Antarctic Observations of Electromagnetic Ion Cyclotron (EMIC) Waves

Induction coil magnetometers have been operated in Antarctica for decades, both at permanent sites as well as remote (Automated Geophysical Observatory) sites. The permanent installations of NSF-funded instruments have included South Pole, McMurdo, Siple and Halley stations, although investigators from other countries have supported similar instruments at other stations. These instruments measure magnetic fluctuations at frequencies the order of .01-5 Hz, ideal for measuring EMIC waves that originate near Earth's equatorial magnetosphere and then propagate to the ground. In this presentation, we describe some recent results that demonstrate the usefulness of these data in understanding characteristics of these waves. Antarctic observations have been essential, for example, for quantifying ionospheric ducting of these waves. We also describe how these data are being used as part of a global network to study the persistence of EMIC wave generation in association with a High Speed Stream. Finally, new results show that the spectral content of EMIC waves, as observed from the ground, has changed over the past several years (with increased solar activity) to now include signatures as high as 2 Hz, where data from 2007, for example, only exceeded 1 Hz infrequently. All of these results are directly relevant to radiation belt dynamics, where the waves are thought to directly interact with energetic ions and electrons.