Found 13 results
Filters: Author is Singer, H. J.  [Clear All Filters]
Authors: Mann I. R., Ozeke L. G., Morley S. K., Murphy K. R., Claudepierre S G, et al.
Title: Reply to 'The dynamics of Van Allen belts revisited'
Abstract: N/A
Date: 02/2019 Publisher: Nature Physics Pages: 103 - 104 DOI: 10.1038/nphys4351 Available at:
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Authors: Engebretson M. J., Posch J. L., Braun D. J., Li W, Ma Q, et al.
Title: EMIC wave events during the four GEM QARBM challenge intervals
Abstract: This paper presents observations of EMIC waves from multiple data sources during the four GEM challenge events in 2013 selected by the GEM “Quantitative Assessment of Radiation Belt Modeling” focus group: March 17‐18 (Stormtime Enhancement), May 31‐June 2 (Stormtime Dropout), September 19‐20 (Non‐storm Enhancement), and September 23‐25 (Non‐storm Dropout). Observations include EMIC wave data from the Van Allen Probes, GOES, and THEMIS spacecraft in the near‐equatorial magnetosphere and from several arrays of ground‐based search coil magnetometers worldwide, as well as localized ring current proton precipitation data from low‐altitude POES spacecraft. Each of these data sets provides only limited spatial coverage, but their combination shows consistent occurrence patte. . .
Date: 07/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025505 Available at:
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Authors: Remya B., Sibeck D G, Halford A J, Murphy K. R., Reeves G D, et al.
Title: Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere
Abstract: We present Van Allen Probe observations of electromagnetic ion cyclotron (EMIC) waves triggered solely due to individual substorm‐injected ions in the absence of storms or compressions of the magnetosphere during 9 August 2015. The time at which the injected ions are observed directly corresponds to the onset of EMIC waves at the location of Van Allen Probe A (L = 5.5 and 18:06 magnetic local time). The injection was also seen at geosynchronous orbit by the Geostationary Operational Environmental Satellite and Los Alamos National Laboratory spacecraft, and the westward(eastward) drift of ions(electrons) was monitored by Los Alamos National Laboratory spacecraft at different local times. The azimuthal location of the injection was determined by tracing the injection signatures backward in. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025354 Available at:
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Authors: Engebretson M. J., Posch J. L., Capman N. S. S., Campuzano N. G., ělik P., et al.
Title: MMS, Van Allen Probes, GOES 13, and Ground Based Magnetometer Observations of EMIC Wave Events Before, During, and After a Modest Interplanetary Shock
Abstract: The stimulation of EMIC waves by a magnetospheric compression is perhaps the closest thing to a controlled experiment that is currently possible in magnetospheric physics, in that one prominent factor that can increase wave growth acts at a well‐defined time. We present a detailed analysis of EMIC waves observed in the outer dayside magnetosphere by the four Magnetosphere Multiscale (MMS) spacecraft, Van Allen Probe A, and GOES 13, and by four very high latitude ground magnetometer stations in the western hemisphere before, during, and after a modest interplanetary shock on December 14, 2015. Analysis shows several features consistent with current theory, as well as some unexpected features. During the most intense MMS wave burst, which began ~ 1 min after the end of a brief magnetosheat. . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025984 Available at:
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Authors: Ohtani S, Motoba T., Gkioulidou M., Takahashi K., and Singer H J
Title: Spatial Development of the Dipolarization Region in the Inner Magnetosphere
Abstract: The present study examines dipolarization events observed by the Van Allen Probes within 5.8 RE from Earth. It is found that the probability of occurrence is significantly higher in the dusk‐to‐midnight sector than in the midnight‐to‐dawn sector, and it deceases sharply earthward. A comparison with observations made at nearby satellites shows that dipolarization signatures are often highly correlated (c.c. > 0.8) within 1 hr in MLT and 1 RE in RXY, and the dipolarization region expands earthward and westward in the dusk‐to‐midnight sector. The westward expansion velocity is estimated at 0.4 hr (in MLT) per minute, or 60 km/s, which is consistent with the previously reported result for geosynchronous dipolarization. The earthward expansion is apparently less systematic than the . . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025443 Available at:
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Authors: Le G., Chi P. J., Strangeway R J, Russell C. T., Slavin J. A., et al.
