Source, Loss, and Transport of Energetic Particles Deep Inside Earth's Magnetosphere (L &amp;lt;4)

Li, Xinlin; Selesnick, R. S.; Zhao, Hong; Baker, D. N.; Blake, J. B.; Temerin, M.

doi:10.1002/9781119815624.ch21

Cited by 6 publications

(6 citation statements)

References 62 publications

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“…For both March and June at L = 2.4, a steady flux population at high energies (⪆2 MeV) is measured by the REPT instrument throughout the study. This is indicative of a stable population in this region, such as stably trapped high‐energy (>100 MeV) protons which have a long lifespan in this region and can penetrate the detector shielding and masquerading as electrons (e.g., Li et al., 2021; Selesnick & Albert, 2019). These proton dynamics are not modulated by individual storm events (e.g., Li et al., 2015, Schultz & Lanzerotti, 1974; Selesnick & Albert, 2019).…”

Section: Resultsmentioning

confidence: 99%

Multi‐MeV Electron Dynamics Near the Inner Edge of the Outer Radiation Belt

Hogan

Zhao

et al. 2021

Geophysical Research Letters

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A variety of dynamic behavior of multi‐MeV electrons near the inner edge of the outer radiation belt has been revealed by detailed analysis of Van Allen Probes data. This study presents multi‐MeV electron flux and phase space density (PSD) using Van Allen Probes data during two strong geomagnetic storms to reveal their energy‐dependent dynamics in the outer belt, with dynamics occurring on timescales of hours to ∼1 week. Enhancements are shown down to L = 2.6, where ∼3 MeV electron populations are enhanced by an order of magnitude during one storm of study. Study of a second comparable storm shows rapid depletion of electron populations up to ∼7 MeV in the region 2.6 ≤ L ≤ 3. We also identify a local electron PSD peak at L ≈ 3 that slowly accumulates during quiet time and is rapidly depleted during an intense storm. Possible contributors to these dynamics are discussed.

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Section: Resultsmentioning

confidence: 99%

Multi‐MeV Electron Dynamics Near the Inner Edge of the Outer Radiation Belt

Hogan

Zhao

et al. 2021

Geophysical Research Letters

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“…Figure 2 demonstrates variations of radiation belt electrons across a wide range in energy: 0.25–6 MeV and L : 1–7. Some of these features have been reported before in different formats, such as energy‐dependent deep penetration of electrons in which very few multi‐MeV electrons were observed below L = 2.6 (Baker et al., 2014; Hogan et al., 2021; X. Li, Baker, et al., 2017; X. Li et al., 1993, 2021; O’Brien et al., 2023; Zhao & Li, 2013a) while less energetic (∼1 MeV) electrons are often seen penetrating into the slot region and sometimes even into the inner belt ( L < 2) (Baker et al., 2004; Claudepierre et al., 2019; Kim et al., 2016; Zhao & Li, 2013b; Zhao et al., 2023; Zheng et al., 2006). Dispersionless injections have mostly been studied using observations near the equatorial plane (Gabrielse et al., 2016; X. Li et al., 1998; Sarris et al., 2002).…”

Section: Measurement Results and Discussionmentioning

confidence: 66%

First Results From REPTile‐2 Measurements Onboard CIRBE

Li,

Selesnick,

Mei

et al. 2024

Geophysical Research Letters

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CIRBE (Colorado Inner Radiation Belt Experiment), a 3U CubeSat, was launched on 15 April 2023 into a sun synchronous orbit (97.4° inclination and 509 km altitude). The sole science payload onboard is REPTile‐2 (Relativistic Electron and Proton Telescope integrated little experiment—2), an advanced version of REPTile which operated in space between 2012 and 2014. REPTile‐2 has 60 channels for electrons (0.25–6 MeV) and 60 channels for protons (6.5–100 MeV). It has been working well, capturing detailed dynamics of the radiation belt electrons, including several orders of magnitude enhancements of the outer belt electrons after an intense magnetic storm, multiple “wisps”‐ an electron precipitation phenomenon associated with human‐made very low frequency (VLF) waves in the inner belt, and “drift echoes” of 0.25–1.4 MeV electrons across the entire inner belt and part of the outer belt. These new observations provide opportunities to test the understanding of the physical mechanisms responsible for these features.

