Ionospheric Response to a Sudden Stratospheric Warming at High Solar Activity

The recent solar minimum has been an ideal opportunity to study the impact of lower atmosphere dynamics on the thermosphere and ionosphere. During January 2009, for instance, the response to a particularly large sudden stratospheric warming revealed large changes in the vertical plasma drift at the magnetic equator. The response in total electron content showed a 50% increase in the morning hours and a 50% decrease in the afternoon, compared to the typical diurnal variation. Modeling the period enable the physical processes to be unraveled. The change appeared to be in part due to a change in phase of the upward propagating semi-diurnal migrating tide. Numerical simulations have been performed to determine the likely response of the upper atmosphere if this particular stratospheric warming had occurred at higher solar activity. Theory might suggest the wind fields reaching the lower thermosphere dynamo region would be similar, so the changes in the electric fields would be more controlled by the plasma density and conductivity changes. The numerical simulation shed light on the likely response and whether the changes if plasma density would likely be discernable from other sources of solar and geomagnetic variability at high solar activity.