SM41F-2547
Location of EMIC Wave Events Relative to the Plasmapause: Van Allen Probes Observations
Thursday, 17 December 2015
Poster Hall (Moscone South)
Sadie Tetrick1, Mark J. Engebretson1, Jennifer L Posch1, Craig Kletzing2, Charles William Smith3, John R Wygant4, Matina Gkioulidou5 and Geoffrey D Reeves6, (1)Augsburg College, Minneapolis, MN, United States, (2)University of Iowa, Iowa City, IA, United States, (3)University of New Hampshire Main Campus, Durham, NH, United States, (4)University of Minnesota Twin Cities, Minneapolis, MN, United States, (5)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, (6)Los Alamos National Laboratory, Los Alamos, NM, United States
Abstract:
Many early theoretical studies of electromagnetic ion cyclotron (EMIC) waves generated in Earth’s magnetosphere predicted that the equatorial plasmapause (PP) would be a preferred location for their generation. However, several large statistical studies in the past two decades, most notably Fraser and Nguyen [2001], have provided little support for this location. In this study we present a survey of the most intense EMIC waves observed by the EMFISIS fluxgate magnetometer on the Van Allen Probes-A spacecraft (with apogee at 5.9 RE) from its launch through the end of 2014, and have compared their location with simultaneous electron density data obtained by the EFW electric field instrument and ring current ion flux data obtained by the HOPE and RBSPICE instruments. We show distributions of these waves as a function of distance inside or outside the PP as a function of local time sector, frequency band (H+, He+, or both), and timing relative to magnetic storms and substorms. Most EMIC waves in this data set occurred within 1 RE of the PP in all local time sectors, but very few were limited to ± 0.1 RE, and most of these occurred in the 06-12 MLT sector during non-storm conditions. The majority of storm main phase waves in the dusk sector occurred inside the PP. He+ band waves dominated at most local times inside the PP, and H+ band waves were never observed there. Although the presence of elevated fluxes of ring current protons was common to all events, the configuration of lower energy ion populations varied as a function of geomagnetic activity and storm phase.
