Impact of Storm‐Time Enhanced O2Absorption on Disk Viewing N2LBH Spectra: TIMED GUVI Observations

A comparison between storm‐time TIMED/GUVI FUV spectra in thermospheric composition disturbed (O/N2<∼140 km> depleted and NO <∼110 km> enhanced) and undisturbed regions reveals the following features: (1) A clear decrease in N2LBHS (140–150 nm) band intensities compared to that between 150 and 160 nm; (2) A significant spectral decrease around O 164.1 nm; (3) Two enhanced peaks between 170 and 185 nm. The feature (2) is clearly due to atomic oxygen density decrease in the low thermosphere. The feature (3) is caused by storm‐time production and transport of nitric oxide. An AURIC simulation reproduced feature (1) confirming that storm‐time enhancement in O2density (∼120–170 km) and the wavelength dependent O2absorption cross section are the source of observed feature (1). On the other hand, the feature (1) was not observed in the regions without O/N2depletion. This further supports that O2density enhancement is responsible for feature (1). Observations by a FUV spectrograph imager on NASA TIMED satellite revealed two interesting features in the storm‐time disturbed thermosphere: (1) a relative decrease in N2LBH intensities at 140–150 nm versus 150–160 nm, (2) significant decrease in O 164.1 nm radiance and enhanced emission between 170 and 185 nm. The feature (2) is well known and due to O density depletion and production of nitric oxide. The feature is not well understood. A model simulation indicates the feature (1) is due to storm‐time O2density increase and wavelength dependent O2absorption cross section which peaked around 140 nm. This result indicates that FUV spectrograph imager is capable to detect storm‐time O2density changes. (1) FUV spectral difference between storm‐quiet time shows a relative decrease in N2LBH intensities at 140–150 nm versus 150–160 nmThe FUV spectrograph difference between undisturbed regions did not show the above feature(3) Simulations confirm indicate that enhanced O2density and absorption causes the observed FUV spectral differences (1) FUV spectral difference between storm‐quiet time shows a relative decrease in N2LBH intensities at 140–150 nm versus 150–160 nm The FUV spectrograph difference between undisturbed regions did not show the above feature (3) Simulations confirm indicate that enhanced O2density and absorption causes the observed FUV spectral differences