the storm initial phases begin gradually without sudden impulses (SIs). The high-speed solar wind contains large-amplitude (nonlinear) #b/jBj = 1 to 2 Alfve´n waves [Belcher and Davis, 1971; Tsurutani et al., 1994; Balogh et al., 1995]. Negative interplanetary magnetic field Bz components of the Alfve´n waves within high-speed streams lead to continuous auroral zone activity called ‘‘High-Intensity Long-Duration Continuous AE Activity’’ or HILDCAAs that can last for a few to 27 days [Tsurutani and Gonzalez, 1987] (however, it should be noted that most but not all high-speed streams have Alfve´n waves with negative interplanetary magnetic field Bz components).