Polarization characteristics of Pi 2 pulsations and implications for their source mechanisms: Location of source regions with respect to the auroral electrojets

Substorm onsets and intensifications are accompanied on a one-to-one basis by a Pi 2 magnetic pulsation burst. The source region for these pulsations is generally thought to lie in the region of substorm disturbance in the auroral oval. In this paper we outline the characteristics of Pi 2 pulsations in regions near the substorm enhanced electrojet but removed from the locale of the westward travelling surge. We show that a resonance region for the pulsations lies at the equatorwad edge of the westward electrojet, which in the evening sector marks the locus of the Harang discontinuity. Finally we show examples where the maximum amplitude of the Pi 2 is located at or equatorward of the southern border of the eastward electrojet or at the southern border of the westward electrojet. This is clear evidence for the coupling of wave energy into the L-shells far distant from the source of the energy. Mechanisms for Pi 2 generation are discussed in the context of the results presented in this paper.