Fig. 4.

(a) High-pass filtered geomagnetic variations at high latitude stations GDH, IQA, CDR, CHB and at HUA in the dip equator during 10–14 h on February 9. (b) Power spectral densities (PSDs) on the ground and plasma flows and magnetic variations observed by GTL after the transient stay in the magnetosheath. Total PSDs at five stations, IQA, GDH, CDR, CHB and BLC, in cusp latitudes are plotted in the bottom panel. The label R, indicated with station codes, represents the polarization mode at major spectral peaks. (c) Plots of solar wind and IMF observed by the ACE spacecraft (time shifted by 72 min) along with AL/PC indices. Three lines show PC indices derived from geomagnetic variations at IQA, ALE and DRV.