Title: Global observations of magnetospheric high- m poloidal waves during the 22 June 2015 magnetic storm
Abstract: We report global observations of high-m poloidal waves during the recovery phase of the 22 June 2015 magnetic storm from a constellation of widely spaced satellites of five missions including Magnetospheric Multiscale (MMS), Van Allen Probes, Time History of Events and Macroscale Interactions during Substorm (THEMIS), Cluster, and Geostationary Operational Environmental Satellites (GOES). The combined observations demonstrate the global spatial extent of storm time poloidal waves. MMS observations confirm high azimuthal wave numbers (m ~ 100). Mode identification indicates the waves are associated with the second harmonic of field line resonances. The wave frequencies exhibit a decreasing trend as L increases, distinguishing them from the single-frequency global poloidal modes normally obs. . .
Date: 04/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073048 Available at:
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Authors: Mann I. R., Ozeke L. G., Murphy K. R., Claudepierre S G, Turner D. L., et al.
Title: Explaining the dynamics of the ultra-relativistic third Van Allen radiation belt
Abstract: Since the discovery of the Van Allen radiation belts over 50 years ago, an explanation for their complete dynamics has remained elusive. Especially challenging is understanding the recently discovered ultra-relativistic third electron radiation belt. Current theory asserts that loss in the heart of the outer belt, essential to the formation of the third belt, must be controlled by high-frequency plasma wave–particle scattering into the atmosphere, via whistler mode chorus, plasmaspheric hiss, or electromagnetic ion cyclotron waves. However, this has failed to accurately reproduce the third belt. Using a datadriven, time-dependent specification of ultra-low-frequency (ULF) waves we show for the first time how the third radiation belt is established as a simple, elegant consequence o. . .
Date: 06/2016 Publisher: Nature Physics DOI: 10.1038/nphys3799 Available at:
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Authors: Sigsbee K., Kletzing C A, Smith C W, MacDowall Robert, Spence Harlan, et al.
Title: Van Allen Probes, THEMIS, GOES, and Cluster Observations of EMIC waves, ULF pulsations, and an electron flux dropout
Abstract: We examined an electron flux dropout during the 12–14 November 2012 geomagnetic storm using observations from seven spacecraft: the two Van Allen Probes, THEMIS-A (P5), Cluster 2, and Geostationary Operational Environmental Satellite (GOES) 13, 14, and 15. The electron fluxes for energies greater than 2.0 MeV observed by GOES 13, 14, and 15 at geosynchronous orbit and by the Van Allen Probes remained at or near instrumental background levels for more than 24 hours from 12–14 November. For energies of 0.8 MeV, the GOES satellites observed two shorter intervals of reduced electron fluxes. The first interval of reduced 0.8 MeV electron fluxes on 12–13 November was associated with an interplanetary shock and a sudden impulse. Cluster, THEMIS, and GOES observed intense He+ EMIC wa. . .
Date: 01/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020877 Available at:
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Authors: Hwang K.-J., Sibeck D G, Fok M.-C. H., Zheng Y., Nishimura Y., et al.
Title: The global context of the 14 November, 2012 storm event
Abstract: From 2 to 5 UT on 14 November, 2012, the Van Allen Probes observed repeated particle flux dropouts during the main phase of a geomagnetic storm as the satellites traversed the post-midnight to dawnside inner magnetosphere. Each flux dropout corresponded to an abrupt change in the magnetic topology, i.e., from a more dipolar configuration to a configuration with magnetic field lines stretched in the dawn-dusk direction. Geosynchronous GOES spacecraft located in the dusk and near-midnight sectors and the LANL constellation with wide local time coverage also observed repeated flux dropouts and stretched field lines with similar occurrence patterns to those of the Van Allen Probe events. THEMIS recorded multiple transient abrupt expansions of the evening-side magnetopause ~20–30 min prior to. . .
