What Can We Learn about Magnetotail Reconnection from 2D PIC Harris-Sheet Simulations?

Goldman, M. V.; Newman, D. L.; Lapenta, Giovanni

doi:10.1007/s11214-015-0154-y

Cited by 65 publications

(90 citation statements)

References 69 publications

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“…As described in the Appendix, the SMART team is significantly augmented by the addition of three Interdisciplinary Scientist Teams (Goldstein et al 2015;Phan et al 2014;Goldman et al 2015), which have provided important inputs by virtue of MHD and kinetic modeling and experience with previous multi-spacecraft magnetospheric missions (Cluster and THEMIS).…”

Section: Mission Requirementsmentioning

confidence: 99%

Magnetospheric Multiscale Overview and Science Objectives

et al. 2015

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Magnetospheric Multiscale (MMS), a NASA four-spacecraft constellation mission launched on March 12, 2015, will investigate magnetic reconnection in the boundary regions of the Earth's magnetosphere, particularly along its dayside boundary with the solar wind and the neutral sheet in the magnetic tail. The most important goal of MMS is to conduct a definitive experiment to determine what causes magnetic field lines to reconnect in a collisionless plasma. The significance of the MMS results will extend far beyond the Earth's magnetosphere because reconnection is known to occur in interplanetary space and in the solar corona where it is responsible for solar flares and the disconnection events known as coronal mass ejections. Active research is also being conducted on reconnection in the laboratory and specifically in magnetic-confinement fusion devices in which it is a limiting factor in achieving and maintaining electron temperatures high enough to initiate fusion. Finally, reconnection is proposed as the cause of numerous phenomena throughout the universe such as comet-tail disconnection events, magnetar flares, supernova ejections, and dynamics of neutron-star accretion disks. The MMS mission design is focused on answering specific questions about reconnection at the Earth's magnetosphere. The prime focus of the mission is on determining the kinetic processes occurring in the electron diffusion region that are responsible for reconnection and that determine how it is initiated; but the mission will also place that physics into the context of the broad spectrum of physical processes associated with reconnection. Connections to other disciplines such as solar physics, astrophysics, and laboratory plasma physics are expected to be made through theory and modeling as informed by the MMS results.

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Section: Mission Requirementsmentioning

confidence: 99%

Magnetospheric Multiscale Overview and Science Objectives

et al. 2015

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“…Reconnection sites can be detected by looking for a number of 'smoking guns' 37 . The same diagnostics can in the future be used in the analysis of the MMS data to try to verify or falsify the present findings.…”

Section: Secondary Reconnection Sites In 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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“…As of today, the DR is ambiguously defined, and there are many different opinions on its rigorous definition. 20 Promising signatures to identify the DR are enhanced energy dissipation, 63 electron nongyrotropic behavior, 1,49,57 an electron phase-space hole along the inflow direction, 8,26 and characteristic velocity distribution functions (VDFs).…”

Section: Introductionmentioning

confidence: 99%

Pseudo-3D PIC modeling of drift-induced spatial inhomogeneities in planar magnetron plasmas

2016

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Particle dynamics in the electron current layer in collisionless magnetic reconnection is investigated by using a particle-in-cell simulation. The electron motion and velocity distribution functions are studied by tracking self-consistent trajectories. New classes of electron orbits are discovered: figure-eight-shaped regular orbits inside the electron jet, noncrossing regular orbits on the jet flanks, noncrossing Speiser orbits, and nongyrotropic electrons in the downstream of the jet termination region. The properties of a super-Alfv enic outflow jet are attributed to an ensemble of electrons traveling through the Speiser orbits. The noncrossing orbits are mediated by the polarization electric field near the electron current layer. The noncrossing electrons are found to be non-negligible in number density. The impact of these new orbits to electron mixing, spatial distribution of energetic electrons, and observational signatures is presented.

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What Can We Learn about Magnetotail Reconnection from 2D PIC Harris-Sheet Simulations?

Cited by 65 publications

References 69 publications

Magnetospheric Multiscale Overview and Science Objectives

Magnetospheric Multiscale Overview and Science Objectives

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

Pseudo-3D PIC modeling of drift-induced spatial inhomogeneities in planar magnetron plasmas

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