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Sample records for collisionless driven reconnection

  1. Collisionless driven reconnection in an open system

    International Nuclear Information System (INIS)

    Horiuchi, Ritoku; Pei, Wenbing; Sato, Tetsuya

    2000-06-01

    Particle simulation studies of collisionless driven reconnection in an open system are presented. Collisionless reconnection evolves in two steps in accordance with the formation of two current layers, i.e., an ion current layer in the early ion phase and an electron current layer in the late electron phase. After the electron current layer is formed inside the ion current layer, the system relaxes gradually to a steady state when convergent plasma flow is driven by an external electric field with a narrow input window. On the other hand, when the convergent plasma flow is driven from the wide input window, magnetic reconnection takes place in an intermittent manner, due to the frequent formation of magnetic islands in the vicinity of neutral sheet. (author)

  2. Influence of a guide field on collisionless driven reconnection

    International Nuclear Information System (INIS)

    Horiuchi, Ritoku; Usami, Shunsuke; Ohtani, Hiroaki

    2014-01-01

    The influence of a guide field on collisionless driven reconnection is investigated by means of two-dimensional electromagnetic particle simulation in an open system. In a quasi-steady state when reconnection electric field evolves fully, a current layer evolves locally in a narrow kinetic region and its scale decreases in proportion to an electron meandering scale as the guide field is intensified. Here, the meandering scale stands for an average spatial scale of nongyrotropic motions in the vicinity of the reconnection point. Force terms associated with off-diagonal components of electron and ion pressure tensors, which are originating from nongyrotropic motions of charged particles, becomes dominant at the reconnection point and sustain the reconnection electric field even when the guide field is strong. It is also found that thermalization of both ions and electrons is suppressed by the guide field. For the weak guide field, an electron nonthermal component is significantly created through a fast outburst from the kinetic region, while for the strong guide field, an ion nonthermal component is generated through the acceleration by an in-plane electric field near the magnetic separatrix. (author)

  3. Particle simulation study of collisionless driven reconnection in a sheared magnetic field

    International Nuclear Information System (INIS)

    Horiuchi, Ritoku; Sato, Tetsuya.

    1996-08-01

    Nonlinear development of collisionless driven reconnection and the consequent energy conversion process between the field and particles in a sheared magnetic field are investigated by means of a two-and-a-half-dimensional particle simulation. Magnetic reconnection takes place in two steps irrespective of a longitudinal magnetic field, but the growth rate of reconnection field varies in proportion to the E x B drift velocity at an input boundary. It is clearly observed that the triggering mechanism of collisionless driven reconnection for the fast growing phase changes from an electron meandering dominance in a weak longitudinal field to an electron inertia dominance in a strong field. The electron acceleration and heating take place in the reconnection area under the influence of reconnection electric field, while the electron energy is converted to the ion energy through the action of electrostatic (ambipolar) field excited by magnetic compression in the downstream. It is also found that, in the presence of a longitudinal magnetic field, the electron acceleration by the reconnection field takes place effectively and the generated force-free current is maintained for a long period while forming an asymmetric spatial profile of current layer. (author)

  4. Nonlinear collisionless magnetic reconnection

    Science.gov (United States)

    Ottaviani, M.; Porcelli, F.

    1993-12-01

    Collisionless magnetic reconnection in regimes where the mode structure is characterized by global convection cells is found to exhibit a quasiexplosive time behavior in the early nonlinear stage where the fluid displacement is smaller than the equilibrium scale length. This process is accompanied by the formation of a current density sublayer narrower than the skin depth. This sublayer keeps shrinking with time.

  5. Lessons on collisionless reconnection from quantum fluids

    Directory of Open Access Journals (Sweden)

    Yasuhito eNarita

    2014-12-01

    Full Text Available Magnetic reconnection in space plasmas remains a challenge in physics in that the phenomenon is associated with the breakdown of frozen-in magnetic field in a collisionless medium. Such a topology change can also be found in superfluidity, known as the quantum vortex reconnection. We give a plasma physicists' view of superfluidity to obtain insights on essential processes in collisionless reconnection, including discussion of the kinetic and fluid pictures, wave dynamics, and time reversal asymmetry. The most important lesson from the quantum fluid is the scenario that reconnection is controlled by the physics of topological defects on the microscopic scale, and by the physics of turbulence on the macroscopic scale. Quantum vortex reconnection is accompanied by wave emission in the form of Kelvin waves and sound waves, which imprints the time reversal asymmetry.

  6. Whistler dominated quasi-collisionless magnetic reconnection

    International Nuclear Information System (INIS)

    Biskamp, D.; Drake, J.F.

    1995-05-01

    A theory of fast quasi-collisionless reconnection is presented. For spatial scales smaller than the ion inertia length the electrons decouple from the ions and the dynamics is described by electron magnetohydrodynamics (EMHD). A qualitative analysis of the reconnection region is obtained, which is corroborated by numerical simulations. The main results are that in contrast to resistive reconnection no macroscopic current sheet is generated, and the reconnection rate is independent of the smallness parameters of the system, i.e. the electron inertia length and the dissipation coefficients. At larger scales the coupling to the ions is important, which, however, does not change the small-scale dynamics. The reconnection rate is only limited by ion inertia being independent of the electron inertia scale and the dissipation coefficients. Reconnection is much faster than in the absence of the whistler mode. (orig.)

  7. Superdiffusion revisited in view of collisionless reconnection

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2014-06-01

    Full Text Available The concept of diffusion in collisionless space plasmas like those near the magnetopause and in the geomagnetic tail during reconnection is reexamined making use of the division of particle orbits into waiting orbits and break-outs into ballistic motion lying at the bottom, for instance, of Lévy flights. The rms average displacement in this case increases with time, describing superdiffusion, though faster than classical, is still a weak process, being however strong enough to support fast reconnection. Referring to two kinds of numerical particle-in-cell simulations we determine the anomalous diffusion coefficient, the anomalous collision frequency on which the diffusion process is based, and construct a relation between the diffusion coefficients and the resistive scale. The anomalous collision frequency from electron pseudo-viscosity in reconnection turns out to be of the order of the lower-hybrid frequency with the latter providing a lower limit, thus making similar assumptions physically meaningful. Tentative though not completely justified use of the κ distribution yields κ ≈ 6 in the reconnection diffusion region and, for the anomalous diffusion coefficient, the order of several times Bohm diffusivity.

  8. Collisionless magnetic reconnection in a plasmoid chain

    Science.gov (United States)

    Markidis, S.; Henri, P.; Lapenta, G.; Divin, A.; Goldman, M. V.; Newman, D.; Eriksson, S.

    2012-02-01

    The kinetic features of plasmoid chain formation and evolution are investigated by two dimensional Particle-in-Cell simulations. Magnetic reconnection is initiated in multiple X points by the tearing instability. Plasmoids form and grow in size by continuously coalescing. Each chain plasmoid exhibits a strong out-of plane core magnetic field and an out-of-plane electron current that drives the coalescing process. The disappearance of the X points in the coalescence process are due to anti-reconnection, a magnetic reconnection where the plasma inflow and outflow are reversed with respect to the original reconnection flow pattern. Anti-reconnection is characterized by the Hall magnetic field quadrupole signature. Two new kinetic features, not reported by previous studies of plasmoid chain evolution, are here revealed. First, intense electric fields develop in-plane normally to the separatrices and drive the ion dynamics in the plasmoids. Second, several bipolar electric field structures are localized in proximity of the plasmoid chain. The analysis of the electron distribution function and phase space reveals the presence of counter-streaming electron beams, unstable to the two stream instability, and phase space electron holes along the reconnection separatrices.

  9. About 'reconnection' in a collisionless plasma

    International Nuclear Information System (INIS)

    Pellat, R.

    1979-01-01

    Two kinds of mechanisms have been advertised for magnetic field line reconnection in plasmas: a slow diffusive process, proposed by Parker and Sweet (1958), related to the Tearing mode and field line stochasticity; an Alfenic flow, with a fast merging rate, the so-called Petschek theory. The present author considers both mechanisms successively and emphasizes the yet unsolved theoretical difficulties. (Auth.)

  10. Accessing the Asymmetric Collisionless Reconnection Regime in the Terrestrial Reconnection Experiment (TREX)

    Science.gov (United States)

    Greess, S.; Egedal, J.; Olson, J.; Millet-Ayala, A.; Myers, R.; Wallace, J.; Clark, M.; Forest, C.

    2017-12-01

    Kinetic effects are expected to dominate the collisionless reconnection regime, where the mean free path is large enough that the anisotropic electron pressure can develop without being damped away by collisional pitch angle scattering. In simulations, the anisotropic pressure drives the formation of outflow jets [1]. These jets are expected to play a role in the reconnection layer at the Earth's magnetopause, which is currently being explored by Magnetospheric Multiscale Mission (MMS) [2]. Until recently, this regime of anisotropic pressure was inaccessible by laboratory experiments, but new data from the Terrestrial Reconnection Experiment (TREX) shows that fully collisionless reconnection can now be achieved in the laboratory. Future runs at TREX will delve deeper into this collisionless regime in both the antiparallel and guide-field cases. [1] Le, A. et al. JPP, 81(1). doi: 10.1017/S0022377814000907. [2] Burch, J. L. et al. Space Sci. Rev. 199,5. doi: 10.1007/s11214-015-0164-9 Supported in part by NSF/DOE award DE-SC0013032.

  11. Scaling of Magnetic Reconnection in Relativistic Collisionless Pair Plasmas

    Science.gov (United States)

    Liu, Yi-Hsin; Guo, Fan; Daughton, William; Li, Hui; Hesse, Michael

    2015-01-01

    Using fully kinetic simulations, we study the scaling of the inflow speed of collisionless magnetic reconnection in electron-positron plasmas from the non-relativistic to ultra-relativistic limit. In the anti-parallel configuration, the inflow speed increases with the upstream magnetization parameter sigma and approaches the speed of light when sigma is greater than O(100), leading to an enhanced reconnection rate. In all regimes, the divergence of the pressure tensor is the dominant term responsible for breaking the frozen-in condition at the x-line. The observed scaling agrees well with a simple model that accounts for the Lorentz contraction of the plasma passing through the diffusion region. The results demonstrate that the aspect ratio of the diffusion region, modified by the compression factor of proper density, remains approximately 0.1 in both the non-relativistic and relativistic limits.

  12. Three dimensional density cavities in guide field collisionless magnetic reconnection

    Science.gov (United States)

    Markidis, S.; Lapenta, G.; Divin, A.; Goldman, M.; Newman, D.; Andersson, L.

    2012-03-01

    Particle-in-cell simulations of collisionless magnetic reconnection with a guide field reveal for the first time the three dimensional features of the low density regions along the magnetic reconnection separatrices, the so-called cavities. It is found that structures with further lower density develop within the cavities. Because their appearance is similar to the rib shape, these formations are here called low density ribs. Their location remains approximately fixed in time and their density progressively decreases, as electron currents along the cavities evacuate them. They develop along the magnetic field lines and are supported by a strong perpendicular electric field that oscillates in space. In addition, bipolar parallel electric field structures form as isolated spheres between the cavities and the outflow plasma, along the direction of the low density ribs and of magnetic field lines.

  13. Collisionless magnetic reconnection: analytical model and PIC simulation comparison

    Directory of Open Access Journals (Sweden)

    V. Semenov

    2009-03-01

    Full Text Available Magnetic reconnection is believed to be responsible for various explosive processes in the space plasma including magnetospheric substorms. The Hall effect is proved to play a key role in the reconnection process. An analytical model of steady-state magnetic reconnection in a collisionless incompressible plasma is developed using the electron Hall MHD approximation. It is shown that the initial complicated system of equations may split into a system of independent equations, and the solution of the problem is based on the Grad-Shafranov equation for the magnetic potential. The results of the analytical study are further compared with a two-dimensional particle-in-cell simulation of reconnection. It is shown that both methods demonstrate a close agreement in the electron current and the magnetic and electric field structures obtained. The spatial scales of the acceleration region in the simulation and the analytical study are of the same order. Such features like particles trajectories and the in-plane electric field structure appear essentially similar in both models.

  14. Turbulent transport in 2D collisionless guide field reconnection

    Science.gov (United States)

    Muñoz, P. A.; Büchner, J.; Kilian, P.

    2017-02-01

    Transport in hot and dilute, i.e., collisionless, astrophysical and space, plasmas is called "anomalous." This transport is due to the interaction between the particles and the self-generated turbulence by their collective interactions. The anomalous transport has very different and not well known properties compared to the transport due to binary collisions, dominant in colder and denser plasmas. Because of its relevance for astrophysical and space plasmas, we explore the excitation of turbulence in current sheets prone to component- or guide-field reconnection, a process not well understood yet. This configuration is typical for stellar coronae, and it is created in the laboratory for which a 2.5D geometry applies. In our analysis, in addition to the immediate vicinity of the X-line, we also include regions outside and near the separatrices. We analyze the anomalous transport properties by using 2.5D Particle-in-Cell code simulations. We split off the mean slow variation (in contrast to the fast turbulent fluctuations) of the macroscopic observables and determine the main transport terms of the generalized Ohm's law. We verify our findings by comparing with the independently determined slowing-down rate of the macroscopic currents (due to a net momentum transfer from particles to waves) and with the transport terms obtained by the first order correlations of the turbulent fluctuations. We find that the turbulence is most intense in the "low density" separatrix region of guide-field reconnection. It is excited by streaming instabilities, is mainly electrostatic and "patchy" in space, and so is the associated anomalous transport. Parts of the energy exchange between turbulence and particles are reversible and quasi-periodic. The remaining irreversible anomalous resistivity can be parametrized by an effective collision rate ranging from the local ion-cyclotron to the lower-hybrid frequency. The contributions to the parallel and the perpendicular (to the magnetic

  15. Self-reinforcing process of the reconnection electric field in the electron diffusion region and onset of collisionless magnetic reconnection

    International Nuclear Information System (INIS)

    Lu Quanming; Lu San; Huang Can; Wu Mingyu; Wang Shui

    2013-01-01

    The onset of collisionless magnetic reconnection is considered to be controlled by electron dynamics in the electron diffusion region, where the reconnection electric field is balanced mainly by the off-diagonal electron pressure tensor term. Two-dimensional particle-in-cell simulations are employed in this paper to investigate the self-reinforcing process of the reconnection electric field in the electron diffusion region, which is found to grow exponentially. A theoretical model is proposed to demonstrate such a process in the electron diffusion region. In addition the reconnection electric field in the pileup region, which is balanced mainly by the electromotive force term, is also found to grow exponentially and its growth rate is twice that in the electron diffusion region. (paper)

  16. On the relationship between quadrupolar magnetic field and collisionless reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Smets, R., E-mail: roch.smets@lpp.polytechnique.fr; Belmont, G. [LPP, University P. and M. Curie, CNRS, Ecole Polytechnique, F-91128 Palaiseau (France); Aunai, N. [IRAP, University Paul Sabatier, F-31028 Toulouse (France); Boniface, C. [CEA/DAM, DIF, F-91297 Arpajon (France); Fuchs, J. [LULI, Ecole Polytechnique, CNRS, CEA, University P. and M. Curie, F-91128 Palaiseau (France)

    2014-06-15

    Using hybrid simulations, we investigate the onset of fast reconnection between two cylindrical magnetic shells initially close to each other. This initial state mimics the plasma structure in High Energy Density Plasmas induced by a laser-target interaction and the associated self-generated magnetic field. We clearly observe that the classical quadrupolar structure of the out-of-plane magnetic field appears prior to the reconnection onset. Furthermore, a parametric study reveals that, with a non-coplanar initial magnetic topology, the reconnection onset is delayed and possibly suppressed. The relation between the out-of-plane magnetic field and the out-of-plane electric field is discussed.

  17. Impulsive nature in collisional driven reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Kitabata, Hideyuki; Hayashi, Takaya; Sato, Tetsuya

    1995-11-01

    Compressible magnetohydrodynamic simulation is carried out in order to investigate energy relaxation process of the driven magnetic reconnection in an open finite system through a long time calculation. It is found that a very impulsive energy release occurs in an intermittent fashion through magnetic reconnection for a continuous magnetic flux injection on the boundary. In the impulsive phase, the reconnection rate is remarkably enhanced up to more than ten times of the driving rate on the boundary. (author).

  18. Impulsive nature in collisional driven reconnection

    International Nuclear Information System (INIS)

    Kitabata, Hideyuki; Hayashi, Takaya; Sato, Tetsuya.

    1995-11-01

    Compressible magnetohydrodynamic simulation is carried out in order to investigate energy relaxation process of the driven magnetic reconnection in an open finite system through a long time calculation. It is found that a very impulsive energy release occurs in an intermittent fashion through magnetic reconnection for a continuous magnetic flux injection on the boundary. In the impulsive phase, the reconnection rate is remarkably enhanced up to more than ten times of the driving rate on the boundary. (author)

  19. A general hybrid kinetic-fluid model for collisionless magnetic reconnection

    International Nuclear Information System (INIS)

    Martinell, Julio J.

    2006-01-01

    A general set of equations appropriate for the description of the plasma dynamics within a collisionless magnetized plasma during the process of magnetic reconnection is derived. The particular geometry considered is that of a Harris pinch with a guide field and full kinetic equations for the perturbations are found, valid within the singular layer around the reconnecting region. Ion equations take into account finite Larmor radius effects while electron dynamics is based on the gyro-averaged drift kinetic equation. A more manageable model is obtained by resorting to fluid equations for the ions and retaining electron kinetic effects. It is shown that these equations give the same results obtained from the two-fluid theory in the limit of the collisionless tearing mode for different regimes

  20. Physics of collisionless reconnection in a stressed X-point collapse

    International Nuclear Information System (INIS)

    Tsiklauri, D.; Haruki, T.

    2008-01-01

    Recently, magnetic reconnection during collisionless, stressed, X-point collapse was studied using kinetic, 2.5-dimensional, fully electromagnetic, relativistic particle-in-cell numerical code [D. Tsiklauri and T. Haruki, Phys. Plasmas 14, 112905 (2007)]. Here we finalize the investigation of this topic by addressing key outstanding physical questions: (i) Which term in the generalized Ohm's law is responsible for the generation of the reconnection electric field? (ii) How does the time evolution of the reconnected flux vary with the ion-electron mass ratio? (iii) What is the exact energy budget of the reconnection process; i.e., in which proportion initial (mostly magnetic) energy is converted into other forms of energy? (iv) Are there any anisotropies in the velocity distribution of the accelerated particles? The following points have been established. (i) A reconnection electric field is generated by the electron pressure tensor off-diagonal terms, resembling to the case of tearing unstable Harris current sheet studied by the GEM reconnection challenge. (ii) For m i /m e >>1, the time evolution of the reconnected flux is independent of ion-electron mass ratio. In addition, in the case of m i /m e =1, we show that reconnection proceeds slowly as the Hall term is zero; when m i /m e >>1 (i.e., the Hall term is nonzero) reconnection is fast and we conjecture that this is due to magnetic field being frozen into electron fluid, which moves significantly faster than ion fluid. (iii) Within one Alfven time, somewhat less than half (∼40%) of the initial total (roughly magnetic) energy is converted into the kinetic energy of electrons, and somewhat more than half (∼60%) into kinetic energy of ions (similar to solar flare observations). (iv) In the strongly stressed X-point case, in about one Alfven time, a full isotropy in all three spatial directions of the velocity distribution is seen for superthermal electrons (also commensurate with solar flare observations).

  1. Role of compressibility on driven magnetic reconnection

    International Nuclear Information System (INIS)

    Sato, T.; Hayashi, T.; Watanabe, K.; Horiuchi, R.; Tanaka, M.; Sawairi, N.; Kusano, K.

    1991-08-01

    Whether it is induced by an ideal (current driven) instability or by an external force, plasma flow causes a change in the magnetic field configuration and often gives rise to a current intensification locally, thereby a fast driven reconnection being driven there. Many dramatic phenomena in magnetically confined plasmas such as magnetospheric substorms, solar flares, MHD self-organization and tokamak sawtooth crash, may be attributed to this fast driven reconnection. Using a fourth order MHD simulation code it is confirmed that compressibility of the plasma plays a crucial role in leading to a fast (MHD time scale) driven reconnection. This indicates that the incompressible representation is not always applicable to the study of a global dynamical behavior of a magnetically confined plasma. (author)

  2. Non-thermal particle acceleration in collisionless relativistic electron-proton reconnection

    Science.gov (United States)

    Werner, G. R.; Uzdensky, D. A.; Begelman, M. C.; Cerutti, B.; Nalewajko, K.

    2018-02-01

    Magnetic reconnection in relativistic collisionless plasmas can accelerate particles and power high-energy emission in various astrophysical systems. Whereas most previous studies focused on relativistic reconnection in pair plasmas, less attention has been paid to electron-ion plasma reconnection, expected in black hole accretion flows and relativistic jets. We report a comprehensive particle-in-cell numerical investigation of reconnection in an electron-ion plasma, spanning a wide range of ambient ion magnetizations σi, from the semirelativistic regime (ultrarelativistic electrons but non-relativistic ions, 10-3 ≪ σi ≪ 1) to the fully relativistic regime (both species are ultrarelativistic, σi ≫ 1). We investigate how the reconnection rate, electron and ion plasma flows, electric and magnetic field structures, electron/ion energy partitioning, and non-thermal particle acceleration depend on σi. Our key findings are: (1) the reconnection rate is about 0.1 of the Alfvénic rate across all regimes; (2) electrons can form concentrated moderately relativistic outflows even in the semirelativistic, small-σi regime; (3) while the released magnetic energy is partitioned equally between electrons and ions in the ultrarelativistic limit, the electron energy fraction declines gradually with decreased σi and asymptotes to about 0.25 in the semirelativistic regime; and (4) reconnection leads to efficient non-thermal electron acceleration with a σi-dependent power-law index, p(σ _i)˜eq const+0.7σ _i^{-1/2}. These findings are important for understanding black hole systems and lend support to semirelativistic reconnection models for powering non-thermal emission in blazar jets, offering a natural explanation for the spectral indices observed in these systems.

  3. Evidence of Magnetic Field Switch-off in Collisionless Magnetic Reconnection

    Science.gov (United States)

    Innocenti, M. E.; Goldman, M.; Newman, D.; Markidis, S.; Lapenta, G.

    2015-09-01

    The long-term evolution of large domain particle-in-cell simulations of collisionless magnetic reconnection is investigated following observations that show two possible outcomes for collisionless reconnection: toward a Petschek-like configuration or toward multiple X points. In the present simulation, a mixed scenario develops. At earlier time, plasmoids are emitted, disrupting the formation of Petschek-like structures. Later, an almost stationary monster plasmoid forms, preventing the emission of other plasmoids. A situation reminiscent of Petschek’s switch-off then ensues. Switch-off is obtained through a slow shock/rotational discontinuity compound structure. Two external slow shocks (SS) located at the separatrices reduce the in-plane tangential component of the magnetic field, but not to zero. Two transitions reminiscent of rotational discontinuities (RD) in the internal part of the exhaust then perform the final switch-off. Both the SS and the RD are characterized through analysis of their Rankine-Hugoniot jump conditions. A moderate guide field is used to suppress the development of the firehose instability in the exhaust.

  4. Disruption of Alfvénic turbulence by magnetic reconnection in a collisionless plasma

    Science.gov (United States)

    Mallet, Alfred; Schekochihin, Alexander A.; Chandran, Benjamin D. G.

    2017-12-01

    We calculate the disruption scale \\text{D}$ at which sheet-like structures in dynamically aligned Alfvénic turbulence are destroyed by the onset of magnetic reconnection in a low- collisionless plasma. The scaling of \\text{D}$ depends on the order of the statistics being considered, with more intense structures being disrupted at larger scales. The disruption scale for the structures that dominate the energy spectrum is \\text{D}\\sim L\\bot 1/9(de\\unicode[STIX]{x1D70C}s)4/9$ , where e$ is the electron inertial scale, s$ is the ion sound scale and \\bot $ is the outer scale of the turbulence. When e$ and s/L\\bot $ are sufficiently small, the scale \\text{D}$ is larger than s$ and there is a break in the energy spectrum at \\text{D}$ , rather than at s$ . We propose that the fluctuations produced by the disruption are circularised flux ropes, which may have already been observed in the solar wind. We predict the relationship between the amplitude and radius of these structures and quantify the importance of the disruption process to the cascade in terms of the filling fraction of undisrupted structures and the fractional reduction of the energy contained in them at the ion sound scale s$ . Both of these fractions depend strongly on e$ , with the disrupted structures becoming more important at lower e$ . Finally, we predict that the energy spectrum between \\text{D}$ and s$ is steeper than \\bot -3$ , when this range exists. Such a steep `transition range' is sometimes observed in short intervals of solar-wind turbulence. The onset of collisionless magnetic reconnection may therefore significantly affect the nature of plasma turbulence around the ion gyroscale.

