Electron pitch-angle diffusion: resonant scattering by waves vs. nonadiabatic effects

Artemyev, А. V.; Orlova, K.; Mourenas, D.; Agapitov, Oleksiy; Krasnoselskikh, V.

doi:10.5194/angeo-31-1485-2013

Cited by 28 publications

(38 citation statements)

References 30 publications

(45 reference statements)

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“…However, the more likely situation, where K p < 2, would probably lead to almost no reduction of the magnetic local time‐averaged lifetimes. Another possibility would be an increased pitch angle diffusion of high‐energy (>1 MeV) electrons caused by a strongly reduced magnetic field line curvature in the midnight sector at GEO during disturbed periods [ Artemyev et al , ]. But such effects are expected to occur at GEO only during important disturbances, while the present study focuses instead on moderately disturbed periods during the long recovery phase of storms.…”

Section: Discussionmentioning

confidence: 96%

Statistical analysis of electron lifetimes at GEO: Comparisons with chorus‐driven losses

2014

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The population of electrons in the Earth's outer radiation belt increases when the magnetosphere is exposed to high-speed streams of solar wind, coronal mass ejections, magnetic clouds, or other disturbances. After this increase, the number of electrons decays back to approximately the initial population. This study statistically analyzes the lifetimes of the electron at Geostationary Earth Orbit (GEO) from Los Alamos National Laboratory electron flux data. The decay rate of the electron fluxes are calculated for 14 energies ranging from 24 keV to 3.5 MeV to identify a relationship between the lifetime and energy of the electrons. The statistical data show that electron lifetimes increase with energy. Also, the statistical results show a good agreement up to ∼1 MeV with an analytical model of lifetimes, where electron losses are caused by their resonant interaction with oblique chorus waves, using average wave intensities obtained from Cluster statistics. However, above 500 keV, the measured lifetimes increase with energy becomes less steep, almost stopping. This could partly stem from the difficultly of identifying lifetimes larger than 10 days, for high energy, with the methods and instruments of the present study at GEO. It could also result from the departure of the actual geomagnetic field from a dipolar shape, since a compressed field on the dayside should preferentially increase chorus-induced losses at high energies. However, during nearly quiet geomagnetic conditions corresponding to lifetime measurement periods, it is more probably an indication that outward radial diffusion imposes some kind of upper limit on lifetimes of high-energy electrons near geostationary orbit.

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Section: Discussionmentioning

confidence: 96%

Statistical analysis of electron lifetimes at GEO: Comparisons with chorus‐driven losses

2014

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“…Figure 3 shows the magnetic field (B x , B y , B z , and B t in the GSM coordinate system) measured by the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) , the spinaveraged electron fluxes measured by the Magnetic Electron Ion Spectrometer (MagEIS) [Blake et al, 2013], and Relativistic Electron-Proton Telescope (REPT) instruments of the Energetic particle, Composition, and Thermal plasma suite [Spence et al, 2013] on RBSP-A between 15:00 UT on 15 August Figure 3). Birmingham [1984] and Artemyev et al [2013] have shown that nonadiabatic motion in strongly curved magnetic field lines can result in the electron scattering near equatorial plane. Based on the observations of 1.8 MeV electron fluxes from RBSP-A at 18:52 UT on 15 August (j 1 ), 01:20 UT (j 2 ), and 03:46 UT (j 3 ) on 16 August 2013 (as indicated by the three red dots in Figure 3c), the role of substorm electron injections in the recovery and enhancements of electron fluxes at L *~5 .4 was calculated.…”

Section: Themis-a and Geosynchronous Orbit Satellite Observationsmentioning

confidence: 99%

Prompt enhancement of the Earth's outer radiation belt due to substorm electron injections

et al. 2016

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We present multipoint simultaneous observations of the near‐Earth magnetotail and outer radiation belt during the substorm electron injection event on 16 August 2013. Time History of Events and Macroscale Interactions during Substorms A in the near‐Earth magnetotail observed flux‐enhanced electrons of 300 keV during the magnetic field dipolarization. Geosynchronous orbit satellites also observed the intensive electron injections. Located in the outer radiation belt, RBSP‐A observed enhancements of MeV electrons accompanied by substorm dipolarization. The phase space density (PSD) of MeV electrons at L*~5.4 increased by 1 order of magnitude in 1 h, resulting in a local PSD peak of MeV electrons, which was caused by the direct effect of substorm injections. Enhanced MeV electrons in the heart of the outer radiation belt were also detected within 2 h, which may be associated with intensive substorm electron injections and subsequent local acceleration by chorus waves. Multipoint observations have shown that substorm electron injections not only can be the external source of MeV electrons at the outer edge of the outer radiation belt (L*~5.4) but also can provide the intensive seed populations in the outer radiation belt. These initial higher‐energy electrons from injection can reach relativistic energy much faster. The observations also provide evidence that enhanced substorm electron injections can explain rapid enhancements of MeV electrons in the outer radiation belt.

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“…Transport of hot magnetotail ions into the inner magnetosphere is critical to the formation of the ring current system [e.g., Daglis et al , ; Gkioulidou et al , , and references therein] and generation of ultralow frequency waves [see Hughes et al , ; Glassmeier et al , ; Dai et al , , and references therein]. Electric currents of hot ions significantly deform the magnetic field configuration in the nightside magnetosphere, influencing the dynamics [ West et al , ; Sergeev et al , ; Artemyev et al , ] and scattering [ Orlova and Shprits , , ; Ni et al , ] of relativistic electrons. The local magnetic field configuration also affects whistler wave generation [e.g., Trakhtengerts , ; Omura et al , ; Katoh and Omura , ; Tao et al , ].…”

Section: Introductionmentioning

confidence: 99%

Acceleration of ions by electric field pulses in the inner magnetosphere

2015

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Intense (∼5–15 mV/m), short‐lived (≤1 min) electric field pulses have been observed to accompany earthward propagating, dipolarizing flux bundles (flux tubes with a strong magnetic field) before they are stopped by the strong dipole field. Using Time History of Events and Macroscale Interactions during Substorms observations and test particle modeling, we investigate particle acceleration around L shell ∼7–9 in the nightside magnetosphere and demonstrate that such pulses can effectively accelerate ions with tens of keV initial energy to hundreds of keV. This acceleration occurs because the ion gyroradius is comparable to the spatial scale of the localized electric field pulse at the leading edge of the flux bundle before it stops. The proposed acceleration mechanism can reproduce observed spectra of high‐energy ions. We conclude that the electric field associated with dipolarizing flux bundles prior to their stoppage in the inner magnetosphere provides a natural site for intense local ion acceleration.

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Electron pitch-angle diffusion: resonant scattering by waves vs. nonadiabatic effects

Cited by 28 publications

References 30 publications

Statistical analysis of electron lifetimes at GEO: Comparisons with chorus‐driven losses

Statistical analysis of electron lifetimes at GEO: Comparisons with chorus‐driven losses

Prompt enhancement of the Earth's outer radiation belt due to substorm electron injections

Acceleration of ions by electric field pulses in the inner magnetosphere

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