High‐energy radiation belt electrons from CRAND

Selesnick, R. S.

doi:10.1002/2014ja020963

Cited by 29 publications

(37 citation statements)

References 24 publications

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“…Since neutron decay is well understood, its known properties enable evaluation of its contribution. In the neutron rest frame, electrons produced by neutron decay have a beta decay spectrum:

ψ ((), E) = normalC \sqrt{E ((), E + 2 m_{e} c^{2})} ((), E + m_{e} c^{2}) {(Q - E)}^{2}

where E is electron kinetic energy, Q is the maximum available energy for electrons due to the mass difference ( Q = m n c 2 − m p c 2 − m e c 2 =782 keV), and C is a constant ( C = 17.57 MeV −5 when ∫Ψd E = 1; Selesnick, ). Albedo neutrons below 1 eV have been determined to be responsible for the majority of the energetic electrons of interest (Hess et al, ; Lenchek et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…Albedo neutrons below 1 eV have been determined to be responsible for the majority of the energetic electrons of interest (Hess et al, ; Lenchek et al, ). Therefore, we need only to consider neutrons at rest (also discussed in Hess et al, , and Selesnick, ). We can calculate the fluxes of the CRAND‐produced electrons at different energies with lifetime τ e (Li et al, ):

J ((), E) = n \frac{τ_{normale}}{τ_{n}} \frac{v ((), E) normalΨ ((), E)}{4 π}

where J is the electron flux, n is the neutron density, τ n is the neutron lifetime, and v is the electron velocity.…”

Section: Methodsmentioning

confidence: 99%

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Cosmic Ray Albedo Neutron Decay (CRAND) as a Source of Inner Belt Electrons: Energy Spectrum Study

Zhang

Zhao

et al. 2019

Geophysical Research Letters

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Cosmic Ray Albedo Neutron Decay (CRAND) has been recently confirmed as a source of energetic electrons at the inner edge of the inner belt by the Colorado Student Space Weather Experiment (CSSWE) mission. Here we use observations from the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) mission, to investigate the CRAND contribution to inner belt electrons quantitatively over a broad energy range (~100–800 keV). Spectral fitting analysis supports the conclusion that CRAND is the most important electron source at the inner edge of the inner belt. For the first time, we show that CRAND is the dominant source of >250‐keV quasitrapped electrons throughout the inner belt and slot region during quiet times. We suggest that additional sources for <250‐keV electrons exist, perhaps from inward transport. In contrast, dynamics of electrons in the inner belt and slot region is dominated by injections during active times.

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“…Since neutron decay is well understood, its known properties enable evaluation of its contribution. In the neutron rest frame, electrons produced by neutron decay have a beta decay spectrum:

ψ ((), E) = normalC \sqrt{E ((), E + 2 m_{e} c^{2})} ((), E + m_{e} c^{2}) {(Q - E)}^{2}

Section: Methodsmentioning

confidence: 99%

J ((), E) = n \frac{τ_{normale}}{τ_{n}} \frac{v ((), E) normalΨ ((), E)}{4 π}

where J is the electron flux, n is the neutron density, τ n is the neutron lifetime, and v is the electron velocity.…”

Section: Methodsmentioning

confidence: 99%

Cosmic Ray Albedo Neutron Decay (CRAND) as a Source of Inner Belt Electrons: Energy Spectrum Study

Zhang

Zhao

et al. 2019

Geophysical Research Letters

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“…Modern physical models of the electron radiation belts allow for radial diffusion, pitch angle scattering, and energy diffusion, where the latter is usually described as momentum diffusion [ Albert et al , ; Xiao et al , ; Su et al , ; Subbotin and Shprits , ; Tu et al , ; Glauert et al , ]. A typical expression for the gyrobounce drift phase‐averaged PSD ( f ) is