  5. The inversion layer of electric fields and electron phase-space-hole structure during two-dimensional collisionless magnetic reconnection

    International Nuclear Information System (INIS)

    Chen Lijen; Lefebvre, Bertrand; Torbert, Roy B.; Daughton, William S.

    2011-01-01

    Based on two-dimensional fully kinetic simulations that resolve the electron diffusion layer in undriven collisionless magnetic reconnection with zero guide field, this paper reports the existence and evolution of an inversion layer of bipolar electric fields, its corresponding phase-space structure (an electron-hole layer), and the implication to collisionless dissipation. The inversion electric field layer is embedded in the layer of bipolar Hall electric field and extends throughout the entire length of the electron diffusion layer. The electron phase-space hole structure spontaneously arises during the explosive growth phase when there exist significant inflows into the reconnection layer, and electrons perform meandering orbits across the layer while being cyclotron-turned toward the outflow directions. The cyclotron turning of meandering electrons by the magnetic field normal to the reconnection layer is shown to be a primary factor limiting the current density in the region where the reconnection electric field is balanced by the gradient (along the current sheet normal) of the off-diagonal electron pressure-tensor.

  6. Coupling between reconnection and Kelvin-Helmholtz instabilities in collisionless plasmas

    Directory of Open Access Journals (Sweden)

    D. Grasso

    2009-04-01

    Full Text Available In a collisionless plasma, when reconnection instability takes place, strong shear flows may develop. Under appropriate conditions these shear flows become unstable to the Kelvin-Helmholtz instability. Here, we investigate the coupling between these instabilities in the framework of a four-field model. Firstly, we recover the known results in the low β limit, β being the ratio between the plasma and the magnetic pressure. We concentrate our attention on the dynamical evolution of the current density and vorticity sheets which evolve coupled together according to a laminar or a turbulent regime. A three-dimensional extension in this limit is also discussed. Secondly, we consider finite values of the β parameter, allowing for compression of the magnetic and velocity fields along the ignorable direction. We find that the current density and vorticity sheets now evolve separately. The Kelvin-Helmholtz instability involves only the vorticity field, which ends up in a turbulent regime, while the current density maintains a laminar structure.

  7. Slab magnetised non-relativistic low-beta electron-positron plasmas: collisionless heating, linear waves and reconnecting instabilities

    Science.gov (United States)

    Zocco, Alessandro

    2017-12-01

    The properties of a non-relativistic magnetised low-beta electron-positron plasma in slab geometry are investigated. The two species are taken to be drift kinetic while we retain Larmor radius effects in quasi-neutrality, and inertia in Ohm's law. A linear analysis shows that, for small magnetic perturbations, Alfvénic perturbations travel at the electron Alfvén speed, which is based on the electron mass. We discuss the role of the displacement current when Larmor-scale and Debye-scale effects are both retained. We predict the existence of a kinetic electron Alfvén wave which connects to the K-modes of Mishchenko et al. (J. Plasma Phys., 2017 (submitted)) in the electrostatic limit. It is found that linear drift waves are not supported by the system if the two species have the same temperature. Tearing modes can be driven unstable by equilibrium current density gradients. Also in this case, the characteristic time is based on the electron Alfvén speed. Nonlinear hybrid fluid-kinetic equations are also derived. It is shown that each species is described, to leading order, by the kinetic reduced electron heating model (KREHM) kinetic equation of Zocco & Schekochihin (Phys. Plasmas, vol. 18, 2011, 102309). The model is extended to retain first-order Larmor radius effects. It supports collisionless dispersive waves, which can greatly impact nonlinear magnetic reconnection. Diamagnetic effects enter the nonlinear equations via the first-order magnetic compressibility. A minimal nonlinear model for two-dimensional low-frequency isothermal pair plasmas is derived.

  8. Comparison of multi-fluid moment models with particle-in-cell simulations of collisionless magnetic reconnection

    International Nuclear Information System (INIS)

    Wang, Liang; Germaschewski, K.; Hakim, Ammar H.; Bhattacharjee, A.

    2015-01-01

    We introduce an extensible multi-fluid moment model in the context of collisionless magnetic reconnection. This model evolves full Maxwell equations and simultaneously moments of the Vlasov-Maxwell equation for each species in the plasma. Effects like electron inertia and pressure gradient are self-consistently embedded in the resulting multi-fluid moment equations, without the need to explicitly solving a generalized Ohm's law. Two limits of the multi-fluid moment model are discussed, namely, the five-moment limit that evolves a scalar pressures for each species and the ten-moment limit that evolves the full anisotropic, non-gyrotropic pressure tensor for each species. We first demonstrate analytically and numerically that the five-moment model reduces to the widely used Hall magnetohydrodynamics (Hall MHD) model under the assumptions of vanishing electron inertia, infinite speed of light, and quasi-neutrality. Then, we compare ten-moment and fully kinetic particle-in-cell (PIC) simulations of a large scale Harris sheet reconnection problem, where the ten-moment equations are closed with a local linear collisionless approximation for the heat flux. The ten-moment simulation gives reasonable agreement with the PIC results regarding the structures and magnitudes of the electron flows, the polarities and magnitudes of elements of the electron pressure tensor, and the decomposition of the generalized Ohm's law. Possible ways to improve the simple local closure towards a nonlocal fully three-dimensional closure are also discussed

  9. Study of driven magnetic reconnection in a laboratory plasma

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Masaaki; Ji, H.; Hsu, S.; Carter, T.; Kulsrud, R.; Bretz, N.; Jobes, F.; Ono, Yasushi; Perkins, F.

    1998-12-31

    The Magnetic Reconnection Experiment (MRX) has been constructed to investigate the fundamental physics of magnetic reconnection in a well controlled laboratory setting. This device creates an environment satisfying the criteria for a magnetohydrodynamic (MHD) plasma (S {much_gt} 1, {rho}{sub i} {much_lt} L). The boundary conditions can be controlled externally, and experiments with fully three-dimensional reconnection are now possible. In the initial experiments, the effects of the third vector component of reconnecting fields have been studied. Two distinctively different shapes of neutral sheet current layers, depending on the third component, are identified during driven magnetic reconnection. Without the third component (anti-parallel or null-helicity reconnection), a thin double-Y shaped diffusion region is identified. A neutral sheet current profile is measured accurately to be as narrow as order ion gyro-radius. In the presence of an appreciable third component (co-helicity reconnection), an O-shaped diffusion region appears and grows into a spheromak configuration.

  10. Effects of a Guide Field on the Larmor Electric Field and Upstream Electron Temperature Anisotropy in Collisionless Asymmetric Magnetic Reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Ek-In, Surapat; Ruffolo, David [Department of Physics, Faculty of Science, Mahidol University, Bangkok (Thailand); Malakit, Kittipat [Department of Physics, Faculty of Science and Techonology, Thammasat University, Pathum Thani (Thailand); Shay, Michael A. [Department of Physics and Astronomy, University of Delaware, Newark, DE (United States); Cassak, Paul A., E-mail: kmalakit@gmail.com [Department of Physics and Astronomy, West Virginia University, Morgantown, WV (United States)

    2017-08-20

    We perform the first study of the properties of the Larmor electric field (LEF) in collisionless asymmetric magnetic reconnection in the presence of an out-of-plane (guide) magnetic field for different sets of representative upstream parameters at Earth’s dayside magnetopause with an ion temperature greater than the electron temperature (the ion-to-electron temperature ratio fixed at 2) using two-dimensional particle-in-cell simulations. We show that the LEF does persist in the presence of a guide field. We study how the LEF thickness and strength change as a function of guide field and the magnetospheric temperature and reconnecting magnetic field strength. We find that the thickness of the LEF structure decreases, while its magnitude increases when a guide field is added to the reconnecting magnetic field. The added guide field makes the Larmor radius smaller, so the scaling with the magnetospheric ion Larmor radius is similar to that reported for the case without a guide field. Note, however, that the physics causing the LEF is not well understood, so future work in other parameter regimes is needed to fully predict the LEF for arbitrary conditions. We also find that a previously reported upstream electron temperature anisotropy arises in the vicinity of the LEF region both with and without a guide field. We argue that the generation of the anisotropy is linked to the existence of the LEF. The LEF can be used in combination with the electron temperature anisotropy as a signature to effectively identify dayside reconnection sites in observations.

  11. Three-Dimensional Collisionless Magnetic Reconnection: Simulation With a Particle Electromagnetic Code

    Science.gov (United States)

    Scholer, M.; Sidorenko, I.; Jaroschek, C.; Treumann, R. A.; Zeiler, A.

    2002-12-01

    We have investigated the onset of reconnection in thin current sheets by means of three-dimensional full particle (PIC) simulations. Instead of imposing reconnection ab initio, reconnection is allowed to develop out of the numerical noise. We do not impose symmetry about the midplane, so that the drift kink instability, the Kelvin-Helmholtz instability, and the sausage instability are allowed for, and we use a high mass ratio of mi/m_e=160. The system is double periodic with two current sheets, which limits the time reconnection can proceed, but simplifies the boundary conditions. Two cases are investigated: (1) a thin current sheet with exactly antiparallel fields, and (2) a thin current sheet with a guide field of the same order as the antiparallel field. In case (1) the lower hybrid drift instability (LHDI) is excited and leads to current sheet thinning. Subsequently, patchy reconnection sets in, and arranges itself within a few ion times into a single neutral line. In case (2) the onset of reconnection is delayed, but eventually a single neutral line emerges. No sausage mode or kink mode, respectively, preceed in either case the onset of reconnection. After a single neutral line has evolved it kinks in the current direction.

  12. Magnetic Reconnection Driven by Thermonuclear Burning

    Science.gov (United States)

    Gatto, R.; Coppi, B.

    2017-10-01

    Considering that fusion reaction products (e.g. α-particles) deposit their energy on the electrons, the relevant thermal energy balance equation is characterized by a fusion source term, a relatively large longitudinal thermal conductivity and an appropriate transverse thermal conductivity. Then, looking for modes that are radially localized around rational surfaces, reconnected field configurations are found that can be sustained by the electron thermal energy source due to fusion reactions. Then this process can be included in the category of endogenous reconnection processes and may be viewed as a form of the thermonuclear instability that can develop in an ignited inhomogeneous plasma. A complete analysis of the equations supporting the relevant theory is reported. Sponsored in part by the U.S. DoE.

  13. An experimental platform for pulsed-power driven magnetic reconnection

    Science.gov (United States)

    Hare, J. D.; Suttle, L. G.; Lebedev, S. V.; Loureiro, N. F.; Ciardi, A.; Chittenden, J. P.; Clayson, T.; Eardley, S. J.; Garcia, C.; Halliday, J. W. D.; Robinson, T.; Smith, R. A.; Stuart, N.; Suzuki-Vidal, F.; Tubman, E. R.

    2018-05-01

    We describe a versatile pulsed-power driven platform for magnetic reconnection experiments, based on the exploding wire arrays driven in parallel [Suttle et al., Phys. Rev. Lett. 116, 225001 (2016)]. This platform produces inherently magnetised plasma flows for the duration of the generator current pulse (250 ns), resulting in a long-lasting reconnection layer. The layer exists for long enough to allow the evolution of complex processes such as plasmoid formation and movement to be diagnosed by a suite of high spatial and temporal resolution laser-based diagnostics. We can access a wide range of magnetic reconnection regimes by changing the wire material or moving the electrodes inside the wire arrays. We present results with aluminium and carbon wires, in which the parameters of the inflows and the layer that forms are significantly different. By moving the electrodes inside the wire arrays, we change how strongly the inflows are driven. This enables us to study both symmetric reconnection in a range of different regimes and asymmetric reconnection.

  14. Collisionless magnetic reconnection in large-scale electron-positron plasmas

    International Nuclear Information System (INIS)

    Daughton, William; Karimabadi, Homa

    2007-01-01

    One of the most fundamental questions in reconnection physics is how the dynamical evolution will scale to macroscopic systems of physical relevance. This issue is examined for electron-positron plasmas using two-dimensional fully kinetic simulations with both open and periodic boundary conditions. The resulting evolution is complex and highly dynamic throughout the entire duration. The initial phase is distinguished by the coalescence of tearing islands to larger scale while the later phase is marked by the expansion of diffusion regions into elongated current layers that are intrinsically unstable to plasmoid generation. It appears that the repeated formation and ejection of plasmoids plays a key role in controlling the average structure of a diffusion region and preventing the further elongation of the layer. The reconnection rate is modulated in time as the current layers expand and new plasmoids are formed. Although the specific details of this evolution are affected by the boundary and initial conditions, the time averaged reconnection rate remains fast and is remarkably insensitive to the system size for sufficiently large systems. This dynamic scenario offers an alternative explanation for fast reconnection in large-scale systems

  15. Electron-inertia effects on driven magnetic field reconnection

    International Nuclear Information System (INIS)

    Al-Salti, N.; Shivamoggi, B.K.

    2003-01-01

    Electron-inertia effects on the magnetic field reconnection induced by perturbing the boundaries of a slab of plasma with a magnetic neutral surface inside are considered. Energetics of the tearing mode dynamics with electron inertia which controls the linearized collisionless magnetohydrodynamics (MHD) are considered with a view to clarify the role of the plasma pressure in this process. Cases with the boundaries perturbed at rates slow or fast compared with the hydromagnetic evolution rate are considered separately. When the boundaries are perturbed at a rate slow compared with the hydromagnetic evolution rate and fast compared with the resistive diffusion rate, the plasma response for early times is according to ideal MHD. A current sheet formation takes place at the magnetic neutral surface for large times in the ideal MHD stage and plasma becomes motionless. The subsequent evolution of the current sheet is found to be divided into two distinct stages: (i) the electron-inertia stage for small times (when the current sheet is very narrow); (ii) the resistive-diffusion stage for large times. The current sheet mainly undergoes exponential damping in the electron-inertia regime while the bulk of the diffusion happens in the resistivity regime. For large times of the resistive-diffusion stage when plasma flow is present, the current sheet completely disappears and the magnetic field reconnection takes place. When the boundaries are perturbed at a rate fast compared even with the hydromagnetic evolution rate, there is no time for the development of a current sheet and the magnetic field reconnection has been found not to take place

  16. Wave driven magnetic reconnection in the Taylor problem

    International Nuclear Information System (INIS)

    Fitzpatrick, Richard; Bhattacharjee, Amitava; Ma Zhiwei; Linde, Timur

    2003-01-01

    An improved Laplace transform theory is developed in order to investigate the initial response of a stable slab plasma equilibrium enclosed by conducting walls to a suddenly applied wall perturbation in the so-called Taylor problem. The novel feature of this theory is that it does not employ asymptotic matching. If the wall perturbation is switched on slowly compared to the Alfven time then the plasma response eventually asymptotes to that predicted by conventional asymptotic matching theory. However, at early times there is a compressible Alfven wave driven contribution to the magnetic reconnection rate which is not captured by asymptotic matching theory, and leads to a significant increase in the reconnection rate. If the wall perturbation is switched on rapidly compared to the Alfven time then strongly localized compressible Alfven wave-pulses are generated which bounce backward and forward between the walls many times. Each instance these wave-pulses cross the resonant surface they generate a transient surge in the reconnection rate. The maximum pulse driven reconnection rate can be much larger than that predicted by conventional asymptotic matching theory

  17. Weibel instability mediated collisionless shocks using intense laser-driven plasmas

    Science.gov (United States)

    Palaniyappan, Sasikumar; Fiuza, Federico; Huang, Chengkun; Gautier, Donald; Ma, Wenjun; Schreiber, Jorg; Raymer, Abel; Fernandez, Juan; Shimada, Tom; Johnson, Randall

    2017-10-01

    The origin of cosmic rays remains a long-standing challenge in astrophysics and continues to fascinate physicists. It is believed that ``collisionless shocks'' - where the particle Coulomb mean free path is much larger that the shock transition - are a dominant source of energetic cosmic rays. These shocks are ubiquitous in astrophysical environments such as gamma-ray bursts, supernova remnants, pulsar wind nebula and coronal mass ejections from the sun. A particular type of electromagnetic plasma instability known as Weibel instability is believed to be the dominant mechanism behind the formation of these collisionless shocks in the cosmos. The understanding of the microphysics behind collisionless shocks and their particle acceleration is tightly related with nonlinear basic plasma processes and remains a grand challenge. In this poster, we will present results from recent experiments at the LANL Trident laser facility studying collisionless shocks using intense ps laser (80J, 650 fs - peak intensity of 1020 W/cm2) driven near-critical plasmas using carbon nanotube foam targets. A second short pulse laser driven protons from few microns thick gold foil is used to radiograph the main laser-driven plasma. Work supported by the LDRD program at LANL.

  18. The Current-Driven, Ion-Acoustic Instability in a Collisionless Plasma

    DEFF Research Database (Denmark)

    Michelsen, Poul; Pécseli, Hans; Juul Rasmussen, Jens

    1979-01-01

    The current-driven, ion-acoustic instability was investigated by means of an experiment performed in a collisionless plasma produced in a single-ended Q-machine. Reflections at the ends of the plasma column gave rise to a standing wave. Parameters of the instability were investigated, and it was ......, and it was demonstrated that the fluctuations in the plasma column behave as a classical Van der Pol oscillator. Accurate measurements of the growth rate of the instability can be performed by making explicit use of the particular properties of such a system.......The current-driven, ion-acoustic instability was investigated by means of an experiment performed in a collisionless plasma produced in a single-ended Q-machine. Reflections at the ends of the plasma column gave rise to a standing wave. Parameters of the instability were investigated...

  19. Laser-driven, magnetized quasi-perpendicular collisionless shocks on the Large Plasma Device

    Energy Technology Data Exchange (ETDEWEB)

    Schaeffer, D. B., E-mail: dschaeffer@physics.ucla.edu; Everson, E. T.; Bondarenko, A. S.; Clark, S. E.; Constantin, C. G.; Vincena, S.; Van Compernolle, B.; Tripathi, S. K. P.; Gekelman, W.; Niemann, C. [Department of Physics and Astronomy, University of California - Los Angeles, Los Angeles, California 90095 (United States); Winske, D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2014-05-15

    The interaction of a laser-driven super-Alfvénic magnetic piston with a large, preformed magnetized ambient plasma has been studied by utilizing a unique experimental platform that couples the Raptor kJ-class laser system [Niemann et al., J. Instrum. 7, P03010 (2012)] to the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the University of California, Los Angeles. This platform provides experimental conditions of relevance to space and astrophysical magnetic collisionless shocks and, in particular, allows a detailed study of the microphysics of shock formation, including piston-ambient ion collisionless coupling. An overview of the platform and its capabilities is given, and recent experimental results on the coupling of energy between piston and ambient ions and the formation of collisionless shocks are presented and compared to theoretical and computational work. In particular, a magnetosonic pulse consistent with a low-Mach number collisionless shock is observed in a quasi-perpendicular geometry in both experiments and simulations.

  20. Bifurcation Theory of the Transition to Collisionless Ion-temperature-gradient-driven Plasma Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Kolesnikov, R.A.; Krommes, J.A.

    2005-09-22

    The collisionless limit of the transition to ion-temperature-gradient-driven plasma turbulence is considered with a dynamical-systems approach. The importance of systematic analysis for understanding the differences in the bifurcations and dynamics of linearly damped and undamped systems is emphasized. A model with ten degrees of freedom is studied as a concrete example. A four-dimensional center manifold (CM) is analyzed, and fixed points of its dynamics are identified and used to predict a ''Dimits shift'' of the threshold for turbulence due to the excitation of zonal flows. The exact value of that shift in terms of physical parameters is established for the model; the effects of higher-order truncations on the dynamics are noted. Multiple-scale analysis of the CM equations is used to discuss possible effects of modulational instability on scenarios for the transition to turbulence in both collisional and collisionless cases.

  1. Intense laser driven collision-less shock and ion acceleration in magnetized plasmas

    Science.gov (United States)

    Mima, K.; Jia, Q.; Cai, H. B.; Taguchi, T.; Nagatomo, H.; Sanz, J. R.; Honrubia, J.

    2016-05-01

    The generation of strong magnetic field with a laser driven coil has been demonstrated by many experiments. It is applicable to the magnetized fast ignition (MFI), the collision-less shock in the astrophysics and the ion shock acceleration. In this paper, the longitudinal magnetic field effect on the shock wave driven by the radiation pressure of an intense short pulse laser is investigated by theory and simulations. The transition of a laminar shock (electro static shock) to the turbulent shock (electromagnetic shock) occurs, when the external magnetic field is applied in near relativistic cut-off density plasmas. This transition leads to the enhancement of conversion of the laser energy into high energy ions. The enhancement of the conversion efficiency is important for the ion driven fast ignition and the laser driven neutron source. It is found that the total number of ions reflected by the shock increases by six time when the magnetic field is applied.

  2. Simulation study of magnetic reconnection

    International Nuclear Information System (INIS)

    Horiuchi, Ritoku

    1998-01-01

    Dynamical process of collisionless driven reconnection is investigated by means of a two-and-one-half-dimensional particle simulation. Magnetic reconnection develops in two steps in accordance with the formation of ion and electron current layers. The dominant triggering mechanism for electron phase changes from electron meandering motion effect to electron inertia effect as a longitudinal magnetic field increases. It is also found that the energy conversion takes place from electrons to ions through the action of an electrostatic field excited in the downstream and thus the average ion temperature becomes about 1.5 of the average electron temperature. (author)

  3. A simulation of driven reconnection by a high precision MHD code

    International Nuclear Information System (INIS)

    Kusano, Kanya; Ouchi, Yasuo; Hayashi, Takaya; Horiuchi, Ritoku; Watanabe, Kunihiko; Sato, Tetsuya.

    1988-01-01

    A high precision MHD code, which has the fourth-order accuracy for both the spatial and time steps, is developed, and is applied to the simulation studies of two dimensional driven reconnection. It is confirm that the numerical dissipation of this new scheme is much less than that of two-step Lax-Wendroff scheme. The effect of the plasma compressibility on the reconnection dynamics is investigated by means of this high precision code. (author)

  4. A RECONNECTION-DRIVEN RAREFACTION WAVE MODEL FOR CORONAL OUTFLOWS

    International Nuclear Information System (INIS)

    Bradshaw, S. J.; Aulanier, G.; Del Zanna, G.

    2011-01-01

    We conduct numerical experiments to determine whether interchange reconnection at high altitude coronal null points can explain the outflows observed as blueshifts in coronal emission lines at the boundaries between open and closed magnetic field regions. In this scenario, a strong, post-reconnection pressure gradient forms in the field-aligned direction when dense and hot, active region core loops reconnect with neighboring tenuous and cool, open field lines. We find that the pressure gradient drives a supersonic outflow and a rarefaction wave develops in both the open and closed post-reconnection magnetic field regions. We forward-model the spectral line profiles for a selection of coronal emission lines to predict the spectral signatures of the rarefaction wave. We find that the properties of the rarefaction wave are consistent with the observed velocity versus temperature structure of the corona in the outflow regions, where the velocity increases with the formation temperature of the emission lines. In particular, we find excellent agreement between the predicted and observed Fe XII 195.119 Å spectral line profiles in terms of the blueshift (10 km s –1 ), full width at half-maximum (83 mÅ) and symmetry. Finally, we find that T i e in the open field region, which indicates that the interchange reconnection scenario may provide a viable mechanism and source region for the slow solar wind.

  5. Collisionless Kelvin-Helmholtz instability and vortex-induced reconnection in the external region of the Earth magnetotail

    International Nuclear Information System (INIS)

    Pegoraro, F; Faganello, M; Califano, F

    2008-01-01

    In a magnetized plasma streaming with a non uniform velocity, the Kelvin-Helmholtz instability plays a major role in mixing different plasma regions and in stretching the magnetic field lines leading to the formation of layers with a sheared magnetic field where magnetic field line reconnection can take place. A relevant example is provided by the formation of a mixing layer between the Earth's magnetosphere and the solar wind at low latitudes during northward periods. In the considered configuration, in the presence of a magnetic field nearly perpendicular to the plane defined by the velocity field and its inhomogeneity direction, velocity shear drives a Kelvin-Helmholtz instability which advects and distorts the magnetic field configuration. If the Alfven velocity associated to the in-plane magnetic field is sufficiently weak with respect to the variation of the fluid velocity in the plasma, the Kelvin-Helmholtz instability generates fully rolled-up vortices which advect the magnetic field lines into a complex configuration, causing the formation of current layers along the inversion curves of the in-plane magnetic field component. Pairing of the vortices generated by the Kelvin-Helmholtz instability is a well know phenomenon in two-dimensional hydrodynamics. Here we investigate the development of magnetic reconnection during the vortex pairing process and show that completely different magnetic structures are produced depending on how fast the reconnection process develops on the time scale set by the pairing process.

