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Found 4 entries in the Bibliography.
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2020 |
Global ENA Imaging and In Situ Observations of Substorm Dipolarization on 10 August 2016 Abstract This paper presents the first combined use of data from Magnetospheric Multiscale (MMS), Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS), and Van Allen Probes (RBSP) to study the 10 August 2016 magnetic dipolarization. We report the first correlation of MMS tail observations with TWINS energetic neutral atom (ENA) images of the ring current (RC). We analyze 15-min, 1° TWINS 2 images in 1–50 keV energy bins. To characterize the high-altitude RC we extract peak ENA flux from L= 2.5 to 5 in the postmidnight sector. We estimate peak low-altitude ion flux from ENAs near the Earth s limb. For a local perspective, we use spin-averaged proton fluxes from the RBSP A Helium Oxygen Proton Electron (HOPE) spectrometer. We find that the 1000 UT dipolarization triggered an abrupt and significant increase in low-altitude ions and a gradual but modest increase in the high-altitude RC. The relative strength and timing of the low versus high-altitude flux indicate that the dipolarization isotropized the injected ions and initially filled the loss cone. The substorm injection brought cooler ions in from the magnetotail, reducing the peak energy at both low and high altitudes. The post-dipolarization low-altitude flux exhibited a decay rate dispersion favoring longer decay times at lower energies, possibly caused by growth of the low energy RC providing enhanced flux into the loss cone. A variety of finer scale local injection structures were observed in the high-altitude RC both before and after the dipolarization, and the average system level RC intensity increased after 1000 UT. Goldstein, J.; Valek, P.; McComas, D.; Redfern, J.; Spence, H.; Skoug, R.; Larsen, B.; Reeves, G.; Nakamura, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 04/2020 YEAR: 2020   DOI: 10.1029/2019JA027733 substorm dipolarization; cross-scale physics; imaging; multipoint in situ; ring current; Van Allen Probes |
Global ENA Imaging and In Situ Observations of Substorm Dipolarization on 10 August 2016 This paper presents the first combined use of data from Magnetospheric Multiscale (MMS), Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS), and Van Allen Probes (RBSP) to study the 10 August 2016 magnetic dipolarization. We report the first correlation of MMS tail observations with TWINS energetic neutral atom (ENA) images of the ring current (RC). We analyze 15-min, 1° TWINS 2 images in 1–50 keV energy bins. To characterize the high-altitude RC we extract peak ENA flux from L= 2.5 to 5 in the postmidnight sector. We estimate peak low-altitude ion flux from ENAs near the Earth s limb. For a local perspective, we use spin-averaged proton fluxes from the RBSP A Helium Oxygen Proton Electron (HOPE) spectrometer. We find that the 1000 UT dipolarization triggered an abrupt and significant increase in low-altitude ions and a gradual but modest increase in the high-altitude RC. The relative strength and timing of the low versus high-altitude flux indicate that the dipolarization isotropized the injected ions and initially filled the loss cone. The substorm injection brought cooler ions in from the magnetotail, reducing the peak energy at both low and high altitudes. The post-dipolarization low-altitude flux exhibited a decay rate dispersion favoring longer decay times at lower energies, possibly caused by growth of the low energy RC providing enhanced flux into the loss cone. A variety of finer scale local injection structures were observed in the high-altitude RC both before and after the dipolarization, and the average system level RC intensity increased after 1000 UT. Goldstein, J.; Valek, P.; McComas, D.; Redfern, J.; Spence, H.; Skoug, R.; Larsen, B.; Reeves, G.; Nakamura, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 04/2020 YEAR: 2020   DOI: https://doi.org/10.1029/2019JA027733 substorm dipolarization; cross-scale physics; imaging; multipoint in situ; ring current |
2015 |
Substorms generally inject 10s-100s keV electrons, but intense substorm electric fields have been shown to inject MeV electrons as well. An intriguing question is whether such MeV electron injections can populate the outer radiation belt. Here we present observations of a substorm injection of MeV electrons into the inner magnetosphere. In the pre-midnight sector at L\~5.5, Van Allen Probes (RBSP)-A observed a large dipolarization electric field (50mV/m) over \~40s and a dispersionless injection of electrons up to \~3 MeV. Pitch angle observations indicated betatron acceleration of MeV electrons at the dipolarization front. Corresponding signals of MeV electron injection were observed at LANL-GEO, THEMIS-D, and GOES at geosynchronous altitude. Through a series of dipolarizations, the injections increased the MeV electron phase space density by one order of magnitude in less than 3 hours in the outer radiation belt (L>4.8). Our observations provide evidence that deep injections can supply significant MeV electrons. Dai, Lei; Wang, Chi; Duan, Suping; He, Zhaohai; Wygant, John; Cattell, Cynthia; Tao, Xin; Su, Zhenpeng; Kletzing, Craig; Baker, Daniel; Li, Xinlin; Malaspina, David; Blake, Bernard; Fennell, Joseph; Claudepierre, Seth; Turner, Drew; Reeves, Geoffrey; Funsten, Herbert; Spence, Harlan; Angelopoulos, Vassilis; Fruehauff, Dennis; Chen, Lunjin; Thaller, Scott; Breneman, Aaron; Tang, Xiangwei; Published by: Geophysical Research Letters Published on: 07/2015 YEAR: 2015   DOI: 10.1002/2015GL064955 electric fields; radiation belt electrons; substorm dipolarization; substorm injection; Van Allen Probes |
2014 |
Observation and model results accumulated in the last decade indicate that substorms can promptly inject relativistic \textquoteleftkiller\textquoteright electrons (>=MeV) in addition to 10\textendash100 keV subrelativistic populations. Using measurements from Cluster, Polar, LANL, and GOES satellites near the midnight sector, we show in two events that intense electric fields, as large as 20 mV/m, associated with substorm dipolarization are associated with injections of relativistic electrons into the outer radiation belt. Enhancements of hundreds of keV electrons at dipolarization in the magnetotail can account for the injected MeV electrons through earthward transport. These observations provide evidence that substorm electric fields inject relativistic electrons by transporting magnetotail electrons into the outer radiation belt. In these two events, injected relativistic electrons dominated the substorm timescale enhancement of MeV electrons as observed at geosynchronous orbit. Dai, Lei; Wygant, John; Cattell, Cynthia; Thaller, Scott; Kersten, Kris; Breneman, Aaron; Tang, Xiangwei; Friedel, Reiner; Claudepierre, Seth; Tao, Xin; Published by: Geophysical Research Letters Published on: 02/2014 YEAR: 2014   DOI: 10.1002/2014GL059228 radiation belt relativistic electrons; substorm dipolarization; substorm electric fields; substorm injection |
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