Electrodynamic response of the ionosphere to high-speed solar wind streams

A combination of dawn and dusk observations from the DMSP F13 satellite and output from the thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM) are used to study the electrodynamic response of the ionosphere to quasi 9-day recurrent geomagnetic activity driven by solar wind high-speed streams during 2005. Superposed epoch analysis of the zonal and vertical plasma drifts reveal that significant electrodynamic perturbations occur in response to the high-speed streams during 2005. The peak response occurs around 0.5 days after the high-speed stream interface, and the drift perturbations slowly relax back to quiet levels over 4-6 days. The observed and modeled zonal drift perturbations are in good agreement near dusk; however, the amplitude of the zonal drift perturbations at dawn slightly differ. At low-and midlatitudes the modeled drift perturbations are westward at all local times, with the largest westward drifts occurring near midnight. At dawn, the DMSP observations at low-and midlatitudes reveal ∼20 m s^-1 eastward drift perturbations, while the TIE-GCM simulates weaker eastward drifts at midlatitudes and westward drifts in the equatorial region. At dusk, the low-and midlatitude perturbation drifts are ∼10-20 m s^-1 westward in both the DMSP observations and TIE-GCM simulations. Owing to equatorial expansion and strengthening of the high-latitude two-cell convection pattern, the high-latitude zonal drift perturbations are eastward in the morning and westward in the afternoon and evening. Less agreement is present between the simulated and observed vertical drift perturbations. Near dawn, at all latitudes upward drift perturbations are revealed by both the TIE-GCM simulation (∼5 m s ^-1) and DMSP observations (∼10-15 m s^-1). However, at dusk the DMSP observes an upward drift perturbation on the order of 25-35 m s^-1, while the TIE-GCM simulates vertical drift perturbations less than 10 m s^-1. The disagreement may be related to errors in the DMSP observations, or deficiencies in the model. Based on the results presented, we conclude that the disturbance dynamo mechanism is an important mechanism for driving the electrodynamic response at dawn and dusk to recurrent geomagnetic activity driven by solar wind high-speed streams.