title: Global-scale coherence modulation of radiation-belt electron loss from plasmaspheric hiss.
abstract: Over 40 years ago it was suggested that electron loss in the region of the radiation belts that overlaps with the region of high plasma density called the plasmasphere, within four to five Earth radii, arises largely from interaction with an electromagnetic plasma wave called plasmaspheric hiss. This interaction strongly influences the evolution of the radiation belts during a geomagnetic storm, and over the course of many hours to days helps to return the radiation-belt structure to its 'quiet' pre-storm configuration. Observations have shown that the long-term electron-loss rate is consistent with this theory but the temporal and spatial dynamics of the loss process remain to be directly verified. Here we report simultaneous measurements of structured radiation-belt electron losses and the hiss phenomenon that causes the losses. Losses were observed in the form of bremsstrahlung X-rays generated by hiss-scattered electrons colliding with the Earth's atmosphere after removal from the radiation belts. Our results show that changes of up to an order of magnitude in the dynamics of electron loss arising from hiss occur on timescales as short as one to twenty minutes, in association with modulations in plasma density and magnetic field. Furthermore, these loss dynamics are coherent with hiss dynamics on spatial scales comparable to the size of the plasmasphere. This nearly global-scale coherence was not predicted and may affect the short-term evolution of the radiation belts during active times.
authors.affiliation: School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: A W
authors.initials: AW
authors.lastname: Breneman
authors.affiliation: Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755, USA.
authors.forename: A
authors.initials: A
authors.lastname: Halford
authors.affiliation: Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755, USA.
authors.forename: R
authors.initials: R
authors.lastname: Millan
authors.affiliation: Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA.
authors.forename: M
authors.initials: M
authors.lastname: McCarthy
authors.affiliation: Aerospace Corporation, Los Angeles, California 90009, USA.
authors.forename: J
authors.initials: J
authors.lastname: Fennell
authors.affiliation: Space Sciences Laboratory, University of California, Berkeley, California 94720, USA.
authors.forename: J
authors.initials: J
authors.lastname: Sample
authors.affiliation: Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755, USA.
authors.forename: L
authors.initials: L
authors.lastname: Woodger
authors.affiliation: Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: G
authors.initials: G
authors.lastname: Hospodarsky
authors.affiliation: School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Wygant
authors.affiliation: School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Cattell
authors.affiliation: Southwest Research Institute, San Antonio, Texas 78238, USA.
authors.forename: J
authors.initials: J
authors.lastname: Goldstein
authors.affiliation: University of Colorado, The Laboratory for Atmospheric and Space Physics (LASP), Boulder, Colorado 80303, USA.
authors.forename: D
authors.initials: D
authors.lastname: Malaspina
authors.affiliation: Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Kletzing