Radiation Belt Radial Diffusion at Earth and Beyond

Lejosne, Solène; Kollmann, P.

doi:10.1007/s11214-020-0642-6

Cited by 60 publications

(58 citation statements)

References 216 publications

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“…It is noted that although we have opted to use the method of Ozeke et al (2014) to convert power spectral densities to diffusion coefficient values, other formalisms exist (see Lejosne and Kollmann (2020) for a thorough review). As mentioned previously, important differences can exist between the different approaches and it is highlighted that the approach adopted by Ozeke et al (2014) (which follows work by Fei et al (2006)) can lead to an underestimation of the total radial diffusion coefficients by a factor of 2 (Lejosne, 2019).…”

Section: Estimating Radial Diffusion Coefficientsmentioning

confidence: 99%

ULF Wave Driven Radial Diffusion During Geomagnetic Storms: A Statistical Analysis of Van Allen Probes Observations

et al. 2021

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Earth's inner magnetosphere is host to a population of highly variable, highly dynamic, and highly energetic particles known as the Van Allen radiation belts (Li & Hudson, 2019;Van Allen et al., 1958, 1959. Of particular interest is the outer radiation belt population that typically occupies radial distances greater than 3-4 R E and is host to extremely energetic MeV electrons. During geomagnetic storms, this population undergoes dramatic enhancements as well as rapid flux dropouts (e.g., Baker et al., 2004;Murphy et al., 2018;Turner et al., 2012). The MeV electron component of the outer radiation belt can cause problematic satellite

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Section: Estimating Radial Diffusion Coefficientsmentioning

confidence: 99%

ULF Wave Driven Radial Diffusion During Geomagnetic Storms: A Statistical Analysis of Van Allen Probes Observations

et al. 2021

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“…The distribution of phase space density (PSD) over M‐shell or a similar quantity can be a useful indicator of the physical processes acting in a radiation belt. The shape of a radial PSD profile can indicate whether a belt may be supplied through local source process of some kind or if can be simply populated by radial transport of particles from large distances, for example through means of radial diffusion (Lejosne & Kollmann, 2020). According to Liouville's theorem, PSD is conserved along trajectories of particles as long as there are no particle sources or losses.…”

Section: Innermost Beltmentioning

confidence: 99%

“…(2017). Losses at the planet's surface itself combined with radial diffusive transport is sufficient to cause falling PSD profiles (Lejosne & Kollmann, 2020). Often losses are enhanced by distributed losses away from the planet, for example from neutral gas tori leading to energy loss (Clark et al., 2014), charge exchange (Kollmann et al., 2011), or waves that scatter particles along the field lines into the atmosphere (Nénon, Sicard, Kollmann et al., 2018).…”

Section: Innermost Beltmentioning

confidence: 99%

Jupiter's Ion Radiation Belts Inward of Europa's Orbit

et al. 2021

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Jupiter has the largest magnetosphere in the solar system and electron radiation belts with the highest energies (Mauk & Fox, 2010;. It has been visited by several spacecraft (Krupp et al., 2004), yet there are regions in physical space and particle energy that are not well explored (Roussos et al., 2019). High intensities of either electrons or protons can impact the integrity of in-situ radiation measurements Mauk et al., 2016;Nénon, Sicard, Caron et al., 2018), which becomes an issue inward of the orbit of Io and makes reliable measurements in this region particularly rare. NASA's Juno mission-a Jupiter polar orbiting spacecraft-frequently, albeit briefly, visits Jupiter's radiation belts and is equipped with energetic particle instrumentation. Here we present a careful analysis of data obtained by its JEDI instrument (Section 2.1) and filter the measurements to select reliable measurements (Section 3). We use that data to study the physics of the innermost radiation belt (Section 4

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“…Jaynes et al (2018) found that ULF wave acceleration followed by inward radial diffusion can energize source populations to ultra relativistic energies. Electrons with pitch angles near 90° are more effectively energized by radial diffusion (Chen et al, 2007;Lejosne & Kollmann, 2020), which may explain the anisotropies of the higher energy electrons, and why pitch angles appear to become more anisotropic on similar timescales. This is consistent with our results, which show the most anisotropy at the highest energies in the day after Dst minimum.…”

Section: Discussionmentioning

confidence: 99%

Evolution of Pitch Angle Distributions of Relativistic Electrons During Geomagnetic Storms: Van Allen Probes Observations

et al. 2021

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We present a study analyzing relativistic and ultra relativistic electron energization and the evolution of pitch angle distributions using data from the Van Allen Probes. We study the connection between energization and isotropization to determine if there is a coherence across storms and across energies. Pitch angle distributions are fit with a J0sinnθ function, and the variable “n” is characterized as the pitch angle index and tracked over time. Our results show that consistently across all storms with ultra relativistic electron energization, electron distributions are most anisotropic within around a day of Dstmin and become more isotropic in the following week. Also, each consecutively higher energy channel is associated with higher anisotropy after storm main phase. Changes in the pitch angle index are reflected in each energy channel; when 1.8 MeV electron pitch angle distributions increase (or decrease) in pitch angle index, so do the other energy channels. We show that the peak anisotropies differ between coronal mass ejection (CME)‐ and corotating interaction region (CIR)‐driven storms and measure the relaxation rate as the anisotropy falls after the storm. The isotropization rate in pitch angle index for CME‐driven storms is −0.15 ± 0.02 day−1 at 1.8 MeV, −0.30 ± 0.01 day−1 at 3.4 MeV, and −0.39 ± 0.02 day−1 at 5.2 MeV. For CIR‐driven storms, the isotropization rates are −0.10 ± 0.01 day−1 for 1.8 MeV, −0.13 ± 0.02 day−1 for 3.4 MeV, and −0.11 ± 0.02 day−1 for 5.2 MeV. This study shows that there is a global coherence across energies and that storm type may play a role in the evolution of electron pitch angle distributions.

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Radiation Belt Radial Diffusion at Earth and Beyond

Cited by 60 publications

References 216 publications

ULF Wave Driven Radial Diffusion During Geomagnetic Storms: A Statistical Analysis of Van Allen Probes Observations

ULF Wave Driven Radial Diffusion During Geomagnetic Storms: A Statistical Analysis of Van Allen Probes Observations

Jupiter's Ion Radiation Belts Inward of Europa's Orbit

Evolution of Pitch Angle Distributions of Relativistic Electrons During Geomagnetic Storms: Van Allen Probes Observations

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