The controlling effect of ion temperature on EMIC wave excitation and scattering

Chen, Lunjin; Thorne, R. M.; Bortnik, J.

doi:10.1029/2011gl048653

Cited by 113 publications

(185 citation statements)

References 20 publications

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“…Hot ion effects (not considered here) may increase the minimum energy E min for cyclotron resonance with He band waves near F cHe , mitigating lifetime reduction in such cases [Chen et al, 2011]. Hot ion effects (not considered here) may increase the minimum energy E min for cyclotron resonance with He band waves near F cHe , mitigating lifetime reduction in such cases [Chen et al, 2011].…”

Section: Combined Effects Of Simultaneous Emic and Whistler Mode Wavementioning

confidence: 99%

Contemporaneous EMIC and whistler mode waves: Observations and consequences for MeV electron loss

Zhang

Mourenas

Artemyev

et al. 2017

Geophysical Research Letters

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The high variability of relativistic (MeV) electron fluxes in the Earth's radiation belts is partly controlled by loss processes involving resonant interactions with electromagnetic ion cyclotron (EMIC) and whistler mode waves. But as previous statistical models were generated independently for each wave mode, whether simultaneous electron scattering by the two wave types has global importance remains an open question. Using >3 years of simultaneous Van Allen Probes and THEMIS measurements, we explore the contemporaneous presence of EMIC and whistler mode waves in the same L shell, albeit at different local times, determining the distribution of wave and plasma parameters as a function of L, Kp, and AE. We derive electron lifetimes from observations and provide the first statistics of combined effects of EMIC and whistler mode wave scattering on MeV electrons as a function of L and geomagnetic activity. We show that MeV electron lifetimes are often strongly reduced by such combined scattering.

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Section: Combined Effects Of Simultaneous Emic and Whistler Mode Wavementioning

confidence: 99%

Contemporaneous EMIC and whistler mode waves: Observations and consequences for MeV electron loss

Zhang

Mourenas

Artemyev

et al. 2017

Geophysical Research Letters

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“…Our calculations are based upon the cold plasma theory, which, however, can break down when the hot proton and/or electron density becomes comparable to or even exceed the cold plasma density, which can be the case during the intensification of substorm injections [e.g., Chen et al, 2011;Silin et al, 2011]. Inclusion of thermal plasma effects can introduce large differences in the determination of resonant frequencies and resonant scattering rates as well.…”

Section: 1002/2015ja021466mentioning

confidence: 99%

Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales

et al. 2015

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To improve our understanding of the role of electromagnetic ion cyclotron (EMIC) waves in radiation belt electron dynamics, we perform a comprehensive analysis of EMIC wave‐induced resonant scattering of outer zone relativistic (>0.5 MeV) electrons and resultant electron loss time scales with respect to EMIC wave band, L shell, and wave normal angle model. The results demonstrate that while H+‐band EMIC waves dominate the scattering losses of ~1–4 MeV outer zone relativistic electrons, it is He+‐band and O+‐band waves that prevail over the pitch angle diffusion of ultrarelativistic electrons at higher energies. Given the wave amplitude, EMIC waves at higher L shells tend to resonantly interact with a larger population of outer zone relativistic electrons and drive their pitch angle scattering more efficiently. Obliquity of EMIC waves can reduce the efficiency of wave‐induced relativistic electron pitch angle scattering. Compared to the frequently adopted parallel or quasi‐parallel model, use of the latitudinally varying wave normal angle model produces the largest decrease in H+‐band EMIC wave scattering rates at pitch angles < ~40° for electrons > ~5 MeV. At a representative nominal amplitude of 1 nT, EMIC wave scattering produces the equilibrium state (i.e., the lowest normal mode under which electrons at the same energy but different pitch angles decay exponentially on the same time scale) of outer belt relativistic electrons within several to tens of minutes and the following exponential decay extending to higher pitch angles on time scales from <1 min to ~1 h. The electron loss cone can be either empty as a result of the weak diffusion or heavily/fully filled due to approaching the strong diffusion limit, while the trapped electron population at high pitch angles close to 90° remains intact because of no resonant scattering. In this manner, EMIC wave scattering has the potential to deepen the anisotropic distribution of outer zone relativistic electrons by reshaping their pitch angle profiles to “top‐hat.” Overall, H+‐band and He+‐band EMIC waves are most efficient in producing the pitch angle scattering loss of relativistic electrons at ~1–2 MeV. In contrast, the presence of O+‐band EMIC waves, while at a smaller occurrence rate, can dominate the scattering loss of 5–10 MeV electrons in the entire region of the outer zone, which should be considered in future modeling of the outer zone relativistic electron dynamics.

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“…3. Cold plasma density: Since the wave power is centered well below the He + gyrofrequency, the finite beta effect is ignorable [Chen et al, 2011[Chen et al, , 2013 and the cold wave dispersion relation is used in computing the diffusion coefficient. Since GOES 13 does not provide plasma density observations, we calculate the plasma density using the upper hybrid resonance (UHR) frequency provided by the Electric and Magnetic Field Instrument and Integrated Science (EMFISIS) [Kletzing et al, 2013] on the Van Allen Probes.…”

Section: 1002/2014gl062273mentioning

confidence: 99%

Investigation of EMIC wave scattering as the cause for the BARREL 17 January 2013 relativistic electron precipitation event: A quantitative comparison of simulation with observations

Millan

Hudson

et al. 2014

Geophysical Research Letters

136

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Electromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) balloons and was magnetically mapped close to Geostationary Operational Environmental Satellite (GOES) 13. We simulate the relativistic electron pitch angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES 13 and the Van Allen Probes. We show that the count rate, the energy distribution, and the time variation of the simulated precipitation all agree very well with the balloon observations, suggesting that EMIC wave scattering was likely the cause for the precipitation event. The event reported here is the first balloon REP event with closely conjugate EMIC wave observations, and our study employs the most detailed quantitative analysis on the link of EMIC waves with observed REP to date.

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The controlling effect of ion temperature on EMIC wave excitation and scattering

Cited by 113 publications

References 20 publications

Contemporaneous EMIC and whistler mode waves: Observations and consequences for MeV electron loss

Contemporaneous EMIC and whistler mode waves: Observations and consequences for MeV electron loss

Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales

Investigation of EMIC wave scattering as the cause for the BARREL 17 January 2013 relativistic electron precipitation event: A quantitative comparison of simulation with observations

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