Thermospheric temperature and density variability during 3-4 February 2022 minor geomagnetic storm

Themospheric conditions during a minor geomagnetic event of 3 and 4 February 2022 has been investigated using disk temperature (T-disk) observations from Global-scale Observations of the Limb and Disk (GOLD) mission and model simulations. GOLD observed that the T-disk increases by more than 60 K during the storm event when compared with pre-storm quiet days. A comparison of the T-disk with effective temperatures (T-eff, i.e., a weighted average based on airglow emission layer) from Mass Spectrometer Incoherent Scatter radar version 2 (MSIS2) and Multiscale Atmosphere-Geospace Environment (MAGE) models shows that MAGE outperforms MSIS2 during this particular event. MAGE underestimates the T-eff by about 2%, whereas MSIS2 underestimates it by 7%. As temperature enhancements lead to an expansion of the thermosphere and resulting density changes, the value of the temperature enhancement observed by GOLD can be utilized to find a GOLD equivalent MSIS2 (GOLD-MSIS) simulation-from a set of MSIS2 runs obtained by varying geomagnetic ap index values. From the MSIS-GOLD run we found that the thermospheric density enhancement varies with altitude from 15% (at 150) to 80% (at 500 km). Independent simulations from the MAGE model also show a comparable enhancement in neutral density. These results suggest that even a modest storm could impact the thermospheric densities significantly and GOLD data can be used to improve the empirical and assimilative models of the thermosphere.