Pi2 pulsations associated with poleward boundary intensifications during the absence of substorms

Abstract

Pi2 pulsations during the intervals of extremely quiet geomagnetic conditions (Kp = 0) have been reported by Sutcliffe and Lyons [2002]. These authors observed that several Pi2 bursts occurred simultaneously at high (magnetic latitude = 71°) and low (42°) latitudes during the absence of magnetospheric substorms and found that the bursts are strongly correlated with poleward boundary intensifications (PBIs). The authors discussed the correlation between the PBI‐associated Pi2 (PBI‐Pi2) bursts and enhancements of energetic particle fluxes in the plasma sheet, but they did not focus on the wave properties of the PBI‐Pi2 pulsations. In this study we examine whether the PBI‐Pi2 pulsations at middle/low latitudes exhibit spatial variations similar to substorm‐associated Pi2 pulsations. Using ground‐based data from latitudinally and longitudinally extended magnetometer network and spacecraft data in the duskside, we investigate the spatial variation of the frequency, amplitude, phase, and interstation coherence of the PBI‐Pi2 events. We show that the PBI‐Pi2 pulsations in this study have different features at different local times and suggest that their period and duration are determined at a source region, where fast earthward flows brake.