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“…In addition to the lower extension of the atmosphere during solar minimum, the slow increase of radiation belt proton fluxes from 2014 to 2019 may also be influenced by CRAND (Selesnick et al., 2014). The most energetic particles of the galactic cosmic rays (GCR) interact with neutral atoms in the upper atmosphere and produce energetic albedo neutrons which decay into protons, electrons, and antineutrinos (Li et al., 2021). Because they are electrically charged, some of these electrons and protons become geomagnetically trapped at low altitude in the inner belt region.…”

Section: Evolution Of Proton Fluxes In the Saa With The Solar Cyclementioning

confidence: 99%

“…GCR are more intense during the quiet period of 2018 and 2019, so that this source mainly explains the increase of the fluxes. Nevertheless, the magnitude of the flux variation is much greater than the solar cycle variation of atmospheric neutrons that are the source of these trapped protons (Li et al., 2021), so that effects of the terrestrial atmosphere seem to dominate in the solar cycle modulation at low altitude.…”

Section: Evolution Of Proton Fluxes In the Saa With The Solar Cyclementioning

confidence: 99%

Proton Flux Variations During Solar Energetic Particle Events, Minimum and Maximum Solar Activity, and Splitting of the Proton Belt in the South Atlantic Anomaly

et al. 2023

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The South Atlantic Anomaly (SAA) is an area where Earth's magnetic field is particularly low. This comes from the fact that the Earth's magnetic axis is tilted with respect to the Earth's rotation axis by an angle of approximately 11° and that the axis of the magnetic idealized dipole is located some 400 km away from the Earth's center (Brekke, 2013). As a consequence, the SAA is also a region where inner radiation belt particles can mirror at lower altitudes increasing the local particle flux.Unlike the geographic poles, Earth's magnetic poles are not fixed and tend to wander over time, and in parallel, the intensity of Earth's magnetic field is varying over time, for example, presently decreasing (Brekke, 2013). Hence the SAA has been drifting and growing in recent years (Amit et al., 2021;Anderson et al., 2018;Stassinopoulos et al., 2015), and those secular trends have an effect on the inner belt, especially as observed at Low Earth Orbit (LEO) (Girgis et al., 2021).In addition to secular drifts, the inner belt particles are affected by solar cycle variation. In fact, the low-altitude geomagnetically trapped population is known to be coupled to the atmospheric density through changes induced by solar activity (Anderson et al., 2018;Bruno et al., 2021b). Protons with energies above a few tens of MeV mostly originate through the Cosmic-Ray Albedo Neutron Decay (CRAND) mechanism. Because the CRAND source comes mostly from low geomagnetic latitudes due to high cutoff rigidities, the solar modulation of the cosmic rays has a relatively small effect on the variability of the trapped protons (Bruno et al., 2021b). The major variations are due to the atmospheric loss processes, including ionization and scattering of neutral and ionized atoms, induced by solar extreme ultraviolet (EUV) radiation heating the Earth's upper atmosphere. In fact, increased EUV during solar maxima leads to higher neutral and ionospheric densities, causing a decrease of proton fluxes concentrated at low altitudes and L shells.One of the particularities of the particle fluxes at low altitudes is that the high-energy trapped proton fluxes are strongly anisotropic, that is, the proton fluxes depend on their arrival direction in the plane perpendicular to the local magnetic field vector as well as on their pitch angle (angle between their velocity vector and

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Source, Loss, and Transport of Energetic Particles Deep Inside Earth's Magnetosphere (L <4)

Cited by 6 publications

References 62 publications

Multi‐MeV Electron Dynamics Near the Inner Edge of the Outer Radiation Belt

Multi‐MeV Electron Dynamics Near the Inner Edge of the Outer Radiation Belt

First Results From REPTile‐2 Measurements Onboard CIRBE

Proton Flux Variations During Solar Energetic Particle Events, Minimum and Maximum Solar Activity, and Splitting of the Proton Belt in the South Atlantic Anomaly

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