  6. 3-D magnetic reconnection in colliding laser-produced plasmas

    Science.gov (United States)

    Matteucci, Jackson; Fox, Will; Moissard, Clement; Bhattacharjee, Amitava

    2017-10-01

    Recent experiments have demonstrated magnetic reconnection between colliding plasma plumes, where the reconnecting magnetic fields were self-generated in the expanding laser-produced plasmas by the Biermann battery effect. Using fully kinetic 3-D particle in cell simulations, we conduct the first end-to-end simulations of these experiments, including self-consistent magnetic field generation via the Biermann effect through driven magnetic field reconnection. The simulations show rich, temporally and spatially dependent magnetic field reconnection. First, we find fast, vertically-localized ``Biermann-mediated reconnection,'' an inherently 3-D reconnection mechanism where the sign of the Biermann term reverses in the reconnection layer, destroying incoming flux and reconnecting flux downstream. Reconnection then transitions to fast, collisionless reconnection sustained by the non-gyrotropic pressure tensor. To separate out the role 3-D mechanisms, 2-D simulations are initialized based on reconnection-plane cuts of the 3-D simulations. These simulations demonstrate: (1) suppression of Biermann-mediated reconnection in 2-D; (2) similar efficacy of pressure tensor mechanisms in 2-D and 3-D; and (3) plasmoids develop in the reconnection layer in 2-D, where-as they are suppressed in 3-D. Supported by NDSEG Fellowship. This research used resources of the OLCF at ORNL, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.

  7. Final Scientific/Technical Report for "Role of Electron Kinetic Effects on the Macroscopic Structure and Evolution of Collisionless Reconnection in Simulations with Open Boundary Conditions"

    Energy Technology Data Exchange (ETDEWEB)

    Scudder, Jack

    2011-02-04

    The final years of this grant have been dedicated to diagnosing the observable properties of Collisionless Magnetic Reconnection (CMR) as disclosed by the open boundary condition PIC simulations developed under this grant. Particular attention has focussed on identifying the Electron Diffusion Region (EDR), the short scale domain where the process is thought to be enabled. The critical issue has been the need for experimental closure for CMR that is widely invoked in astrophysics, but has actually rather little direct, incontrovertible evidence for its involvement. This difficulty arises because CMR is about topology change of the magnetic field - a concept that is not conducive to single, or even few point correlations as are beginning to be possible with spacecraft armada, like Cluster or the planned Magnetospheric Multi-Scale (MMS) mission to be launched in 2014. Alternate formulations about the time rate of magnetic flux inventoried by a moving observer, reformulate the needed evidence in terms of the curl of various weak vector fields, such as E+UexB, that is zero in ideal MHD. To sense E+UexB from space measurements is already a heroic task. The curl of such a small vector field is outside the domain of the possible.

  8. Power-law Statistics of Driven Reconnection in the Magnetically Closed Corona

    Science.gov (United States)

    Knizhnik, K. J.; Uritsky, V. M.; Klimchuk, J. A.; DeVore, C. R.

    2018-01-01

    Numerous observations have revealed that power-law distributions are ubiquitous in energetic solar processes. Hard X-rays, soft X-rays, extreme ultraviolet radiation, and radio waves all display power-law frequency distributions. Since magnetic reconnection is the driving mechanism for many energetic solar phenomena, it is likely that reconnection events themselves display such power-law distributions. In this work, we perform numerical simulations of the solar corona driven by simple convective motions at the photospheric level. Using temperature changes, current distributions, and Poynting fluxes as proxies for heating, we demonstrate that energetic events occurring in our simulation display power-law frequency distributions, with slopes in good agreement with observations. We suggest that the braiding-associated reconnection in the corona can be understood in terms of a self-organized criticality model driven by convective rotational motions similar to those observed at the photosphere.

  9. INJECTION OF PLASMA INTO THE NASCENT SOLAR WIND VIA RECONNECTION DRIVEN BY SUPERGRANULAR ADVECTION

    International Nuclear Information System (INIS)

    Yang Liping; He Jiansen; Tu Chuanyi; Chen Wenlei; Zhang Lei; Wang Linghua; Yan Limei; Peter, Hardi; Marsch, Eckart; Feng, Xueshang

    2013-01-01

    To understand the origin of the solar wind is one of the key research topics in modern solar and heliospheric physics. Previous solar wind models assumed that plasma flows outward along a steady magnetic flux tube that reaches continuously from the photosphere through the chromosphere into the corona. Inspired by more recent comprehensive observations, Tu et al. suggested a new scenario for the origin of the solar wind, in which it flows out in a magnetically open coronal funnel and mass is provided to the funnel by small-scale side loops. Thus mass is supplied by means of magnetic reconnection that is driven by supergranular convection. To validate this scenario and simulate the processes involved, a 2.5 dimensional (2.5D) numerical MHD model is established in the present paper. In our simulation a closed loop moves toward an open funnel, which has opposite polarity and is located at the edge of a supergranulation cell, and magnetic reconnection is triggered and continues while gradually opening up one half of the closed loop. Its other half connects with the root of the open funnel and forms a new closed loop which is submerged by a reconnection plasma stream flowing downward. Thus we find that the outflowing plasma in the newly reconnected funnel originates not only from the upward reconnection flow but also from the high-pressure leg of the originally closed loop. This implies an efficient supply of mass from the dense loop to the dilute funnel. The mass flux of the outflow released from the funnel considered in our study is calculated to be appropriate for providing the mass flux at the coronal base of the solar wind, though additional heating and acceleration mechanisms are necessary to keep the velocity at the higher location. Our numerical model demonstrates that in the funnel the mass for the solar wind may be supplied from adjacent closed loops via magnetic reconnection as well as directly from the footpoints of open funnels.

  10. Anomalous heating and plasmoid formation in pulsed power driven magnetic reconnection experiments

    Science.gov (United States)

    Hare, Jack

    2017-10-01

    Magnetic reconnection is an important process occurring in various plasma environments, including high energy density plasmas. In this talk we will present results from a recently developed magnetic reconnection platform driven by the MAGPIE pulsed power generator (1 MA, 250 ns) at Imperial College London. In these experiments, supersonic, sub-Alfvénic plasma flows collide, bringing anti-parallel magnetic fields into contact and producing a well-defined, elongated reconnection layer. This layer is long-lasting (>200 ns, > 10 hydrodynamic flow times) and is diagnosed using a suite of high resolution, spatially and temporally resolved diagnostics which include laser interferometry, Thomson scattering and Faraday rotation imaging. We observe significant heating of the electrons and ions inside the reconnection layer, and calculate that the heating must occur on time-scales far faster than can be explained by classical mechanisms. Possible anomalous mechanisms include in-plane electric fields caused by two-fluid effects, and enhanced resistivity and viscosity caused by kinetic turbulence. We also observe the repeated formation of plasmoids in the reconnection layer, which are ejected outwards along the layer at super-Alfvénic velocities. The O-point magnetic field structure of these plasmoids is determined using in situ magnetic probes, and these plasmoids could also play a role in the anomalous heating of the electrons and ions. In addition, we present further modifications to this experimental platform which enable us to study asymmetric reconnection or measure the out-of-plane magnetic field inside the plasmoids. This work was supported in part by the Engineering and Physical Sciences Research Council (EPSRC) Grant No. EP/N013379/1, and by the U.S. Department of Energy (DOE) Awards No. DE-F03-02NA00057 and No. DE-SC-0001063.

  11. X-Ray Imaging of Ultrafast Magnetic Reconnection Driven by Relativistic Electrons

    Science.gov (United States)

    Raymond, Anthony; McKelvey, Andrew; Zulick, Calvin; Maksimchuk, Anatoly; Thomas, Alexander; Willingale, Louise; Chvykov, Vladimir; Yanovsky, Victor; Krushelnick, Karl

    2014-10-01

    Magnetic reconnection events driven by relativistic electrons are observed between two high intensity laser/plasma interaction sites. The two laser focuses were on average 20 μm FWHM containing 50 TW of power each, delivered with a split f/3 paraboloid onto copper foil targets at a focused intensity of 4×1018 W/cm2. A spherically bent k-alpha X-ray Bragg crystal was utilized to image the interactions, and by motorizing one half of the paraboloid vertically the focal separation was varied between 0-200 μm. While these k-alpha images demonstrated a ring structure surrounding a single focus (due to electrons returning from vacuum to the rear of the target surface), splitting the focuses revealed the rings of either spot interacting and enhancing between the focuses, evidencing magnetic reconnection driven by the relativistic electron currents. Imaging the transversely propagating electrons with a filtered LANEX screen demonstrated relativistic currents with spatial nonuniformities potentially directly originating from reconnection events, and varying target geometries were used to investigate the resulting effects on the spatial electron profiles. At present PIC simulations are being conducted to better understand and attempt to reproduce the measured electron outflow dynamics. Currently at: ELI Attosecond Light Pulse Source.

  12. Externally-Driven Onset of Localized Magnetic Reconnection in a Magnetotail Configuration

    Science.gov (United States)

    Pritchett, P. L.; Lu, S.

    2017-12-01

    In observations of the nightside auroral arcs and ionospheric currents, the onset or breakup phase of a substorm is sharply defined in time and is highly localized in space. Attempts to understand this localization in terms of the onset of localized magnetic reconnection have generally been unsuccessful. Thus, a y-localized driving convection electric field Ey applied at the lobe boundaries spreads out before it reaches the equatorial plane and results only in 2-D reconnection. In this work, the response of a magnetotail equilibrium containing a dipole magnetic field and plasma sheet regions to the imposition of a longitudinally-limited, high-latitude driving electric field is investigated using 3-D particle-in-cell simulations. The initial response involves a reduction in the equatorial Bz field that is then followed by the development of a dawn-dusk asymmetric current sheet relative to the meridian plane of the driving field. The key feature is the presence of a dusk-side Hall electric field Ez that drives magnetic flux dawnward and thus further reduces the Bz field on the duskward side. The net result is that Bz is driven through zero in a localized region on the duskward side, leading to the onset of localized reconnection and the emergence of magnetic flux ropes. The cross-tail extent of the reconnection expands but remains limited to ˜30di, where di is the ion inertia length. The dissipation E' \\cdot J is peaked along the finite X line, with a load region (negative E' \\cdot J) forming tailward of this region. The particle energy spectra in the downtail region show shoulders for the ions in the energy range ˜3-8Eth (Eth is the initial thermal energy) and extended tails for the electrons in the range ˜10-20Eth. These results demonstrate the ability of a high-latitude disturbance that may be connected to dayside flow channels [Nishimura et al., 2014] to initiate localized magnetic reconnection in the magnetotail.

  13. Experimental study of subcritical laboratory magnetized collisionless shocks using a laser-driven magnetic piston

    Energy Technology Data Exchange (ETDEWEB)

    Schaeffer, D. B., E-mail: dschaeffer@physics.ucla.edu; Everson, E. T.; Bondarenko, A. S.; Clark, S. E.; Constantin, C. G.; Gekelman, W.; Niemann, C. [Department of Physics and Astronomy, University of California—Los Angeles, Los Angeles, California 90095 (United States); Winske, D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2015-11-15

    Recent experiments at the University of California, Los Angeles have successfully generated subcritical magnetized collisionless shocks, allowing new laboratory studies of shock formation relevant to space shocks. The characteristics of these shocks are compared with new data in which no shock or a pre-shock formed. The results are consistent with theory and 2D hybrid simulations and indicate that the observed shock or shock-like structures can be organized into distinct regimes by coupling strength. With additional experiments on the early time parameters of the laser plasma utilizing Thomson scattering, spectroscopy, and fast-gate filtered imaging, these regimes are found to be in good agreement with theoretical shock formation criteria.

  14. Reconnection-driven Magnetohydrodynamic Turbulence in a Simulated Coronal-hole Jet

    Energy Technology Data Exchange (ETDEWEB)

    Uritsky, Vadim M.; Roberts, Merrill A. [Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064 (United States); DeVore, C. Richard; Karpen, Judith T., E-mail: vadim.uritsky@nasa.gov [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2017-03-10

    Extreme-ultraviolet and X-ray jets occur frequently in magnetically open coronal holes on the Sun, especially at high solar latitudes. Some of these jets are observed by white-light coronagraphs as they propagate through the outer corona toward the inner heliosphere, and it has been proposed that they give rise to microstreams and torsional Alfvén waves detected in situ in the solar wind. To predict and understand the signatures of coronal-hole jets, we have performed a detailed statistical analysis of such a jet simulated by an adaptively refined magnetohydrodynamics model. The results confirm the generation and persistence of three-dimensional, reconnection-driven magnetic turbulence in the simulation. We calculate the spatial correlations of magnetic fluctuations within the jet and find that they agree best with the Müller–Biskamp scaling model including intermittent current sheets of various sizes coupled via hydrodynamic turbulent cascade. The anisotropy of the magnetic fluctuations and the spatial orientation of the current sheets are consistent with an ensemble of nonlinear Alfvén waves. These properties also reflect the overall collimated jet structure imposed by the geometry of the reconnecting magnetic field. A comparison with Ulysses observations shows that turbulence in the jet wake is in quantitative agreement with that in the fast solar wind.

  15. Toward multi-scale simulation of reconnection phenomena in space plasma

    Science.gov (United States)

    Den, M.; Horiuchi, R.; Usami, S.; Tanaka, T.; Ogawa, T.; Ohtani, H.

    2013-12-01

    Magnetic reconnection is considered to play an important role in space phenomena such as substorm in the Earth's magnetosphere. It is well known that magnetic reconnection is controlled by microscopic kinetic mechanism. Frozen-in condition is broken due to particle kinetic effects and collisionless reconnection is triggered when current sheet is compressed as thin as ion kinetic scales under the influence of external driving flow. On the other hand configuration of the magnetic field leading to formation of diffusion region is determined in macroscopic scale and topological change after reconnection is also expressed in macroscopic scale. Thus magnetic reconnection is typical multi-scale phenomenon and microscopic and macroscopic physics are strongly coupled. Recently Horiuchi et al. developed an effective resistivity model based on particle-in-cell (PIC) simulation results obtained in study of collisionless driven reconnection and applied to a global magnetohydrodynamics (MHD) simulation of substorm in the Earth's magnetosphere. They showed reproduction of global behavior in substrom such as dipolarization and flux rope formation by global three dimensional MHD simulation. Usami et al. developed multi-hierarchy simulation model, in which macroscopic and microscopic physics are solved self-consistently and simultaneously. Based on the domain decomposition method, this model consists of three parts: a MHD algorithm for macroscopic global dynamics, a PIC algorithm for microscopic kinetic physics, and an interface algorithm to interlock macro and micro hierarchies. They verified the interface algorithm by simulation of plasma injection flow. In their latest work, this model was applied to collisionless reconnection in an open system and magnetic reconnection was successfully found. In this paper, we describe our approach to clarify multi-scale phenomena and report the current status. Our recent study about extension of the MHD domain to global system is presented. We

  16. Experimental Verification of the Hall Effect during Magnetic Reconnection in a Laboratory Plasma

    International Nuclear Information System (INIS)

    Yang Ren; Masaaki Yamada; Stefan Gerhardt; Hantao Ji; Russell Kulsrud; Aleksey Kuritsyn

    2005-01-01

    In this letter we report a clear and unambiguous observation of the out-of-plane quadrupole magnetic field suggested by numerical simulations in the reconnecting current sheet in the Magnetic Reconnection Experiment (MRX). Measurements show that the Hall effect is large in collisionless regime and becomes small as the collisionality increases, indicating that the Hall effect plays an important role in collisionless reconnection

  17. Collisionless current sheet equilibria

    Science.gov (United States)

    Neukirch, T.; Wilson, F.; Allanson, O.

    2018-01-01

    Current sheets are important for the structure and dynamics of many plasma systems. In space and astrophysical plasmas they play a crucial role in activity processes, for example by facilitating the release of magnetic energy via processes such as magnetic reconnection. In this contribution we will focus on collisionless plasma systems. A sensible first step in any investigation of physical processes involving current sheets is to find appropriate equilibrium solutions. The theory of collisionless plasma equilibria is well established, but over the past few years there has been a renewed interest in finding equilibrium distribution functions for collisionless current sheets with particular properties, for example for cases where the current density is parallel to the magnetic field (force-free current sheets). This interest is due to a combination of scientific curiosity and potential applications to space and astrophysical plasmas. In this paper we will give an overview of some of the recent developments, discuss their potential applications and address a number of open questions.

  18. Kinetic-scale flux rope reconnection in periodic and line-tied geometries

    Science.gov (United States)

    Sauppe, J. P.; Daughton, W.

    2018-01-01

    The collisionless reconnection of two parallel flux ropes driven by both the coalescence and kink instabilities is examined using fully kinetic simulations in periodic and line-tied geometries. The three-dimensional reconnection rate is computed from the maximum of the quasi-potential, Ξ ≡ - ∫ E . d ℓ , where the integral of the electric field is taken along the magnetic field lines across the system. In periodic simulations in which the kink mode is nearly suppressed, reconnection is driven by the coalescence instability, and the peak rate is within 3%-8% of comparable 2D simulations. When a strong kink growth is observed, the peak reconnection rate drops by 10%-25%, and there is a larger drop for lower guide field. With line-tied boundary conditions, the kink instability plays a key role in allowing the flux ropes to interact and partially reconnect. In this limit, the field lines with maximum quasi-potential are associated with a quasi-separatrix layer, and the electric field along these special field lines is supported predominantly by the divergence of the electron pressure tensor. Both of these features, along with the observed reconnection rate, are consistent with recent laboratory experiments on kinetic-scale flux ropes. In kinetic simulations, the non-gyrotropic pressure tensor terms contribute significantly more to the reconnecting electric field than do the gyrotropic terms, while contributions from the electron inertia are significant for field lines adjacent to the quasi-separatrix layer.

  19. Frontiers for Laboratory Research of Magnetic Reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Hantao [Princeton University; Guo, Fan [Los Alamos National Laboratory

    2015-07-16

    Magnetic reconnection occcurs throughout heliophysical and astrophysical plasmas as well as in laboratory fusion plasmas. Two broad categories of reconnection models exist: collisional MHD and collisionless kinetic. Eight major questions with respect to magnetic connection are set down, and past and future devices for studying them in the laboratory are described. Results of some computerized simulations are compared with experiments.

  20. Coronal magnetic reconnection driven by CME expansion—the 2011 June 7 event

    Energy Technology Data Exchange (ETDEWEB)

    Van Driel-Gesztelyi, L.; Baker, D.; Green, L. M.; Williams, D. R.; Carlyle, J.; Kliem, B.; Long, D. M.; Matthews, S. A. [University College London, Mullard Space Science Laboratory, Holmbury St Mary, Dorking, Surrey RH5 6NT (United Kingdom); Török, T. [Predictive Science Inc., 9990 Mesa Rim Road, Street 170, San Diego, CA 92121 (United States); Pariat, E.; Valori, G.; Démoulin, P.; Malherbe, J.-M. [Observatoire de Paris, LESIA, UMR 8109 (CNRS), F-92195 Meudon-Principal Cedex (France)

    2014-06-10

    Coronal mass ejections (CMEs) erupt and expand in a magnetically structured solar corona. Various indirect observational pieces of evidence have shown that the magnetic field of CMEs reconnects with surrounding magnetic fields, forming, e.g., dimming regions distant from the CME source regions. Analyzing Solar Dynamics Observatory (SDO) observations of the eruption from AR 11226 on 2011 June 7, we present the first direct evidence of coronal magnetic reconnection between the fields of two adjacent active regions during a CME. The observations are presented jointly with a data-constrained numerical simulation, demonstrating the formation/intensification of current sheets along a hyperbolic flux tube at the interface between the CME and the neighboring AR 11227. Reconnection resulted in the formation of new magnetic connections between the erupting magnetic structure from AR 11226 and the neighboring active region AR 11227 about 200 Mm from the eruption site. The onset of reconnection first becomes apparent in the SDO/AIA images when filament plasma, originally contained within the erupting flux rope, is redirected toward remote areas in AR 11227, tracing the change of large-scale magnetic connectivity. The location of the coronal reconnection region becomes bright and directly observable at SDO/AIA wavelengths, owing to the presence of down-flowing cool, dense (10{sup 10} cm{sup –3}) filament plasma in its vicinity. The high-density plasma around the reconnection region is heated to coronal temperatures, presumably by slow-mode shocks and Coulomb collisions. These results provide the first direct observational evidence that CMEs reconnect with surrounding magnetic structures, leading to a large-scale reconfiguration of the coronal magnetic field.

  1. Mesoscopic plasma modes producing magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Coppi, B.; Detragiache, P. (Massachusetts Institute of Technology, Cambridge (United States))

    1993-07-01

    Magnetic reconnection processes in collisionless regimes are shown to be difficult to excite in well confined plasma and, when excited, they possess rather weak characteristics in that they depend on the physics of [open quotes]transition layers[close quotes] that have microscopic dimensions. When considering the effects of the so-called drift frequencies that depend on the pressure gradients of both the electron and the ion populations, modes with azimuthal or poloidal mode number M[sup 0] = 1 can be driven unstable only in a limited range of parameters. The relevance of this theory is pointed out to explain the experimentally observed crash events of the plasma temperature in regimes where the electron collision frequency is smaller then the mode growth rate. Given the mode weakness it is suggested that the onset of reconnection should be triggered or prevented by controlling factors, such as the gradients of the plasma density or the creation of a significant high energy particle population in the center of the plasma column. It is pointed out that the plasma pressure gradient in the affected region of the plasma column is the driving factor of the considered instability in a well-confined plasma and, on this basis, the associated process of magnetic reconnection can be expected to proceed only up to the stage where the instability will have adequately depressed the relevant pressure gradient. The applicability of this analysis to space plasmas is discussed. 26 refs., 8 figs.

  2. Three-minute Sunspot Oscillations Driven by Magnetic Reconnection in a Light Bridge

    Science.gov (United States)

    Song, Donguk; Chae, Jongchul; Kwak, Hannah; Kano, Ryouhei; Yurchyshyn, Vasyl; Moon, Yong-Jae; Lim, Eun-Kyung; Lee, Jeongwoo

    2017-12-01

    We report a different type of three-minute chromospheric oscillation above a sunspot in association with a small-scale impulsive event in a light bridge (LB). During our observations, we found a transient brightening in the LB. The brightening was composed of elementary bursts that may be a manifestation of fast repetitive magnetic reconnections in the LB. Interestingly, the oscillations in the nearby sunspot umbra were impulsively excited when the intensity of the brightening reached its peak. The initial period of the oscillations was about 2.3 minutes and then gradually increased to 3.0 minutes with time. In addition, we found that the amplitude of the excited oscillations was twice the amplitude of oscillations before the brightening. Based on our results, we propose that magnetic reconnection occurring in an LB can excite oscillations in the nearby sunspot umbra.

  3. Energy balance in current sheets: From Petschek to gravity driven reconnection

    International Nuclear Information System (INIS)

    Mercier, C.; Heyvaerts, J.

    1980-01-01

    It has been shown earlier that energy balance processes play a very important role in the determination of the reconnection regime in the central diffusive region of a steady Petschek flow (usually considered elsewhere as isothermal and incompressible): as a consequence of the plasma thermal properties, abrupt transitions in the reconnection regime may occur for special external conditions. The regime becomes then a dynamical one, and it was suggested that onset of plasma microturbulence may result and act as a primary triggering mechanism in solar flares. In this paper we will reexamine the problem of onset of such dynamical transition and conclude that plasma microturbulence does not appear in a straightforward way. However it is possible that the canonical Petschek regime may evolute into a new one in which the dissipative sheet is no longer infinitesimal with respect to the dimensions of the structure, and in which gravity plays an important role. Flare triggering, if related to the reconnection regime, must then proceed by more complex processes, possibly related to tearing mode dynamics, or to more global properties of the magnetic structure of the active region. (orig.)

