Ballooning‐Interchange Instability in the Near‐Earth Plasma Sheet and Auroral Beads: Global Magnetospheric Modeling at the Limit of the MHD Approximation

Sorathia, Kareem; Merkin, V. G.; Panov, E. V.; Zhang, Binzheng; Lyon, J. G.; Garretson, J.; Ukhorskiy, A. Y.; Ohtani, S.; Sitnov, M. I.; Wiltberger, M. J.

doi:10.1029/2020gl088227

Cited by 88 publications

(107 citation statements)

References 54 publications

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“…Besides, spatial maps of ionospheric currents (not shown) imply that higher resolutions tend to exhibit stronger and smaller-scale ionospheric current patterns. This is consistent with Sorathia et al (2020) who report that the high-resolution global MHD simulation GAMERA produced localized field-aligned current structures. Nevertheless, many observational studies have shown highly-complex ionospheric current features (Apatenkov et al, 2020) such as vortexes (Belakhovsky et al, 2019;Viljanen et al, 2006;Viljanen, Tanskanen, et al, 2006), which pose significant challenges for modelers.…”

Section: Latitudinal and Regional Variabilitysupporting

confidence: 92%

Modeling the Geomagnetic Response to the September 2017 Space Weather Event Over Fennoscandia Using the Space Weather Modeling Framework: Studying the Impacts of Spatial Resolution

et al. 2021

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We must be able to predict and mitigate against geomagnetically induced current (GIC) effects to minimize socio-economic impacts. This study employs the space weather modeling framework (SWMF) to model the geomagnetic response over Fennoscandia to the September 7-8, 2017 event. Of key importance to this study is the effects of spatial resolution in terms of regional forecasts and improved GIC modeling results. Therefore, we ran the model at comparatively low, medium, and high spatial resolutions. The virtual magnetometers from each model run are compared with observations from the IMAGE magnetometer network across various latitudes and over regional-scales. The virtual magnetometer data from the SWMF are coupled with a local ground conductivity model which is used to calculate the geoelectric field and estimate GICs in a Finnish natural gas pipeline. This investigation has lead to several important results in which higher resolution yielded: (1) more realistic amplitudes and timings of GICs, (2) higher amplitude geomagnetic disturbances across latitudes, and (3) increased regional variations in terms of differences between stations. Despite this, substorms remain a significant challenge to surface magnetic field prediction from global magnetohydrodynamic modeling. For example, in the presence of multiple large substorms, the associated large-amplitude depressions were not captured, which caused the largest model-data deviations. The results from this work are of key importance to both modelers and space weather operators. Particularly when the goal is to obtain improved regional forecasts of geomagnetic disturbances and/or more realistic estimates of the geoelectric field.Plain Language Summary Geomagnetically induced currents (GICs) affect large groundbased conducting infrastructure and are associated with the dynamic behavior of geospace electrical currents that drive rapid variations of the surface geomagnetic field. Through geomagnetic induction with the ground conductivity, a geoelectric field is set up which causes unwanted currents to flow in large-scale technological systems. This can result in damage, which can eventually lead to failures and disruptions. To mitigate against GICs we need the capability to predict geomagnetic field variations at the surface with sufficient accuracy, knowledge of the ground conductivity, and a realistic description of the affected system. In this study, we use a global magnetohydrodynamic model (with additional integrated components) to model the surface geomagnetic field variations for the September 2017 event. We compare the simulated ground magnetic fields with those measured at equivalent locations. The spatial resolution of the model is modified to determine if this provides improved performance for capturing spatially structured geomagnetic disturbances. The modeled geomagnetic fields are employed with a ground conductivity model to compute GICs in a natural gas pipeline, which is compared with GIC recordings. We see that higher spatial resolution runs can improve GI...

