How Does Thermospheric Temperature and Composition Recovery Differ After
a Strong Geomagnetic Storm?
Abstract
The recovery of the thermosphere after a strong geomagnetic storm on 12
May 2021 is investigated using lower and middle thermospheric
temperature (Tdisk), ratio of atomic oxygen and molecular nitrogen
column densities (O/N2), cooling due to Nitric Oxide (NO), and model
simulations. The peak influence of the geomagnetic storm lasted about
five hours and generated latitudinal gradients in Tdisk and O/N2.
Following the storm, the latitudinal gradient in temperature recovered
faster compared to that of O/N2. Measured NO-cooling rate and simulated
NO-densities are enhanced on the storm day compared to a quiet-day,
consistent with a rapid recovery in temperatures. Based on this, we
conclude that the faster recovery of the Tdisk latitudinal gradient is
driven by the combined effect of NO cooling and strong thermal
conductivity. Furthermore, the slower recovery of the O/N2 latitudinal
gradients can be attributed to the lack of poleward advection after the
storm.