  4. RECONNECTION-DRIVEN DOUBLE LAYERS IN THE STRATIFIED PLASMA OF THE SOLAR TRANSITION REGION: SUPPLY OF HOT PLASMA INTO THE CORONA

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Nagendra [Department of Electrical and Computer Engineering University of Alabama, Huntsville, AL 35899 (United States)

    2015-09-01

    A novel mechanism for the supply of hot plasma into the corona from the chromosphere is suggested here; the mechanism involves collisionless magnetic reconnection (CMR) in the transition region (TR) followed by double layer (DL) formation in the enhanced expansion of the chromospheric cold plasma mixed with CMR-heated hot electrons. It is well known that (i) the CMR produces energetic electrons and (ii) DLs naturally form in expanding dense plasmas containing a minor population of hot electrons. We apply these plasma physics facts to the dynamics of stratified plasma in the TR. In the TR where densities fall below ∼10{sup 16} m{sup −3}, all collisional mean-free paths, electron–ion, ion–neutral, and electron–neutral, become long enough to render plasma collisionless at kinetic scale lengths, making CMR and DL formation possible. The DLs accelerate the chromospheric cold ions to energies comparable to the energy of the hot electrons. When the upflowing energized ions neutralized by the escaping hot electrons thermalize, the resulting hot tenuous plasma supplies an energy flux ∼3 × 10{sup 5} erg cm{sup −2} s{sup −1} = 3 × 10{sup 2} J m{sup −2} s{sup −1} into the corona. The CMR–DL mechanism introduces sudden transitions in the TR as microstructures in both density and energy. The global transition in the TR could be a fractal structure containing such microscopic features. If not impossible, it is difficult to measure such microstructures, but it seems that the coronal heating begins in the nearly collisionless TR by CMR and DL formation.

  5. Collisionless plasmas in astrophysics

    CERN Document Server

    Belmont, Gerard; Mottez, Fabrice; Pantellini, Filippo; Pelletier, Guy

    2013-01-01

    Collisionless Plasmas in Astrophysics examines the unique properties of media without collisions in plasma physics. Experts in this field, the authors present the first book to concentrate on collisionless conditions in plasmas, whether close or not to thermal equilibrium. Filling a void in scientific literature, Collisionless Plasmas in Astrophysics explains the possibilities of modeling such plasmas, using a fluid or a kinetic framework. It also addresses common misconceptions that even professionals may possess, on phenomena such as "collisionless (Landau) damping". Abundant illustrations

  6. Momentum transport and nonlocality in heat-flux-driven magnetic reconnection in high-energy-density plasmas

    Science.gov (United States)

    Liu, Chang; Fox, William; Bhattacharjee, Amitava; Thomas, Alexander G. R.; Joglekar, Archis S.

    2017-10-01

    Recent theory has demonstrated a novel physics regime for magnetic reconnection in high-energy-density plasmas where the magnetic field is advected by heat flux via the Nernst effect. Here we elucidate the physics of the electron dissipation layer in this regime. Through fully kinetic simulation and a generalized Ohm's law derived from first principles, we show that momentum transport due to a nonlocal effect, the heat-flux-viscosity, provides the dissipation mechanism for magnetic reconnection. Scaling analysis, and simulations show that the reconnection process comprises a magnetic field compression stage and quasisteady reconnection stage, and the characteristic width of the current sheet in this regime is several electron mean-free paths. These results show the important interplay between nonlocal transport effects and generation of anisotropic components to the distribution function.

  7. Collisionless electrostatic shocks

    DEFF Research Database (Denmark)

    Andersen, H.K.; Andersen, S.A.; Jensen, Vagn Orla

    1970-01-01

    An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth......An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth...

  8. Magnetic Reconnection

    NARCIS (Netherlands)

    Schep, T. J.

    1994-01-01

    This lecture deals with the concept of magnetic field lines and with the conservation of magnetic flux. In high temperature fusion devices like tokamaks flux conservation can be violated and reconnection can occur at closed magnetic field lines. Reconnection processes lead to changes in the global

  9. On the cessation of magnetic reconnection

    Directory of Open Access Journals (Sweden)

    M. Hesse

    2004-01-01

    Full Text Available Kinetic simulations of collisionless magnetic reconnection are used to study the effect on the reconnection rate of ion density enhancements in the inflow region. The goal of the investigation is to study a candidate mechanism for the slow-down of magnetic reconnection. The calculations involve either proton or oxygen additions in the inflow region, initially located at two distances from the current sheet. Protons are found to be much more tightly coupled into the evolution of the reconnecting system and, therefore, they effect an immediate slowdown of the reconnection process, as soon as the flux tubes they reside on become involved. Oxygen, on the other hand, has, within the limits of the calculations, a much less pronounced effect on the reconnection electric field. The difference is attributed to the lack of tight coupling to the magnetic field of the oxygen populations. Last, a study of proton and oxygen acceleration finds that protons respond primarily to the reconnection electric field, whereas the main oxygen electric field is achieved by Hall-type electric fields at the plasma sheet boundary. Key words. Space plasma physics (magnetic reconnection; numerical simulation studies; numerical simulation studies

  10. Magnetic reconnection in plasma under inertial confinement fusion conditions driven by heat flux effects in Ohm's law.

    Science.gov (United States)

    Joglekar, A S; Thomas, A G R; Fox, W; Bhattacharjee, A

    2014-03-14

    In the interaction of high-power laser beams with solid density plasma there are a number of mechanisms that generate strong magnetic fields. Such fields subsequently inhibit or redirect electron flows, but can themselves be advected by heat fluxes, resulting in complex interplay between thermal transport and magnetic fields. We show that for heating by multiple laser spots reconnection of magnetic field lines can occur, mediated by these heat fluxes, using a fully implicit 2D Vlasov-Fokker-Planck code. Under such conditions, the reconnection rate is dictated by heat flows rather than Alfvènic flows. We find that this mechanism is only relevant in a high β plasma. However, the Hall parameter ωcτei can be large so that thermal transport is strongly modified by these magnetic fields, which can impact longer time scale temperature homogeneity and ion dynamics in the system.

  11. Nonlinear magnetic reconnection in low collisionality plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Ottaviani, M. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Porcelli, F. [Politecnico di Torino, Turin (Italy)

    1994-07-01

    The magnetic reconnection in collisionless regimes, where electron inertia is responsible for the decoupling of the plasma motion from that of the field lines, is discussed. Since the linear theory of m=1 modes breaks down for very small magnetic island widths, a non linear analysis is called for. Thus, the behaviour of a collisionless, 2-D fluid slab model in the limit {rho}/d -> 0, is analyzed. The main result is that, when the island size is larger than the linear layer but smaller than the equilibrium scale length, the reconnection rate exhibits a quasi-explosive time behaviour, during which a current density sub-layer narrower than the skin depth is formed. It is believed that the inclusion of the electron initial term in Ohm`s law opens the possibility to understand the rapidity of relaxation process observed in low collisionality plasmas. 7 refs., 6 figs.

  12. Magnetic Reconnection

    International Nuclear Information System (INIS)

    Yamada, Masaaki; Kulsrud, Russell; Ji, Hantao

    2009-01-01

    We review the fundamental physics of magnetic reconnection in laboratory and space plasmas, by discussing results from theory, numerical simulations, observations from space satellites, and the recent results from laboratory plasma experiments. After a brief review of the well-known early work, we discuss representative recent experimental and theoretical work and attempt to interpret the essence of significant modern findings. In the area of local reconnection physics, many significant findings have been made with regard to two-fluid physics and are related to the cause of fast reconnection. Profiles of the neutral sheet, Hall currents, and the effects of guide field, collisions, and micro-turbulence are discussed to understand the fundamental processes in a local reconnection layer both in space and laboratory plasmas. While the understanding of the global reconnection dynamics is less developed, notable findings have been made on this issue through detailed documentation of magnetic self-organization phenomena in fusion plasmas. Application of magnetic reconnection physics to astrophysical plasmas is also briefly discussed.

  13. Magnetic Reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Masaaki Yamada, Russell Kulsrud and Hantao Ji

    2009-09-17

    We review the fundamental physics of magnetic reconnection in laboratory and space plasmas, by discussing results from theory, numerical simulations, observations from space satellites, and the recent results from laboratory plasma experiments. After a brief review of the well-known early work, we discuss representative recent experimental and theoretical work and attempt to interpret the essence of significant modern findings. In the area of local reconnection physics, many significant findings have been made with regard to two- uid physics and are related to the cause of fast reconnection. Profiles of the neutral sheet, Hall currents, and the effects of guide field, collisions, and micro-turbulence are discussed to understand the fundamental processes in a local reconnection layer both in space and laboratory plasmas. While the understanding of the global reconnection dynamics is less developed, notable findings have been made on this issue through detailed documentation of magnetic self-organization phenomena in fusion plasmas. Application of magnetic reconnection physics to astrophysical plasmas is also brie y discussed.

  14. The Development of Drift Wave Turbulence in Magnetic Reconnection

    Science.gov (United States)

    McMurtrie, L.; Drake, J. F.; Swisdak, M. M.

    2013-12-01

    An important feature in collisionless magnetic reconnection is the development of sharp discontinuities along the separatrices bounding the Alfvenic outflow. The typical scale length of these features is ρs (the Larmor radius based on the sound speed) for guide field reconnection. Temperature gradients in the inflowing plasma (as might be found in the magnetopause) can lead to instabilities at these separatrices, specifically drift wave turbulence. We present standalone 2D and 3D PIC simulations of drift wave turbulence to investigate scaling properties and growth rates. Further investigations of the relative importance of drift wave turbulence in the development of reconnection will also be considered.

  15. Force balance near an X line in a collisionless plasma

    Science.gov (United States)

    Lyons, L. R.; Pridmore-Brown, D. C.

    1990-01-01

    The suggestion by Dungey (1988) that the gyroviscosity associated with gradients of the off-diagonal elements of the electron pressure tensor can balance a reconnection electric field along a magnetic X line in a collisionless plasma is investigated. The detailed balance of forces in the vicinity of an X line is evaluated using a two-dimensional magnetic field model and a simple model for particle motion. The results show that the gyroviscosity can indeed provide the force required to balance a reconnection electric field in that region, so that neither collisions nor wave turbulence are necessary for reconnection. The results also show that there should not be a significant increase in current from electron acceleration very near an X line. Reasonable numerical estimates are obtained for conditions expected in the vicinity of the distant X line in the geomagnetic tail.

  16. Toward laboratory torsional spine magnetic reconnection

    Science.gov (United States)

    Chesny, David L.; Orange, N. Brice; Oluseyi, Hakeem M.; Valletta, David R.

    2017-12-01

    Magnetic reconnection is a fundamental energy conversion mechanism in nature. Major attempts to study this process in controlled settings on Earth have largely been limited to reproducing approximately two-dimensional (2-D) reconnection dynamics. Other experiments describing reconnection near three-dimensional null points are non-driven, and do not induce any of the 3-D modes of spine fan, torsional fan or torsional spine reconnection. In order to study these important 3-D modes observed in astrophysical plasmas (e.g. the solar atmosphere), laboratory set-ups must be designed to induce driven reconnection about an isolated magnetic null point. As such, we consider the limited range of fundamental resistive magnetohydrodynamic (MHD) and kinetic parameters of dynamic laboratory plasmas that are necessary to induce the torsional spine reconnection (TSR) mode characterized by a driven rotational slippage of field lines - a feature that has yet to be achieved in operational laboratory magnetic reconnection experiments. Leveraging existing reconnection models, we show that within a 3$ apparatus, TSR can be achieved in dense plasma regimes ( 24~\\text{m}-3$ ) in magnetic fields of -1~\\text{T}$ . We find that MHD and kinetic parameters predict reconnection in thin current sheets on time scales of . While these plasma regimes may not explicitly replicate the plasma parameters of observed astrophysical phenomena, studying the dynamics of the TSR mode within achievable set-ups signifies an important step in understanding the fundamentals of driven 3-D magnetic reconnection and the self-organization of current sheets. Explicit control of this reconnection mode may have implications for understanding particle acceleration in astrophysical environments, and may even have practical applications to fields such as spacecraft propulsion.

  17. Anomalous particle pinch for collisionless plasma

    International Nuclear Information System (INIS)

    Terry, P.W.

    1989-01-01

    The particle transport arising from the convection of nonadiabatic electron density by ion temperature gradient driven turbulence is examined when trapped electrons collide less often than a bounce period. In the lower temperature end of this regime, trapped electrons are collisional and the particle flux is outward (in the direction of the gradients). When the trapped electrons are collisionless, there is a temperature threshold above which the electron temperature gradient driven particle flux changes sign and becomes inward. The magnitude of the nonadiabatic electron contribution to the growth rate is found to be potentially of the same order as the ion contribution. 11 refs

  18. MMS observations of guide field reconnection at the interface between colliding reconnection jets inside flux rope-like structures at the magnetopause

    Science.gov (United States)

    Oieroset, M.; Phan, T.; Haggerty, C. C.; Shay, M.; Eastwood, J. P.; Gershman, D. J.; Drake, J. F.; Fujimoto, M.; Ergun, R.; Mozer, F.; Oka, M.; Torbert, R. B.; Burch, J. L.; Wang, S.; Chen, L. J.; Swisdak, M.; Pollock, C. J.; Dorelli, J.; Fuselier, S. A.; Lavraud, B.; Kacem, I.; Giles, B. L.; Moore, T. E.; Saito, Y.; Avanov, L. A.; Paterson, W. R.; Strangeway, R. J.; Schwartz, S. J.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Malakit, K.

    2017-12-01

    The formation and evolution of magnetic flux ropes is of critical importance for a number of collisionless plasma phenomena. At the dayside magnetopause flux rope-like structures can form between two X-lines. The two X-lines produce converging plasma jets. At the interface between the colliding jets a compressed current sheet can form, which in turn can undergo reconnection. We present MMS observations of the exhaust and diffusion region of such reconnection.

  19. Fast Magnetic Reconnection in the Plasmoid-Dominated Regime

    International Nuclear Information System (INIS)

    Uzdensky, D. A.; Loureiro, N. F.; Schekochihin, A. A.

    2010-01-01

    A conceptual model of resistive magnetic reconnection via a stochastic plasmoid chain is proposed. The global reconnection rate is shown to be independent of the Lundquist number. The distribution of fluxes in the plasmoids is shown to be an inverse-square law. It is argued that there is a finite probability of emergence of abnormally large plasmoids, which can disrupt the chain (and may be responsible for observable large abrupt events in solar flares and sawtooth crashes). A criterion for the transition from the resistive magnetohydrodynamic to the collisionless regime is provided.

  20. Magnetic reconnection in magnetotail and solar plasmas

    International Nuclear Information System (INIS)

    Wang Xiaogang.

    1991-01-01

    The formation of current sheets which dominates the heating of the solar corona and the onset of substorms due to collisionless tearing instability in the magnetotail are investigated in the context of magnetic field line reconnection in space plasmas. In Chapters 2 and 3 of this thesis, the collisionless tearing instability and current disruption of the magnetotail are considered. The linear collisionless tearing instability, with wavelengths of the order of 10 R E , and with a growth rate γ ∼ 10 -2 /sec, is identified as a possible mechanism for the growth phase of a substorm. The linear analysis is carried out in the presence of an equilibrium B y -field, neglected in other theories. The nonlinear theory of collisionless tearing mode is dominated by mode coupling effects. From the evolution equations for electro-magnetic field perturbations, the author derived a nonlinear growth rate by generalizing the boundary layer techniques of linear theory. He finds that the nonlinear growth is of the order of 1 sec, much faster than the linear growth. It is proposed that collisionless tearing modes provide a mechanism for current disruption observed by spacecrafts. The electrical field generated during the nonlinear evolution can cause particle acceleration in the earth-tail direction. His estimates indicate ion energies up to 0.7 MeV and electron energies up to 8.1 MeV, which is not inconsistent with the observations. In the Chapter 4 it is shown that current sheets can be formed in Parker's model of the solar corona in the presence of smooth photospheric flows, despite van Ballegooijen and Field's proof that in an ideal plasma current sheets doe not occur unless the boundary velocity field is discontinuous

  1. Collisionless sausage instability

    International Nuclear Information System (INIS)

    Coppins, M.

    1989-01-01

    The Chew--Goldberger--Low (CGL) double adiabatic model [Proc. R. Soc. London Ser. A 236, 112 (1956)] is used to study the linear m = 0 (sausage) mode in a Z pinch operating in the collisionless, small ion Larmor radius regime. The model is valid in this case since the parallel heat flow is identically zero. A necessary and sufficient condition for stability, applicable to arbitrary (anisotropic) Z-pinch equilibria, is derived and the eigenvalue equation is solved for two classes of isotropic equilibria. Growth rates are shown to be lower than those of ideal magnetohydrodynamics (MHD). It is found that, in contrast to ideal MHD, the CGL eigenfunctions are characterized by an unperturbed inner region

  2. Global Simulations of Magnetotail Reconnection

    Science.gov (United States)

    Kuznetsova, M. M.; Hesse, M.; Rastatter, L.; Toth, G.; Gombosi, T.

    2007-01-01

    There is a growing number of observational evidences of dynamic quasi-periodical magnetosphere response to continuously southward interplan etary magnetic field (IMF). However, traditional global MHD simulatio ns with magnetic reconnection supported by numerical dissipation and ad hoc anomalous resistivity driven by steady southward IMF often prod uce only quasi-steady configurations with almost stationary near-eart h neutral line. This discrepancy can be explained by the assumption that global MHD simulations significantly underestimate the reconnectio n rate in the magnetotail during substorm expansion phase. Indeed, co mparative studies of magnetic reconnection in small scale geometries demonstrated that traditional resistive MHD did not produce the fast r econnection rates observed in kinetic simulations. The major approxim ation of the traditional MHD approach is an isotropic fluid assumption) with zero off-diagonal pressure tensor components. The approximatio n, however, becomes invalid in the diffusion region around the reconn ection site where ions become unmagnetized and experience nongyrotropic behaviour. Deviation from gyrotropy in particle distribution functi on caused by kinetic effects manifests itself in nongyrotropic pressu re tensor with nonzero off-diagonal components. We use the global MHD code BATS-R-US and replace ad hoc parameters such as "critical curren t density" and "anomalous resistivity" with a physically motivated di ssipation model. The key element of the approach is to identify diffusion regions where the isotropic fluid MHD approximation is not applic able. We developed an algorithm that searches for locations of magnet otail reconnection sites. The algorithm takes advantage of block-based domain-decomposition technique employed by the BATS-R-US. Boundaries of the diffusion region around each reconnection site are estimated from the gyrotropic orbit threshold condition, where the ion gyroradius is equal to the distance to the

  3. A Parallel Two-fluid Code for Global Magnetic Reconnection Studies

    International Nuclear Information System (INIS)

    Breslau, J.A.; Jardin, S.C.

    2001-01-01

    This paper describes a new algorithm for the computation of two-dimensional resistive magnetohydrodynamic (MHD) and two-fluid studies of magnetic reconnection in plasmas. It has been implemented on several parallel platforms and shows good scalability up to 32 CPUs for reasonable problem sizes. A fixed, nonuniform rectangular mesh is used to resolve the different spatial scales in the reconnection problem. The resistive MHD version of the code uses an implicit/explicit hybrid method, while the two-fluid version uses an alternating-direction implicit (ADI) method. The technique has proven useful for comparing several different theories of collisional and collisionless reconnection

  4. Collisionless dissipation of Langmuir turbulence

    International Nuclear Information System (INIS)

    Erofeev, V.I.

    2002-01-01

    An analysis of two experimental observations of Langmuir wave collapse is performed. The corresponding experimental data are shown to give evidence against the collapse. The physical reason for preventing the collapses is found to be the nonresonant electron diffusion in momentums. In this process, plasma thermal electrons are efficiently heated at the expense of wave energy, and intense collisionless wave dissipation takes place. The basic reason of underestimation of this phenomenon in traditional theory is shown to be the substitution of real plasma by a plasma probabilistic ensemble. A theory of nonresonant electron diffusion in a single collisionless plasma is developed. It is shown that corresponding collisionless wave dissipation may arrest spectral energy transfer towards small wave numbers

  5. A collisionless shock wave experiment

    International Nuclear Information System (INIS)

    Winske, D.; Jones, M.E.; Sgro, A.G.; Thomas, V.A.

    1995-01-01

    Collisionless shock waves are a very important heating mechanism for plasmas and are commonly found in space and astrophysical environments. Collisionless shocks were studied in the laboratory more than 20 years ago, and more recently in space via in situ satellite measurements. The authors propose a new laboratory shock wave experiment to address unresolved issues related to the differences in the partition of plasma heating between electrons and ions in space and laboratory plasmas, which can have important implications for a number of physical systems

  6. Endogenous Magnetic Reconnection in Solar Coronal Loops

    Science.gov (United States)

    Asgari-Targhi, M.; Coppi, B.; Basu, B.; Fletcher, A.; Golub, L.

    2017-12-01

    We propose that a magneto-thermal reconnection process occurring in coronal loops be the source of the heating of the Solar Corona [1]. In the adopted model, magnetic reconnection is associated with electron temperature gradients, anisotropic electron temperature fluctuations and plasma current density gradients [2]. The input parameters for our theoretical model are derived from the most recent observations of the Solar Corona. In addition, the relevant (endogenous) collective modes can produce high energy particle populations. An endogenous reconnection process is defined as being driven by factors internal to the region where reconnection takes place. *Sponsored in part by the U.S. D.O.E. and the Kavli Foundation* [1] Beafume, P., Coppi, B. and Golub, L., (1992) Ap. J. 393, 396. [2] Coppi, B. and Basu, B. (2017) MIT-LNS Report HEP 17/01.

  7. Corotating Magnetic Reconnection Site in Saturn’s Magnetosphere

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Z. H.; Coates, A. J.; Ray, L. C.; Rae, I. J.; Jones, G. H.; Owen, C. J.; Dunn, W. R.; Lewis, G. R. [UCL Mullard Space Science Laboratory, Dorking RH5 6NT (United Kingdom); Grodent, D.; Radioti, A.; Gérard, J.-C. [Laboratoire de Physique Atmosphérique et Planétaire, STAR institute, Université de Liège, B-4000 Liège (Belgium); Dougherty, M. K. [Imperial College of Science, Technology and Medicine, Space and Atmospheric Physics Group, Department of Physics, London SW7 2BW (United Kingdom); Guo, R. L. [Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing (China); Pu, Z. Y. [School of Earth and Space Sciences, Peking University, Beijing (China); Waite, J. H., E-mail: z.yao@ucl.ac.uk [Southwest Research Institute, San Antonio, TX (United States)

    2017-09-10

    Using measurements from the Cassini spacecraft in Saturn’s magnetosphere, we propose a 3D physical picture of a corotating reconnection site, which can only be driven by an internally generated source. Our results demonstrate that the corotating magnetic reconnection can drive an expansion of the current sheet in Saturn’s magnetosphere and, consequently, can produce Fermi acceleration of electrons. This reconnection site lasted for longer than one of Saturn’s rotation period. The long-lasting and corotating natures of the magnetic reconnection site at Saturn suggest fundamentally different roles of magnetic reconnection in driving magnetospheric dynamics (e.g., the auroral precipitation) from the Earth. Our corotating reconnection picture could also potentially shed light on the fast rotating magnetized plasma environments in the solar system and beyond.

  8. Rapid reconnection in compressible plasma

    International Nuclear Information System (INIS)

    Heyn, M.F.; Semenov, V.S.

