First synoptic observations of geomagnetic storm effects on the global-scale oi 135.6-nm dayglow in the thermosphere by the GOLD mission

The Global-scale Observations of the Limb and Disk (GOLD) mission provides, for the first time, a synoptic view of the thermospheric response to a moderate geomagnetic storm at a 30-min cadence. The observations showed that the OI 135.6-nm emission substantially decreased at middle and high latitudes, but it increased at low latitudes. The depletion pattern between 4 and 6 November 2018 was likely due to the strong upwelling of the high-latitude thermosphere. The deepest depletion in brightness that occurred near local noon was of ~300–400 R (~35% of the quiet time background level) and displayed a striking westward movement. First-principles modeling reasonably reproduced the overall morphology of brightness response to the geomagnetic storm despite the depletion magnitude in brightness being underestimated. The postprocessing of the simulation results revealed that the westward movement of the deepest depletion was attributable to the horizontal wind changes driven by the geomagnetic storm.