A physical explanation for the magnetic decrease ahead of dipolarization fronts

Yao, Zhonghua; Liu, Jiang; Owen, C. J.; Forsyth, C.; Rae, I. J.; Pu, Z. Y.; Fu, H. S.; Zhou, X.‐Z.; Shi, Quanqi; Du, Aimin; Guo, Ruilong; Chu, Xiangning

doi:10.5194/angeo-33-1301-2015

Cited by 43 publications

(55 citation statements)

References 58 publications

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“…To reveal the unbiased pattern, please refer to and L DT ≈ 3.0 R E . Second, for both regions, a dipolar feature in the Z component of the magnetic field can be observed as has already been reported by others (Angelopoulos et al, 1992;Ohtani et al, 2004;Runov et al, 2011;Liu et al, 2013;Yao et al, 2015). Third, the density variation is different for the two regions.…”

Section: Superposed Epoch Analysis Of Plasma Quantitiessupporting

confidence: 72%

“…Recently, Schmid et al (2015) performed statistical studies on dipolarization fronts and plasma flows in THEMIS data and hypothesize on the development of such events. Yao et al (2015) used the list of Liu et al (2013) to try to physically explain the dipolarization feature of fast flows. Runov et al (2015) showed that the characteristic timescale of the flux transport enhancements does not depend on geocentric distance and is around 40-60 s. Most recently, Wang et al (2016) found evidence of compressible fluctuations during bursty bulk flows in the plasma sheet.…”

Section: Frühauff and K-h Glassmeier: Magnetotail Fast Flowsmentioning

confidence: 99%

“…This simple technique finds the average or median profile of time series, when the key time, i.e., the time of a defined feature in the event, has been properly defined. While usually the key time for fast flows is defined by using magnetic field data (Ohtani et al, 2004;Yao et al, 2015), here, the peak in V X serves as the key time proxy. Therefore, each peak in the data is treated as a single event constituting to the analysis.…”

Section: Superposed Epoch Analysis Of Plasma Quantitiesmentioning

confidence: 99%

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Statistical analysis of magnetotail fast flows and related magnetic disturbances

Frühauff¹,

Glaßmeier²

2016

Ann. Geophys.

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Abstract. This study presents an investigation on the occurrence of fast flows in the magnetotail using the complete available data set of the THEMIS spacecraft for the years 2007 to 2015. The fast flow events (times of enhanced ion velocity) are detected through the use of a velocity criterion, therefore making the resulting database as large as almost 16 000 events. First, basic statistical findings concerning velocity distributions, occurrence rates, group structures are presented. Second, Superposed Epoch Analysis is utilized to account for average profiles of selected plasma quantities. The data reveal representative time series in near and far tail of the Earth with typical timescales of the order of 1-2 min, corresponding to scale sizes of 3 R E . Last, related magnetic field disturbances are analyzed. It is found that the minimum variance direction is essentially confined to a plane almost perpendicular to the main flow direction while, at the same time, the maximum variance direction is aligned with flow and background field directions. The presentation of the database and first statistical findings will prove useful both as input for magneto-hydrodynamical simulations and theoretical considerations of fast flows.

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Section: Superposed Epoch Analysis Of Plasma Quantitiessupporting

confidence: 72%

Section: Frühauff and K-h Glassmeier: Magnetotail Fast Flowsmentioning

confidence: 99%

Section: Superposed Epoch Analysis Of Plasma Quantitiesmentioning

confidence: 99%

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Statistical analysis of magnetotail fast flows and related magnetic disturbances

Frühauff¹,

Glaßmeier²

2016

Ann. Geophys.

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“…(1) As shown previously in the literature, near-earth instabilities and reconnection usually take place in thin current sheet conditions (Büchner and Kuska 1999;Drake et al 1994;Nakamura et al 2006;Birn 1993, 1999). (2) It is also often reported that both reconnection and plasma instability are associated with magnetic dipolarization Lui et al 2008b;Yao et al 2013bYao et al , 2015; (3) Reconnection and reconnection outflows may also directly trigger a pseudo-substorm (or very small substorm) (Pu et al 2010;Yao et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Auroral streamer and its role in driving wave-like pre-onset aurora

Yao

Rae³

et al. 2017

Geosci. Lett.

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The time scales of reconnection outflow, substorm expansion, and development of instabilities in the terrestrial magnetosphere are comparable, i.e., from several to tens of minutes, and their existence is related. In this paper, we investigate the physical relations among those phenomena with measurements during a substorm event on January 29, 2008. We present conjugate measurements from ground-based high-temporal resolution all-sky imagers and in situ THEMIS measurements. An auroral streamer (north-south aligned thin auroral layer) was formed and propagated equatorward, which usually implies an earthward propagating plasma flow in the magnetotail. At the most equatorward part of the auroral streamer, a wave-like auroral band was formed aligning in the east-west direction. The wave-like auroral structure is usually explained as a consequence of instability development. Using AM03 model, we trace the auroral structure to magnetotail and estimate a wavelength of ~0.5 R E . The scale is comparable to the drift mode wavelength determined by the in situ measurements from THEMIS-A, whose footpoint is on the wave-like auroral arc. We also present similar wave-like aurora observations from Cassini ultraviolet imaging spectrograph at Saturn and from Hubble space telescope at Jupiter, suggesting that the wave-like aurora structure is likely a result of fundamental plasma dynamics in the solar system planetary magnetospheres.

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“…In other words, a very large number of DFBs is required to account for the magnetic flux in the near-Earth dipolarization for a moderate size substorm. This result was reached by Lui (2015) and Yao et al (2015).…”

Section: Summary and Discussionmentioning

confidence: 68%

Frozen-in condition for ions and electrons: implication on magnetic flux transport by dipolarizing flux bundles

Lui

2018

Geosci. Lett.

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The ability of dipolarizing flux bundles (DFBs) in transporting magnetic flux from the mid-tail reconnection site for near-Earth dipolarization is evaluated by two methods: the generalized Ohm's law and the concept of flux preserving and line preserving. From the generalized Ohm's law, the breakdown of the frozen-in condition (FIC) for ions is shown to be intimately related to that for electrons. When FIC is not satisfied for the ion fluid associated with energy conversion, it also implies the same for the electron fluid. When FIC holds, the plasma has the flux preserving property. It further guarantees that charged particles on a given magnetic field line will stay together on a magnetic field line at later times, i.e., line preserving. Conversely, when line preserving does not hold, flux preserving does not hold also. Previous detailed examination on the FIC for DFBs revealed that the majority of DFBs associated with energy conversion violate the FIC for the ion fluid. This implies that FIC does not hold for the electron fluid also. Furthermore, plasmas in substorm injections come from vastly different locations, violating the line preserving property and implying that FIC is broken for the magnetic flux tubes associated with substorm injection and dipolarization. These observations indicate that DFBs are not an effective agent to transport magnetic flux within the magnetosphere and further imply that midtail magnetic reconnection is rather ineffective in transporting magnetic flux for near-Earth dipolarization.© The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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A physical explanation for the magnetic decrease ahead of dipolarization fronts

Cited by 43 publications

References 58 publications

Statistical analysis of magnetotail fast flows and related magnetic disturbances

Statistical analysis of magnetotail fast flows and related magnetic disturbances

Auroral streamer and its role in driving wave-like pre-onset aurora

Frozen-in condition for ions and electrons: implication on magnetic flux transport by dipolarizing flux bundles

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