Global dayside ionospheric response to interplanetary electric fields: Plasma uplift and increases in total electron content

The interplanetary shock/electric field event of 5-6 November 2001 is analyzed using ACE interplanetary data. The consequential ionospheric effects are studied using GPS receiver data from the CHAMP satellite and data from similar to 100 ground-based GPS receivers. The dawn-to-dusk interplanetary electric field was initially similar to 33 mV/m just after a forward shock (IMF B-Z = -48 nT), reaching a peak value of similar to 54 mV/m one hour and 40 minutes later (B-Z = -78 nT). The electric field was similar to 45 mV/m (B-Z = -65 nT) two hours after the shock and a magnetic storm intensity of D-ST = -275 nT was reached. The dayside satellite GPS receiver data plus ground-based GPS data indicate that the entire equatorial and midlatitude (up to +/- 50 degrees MLAT) dayside ionosphere was uplifted, significantly increasing the column-integrated electron content at altitudes above the CHAMP orbital altitude of 430 kin. Based on the total electron content (TEC), this uplift appeared to peak similar to 2 1/2 hours after the shock passage. The effect of the uplift leading to TEC increase lasted for 4 to 5 hours. We suggest that the interplanetary electric field "promptly penetrated" to the ionosphere, and the dayside plasma was convected (by E x B drift) to higher altitudes. Upward plasma transport led to a similar to 55-60% increase in equatorial ionospheric TEC measured from altitudes of similar to 430 km (at 1930 LT). This inferred vertical transport plus photoionization of atmospheric neutrals at lower altitudes caused a 21% TEC increase in equatorial ionospheric TEC at similar to 14 LT (from ground based measurements). Data from an equatorial magnetometer confirms the electric field behavior inferred from the TEC changes on the dayside. Seven to nine hours after the beginning of the electric field event, the dayside ionospheric TEC above similar to 430 kin decreased to values approximately 45% lower than quiet day values. The ground-based equatorial ionospheric TEC decrease was similar to 16%. This decrease occurred both at midlatitudes and at the equator. We presume that thermospheric winds and neutral composition changes produced by the storm-time frictional heating and disturbance dynamo electric fields are responsible for these decreases.