Characteristics of ULF Waves at Very High Latitudes Inferred From Ground-Based Magnetometer Observations

Using observations from the Greenland magnetometer chain at 1-Hz sampling rate we have the possibility to study ULF waves over a wide frequency band and a latitude range which extends across most of the auroral zone and deep into the polar cap, i.e. covering the transition from field lines which are often closed in the magnetosphere to those which are always open. We examine Greenland magnetometer observations from 2003, 2004 and 2005 with the objective to characterize the frequency and latitude dependence of ULF wave activity during quiet and stormy times. To do so we select several frequency bands and bin the magnetometer observations according to the level of geomagnetic activity as defined by various geomagnetic indices. We further infer statistical patterns of ULF activity between 66 and 85 deg geomagnetic latitude over all magnetic local times. The investigation includes examining the temporal development of ULF wave activity in relation to the progress of a magnetic storm.