Auroral Substrom Oscillations and Field Line Resonances

Wanliss et al. [2002] found luminosity oscillations in the aurora were often associated with substorms. The oscillations at different colors suggest periodicity in the particle precipitation. They examined CANOPUS photometer and magnetometer data of a magnetospheric substorm on April 1, 2000 at 0525 UT. For this study, we combine the spectral and phase information of 240 individual substorms, spanning ten years (1991 to 2000), to determine if the field line resonance (FLR) properties are common to all substorms. Periodicities in the photometer data are determined using the wavelet transform. As with the previous analysis, spectral data are organized by latitude and wavelength (470.9, 486.1, 557.7, and 630.0 nm). Each point of power in the wavelength versus frequency profile is identified as before or after substorm onset. We also separate events into categories of substorm or poleward boundary intensification (PBI) in order to distinguish the FLR properties of the event types.