ULF Waves and Relativistic Electron Acceleration and Losses from the Radiation Belts: A Superposed Epoch Analysis
Thursday, October 1, 2015
Marina Georgiou1, Ioannis A. Daglis1, Eftyhia Zesta2, Christos Katsavrias1, Georgios Balasis3, Ian Robert Mann4 and Kanaris Tsinganos1, (1)National and Kapodistrian University of Athens, Athens, Greece, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)National Observatory of Athens, Athens, Greece, (4)University of Alberta, Edmonton, AB, Canada
Abstract:
Geospace magnetic storms are associated with flux variations of electrons in the outer radiation belt. We examine the response of relativistic and ultra-relativistic electrons to 39 moderate and intense magnetic storms and compare these with concurrent observations of ULF wave power and of the plasmapause location. SAMPEX obsevations show that during 27 of the magnetic storms, the ultra-relativistic electron population of the outer radiation belt was enhanced. This enhancement was also evident in the phase space density derived from electron fluxes observed by the geosynchronous GOES satellites. On the other hand, the remaining 12 magnetic storms were not followed by enhancements in the relativistic electron population. We compare electron observations with the concurrent latitudinal and global distribution of wave power enhancements at Pc5 frequencies as detected by the CARISMA and IMAGE magnetometer arrays, as well as by magnetic stations collaborating in SuperMAG. During the main phase of both sets of magnetic storms, there is a pronounced penetration of Pc5 wave power to L shells as low as 2 — especially during magnetic storms characterised by enhanced post-storm electron fluxes. Later in the recovery phase, Pc5 wave activity returns to more typical values and radial distribution with a peak at outer L shells. Pc5 wave activity was found to persist longer for the electron-enhanced storms than for those that do not produce such enhancements. We put our Pc5 wave observations in the context of the plasmapause location, as determined by IMAGE EUV observations. Specifically, we discuss the growth and decay characteristics of Pc5 waves in association with the plasmapause location, as a controlling factor for wave power penetration deep into the magnetosphere.