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Section: Latitudinal and Regional Variabilitysupporting

confidence: 92%

Modeling the Geomagnetic Response to the September 2017 Space Weather Event Over Fennoscandia Using the Space Weather Modeling Framework: Studying the Impacts of Spatial Resolution

et al. 2021

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“…The local B z minimum has been previously studied in the RCM (Yang et al., 2010) and in empirical models (Stephens et al., 2013). Other than the adiabatic earthward convection, an alternative to the adiabatic‐earthward‐convection mechanism is proposed by evacuating the magnetic flux from the tail to the flanks (Gordeev et al., 2017; Hsieh & Otto, 2014; V. A. Sergeev et al., 2018; Sorathia et al., 2020).…”

Section: Discussion and Summarymentioning

confidence: 99%

“…Other than the adiabatic earthward convection, an alternative to the adiabatic-earthward-convection mechanism is proposed by evacuating the magnetic flux from the tail to the flanks (Gordeev et al, 2017;Hsieh & Otto, 2014;V. A. Sergeev et al, 2018;Sorathia et al, 2020).…”

Section: Implication For the Current Sheet Instabilitymentioning

confidence: 99%

Effects of Ion Slippage in Earth's Ionosphere and the Plasma Sheet

Wang

Yang

Nishimura

et al. 2021

Geophysical Research Letters

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Although triggering mechanisms for substorm onsets remain highly controversial, consensus has reached that violation of frozen‐in flux condition in the central plasma sheet is required. In this study, we carry out a numerical gedanken experiment to investigate the effects of the violation by assuming ions slip with respect to the magnetic field lines in the late substorm growth phase while electrons remain magnetized, without specifying the microphysics. The simulation results predict (1) a thin arc and a strong westward electrojet associated with downward‐upward‐downward field‐aligned currents and westward‐eastward‐westward horizontal flows in the ionosphere, which are found to be consistent with a preonset arc observed by the Swarm and the all‐sky imager; (2) a rapid creation of a bubble‐blob pair in the plasma sheet with a tailward hump of Bz that may lead to tearing instability.

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“…We use this simulation, which is described in more detail in Section 2.1 and by Sorathia et al. (2020), to get a realistic distribution of ionospheric currents and associated magnetic field disturbances in a region that is traversed by a simulated EZIE satellite. (2) Zoomed‐in view of magnetic field and currents in this region.…”

Section: Estimating the Electrojet From Simulated Mesospheric Magnetic Field Measurementsmentioning

confidence: 99%

Electrojet Estimates From Mesospheric Magnetic Field Measurements

et al. 2021

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The first attempts to relate ground magnetic disturbances to electric currents in space were carried out more than a century ago. Birkeland (1908) presented a horizontal two-cell equivalent current system which is reminiscent of maps derived from modern magnetometer networks (Waters et al., 2015). Birkeland further proposed a three-dimensional (3D) structure of the space currents that involved magnetic field-aligned currents. This idea remained controversial until it was confirmed by early magnetometer measurements in space (Zmuda et al., 1966). We now view the 3D ionospheric current system as composed of Birkeland currents, that flow along magnetic field lines, and a horizontal current that is confined to a thin conducting layer of the ionosphere, mainly around 100-120 km altitude. The relationship between ground magnetic field observations and this 3D current system is ambiguous, and we therefore often interpret ground magnetic field observations in terms of an equivalent 2D current system. At high latitudes, the equivalent current is nearly identical with the divergence-free part of the horizontal current (e.g., Fukushima, 1976;Untiedt & Baumjohann, 1993). In this study, we use the term electrojet as synonymous with the equivalent current, although it is sometimes used to refer to specific parts of it.

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Ballooning‐Interchange Instability in the Near‐Earth Plasma Sheet and Auroral Beads: Global Magnetospheric Modeling at the Limit of the MHD Approximation

Cited by 88 publications

References 54 publications

Modeling the Geomagnetic Response to the September 2017 Space Weather Event Over Fennoscandia Using the Space Weather Modeling Framework: Studying the Impacts of Spatial Resolution

Modeling the Geomagnetic Response to the September 2017 Space Weather Event Over Fennoscandia Using the Space Weather Modeling Framework: Studying the Impacts of Spatial Resolution

Effects of Ion Slippage in Earth's Ionosphere and the Plasma Sheet

Electrojet Estimates From Mesospheric Magnetic Field Measurements

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