Electron flux dropouts at Geostationary Earth Orbit: Occurrences, magnitudes, and main driving factors

Boynton, Richard; Mourenas, D.; Balikhin, M. A.

doi:10.1002/2016ja022916

Cited by 37 publications

(77 citation statements)

References 55 publications

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“…The main factors that are considered to cause dropouts are the substorm growth phase and solar wind dynamic pressure. It is important to note that storms are not necessary for presence of dropouts, but dropouts are often seen during substorm activity (e.g., Boynton et al, ; Reeves & Henderson, ). On the other hand abrupt compression of the magnetosphere due to an increase in dynamic pressure causes trapped electrons in the outer radiation belt to be lost to the solar wind via magnetopause shadowing (e.g., Bortnik et al, ; Boynton et al, ; Kim & Chan, ; Onsager et al, ; Reeves et al, , and references therein).…”

Section: Discussionmentioning

confidence: 99%

A Study of Intense Local dB/dt Variations During Two Geomagnetic Storms

et al. 2018

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Interactions between the solar wind and the Earth's magnetosphere manifest many important space weather phenomena. In this paper, magnetosphere‐ionosphere drivers of intense dB/dt produced during geomagnetic storms that occurred on 9 March 2012 and 17 March 2015 are analyzed. A multi‐instrument approach combining Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission space‐borne and ground‐based observations was adopted to examine the magnetosphere‐ionosphere signatures associated with the dB/dt extremes during each storm. To complement the THEMIS measurements, ground‐based magnetometer recordings and All‐Sky Imager observations, equivalent ionospheric currents derived from magnetometer chains across North America and Greenland, and geosynchronous observations from the Los Alamos National Laboratory Synchronous Orbit Particle Analyzer are also examined. Our results show that the most extreme dB/dt variations are associated with marked perturbations in the THEMIS magnetospheric measurements, poleward expanding discrete aurora passing over the magnetometer sites (seen by the ground‐based THEMIS All‐Sky Imagers), intense Pc5 waves, rapid injection of energetic particles, and intense auroral westward currents. Substorms are considered as the major driver with a possible contribution from magnetospheric waves. The findings of this study strongly suggest that the localization of extreme dB/dt variations is most likely related to the mapping of magnetosphere currents to local ionospheric structures.

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Section: Discussionmentioning

confidence: 99%

A Study of Intense Local dB/dt Variations During Two Geomagnetic Storms

et al. 2018

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“…The method of using the physical interpretability of the NARMAX model structure detection has since been used in many other studies to identify relationships between the solar wind and various aspects of the magnetosphere. Examples include studies of SYM‐H index (Beharrell & Honary, ), proton fluxes at GEO (Boynton, Billings, et al, ), the electron fluxes (Balikhin et al, ; Boynton, Balikhin, Billings, Reeves, et al, ), and electron flux dropouts at GEO (Boynton, Mourenas, et al, ) and at the GPS orbit (Boynton et al, ).…”

Section: Narmax Methodologymentioning

confidence: 99%

The System Science Development of Local Time‐Dependent 40‐keV Electron Flux Models for Geostationary Orbit

et al. 2019

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At geosynchronous Earth orbit, the radiation belt/ring current electron fluxes with energies up to several hundred kiloelectron volts can vary widely in magnetic local time (MLT). This study aims to develop Nonlinear AutoRegressive eXogenous models using system science techniques, which account for the spatial variation in MLT. This is difficult for system science techniques, since there is sparse data availability of the electron fluxes at different MLT. To solve this problem, the data are binned from Geostationary Operational Environmental Satellites (GOES) 13, 14, and 15 by MLT, and a separate Nonlinear AutoRegressive eXogenous model is deduced for each bin using solar wind variables as the inputs to the model. These models are then conjugated into one spatiotemporal forecast. The model performance statistics for each model varies in MLT with a prediction efficiency between 47% and 75% and a correlation coefficient between 51.3% and 78.9% for the period from 1 March 2013 to 31 December 2017.

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“…Magnetopause shadowing can also produce a sharp gradient at the last closed drift shell (LCDS) and create a favorable condition for strong outward radial diffusion (Shprits et al, ; Turner et al, ; Yu et al, ). Thus, magnetopause shadowing and outward radial diffusion can drive drift losses to the magnetosphere boundary (Boynton et al, ; Gao et al, ; Ohtani et al, ; Shprits et al, ; Turner et al, ).…”

Section: Introductionmentioning

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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Electron flux dropouts at Geostationary Earth Orbit: Occurrences, magnitudes, and main driving factors

Cited by 37 publications

References 55 publications

A Study of Intense Local dB/dt Variations During Two Geomagnetic Storms

A Study of Intense Local dB/dt Variations During Two Geomagnetic Storms

The System Science Development of Local Time‐Dependent 40‐keV Electron Flux Models for Geostationary Orbit

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

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