O/N₂ changes during 1–4 October 2002 storms: IMAGE SI‐13 and TIMED/GUVI observations

Abstract

Thermospheric O/N 2 column density ratios referenced at a N 2 column density of 10 17 cm −2 are obtained using the IMAGE SI‐13 and TIMED/GUVI far‐ultraviolet (FUV) dayglow data, AURIC simulation results, and MSIS86 model. Each of the magnetic storms occurring during a 4‐day period (1–4 October 2002) caused significant O/N 2 depletion that was detected by both of the IMAGE SI‐13 and GUVI instruments. The depletion extended down to latitudes of 10° and −5° in the Northern and Southern Hemispheres, respectively. Simultaneous measurements show an excellent agreement between the SI‐13 and GUVI O/N 2 on both global and local scales. The IMAGE SI‐13 O/N 2 data provide direct optical evidence that the O/N 2 depletion corotates with the Earth. The GUVI O/N 2 indicate the depletion in both of the hemispheres is not symmetric owing to the seasonal effect and differences in heating and convection induced winds. Both the IMAGE SI‐13 and GUVI O/N 2 maps also provide a good opportunity for future modeling efforts.