Interplanetary magnetic field control of polar patch velocity

Zhang, Yongliang; McEwen, D. J.; Cogger, L. L.

doi:10.1029/2002ja009742

Cited by 6 publications

(4 citation statements)

References 24 publications

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“…This is in very good agreement with earlier observations [e.g., Cannon et al , ; Fukui et al , ; Zhang et al , ; Moen et al , ; Hosokawa et al , ; Yang et al , ]. The effect of IMF B y on the trajectory of patch material in the polar caps can be explained by the influence of IMF B y on the polar ionospheric convection and on poleward moving auroral forms [e.g., Heppner and Maynard , ; Zhang et al , ; Karlson et al , ; Ruohoniemi and Greenwald , ; Moen et al , ]. Indeed, for IMF B y <0, the cusp inflow region is shifted toward prenoon and the patch material will be pulled into the duskside.…”

Section: Discussionsupporting

confidence: 90%

Interhemispheric study of polar cap patch occurrence based on Swarm in situ data

et al. 2017

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The Swarm satellites offer an unprecedented opportunity for improving our knowledge about polar cap patches, which are regarded as the main space weather issue in the polar caps. We present a new robust algorithm that automatically detects polar cap patches using in situ plasma density data from Swarm. For both hemispheres, we compute the spatial and seasonal distributions of the patches identified separately by Swarm A and Swarm B between December 2013 and August 2016. We show a clear seasonal dependency of patch occurrence. In the Northern Hemisphere (NH), patches are essentially a winter phenomenon, as their occurrence rate is enhanced during local winter and very low during local summer. Although not as pronounced as in the NH, the same pattern is seen for the Southern Hemisphere (SH). Furthermore, the rate of polar cap patch detection is generally higher in the SH than in the NH, especially on the dayside at about 77° magnetic latitude. Additionally, we show that in the NH the number of patches is higher in the postnoon and prenoon sectors for interplanetary magnetic field (IMF) By<0 and IMF By>0, respectively, and that this trend is mirrored in the SH, consistent with the ionospheric flow convection. Overall, our results confirm previous studies in the NH, shed more light regarding the SH, and provide further insight into polar cap patch climatology. Along with this algorithm, we provide a large data set of patches automatically detected with in situ measurements, which opens new horizons in studies of polar cap phenomena.

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Section: Discussionsupporting

confidence: 90%

Interhemispheric study of polar cap patch occurrence based on Swarm in situ data

et al. 2017

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“…This was due to strongly southward IMF B z and slightly negative IMF B y [Weimer, 1995]. Such convections are also consistent with the IMF dependence of polar ionospheric convection direction revealed by drifting of polar patches [Zhang et al, 2003]. The ionospheric convection patterns in Figure 6 indicate the plasma flow was roughly parallel to the red line in Figure 1b, indicating that the plasma and the magnetic fields in both ionosphere and magnetosphere were brought toward the nightside gap where reconnection occurred in the magnetotail and lead to polar rain electron energy dispersion.…”

Section: Eventsupporting

confidence: 86%

Nightside polar rain aurora boundary gap and its applications for magnetotail reconnection

2011

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[1] Polar rain electrons with energy around 1 keV occasionally fill the polar cap ionosphere. Their energy flux is high enough to produce detectable auroral emissions, called polar rain aurora (PRA). We report a PRA event on 2 August 2002 and the estimation of the magnetotail reconnection location and size from the PRA boundary. The distinguishing feature of this event identified from the TIMED/GUVI data is an emission depletion gap between PRA and auroral oval. The size of the gap is about 2°in latitude and extended from the dusk sector (17:00 MLT) to the premidnight sector (22:00 MLT). This gap coincides with the electron flux gap in the DMSP electron energy flux data. The electron flux data show the existence of energy dispersion at the gap. These GUVI and DMSP observations support the idea that the gap is very likely due to a magnetic reconnection in the magnetotail that blocks the solar wind electron entry into the polar ionosphere. Based on the electron energy dispersion, the nightside X line is estimated to be at X = −50 to −60 R E , which is consistent with results from other studies. The gap extends from the nightside to the duskside and presumably to the dawnside. This new information suggests that the extension of the tail X line over the entire plasma sheet in the dawn-dusk direction under a strongly southward IMF (B z ∼ −10 nT) and the curved nature of the X line.Citation: Zhang, Y., L. J. Paxton, and H. Kil (2011), Nightside polar rain aurora boundary gap and its applications for magnetotail reconnection,

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“…McEwen and Harris [1996] and Zhang et al [2003] documented an IMF B y control on azimuthal motion of the patches observed at Eureka station, ideally situated in the middle of the polar cap at Eureka (89°corrected geomagnetic latitude (CGM)), Canada, consistent with convection models developed by Weimer [1995] and Hairston and Heelis [1990]. Hosokawa et al [2009b] presented similar statistical results by applying automated patch detection and velocity determination procedures to all-sky airglow imager observations at Resolute Bay (83°CGM).…”

Section: Patch Transport Across the Polar Capsupporting

confidence: 62%

On the symmetry of ionospheric polar cap patch exits around magnetic midnight

et al. 2015

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In this paper we examine how polar cap patches, which have been frozen into the antisolar flow over the polar cap, are transported into the nighttime auroral oval. First we present a detailed case study from 12 January 2002, with continuous observations of polar cap patches exiting into the nighttime auroral oval in the Scandinavian sector. Satellite images of the auroral oval and all-sky camera observations of 630.0 nm airglow patches are superimposed onto Super Dual Auroral Radar Network convection maps. These composite plots reveal that polar cap patches exit on both the dusk and on the dawn convection cells. Then we present statistics based on 8 years of data from the meridian scanning photometer at Ny-Aalesund, Svalbard, to investigate the possible interplanetary magnetic field (IMF) B y influence on the distribution of patch exits around magnetic midnight. The magnetic local time distribution of patch exits is almost symmetric around magnetic midnight, independent of IMF B y polarity. Synthesizing these observations with previous results, we propose a three-step mechanism for why patch material exits symmetrically around midnight. First, intake of patch material occurs on both convection cells for both IMF B y polarities. Second, plasma intake by transient magnetopause reconnection stretches the newly cut polar cap patches into dawn-dusk elongated forms during their transport into the polar cap. And finally at exit, dawn-dusk elongated patches are split and diverted toward both the dawn and dusk flanks when grabbed by transient tail reconnection.

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Interplanetary magnetic field control of polar patch velocity

Cited by 6 publications

References 24 publications

Interhemispheric study of polar cap patch occurrence based on Swarm in situ data

Interhemispheric study of polar cap patch occurrence based on Swarm in situ data

Nightside polar rain aurora boundary gap and its applications for magnetotail reconnection

On the symmetry of ionospheric polar cap patch exits around magnetic midnight

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