Solar cycle dependence of ion cyclotron wave frequencies
Thursday, 4 September 2014: 12:10 PM
Regency Ballroom (Hyatt Regency)
Marc Lessard1, Carol Weaver1, Erik Anders Lindgren1, Kristoff W Paulson1,2 and Mark J. Engebretson3, (1)University of New Hampshire, Durham, NH, United States, (2)University of New Hampshire, Chelmsford, MA, United States, (3)Augsburg College, Minneapolis, MN, United States
Abstract:
Electromagnetic ion cyclotron (EMIC) waves have been studied for decades, though remain a fundamentally important topic in heliospheric physics. The connection of EMIC waves to the scattering of energetic particles from Earthâs radiation belts is one of many topics that motivate the need for a deeper understanding of characteristics and occurrence distributions of the waves. In this study, we show that EMIC wave frequencies, as observed at Halley Station in Antarctica from 2008 through 2012, increase by approximately 50% from 2009 to 2012. Assuming that these waves may be excited in the vicinity of the plasmapause, the change in Kp in going from solar minimum to near solar maximum would drive increased plasmapause erosion, thereby shifting the generation region of the EMIC to lower L and resulting in the higher frequencies. Numerical results from a Kp-driven empirical model over this period show an inward shift of the plasmapause of ~0.6 RE in the region (which is near dawn for these events), suggesting that plasmapause erosion may play a role in this effect.
