Electromagnetic energy conversion in downstream fronts from three dimensional kinetic reconnection

Lapenta, Giovanni; Goldman, M. V.; Newman, D. L.; Markidis, Stefano; Divin, Andrey

doi:10.1063/1.4872028

Cited by 56 publications

(77 citation statements)

References 43 publications

(114 reference statements)

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“…Figure 1b shows the corresponding equatorial distribution of the conventional dissipation parameter j ⋅ E ′ i . Similar variations of j ⋅ E ′ near DFs, including its negative dips, were reported in simulations of other reconnection regimes (Khotyaintsev et al, 2017;Lapenta et al, 2014). Figure 1b also reveals strong negative dips of the j ⋅ E ′ parameter earthward of the X line in the DF region.…”

Section: Simulation Setup and Resultssupporting

confidence: 82%

Kinetic Dissipation Around a Dipolarization Front

Sitnov

Merkin

Roytershteyn

et al. 2018

Geophysical Research Letters

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Kinetic aspects of energy conversion and dissipation near a dipolarization front (DF) in the magnetotail are considered using fully kinetic 3‐D particle‐in‐cell simulations. The energy conversion is described in terms of the pressure dilatation, as well as the double contraction of deviatoric pressure tensor and traceless strain rate tensor, also known as the Pi‐D parameter in turbulence studies. It is shown that in contrast to the fluid dissipation measure, the Joule heating rate, which cannot distinguish between ion and electron dissipation and reveals deep negative dips at the DF, the Pi‐D parameters, as kinetic analogs of the Joule heating rate, are largely positive and drastically different for ions and electrons. Further analysis of these parameters suggests that ions are heated at and ahead of the DF due to their reflection from the front, while electrons are heated at and behind the DF due to the long‐wavelength lower‐hybrid drift instability.

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Section: Simulation Setup and Resultssupporting

confidence: 82%

Kinetic Dissipation Around a Dipolarization Front

Sitnov

Merkin

Roytershteyn

et al. 2018

Geophysical Research Letters

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“…These observational findings are at odds with 2D models reporting that the main energy conversion site is near the reconnection point 14,21 . However, they are in agreement with 3D kinetic models showing that, once reconnection is studied in the full three dimensions, substantial energy dissipation is present in the reconnection fronts 22,23 . Now the question has become one of urgency: will the MMS mission find its target electron diffusion regions primarily near the inner box of the classic 2D cartoon of nested boxes centred on the x-point, or will it also find them elsewhere?…”

supporting

confidence: 86%

supporting

confidence: 86%

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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“…This case was considered in two previous publications. We reconsider here the same simulation parameters and the readers can find the detailed setup information in [26,24]. In summary, we use the following parameters: m i /m e = 256, v th,e /c = 0.045, T i /T e = 5 .…”

Section: Secondary Reconnection From Single Reconnection Regionmentioning

confidence: 99%

Energy exchanges in reconnection outflows

Lapenta

Goldman

Newman

2016

Plasma Phys. Control. Fusion

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Abstract. Reconnection outflows are highly energetic directed flows that interact with the ambient plasma or with flows from other reconnection regions. Under these conditions the flow becomes highly unstable and chaotic, as any flow jets interacting with a medium. We report here massively parallel simulations of the two cases of interaction between outflow jets and between a single outflow with an ambient plasma. We find in both case the development of a chaotic magnetic field, subject to secondary reconnection events that further complicate the topology of the field lines. The focus of the present analysis is on the energy balance. We compute each energy channel (electromagnetic, bulk, thermal, for each species) and find where the most energy is exchanged and in what form. The main finding is that the largest energy exchange is not at the reconnection site proper but in the regions where the outflowing jets are destabilizied.

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Electromagnetic energy conversion in downstream fronts from three dimensional kinetic reconnection

Cited by 56 publications

References 43 publications

Kinetic Dissipation Around a Dipolarization Front

Kinetic Dissipation Around a Dipolarization Front

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

Energy exchanges in reconnection outflows

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