Geophysical Research Letters: During the storm on November 3 to 4, 2021, the Global-scale Observations of the Limb and Disk (GOLD) mission observed well separated EIA crests post sunset on Nov 3, but merged EIA on Nov 4. We used the Whole Atmosphere Community Climate Model (WACCM-X) to simulate the EIA structures during the two nights. The simulations show two separated post sunset EIA crests on November 3rd but merged post sunset EIA crests on November 4th, which are qualitatively consistent with the GOLD observations. Numerical simulations and Ionospheric Connection Explorer (ICON) neutral wind observations illustrate that the formation of merged EIA crests was due to several hours of downward E × B drifts before and after sunset. Further diagnostic analysis revealed that it was mainly driven by westward electric fields caused by the disturbance dynamo electric field during the recovery phase of the storm.
Nmax observed by GOLD and NmF2 simulated by WACCM-X at 20:10 UT on November 03-04, 2021. The red dotted lines represent the magnetic equator.