Geomagnetic and auroral activity driven by corotating interaction regions during the declining phase of Solar Cycle 23

(3) The enhancement of the auroral power and Kp with increasing solar wind speed followed the same pattern, for both dominantly southward and northward Bz conditions, regardless of the behavior of solar wind density and dynamic pressure. These results suggest that, during CIR events, southward Bz played the most critical role in determining geomagnetic and auroral activity, whereas solar wind speed was the next most important contributor.

The solar wind dynamic pressure was the less important factor, as compared with Bz and solar wind speed. Relatively strong auroral precipitation energy flux (> ~3 mW/m2) occurred in a wider auroral oval region after the stream interface than before it for both dominantly northward and southward Bz conditions. These conditions enhanced the auroral hemispheric power after the stream interface.

Intense auroral precipitation (> ~4 mW/m2) generally occurred widely at night under dominantly southward Bz conditions, but the location of this precipitation in the auroral oval was different when it was associated with different solar wind density and speed conditions.