The Importance of Ion Composition for Radiation Belt Modeling

Ross, John P.; Glauert, S. A.; Horne, Richard B.; Meredith, Nigel P.

doi:10.1029/2022ja030680

Cited by 6 publications

(15 citation statements)

References 56 publications

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“…The results presented in this study could be a general reference for works on the cold ion populations. Although some of our results are consistent with previous findings (e.g., Ross et al., 2022), we can only get limited results about the cold ion populations and the ion compositions due to the small data set of the cold ion density comparable to the total electron density and the possible contaminations of helium and oxygen ion densities from cold protons. Further observational and simulation studies are desired to confirm the results presented in this study.…”

Section: Discussionsupporting

confidence: 89%

“…In addition, Ross et al. (2022) emphasized the importance of ion composition on the decay of relativistic electron fluxes in the radiation belts by EMIC waves through kinetic simulations. They found that the radiation belt electron decay agrees better with Van Allen Probes observation when the helium fraction is only a few percent.…”

Section: Discussionmentioning

confidence: 99%

“…Since the cold ions in the inner magnetosphere mainly originate from the ionosphere where O + outflow is frequently observed (e.g., Hull et al, 2019;, we may expect that there are more O + ions than He + ions. In addition, Ross et al (2022) emphasized the importance of ion composition on the decay of relativistic electron fluxes in the radiation belts by EMIC waves through kinetic simulations. They found that the radiation belt electron decay agrees better with Van Allen Probes observation when the helium fraction is only a few percent.…”

Section: Discussionmentioning

confidence: 99%

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The Densities and Compositions of Background Cold Ions Based on the Van Allen Probe Observations

Yue

Kistler

et al. 2023

Geophysical Research Letters

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The cold ions, which are generally “invisible” to most instruments, have strong impacts on plasma wave and magnetic reconnection. Under particular situations, these cold ions could be accelerated and thus become detectable. In this study, we statistically investigated the properties of background cold ions based on Van Allen Probe observations. The cold ions could often be detected near the dusk sector, and a clear dawn‐dusk asymmetry is observed for all ion species with higher density at the dusk side, showing plasmaspheric plume‐like structures. Similar to the cold electrons, cold proton ions show a clear boundary of plasmapause with its location moving toward the Earth as geomagnetic activity increases. Furthermore, the percentage of oxygen increases, and the percentage of protons decreases as geomagnetic activity increases whereas the helium composition is generally small. Our results provide important information on ion compositions for the understanding of cold‐plasma dynamics in the inner magnetosphere.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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The Densities and Compositions of Background Cold Ions Based on the Van Allen Probe Observations

Yue

Kistler

et al. 2023

Geophysical Research Letters

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“…(2015) of the early Van Allen Probes era (2012–2014) suggest that O+ EMIC waves are found generally in the outer plasmasphere and occasionally the plasma trough which is the region in which this loss process is observed. In this region the O+ density can be higher than the partial ion compositions used here, thus increasing the strength of O+ band EMIC waves (e.g., Nosé et al., 2020; Ross et al., 2022). A study of Van Allen Probes data from 2012 to 2017 by H. Chen et al.…”

Section: Discussionmentioning

confidence: 85%

“…(2003) as used in our analysis presented here, have been used as limiting cases and storm time conditions for study of the sensitivity of minimum resonant energies and diffusion coefficients for ultrarelativistic electrons by Ross et al. (2022). The composition of Kersten et al.…”

Section: Discussionmentioning

confidence: 99%

On the Dynamics of Ultrarelativistic Electrons (>2 MeV) Near L* = 3.5 During 8 June 2015

Hogan,

Li,

Xiang

et al. 2023

JGR Space Physics

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Understanding local loss processes in Earth’s radiation belts is critical to understanding their overall structure. Electromagnetic ion cyclotron waves can cause rapid loss of multi‐MeV electrons in the radiation belts. These loss effects have been observed at a range of L* values, recently as low as L* = 3.5. Here, we present a case study of an event where a local minimum develops in multi‐MeV electron phase space density (PSD) near L* = 3.5 and evaluate the possibility of electromagnetic ion cyclotron (EMIC) waves in contributing to the observed loss feature. Signatures of EMIC waves are shown including rapid local loss and pitch angle bite outs. Analysis of the wave power spectral density during the event shows EMIC wave occurrence at higher L* values. Using representative wave parameters, we calculate minimum resonant energies, diffusion coefficients, and simulate the evolution of electron PSD during this event. From these results, we find that O+ band EMIC waves could be contributing to the local loss feature during this event. O+ band EMIC waves are uncommon, but do occur in these L* ranges, and therefore may be a significant driver of radiation belt dynamics under certain preconditioning of the radiation belts.

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Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

et al. 2023

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We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data collected by the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at >0.5 MeV which are abrupt (bursty) (lasting ∼17 s, or $\Delta L\sim 0.56$ Δ L ∼ 0.56 ) with significant substructure (occasionally down to sub-second timescale). We attribute the bursty nature of the precipitation to the spatial extent and structuredness of the wave field at the equator. Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Case studies employing conjugate ground-based or equatorial observations of the EMIC waves reveal that the energy of moderate and strong precipitation at ELFIN approximately agrees with theoretical expectations for cyclotron resonant interactions in a cold plasma. Using multiple years of ELFIN data uniformly distributed in local time, we assemble a statistical database of ∼50 events of strong EMIC wave-driven precipitation. Most reside at $L\sim 5-7$ L ∼ 5 − 7 at dusk, while a smaller subset exists at $L\sim 8-12$ L ∼ 8 − 12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an $L$ L -shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio’s spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of $\sim 1.45$ ∼ 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. It should be noted though that this diffusive treatment likely includes effects from nonlinear resonant interactions (especially at high energies) and nonresonant effects from sharp wave packet edges (at low energies). Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven >1 MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to ∼ 200-300 keV by much less intense higher frequency EMIC waves at dusk (where such waves are most frequent). At ∼100 keV, whistler-mode chorus may be implicated in concurrent precipitation. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.

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The Importance of Ion Composition for Radiation Belt Modeling

Cited by 6 publications

References 56 publications

The Densities and Compositions of Background Cold Ions Based on the Van Allen Probe Observations

The Densities and Compositions of Background Cold Ions Based on the Van Allen Probe Observations

On the Dynamics of Ultrarelativistic Electrons (>2 MeV) Near L* = 3.5 During 8 June 2015

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

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