Simulation of the outer radiation belt electrons near geosynchronous orbit including both radial diffusion and resonant interaction with Whistler‐mode chorus waves

Varotsou, Athena; Böscher, D.; Bourdarie, S.; Horne, Richard B.; Glauert, S. A.; Meredith, Nigel P.

doi:10.1029/2005gl023282

Cited by 138 publications

(193 citation statements)

References 24 publications

(32 reference statements)

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“…Possible candidates for these model trends are most likely waveparticle interactions (whistler chorus, hiss, electromagnetic ion cyclotron waves, etc.) which are also being studied by other modeling and data analysis efforts [Horne and Thorne, 1998;Meredith et al, 2002;Summers, 2005;Varotsou et al, 2005;Shprits et al, 2005;Green and Kivelson, 2004].…”

Section: Estimating the Missing Source/lossmentioning

confidence: 99%

Identifying the radiation belt source region by data assimilation

et al. 2007

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[1] We describe how assimilation of radiation belt data with a simple radial diffusion code can be used to identify and adjust for unknown physics in the model. We study the dropout and the following enhancement of relativistic electrons during a moderate storm on 25 October 2002. We introduce a technique that uses an ensemble Kalman filter and the probability distribution of the forecast ensemble to identify if the model is drifting away from the observations and to find inconsistencies between model forecast and observations. We use the method to pinpoint the time periods and locations where most of the disagreement occurs and how much the Kalman filter has to adjust the model state to match the observations. Although the model does not contain explicit source or loss terms, the Kalman filter algorithm can implicitly add very localized sources or losses in order to reduce the discrepancy between model and observations. We use this technique with multisatellite observations to determine when simple radial diffusion is inconsistent with the observed phase space densities indicating where additional source (acceleration) or loss (precipitation) processes must be active. We find that the outer boundary estimated by the ensemble Kalman filter is consistent with negative phase space density gradients in the outer electron radiation belt. We also identify specific regions in the radiation belts (L* % 5-6 and to a minor extend also L* % 4) where simple radial diffusion fails to adequately capture the variability of the observations, suggesting local acceleration/loss mechanisms.

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Section: Estimating the Missing Source/lossmentioning

confidence: 99%

Identifying the radiation belt source region by data assimilation

et al. 2007

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“…It is therefore necessary to use an approximation. One of the most widely used approximations is quasi-linear theory, which has been used extensively in radiation belt models at the Earth (e.g., Varotsou et al, 2005Varotsou et al, , 2008Albert et al, 2009;Shprits et al, 2009a, b;Fok et al, 2008;Su et al, 2010). Quasi-linear theory does not include phase trapping or phase bunching of electrons but assumes a broad band of waves and uses the time-averaged wave power.…”

Section: Calculating Diffusion Coefficientsmentioning

confidence: 99%

Electron acceleration at Jupiter: input from cyclotron-resonant interaction with whistler-mode chorus waves

et al. 2013

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Abstract. Jupiter has the most intense radiation belts of all the outer planets. It is not yet known how electrons can be accelerated to energies of 10 MeV or more. It has been suggested that cyclotron-resonant wave-particle interactions by chorus waves could accelerate electrons to a few MeV near the orbit of Io. Here we use the chorus wave intensities observed by the Galileo spacecraft to calculate the changes in electron flux as a result of pitch angle and energy diffusion. We show that, when the bandwidth of the waves and its variation with L are taken into account, pitch angle and energy diffusion due to chorus waves is a factor of 8 larger at Lshells greater than 10 than previously shown. We have used the latitudinal wave intensity profile from Galileo data to model the time evolution of the electron flux using the British Antarctic Survey Radiation Belt (BAS) model. This profile confines intense chorus waves near the magnetic equator with a peak intensity at ∼ 5 • latitude. Electron fluxes in the BAS model increase by an order of magnitude for energies around 3 MeV. Extending our results to L = 14 shows that cyclotron-resonant interactions with chorus waves are equally important for electron acceleration beyond L = 10. These results suggest that there is significant electron acceleration by cyclotron-resonant interactions at Jupiter contributing to the creation of Jupiter's radiation belts and also increasing the range of L-shells over which this mechanism should be considered.

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“…It is generally 45 understood that the belt dynamics arise from a delicate balance between acceleration, transport, 46 and loss 4 , with some recent modern studies highlighting a potential importance for high 47 frequency wave-particle interactions 5, 6 over traditional radial transport 7 or ultra-low frequency 48 (ULF) wave-particle resonance 8 for relativistic electron acceleration in the inner 49 magnetosphere 9 . Concerning loss, in the main phase of geomagnetic storms, a puzzling and 50 poorly understood rapid loss is often observed deep in the heart of the radiation belt, see e.g., the 51 review by Turner et al 10 , followed by a replenishment of relativistic electron flux in the form of Explaining the enigmatic third radiation belt requires electrons to be rapidly lost in the main 59 phase of geomagnetic storms, either by rapid scattering into the atmosphere by high frequency 60 plasma wave-particle interactions, or alternatively through rapid loss out through the 61 magnetopause in a process termed magnetopause shadowing 12 .…”

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confidence: 99%