Effects of the equatorward auroral boundary location and solar wind parameters on Pc5 activity at auroral zone stations: A multiple regression analysis

Abstract

We have conducted a multiple regression analysis of the effect of auroral boundary movement on Pc5 power, the pulsation index, and the product of these two parameters at 17 auroral zone ground magnetometer stations in both hemispheres in March–April 2001, during which time several strong magnetic storms occurred. Solar wind parameters observed by the ACE satellite (velocity, ion density, and Bz) were included as additional independent variables in the regression models to control for their known effects. Auroral boundary data were determined from particle data collected by the DMSP satellites. The fraction of time a station was poleward of the equatorward auroral boundary increased Pc5 power, pulsation index, and the product of the two parameters independent of changes in the solar wind and interplanetary magnetic field. When data were analyzed by storm onset and storm recovery, this association was seen only during storm recovery periods. Individual station analyses showed a reduction in Pc5 power when stations were equatorward of the boundary, but there was no reduction in the Pc5 pulsation index. However, this association between Pc5 activity and auroral boundary movement was not seen in simple graphical presentations; this argues for the value of multifactor analyses in the determination of the drivers of Pc5 activity, rather than the individual study of single factors. A more northward Bz correlated with increased Pc5 power and pulsation index. Solar wind velocity and ion density were both associated with higher Pc5 activity during daylight hours.