Study of a global auroral Pc5 pulsation event with concurrent ULF waves

We present results from a study of concurrent, periodic variations in auroral luminosity (auroral pulsations) and in magnetospheric plasma/magnetic field data. This event occurred on 10 March 2010 from similar to 13 to 17 UT during an extended southward interplanetary magnetic field and was probably triggered by a slow shock. The auroral pulsations, as measured by the Ultraviolet Imager on board the Polar satellite, were long lasting (similar to 2.5 h), monochromatic (similar to 2.5mHz), large scale, and appeared in the night sector auroral zone with a latitudinal extent comparable to the latitudinal width of the oval. There was no phase shift between the auroral pulsations observed at different local times, indicating a stationary structure. Particle data from the Defense Meteorological Satellite Program Special Sensor Precipitating Electron and Ion Spectrometer indicate that the pulsations were diffuse originating from the central plasma sheet. During this time, Geotail was in the dawn sector plasma sheet and observed a ULF wave with the same frequency as the auroral pulsations last similar to 35 min. The ULF wave had large radial and compressional components, and the plasma density and total magnetic field were anticorrelated. These two observations strongly suggest that the observed ULF wave was associated with an standing ULF poloidal mode. The wave compressional component may be able to change the loss cone, resulting in periodic auroral precipitating.