Evolution of the lower hybrid drift instability at reconnection jet front

Divin, Andrey; Khotyaintsev, Yuri; Vaivads, A.; André, Mats; Markidis, Stefano; Lapenta, Giovanni

doi:10.1002/2014ja020503

Cited by 73 publications

(104 citation statements)

References 71 publications

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“…Note that there are already several DF observations by MMS with a small separation close to 40 km (e.g., Liu et al, 2018). However, these finger-like density structures arising from kinetic instabilities are at ion-electron hybrid scale (e.g., Divin, Khotyaintsev, Vaivads, André, Markidis, et al, 2015;Vapirev et al, 2013), larger than the scale of the density gradient we observed in the low-density side of the DF. More importantly, these observations did not investigate the electron-scale current, electric structure, and energy conversion using multispacecraft method.…”

Section: Summary and Discussionmentioning

confidence: 57%

“…To date, DF structure at ion scale has been well investigated by spacecraft observations and numerical simulations (e.g., Balikhin et al, 2014;Drake et al, 2014;Divin, Khotyaintsev, Vaivads, André, Markidis, et al, 2015;Fu et al, 2012a;Pritchett et al, 2014;Vapirev et al, 2013;Yao et al, 2016), while DF structure at electron scale still remains not fully understood due to instrumental limitations and spacecraft separation distances. Studying the DF dynamics is of particular interest for the magnetotail physics.…”

Section: Introductionmentioning

confidence: 99%

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Electron‐Scale Measurements of Dipolarization Front

Liu

et al. 2018

Geophysical Research Letters

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Dipolarization front (DF)—a sharp boundary with scale of ion inertial length (c/ωpi) in the Earth's magnetotail—can also have fine structures at electron scale (c/ωpe). Such electron‐scale structures, determining the local energy conversion, have not been revealed by multispacecraft observations so far, due to the large separation of spacecraft in previous studies. Here we report the first electron‐scale multispacecraft measurements of DF, using data from the recent Magnetospheric Multiscale mission. We find strong parallel currents only in the high‐density side of the DF but strong perpendicular currents across the whole DF. We find no parallel electric fields during the DF interval. Although DF is primarily an energy‐load region (E·J > 0), the electron‐scale currents could lead to a localized energy generation (E·J < 0). Such features are different from those reported in previous multispacecraft studies, where the currents, electric fields, and energy conversion are uniform across the DF; they also shed lights on the study of substorm current wedge, which is crucial in the magnetosphere‐ionosphere coupling.

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Section: Summary and Discussionmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Electron‐Scale Measurements of Dipolarization Front

Liu

et al. 2018

Geophysical Research Letters

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“…The front is again subject to the same instability as described above and driven by the density gradients at the fronts. A detailed investigation of the nature of the instability in the present run and discussed in previous research 34,41 is reported in the Supplementary Methods. Although the nature of the instability is the same as in Run A, the nonlinear evolution presents some differences owing to the different box size and boundary conditions.…”

Section: Secondary Reconnection In Reconnection Frontsmentioning

confidence: 89%

“…32) and kinetic 33 simulations. When considered at the kinetic level, this instability acquires the nature of a drift instability caused by the presence of drifts associated with the density gradients 34 . An in-depth analysis of the nature of the instability as well its energetic consequences is provided in the Supplementary Information.…”

