Pi2 pulsation periodicity and variations in magnetotail flows

Pi2 pulsations are a category of ULF waves with periods between 40-150 seconds frequently observed by ground-based magnetometers predominantly during substorm onset. The origin of these pulsations has been attributed to the coupling of Alfvenic oscillations associated with t he generation of the substorm current wedge, and fast-mode compressional waves moving radially inward from the tail, including plasmaspheric cavity modes at low-latitudes. It has recently been suggested that the frequencies of observed night-side auroral zone and low-latitude Pi2 pulsations, or Pi2 waveforms on the flanks, may be due to periodic variations in the sunward plasma flow from the tail such as during multiple bursty bulk flows (BBFs). Using a favourable conjun ction of the Geotail satellite with the CARISMA ground- based magnetometers on 23rd December 2000, the relationship between the frequency of Pi2 pulsations observed on the ground and periodicity in Earthward plasma flows has been inv estigated. Enhanced Earthward flows were seen during periods of substorm activity; however, using time-series analysis a direct link was not observed between the periodicity in the flow-bursts and the periodicity of pulsations within the Pi2 waveband.