Simultaneous ULF waves, whistler-mode chorus and pulsating aurora observed by the Van Allen Probes and ground-based systems

Tuesday, 16 December 2014
Allison N Jaynes, University of Colorado at Boulder, Boulder, CO, United States, Marc Lessard, University of New Hampshire Main Campus, Durham, NH, United States, Kazue Takahashi, Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, Craig Kletzing, University of Iowa, Iowa City, IA, United States, John R Wygant, University of Minnesota Twin Cities, Minneapolis, MN, United States, Eric Donovan, University of Calgary, Calgary, AB, Canada and J Bernard Blake, The Aerospace Corp, Los Angeles, CA, United States
Theory and observations have linked equatorial VLF waves with pulsating aurora for decades, invoking the process of pitch-angle scattering of 10's keV electrons in the equatorial magnetosphere. Recent satellite studies have strengthened this argument, by showing strong correlation between pulsating auroral patches and (1) lower-band chorus observed by THEMIS and (2) 30-100 keV electron modulation in the vicinity of geosynchronous orbit observed by GOES. Additionally, a link has been made between Pc4-5 compressional pulsations and modulation of whistler-mode chorus using THEMIS. Here we present simultaneous in-situ observations of structured chorus waves and an apparent poloidal field line resonance as a result of a substorm injection, observed by Van Allen Probes, along with ground-based observations of pulsating aurora. We demonstrate the possible scenario being one of substorm-driven ULF pulsations modulating chorus waves, and thus providing the driver for pulsating particle precipitation into the Earth's atmosphere. We also show, for the first time, a particular 3-Hz modulation of individual chorus elements concurrent with pulsating aurora. Such modulation has been noticed in camera data of pulsating aurora for decades.