Simulation of a rapid dropout event for highly relativistic electrons with the RBE model

Kang, Seungbum; Fok, M. H.; Glocer, A.; Kang, Min; Choi, Chang‐Shik; Choi, Eun Jin; Hwang, Junga

doi:10.1002/2015ja021966

Cited by 21 publications

(25 citation statements)

References 88 publications

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“…But as showed in our events, it is difficult to obtain the global distribution of EMIC waves from satellites in space. In addition, the statistical EMIC wave distribution achieved from long‐term observations may not realistically represent the wave conditions during a specific event (Kang et al, ). Recently, Y. Zhang et al () developed a new technique to infer EMIC wave amplitudes from the ratio of precipitated and trapped proton fluxes measured by NOAA‐POES satellites.…”

Section: Discussionmentioning

confidence: 99%

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Understanding the Mechanisms of Radiation Belt Dropouts Observed by Van Allen Probes

et al. 2017

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To achieve a better understanding of the dominant loss mechanisms for the rapid dropouts of radiation belt electrons, three distinct radiation belt dropout events observed by Van Allen Probes are comprehensively investigated. For each event, observations of the pitch angle distribution of electron fluxes and electromagnetic ion cyclotron (EMIC) waves are analyzed to determine the effects of atmospheric precipitation loss due to pitch angle scattering induced by EMIC waves. Last closed drift shells (LCDS) and magnetopause standoff position are obtained to evaluate the effects of magnetopause shadowing loss. Evolution of electron phase space density (PSD) versus L* profiles and the μ and K (first and second adiabatic invariants) dependence of the electron PSD drops are calculated to further analyze the dominant loss mechanisms at different L*. Our findings suggest that these radiation belt dropouts can be classified into distinct classes in terms of dominant loss mechanisms: magnetopause shadowing dominant, EMIC wave scattering dominant, and combination of both mechanisms. Different from previous understanding, our results show that magnetopause shadowing can deplete electrons at L* < 4, while EMIC waves can efficiently scatter electrons at L* > 4. Compared to the magnetopause standoff position, it is more reliable to use LCDS to evaluate the impact of magnetopause shadowing. The evolution of electron PSD versus L* profile and the μ, K dependence of electron PSD drops can provide critical and credible clues regarding the mechanisms responsible for electron losses at different L* over the outer radiation belt.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Understanding the Mechanisms of Radiation Belt Dropouts Observed by Van Allen Probes

et al. 2017

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“…Such wave candidates include whistler-mode chorus, plasmaspheric hiss, and electromagnetic ion cyclotron (EMIC) waves, whereas these wave modes tend to predominantly resonate with radiation belt electrons at different energies from~1 keV to 10 MeV. A recent simulation of Kang et al [2016], on the basis of the Radiation Belt Environment (RBE) model , demonstrated that EMIC waves can cause efficient electron flux dropouts in the heart of the radiation belt within a short time period. Xiang et al [2016] looked into multisatellite simultaneous observations of magnetopause and atmospheric losses of radiation belt electrons during an event Journal of Geophysical Research: Space Physics 10.1002/2016JA023067 of intense solar wind dynamic pressure pulse.…”

Section: Discussionmentioning

confidence: 99%

Dynamic responses of the Earth's radiation belts during periods of solar wind dynamic pressure pulse based on normalized superposed epoch analysis