    1996-01-01

    A study of set-up, propagation, and interaction of non-linear and linear magnetohydrodynamic waves driven by magnetic reconnection is presented. The source term of the waves generated by magnetic reconnection is obtained explicitly in terms of the initial background conditions and the local reconnection electric field. The non-linear solution of the problem found earlier, serves as a basis for formulation and extensive investigation of the corresponding linear initial-boundary value problem of compressible magnetohydrodynamics. In plane geometry, the Green close-quote s function of the problem is obtained and its properties are discussed. For the numerical evaluation it turns out that a specific choice of the integration contour in the complex plane of phase velocities is much more effective than the convolution with the real Green close-quote s function. Many complex effects like intrinsic wave coupling, anisotropic propagation characteristics, generation of surface and side wave modes in a finite beta plasma are retained in this analysis. copyright 1996 American Institute of Physics

  9. Studying astrophysical particle acceleration with laser-driven plasmas

    Science.gov (United States)

    Fiuza, Frederico

    2016-10-01

    The acceleration of non-thermal particles in plasmas is critical for our understanding of explosive astrophysical phenomena, from solar flares to gamma ray bursts. Particle acceleration is thought to be mediated by collisionless shocks and magnetic reconnection. The microphysics underlying these processes and their ability to efficiently convert flow and magnetic energy into non-thermal particles, however, is not yet fully understood. By performing for the first time ab initio 3D particle-in-cell simulations of the interaction of both magnetized and unmagnetized laser-driven plasmas, it is now possible to identify the optimal parameters for the study of particle acceleration in the laboratory relevant to astrophysical scenarios. It is predicted for the Omega and NIF laser conditions that significant non-thermal acceleration can occur during magnetic reconnection of laser-driven magnetized plasmas. Electrons are accelerated by the electric field near the X-points and trapped in contracting magnetic islands. This leads to a power-law tail extending to nearly a hundred times the thermal energy of the plasma and that contains a large fraction of the magnetic energy. The study of unmagnetized interpenetrating plasmas also reveals the possibility of forming collisionless shocks mediated by the Weibel instability on NIF. Under such conditions, both electrons and ions can be energized by scattering out of the Weibel-mediated turbulence. This also leads to power-law spectra that can be detected experimentally. The resulting experimental requirements to probe the microphysics of plasma particle acceleration will be discussed, paving the way for the first experiments of these important processes in the laboratory. As a result of these simulations and theoretical analysis, there are new experiments being planned on the Omega, NIF, and LCLS laser facilities to test these theoretical predictions. This work was supported by the SLAC LDRD program and DOE Office of Science, Fusion

  10. On Collisionless Damping of Ion Acoustic Waves

    DEFF Research Database (Denmark)

    Jensen, Vagn Orla; Petersen, P.I.

    1973-01-01

    Exact theoretical treatments show that the damping of ion acoustic waves in collisionless plasmas does not vanish when the derivative of the undisturbed distribution function at the phase velocity equals zero.......Exact theoretical treatments show that the damping of ion acoustic waves in collisionless plasmas does not vanish when the derivative of the undisturbed distribution function at the phase velocity equals zero....

  11. Final report for the NSF/DOE partnership in basic plasma science grant DE-FG02-06ER54906 'Laser-driven collisionless shocks in the Large Plasma Device'

    Energy Technology Data Exchange (ETDEWEB)

    Niemann, Christoph [UCLA, CA (United States); Gekelman, W. [UCLA, CA (United States); Winske, D. [LANL, NM (United States); Larsen, D. [LLNL, CA (United States)

    2012-12-14

    We have performed several thousand high-energy laser shots in the LAPD to investigate the dynamics of an exploding laser-produced plasma in a large ambient magneto-plasma. Debris-ions expanding at super-Alfvenic velocity (up to MA=1.5) expel the ambient magnetic field, creating a large (> 20 cm) diamagnetic cavity. We observed field compressions of up to B/B{sub 0} = 1.5 at the edge of the bubble, consistent with the MHD jump conditions, as well as localized electron heating at the edge of the bubble. Two-dimensional hybrid simulations reproduce these measurements well and show that the majority of the ambient ions are energized by the magnetic piston to super-Alfvenic speeds and swept outside the bubble volume. Nonlinear shear-Alfven waves ({delta}B/B{sub 0} > 25%) are radiated from the cavity with a coupling efficiency of 70% from magnetic energy in the bubble to the wave. While the data is consistent with a weak magneto-sonic shock, the experiments were severely limited by the low ambient plasma densities (10{sup 12} cm{sup -3}). 2D hybrid simulations indicate that future experiments with the new LAPD plasma source and densities in excess of 10{sup 13} cm{sup -3} will drive full-blown collisionless shocks with MA>10 over several c/wpi and shocked Larmor radii. In a separate experiment at the LANL Trident laser facility we have performed a proof-of-principle experiment at higher densities to demonstrate key elements of collisionless shocks in laser-produced magnetized plasmas with important implications to NIF. Simultaneously we have upgraded the UCLA glass-laser system by adding two large amplitude disk amplifiers from the NOVA laser and boost the on-target energy from 30 J to up to 1 kJ, making this one of the world’s largest university-scale laser systems. We now have the infrastructure in place to perform novel and unique high-impact experiments on collision-less shocks at the LAPD.

  12. Final report for the NSF/DOE partnership in basic plasma science grant DE-FG02-06ER54906 'Laser-driven collisionless shocks in the Large Plasma Device'™

    International Nuclear Information System (INIS)

    Niemann, Christoph; Gekelman, W.; Winske, D.; Larsen, D.

    2012-01-01

    We have performed several thousand high-energy laser shots in the LAPD to investigate the dynamics of an exploding laser-produced plasma in a large ambient magneto-plasma. Debris-ions expanding at super-Alfvenic velocity (up to MA=1.5) expel the ambient magnetic field, creating a large (> 20 cm) diamagnetic cavity. We observed field compressions of up to B/B 0 = 1.5 at the edge of the bubble, consistent with the MHD jump conditions, as well as localized electron heating at the edge of the bubble. Two-dimensional hybrid simulations reproduce these measurements well and show that the majority of the ambient ions are energized by the magnetic piston to super-Alfvenic speeds and swept outside the bubble volume. Nonlinear shear-Alfven waves (δB/B 0 > 25%) are radiated from the cavity with a coupling efficiency of 70% from magnetic energy in the bubble to the wave. While the data is consistent with a weak magneto-sonic shock, the experiments were severely limited by the low ambient plasma densities (10 12 cm -3 ). 2D hybrid simulations indicate that future experiments with the new LAPD plasma source and densities in excess of 10 13 cm -3 will drive full-blown collisionless shocks with MA>10 over several c/wpi and shocked Larmor radii. In a separate experiment at the LANL Trident laser facility we have performed a proof-of-principle experiment at higher densities to demonstrate key elements of collisionless shocks in laser-produced magnetized plasmas with important implications to NIF. Simultaneously we have upgraded the UCLA glass-laser system by adding two large amplitude disk amplifiers from the NOVA laser and boost the on-target energy from 30 J to up to 1 kJ, making this one of the world's largest university-scale laser systems. We now have the infrastructure in place to perform novel and unique high-impact experiments on collision-less shocks at the LAPD

  13. Forced magnetic reconnection

    Science.gov (United States)

    Vekstein, G.

    2017-10-01

    This is a tutorial-style selective review explaining basic concepts of forced magnetic reconnection. It is based on a celebrated model of forced reconnection suggested by J. B. Taylor. The standard magnetohydrodynamic (MHD) theory of this process has been pioneered by Hahm & Kulsrud (Phys. Fluids, vol. 28, 1985, p. 2412). Here we also discuss several more recent developments related to this problem. These include energetics of forced reconnection, its Hall-mediated regime, and nonlinear effects with the associated onset of the secondary tearing (plasmoid) instability.

  14. Towards parallel collisionless shocks in the Large Plasma Device

    Science.gov (United States)

    Weidl, M. S.; Heuer, P. V.; Schaeffer, D.; Winske, D.; Constantin, C. G.; Dorst, R.; Niemann, C.

    2017-12-01

    Previous research on parallel collisionless shocks, which constitute an important part of the Earth's bow shock region, has been limited to satellite measurements and simulations. However, whether and how these collisionless shocks form depends on a wide range of parameters and scales, some of which can be established and measured more easily in a laboratory experiment.Using a kJ-class laser, an ongoing experimental campaign at the Large Plasma Device (LAPD) at UCLA in Los Angeles is expected to produce the first laboratory measurements of the formation of a parallel collisionless shock. We present hybrid kinetic/MHD simulations which show how ion-beam instabilities in the background plasma can be driven by ablating carbon ions from a polyethylene target, causing non-linear density oscillations which eventually develop into a propagating shock front.The free-streaming carbon ions can excite both the resonant right-hand instability and the non-resonant firehose mode, the latter of which has also received a lot of attention among astrophysicists as Bell's instability. We present detailed magnetic-field measurements from LAPD experiments in which we have identified these instabilities, and discuss their respective roles for future shock formation and the basic microphysical processes which drive them.

  15. Parallel collisionless-shock experiments at the Large Plasma Device

    Science.gov (United States)

    Weidl, Martin; Heuer, Peter; Bondarenko, Anton; Schaeffer, Derek; Winske, Dan; Constantin, Carmen; Jenko, Frank; Niemann, Christoph

    2017-04-01

    Previous research on parallel collisionless shocks, which constitute an important part of the Earth's bow shock region, has been limited to satellite measurements and simulations. However, whether and how these collisionless shocks form depends on a wide range of parameters and scales, some of which can be established and measured more easily in a laboratory experiment. Using a kJ-class laser, an ongoing experimental campaign at the Large Plasma Device (LAPD) at UCLA in Los Angeles is expected to produce the first laboratory measurements of the formation of a parallel collisionless shock. We present hybrid kinetic/MHD simulations which show how ion-beam instabilities in the background plasma can be driven by ablating carbon ions from a polyethylene target, causing non-linear density oscillations which eventually develop into a propagating shock front. The free-streaming carbon ions can excite both the resonant right-hand instability and the non-resonant firehose mode, the latter of which has also received a lot of attention among astrophysicists as Bell's instability. We present measurements from a first trial experiment at LAPD, in which we have identified these instabilities, and discuss their respective roles for future shock formation and the basic microphysical processes which drive them.

  16. Magnetic Reconnection with Sweet-Parker Characteristics in Two-dimensional Laboratory Plasmas

    International Nuclear Information System (INIS)

    Carter, T.; Hsu, S.; Ji, H.; Kulsrud, R.; Yamada, M.

    1999-01-01

    Magnetic reconnection has been experimentally studied in a well-controlled, two-dimensional laboratory magnetohydrodynamic plasma. The observations are found to be both qualitatively and quantitatively consistent with a generalized Sweet-Parker model which incorporates compressibility, downstream pressure, and the effective resistivity. The latter is significantly enhanced over its classical values in the collisionless limit. This generalized Sweet-Parker model also applies to the case in which an unidirectional, sizable third magnetic component is present

  17. Universal collisionless transport of graphene

    Science.gov (United States)

    Link, Julia M.; Orth, Peter P.; Sheehy, Daniel E.; Schmalian, Jörg

    2016-06-01

    The impact of the electron-electron Coulomb interaction on the optical conductivity of graphene has led to a controversy that calls into question the universality of collisionless transport in this and other Dirac materials. Using a lattice calculation that avoids divergences present in previous nodal Dirac approaches, our work settles this controversy and obtains results in quantitative agreement with experiment over a wide frequency range. We also demonstrate that dimensional regularization methods agree, if the regularization of the theory in modified dimensions is correctly implemented. Tight-binding lattice and nodal Dirac theory calculations are shown to coincide at low energies even when the nonzero size of the atomic orbital wave function is included, conclusively demonstrating the universality of the optical conductivity of graphene.

  18. Nonlinear waves in collisionless gravitating systems

    Energy Technology Data Exchange (ETDEWEB)

    Polyachenko, V.L.; Shukhman, I.G.

    1979-09-01

    Nonlinear equations are derived for the gravitational potential in collisionless systems modeling galaxies. Solutions in the form of solitary waves (solitons) are obtained and their stability is tested. Systems composed of both stars and gas are also discussed. The dependence of the critical wavelength on the perturbation amplitude is established for the classical Jeans problem (an infinite, homogeneous world model) and for its two- and one-dimensional analogs in the collisionless case.

  19. Forced magnetic reconnection

    International Nuclear Information System (INIS)

    Hahm, T.S.; Kulsrud, R.M.

    1984-11-01

    By studying a simple model problem, we examine the time evolution of magnetic field islands which are induced by perturbing the boundary surrounding an incompressible plasma with a resonant surface inside. We find that for sufficiently small boundary perturbations, the reconnection and island formation process occurs on the tearing mode time scale defined by Furth, Killeen, and Rosenbluth. For larger perturbations the time scale is that defined by Rutherford. The resulting asymptotic equilibrium is such that surface currents in the resonant region vanish. A detailed analytical picture of this reconnection process is presented

  20. The physical foundation of the reconnection electric field

    Science.gov (United States)

    Hesse, M.; Liu, Y.-H.; Chen, L.-J.; Bessho, N.; Wang, S.; Burch, J. L.; Moretto, T.; Norgren, C.; Genestreti, K. J.; Phan, T. D.; Tenfjord, P.

    2018-03-01

    Magnetic reconnection is a key charged particle transport and energy conversion process in environments ranging from astrophysical systems to laboratory plasmas [Yamada et al., Rev. Mod. Phys. 82, 603-664 (2010)]. Magnetic reconnection facilitates plasma transport by establishing new connections of magnetic flux tubes, and it converts, often explosively, energy stored in the magnetic field to kinetic energy of charged particles [J. L. Burch and J. F. Drake, Am. Sci. 97, 392-299 (2009)]. The intensity of the magnetic reconnection process is measured by the reconnection electric field, which regulates the rate of flux tube connectivity changes. The change of magnetic connectivity occurs in the current layer of the diffusion zone, where the plasma transport is decoupled from the transport of magnetic flux. Here we report on computer simulations and analytic theory to provide a self-consistent understanding of the role of the reconnection electric field, which extends substantially beyond the simple change of magnetic connections. Rather, we find that the reconnection electric field is essential to maintain the current density in the diffusion region, which would otherwise be dissipated by a set of processes. Natural candidates for current dissipation are the average convection of current carriers away from the reconnection region by the outflow of accelerated particles, or the average rotation of the current density by the magnetic field reversal in the vicinity. Instead, we show here that the current dissipation is the result of thermal effects, underlying the statistical interaction of current-carrying particles with the adjacent magnetic field. We find that this interaction serves to redirect the directed acceleration of the reconnection electric field to thermal motion. This thermalization manifests itself in form of quasi-viscous terms in the thermal energy balance of the current layer. This collisionless viscosity, found in the pressure evolution equation

  1. Reconnection in tokamaks

    International Nuclear Information System (INIS)

    Pare, V.K.

    1983-01-01

    Calculations with several different computer codes based on the resistive MHD equations have shown that (m = 1, n = 1) tearing modes in tokamak plasmas grow by magnetic reconnection. The observable behavior predicted by the codes has been confirmed in detail from the waveforms of signals from x-ray detectors and recently by x-ray tomographic imaging

  2. Magneto-thermal reconnection of significance to space and astrophysics

    International Nuclear Information System (INIS)

    Coppi, B.

    2016-01-01

    Magnetic reconnection processes that can be excited in collisionless plasma regimes are of interest to space and astrophysics to the extent that the layers in which reconnection takes place are not rendered unrealistically small by their unfavorable dependence on relevant macroscopic distances. The equations describing new modes producing magnetic reconnection over relatively small but significant distances, unlike tearing types of mode, even when dealing with large macroscopic scale lengths, are given. The considered modes are associated with a finite electron temperature gradient and have a phase velocity in the direction of the electron diamagnetic velocity that can reverse to the opposite direction as relevant parameters are varied over a relatively wide range. The electron temperature perturbation has a primary role in the relevant theory. In particular, when referring to regimes in which the longitudinal (to the magnetic field) electron thermal conductivity is relatively large, the electron temperature perturbation becomes singular if the ratio of the transverse to the longitudinal electron thermal conductivity becomes negligible.

  3. PROTON TEMPERATURE ANISOTROPY AND MAGNETIC RECONNECTION IN THE SOLAR WIND: EFFECTS OF KINETIC INSTABILITIES ON CURRENT SHEET STABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Matteini, L.; Landi, S.; Velli, M. [Dipartimento di Fisica e Astronomia, Universita degli Studi di Firenze, Largo E. Fermi 2, I-50125 Florence (Italy); Matthaeus, W. H. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

    2013-02-15

    We investigate the role of kinetic instabilities driven by a proton anisotropy on the onset of magnetic reconnection by means of two-dimensional hybrid simulations. The collisionless tearing of a current sheet is studied in the presence of a proton temperature anisotropy in the surrounding plasma. Our results confirm that anisotropic protons within the current sheet region can significantly enhance/stabilize the tearing instability of the current. Moreover, fluctuations associated with linear instabilities excited by large proton temperature anisotropies can significantly influence the stability of the plasma and perturb the current sheets, triggering the tearing instability. We find that such a complex coupling leads to a faster tearing evolution in the T{sub Up-Tack} > T{sub ||} regime when an ion-cyclotron instability is generated by the anisotropic proton distribution functions. On the contrary, in the presence of the opposite anisotropy, fire-hose fluctuations excited by the unstable background protons with T{sub ||} < T{sub Up-Tack} are not able to efficiently destabilize current sheets, which remain stable for a long time after fire-hose saturation. We discuss possible influences of this novel coupling on the solar wind and heliospheric plasma dynamics.

  4. Nanoflare heating model for collisionless solar corona

    Indian Academy of Sciences (India)

    Magnetic reconnection plays a significant role in heating the solar corona. When two oppositely directed magnetic fields come closer to form a current sheet, the current density of the plasma increases due to which magnetic reconnection and conversion of magnetic energy into thermal energy takes place. The present ...

  5. Nanoflare heating model for collisionless solar corona

    Indian Academy of Sciences (India)

    2017-01-31

    Jan 31, 2017 ... Magnetic reconnection plays a significant role in heating the solar corona. When two oppositely directed magnetic fields come closer to form a current sheet, the current density of the plasma increases due to which magnetic reconnection and conversion of magnetic energy into thermal energy takes place.

  6. Reconnection on the Sun

    Science.gov (United States)

    Kohler, Susanna

    2016-05-01

    Because the Sun is so close, it makes an excellent laboratory to study processes we cant examinein distant stars. One openquestion is that of how solar magnetic fields rearrange themselves, producing the tremendous releases of energy we observe as solar flares and coronal mass ejections (CMEs).What is Magnetic Reconnection?Magnetic reconnection occurs when a magnetic field rearranges itself to move to a lower-energy state. As field lines of opposite polarity reconnect, magnetic energy is suddenly converted into thermal and kinetic energy.This processis believed to be behind the sudden releases of energy from the solar surface in the form of solar flares and CMEs. But there are many different models for how magnetic reconnection could occur in the magnetic field at the Suns surface, and we arent sure which one of these reconnection types is responsible for the events we see.Recently, however, several studies have been published presenting some of the first observational support of specific reconnection models. Taken together, these observations suggest that there are likely several different types of reconnection happening on the solar surface. Heres a closer look at two of these recent publications:A pre-eruption SDO image of a flaring region (b) looks remarkably similar to a 3D cartoon for typical breakout configuration (a). Click for a closer look! [Adapted from Chen et al. 2016]Study 1:Magnetic BreakoutLed by Yao Chen (Shandong University in China), a team of scientists has presented observations made by the Solar Dynamics Observatory (SDO) of a flare and CME event that appears to have been caused by magnetic breakout.In the magnetic breakout model, a series of loops in the Suns lower corona are confined by a surrounding larger loop structure called an arcade higher in the corona. As the lower loops push upward, reconnection occurs in the upper corona, removing the overlying, confining arcade. Without that extra confinement, the lower coronal loops expand upward

  7. Introduction to Plasma Dynamo, Reconnection and Shocks

    Energy Technology Data Exchange (ETDEWEB)

    Intrator, Thomas P. [Los Alamos National Laboratory

    2012-08-30

    In our plasma universe, most of what we can observe is composed of ionized gas, or plasma. This plasma is a conducting fluid, which advects magnetic fields when it flows. Magnetic structure occurs from the smallest planetary to the largest cosmic scales. We introduce at a basic level some interesting features of non linear magnetohydrodynamics (MHD). For example, in our plasma universe, dynamo creates magnetic fields from gravitationally driven flow energy in an electrically conducting medium, and conversely magnetic reconnection annihilates magnetic field and accelerates particles. Shocks occur when flows move faster than the local velocity (sonic or Alfven speed) for the propagation of information. Both reconnection and shocks can accelerate particles, perhaps to gigantic energies, for example as observed with 10{sup 20} eV cosmic rays.

  8. Onset of Fast Magnetic Reconnection via Subcritical Bifurcation

    Directory of Open Access Journals (Sweden)

    ZHIBIN eGUO

    2015-04-01

    Full Text Available We report a phase transition model for the onset of fast magnetic reconnection. By investigating the joint dynamics of streaming instability(i.e., current driven ion acoustic in this paper and current gradient driven whistler wave {color{blue} {prior to the onset of fast reconnection}}, we show that the nonlinear evolution of current sheet(CS can be described by a Landau-Ginzburg equation. The phase transition from slow reconnection to fast reconnection occurs at a critical thickness, $Delta_csimeq frac{2}{sqrt{pi}}left|frac{v_{the}}{v_c}right|d_e$, where $v_{the}$ is electron thermal velocity and $v_c$ is the velocity threshold of the streaming instability. For current driven ion acoustic, $Delta_c$ is $leq10d_e$. If the thickness of the CS is narrower than $Delta_c$, the CS subcritically bifurcates into a rough state, which facilitates breakage of the CS, and consequently initiates fast reconnection.

  9. INTERCHANGE RECONNECTION AND CORONAL HOLE DYNAMICS

    International Nuclear Information System (INIS)

    Edmondson, J. K.; Antiochos, S. K.; DeVore, C. R.; Lynch, B. J.; Zurbuchen, T. H.

    2010-01-01

    We investigate the effect of magnetic reconnection between open and closed fields, often referred to as 'interchange' reconnection, on the dynamics and topology of coronal hole boundaries. The most important and most prevalent three-dimensional topology of the interchange process is that of a small-scale bipolar magnetic field interacting with a large-scale background field. We determine the evolution of such a magnetic topology by numerical solution of the fully three-dimensional MHD equations in spherical coordinates. First, we calculate the evolution of a small-scale bipole that initially is completely inside an open field region and then is driven across a coronal hole boundary by photospheric motions. Next the reverse situation is calculated in which the bipole is initially inside the closed region and driven toward the coronal hole boundary. In both cases, we find that the stress imparted by the photospheric motions results in deformation of the separatrix surface between the closed field of the bipole and the background field, leading to rapid current sheet formation and to efficient reconnection. When the bipole is inside the open field region, the reconnection is of the interchange type in that it exchanges open and closed fields. We examine, in detail, the topology of the field as the bipole moves across the coronal hole boundary and find that the field remains well connected throughout this process. Our results, therefore, provide essential support for the quasi-steady models of the open field, because in these models the open and closed flux are assumed to remain topologically distinct as the photosphere evolves. Our results also support the uniqueness hypothesis for open field regions as postulated by Antiochos et al. On the other hand, the results argue against models in which open flux is assumed to diffusively penetrate deeply inside the closed field region under a helmet streamer. We discuss the implications of this work for coronal observations.

  10. Nonthermal Particle Acceleration in 3D Relativistic Magnetic Reconnection in Pair Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Werner, Gregory R.; Uzdensky, Dmitri A., E-mail: Greg.Werner@colorado.edu [Center for Integrated Plasma Studies, Physics Department, University of Colorado, 390 UCB, Boulder, CO 80309 (United States)

    2017-07-10

    As a fundamental process converting magnetic to plasma energy in high-energy astrophysical plasmas, relativistic magnetic reconnection is a leading explanation for the acceleration of particles to the ultrarelativistic energies that are necessary to power nonthermal emission (especially X-rays and gamma-rays) in pulsar magnetospheres and pulsar wind nebulae, coronae and jets of accreting black holes, and gamma-ray bursts. An important objective of plasma astrophysics is therefore the characterization of nonthermal particle acceleration (NTPA) effected by reconnection. Reconnection-powered NTPA has been demonstrated over a wide range of physical conditions using large 2D kinetic simulations. However, its robustness in realistic 3D reconnection—in particular, whether the 3D relativistic drift-kink instability (RDKI) disrupts NTPA—has not been systematically investigated, although pioneering 3D simulations have observed NTPA in isolated cases. Here, we present the first comprehensive study of NTPA in 3D relativistic reconnection in collisionless electron–positron plasmas, characterizing NTPA as the strength of 3D effects is varied systematically via the length in the third dimension and the strength of the guide magnetic field. We find that, while the RDKI prominently perturbs 3D reconnecting current sheets, it does not suppress particle acceleration, even for zero guide field; fully 3D reconnection robustly and efficiently produces nonthermal power-law particle spectra closely resembling those obtained in 2D. This finding provides strong support for reconnection as the key mechanism powering high-energy flares in various astrophysical systems. We also show that strong guide fields significantly inhibit NTPA, slowing reconnection and limiting the energy available for plasma energization, yielding steeper and shorter power-law spectra.