\begin{matrix} \frac{\partial f}{\partial t} = L^{2} {(|, \frac{\partial}{\partial L})}_{M, K} [\frac{D_{L L}}{L^{2}} {(|, \frac{\partial f}{\partial L})}_{M, K}] + \frac{1}{p^{2}} {(|, \frac{\partial}{\partial p})}_{x, L} [p^{2} D_{p p} {(|, \frac{\partial f}{\partial p})}_{x, L} + p^{2} D_{p x} {(|, \frac{\partial f}{\partial x})}_{p, L}] \\ + \frac{1}{x T (y)} {(|, \frac{\partial}{\partial x})}_{p, L} [x T (y) D_{x x} {(|, \frac{\partial f}{\partial x})}_{p, L} + x T (y) D_{x p} {(|, \frac{\partial f}{\partial p})}_{x, L}] + S \end{matrix}

where x is the cosine of the equatorial pitch angle, T ( y ) is a scale factor related to the particle's bounce period, the D s represent diffusion processes, and S represents a source, namely, cosmic ray albedo neutron decay (CRAND) [see, e.g., Selesnick , , and references therein].…”

Section: Analysis Approachmentioning

confidence: 99%

Inner zone and slot electron radial diffusion revisited

O’Brien

Claudepierre

Guild

et al. 2016

Geophysical Research Letters

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Using recent data from NASA's Van Allen Probes, we estimate the quiet time radial diffusion coefficients for electrons in the inner radiation belt (L < 3) with energies from ~50 to 750 keV. The observations are consistent with dynamics dominated by pitch angle scattering and radial diffusion. We use a coordinate system in which these two modes of diffusion are separable. Then we integrate phase space density over pitch angle to obtain a “bundle content” that is invariant to pitch angle scattering, except for atmospheric loss. We estimate the effective radial diffusion coefficient from the temporal and radial variation of the bundle content. We show that our diffusion coefficients agree well with previously determined values obtained in the 1960s and 1970s and follow the form one expects for radial diffusion caused by exponentially decaying impulses in the large‐scale electrostatic potential.

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“…They also showed that there were essentially no (or very few) E > 1 MeV electrons present, at least in the early Van Allen Probes mission time frame. Selesnick (2015) showed that the neutron albedo generated electron fluxes are too low to account for the observed E < 1 MeV inner zone electrons, indicating that a different source was responsible for the inner zone electron fluxes. However, his calculations also indicated that the process could generate multi-MeV electrons at low flux levels, below the upper limits set by the Van Allen Probe measurements.…”

Section: Inner Zone Electronsmentioning

confidence: 98%

Space Weather Effects in the Earth’s Radiation Belts

et al. 2017

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The first major scientific discovery of the Space Age was that the Earth is enshrouded in toroids, or belts, of very high-energy magnetically trapped charged particles. Early observations of the radiation environment clearly indicated that the Van Allen belts could be delineated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. The energy distribution, spatial extent and particle species makeup of the Van Allen belts has been subsequently explored by several space missions. Recent observations by the NASA dual-spacecraft Van Allen Probes mission have revealed many novel properties of the radiation belts, especially for electrons at highly relativistic and ultra-relativistic kinetic energies. In this review we summarize the space weather impacts of the radiation belts. We demonstrate that many remarkable features of energetic particle changes are driven by strong solar and solar wind forcings. Recent comprehensive data show broadly and in many ways how high energy particles are accelerated, transported, and lost in the magnetosphere due to interplanetary shock wave interactions, coronal mass ejection impacts, and high-speed solar wind streams. We also discuss how radiation belt particles are intimately tied to other parts of the geospace system through atmosphere, ionosphere, and plasmasphere coupling. The new data have in many ways rewritten the textbooks about the radiation belts as a key space weather threat to human technological systems.

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High‐energy radiation belt electrons from CRAND

Cited by 29 publications

References 24 publications

Cosmic Ray Albedo Neutron Decay (CRAND) as a Source of Inner Belt Electrons: Energy Spectrum Study

Cosmic Ray Albedo Neutron Decay (CRAND) as a Source of Inner Belt Electrons: Energy Spectrum Study

Inner zone and slot electron radial diffusion revisited

Space Weather Effects in the Earth’s Radiation Belts

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