Xiang

et al. 2016

JGR Space Physics

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Using the electron flux measurements obtained from five satellites (GOES 15 and POES 15, 16, 18, and 19), we investigate the flux variations of radiation belt electrons during forty solar wind dynamic pressure pulses identified between September 2012 and December 2014. By utilizing the mean duration of the pressure pulses as the epoch timeline and stretching or compressing the time phases of individual events to normalize the duration by means of linear interpolation, we have performed normalized superposed epoch analysis to evaluate the dynamic responses of radiation belt energetic electrons corresponding to various groups of solar wind and magnetospheric conditions in association with solar wind dynamic pressure pulses. Our results indicate that by adopting the timeline normalization we can reproduce the typical response of the electron radiation belts to pressure pulses. Radiation belt electron fluxes exhibit large depletions right after the Pdyn peak during the periods of northward interplanetary magnetic field (IMF) Bz and are more likely to occur during the Pdyn pulse under southward IMF Bz conditions. For the pulse events with large negative values of (Dst)min, radiation belt electrons respond in a manner similar to those with southward IMF Bz, and the corresponding postpulse recovery can extend to L ~ 3 and exceed the prepulse flux levels. Triggered by the solar wind pressure enhancements, deeper earthward magnetopause erosion provides favorable conditions for the prompt electron flux dropouts that extend down to L ~ 5, and the pressure pulses with longer duration tend to produce quicker and stronger electron flux decay. In addition, the events with high electron fluxes before the Pdyn pulse tend to experience more severe electron flux dropouts during the course of the pulse, while the largest rate of electron flux increase before and after the pulse occurs under the preconditioned low electron fluxes. These new results help us understand how electron fluxes respond to solar wind dynamic pressure pulses and how these responses depend on the solar wind and geomagnetic conditions and on the preconditions in the electron radiation belts.

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“…To examine possible magnetopause shadowing, we investigate drift shells using CIMI with the TS04 model. Drift shells are calculated finding the iso‐contours of the Hamiltonian H at a given time as done by Min et al (, ) using

H = \sqrt{E_{0} ((), E_{0} + 2 M B_{m})} + q normalΦ,

where Φ is the electrostatic potential that we omit as done in Kang et al (). This approximation is valid because convective potentials are much less than 226 keV for this particular event and therefore do not change drift shells significantly; this results in drift shells that are simply a function of B m only.…”

Section: Cimi Simulation Of the Dropoutmentioning

confidence: 99%

An Energetic Electron Flux Dropout Due to Magnetopause Shadowing on 1 June 2013

Kang¹,

Fok²,

Komar

et al. 2018

JGR Space Physics

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We examine the mechanisms responsible for the dropout of energetic electron flux during 31 May to 1 June 2013 using Van Allen Probe (Radiation Belt Storm Probes (RBSP)) electron flux data and simulations with the Comprehensive Inner Magnetosphere‐Ionosphere (CIMI) model. During the storm main phase, L‐shells at RBSP locations are greater than ~8, which are connected to open drift shells. Consequently, diminished electron fluxes were observed over a wide range of energies. The combination of drift shell splitting, magnetopause shadowing, and drift loss all results in butterfly electron pitch angle distributions (PADs) at the nightside. During storm sudden commencement, RBSP observations display electron butterfly PADs over a wide range of energies. However, it is difficult to determine whether there are butterfly PADs during the storm main phase since the maximum observable equatorial pitch angle from RBSP is not larger than ~40° during this period. To investigate the causes of the dropout, the CIMI model is used as a global 4‐D kinetic inner magnetosphere model. The CIMI model reproduces the dropout with very similar timing and flux levels and PADs along the RBSP trajectory for 593 keV. Furthermore, the CIMI simulation shows butterfly PADs for 593 keV during the storm main phase. Based on comparison of observations and simulations, we suggest that the dropout during this event mainly results from magnetopause shadowing.

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Simulation of a rapid dropout event for highly relativistic electrons with the RBE model

Cited by 21 publications

References 88 publications

Understanding the Mechanisms of Radiation Belt Dropouts Observed by Van Allen Probes

Understanding the Mechanisms of Radiation Belt Dropouts Observed by Van Allen Probes

Dynamic responses of the Earth's radiation belts during periods of solar wind dynamic pressure pulse based on normalized superposed epoch analysis

An Energetic Electron Flux Dropout Due to Magnetopause Shadowing on 1 June 2013

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