  11. Colour reconnections in Herwig++

    OpenAIRE

    Gieseke, Stefan; Röhr, Christian; Siódmok, Andrzej

    2012-01-01

    We describe the implementation details of the colour reconnection model in the event generator Herwig++. We study the impact on final-state observables in detail and confirm the model idea from colour preconfinement on the basis of studies within the cluster hadronization model. Moreover, we show that the description of minimum bias and underlying event data at the LHC is improved with this model and present results of a tune to available data.

  12. Sub-grid-scale description of turbulent magnetic reconnection in magnetohydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Widmer, F., E-mail: widmer@mps.mpg.de [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen (Germany); Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Büchner, J. [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen (Germany); Yokoi, N. [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)

    2016-04-15

    Magnetic reconnection requires, at least locally, a non-ideal plasma response. In collisionless space and astrophysical plasmas, turbulence could transport energy from large to small scales where binary particle collisions are rare. We have investigated the influence of small scale magnetohydrodynamics (MHD) turbulence on the reconnection rate in the framework of a compressible MHD approach including sub-grid-scale (SGS) turbulence. For this sake, we considered Harris-type and force-free current sheets with finite guide magnetic fields directed out of the reconnection plane. The goal is to find out whether unresolved by conventional simulations MHD turbulence can enhance the reconnection process in high-Reynolds-number astrophysical plasmas. Together with the MHD equations, we solve evolution equations for the SGS energy and cross-helicity due to turbulence according to a Reynolds-averaged turbulence model. The SGS turbulence is self-generated and -sustained through the inhomogeneities of the mean fields. By this way, the feedback of the unresolved turbulence into the MHD reconnection process is taken into account. It is shown that the turbulence controls the regimes of reconnection by its characteristic timescale τ{sub t}. The dependence on resistivity was investigated for large-Reynolds-number plasmas for Harris-type as well as force-free current sheets with guide field. We found that magnetic reconnection depends on the relation between the molecular and apparent effective turbulent resistivity. We found that the turbulence timescale τ{sub t} decides whether fast reconnection takes place or whether the stored energy is just diffused away to small scale turbulence. If the amount of energy transferred from large to small scales is enhanced, fast reconnection can take place. Energy spectra allowed us to characterize the different regimes of reconnection. It was found that reconnection is even faster for larger Reynolds numbers controlled by the molecular

  13. Laboratory experiment to study collisionless shock

    Science.gov (United States)

    Kuramitsu, Y.; Sakawa, Y.; Morita, T.; Aoki, H.; Tanji, H.; Dono, S.; Waugh, J. N.; Gregory, C. D.; Koenig, M.; Woolsey, N.; Takabe, H.

    2010-08-01

    We report the experimental results of collisionless shock formation in counterstreaming plasmas produced by a high-power laser system. The experiment was performed with Gekko XII HIPER laser system at the Institute of Laser Engineering. In order to model collisionless shocks in the universe, supersonic counterstreaming plasma flows were generated using a CH double-plane target. By using the self-emission measurements, we observed the emission increase toward the shock through the downstream. We also observed the density jump associated with the emission increase. The width of the transition region is shorter than the ion-ion mean-free-path calculated from the measured plasma velocity and density.

  14. Magnetic reconnection in nontoroidal plasmas

    International Nuclear Information System (INIS)

    Boozer, Allen H.

    2005-01-01

    Magnetic reconnection is a major issue in solar and astrophysical plasmas. The mathematical result that the evolution of a magnetic field with only point nulls is always locally ideal limits the nature of reconnection in nontoroidal plasmas. Here it is shown that the exponentially increasing separation of neighboring magnetic field lines, which is generic, tends to produce rapid magnetic reconnection if the length of the field lines is greater than about 20 times the exponentiation, or Lyapunov, length

  15. Imaging Observations of Magnetic Reconnection in a Solar Eruptive Flare

    International Nuclear Information System (INIS)

    Li, Y.; Ding, M. D.; Sun, X.; Qiu, J.; Priest, E. R.

    2017-01-01

    Solar flares are among the most energetic events in the solar atmosphere. It is widely accepted that flares are powered by magnetic reconnection in the corona. An eruptive flare is usually accompanied by a coronal mass ejection, both of which are probably driven by the eruption of a magnetic flux rope (MFR). Here we report an eruptive flare on 2016 March 23 observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory . The extreme-ultraviolet imaging observations exhibit the clear rise and eruption of an MFR. In particular, the observations reveal solid evidence of magnetic reconnection from both the corona and chromosphere during the flare. Moreover, weak reconnection is observed before the start of the flare. We find that the preflare weak reconnection is of tether-cutting type and helps the MFR to rise slowly. Induced by a further rise of the MFR, strong reconnection occurs in the rise phases of the flare, which is temporally related to the MFR eruption. We also find that the magnetic reconnection is more of 3D-type in the early phase, as manifested in a strong-to-weak shear transition in flare loops, and becomes more 2D-like in the later phase, as shown by the apparent rising motion of an arcade of flare loops.

  16. Imaging Observations of Magnetic Reconnection in a Solar Eruptive Flare

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.; Ding, M. D. [School of Astronomy and Space Science, Nanjing University, Nanjing 210023 (China); Sun, X. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Qiu, J. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Priest, E. R., E-mail: yingli@nju.edu.cn [School of Mathematics and Statistics, University of St Andrews, Fife KY16 9SS, Scotland (United Kingdom)

    2017-02-01

    Solar flares are among the most energetic events in the solar atmosphere. It is widely accepted that flares are powered by magnetic reconnection in the corona. An eruptive flare is usually accompanied by a coronal mass ejection, both of which are probably driven by the eruption of a magnetic flux rope (MFR). Here we report an eruptive flare on 2016 March 23 observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory . The extreme-ultraviolet imaging observations exhibit the clear rise and eruption of an MFR. In particular, the observations reveal solid evidence of magnetic reconnection from both the corona and chromosphere during the flare. Moreover, weak reconnection is observed before the start of the flare. We find that the preflare weak reconnection is of tether-cutting type and helps the MFR to rise slowly. Induced by a further rise of the MFR, strong reconnection occurs in the rise phases of the flare, which is temporally related to the MFR eruption. We also find that the magnetic reconnection is more of 3D-type in the early phase, as manifested in a strong-to-weak shear transition in flare loops, and becomes more 2D-like in the later phase, as shown by the apparent rising motion of an arcade of flare loops.

  17. Application of PDSLin to the magnetic reconnection problem

    KAUST Repository

    Yuan, Xuefei

    2013-01-01

    Magnetic reconnection is a fundamental process in a magnetized plasma at both low and high magnetic Lundquist numbers (the ratio of the resistive diffusion time to the Alfvén wave transit time), which occurs in a wide variety of laboratory and space plasmas, e.g. magnetic fusion experiments, the solar corona and the Earth\\'s magnetotail. An implicit time advance for the two-fluid magnetic reconnection problem is known to be difficult because of the large condition number of the associated matrix. This is especially troublesome when the collisionless ion skin depth is large so that the Whistler waves, which cause the fast reconnection, dominate the physics (Yuan et al 2012 J. Comput. Phys. 231 5822-53). For small system sizes, a direct solver such as SuperLU can be employed to obtain an accurate solution as long as the condition number is bounded by the reciprocal of the floating-point machine precision. However, SuperLU scales effectively only to hundreds of processors or less. For larger system sizes, it has been shown that physics-based (Chacón and Knoll 2003 J. Comput. Phys. 188 573-92) or other preconditioners can be applied to provide adequate solver performance. In recent years, we have been developing a new algebraic hybrid linear solver, PDSLin (Parallel Domain decomposition Schur complement-based Linear solver) (Yamazaki and Li 2010 Proc. VECPAR pp 421-34 and Yamazaki et al 2011 Technical Report). In this work, we compare numerical results from a direct solver and the proposed hybrid solver for the magnetic reconnection problem and demonstrate that the new hybrid solver is scalable to thousands of processors while maintaining the same robustness as a direct solver. © 2013 IOP Publishing Ltd.

  18. Current sheets and pressure anisotropy in the reconnection exhaust

    International Nuclear Information System (INIS)

    Le, A.; Karimabadi, H.; Roytershteyn, V.; Egedal, J.; Ng, J.; Scudder, J.; Daughton, W.; Liu, Y.-H.

    2014-01-01

    A particle-in-cell simulation shows that the exhaust during anti-parallel reconnection in the collisionless regime contains a current sheet extending 100 inertial lengths from the X line. The current sheet is supported by electron pressure anisotropy near the X line and ion anisotropy farther downstream. Field-aligned electron currents flowing outside the magnetic separatrices feed the exhaust current sheet and generate the out-of-plane, or Hall, magnetic field. Existing models based on different mechanisms for each particle species provide good estimates for the levels of pressure anisotropy. The ion anisotropy, which is strong enough to reach the firehose instability threshold, is also important for overall force balance. It reduces the outflow speed of the plasma

  19. Reconnections of Wave Vortex Lines

    Science.gov (United States)

    Berry, M. V.; Dennis, M. R.

    2012-01-01

    When wave vortices, that is nodal lines of a complex scalar wavefunction in space, approach transversely, their typical crossing and reconnection is a two-stage process incorporating two well-understood elementary events in which locally coplanar hyperbolas switch branches. The explicit description of this reconnection is a pedagogically useful…

  20. Reconnecting to the biosphere.

    Science.gov (United States)

    Folke, Carl; Jansson, Asa; Rockström, Johan; Olsson, Per; Carpenter, Stephen R; Chapin, F Stuart; Crépin, Anne-Sophie; Daily, Gretchen; Danell, Kjell; Ebbesson, Jonas; Elmqvist, Thomas; Galaz, Victor; Moberg, Fredrik; Nilsson, Måns; Osterblom, Henrik; Ostrom, Elinor; Persson, Asa; Peterson, Garry; Polasky, Stephen; Steffen, Will; Walker, Brian; Westley, Frances

    2011-11-01

    Humanity has emerged as a major force in the operation of the biosphere, with a significant imprint on the Earth System, challenging social-ecological resilience. This new situation calls for a fundamental shift in perspectives, world views, and institutions. Human development and progress must be reconnected to the capacity of the biosphere and essential ecosystem services to be sustained. Governance challenges include a highly interconnected and faster world, cascading social-ecological interactions and planetary boundaries that create vulnerabilities but also opportunities for social-ecological change and transformation. Tipping points and thresholds highlight the importance of understanding and managing resilience. New modes of flexible governance are emerging. A central challenge is to reconnect these efforts to the changing preconditions for societal development as active stewards of the Earth System. We suggest that the Millennium Development Goals need to be reframed in such a planetary stewardship context combined with a call for a new social contract on global sustainability. The ongoing mind shift in human relations with Earth and its boundaries provides exciting opportunities for societal development in collaboration with the biosphere--a global sustainability agenda for humanity.

  1. Global dynamics of magnetic reconnection in VINETA II

    International Nuclear Information System (INIS)

    Bohlin, Hannes

    2014-01-01

    Magnetic reconnection is a fundamental plasma process where a change in field line connectivity occurs in a current sheet at the boundary between regions of opposing magnetic fields. In this process, energy stored in the magnetic field is converted into kinetic and thermal energy, which provides a source of plasma heating and energetic particles. Magnetic reconnection plays a key role in many space and laboratory plasma phenomena, e.g. solar flares, Earth's magnetopause dynamics and instabilities in tokamaks. A new linear device (VINETAII) has been designed for the study of the fundamental physical processes involved in magnetic reconnection. The plasma parameters are such that magnetic reconnection occurs in a collision-dominated regime. A plasma gun creates a localized current sheet, and magnetic reconnection is driven by modulating the plasma current and the magnetic field structure. The plasma current is shown to flow in response to a combination of an externally induced electric field and electrostatic fields in the plasma, and is highly affected by axial sheath boundary conditions. Further, the current is changed by an additional axial magnetic field (guide field), and the current sheet geometry was demonstrated to be set by a combination of magnetic mapping and cross-field plasma diffusion. With increasing distance from the plasma gun, magnetic mapping results in an increase of the current sheet length and a decrease of the width. The control parameter is the ratio of the guide field to the reconnection magnetic field strength. Cross-field plasma diffusion leads to a radial expansion of the current sheet at low guide fields. Plasma currents are also observed in the azimuthal plane and were found to originate from a combination of the field-aligned current component and the diamagnetic current generated by steep in-plane pressure gradients in combination with the guide field. The reconnection rate, defined via the inductive electric field, is shown to be

  2. Interchange Slip-Running Reconnection and Sweeping SEP-Beams

    Science.gov (United States)

    Masson, S.; Aulanier, G.; Pariat, E.; Klein, K.-L.

    2011-01-01

    We present a new model to explain how particles, accelerated at a reconnection site that is not magnetically connected to the Earth, could eventually propagate along the well-connected open flux tube. Our model is based on the results of a low-beta resistive magnetohydrodynamics simulation of a three-dimensional line-tied and initially current-free bipole, that is embedded in a non-uniform open potential field. The topology of this configuration is that of an asymmetric coronal null-point, with a closed fan surface and an open outer spine. When driven by slow photospheric shearing motions, field lines, initially fully anchored below the fan dome, reconnect at the null point, and jump to the open magnetic domain. This is the standard interchange mode as sketched and calculated in 2D. The key result in 3D is that, reconnected open field lines located in the vicinity of the outer spine, keep reconnecting continuously, across an open quasi-separatrix layer, as previously identified for non-open-null-point reconnection. The apparent slipping motion of these field lines leads to form an extended narrow magnetic flux tube at high altitude. Because of the slip-running reconnection, we conjecture that if energetic particles would be travelling through, or be accelerated inside, the diffusion region, they would be successively injected along continuously reconnecting field lines that are connected farther and farther from the spine. At the scale of the full Sun, owing to the super-radial expansion of field lines below 3 solar radius, such energetic particles could easily be injected in field lines slipping over significant distances, and could eventually reach the distant flux tube that is well-connected to the Earth.

  3. The microphysics of collisionless shock waves

    DEFF Research Database (Denmark)

    Marcowith, Alexandre; Bret, Antoine; Bykov, Andrei

    2016-01-01

    Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active...... galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space....... It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments...

  4. Localized tearing modes in the magnetotail driven by curvature effects

    Energy Technology Data Exchange (ETDEWEB)

    Sundaram, A.K.; Fairfield, D.H. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

    1995-03-01

    The stability of collisionless tearing modes is examined in the presence of curvature drift resonances and the trapped particle effects. A kinetic description for both electrons and ions is employed to investigate the stability of a two-dimensional equilibrium model. The main features of the study are to treat the ion dynamics properly by incorporating effects associated with particle trajectories in the tail fields and to include the linear coupling of trapped particle modes. Generalized dispersion relations are derived in several parameter regimes by considering two important sublayers of the reconnecting region. For a typical choice of parameters appropriate to the current sheet region, the authors demonstrate that localized tearing modes driven by ion curvature drift resonance effects are excited in the current sheet region with growth time of the order of a few seconds. Also, they examine nonlocal characteristics of tearing modes driven by curvature effects and show that modes growing in a fraction of a second arise when mode widths are larger than the current sheet width. Further, they show that trapped particle effects, in an interesting frequency regime, significantly enhance the growth rate of the tearing mode. The relevance of this theory for substorm onset phase and other features of the substorms is briefly discussed. 38 refs.

  5. Numerical simulations of collisionless drift instabilities for low-density plasmas

    International Nuclear Information System (INIS)

    Lee, W.W.; Yau, Y.Y.K.; Okuda, H.

    1977-10-01

    Nonlinear behavior of the collisionless drift instabilities are studied for the universal and current driven modes by means of electrostatic particle simulations in two-and-a-half dimensions. Realistic mass ratios of the electrons to the ions are used in the simulations, where the guiding-center approximation for the electrons and the exact dynamics for the ions are employed. Several nonlinear effects including the quasilinear diffusion of the particle density, the frequency shift due to the ambipolar field, the mode competition among the unstable waves, and the quasilinear diffusion in the velocity space are found to be the dominant mechanisms for the saturation. The stabilization of the collisionless drift instabilities by the magnetic shear has also been studied

  6. Collisionless shocks in laser-produced plasma generate monoenergetic high-energy proton beams

    Science.gov (United States)

    Haberberger, Dan; Tochitsky, Sergei; Fiuza, Frederico; Gong, Chao; Fonseca, Ricardo A.; Silva, Luis O.; Mori, Warren B.; Joshi, Chan

    2012-01-01

    Compact and affordable ion accelerators based on laser-produced plasmas have potential applications in many fields of science and medicine. However, the requirement of producing focusable, narrow-energy-spread, energetic beams has proved to be challenging. Here we demonstrate that laser-driven collisionless shocks can accelerate proton beams to ~20MeV with extremely narrow energy spreads of about 1% and low emittances. This is achieved using a linearly polarized train of multiterawatt CO2 laser pulses interacting with a gas-jet target. Computer simulations show that laser-heated electrons launch a collisionless shock that overtakes and reflects the protons in the slowly expanding hydrogen plasma, resulting in a narrow energy spectrum. Simulations predict the production of ~200MeV protons needed for radiotherapy by using current laser technology. These results open a way for developing a compact and versatile, high-repetition-rate ion source for medical and other applications.

  7. Plasma pressure tensor effects on reconnection: Hybrid and Hall-magnetohydrodynamics simulations

    International Nuclear Information System (INIS)

    Yin Lin; Winske, Dan

    2003-01-01

    Collisionless reconnection is studied using two-dimensional (2-D) hybrid (particle ions, massless fluid electrons) and Hall-magnetohydrodynamics (Hall-MHD) simulations. Both use the full electron pressure tensor instead of a localized resistivity in Ohm's law to initiate reconnection; an initial perturbation or boundary driving to the equilibrium is used. The initial configurations include one-dimensional (1-D) and 2-D current sheets both with and without a guide field. Electron dynamics from the two calculations are compared, and overall agreement is found between the calculations in both reconnection rate and global configuration [L. Yin et al., J. Geophys. Res. 106, 10761 (2001)]. It is shown that the electron drifts in the small-transverse-scale fields near the X point cause the electron motion to decouple from the ion motion, and that reconnection occurs due to electron viscous effects contained in the off-diagonal terms of the electron pressure tensor. Comparing the hybrid and Hall-MHD simulations shows that effects of the off-diagonal terms in the ion pressure tensor, i.e., the ion gyro-radius effects, are necessary in order to model correctly the ion out-of-plane motion. It is shown that these effects can be modeled efficiently in a particle Hall-MHD simulation in which particle ions are used in a predictor/corrector manner to implement ion gyro-radius corrections [L. Yin et al., Phys. Plasmas 9, 2575 (2002)]. For modeling reconnection in large systems, a new integrated approach is examined in which Hall-MHD calculations using a full electron pressure tensor model is embedded inside a MHD simulation. The embedded simulation of current sheet thinning and reconnection dynamics in a realistic 2-D magnetotail equilibrium exhibits smooth transitions of plasma and field quantities between the two regions, with small-scale physics represented well in the compressed current sheet and in the near-X-point region

  8. A Reconnection Switch to Trigger gamma-Ray Burst Jet Dissipation

    Energy Technology Data Exchange (ETDEWEB)

    McKinney, Jonathan C.; Uzdensky, Dmitri A.

    2012-03-14

    Prompt gamma-ray burst (GRB) emission requires some mechanism to dissipate an ultrarelativistic jet. Internal shocks or some form of electromagnetic dissipation are candidate mechanisms. Any mechanism needs to answer basic questions, such as what is the origin of variability, what radius does dissipation occur at, and how does efficient prompt emission occur. These mechanisms also need to be consistent with how ultrarelativistic jets form and stay baryon pure despite turbulence and electromagnetic reconnection near the compact object and despite stellar entrainment within the collapsar model. We use the latest magnetohydrodynamical models of ultrarelativistic jets to explore some of these questions in the context of electromagnetic dissipation due to the slow collisional and fast collisionless reconnection mechanisms, as often associated with Sweet-Parker and Petschek reconnection, respectively. For a highly magnetized ultrarelativistic jet and typical collapsar parameters, we find that significant electromagnetic dissipation may be avoided until it proceeds catastrophically near the jet photosphere at large radii (r {approx} 10{sup 13}-10{sup 14}cm), by which the jet obtains a high Lorentz factor ({gamma} {approx} 100-1000), has a luminosity of L{sub j} {approx} 10{sup 50}-10{sup 51} erg s{sup -1}, has observer variability timescales of order 1s (ranging from 0.001-10s), achieves {gamma}{theta}{sub j} {approx} 10-20 (for opening half-angle {theta}{sub j}) and so is able to produce jet breaks, and has comparable energy available for both prompt and afterglow emission. A range of model parameters are investigated and simplified scaling laws are derived. This reconnection switch mechanism allows for highly efficient conversion of electromagnetic energy into prompt emission and associates the observed prompt GRB pulse temporal structure with dissipation timescales of some number of reconnecting current sheets embedded in the jet. We hope this work helps motivate the

  9. Magnetic Reconnection in Solar Flares

    Science.gov (United States)

    Forbes, Terry G.

    2016-05-01

    Reconnection has at least three possible roles in solar flares: First, it may contribute to the build-up of magnetic energy in the solar corona prior to flare onset; second, it may directly trigger the onset of the flare; and third, it may allow the release of magnetic energy by relaxing the magnetic field configuration to a lower energy state. Although observational support for the first two roles is somewhat limited, there is now ample support for the third. Within the last few years EUV and X-ray instruments have directly observed the kind of plasma flows and heating indicative of reconnection. Continued improvements in instrumentation will greatly help to determine the detailed physics of the reconnection process in the solar atmosphere. Careful measurement of the reconnection outflows will be especially helpful in this regard. Current observations suggest that in some flares the jet outflows are accelerated within a short diffusion region that is more characteristic of Petschek-type reconnection than Sweet-Parker reconnection. Recent resistive MHD theoretical and numerical analyses predict that the length of the diffusion region should be just within the resolution range of current X-ray and EUV telescopes if the resistivity is uniform. On the other hand, if the resistivity is not uniform, the length of the diffusion region could be too short for the outflow acceleration region to be observable.

  10. Magnetohydrodynamic study of three-dimensional instability of the spontaneous fast magnetic reconnection

    International Nuclear Information System (INIS)

    Shimizu, T.; Kondoh, K.; Ugai, M.; Shibata, K.

    2009-01-01

    Three-dimensional instability of the spontaneous fast magnetic reconnection is studied with magnetohydrodynamic (MHD) simulation, where the two-dimensional model of the spontaneous fast magnetic reconnection is destabilized in three dimension. Generally, in two-dimensional magnetic reconnection models, every plasma condition is assumed to be uniform in the sheet current direction. In such two-dimensional MHD simulations, the current sheet destabilized by the initial resistive disturbance can be developed to fast magnetic reconnection by a current driven anomalous resistivity. In this paper, the initial resistive disturbance includes a small amount of fluctuations in the sheet current direction, i.e., along the magnetic neutral line. The other conditions are the same as that of previous two-dimensional MHD studies for fast magnetic reconnection. Accordingly, we may expect that approximately two-dimensional fast magnetic reconnection occurs in the MHD simulation. In fact, the fast magnetic reconnection activated on the first stage of the simulation is two dimensional. However, on the subsequent stages, it spontaneously becomes three dimensional and is strongly localized in the sheet current direction. The resulting three-dimensional fast magnetic reconnection intermittently ejects three-dimensional magnetic loops. Such intermittent ejections of the three-dimensional loops are similar to the intermittent downflows observed in the solar flares. The ejection of the three-dimensional loops seems to be random but, numerically and theoretically, it is shown that the aspect ratio of the ejected loops is limited under a criterion.

  11. Nanoflare heating model for collisionless solar corona

    Indian Academy of Sciences (India)

    2017-01-31

    Jan 31, 2017 ... fields come closer to form a current sheet, the current density of the plasma increases due to which magnetic reconnection and conversion of ... This current sheet of finite region is called diffusion region. The energy of the .... (6) we can balance the advection ve ×B with electron pressure tensor. Erec = ve ...

