Correspondence between the ULF wave power spatial distribution and auroral oval boundaries

Abstract

The location of the auroral oval boundaries has been mapped onto the Pc5 wave power spatial distribution. The poleward and equatorward boundaries of auroral oval are estimated using either the BAS database based on UV observations of the aurora by the IMAGE satellite or the OVATION model based on the DMSP particle data. The epicenter of the spectral power of broadband fluctuations in the Pc5 band during storm growth phase is mapped inside the auroral oval. During the storm recovery phase, the spectral power of narrowband Pc5 waves, both in the morning and dusk sector, is mapped inside the auroral oval or around its equatorward boundary. This observational result confirms the effects earlier reported: the spatial/temporal variations of the Pc5 wave power in the morning/pre-noon sector are closely related to the location of the auroral electrojet and magnetospheric field-aligned currents. At the same time, narrowband Pc5 waves demonstrate typical resonant features in the amplitude-phase latitudinal structure. Thus, the location of the auroral oval (or its equatorward border) is the preferred latitude of magnetospheric field-line Alfven resonator excitation. This effect is not taken into account by modern theories of ULF Pc5 waves, but it could be significant for development of more adequate models.