Section: Simulation Of Reconnection-generated Flux Ropesmentioning

confidence: 99%

Secondary reconnection sites in reconnection-generated flux ropes and reconnection fronts

et al. 2015

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The primary target of the Magnetospheric MultiScale (MMS) mission is the electron-scale di usion layer around reconnection sites. Here we study where these regions are found in full three-dimensional simulations. In two dimensions the sites of electron di usion, defined as the regions where magnetic topology changes and electrons move with respect to the magnetic field lines, are located near the reconnection site. But in three dimensions we find that the reconnection exhaust far from the primary reconnection site also becomes host to secondary reconnection sites. Four diagnostics are used to demonstrate the point: the direct observation of topology impossible without secondary reconnection, the direct measurement of topological field line breakage, the measurement of electron jets emerging from secondary reconnection regions, and the violation of the frozen-in condition. We conclude that secondary reconnection occurs in a large part of the exhaust, providing many more chances for MMS to find itself in the right region to hit its target.T he primary focus of the planned Magnetospheric MultiScale (MMS) Mission 1 is the identification and in situ study of electron-scale regions where magnetic reconnection develops (http://mms.gsfc.nasa.gov/science.html). Magnetic reconnection 2 is believed to be the engine of many space and astrophysical processes where magnetic energy is stored over relatively long times to be released suddenly in bursts of kinetic energy. The mission planning and the thinking of the community has been in large part informed by the two-dimensional (2D) picture that has emerged from decades of simulations based on the classic field reversal configuration, where two regions of oppositely directed magnetic fields reconnect at one central location called the x-point. There magnetic field lines break and form new connections.This paradigm has been tremendously successful and from 2D simulations has found confirmation in many laboratory experiments 3 and in situ space observations 4 . When going from two to three dimensions, the model still remains valid if one can assume the presence of a region where the variations along the out-of-plane directions are small. In this case, extended reconnection regions develop, retaining a 2D-like configuration over significant widths in the out-of-plane direction 5,6 . But 3D effects can drastically alter the structure of a reconnection site 7 , with the possibility of inherently 3D configurations even in fast kinetic reconnection 8 .We think it is imperative to ask the question as to how these new 3D discoveries impact the execution of the MMS mission. The mission was designed with the two-nested-box vision 9 : around the reconnection site the ions become decoupled from magnetic field lines in a larger region, whereas the electrons continue to move along with the field lines until a smaller inner region is reached. This scheme is etched into the minds of every researcher working in reconnection and appears in the place of honour in the science section of the MMS web...

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“…The nature of this instability is that of a drift mode [15,12]: the density at the front has a strong gradient in a direction normal to the field, the typical condition for drift modes [12]. We reported elsewhere the analysis of the mode spatial and temporal spectrum [7].…”

Section: Drift-interchange Destabilization Of Fronts Formed By Reconnmentioning

confidence: 99%

Where should MMS look for electron diffusion regions?

Lapenta

Goldman

Newman

2016

J. Phys.: Conf. Ser.

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Abstract. A great possible achievement for the MMS mission would be crossing electron di↵usion regions (EDR). EDR are regions in proximity of reconnection sites where electrons decouple from field lines, breaking the frozen in condition. Decades of research on reconnection have produced a widely shared map of where EDRs are. We expect reconnection to take place around a so called x-point formed by the intersection of the separatrices dividing inflowing from outflowing plasma. The EDR forms around this x-point as a small electron scale box nested inside a larger ion di↵usion region. But this point of view is based on a 2D mentality. We have recently proposed that once the problem is considered in full 3D, secondary reconnection events can form [Lapenta et al., Nature Physics, 11, 690, 2015] in the outflow regions even far downstream from the primary reconnection site. We revisit here this new idea confirming that even using additional indicators of reconnection and even considering longer periods and wider distances the conclusion remains true: secondary reconnection sites form downstream of a reconnection outflow causing a sort of chain reaction of cascading reconnection sites. If we are right, MMS will have an interesting journey even when not crossing necessarily the primary site. The chances are greatly increased that even if missing a primary site during an orbit, MMS could stumble instead on one of these secondary sites.

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Evolution of the lower hybrid drift instability at reconnection jet front

Cited by 73 publications

References 71 publications

Electron‐Scale Measurements of Dipolarization Front

Electron‐Scale Measurements of Dipolarization Front

Secondary reconnection sites in reconnection-generated flux ropes and reconnection fronts

Where should MMS look for electron diffusion regions?

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