Empirically Estimated Electron Lifetimes in the Earth's Radiation Belts: Van Allen Probe Observations

Claudepierre, S. G.; Bortnik, J.; O’Brien, T. P.; Fennell, J. F.; Blake, J. B.

doi:10.1029/2019gl086053

Cited by 38 publications

(93 citation statements)

References 25 publications

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“…The lifetimes are calculated using Equation 5 of Ni et al (2013). These lifetime values are comparable to previous results calculated in theory (e.g., Abel & Thorne, 1998; Albert et al, 2020; Claudepierre et al, 2020b; Mourenas et al, 2017; Ross et al, 2019) and inferred from observations (Claudepierre et al, 2020a; Ripoll et al, 2014). The lifetime of the electron flux due to collision + hiss + LGW is much shorter than that due to collision + hiss because the deep minimum of < D αα > at PA = [65°, 85°] from hiss waves is significantly filled by LGW waves (Figure 2e).…”

Section: Comparisons Between Simulations and Observationssupporting

confidence: 91%

“…This model contains the azimuthal drift effect, PA diffusion induced by various plasma waves, and a CRAND source. Recently, the scattering effects of different waves on electrons in the slot region have been a topic of active research (Albert et al, 2016(Albert et al, , 2020Claudepierre et al, 2020aClaudepierre et al, , 2020bRoss et al, 2019). The wave models in these studies are mostly empirical, and their calculated results showed limited quantitative comparisons with specific satellite measurements during extend quiet times.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of Energetic Electrons in the Slot Region During Geomagnetically Quiet Times: Losses Due to Wave‐Particle Interactions Versus a Source From Cosmic Ray Albedo Neutron Decay (CRAND)

Xiang

et al. 2020

JGR Space Physics

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Earth's slot region, lying between the outer and inner radiation belts, has been identified as due to a balance between inward radial diffusion and pitch angle (PA) scattering induced by waves. However, recent satellite observations and modeling studies indicate that cosmic ray albedo neutron decay (CRAND) may also play a significant role in energetic electron dynamics in the slot region. In this study, using a drift-diffusion-source model, we investigate the relative contribution of all significant waves and CRAND to the dynamics of energetic electrons in the slot region during July 2014, an extended period of quiet geomagnetic activity. The bounce-averaged PA diffusion coefficients from three types of waves (hiss, lightning-generated whistlers [LGW], and very low frequency [VLF] transmitters) are calculated based on quasi-linear theory, while the CRAND source follows the results in Xiang et al. (2019, https://doi.org/ 10.1029/2018GL081730). The simulation results indicate that both LGW and VLF transmitter waves can enhance loss and weaken the top hat PA distribution induced by hiss waves. For 470 keV electrons at L ¼ 2.5, simulation results without CRAND show a much quicker decrease than observations from the Van Allen Probes. After including CRAND, simulated electron flux variations reproduce satellite observations, suggesting that CRAND is an important source for hundreds of keV electrons in the slot region during quiet times. The balance between the CRAND source and loss due to wave-particle interactions provides a lower limit to relativistic electron fluxes in the slot region, which can act as an important reference point for instrument calibration when a true background level is warranted.

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Section: Comparisons Between Simulations and Observationssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Dynamics of Energetic Electrons in the Slot Region During Geomagnetically Quiet Times: Losses Due to Wave‐Particle Interactions Versus a Source From Cosmic Ray Albedo Neutron Decay (CRAND)

Xiang

et al. 2020

JGR Space Physics

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“…Many studies have been devoted to calculate electron lifetimes throughout the radiation belts (Albert & Shprits, 2009; Baker et al., 2013; Claudepierre et al., 2020; Fennell et al., 2013; Meredith et al., 2002). Precise calculations of electron lifetimes are crucial for accurately modeling and forecasting the global dynamics of the outer radiation belt and for providing a comprehensive description of electron flux variations over a wide energy range.…”