  12. Reconnecting Eye to Brain.

    Science.gov (United States)

    Crair, Michael C; Mason, Carol A

    2016-10-19

    Although much is known about the regenerative capacity of retinal ganglion cells, very significant barriers remain in our ability to restore visual function following traumatic injury or disease-induced degeneration. Here we summarize our current understanding of the factors regulating axon guidance and target engagement in regenerating axons, and review the state of the field of neural regeneration, focusing on the visual system and highlighting studies using other model systems that can inform analysis of visual system regeneration. This overview is motivated by a Society for Neuroscience Satellite meeting, "Reconnecting Neurons in the Visual System," held in October 2015 sponsored by the National Eye Institute as part of their "Audacious Goals Initiative" and co-organized by Carol Mason (Columbia University) and Michael Crair (Yale University). The collective wisdom of the conference participants pointed to important gaps in our knowledge and barriers to progress in promoting the restoration of visual system function. This article is thus a summary of our existing understanding of visual system regeneration and provides a blueprint for future progress in the field. Copyright © 2016 the authors 0270-6474/16/3610707-16$15.00/0.

  13. Overview and first results of experiments on magnetic reconnection between colliding magnetized plasmas at the National Ignition Facility

    Science.gov (United States)

    Fox, W.; Rosenberg, M.; Schaeffer, D.; Fiksel, G.; Park, H. S.; Kalantar, D.; Bhattacharjee, A.; Huang, Y.-M.; Ji, H.; Matteucci, J.; Gao, L.; Uzdensky, D.; Birkel, A.; Li, C. K.; Hu, S. X.; Shvydky, A.

    2017-10-01

    Expanding laser-produced plasmas naturally self-generate magnetic fields by the Biermann battery effect, and the collision of two plumes can drive magnetic reconnection. The National Ignition Facility at LLNL occupies a unique position for laser-driven magnetic reconnection experiments by simultaneously allowing very large plasma temperature, low plasma resistivity, and large system size, which allows observation of secondary instabilities driven during magnetic reconnection and particle acceleration relevant to astrophysical plasmas. Magnetic reconnection experiments have been conducted on the NIF through the NIF Discovery Science program with the first experimental shots conducted in May 2017. We will present the design of the experimental platform and results from the first experimental day. Magnetic reconnection data is obtained from proton radiography based on a DHe3 backlighter, x-ray self-emission, and a new low-energy particle spectrometer (NIF EPPS-300G) developed by the NIF Facility and Engineering and fielded for the first time on these experiments.

  14. Stability of spherical gravitating collisionless systems

    Energy Technology Data Exchange (ETDEWEB)

    Polyachenko, V.L.

    1988-03-01

    A unified method that uses a procedure, established in the paper, for reducing the problem of the stability of a spherical system to the analogous problem of perturbations of the simplest form in a corresponding cylindrical system provides the framework for investigating the stability of collisionless star clusters with different types of anisotropy of the velocity distribution. For spherical systems embedded in a massive halo or possessing a large central mass, equations - in the simplest case integral equations - for the eigenfunctions and eigenfrequencies of the oscillations are derived.

  15. Kinetic instabilities in plasmas: from electromagnetic fluctuations to collisionless shocks

    International Nuclear Information System (INIS)

    Ruyer, Charles

    2014-01-01

    -in-cell (PIC) simulations of the ion Weibel instability in uniform geometries, as well as shock-relevant non-uniform configurations. Moreover, they are found in correct agreement with a recent laser-driven plasma collision experiment. Along with this comparison, we pinpoint the important role of electron screening on the ion-Weibel dynamics, which may affect the results of simulations with artificially high electron mass. We subsequently address the shock propagation resulting from the magnetic Weibel turbulence generated in the upstream region. Generalizing the previous symmetric-beam model to the upstream region of the shock, the role of the magnetic turbulence in the shock-front has been analytically and self-consistently characterized. Comparison with simulations validates the model. The interaction of high-energy, ultra-high intensity lasers with dense plasmas is known to produce copious amounts of suprathermal particles. Their acceleration and subsequent transport trigger a variety of Weibel-like electromagnetic instabilities, acting as additional sources of slowing down and scattering. Their understanding is important for the many applications based upon the energy deposition and/or field generation of laser-driven particles. We investigate the ability of relativistic-intensity laser pulses to induce Weibel instability-mediated shocks in overdense plasma targets, as first proposed by Fiuza in 2012. By means of both linear theory and 2D PIC simulations, we demonstrated that in contrast to the standard astrophysical scenario previously addressed, the early-time magnetic fluctuations (Weibel instability) generated by the suprathermal electrons (and not ions) are strong enough to isotropize the target ions and, therefore, induce a collisionless electromagnetic shock. (author) [fr

  16. Resonance suppression from color reconnection

    Science.gov (United States)

    Acconcia, R.; Chinellato, D. D.; de Souza, R. Derradi; Takahashi, J.; Torrieri, G.; Markert, C.

    2018-02-01

    We present studies that show how multi-parton interaction and color reconnection affect the hadro-chemistry in proton-proton (pp) collisions with special focus on the production of resonances using the pythia8 event generator. We find that color reconnection suppresses the relative production of meson resonances such as ρ0 and K* , providing an alternative explanation for the K*/K decrease observed in proton-proton collisions as a function of multiplicity by the ALICE collaboration. Detailed studies of the underlying mechanism causing meson resonance suppression indicate that color reconnection leads to shorter, less energetic strings whose fragmentation is less likely to produce more massive hadrons for a given quark content, therefore reducing ratios such as K*/K and ρ0/π in high-multiplicity pp collisions. In addition, we have also studied the effects of allowing string junctions to form and found that these may also contribute to resonance suppression.

  17. A Magnetic Reconnection Mechanism for the Generation of Anomalous Cosmic Rays

    Science.gov (United States)

    Drake, J. F.; Opher, M.; Swisdak, M.; Chamoun, J. N.

    2010-02-01

    The recent observations of the anomalous cosmic ray (ACR) energy spectrum as Voyager 1 and Voyager 2 crossed the heliospheric termination shock have called into question the conventional shock source of these energetic particles. We suggest that the sectored heliospheric magnetic field, which results from the flapping of the heliospheric current sheet, piles up as it approaches the heliopause, narrowing the current sheets that separate the sectors and triggering the onset of collisionless magnetic reconnection. Particle-in-cell simulations reveal that most of the magnetic energy is released and most of this energy goes into energetic ions with significant but smaller amounts of energy going into electrons. The energy gain of the most energetic ions results from their reflection from the ends of contracting magnetic islands, a first-order Fermi process. The energy gain of the ions in contracting islands increases their parallel (to the magnetic field B) pressure p par until the marginal fire-hose condition is reached, causing magnetic reconnection and associated particle acceleration to shut down. Thus, the feedback of the self-consistent development of the energetic ion pressure on reconnection is a crucial element of any reconnection-based, particle-acceleration model. The model calls into question the strong scattering assumption used to derive the Parker transport equation and therefore the absence of first-order Fermi acceleration in incompressible flows. A simple one-dimensional model for particle energy gain and loss is presented in which the feedback of the energetic particles on the reconnection drive is included. The ACR differential energy spectrum takes the form of a power law with a spectral index slightly above 1.5. The model has the potential to explain several key Voyager observations, including the similarities in the spectra of different ion species.

  18. Magnetohydrodynamic study for three-dimensional instability of the Petschek type magnetic reconnection

    International Nuclear Information System (INIS)

    Shimizu, T.; Kondoh, K.

    2013-01-01

    The 3D instability of the spontaneous fast magnetic reconnection process is studied with magnetohydrodynamics (MHD) simulations, where the 2D model of the spontaneous fast magnetic reconnection is destabilized in three dimension. As well known in many 2D numerical MHD studies, when a 1D current sheet is destabilized with the current-driven anomalous resistivity, the 2D Petschek type fast magnetic reconnection is established. This paper shows that the 2D Petschek type fast magnetic reconnection can be destabilized in three dimension by an initial resistive disturbance which includes a weak fluctuation in the sheet current direction, i.e., along the magnetic neutral line. The resulting 3D fast magnetic reconnection finally becomes intermittent and random through a 3D instability. In addition, it is also shown that the 3D instability is suppressed by the uniform resistivity. It suggests that the 3D instability is caused in the Petschek-type reconnection process which is characterized by a strongly localized magnetic diffusion region and the slow shock acceleration of the plasma jets and is suppressed in the Sweet-Parker type reconnection process

  19. Flare magnetic reconnection fluxes as possible signatures of flare contributions to gradual SEP events

    Science.gov (United States)

    Kahler, S. W.; Kazachenko, M.; Lynch, B. J.; Welsch, B. T.

    2017-09-01

    The primary sources of solar energetic (E > 20 MeV) particle (SEP) events are flares and CME-driven shocks. Some studies claim that even up to GeV energies solar flares are major contributors to SEP events. There are several candidate flare processes for producing SEPs, but acceleration in magnetic reconnection regions is probably the most efficient. Previous studies have relied on flare radiation signatures to determine the times and locations of SEP injections. An alternative approach is to use the amount of magnetic flux that gets reconnected during solar flares. The photospheric magnetic flux swept out by flare ribbons is thought to be directly related to the amount of magnetic reconnection in the corona and is therefore a key diagnostic tool for understanding the physical processes in flares and CMEs. We use the database of flare magnetic reconnection fluxes to compare these parameters with peak intensities of SEP events. We find that while sizes of 15 ∼25-MeV SEP events in the western hemisphere correlate with both CME speeds and reconnection fluxes, there are many cases of large reconnection fluxes with no observed SEP events. The occurrence of large reconnection fluxes accompanied by slow CMEs but no SEP events suggests that the CME shocks are the primary, if not the only, sources of high energy (E > 100 MeV) SEP events.

  20. Hall MHD Modeling of Two-dimensional Reconnection: Application to MRX Experiment

    International Nuclear Information System (INIS)

    Lukin, V.S.; Jardin, S.C.

    2003-01-01

    Two-dimensional resistive Hall magnetohydrodynamics (MHD) code is used to investigate the dynamical evolution of driven reconnection in the Magnetic Reconnection Experiment (MRX). The initial conditions and dimensionless parameters of the simulation are set to be similar to the experimental values. We successfully reproduce many features of the time evolution of magnetic configurations for both co- and counter-helicity reconnection in MRX. The Hall effect is shown to be important during the early dynamic X-phase of MRX reconnection, while effectively negligible during the late ''steady-state'' Y-phase, when plasma heating takes place. Based on simple symmetry considerations, an experiment to directly measure the Hall effect in MRX configuration is proposed and numerical evidence for the expected outcome is given

  1. Weakly Collisional and Collisionless Astrophysical Plasmas

    DEFF Research Database (Denmark)

    Berlok, Thomas

    associated with the ions and is thus well suited for studying collisionless plasmas. We have developed a new 2D-3V Vlasov-fluid code which works by evolving the phase-space density distribution of the ions while treating the electrons as an inertialess fluid. The code uses the particle-incell (PIC) method...... and several options for particle interpolation (cloud-in-cell and triangular-shaped-cloud) and several methods for updating the equations in time ( the predictor-corrector and the Horowitz method) are provided. The programming language Python has been chosen for its usability but high performance...... instability and simulations of waves, such as the ion-acoustic, ion Bernstein, ion-cyclotron and whistler waves. The thesis also contains a general introduction to the PIC method including a discussion of aliasing due to the numerical grid and the finite grid instability. We furthermore study ion...

  2. Electrostatic effect for the collisionless tearing mode

    International Nuclear Information System (INIS)

    Hoshino, M.

    1987-01-01

    Electron dynamics has not been self-consistently considered in collisionless tearing mode theories to date because of the mathematical complexity of the Vlasov-Maxwell equations. We have found using computer simulations that electrostatic fields play an important role in the tearing mode. Vlasov theory, including the electrostatic field, is investigated for topologies with both antiparallel and nonantiparallel magnetic field lines. The electrostatic field influences the resonant current in the neutral sheet which is a non-MHD effect, and modifies the linear growth rate. At the magnetopause, where the field lines are not antiparallel, the electrostatic effect acts to raise the linear growth rate of the tearing mode. On the other hand, in the magnetotail, where magnetic field lines are antiparallel, the electrostatic effect reduces the tearing mode growth rate. copyright American Geophysical Union 1987

  3. Final Technical Report: Magnetic Reconnection in High-Energy Laser-Produced Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Germaschewski, Kai [Univ. of New Hampshire, Durham, NH (United States); Fox, William [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Bhattacharjee, Amitava [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

    2017-04-06

    This report describes the final results from the DOE Grant DE-SC0007168, “Fast Magnetic Reconnection in HED Laser-Produced Plasmas.” The recent generation of laboratory high-energy-density physics facilities has opened significant physics opportunities for experimentally modeling astrophysical plasmas. The goal of this proposal is to use these new tools to study fundamental problems in plasma physics and plasma astrophysics. Fundamental topics in this area involve study of the generation, amplification, and fate of magnetic fields, which are observed to pervade the plasma universe and govern its evolution. This project combined experiments at DOE laser facilities with kinetic plasma simulation to study these processes. The primary original goal of the project was to study magnetic reconnection using a new experimental platform, colliding magnetized laser-produced plasmas. However through a series of fortuitous discoveries, the work broadened out to allow significant advancement on multiple topics in laboratory astrophysics, including magnetic reconnection, Weibel instability, and collisionless shocks.

  4. Understanding the energetics of magnetic reconnection with the presence of waves in laboratory plasmas

    Science.gov (United States)

    Yamada, M.; Yoo, J.; Ji, H.; Jara-Almonte, J.; Fox, W.; Kulsrud, R. M.

    2017-12-01

    In spite of the huge difference (106-107) in physical scales, we find remarkable commonality between the properties and the dynamics of the collisionless reconnection layer in laboratory and space plasmas. The recent significant progress in diagnostics in the both fields made us possible to directly compare the observed physics processes. At first experimental results on the energy conversion and partitioning are discussed and compared with quantitative estimates based on two-fluid analysis as well as space observations. We observed notable similarity in the energy partitioning in the reconnection layer of the MRX results and space observations [1,2]. Furthermore, we have observed whistler waves and lower-hybrid frequency fluctuations at the lower density side of asymmetric reconnection layer on MRX [2]. The experimental results are remarkably consistent with the recent space observations from MMS [3]. We plan to systematically vary the guide field strength to critically test the validity and universality of plasma waves and their consequences on the energy dissipation to electrons. We directly compare the data from the MRX and the recent MMS observations which show very similar power spectra. Ref.: [1] M. Yamada, et al, PoP 23, 055402 (2016), [2] J. Yoo et al, in press J. G.R. (2017), [3] L. J. Chen et al, tom be published.

  5. MAGNETOHYDRODYNAMICS STUDY OF THREE-DIMENSIONAL FAST MAGNETIC RECONNECTION FOR INTERMITTENT SNAKE-LIKE DOWNFLOWS IN SOLAR FLARES

    International Nuclear Information System (INIS)

    Shimizu, T.; Kondo, K.; Ugai, M.; Shibata, K.

    2009-01-01

    Three-dimensional instability of the spontaneous fast magnetic reconnection is studied with magnetohydrodynamics (MHD) simulation, where the two-dimensional model of the spontaneous fast magnetic reconnection is destabilized in three dimensions. In two-dimensional models, every plasma condition is assumed to be uniform in the sheet current direction. In that case, it is well known that the two-dimensional fast magnetic reconnection can be caused by current-driven anomalous resistivity, when an initial resistive disturbance is locally put in a one-dimensional current sheet. In this paper, it is studied whether the two-dimensional fast magnetic reconnection can be destabilized or not when the initial resistive disturbance is three dimensional, i.e., that which has weak fluctuations in the sheet current direction. According to our study, the two-dimensional fast magnetic reconnection is developed to the three-dimensional intermittent fast magnetic reconnection which is strongly localized in the sheet current direction. The resulting fast magnetic reconnection repeats to randomly eject three-dimensional magnetic loops which are very similar to the intermittent downflows observed in solar flares. In fact, in some observations of solar flares, the current sheet seems to be approximately one dimensional, but the fast magnetic reconnection is strongly localized in the sheet current direction, i.e., fully three dimensional. In addition, the observed plasma downflows as snake-like curves. It is shown that those observed features are consistent with our numerical MHD study.

  6. Spectroscopic Signature of Bursty Reconnection

    Science.gov (United States)

    Schmit, D. J.; Innes, D.; Barta, M.

    2013-12-01

    Bursty reconnection is thought to play a central role in explosive events in the solar atmosphere. Time dependent reconnection occurs when a current sheet undergoes tearing and coalescence instabilities. We simulate these dynamics using a 2.5D adiabatic dimensionless single-fluid MHD model. We scale the model output into the regime appropriate for the upper chromosphere and forward model time dependent spectral profiles which incorporate the projection effects of viewing angle and temperature sensitivity. We find that the profiles are often bimodal and red wing dominant. Both red and blue shifted peaks are visible at velocities 40% of the Alfven speed outside the current sheet. This spectral modeling provides a platform for direct comparison with the novel dataset to be provided by IRIS, particularly in the context of jets and flares.

  7. Multiscale Processes in Magnetic Reconnection

    Science.gov (United States)

    Surjalal Sharma, A.; Jain, Neeraj

    The characteristic scales of the plasma processes in magnetic reconnection range from the elec-tron skin-depth to the magnetohydrodynamic (MHD) scale, and cross-scale coupling among them play a key role. Modeling these processes requires different physical models, viz. kinetic, electron-magnetohydrodynamics (EMHD), Hall-MHD, and MHD. The shortest scale processes are at the electron scale and these are modeled using an EMHD code, which provides many features of the multiscale behavior. In simulations using initial conditions consisting of pertur-bations with many scale sizes the reconnection takes place at many sites and the plasma flows from these interact with each other. This leads to thin current sheets with length less than 10 electron skin depths. The plasma flows also generate current sheets with multiple peaks, as observed by Cluster. The quadrupole structure of the magnetic field during reconnection starts on the electron scale and the interaction of inflow to the secondary sites and outflow from the dominant site generates a nested structure. In the outflow regions, the interaction of the electron outflows generated at the neighboring sites lead to the development of electron vortices. A signature of the nested structure of the Hall field is seen in Cluster observations, and more details of these features are expected from MMS.

  8. Nonlinear theory of collisionless trapped ion modes

    International Nuclear Information System (INIS)

    Hahm, T.S.; Tang, W.M.

    1996-01-01

    A simplified two field nonlinear model for collisionless trapped-ion-mode turbulence has been derived from nonlinear bounce-averaged drift kinetic equations. The renormalized thermal diffusivity obtained from this analysis exhibits a Bohm-like scaling. A new nonlinearity associated with the neoclassical polarization density is found to introduce an isotope-dependent modification to this Bohm-like diffusivity. The asymptotic balance between the equilibrium variation and the finite banana width induced reduction of the fluctuation potential leads to the result that the radial correlation length decreases with increasing plasma current. Other important conclusions from the present analysis include the predictions that (i) the relative density fluctuation level δn/n 0 is lower than the conventional mixing length estimate, Δr/L n (ii) the ion temperature fluctuation level δT i /T i significantly exceeds the density fluctuation level δn/n 0 ; and (iii) the parallel ion velocity fluctuation level δv iparallel /v Ti is expected to be negligible

  9. Collisionless microinstabilities in stellarators. II. Numerical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Proll, J. H. E.; Xanthopoulos, P.; Helander, P. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Wendelsteinstraße 1, 17491 Greifswald, Germany and Max-Planck/Princeton Research Center for Plasma Physics, 17491 Greifswald (Germany)

    2013-12-15

    Microinstabilities exhibit a rich variety of behavior in stellarators due to the many degrees of freedom in the magnetic geometry. It has recently been found that certain stellarators (quasi-isodynamic ones with maximum-J geometry) are partly resilient to trapped-particle instabilities, because fast-bouncing particles tend to extract energy from these modes near marginal stability. In reality, stellarators are never perfectly quasi-isodynamic, and the question thus arises whether they still benefit from enhanced stability. Here, the stability properties of Wendelstein 7-X and a more quasi-isodynamic configuration, QIPC, are investigated numerically and compared with the National Compact Stellarator Experiment and the DIII-D tokamak. In gyrokinetic simulations, performed with the gyrokinetic code GENE in the electrostatic and collisionless approximation, ion-temperature-gradient modes, trapped-electron modes, and mixed-type instabilities are studied. Wendelstein 7-X and QIPC exhibit significantly reduced growth rates for all simulations that include kinetic electrons, and the latter are indeed found to be stabilizing in the energy budget. These results suggest that imperfectly optimized stellarators can retain most of the stabilizing properties predicted for perfect maximum-J configurations.

  10. Relativistic soliton-like collisionless ionization wave

    Science.gov (United States)

    Arefiev, Alexey; McCormick, Matthew; Quevedo, Hernan; Bengtson, Roger; Ditmire, Todd

    2014-10-01

    It has been observed in recent experiments with laser-irradiated gas jets that a plasma filament produced by the laser and containing energetic electrons can launch a relativistic ionization wave into ambient gas. Here we present a self-consistent theory that explains how a collisionless ionization wave can propagate in a self-sustaining regime. A population of hot electrons necessarily generates a sheath electric field at the plasma boundary. This field penetrates the ambient gas, ionizing the gas atoms and thus causing the plasma boundary to expand. We show that the motion of the newly generated electrons can form a potential well adjacent to the plasma boundary. The outwards motion of the well causes a bunch of energetic electrons to become trapped, while allowing the newly generated electrons to escape into the plasma without retaining much energy. The resulting soliton-like ionizing field structure propagates outwards with a bunch of hot electrons that maintain a strong sheath field despite significant plasma expansion. We also present 1D and 2D particle-in-cell simulations that illustrate the described mechanism. The simulations were performed using HPC resources provided by the Texas Advanced Computing Center. This work was supported by NNSA Contract No. DE-FC52-08NA28512 and U.S. DOE Contract No. DE-FG02-04ER54742.

  11. Transport theory in the collisionless limit

    International Nuclear Information System (INIS)

    Hazeltine, R.D.

    1998-01-01

    Traditional transport theory provides a closure of fluid equations that is valid in the collisional, short mean-free-path limit. The possibility of extending an analogous closure to long mean-free path is examined here. An appropriate kinetic equation, using a model collision operator, is solved rigorously for arbitrary collisionality but weak, Maxwellian source terms. The corresponding particle and heat flows are then expressed in terms of the density and temperature profiles. The transport matrix is found to be symmetric even at vanishing collision frequency; in the collisionless limit it takes the form of nonlocal operators. The operator corresponding to thermal conductivity agrees with one found previously by Hammett and Perkins. However particle diffusion, which turns out to satisfy a local Fick's law for any finite collision frequency, becomes singular at vanishing collisionality, where the pressure gradient vanishes. We conclude that the fluxes can generally be expressed in terms of particle and energy sources, but not always in terms of pressure and temperature profiles

  12. MMS observation of energy conversion and collisionless plasma dissipation channels in the turbulent magnetosheath

    Science.gov (United States)

    Parashar, T.; Yang, Y.; Chasapis, A.; Matthaeus, W. H.

    2017-12-01

    High resolution Magnetospheric Multiscale (MMS) plasma and magnetic field data obtained in the inhomogeneous turbulent magnetosheath directly reveals the exchanges of energy between electromagnetic, flow and random kinetic energy. The parameters that quantify these exchanges are based on standard manipulations of the collisionless Vlasov model of plasma dynamics [1], without appeal to viscous or other closures. No analysis of heat transport or heat conduction is carried out. Several intervals of burst mode data in the magnetosheath are considered. Time series of the work done by the electromagnetic field, and the pressure-stress interaction enable description of the pathways to dissipation in this low collisionality plasma. Using these examples we demonstrate that the pressure-stress interaction provides important information not readily revealed in other diagnostics concerning the physical processes that are observed. This method does not require any specific mechanism for its application such as reconnection or a selected mode, although with increased experience it will be useful in distinguishing among proposed possibilities. [1] Y. Yang et al, Phys. Plasmas 24, 072306 (2017); doi: 10.1063/1.4990421.

