Radial diffusion simulations of the 20 September 2007 radiation belt dropout

Albert, J. M.

doi:10.5194/angeo-32-925-2014

Cited by 9 publications

(9 citation statements)

References 48 publications

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“…Rapid, large‐scale dropouts of radiation belt electrons, usually (though not only) seen during the main phase of storms, are not well understood. Both outward radial diffusion and precipitation due to pitch angle scattering by cyclotron‐resonant waves are frequently invoked, but as currently modeled, they seem insufficiently effective at L ∗ ∼4 or below and at energy below ∼1 MeV, respectively (Albert, ; Morley et al, ; Turner et al, ; Yu et al, ). Here L ∗ , or Roederer L , is the well‐known quantity corresponding to the third adiabatic invariant associated with azimuthal drift around the Earth.…”

Section: Introductionmentioning

confidence: 99%

Calculation of Last Closed Drift Shells for the 2013 GEM Radiation Belt Challenge Events

et al. 2018

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Radiation belt behavior is often analyzed in terms of adiabatic invariants, of which the third roughly characterizes the radial distance of particle drift shells. The outermost, or last closed drift shell, can be an important boundary for numerical modeling, especially for drift-averaged treatments such as three-dimensional diffusion codes. Here we discuss calculation of the last closed drift shell, using the widely used International Radiation Belt Environment Modeling (IRBEM) Library, the LanlGeoMag code, and a guiding center code named AFRL-Shell, in conjunction with a variety of current magnetic field models. We present results for the four events in 2013, comprising the radiation belt challenge organized by the Quantitative Assessment of Radiation Belt Modeling focus group of the Geospace Environment Modeling (GEM) program.

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Section: Introductionmentioning

confidence: 99%

Calculation of Last Closed Drift Shells for the 2013 GEM Radiation Belt Challenge Events

et al. 2018

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“…Parallel to the acceleration processes, there have been two dominant loss paradigms (Albert, ). One paradigm (Li et al, ) is the radial loss to the magnetopause (boundary of the magnetosphere).…”

Section: Introductionmentioning

confidence: 99%

Rapid Loss of Radiation Belt Relativistic Electrons by EMIC Waves

Gao

Zheng

et al. 2017

JGR Space Physics

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How relativistic electrons are lost is an important question surrounding the complex dynamics of the Earth's outer radiation belt. Radial loss to the magnetopause and local loss to the atmosphere are two main competing paradigms. Here on the basis of the analysis of a radiation belt storm event on 27 February 2014, we present new evidence for the electromagnetic ion cyclotron (EMIC) wave‐driven local precipitation loss of relativistic electrons in the heart of the outer radiation belt. During the main phase of this storm, the radial profile of relativistic electron phase space density was quasi‐monotonic, qualitatively inconsistent with the prediction of radial loss theory. The local loss at low L shells was required to prevent the development of phase space density peak resulting from the radial loss process at high L shells. The rapid loss of relativistic electrons in the heart of outer radiation belt was observed as a dip structure of the electron flux temporal profile closely related to intense EMIC waves. Our simulations further confirm that the observed EMIC waves within a quite limited longitudinal region were able to reduce the off‐equatorially mirroring relativistic electron fluxes by up to 2 orders of magnitude within about 1.5 h.

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“…The existence in the inner magnetosphere of rapid dropouts of almost whole populations of energetic electrons (with energies E ∼25–200 keV) is now well known [e.g., see Millan and Thorne , ; Morley et al , ; Turner et al , , , ; Albert , ; Gao et al , ; Hwang et al , , and references therein], as well as the disappearance in various situations of nearly equatorially mirroring energetic electrons, leading to the formation of so‐called butterfly distributions in equatorial pitch angle α 0 [e.g., see Gannon et al , ; Gu et al , ; Zhao et al , ]. Such rapid variations of the distribution of energetic electrons may have profound and direct mitigating consequences on internal charging hazards inside various spacecrafts [e.g., see Mulligan‐Skov et al , ; Tian et al , ].…”

Section: Introductionmentioning

confidence: 99%

“…And more specifically, how to solve the problem of nearly equatorially mirroring energetic electron scattering and loss? During storm periods of strong magnetic field perturbations and/or high L > 6 (with L McIlwain's number), drift shell splitting and enhanced outward radial diffusion up to the magnetopause can certainly operate [ Sibeck et al , ; Shprits et al , ; Kim et al , ; Albert , ; Turner et al , ]. Magnetopause shadowing may progressively entail losses at lower L , down to L ∼ 4, due to strong radial diffusion by ultralow frequency (ULF) waves in the presence of a steeply decreasing phase space density toward higher L [ Elkington et al , ; Shprits et al , ; Ukhorskiy et al , ].…”

Section: Introductionmentioning

confidence: 99%

“…Magnetopause shadowing may progressively entail losses at lower L , down to L ∼ 4, due to strong radial diffusion by ultralow frequency (ULF) waves in the presence of a steeply decreasing phase space density toward higher L [ Elkington et al , ; Shprits et al , ; Ukhorskiy et al , ]. However, during nonstorm times with weak magnetic disturbances at low L < 6, other mechanisms should likely take over [ Morley et al , ; Turner et al , ; Albert , ]. Worthy candidates are electromagnetic ion cyclotron (EMIC) waves, fast magnetosonic waves, or chorus whistler mode waves, which may transport particles to smaller pitch angles via resonant interactions, ultimately leading to their precipitation into the atmosphere [e.g., Shprits et al , ; Thorne , ].…”

Section: Introductionmentioning

confidence: 99%

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Equatorial electron loss by double resonance with oblique and parallel intense chorus waves

et al. 2016

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Puzzling satellite observations of butterfly pitch angle distributions and rapid dropouts of 30–150 keV electrons are widespread in the Earth's radiation belts. Several mechanisms have been proposed to explain these observations, such as enhanced outward radial diffusion combined with magnetopause shadowing or scattering by intense magnetosonic waves, but their effectiveness is mainly limited to storm times. Moreover, the scattering of 30–150 keV electrons via cyclotron resonance with intense parallel chorus waves should be limited to particles with equatorial pitch angle smaller than 70°–75°, leaving unaffected a large portion of the population. In this paper, we investigate the possible effects of oblique whistler mode waves, noting, in particular, that Landau resonance with very oblique waves can occur up to ∼89°. We demonstrate that such very oblique chorus waves with realistic amplitudes can very efficiently nonlinearly transport nearly equatorially mirroring electrons toward smaller pitch angles where nonlinear scattering (phase bunching) via cyclotron resonance with quasi‐parallel waves can take over and quickly send them to much lower pitch angles <40°. The proposed double resonance mechanism could therefore explain the formation of butterfly pitch angle distributions as well as contribute to some fast dropouts of 30–150 keV electrons occurring during moderate geomagnetic disturbances at L = 4–6. Since 30–150 keV electrons represent a seed population for a further acceleration to relativistic energies by intense parallel chorus waves during storms or substorms, the proposed mechanism may have important consequences on the dynamics of 100 keV to MeV electron fluxes in the radiation belts.

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Radial diffusion simulations of the 20 September 2007 radiation belt dropout

Cited by 9 publications

References 48 publications

Calculation of Last Closed Drift Shells for the 2013 GEM Radiation Belt Challenge Events

Calculation of Last Closed Drift Shells for the 2013 GEM Radiation Belt Challenge Events

Rapid Loss of Radiation Belt Relativistic Electrons by EMIC Waves

Equatorial electron loss by double resonance with oblique and parallel intense chorus waves

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