Date: 02/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020826 Available at:
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Authors: Paral J., Hudson M K, Kress B T, Wiltberger M. J., Wygant J R, et al.
Title: Magnetohydrodynamic modeling of three Van Allen Probes storms in 2012 and 2013
Abstract: Coronal mass ejection (CME)-shock compression of the dayside magnetopause has been observed to cause both prompt enhancement of radiation belt electron flux due to inward radial transport of electrons conserving their first adiabatic invariant and prompt losses which at times entirely eliminate the outer zone. Recent numerical studies suggest that enhanced ultra-low frequency (ULF) wave activity is necessary to explain electron losses deeper inside the magnetosphere than magnetopause incursion following CME-shock arrival. A combination of radial transport and magnetopause shadowing can account for losses observed at radial distances into L = 4.5, well within the computed magnetopause location. We compare ULF wave power from the Electric Field and Waves (EFW) electric field instrument on th. . .
Date: 08/2015 Publisher: Annales Geophysicae Pages: 1037 - 1050 DOI: 10.5194/angeo-33-1037-2015 Available at:
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Authors: Engebretson M. J., Posch J. L., Wygant J R, Kletzing C A, Lessard M. R., et al.
Title: Van Allen probes, NOAA, GOES, and ground observations of an intense EMIC wave event extending over 12 hours in MLT
Abstract: Although most studies of the effects of EMIC waves on Earth's outer radiation belt have focused on events in the afternoon sector in the outer plasmasphere or plume region, strong magnetospheric compressions provide an additional stimulus for EMIC wave generation across a large range of local times and L shells. We present here observations of the effects of a wave event on February 23, 2014 that extended over 8 hours in UT and over 12 hours in local time, stimulated by a gradual 4-hour rise and subsequent sharp increases in solar wind pressure. Large-amplitude linearly polarized hydrogen band EMIC waves (up to 25 nT p-p) appeared for over 4 hours at both Van Allen Probes, from late morning through local noon, when these spacecraft were outside the plasmapause, with densities ~5-20 cm-3. W. . .
Date: 06/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021227 Available at:
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Authors: Sergeev V. A., Nikolaev A. V., Tsyganenko N A, Angelopoulos V, Runov A. V., et al.
Title: Testing a two-loop pattern of the substorm current wedge (SCW2L)
Abstract: Recent quantitative testing of the classical (region 1 sense) substorm current wedge (SCI) model revealed systematic discrepancies between the observed and predicted amplitudes, which suggested us to include additional region 2 sense currents (R2 loop) earthward of the dipolarized region (SCW2L model). Here we discuss alternative circuit geometries of the 3-D substorm current system and interpret observations of the magnetic field dipolarizations made between 6.6RE and 11RE, to quantitatively investigate the SCW2L model parameters. During two cases of a dipole-like magnetotail configuration, the dipolarization/injection front fortuitously stopped at r ~ 9RE for the entire duration of ~ 30 min long SCW-related dipolarization within a unique, radially distributed multispacecraft constellat. . .
Date: 02/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 947 - 963 DOI: 10.1002/2013JA019629 Available at:
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Authors: Ohtani S, Miyoshi Y, Singer H J, and Weygand J M
Title: On the loss of relativistic electrons at geosynchronous altitude: Its dependence on magnetic configurations and external conditions
Abstract: [1] The present study statistically examines geosynchronous magnetic configurations and external conditions that characterize the loss of geosynchronous MeV electrons. The loss of MeV electrons often takes place during magnetospheric storms, but it also takes place without any clear storm activity. It is found that irrespective of storm activity, the day-night asymmetry of the geosynchronous H (north-south) magnetic component is pronounced during electron loss events. For the loss process, the magnitude, rather than the duration, of the magnetic distortion appears to be important, and its effective duration can be as short as ∼30 min. The solar wind dynamic pressure tends to be high and interplanetary magnetic field BZ tends to be southward during electron loss events. Under such externa. . .
Date: 01/2009 Publisher: Journal of Geophysical Research DOI: 10.1029/2008JA013391 Available at:
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