Section: Discussionmentioning

confidence: 99%

Outer Radiation Belt Electron Lifetime Model Based on Combined Van Allen Probes and Cluster VLF Measurements

et al. 2020

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The flux of energetic electrons in the outer radiation belt shows a high variability. The interactions of electrons with very low frequency (VLF) chorus waves play a significant role in controlling the flux variation of these particles. Quantifying the effects of these interactions is crucially important for accurately modeling the global dynamics of the outer radiation belt and to provide a comprehensive description of electron flux variations over a wide energy range (from the source population of 30 keV electrons up to the relativistic core population of the outer radiation belt). Here, we use a synthetic chorus wave model based on a combined database compiled from the Van Allen Probes and Cluster spacecraft VLF measurements to develop a comprehensive parametric model of electron lifetimes as a function of L‐shell, electron energy, and geomagnetic activity. The wave model takes into account the wave amplitude dependence on geomagnetic latitude, wave normal angle distribution, and variations of wave frequency with latitude. We provide general analytical formulas to estimate electron lifetimes as a function of L‐shell (for L = 3.0 to L = 6.5), electron energy (from 30 keV to 2 MeV), and geomagnetic activity parameterized by the AE index. The present model lifetimes are compared to previous studies and analytical results and also show a good agreement with measured lifetimes of 30 to 300 keV electrons at geosynchronous orbit.

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“…Relativistic electron fluxes can be increased by several orders of magnitude (Baker et al, 1994; Reeves et al, 2003) on the timescale of hours to days and can pose a risk to satellite instrumentation (Wrenn et al, 2002). These fluxes then decay on timescales of 5–10 days (Claudepierre et al, 2020; Meredith et al, 2006), and it is believed that their removal is strongly influenced by pitch angle diffusion by electromagnetic ion cyclotron (EMIC) waves (Albert, 2003; Horne & Thorne, 1998). Coincident observations of EMIC waves and relativistic electron precipitation support the idea that EMIC waves are influential at scattering MeV electrons (Miyoshi et al, 2008; Rodger et al, 2008; Usanova et al, 2014; Yuan et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

A New Approach to Constructing Models of Electron Diffusion by EMIC Waves in the Radiation Belts

Ross

Glauert

Horne

et al. 2020

Geophysical Research Letters

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Electromagnetic ion cyclotron (EMIC) waves play an important role in relativistic electron losses in the radiation belts through diffusion via resonant wave-particle interactions. We present a new approach for calculating bounce and drift-averaged EMIC electron diffusion coefficients. We calculate bounce-averaged diffusion coefficients, using quasi-linear theory, for each individual Combined Release and Radiation Effects Satellite (CRRES) EMIC wave observation using fitted wave properties, the plasma density and the background magnetic field. These calculations are then combined into bounce-averaged diffusion coefficients. The resulting coefficients therefore capture the combined effects of individual spectra and plasma properties as opposed to previous approaches that use average spectral and plasma properties, resulting in diffusion over a wider range of energies and pitch angles. These calculations, and their role in radiation belt simulations, are then compared against existing diffusion models. The new diffusion coefficients are found to significantly improve the agreement between the calculated decay of relativistic electrons and Van Allen Probes data. Plain Language Summary In recent years there have been an increasing number of satellites operating in or traversing the Earth's radiation belts. These belts are composed of charged particles that are largely confined by the Earth's magnetic field, although waves can accelerate and scatter these particles. In the outer belt, electrons can be accelerated up to relativistic energies and pose a threat to satellites. Diffusion-based models are used to simulate the electron population, incorporating the statistical effects of waves on the electrons. Electromagnetic ion cyclotron waves are of particular importance for the relativistic population, effectively scattering them into the atmosphere and removing them from the belts. Previous models of this interaction are based on average plasma and wave observations; however, these do not well represent the range of interactions possible. Here we take a new approach, considering each observation individually to determine their statistical effect. When included into diffusion models, this new approach significantly improves the modeling of the relativistic electron population.

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Empirically Estimated Electron Lifetimes in the Earth's Radiation Belts: Van Allen Probe Observations

Cited by 38 publications

References 25 publications

Dynamics of Energetic Electrons in the Slot Region During Geomagnetically Quiet Times: Losses Due to Wave‐Particle Interactions Versus a Source From Cosmic Ray Albedo Neutron Decay (CRAND)

Dynamics of Energetic Electrons in the Slot Region During Geomagnetically Quiet Times: Losses Due to Wave‐Particle Interactions Versus a Source From Cosmic Ray Albedo Neutron Decay (CRAND)

Outer Radiation Belt Electron Lifetime Model Based on Combined Van Allen Probes and Cluster VLF Measurements

A New Approach to Constructing Models of Electron Diffusion by EMIC Waves in the Radiation Belts

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