Rapid Precipitation of Relativistic Electron by EMIC Rising‐Tone Emissions Observed by the Van Allen Probes

Nakamura, Satoko; Omura, Yoshiharu; Kletzing, C. A.; Baker, D. N.

doi:10.1029/2019ja026772

Cited by 32 publications

(47 citation statements)

References 49 publications

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“…Recent analysis (Kubota et al, ; Shoji & Omura, ) showed that rising tone EMIC emission can produce rapid heating of energetic protons around the equator because of the stable trapping, as well as the atmospheric losses of relativistic electrons inside the plasmasphere. Nakamura et al () presented direct Van Allen Probes observations of an event of rapid precipitation of relativistic electrons in timescale shorter than 1 min and in <1 hr of MLT, possibly through nonlinear trapping by EMIC rising tones. Quantitative assessment of the occurrence rates of EMIC rising tones is required to establish their importance to the ring current and radiation belts.…”

Section: The Role Of Nonlinear Processes In the Global Variability Ofmentioning

confidence: 99%

Particle Dynamics in the Earth's Radiation Belts: Review of Current Research and Open Questions

et al. 2020

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The past decade transformed our observational understanding of energetic particle processes in near‐Earth space. An unprecedented suite of observational systems was in operation including the Van Allen Probes, Arase, Magnetospheric Multiscale, Time History of Events and Macroscale Interactions during Substorms, Cluster, GPS, GOES, and Los Alamos National Laboratory‐GEO magnetospheric missions. They were supported by conjugate low‐altitude measurements on spacecraft, balloons, and ground‐based arrays. Together, these significantly improved our ability to determine and quantify the mechanisms that control the buildup and subsequent variability of energetic particle intensities in the inner magnetosphere. The high‐quality data from National Aeronautics and Space Administration's Van Allen Probes are the most comprehensive in situ measurements ever taken in the near‐Earth space radiation environment. These observations, coupled with recent advances in radiation belt theory and modeling, including dramatic increases in computational power, have ushered in a new era, perhaps a “golden era,” in radiation belt research. We have edited a Journal of Geophysical Research: Space Science Special Collection dedicated to Particle Dynamics in the Earth's Radiation Belts in which we gather the most recent scientific findings and understanding of this important region of geospace. This collection includes the results presented at the American Geophysical Union Chapman International Conference in Cascais, Portugal (March 2018) and many other recent and relevant contributions. The present article introduces and review the context, current research, and main questions that motivate modern radiation belt research divided into the following topics: (1) particle acceleration and transport, (2) particle loss, (3) the role of nonlinear processes, (4) new radiation belt modeling capabilities and the quantification of model uncertainties, and (5) laboratory plasma experiments.

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Section: The Role Of Nonlinear Processes In the Global Variability Ofmentioning

confidence: 99%

Particle Dynamics in the Earth's Radiation Belts: Review of Current Research and Open Questions

et al. 2020

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“…However, on the inbound half of orbit 3214, RBSP‐B observed larger amplitude EMIC waves than RBSP‐A and more rising tones than RBSP‐A. Some studies have suggested that EMIC waves with rising tones are more effective at particle scattering than unstructured EMIC waves (Kubota et al, 2015; Kubota & Omura, 2017; Nakamura et al, 2019). A detailed analysis of the EMIC rising tone triggered emissions observed on 22 December 2015, including wave normal analysis, proton distribution functions, and the rising tone frequency sweep rates, will be covered in a separate paper.…”

Section: Discussionmentioning

confidence: 99%

Simultaneous Observations of Electromagnetic Ion Cyclotron (EMIC) Waves and Pitch Angle Scattering During a Van Allen Probes Conjunction

et al. 2020

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On 22 December 2015, the two Van Allen Probes observed two sets of electromagnetic ion cyclotron (EMIC) wave bursts during a close conjunction when both Probe A and Probe B were separated by 0.57 to 0.68 R E . The EMIC waves occurred during an active period in the recovery phase of a coronal mass ejection-driven geomagnetic storm. Both spacecraft observed EMIC wave bursts that had similar spatial structure within a 1-2 min time delay. The EMIC waves occurred outside the plasmasphere, within ΔL ≈ 1-2 of the plasmapause and within a few degrees in magnetic latitude of the equatorial plane. The spatial structure of the EMIC wave bursts may have been related to the proton drift paths outside the plasmasphere and influenced by total magnetic field strength variations associated with solar wind pressure enhancements. The EMIC waves were observed in a narrow L shell region from L ≈ 4.55-5.32 between 10 and 11 magnetic local time (MLT) on the outbound halves of the spacecraft orbits and from L ≈ 4.82-5.51 between 13 and 14 MLT on the inbound halves of the spacecraft orbits. However, Pc1 pulsations were observed on the ground over a broad range of local times. The anisotropy of the proton pitch angle distributions was enhanced when the EMIC waves were observed. Although the overall radiation belt response during this storm was dominated by acceleration and transport processes, the EMIC waves produced local pitch angle scattering of 13-15 keV protons and 2.1-2.6 MeV electrons, consistent with calculations of the expected resonant energies.

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“…The present study focuses on the effect of the parallel‐propagating monochromatic EMIC waves with a moderate amplitude (3 nT). In fact, extremely large‐amplitude (~10 nT) EMIC waves are observed inside the Earth's inner magnetosphere (e.g., Engebretson et al, 2015; Nakamura et al, 2019). As the amplitude of EMIC waves increases, more electrons, either resonant or nonresonant, are expected to have nonlinear behaviors.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Nonlinear Interactions Between Relativistic Electrons and EMIC Waves in Magnetospheric Warm Plasma Environments

Cui

et al. 2020

JGR Space Physics

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With the kinetic dispersion relation and test particle simulation, we examine the effect of hot protons on the nonlinear interactions of relativistic electrons with electromagnetic ion cyclotron (EMIC) waves. We find that hot protons alter the refractive index of EMIC waves at a given wave frequency along latitude and thus modify resonance latitude. Consequently, resonance refractive index gradient along the magnetic field line, which plays a dominant role in controlling the electron behaviors, changes. Overall, the involvement of hot protons enlarges the resonance region (linear and nonlinear) but narrows the nonlinear resonance region. Additionally, hot protons weaken the electron phase bunching process and shift the electron phase trapping region to larger equatorial pitch angles. When the abundance or temperature anisotropy of hot protons increases, their effects on electron behaviors become more significant.

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Rapid Precipitation of Relativistic Electron by EMIC Rising‐Tone Emissions Observed by the Van Allen Probes

Cited by 32 publications

References 49 publications

Particle Dynamics in the Earth's Radiation Belts: Review of Current Research and Open Questions

Particle Dynamics in the Earth's Radiation Belts: Review of Current Research and Open Questions

Simultaneous Observations of Electromagnetic Ion Cyclotron (EMIC) Waves and Pitch Angle Scattering During a Van Allen Probes Conjunction

Nonlinear Interactions Between Relativistic Electrons and EMIC Waves in Magnetospheric Warm Plasma Environments

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