Dipolarization fronts in the near-Earth space and substorm dynamics

Vogiatzis, Ioannis; Isavnin, Alexey; Zong, Qiugang; Sarris, E. T.; Lu, San; Tian, Anmin

doi:10.5194/angeo-33-63-2015

Cited by 17 publications

(27 citation statements)

References 63 publications

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“…This suggest that the re‐reconnecting current sheet most likely has a small‐scale, nonplanar geometry, which seems to be captured very well by the simulations. The agreement between our results, the magnetic field signatures of the dissipating flux rope‐dipolarization front scenario proposed by Slavin, Lepping, Gjerloev, Fairfield, et al (), Vogiatzis et al (), and Lu, Lu, et al (), and the re‐reconnection signatures shown in Lu et al () PIC simulations lead us to the conclusion that MMS indeed observed a dissipating flux rope associated with dipolarization front as we now discuss.…”

Section: Fields and Plasma Signatures Of Re‐reconnection X‐linesupporting

confidence: 90%

“…The flux rope erosion concept proposed by Slavin, Lepping, Gjerloev, Fairfield, et al () can be applied naturally to dipolarization fronts formation by explaining the negative B Z dip, which precedes some of the dipolarization fronts. This mechanism was then reexamined by Vogiatzis et al (, ) using observations from the THEMIS spacecraft. A number of other mechanisms had also been proposed to explain this negative B Z dip feature.…”

Section: Introductionmentioning

confidence: 99%

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Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Poh

Slavin

et al. 2019

JGR Space Physics

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Three‐dimensional global hybrid simulations and observations have shown that earthward‐moving flux ropes (FRs) can undergo magnetic reconnection (or re‐reconnection) with the near‐Earth dipole field to create dipolarization front (DF)‐like signatures that are immediately preceded by brief intervals of negative BZ. The simultaneous erosion of the southward BZ field at the leading edge of the FR and continuous reconnection of lobe magnetic flux at the X‐line tailward of the FR result in the asymmetric south‐north BZ signature in many earthward‐moving FRs and possibly DFs with negative BZ dips prior to their observation. In this study, we analyzed Magnetospheric MultiScale (MMS) observation of fields and plasma signatures associated with the encounter of an ion diffusion region ahead of an earthward‐moving FR on 3 August 2017. The signatures of this re‐reconnection event were (i) +/− BZ reversal, (ii) −/+ bipolar‐type quadrupolar Hall magnetic fields, (iii) northward super‐Alfvénic electron outflow jet of ~1,000–1,500 km/s, (iv) Hall electric field of ~15 mV/m, (v) intense currents of ~40–100 nA/m2, and (vi) J·E′ ~0.11 nW/m3. Our analysis suggests that the MMS spacecraft encounters the ion and electron diffusion regions but misses the X‐line. Our results are in good agreement with particle‐in‐cell simulations of Lu et al. (2016, https://doi.org/10.1002/2016JA022815). We computed a dimensionless reconnection rate of ~0.09 for this re‐reconnection event and through modeling, estimating that the FR would fully dissipate by −16.58 RE. We demonstrated pertubations in the high‐latitude ionospheric currents at the same time of the dissipation of earthward‐moving FRs using ground‐ and space‐based measurements.

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Section: Fields and Plasma Signatures Of Re‐reconnection X‐linesupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Poh

Slavin

et al. 2019

JGR Space Physics

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“…al., 2013; Forsyth et al, 2008;Fu et al, 2013;Sitnov et al, 2013;Vogiatzis et al, 2015). Analogous DF-like structures have also been observed at Mercury and Jupiter (Kronberg et al, 2005;Sundberg et al, 2012;Sun et al, 2015), suggesting that this structure may be common in all planetary magnetotails.…”

Section: Z H Yao Et Al: Dipolarization Front Current Systemmentioning

confidence: 65%

A physical explanation for the magnetic decrease ahead of dipolarization fronts

Yao¹,

Liu

Owen³

et al. 2015

Ann. Geophys.

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Abstract.Recent studies have shown that the ambient plasma in the near-Earth magnetotail can be compressed by the arrival of a dipolarization front (DF). In this paper we study the variations in the characteristics of currents flowing in this compressed region ahead of the DF, particularly the changes in the cross-tail current, using observations from the THEMIS satellites. Since we do not know whether the changes in the cross-tail current lead to a field-aligned current formation or just form a current loop in the magnetosphere, we thus use redistribution to represent these changes of local current density. We found that (1) the redistribution of the cross-tail current is a common feature preceding DFs; (2) the redistribution of cross-tail current is caused by plasma pressure gradient ahead of the DF and (3) the resultant net current redistributed by a DF is an order of magnitude smaller than the typical total current associated with a moderate substorm current wedge (SCW). Moreover, our results also suggest that the redistributed current ahead of the DF is closed by currents on the DF itself, forming a closed current loop around peaks in plasma pressure, what is traditionally referred to as a banana current.

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“…Seven flux ropes are tailward traveling (TFRs), and the other 18 are earthward traveling (EFRs). The few events with b n max largely deviating from theb z GSM are mostly EFRs, which could be deformed due to the strong dipole magnetic field ; see also, Lu et al, 2015;Vogiatzis et al, 2015). Figures 4a and 4c show distributions of b n max and b n min with flux rope locations in the planes of b X GSM -b Z GSM and b X GSM -b Y GSM , respectively.…”

Section: Statistical Resultsmentioning

confidence: 99%

MMS Study of the Structure of Ion‐Scale Flux Ropes in the Earth's Cross‐Tail Current Sheet

Sun

Slavin

Tian

et al. 2019

Geophysical Research Letters

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This study analyzes 25 ion‐scale flux ropes in the Magnetospheric Multiscale (MMS) observations to determine their structures. The high temporal and spatial resolution MMS measurements enable the application of multispacecraft techniques to ion‐scale flux ropes. Flux ropes are identified as quasi‐one‐dimensional (quasi‐1‐D) when they retain the features of reconnecting current sheets; that is, the magnetic field gradient is predominantly northward or southward, and quasi‐2‐D when they exhibit circular cross sections; that is, the magnetic field gradients in the plane transverse to the flux rope axis are comparable. The analysis shows that the quasi‐2‐D events have larger core fields and smaller pressure variations than the quasi‐1‐D events. These two types of flux ropes could be the result of different processes, including magnetic reconnection with different dawn‐dusk magnetic field components, temporal transformation of flattened structure to circular, or interactions with external environments.

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Dipolarization fronts in the near-Earth space and substorm dynamics

Cited by 17 publications

References 63 publications

Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

A physical explanation for the magnetic decrease ahead of dipolarization fronts

MMS Study of the Structure of Ion‐Scale Flux Ropes in the Earth's Cross‐Tail Current Sheet

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