Periodogram analyses of FAC intensity and solar wind coupling. (a) Lomb-Scargle periodograms of the northern hemispheric total (black), dayside (red), and nightside (blue) FAC intensities; T represents total, D is dayside, N is nightside, NH is the northern hemisphere; and 95% confidence levels of the three periodograms are shown by three vertical lines. Cross-wavelet transforms of (b) northern hemispheric total FAC intensity and V_p, and (c) northern hemispheric total FAC intensity and N_CF. Wavelet powers are shown by the color bar at the top. The cone of influence, where edge effects might distort the results, is shown in lighter shades. The relative phase relationships (of FAC intensity with V_p and N_CF) are shown as arrows, horizontal right arrows indicating in-phase, horizontal left arrows indicating anti-phase. For the Lomb-Scargle periodograms, 2-min resolution FAC intensities are used, while for cross-wavelets, all data are processed into 30-min resolution (by taking 30-min running averages) so that they precisely coincide (in time) with each other.