Estimation of pitch angle diffusion rates and precipitation time scales of electrons due to EMIC waves in a realistic field model

Kang, Seungbum; Kang, Min; Fok, M. C. H.; Hwang, Junga; Choi, Chang‐Shik

doi:10.1002/2014ja020644

Cited by 18 publications

(21 citation statements)

References 69 publications

(178 reference statements)

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“…To the authors' knowledge, only Orlova and Shprits () have succeeded in accounting for the Kp‐variable T89 magnetic field (Tsyganenko, ) into the computation of pitch angle diffusion coefficients that were based on CRRES data. A similar effort was made in Kang et al () who computed pitch angle diffusion coefficients but with the simpler parallel approximation of Summers () and the Tsyganenko 04 (T04) magnetic field model (Tsyganenko & Sitnov, ). With the same motivation, Cunningham () has proposed a new theoretical formalism, this time, for radial diffusion coefficients, that accounts for the variability of the magnetic field, yet this is very new and complex and has yet to be broadly tested or used.…”

Section: New Radiation Belt Modeling Capabilities and The Quantificatmentioning

confidence: 96%

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: New Radiation Belt Modeling Capabilities and The Quantificatmentioning

confidence: 96%

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

et al. 2020

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“…Electromagnetic ion cyclotron (EMIC) waves have long been known to play critical roles in the inner magnetosphere by interacting with various species of charged particles over a large‐energy range, including atmospheric precipitation of energetic particles and heating of cold electrons and He + ions [e.g., Kennel and Petschek , ; Cornwall et al ., ; Gendrin et al ., ; Jordanova et al ., ; Summers and Thorne , ; Zhang et al ., ; Shprits et al ., ; Yuan et al ., , ; Zhou et al ., ; Kang et al ., ; Ni et al ., ]. The conventional view for generation of the EMIC waves is based on resonant interaction of L mode ion cyclotron waves near proton gyrofrequency with hot anisotropic protons [e.g., Kennel and Petschek , ].…”

Section: Introductionmentioning

confidence: 99%

Effect of hot anisotropic He⁺ ions on the growth and damping of electromagnetic ion cyclotron waves in the inner magnetosphere

et al. 2017

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Physics of electromagnetic ion cyclotron (EMIC) waves is complicated by inclusion of heavy ions. In particular, He+ ions in the magnetosphere have long been considered to play important roles. Motivated by recent observations, we examine the effect of the inclusion of hot anisotropic He+ ions in addition to the usual hot anisotropic protons. We solve the kinetic dispersion relation for this examination and find the following results. First, inclusion of hot anisotropic He+ ions leads to the growth of EMIC waves at frequencies below the He+ gyrofrequency (He band) and a reduction of the EMIC wave growth rates (or damping of the waves) at frequencies between the proton and He+ gyrofrequencies (H band). Second, this effect is more dramatic for higher temperatures of He+ that would play a role in damping EMIC waves for both frequency bands and especially for cases without a He+ temperature anisotropy. Lastly, the effect is more prominent for cold plasma dominant conditions such as the region inside the plasmasphere or plume than for hot proton dominant conditions such as the region outside the plasmasphere. We propose that this last effect can at least partially explain the satellite observations indicating the preferred (though not exclusive) occurrence of He band waves inside the plasmasphere for the times when hot anisotropic He+ ions are supplied from the plasma sheet and ring current.

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“…Since EMIC waves interact with energetic ring current ions and relativistic electrons and cause loss of these particles into the Earth's atmosphere through pitch angle scattering [e.g., Kennel and Petschek, 1966;Thorne and Kennel, 1971;Erlandson and Ukhorskiy, 2001;Summers and Thorne, 2003], their activities are critical to the dynamics of ring current and radiation belt particles, in particular for MeV electrons [e.g., Horne, 2002;Summers and Thorne, 2003;Kang et al, 2015]. Observations of precipitating ring current or radian belt particles at low-altitude polar-orbiting spacecraft during the occurrence of EMIC waves support the theory of resonant wave-particle interactions with EMIC waves [e.g., Yahnina et al, 2000;Miyoshi et al, 2008;Yuan et al, 2012;Hyun et al, 2014;Kim et al, 2016].…”

Section: Introductionmentioning

confidence: 99%

Spectral characteristics of steady quiet‐time EMIC waves observed at geosynchronous orbit

et al. 2016

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We have studied the spectral properties of quiet‐time electromagnetic ion cyclotron (EMIC) waves following a steady quiet condition, which is defined with Kp values ≤1 during 12 h, using GOES 10, 11, and 12 magnetometer data for solar minimum years 2007–2008. We identified 6584 steady quiet‐time EMIC wave samples using a semiautomated procedure. Approximately 82% of the samples were observed in the morning‐to‐early afternoon sector (0700–1500 magnetic local time) with a maximum occurrence near noon, and their peak frequencies were mostly in the He band. We found that the occurrence rate of steady quiet‐time EMIC waves is higher than that of EMIC waves for all or quiet geomagnetic conditions (Dst > 0 nT or AE < 100 nT) reported in previous studies by a factor of 2 or more. The frequency ratio fpeak (sample's peak frequency)/ fH+ (the local proton gyrofrequency) of the He‐band waves (∼0.11–0.16) under steady quiet conditions is lower than that (∼0.14–0.24) in previous studies. These results may be due to the fact that the plasmasphere expanded more frequently to the geosynchronous region under extremely quiet geomagnetic conditions in 2007–2008 than the periods selected in previous studies. The amplitude and frequency of He‐band EMIC waves for nonlinear wave growth are examined as changing cold plasma density at geosynchronous orbit. We confirm that the spectral properties of observed EMIC waves are in good agreement with the nonlinear theory.

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Estimation of pitch angle diffusion rates and precipitation time scales of electrons due to EMIC waves in a realistic field model

Cited by 18 publications

References 69 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

Effect of hot anisotropic He⁺ ions on the growth and damping of electromagnetic ion cyclotron waves in the inner magnetosphere

Spectral characteristics of steady quiet‐time EMIC waves observed at geosynchronous orbit

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Estimation of pitch angle diffusion rates and precipitation time scales of electrons due to EMIC waves in a realistic field model

Cited by 18 publications

References 69 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

Effect of hot anisotropic He+ ions on the growth and damping of electromagnetic ion cyclotron waves in the inner magnetosphere

Spectral characteristics of steady quiet‐time EMIC waves observed at geosynchronous orbit

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Effect of hot anisotropic He⁺ ions on the growth and damping of electromagnetic ion cyclotron waves in the inner magnetosphere