Birkeland current boundary flows

Archer, William; Knudsen, D. J.; Burchill, J. K.; Jackel, B. J.; Donovan, E.; Connors, Martin; Juusola, Liisa

doi:10.1002/2016ja023789

Cited by 24 publications

(49 citation statements)

References 33 publications

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“…While there are some regions of upward FAC in individual events, we see no region of consistent upward FAC near SAID. The BCBF mark the boundary between upward R1 currents and downward R2 currents, as reported by Archer et al (2017). As one would expect based on their locations relative to the Birkeland currents, BCBF were on average poleward of SAID.…”

Section: Superposed Epoch Analysismentioning

confidence: 61%

“…The flow channels observed on the pass shown in Figure 1 (left column) between 68 ∘ and 70 ∘ MLAT meet the basic criteria of BCBF described in Archer et al (2017) but are also atypical in several ways. They looked at BCBF only while the AE index was <200 nT, and only one eastward and/or westward velocity spike was observed per auroral crossing.…”

Section: 1002/2017ja024577mentioning

confidence: 68%

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Distinguishing Subauroral Ion Drifts From Birkeland Current Boundary Flows

Archer

Knudsen

2018

JGR Space Physics

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The Swarm satellites regularly observe latitudinally narrow ion velocity jets exceeding 1 km/s relative to the surrounding plasma at high latitude. Two distinct categories of duskward directed flow channels are observed. The most common are situated between the Region 1 and Region 2 currents, are observed primarily during quiet geomagnetic conditions, and are called Birkeland current boundary flows. During active conditions, a second type of duskward directed ion velocity jet is observed at the equatorward edge of the Region 2 currents, colocated with a sharp poleward directed plasma density gradient, consistent with subauroral ion drifts. Pedersen current and electric field estimates from the Swarm satellites show both types of flow channel to be associated with low height‐integrated Pedersen conductivity relative to the surrounding plasma. In this study we show two cases in which the Swarm satellites passed through both types of event on the same orbit, as well as the average ion velocity, field‐aligned current, and plasma density surrounding 57 of these events. Some field‐aligned current morphologies previously associated with subauroral ion drifts suggest that they may have instead been Birkeland current boundary flows. In this study we provide a comparative description of both phenomena to facilitate their distinction in future studies.

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Section: Superposed Epoch Analysismentioning

confidence: 61%

Section: 1002/2017ja024577mentioning

confidence: 68%

Distinguishing Subauroral Ion Drifts From Birkeland Current Boundary Flows

Archer

Knudsen

2018

JGR Space Physics

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“…Subsequent observations have shown that the edge of the diffuse aurora in omega bands corresponds to the boundary between the Region 1 and Region 2 current systems, mapping further downtail than the LLBL (Wild et al 2011). Strong shear flows have been observed by low-altitude spacecraft in this region during the occurrence of omega bands (Liu et al 2018), however these shear flows are a ubiquitous feature of the boundary between the R1 and R2 currents (Jiang et al 2015;Archer et al 2017) and as such, the occurrence of a shear flow does not appear to be sufficient to generate an omega band. This region is also generally stable to the KHI particularly when the coupling to the ionosphere is considered but may be unstable to the hybrid Kelvin-Helmholtz/Rayleigh Taylor Instability (Yamamoto 2009(Yamamoto , 2011.…”

Section: Drivers/causesmentioning

confidence: 98%

Physical Processes of Meso-Scale, Dynamic Auroral Forms

Forsyth¹,

Сергеев

Henderson

et al. 2020

Space Sci Rev

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Meso-scale auroral forms, such as poleward boundary intensifications, streamers, omega bands, beads and giant undulations, are manifestations of dynamic processes in the magnetosphere driven, to a large part, by plasma instabilities in the magnetotail. New observations from ground-and space-based instrumentation and theoretical treatments are giving us a clearer view of some of the physical processes behind these auroral forms. However, questions remain as to how some of these observations should be interpreted, given uncertainties in mapping auroral features to locations in the magnetotatil and due to the significant overlap in the results from a variety of models of different plasma instabilities. We provide an overview of recent results in the field and seek to clarify some of the remaining questions with regards to what drives some of the largest and most dynamic auroral forms. Keywords Meso-scale aurora • Poleward boundary intensifications • Auroral streamers • Omega bands • Torches • Auroral beads • Giant undulations • Magnetic mapping • Magnetosphere ionosphere coupling • Plasma instabilities • Magnetotail

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“…Ionospheric flows (or equivalently, electric field) associated with aurorae have been frequently observed since the early era of rocket and spacecraft missions (Burch et al, 1976;Marklund, 1984;Opgenoorth et al, 1990;Smiddy et al, 1980;Ziesolleck et al, 1983). A statistical study by Archer et al (2017) showed that the flows are most prominent at the boundary between Regions 1 and 2 (R1 and R2) currents. In the morning sector, an eastward flow peak is present near the R1/R2 current boundary during active times such as the substorm expansion and growth phases (Fujii et al, 1994;Jiang et al, 2015).…”

Section: 1002/2017gl076485mentioning

confidence: 99%

Flow Shears at the Poleward Boundary of Omega Bands Observed During Conjunctions of Swarm and THEMIS ASI

Liu

Lyons

Archer

et al. 2018

Geophysical Research Letters

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Omega bands are curved aurora forms that evolve from a quiet arc located along the poleward edge of a diffuse auroral band within the midnight to morningside auroral oval. They usually propagate eastward. Because omega bands are a significant contributor to an active magnetotail, knowledge about their generation is important for understanding tail dynamics. Previous studies have shown that auroral streamers, footprints of fast flows in the tail, can propagate into omega bands. Such events, however, are limited, and it is still unclear whether and how the flows trigger the bands. The ionospheric flows associated with omega bands may provide valuable information on the driving mechanisms of the bands. We examine these flows taking advantage of the conjunctions between the Swarm spacecraft and Time History of Events and Macroscale Interactions during Substorms all‐sky imagers, which allow us to demonstrate the relative location of the flows to the omega bands' bright arcs for the first time. We find that a strong eastward ionospheric flow is consistently present immediately poleward of the omega band's bright arc, resulting in a sharp flow shear near the poleward boundary of the band. This ionospheric flow shear should correspond to a flow shear near the inner edge of the plasma sheet. This plasma sheet shear may drive a Kelvin‐Helmholz instability which then distorts the quiet arc to form omega bands. It seems plausible that the strong eastward flows are driven by streamer‐related fast flows or enhanced convection in the magnetotail.

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Birkeland current boundary flows

Cited by 24 publications

References 33 publications

Distinguishing Subauroral Ion Drifts From Birkeland Current Boundary Flows

Distinguishing Subauroral Ion Drifts From Birkeland Current Boundary Flows

Physical Processes of Meso-Scale, Dynamic Auroral Forms

Flow Shears at the Poleward Boundary of Omega Bands Observed During Conjunctions of Swarm and THEMIS ASI

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