Extreme Birkeland Currents Are More Likely During Geomagnetic Storms on the Dayside of the Earth

Coxon, John C.; Chisham, Gareth; Freeman, Mervyn P.; Forsyth, Colin; Walach, Maria‐Theresia; Murphy, Kyle R.; Vines, Sarah K.; Anderson, Brian J.; Smith, Andrew W.; Fogg, Alexandra R.

doi:10.1029/2023ja031946

Cited by 3 publications

(1 citation statement)

References 115 publications

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“…The spatial variation of the PDF shape and scale was shown to be ordered by the large-scale flow vorticity and the magnetic field-aligned current (FAC) systems that couple the magnetosphere to the high-latitude ionosphere (FAC is proportional to vorticity in the limit of uniform ionospheric conductance). Coxon et al (2022Coxon et al ( , 2023 have shown that PDFs of FACs measured in the ionosphere are similarly leptokurtic, with a similar spatial variation in distribution shape and scale to the flow vorticity.…”

Section: Introductionmentioning

confidence: 94%

The Spatial Variation of Large‐ and Meso‐Scale Plasma Flow Vorticity Statistics in the High‐Latitude Ionosphere and Implications for Ionospheric Plasma Flow Models

Chisham,

Freeman

2024

JGR Space Physics

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The ability to understand and model ionospheric plasma flow on all spatial scales has important implications for operational space weather models. This study exploits a recently developed method to statistically separate large‐scale and meso‐scale contributions to probability density functions (PDFs) of ionospheric flow vorticity measured by the Super Dual Auroral Radar Network (SuperDARN). The SuperDARN vorticity data are first sub‐divided depending on the Interplanetary Magnetic Field (IMF) direction, and the separation method is applied to PDFs of vorticity compiled in spatial regions of size 1° of geomagnetic latitude by 1 hr of magnetic local time, covering much of the high‐latitude ionosphere in the northern hemisphere. The resulting PDFs are fit by model functions using maximum likelihood estimation (MLE) and the spatial variations of the MLE estimators for both the large‐scale and meso‐scale components are presented. The spatial variations of the large‐scale vorticity estimators are ordered by the average ionospheric convection flow, which is highly dependent on the IMF direction. The spatial variations of the meso‐scale vorticity estimators appear independent of the senses of vorticity and IMF direction, but have a different character in the polar cap, the cusp, the auroral region, and the sub‐auroral region. The paper concludes by discussing the sources of the vorticity components in the different regions, and the consequences for the fidelity of ionospheric plasma flow models.

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Section: Introductionmentioning

confidence: 94%

The Spatial Variation of Large‐ and Meso‐Scale Plasma Flow Vorticity Statistics in the High‐Latitude Ionosphere and Implications for Ionospheric Plasma Flow Models

Chisham,

Freeman

2024

JGR Space Physics

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Location of Geomagnetic Disturbances in Relation to the Field Aligned Current Boundary

Bower,

Imber,

Milan

et al. 2024

JGR Space Physics

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Geomagnetic disturbances (GMDs) are rapid fluctuations in the strength and direction of the magnetic field near the surface of the Earth which can cause electric currents to be induced in the ground. The geomagnetically induced currents (GICs) can cause damage to pipelines and power grids. A detection algorithm has been developed to identify rapid changes in 10 s averaged magnetometer data. This higher resolution data is important in capturing the most rapid changes associated with extreme GIC events. The algorithm has been used on an array of ground‐based magnetometers from SuperMAG data from 2010 to 2022, creating a new list of global GMDs. Data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) is used to place the observed GMDs in the context of the global pattern of magnetosphere‐ionosphere field‐aligned currents (FACs). A dawn sector population of GMDs is found to lie near the boundary between the region 1 and region 2 FACs, while a pre‐midnight sector population is found to occur poleward of the FAC boundary on region 1 upward FACs. It is also shown that the latitude of the GMDs expands with the FAC boundary and their occurrence peaks around 77° magnetic latitude.

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Space Weather Forecasts of Ground Level Space Weather in the UK: Evaluating Performance and Limitations

Smith,

Rae,

Forsyth

et al. 2024

Space Weather

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Geomagnetically Induced Currents (GICs) are a severe space weather hazard, driven through coupling between the solar wind and magnetosphere. GICs are rarely measured directly, instead the ground magnetic field variability is often used as a proxy. Recently space weather models have been developed to forecast whether the magnetic field variability (R) will exceed specific, extreme thresholds. We test an example machine learning‐based model developed for the northern United Kingdom. We evaluate its performance (discriminative skill and calibration) as a function of magnetospheric state, solar wind input and magnetic local time. We find that the model's performance is highest during active conditions, for example, geomagnetic storms, and lowest during isolated substorms and “quiet” intervals, despite these conditions dominating the training data set. Correspondingly, the performance is high when the solar wind conditions are elevated (i.e., high velocity, large total magnetic field strength, and the interplanetary magnetic field oriented southward), and at a minimum when the north‐south component of the magnetic field is highly variable or around zero. Regarding magnetic local time, performance is highest within the dusk and night sectors, and lowest during the day. The model appears to capture multiple modes of magnetospheric activity, including substorms and viscous interactions, but poorly predicts impulsive phenomena (i.e., storm sudden commencements) and longer timescale coupling processes. Future models of mid‐latitude magnetic field variability will need to effectively use longer time intervals of unpropagated (i.e., observations from L1) solar wind to more completely describe the magnetospheric conditions and response.

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Extreme Birkeland Currents Are More Likely During Geomagnetic Storms on the Dayside of the Earth

Cited by 3 publications

References 115 publications

The Spatial Variation of Large‐ and Meso‐Scale Plasma Flow Vorticity Statistics in the High‐Latitude Ionosphere and Implications for Ionospheric Plasma Flow Models

The Spatial Variation of Large‐ and Meso‐Scale Plasma Flow Vorticity Statistics in the High‐Latitude Ionosphere and Implications for Ionospheric Plasma Flow Models

Location of Geomagnetic Disturbances in Relation to the Field Aligned Current Boundary

Space Weather Forecasts of Ground Level Space Weather in the UK: Evaluating Performance and Limitations

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