Key points model for polar region currents

Xu, Weihua; Chen, Gengxiong; Du, Aimin; Wu, Yingyan; Chen, Bin; Liu, Xiao-Can

doi:10.1029/2007ja012588

Cited by 4 publications

(4 citation statements)

References 18 publications

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“…The QBO at high latitudes (poleward of 50°) are found to be enhanced for postmidnight local times in the morning sector (LT 00:00–06:00), especially on disturbed days. Both the latitudinal and local time variations of QBO in the auroral zones correspond to the features of the enhanced WEJ and EEJ in the postmidnight sector during substorms [ Kamide and Kokubun , ; Ahn et al ., ; Xu et al ., ]. As coupling parameters based on the solar wind speed, rather than other parameters in magnetospheric activity, have been shown a much better predictor of onset probability of substorms [ Newell et al ., ], it seems likely that the QBO at high latitudes are mainly controlled by the variations of auroral electrojets.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Quasi‐biennial oscillations in the geomagnetic field: Their global characteristics and origin

Finlay

2017

JGR Space Physics

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Quasi‐biennial oscillations (QBOs), with periods in the range 1–3 years, have been persistently observed in the geomagnetic field. They provide unique information on the mechanisms by which magnetospheric and ionospheric current systems are modulated on interannual timescales and are also of crucial importance in studies of rapid core field variations. In this paper, we document the global characteristics of the geomagnetic QBO, using ground‐based data collected by geomagnetic observatories between 1985 and 2010, and reexamine the origin of the signals. Fast Fourier transform analysis of second‐order derivatives of the geomagnetic X, Y, and Z components reveals salient QBO signals at periods of 1.3, 1.7, 2.2, 2.9, and 5.0 years, with the most prominent peak at 2.2 years. The signature of geomagnetic QBO is generally stronger in the X and Z components and with larger amplitudes on geomagnetically disturbed days. The amplitude of the QBO in the X component decreases from the equator to the poles, then shows a local maximum at subauroral and auroral zones. The QBO in the Z component enhances from low latitudes toward the polar regions. At high latitudes (poleward of 50°) the geomagnetic QBO exhibits stronger amplitudes during LT 00:00–06:00, depending strongly on the geomagnetic activity level, while at low latitudes the main effect is in the afternoon sector. These results indicate that the QBOs at low‐to‐middle latitudes and at high latitudes are influenced by different magnetospheric and ionospheric current systems. The characteristics of the multiple peaks in the QBO range are found to display similar latitudinal and local time distributions, suggesting that these oscillations are derived from a common source. The features, including the strong amplitudes seen on disturbed days and during postmidnight sectors, and the results from spherical harmonic analysis, verify that the majority of geomagnetic QBO is of external origin. We furthermore find a very high correlation between the geomagnetic QBO and the QBOs in solar wind speed and solar wind dynamic pressure. This suggests the geomagnetic QBO primarily originates from the current systems due to the solar wind‐magnetosphere‐ionosphere coupling process.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Quasi‐biennial oscillations in the geomagnetic field: Their global characteristics and origin

Finlay

2017

JGR Space Physics

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“…Xu et al [94] proposed a "key-points model" for the current structure and intensity of the polar ionosphere. This summarized six "key points" based on elementary characteristics of the complicated polar current system.…”

Section: Space Weather In Polar Regionsmentioning

confidence: 99%

Progress in polar upper atmospheric physics research in China

Liu¹,

Yang²

2012

APS

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The Chinese Antarctic Great Wall, Zhongshan, Kunlun and Arctic Yellow River stations have unique geographical locations, well suited to carry out polar upper atmospheric observations. This paper reviews the tremendous history of nearly 30 years of Chinese polar expeditions and major progress in polar upper atmospheric physics research. This includes the polar upper atmospheric physics conjugate observation system at Zhongshan Station in the Antarctic and Yellow River Station in the Arctic, and original research achievements in polar ionospheric fields, aurora and particle precipitation, the polar current system, polar plasma convection, geomagnetic pulsations and space plasma waves, inter-hemispheric comparisons of the space environment, space weather in polar regions, power spectrum of the incoherent scatter radar, ionospheric heating experiments and polar mesospheric summer echoes, polar ionosphere-magnetosphere numerical simulation and others. Finally, prospects for Chinese polar upper atmospheric physics research are outlined.

