Using MEPED observations to infer plasma density and chorus intensity in the radiation belts

Longley, William; Chan, A. A.; Jaynes, A. N.; Elkington, S. R.; Pettit, Joshua; Ross, Johnathan P. J.; Glauert, S. A.; Horne, Richard B.

doi:10.3389/fspas.2022.1063329

Cited by 6 publications

(3 citation statements)

References 29 publications

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“…These coefficients are calculated using quasilinear theory, with the chorus wave intensity estimated from National Oceanic and Atmospheric Administration (NOAA) Polar Orbiting Environmental Satellites (POES) measurements of precipitating and trapped electron fluxes using the method in and Ni et al (2014). The diffusion coefficients used in this study do not include the effects of a changing ω pe /ω ce ratio, which can substantially affect the wave power estimated from POES observations (Longley et al, 2022). The set of coefficients in Ma et al (2018) are calculated separately for upper and lower band chorus with Gaussian frequency and wave normal angle distributions in each band.…”

Section: Chorus Wave Diffusion Coefficientsmentioning

confidence: 99%

Simulation of radiation belt wave-particle interactions in an MHD-particle framework

Chan,

Elkington,

Longley

et al. 2023

Front. Astron. Space Sci.

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In this paper we describe K2, a comprehensive simulation model of Earth’s radiation belts that includes a wide range of relevant physical processes. Global MHD simulations are combined with guiding-center test-particle methods to model interactions with ultra low-frequency (ULF) waves, substorm injections, convective transport, drift-shell splitting, drift-orbit bifurcations, and magnetopause shadowing, all in self-consistent MHD fields. Simulation of local acceleration and pitch-angle scattering due to cyclotron-scale interactions is incorporated by including stochastic differential equation (SDE) methods in the MHD-particle framework. The SDEs are driven by event-specific bounce-averaged energy and pitch-angle diffusion coefficients. We present simulations of electron phase-space densities during a simplified particle acceleration event based on the 17 March 2013 event observed by the Van Allen Probes, with a focus on demonstrating the capabilities of the K2 model. The relative wave-particle effects of global scale ULF waves and very-low frequency (VLF) whistler-mode chorus waves are compared, and we show that the primary acceleration appears to be from the latter. We also show that the enhancement with both ULF and VLF processes included exceeds that of VLF waves alone, indicating a synergistic combination of energization and transport processes may be important.

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Section: Chorus Wave Diffusion Coefficientsmentioning

confidence: 99%

Simulation of radiation belt wave-particle interactions in an MHD-particle framework

Chan,

Elkington,

Longley

et al. 2023

Front. Astron. Space Sci.

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“…We see a clear improvement in our results, for both >30 keV (black crosses) and >100 keV (blue triangles) energy channels when we decrease the plasma density used in the calculation of the chorus-driven diffusion caused precipitation. This suggests the density used within the BAS model may be too high; similarly, Longley et al (2022) used the ratio between the precipitating and trapped flux observed by POES on 17 March 2013 to infer a generally lower plasma density than used in BAS-RBM. The next improvement in correlation values seen in Figure 13 comes from using solely RBSP data (as opposed to the averaging approach employing the entire BAS wave data base) to calculate the diffusion coefficients, almost doubling the correlation coefficient for the higher energy channel from 0.25 to 0.46.…”

Section: Discussionmentioning

confidence: 99%

Characterizing Radiation‐Belt Energetic Electron Precipitation Spectra: A Comparison of Quasi‐Linear Diffusion Theory With In Situ Measurements

Reidy,

Horne,

Glauert

et al. 2024

JGR Space Physics

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High energy electron precipitation from the Earth's radiation belts is important for loss from the radiation belts and atmospheric chemistry. We follow up investigations presented in Reidy et al. (2021, https://doi.org/10.1029/2020ja028410) where precipitating flux is calculated inside the field of view of the POES T0 detector using quasi‐linear theory and pitch angle diffusion coefficients (Dαα) from the British Antarctic Survey (BAS). These results showed good agreements at >30 keV for L* >5 on the dawnside but the flux were too low at higher energies. We have investigated the effect of changing parameters in the calculation of the precipitating flux to improve the results for the higher energies using comparisons of in situ flux and cold plasma measurements from GOES‐15 and RBSP. We find that the strength of the diffusion coefficients rather than the shape of the source spectrum has the biggest effect on the calculated precipitation. In particular we find decreasing the cold plasma density used in the calculation of Dαα increases the diffusion and hence the precipitation at the loss cone for the higher energies, improving our results. The method of calculating Dαα is also examined, comparing co‐located rather than averaged RBSP measurements. We find that the method itself has minimal effect but using RBSP derived Dαα improved our results over using Dαα calculated using the entire BAS wave data base; this is potentially due to better measurements of the cold plasma density from RBSP than the other spacecraft included in the BAS wave data base (e.g., THEMIS).

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“…However, the bounce-averaged diffusion coefficients used in Chan et al (2023), were computed using a dipolar magnetic field and a static density distribution. The diffusion coefficients, therefore, did not exhibit a realistic variability due to either the storm-time magnetic field or the cold plasma density, which can significantly affect both the estimated wave power (Longley et al, 2022) and the characteristics of the wave-particle interactions themselves (e.g., Kennel & Petschek, 1966).…”

Section: Introductionmentioning

confidence: 99%

Cross‐Scale Modeling of Storm‐Time Radiation Belt Variability

Michael,

Sorathia,

Ukhorskiy

et al. 2024

JGR Space Physics

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During geomagnetic storms relativistic outer radiation belt electron flux exhibits large variations on rapid time scales of minutes to days. Many competing acceleration and loss processes contribute to the dynamic variability of the radiation belts; however, distinguishing the relative contribution of each mechanism remains a major challenge as they often occur simultaneously and over a wide range of spatiotemporal scales. In this study, we develop a new comprehensive model for storm‐time radiation belt dynamics by incorporating electron wave‐particle interactions with parallel propagating whistler mode waves into our global test‐particle model of the outer belt. Electron trajectories are evolved through the electromagnetic fields generated from the Multiscale Atmosphere‐Geospace Environment (MAGE) global geospace model. Pitch angle scattering and energization of the test particles are derived from analytical expressions for quasi‐linear diffusion coefficients that depend directly on the magnetic field and density from the magnetosphere simulation. Using a study of the 17 March 2013 geomagnetic storm, we demonstrate that resonance with lower band chorus waves can produce rapid relativistic flux enhancements during the main phase of the storm. While electron loss from the outer radiation belt is dominated by loss through the magnetopause, wave‐particle interactions drive significant atmospheric precipitation. We also show that the storm‐time magnetic field and cold plasma density evolution produces strong, local variations of the magnitude and energy of the wave‐particle interactions and is critical to fully capturing the dynamic variability of the radiation belts caused by wave‐particle interactions.

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Using MEPED observations to infer plasma density and chorus intensity in the radiation belts

Cited by 6 publications

References 29 publications

Simulation of radiation belt wave-particle interactions in an MHD-particle framework

Simulation of radiation belt wave-particle interactions in an MHD-particle framework

Characterizing Radiation‐Belt Energetic Electron Precipitation Spectra: A Comparison of Quasi‐Linear Diffusion Theory With In Situ Measurements

Cross‐Scale Modeling of Storm‐Time Radiation Belt Variability

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