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Multipoint Spacecraft Observations of Long-Lasting Poloidal Pc4 Pulsations in the Dayside Magnetosphere on 1-2 May 2014We use magnetic field and plasma observations from the Van Allen Probes, Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Geostationary Operational Environmental Satellite system (GOES) spacecraft to study the spatial and temporal characteristics of long-lasting poloidal Pc4 pulsations in the dayside magnetosphere. The pulsations were observed after the main phase of a moderate storm during low geomagnetic activity. The pulsations occurred during various interplanetary conditions and the solar wind parameters do not seem to control the occurrence of the pulsations. The most striking feature of the Pc4 magnetic field pulsations was their occurrence at similar locations during three of four successive orbits. We used this information to study the latitudinal nodal structure of the pulsations and demonstrated that the latitudinal extent of the magnetic field pulsations did not exceed 2 Earth radii (R(sub E)). A phase shift between the azimuthal and radial components of the electric and magnetic fields was observed from Z(sub SM) = 0.30 R(sub E) to Z(sub SM) = -0.16 R(sub E). We used magnetic and electric field data from Van Allen Probes to determine the structure of ULF waves. We showed that the Pc4 magnetic field pulsations were radially polarized and are the second-mode harmonic waves. We suggest that the spacecraft were near a magnetic field null during the second orbit when they failed to observe the magnetic field pulsations at the local times where pulsations were observed on previous and successive orbits. We investigated the spectral structure of the Pc4 pulsations. Each spacecraft observed a decrease of the dominant period as it moved to a smaller L shell (stronger magnetic field strength). We demonstrated that higher frequencies occurred at times and locations where Alfven velocities were greater, i.e., on Orbit 1. There is some evidence that the periods of the pulsations increased during the plasmasphere refilling following the storm.
Document ID
20170003139
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Korotova, Galina
(Maryland Univ. College Park, MD, United States)
Sibeck, David
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Engebretson, Mark
(Augsburg Coll. Minneapolis, MN, United States)
Wygant, John
(Minnesota Univ. Minneapolis, MN, United States)
Thaller, Scott
(Minnesota Univ. Minneapolis, MN, United States)
Spence, Harlan
(New Hampshire Univ. Durham, NH, United States)
Kletzing, Craig
(Iowa Univ. Iowa City, IA, United States)
Angelopoulos, Vassilis
(California Univ. Los Angeles, CA, United States)
Redmon, Robert
(National Geophysical and Solar-Terrestrial Data Center Boulder, CO, United States)
Date Acquired
April 7, 2017
Publication Date
November 14, 2016
Publication Information
Publication: Annales Geophysicae
Publisher: Copernicus Publications
Volume: 34
Issue: 11
ISSN: 0992-7689
e-ISSN: 1432-0576
Subject Category
Geophysics
Report/Patent Number
GSFC-E-DAA-TN41109
Funding Number(s)
CONTRACT_GRANT: NSF AGS-1207445
CONTRACT_GRANT: NNX15AW86G
Distribution Limits
Public
Copyright
Other

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