission at 5.3 μm cools the thermosphere by conversion of solar energy into infrared radiation subsequently exiting thermosphere. It correctly serves as a natural thermostat. The NO 5.3-μm emission is even more important during geomagnetic storm events due to huge deposition of heat energy and momentum in the Earth's atmosphere. The Thermosphere, Ionosphere, Mesosphere Energetics, and Dynamics-Sounding of the Atmosphere using Broadband Emission Radiometry observation of NO 5.3-μm radiative emission is studied between ±55 ∘ geographic latitudes during eight geomagnetic storm events. Two events that occurred during 7-12 November 2004 (Dst = −374 nT) and 23-28 August 2005 (Dst = −184 nT) are analyzed in details. The variation of NO emission during other six storms is also presented. The NO volume emission rate (NO VER) shows an enhancement during storm events. The enhanced NO VER illustrates an equatorward movement with descending peak altitude as one moves toward the equator. The NO infrared radiative flux is calculated by integrating NO VER from altitude of 100 to 155 km. A local time hemispheric asymmetry in both NO VER and NO infrared radiative flux is observed during all geomagnetic storm events.

The diurnal variation of height‐distributed nitric oxide (NO) radiative emission during November 2004 superstorm is studied using TIMED‐SABER satellite observations over 55°N–55°S geographic latitude region. The NO volume emission rate (VER), both during day and nighttime, shows an equatorial movement with descending peak emission altitude as one moves toward the equator. The NO VER from altitude of 100 to 280 km is integrated in steps of 30 km above 160 km (and from 100 to 160 km), obtaining the NO infrared radiative flux (IRF). The response of NO IRF depends on the altitude and time of consideration. The NO IRF in the lower altitude (<190 km) shows higher enhancement and a slower recovery as compared to altitude above it. It is observed that NO IRF during day and night responds differently to the November 2004 superstorm. The zonally averaged daytime NO IRF is mainly highest during weaker main phase (10 November, Dst =−263 nT). The maximum zonally averaged nighttime NO IRF is observed during stronger main phase (8 November, Dst =−374 nT) for all altitudes. The maximum relative daytime (RDE) and nighttime enhancement (RNE), which represent the relative variation of NO IRF during storm periods as compared to quiet time value, also exhibit different variations during this storm period. The minimum RDE is observed to show an equatorial movement as one moves downward in altitude. The minimum RDE occurs at about 35°N–40°N for 250–280 km, which decreases toward the equator, and minimum RDE is found near the equator for 100–160 km. The minimum of RNE is observed over the equator for all altitudes.