A Conjugate Study of ULF Waves at the Cusp: A GEM Project

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This is a proposal to study the ULF wave spectrum at cusp stations in conjugate hemispheres. An auroral observatory located at Longyearbyen, Svalbard in the northern hemisphere has been in operation for nearly a decade and is equipped with induction coil and fluxgate magnetometers to measure the ULF wave spectrum. The station is also instrumented with all-sky and meridian scanning photometers which provide an optical context for the magnetic measurements. In the southern hemisphere, the Australian station at Davis, Antarctica is also equipped with induction coil and fluxgate magnetometers and has made observations of the ULF wave spectrum associated with the cusp for several year. We have begun an echange of data and the analysis shows promising correlations. It is well known that the cusp region is a rich source of ULF waves spanning the frequency spectrum from near dc to above Hz. The spectrum consists of an ensemble of waves and variations with causes ranging from boundary motions and macroscopic boundary instabilities at the low frequency end, through impulsive and coherent signals with correlation to the solar wind at intermediate frequencies, up to an beyond ion-cyclotron waves generated in the unstable plasma near the magnetospheric boundary layers and shocked cusp plasma. Our work in this analysis is aided by through collaboration with the plasma simulation group at the Geophysical Institute. Our goal is to collect ULF data at the two sites on a campaign basis in order to: o investigate the conjugacy of the cusp at these sites; o identify wave generation mechanisms associated with the cusp; o inspect the ULF spectrum at the two sites for correlations; o identify signatures of flux transfer and particle injection at the magnetopause; o use the waves as a diagnostic for location of the boundaries.