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“…For the variations of field-aligned currents, we used the east-west geomagnetic disturbance field (Y component) lower than 50° in geomagnetic latitude in order to avoid involving the effects from the other strong ionospheric currents at high latitudes. While referring to the variations of auroral electrojets, we chose observatories within 55°-70° because the location of the auroral electrojets may shift out of the coverage of the standard AE observatories during severe storms [19,20]. The north-south geomagnetic disturbance field (X component) was exploited to describe the electrojets.…”

Section: Data Selection and Analysismentioning

confidence: 99%

Nightside field-aligned current during the April 6, 2000 superstorm

et al. 2010

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Using the east-west geomagnetic disturbance fields observed from stations at mid-latitudes, we investigate the characteristics of field-aligned currents on the nightside during the April 6, 2000 superstorm. The results indicate that there is an eastward disturbance on the nightside of Northern Hemisphere during the main phase of magnetic storm, while the interplanetary magnetic field (IMF) is continued southward. The positive disturbances in the postmidnight are larger than that in the premidnight. This suggests that upward field-aligned currents develop on the nightside, when the IMF is directed southward. The peak of upward fieldaligned currents is located in postmidnight, and it will be more obvious at substorm expansion. We get the conclusion that both partial ring current and region-2 field-aligned current shift to dusk sector. The upward region-2 current is decreased at substorm onset, and intensified after it. We also investigate the relationship between the upward field-aligned currents on the nightside and the auroral electrojets at high latitudes. It shows a good correspondence between region-2 current and the westward electrojet in the postmidnight. We suppose that they are both associated with the convection electric field. main phase, field-aligned current, auroral electrojet, substorm current wedge Citation: Wang Y, Hong M H, Chen G X, et al. Nightside field-aligned current during the April 6, 2000 superstorm.As one of most important parts of the solar wind-magnetosphere-ionosphere coupling system, field-aligned currents connect the currents flowing in the magnetosphere and ionosphere. The large-scale FACs exhibit the traditional region 1/region 2 current pattern and the dayside region 0 (traditional cusp) current systems. When solar wind disturbances travel to the Earth magnetopause, the generation of dayside field-aligned currents will lead to magnetic impulse events at high-latitude ionosphere [1][2][3], and also disturb the mid-latitude magnetic field [4]. The Region 1 FieldAligned Currents (R1FACs) flow into high latitude ionosphere on the dawnside and out of ionosphere on the duskside. The Region 2 Field-Aligned Currents (R2FACs) are distributed in the lower latitude, which flow in the opposite direction. The closure of R1FACs in the magnetosphere is located in the plasma sheet and the magnetospheric boundary layer, while R2FACs are closed in the inner magnetosphere by the Partial Ring Current (PRC) [5]. The R2FACs are intensified during magnetic storms accompanied with the development of Ring Current (RCs) and PRCs [6]. At substorm onset, the cross-tail current is collapsed and the current wedge formed in night side with westward eletrojet closed around midnight in the ionosphere [7]. The energy stored in the magnetotail enters high-latitude ionosphere through field-aligned currents and the disturbances in the ionosphere will map to magnetosphere. Since the fieldaligned currents are related to many processes in ionosphere-magnetosphere coupling, such as particle precipitation, electric field ...

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Key points model for polar region currents

Cited by 4 publications

References 18 publications

Quasi‐biennial oscillations in the geomagnetic field: Their global characteristics and origin

Quasi‐biennial oscillations in the geomagnetic field: Their global characteristics and origin

Progress in polar upper atmospheric physics research in China

Nightside field-aligned current during the April 6, 2000 superstorm

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