Middle‐Low Latitude Neutral Composition and Temperature Responses to the 20 and 21 November 2003 Superstorm From GUVI Dayside Limb Measurements

TIMED/Global Ultraviolet Imager (GUVI) limb measurements of far‐ultraviolet airglow emission have been used to investigate middle‐low latitude thermospheric composition and neutral temperature responses to the 20 and 21 November 2003 (day of year [DOY] 324 and 325) superstorm. Altitude profiles of O, N2 number densities and temperature, as well as O/N2 column density ratio (∑O/N2), on the storm days along the GUVI limb tracks are compared with those on DOY 323 (quiet time). The storm‐time composition and temperature responses were global and evolved continuously as the storm progressed. Specially, N2 and temperature increased almost globally at all altitudes during the storm and their perturbation structures were similar. The magnitudes of their enhancements both increased with altitude and latitude. The storm‐induced O perturbations decreased in the lower thermosphere but increased in the upper thermosphere. Transition heights of O perturbations from decrease to increase changed with latitude and time. During the storm main and recovery phases, the storm‐induced ∑O/N2 decreases were mostly related to the O depletion in the low‐middle thermosphere, whereas ∑O/N2 increases during the storm were primarily caused by N2 depletion. There was a remarkable hemispheric asymmetry in composition responses as they have different morphologies and lifetime, especially during the storm recovery phase. Key Points N2 density and neutral temperature increase almost globally at all altitudes during the storm with similar latitude structures O density decreases in the lower thermosphere but increases in the upper thermosphere in the main and recovery phases of the storm