  13. FAST MAGNETIC FIELD AMPLIFICATION IN THE EARLY UNIVERSE: GROWTH OF COLLISIONLESS PLASMA INSTABILITIES IN TURBULENT MEDIA

    Energy Technology Data Exchange (ETDEWEB)

    Falceta-Gonçalves, D. [SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS (United Kingdom); Kowal, G. [Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Rua Arlindo Bettio, 1000, São Paulo, SP 03828-000 (Brazil)

    2015-07-20

    In this work we report on a numerical study of the cosmic magnetic field amplification due to collisionless plasma instabilities. The collisionless magnetohydrodynamic equations derived account for the pressure anisotropy that leads, in specific conditions, to the firehose and mirror instabilities. We study the time evolution of seed fields in turbulence under the influence of such instabilities. An approximate analytical time evolution of the magnetic field is provided. The numerical simulations and the analytical predictions are compared. We found that (i) amplification of the magnetic field was efficient in firehose-unstable turbulent regimes, but not in the mirror-unstable models; (ii) the growth rate of the magnetic energy density is much faster than the turbulent dynamo; and (iii) the efficient amplification occurs at small scales. The analytical prediction for the correlation between the growth timescales and pressure anisotropy is confirmed by the numerical simulations. These results reinforce the idea that pressure anisotropies—driven naturally in a turbulent collisionless medium, e.g., the intergalactic medium, could efficiently amplify the magnetic field in the early universe (post-recombination era), previous to the collapse of the first large-scale gravitational structures. This mechanism, though fast for the small-scale fields (∼kpc scales), is unable to provide relatively strong magnetic fields at large scales. Other mechanisms that were not accounted for here (e.g., collisional turbulence once instabilities are quenched, velocity shear, or gravitationally induced inflows of gas into galaxies and clusters) could operate afterward to build up large-scale coherent field structures in the long time evolution.

  14. Nonlinear simulation of magnetic reconnection with a drift kinetic electron model

    International Nuclear Information System (INIS)

    Zwingmann, W.; Ottaviani, M.

    2004-01-01

    The process of reconnection allows for a change of magnetic topology inside a plasma. It is an important process for eruptive phenomena in astrophysical plasma, and the sawtooth relaxation in laboratory plasma close to thermonuclear conditions. The sawtooth relaxation is associated with the collisionless electron tearing instability, caused by the electron inertia. A thorough treatment therefore requires a kinetic model for the electron dynamics. In this contribution, we report on the numerical simulation of the electron tearing instability by solving the Vlasov equation directly. The results confirm results of an early paper on the same subject, and extends them to smaller values of the collision skin depth d e = 0.25. Our results suggest a faster than exponential growth in the early nonlinear phase of the instability. We observe as well an asymmetry of the resulting fields. It seems, however, that the field structure becomes closer to the fluid case for small values of d e

  15. Model of magnetic reconnection in space and astrophysical plasmas

    International Nuclear Information System (INIS)

    Boozer, Allen H.

    2013-01-01

    Maxwell's equations imply that exponentially smaller non-ideal effects than commonly assumed can give rapid magnetic reconnection in space and astrophysical plasmas. In an ideal evolution, magnetic field lines act as stretchable strings, which can become ever more entangled but cannot be cut. High entanglement makes the lines exponentially sensitive to small non-ideal changes in the magnetic field. The cause is well known in popular culture as the butterfly effect and in the theory of deterministic dynamical systems as a sensitive dependence on initial conditions, but the importance to magnetic reconnection is not generally recognized. Two-coordinate models are too constrained geometrically for the required entanglement, but otherwise the effect is general and can be studied in simple models. A simple model is introduced, which is periodic in the x and y Cartesian coordinates and bounded by perfectly conducting planes in z. Starting from a constant magnetic field in the z direction, reconnection is driven by a spatially smooth, bounded force. The model is complete and could be used to study the impulsive transfer of energy between the magnetic field and the ions and electrons using a kinetic plasma model.

  16. Three-dimensional Oscillatory Magnetic Reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Thurgood, Jonathan O.; McLaughlin, James A. [Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle upon Tyne, NE1 1ST (United Kingdom); Pontin, David I., E-mail: jonathan.thurgood@northumbria.ac.uk [Division of Mathematics, University of Dundee, Dundee, DD1 4HN (United Kingdom)

    2017-07-20

    Here we detail the dynamic evolution of localized reconnection regions about 3D magnetic null points using numerical simulation. We demonstrate for the first time that reconnection triggered by the localized collapse of a 3D null point that is due to an external magnetohydrodynamic (MHD) wave involves a self-generated oscillation, whereby the current sheet and outflow jets undergo a reconnection reversal process during which back-pressure formation at the jet heads acts to prise open the collapsed field before overshooting the equilibrium into an opposite-polarity configuration. The discovery that reconnection at fully 3D nulls can proceed naturally in a time-dependent and periodic fashion suggests that oscillatory reconnection mechanisms may play a role in explaining periodicity in astrophysical phenomena associated with magnetic reconnection, such as the observed quasi-periodicity of solar and stellar flare emission. Furthermore, we find that a consequence of oscillatory reconnection is the generation of a plethora of freely propagating MHD waves that escape the vicinity of the reconnection region.

  17. From vortex reconnections to quantum turbulence

    International Nuclear Information System (INIS)

    Lipniacki, T.

    2001-01-01

    An alternative approach to quantum turbulence is proposed in order to derive the evolution equation for vortex line-length density. Special attention is paid to reconnections of vortex lines. The summed line-length change ΔS of two vortex lines resulting from the reconnection (in the presence of counterflow V ns ) can be approximated in the form: δS=-at 1/2 +bV ns 2 t 3/2 , with a>0, b≥0, at least until δS≤0. For steady-state turbulence, the average line-length change left angle ΔS right angle between reconnections has to be zero. If, for a given value of the counterflow, the line density is smaller than the equilibrium one, the reconnections occur less frequently and left angle ΔS right angle becomes positive and the line density grows until the equilibrium is restored. When the line-density is too large, the reconnections are more frequent, the lines shorten between reconnections and the line density gets smaller. The time derivative of the total line density is proportional to the reconnection frequency multiplied by the average line-length change due to a single reconnection. The evolution equation obtained in the proposed approach resembles the alternative Vinen equation. (orig.)

  18. High-power laser experiments to study collisionless shock generation

    Directory of Open Access Journals (Sweden)

    Sakawa Y.

    2013-11-01

    Full Text Available A collisionless Weibel-instability mediated shock in a self-generated magnetic field is studied using two-dimensional particle-in-cell simulation [Kato and Takabe, Astophys. J. Lett. 681, L93 (2008]. It is predicted that the generation of the Weibel shock requires to use NIF-class high-power laser system. Collisionless electrostatic shocks are produced in counter-streaming plasmas using Gekko XII laser system [Kuramitsu et al., Phys. Rev. Lett. 106, 175002 (2011]. A NIF facility time proposal is approved to study the formation of the collisionless Weibel shock. OMEGA and OMEGA EP experiments have been started to study the plasma conditions of counter-streaming plasmas required for the NIF experiment using Thomson scattering and to develop proton radiography diagnostics.

  19. Collisionless emission of radiation by an inhomogeneous plasma

    International Nuclear Information System (INIS)

    Mejerovich, B.Eh.

    1976-01-01

    Collisionless emission of radiation by an inhomogeneous plasma due to the finite motion of charges in the field of external forces and collective interaction forces is studied. The intensity of the radiation is inversely proportional to the square of the transverse dimensions of the plasma. It apparently makes the main contribution to the radiation from a vacuum spark and other relativitstic beams compressed to a small size by collective interaction forces. The intensity of the collisionless radiation is calculated by taking into account Fermi statistics of the electrons. The spectral radiance in the low frequency range increases with frequency, reaches a maximum at the frequency of the finite motion of the emitters and then decreases. Measurement of collisionless radiation emission by a plasma compressed to a small size by the pinch effect is a natural way of diagnosing the plasma

  20. Collisionless Weibel shocks: Full formation mechanism and timing

    Energy Technology Data Exchange (ETDEWEB)

    Bret, A. [ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain); Instituto de Investigaciones Energéticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real (Spain); Stockem, A. [GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon (Portugal); Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Narayan, R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51 Cambridge, Massachusetts 02138 (United States); Silva, L. O. [GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon (Portugal)

    2014-07-15

    Collisionless shocks in plasmas play an important role in space physics (Earth's bow shock) and astrophysics (supernova remnants, relativistic jets, gamma-ray bursts, high energy cosmic rays). While the formation of a fluid shock through the steepening of a large amplitude sound wave has been understood for long, there is currently no detailed picture of the mechanism responsible for the formation of a collisionless shock. We unravel the physical mechanism at work and show that an electromagnetic Weibel shock always forms when two relativistic collisionless, initially unmagnetized, plasma shells encounter. The predicted shock formation time is in good agreement with 2D and 3D particle-in-cell simulations of counterstreaming pair plasmas. By predicting the shock formation time, experimental setups aiming at producing such shocks can be optimised to favourable conditions.

  1. Collisionless kinetic-fluid model of zonal flows in toroidal plasmas

    International Nuclear Information System (INIS)

    Sugama, H.; Watanabe, T.-H.; Horton, W.

    2006-12-01

    A novel kinetic-fluid model is presented, which describes collisionless time evolution of zonal flows in tokamaks. In the new zonal-flow closure relations, the parallel heat fluxes are written by the sum of short- and long-time-evolution parts. The former part is given in the dissipative form of the parallel heat diffusion and relates to collisionless damping processes. The latter is derived from the long-time-averaged gyrocenter distribution and plays a major role in describing low-frequency or stationary zonal flows, for which the parallel heat fluxes are expressed in terms of the parallel flow as well as the nonlinear-source and initial-condition terms. It is shown analytically and numerically that, when applied to the zonal flow driven by either ion or electron temperature gradient turbulence, the kinetic-fluid equations including the new closure relations can reproduce the same long-time zonal-flow responses to the initial condition and to the turbulence source as those obtained from the gyrokinetic model. (author)

  2. Relativistic reconnection in near critical Schwinger field

    Science.gov (United States)

    Schoeffler, Kevin; Grismayer, Thomas; Fonseca, Ricardo; Silva, Luis; Uzdensky, Dmitri

    2017-10-01

    Magnetic reconnection in relativistic pair plasma with QED radiation and pair-creation effects in the presence of strong magnetic fields is investigated using 2D particle-in-cell simulations. The simulations are performed with the QED module of the OSIRIS framework that includes photon emission by electrons and positrons and single photon decay into pairs (non-linear Breit-Wheeler). We investigate the effectiveness of reconnection as a pair- and gamma-ray production mechanism across a broad range of reconnecting magnetic fields, including those approaching the critical quantum (Schwinger) field, and we also explore how the radiative cooling and pair-production processes affect reconnection. We find that in the extreme field regime, the magnetic energy is mostly converted into radiation rather than into particle kinetic energy. This study is a first concrete step towards better understanding of magnetic reconnection as a possible mechanism powering gamma-ray flares in magnetar magnetospheres.

  3. Recent Progress in Understanding Solar Magnetic Reconnection

    Directory of Open Access Journals (Sweden)

    Jeongwoo Lee

    2015-06-01

    Full Text Available Magnetic reconnection is a fundamental process occurring in a wide range of astrophysical, heliospheric and laboratory plasmas. This process alters magnetic topology and triggers rapid conversion of magnetic energy into thermal heating and nonthermal particle acceleration. Efforts to understand the physics of magnetic reconnection have been made across multiple disciplines using remote observations of solar flares and in-situ measurements of geomagnetic storms and substorms as well as laboratory and numerical experiments. This review focuses on the progress achieved with solar flare observations in which most reconnection-related signatures could be resolved in both space and time. The emphasis is on various observable emission features in the low solar atmosphere which manifest the coronal magnetic reconnection because these two regions are magnetically connected to each other. The research and application perspectives of solar magnetic reconnection are briefly discussed and compared with those in other plasma environments.

  4. Interplay between electric fields generated by reconnection and by secondary processes

    Science.gov (United States)

    Lapenta, G.; Innocenti, M. E.; Pucci, F.; Cazzola, E.; Berchem, J.; Newman, D. L.; El-Alaoui, M.; Walker, R. J.; Goldman, M. V.; Ergun, R.

    2017-12-01

    Reconnection regions are surrounded by several sources of free energy that push reconnection towards a turbulent regime: beams can drive streaming instabilities, currents can drive tearing like secondary instabilities, velocity and density shears can drive Kelvin-Helmholtz or Rayleigh-Taylor type of instabilities. The interaction between these instabilities can be very complex. For instance, from a kinetic point of view, instabilities resulting from shears are intermixed with drift-type instabilities, such as drift-kink, kink driven by relative species drift, lower hybrid modes of the electrostatic or electromagnetic type. In addition, the interaction with reconnection is two ways: reconnection causes the conditions for those instabilities to develop while the instabilities alter the progress of reconnection. Although MMS has observed features that can be associated with such instabilities: strong localized parallel electric fields (monopolar and bipolar), fluctuations in the drift range (lower hybrid, whistler), it has been difficult to determine which ones operate and how they differ depending on the symmetric and asymmetric reconnection configurations observed in the magnetotail and at the magnetopause, respectively. We present a comparison between the results of kinetic simulations obtained for typical magnetotail and the magnetopause configurations, using for each of them both analytical equilibria and results of global MHD simulations to initialize the iPIC3D simulations. By selecting what drivers (e.g. shear/no shear) are present, we can identify what instabilities develop and determine their effects on the progression of reconnection in the magnetotail and at the magnetopause. We focus especially on the role of drift waves and whistler instabilities, and discuss our results by comparing them with MMS observations.

  5. Evidence for Secondary Flux Rope Generated by the Electron Kelvin-Helmholtz Instability in a Magnetic Reconnection Diffusion Region.

    Science.gov (United States)

    Zhong, Z H; Tang, R X; Zhou, M; Deng, X H; Pang, Y; Paterson, W R; Giles, B L; Burch, J L; Tobert, R B; Ergun, R E; Khotyaintsev, Y V; Lindquist, P-A

    2018-02-16

    Secondary flux ropes are suggested to play important roles in energy dissipation and particle acceleration during magnetic reconnection. However, their generation mechanism is not fully understood. In this Letter, we present the first direct evidence that a secondary flux rope was generated due to the evolution of an electron vortex, which was driven by the electron Kelvin-Helmholtz instability in an ion diffusion region as observed by the Magnetospheric Multiscale mission. The subion scale (less than the ion inertial length) flux rope was embedded within the electron vortex, which contained a secondary electron diffusion region at the trailing edge of the flux rope. We propose that intense electron shear flow produced by reconnection generated the electron Kelvin-Helmholtz vortex, which induced a secondary reconnection in the exhaust of the primary X line and then led to the formation of the flux rope. This result strongly suggests that secondary electron Kelvin-Helmholtz instability is important for reconnection dynamics.

  6. Influence of Initial Vorticity Distribution on Axisymmetric Vortex Breakdown and Reconnection

    Science.gov (United States)

    Young, Larry A.

    2007-01-01

    An analytical treatment has been developed to study some of the axisymmetric vortex breakdown and reconnection fluid dynamic processes underlying body-vortex interactions that are frequently manifested in rotorcraft and propeller-driven fixed-wing aircraft wakes. In particular, the presence of negative vorticity in the inner core of a vortex filament (one example of which is examined in this paper) subsequent to "cutting" by a solid body has a profound influence on the vortex reconnection, leading to analog flow behavior similar to vortex breakdown phenomena described in the literature. Initial vorticity distributions (three specific examples which are examined) without an inner core of negative vorticity do not exhibit vortex breakdown and instead manifest diffusion-like properties while undergoing vortex reconnection. Though this work focuses on laminar vortical flow, this work is anticipated to provide valuable insight into rotary-wing aerodynamics as well as other types of vortical flow phenomena.

  7. Physics of Reconnection and MMS Mission

    Science.gov (United States)

    Kuznetsova, M. M.; Hesse, M.; Gombosi, T.

    2009-01-01

    Reconnection is the most important process driving the Earth's magnetosphere. Key to the success of the MMS science plan is the coupling of theory and observation. Determining the kinetic processes occurring in the diffusion region and physical parameters that control the rate of magnetic reconnection are among primary objectives of the MMS mission. Analysis of the role played by particle inertial effects in the diffusion region where the plasma is unmagnetized will be presented. The reconnection electric field in he diffusion region is supported primarily by particle non-gyrotropic effects. At the quasi-steady stage the reconnection electric field serves to accelerate and heat the incoming plasma population to maintain the current flow in the diffusion region the pressure balance. The primary mechanism controlling the dissipation in the vicinity of the reconnection site is incorporated into the fluid description in terms of non-gyrotropic corrections to the. induction and energy equations. The results of kinetic and fluid simulations illustrating the physics of magnetic reconnection will be presented. We will dem:tistrate that kinetic nongyrotropic effects can significantly alter the global magnetosphere evolution and location of reconnection sites.

  8. Magnetic Reconnection in the Solar Chromosphere

    Science.gov (United States)

    Lukin, Vyacheslav S.; Ni, Lei; Murphy, Nicholas Arnold

    2017-08-01

    We report on the most recent efforts to accurately and self-consistently model magnetic reconnection processes in the context of the solar chromosphere. The solar chromosphere is a notoriously complex and highly dynamic boundary layer of the solar atmosphere where local variations in the plasma parameters can be of the order of the mean values. At the same time, the interdependence of the physical processes such as magnetic field evolution, local and global energy transfer between internal and electromagnetic plasma energy, radiation transport, plasma reactivity, and dissipation mechanisms make it a particularly difficult system to self-consistently model and understand. Several recent studies have focused on the micro-physics of multi-fluid magnetic reconnection at magnetic nulls in the weakly ionized plasma environment of the lower chromosphere[1-3]. Here, we extend the previous work by considering a range of spatial scales and magnetic field strengths in a configuration with component magnetic reconnection, i.e., for magnetic reconnection with a guide field. We show that in all cases the non-equilibrium reactivity of the plasma and the dynamic interaction among the plasma processes play important roles in determining the structure of the reconnection region. We also speculate as to the possible observables of chromospheric magnetic reconnection and the likely plasma conditions required for generation of Ellerman and IRIS bombs.[1] Leake, Lukin, Linton, and Meier, “Multi-fluid simulations of chromospheric magnetic reconnection in a weakly ionized reacting plasma,” ApJ 760 (2012).[2] Leake, Lukin, and Linton, “Magnetic reconnection in a weakly ionized plasma,” PoP 20 (2013).[3] Murphy and Lukin, “Asymmetric magnetic reconnection in weakly ionized chromospheric plasmas,” ApJ 805 (2015).[*Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National

  9. The Memory of the Magnetic Reconnection Location

    Science.gov (United States)

    Trattner, K. J.; Petrinec, S. M.; Fuselier, S. A.

    2008-05-01

    The location of the reconnection line in relation to regions where accelerated plasma flows have been reported with local magnetic shear angles greater than 50° greatly influences the mass and energy transfer from the solar wind to the magnetosphere. The highest transfer rates are achieved for conditions where the merging fields are anti-parallel. Recent studies concerning the location of the reconnection line with single point measurements under stable solar wind and IMF conditions reveal that the so-called tilted X-line, crossing the dayside sub-solar region, is the dominant reconnection scenario. Magnetic reconnection tends to occur along a continuous X-line of maximum magnetic shear across the dayside magnetopause. Exceptions to this reconnection location are dominant southward IMF conditions (within ±25° of southward IMF) or a dominant IMF Bx component (more than 70% of the IMF in the Bx component) for which the reconnection line bifurcates, and exists along magnetopause regions where the merging fields are exactly anti-parallel. In this presentation we will discuss specific exceptions and differences to the statistical reconnection location model determined from times of stable and unchanged IMF conditions. These differences are most probably caused by the dynamic nature of the IMF direction. Reconnection locations during slow changing IMF clock angles show a certain reluctance to adjust to the new conditions of the changing field and show locations of earlier IMF conditions. An additional puzzling feature is the occurrence of reconnection location anomalies around an IMF clock angle of about 230°.

  10. Some dynamical properties of anisotropic collisionless stellar systems

    International Nuclear Information System (INIS)

    Bertin, G.; Pegoraro, F.

    1989-01-01

    The linear stability analysis of collisionless anisotropic spherical stellar systems presents many unresolved issues. Planning to study the stability of a simple and astrophysically interesting equilibrium seuence ∞ for such stellar systems, we describe here some analytical characterizations of the ∞-distribution functions, formulate the linearized equations for stability, and discuss the relevant boundary conditions. (author). 19 refs.; 1 tab

  11. Collisionless shocks and upstream waves and particles: Introductory remarks

    International Nuclear Information System (INIS)

    Kennel, C.F.

    1981-01-01

    We discuss more aspects of collisionless shock theory that might be pertinent to the problem of upstream waves and particles. It is hoped that our qualititive remarks may be a useful guide for the general reader as he goes through the detailed papers to come

  12. Experimental onset threshold and magnetic pressure pileup for 3D Sweet-Parker reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Intrator, Thomas P [Los Alamos National Laboratory; Sun, Xuan [Los Alamos National Laboratory; Lapenta, Giovanni [Los Alamos National Laboratory; Furno, Ivo [Los Alamos National Laboratory; [NON LANL

    2008-01-01

    In space, astrophysical and laboratory plasmas, magnetic reconnect ion converts magnetic into particle energy during unsteady, explosive events. The abrupt onset and cessation has been a long standing puzzle. We show the first three-dimensional (3D) laboratory example of onset and stagnation of Sweet-Parker type magnetic reconnection between magnetized and parallel current (flux) ropes driven by magnetohydrodynamic (MHD) attraction and 3D instability. Mutually attracting flux ropes advect and merge oppositely directed magnetic fields. Magnetic flux is annihilated, but reaches soon a threshold where magnetic flux and pressure pile up, and reconnection magnetic topology appears. This occurs when inflow speeds exceed the SweetParker speed v{sub SP} = v{sub A} / S{sup 1/2}, where v{sub A} is the Alfven speed and S is the Lundquist number for the reconnection layer, as magnetic flux arrives faster than flux annihilation can process it. Finally piled up fields generate MHD reaction forces that stall the inflow and the reconnection process.

  13. Tripolar electric field Structure in guide field magnetic reconnection

    OpenAIRE

    S. Fu; S. Huang; M. Zhou; B. Ni; X. Deng

    2018-01-01

    It has been shown that the guide field substantially modifies the structure of the reconnection layer. For instance, the Hall magnetic and electric fields are distorted in guide field reconnection compared to reconnection without guide fields (i.e., anti-parallel reconnection). In this paper, we performed 2.5-D electromagnetic full particle simulation to study the electric field structures in magnetic reconnection under different initial guide fields (Bg). Once the amplit...

  14. The Role of Geometry in Magnetic Reconnection

    Science.gov (United States)

    Hesse, Michael; Aunai, Nicholas; Birn, Joachim; Zenitani, Seiji

    2012-01-01

    Magnetic reconnection is arguably the most effective energy conversion and transport process in plasmas. Reconnection is subject to topological considerations in two ways. First, the process itself involves a change in topology of the combined plasma-magnetic field system. This change in topology transcends that of the magnetic field alone and accounts for flux transport relative to the motion of the plasma in the system under investigation. The second way topology is important to magnetic reconnection is through modifications of the diffUSion/dissipation physics brought about by the structure of the reconnecting system. This presentation will present an overview and summary of both past and recent results pertaining to both aspects.

  15. Comparison between Magnetopause and Magnetotail Reconnection Processes

    Science.gov (United States)

    Walker, R. J.; Lapenta, G.; Berchem, J.; El-Alaoui, M.

    2017-12-01

    For the past two years the Magnetosphere Multiscale (MMS) mission has returned detailed observations of reconnection at Earth's dayside magnetopause and now apogee has moved into the magnetotail to enable investigations of reconnection in the plasma sheet. We have been using a combination of global magnetohydrodynamic (MHD) simulation and particle-in-cell (PIC) simulation to model the physics of the reconnection process in both regions. In these calculations, we first use the MHD simulation to model the overall magnetospheric configuration and then carry out a large implicit PIC simulation by using the resulting MHD state to set the initial and boundary conditions. In this presentation, we review the similarities and differences found between the physical processes involved in reconnection occurring in the two different regions. For instance, similar crescent shaped distribution functions have been both observed and found in simulations of reconnection at the magnetopause and in the tail current sheet. Likewise, kinetic simulations have shown that the agyrotropy (non-gyrotropy) of the electron distribution function is the cleanest indicator of the location of the electron diffusion region (EDR) of both regions. There are also significant differences between the two regions. These are mostly related to the fact that separatrices are different because the plasma density is asymmetric across the dayside magnetopause and that smaller electric and guide fields are present in the night side. For instance, the jetting plasmas from reconnection in the tail form dipolarization fronts where energy exchange occurs while flux transfer events (flux ropes) form on the magnetopause and then move away from the reconnection site without forming dipolarization fronts. However, many uncertainties remain. For example, strong waves associated with the reconnection are found in the EDR at both places but it is not understood whether the kinetic mechanisms leading to the waves are the

  16. Experimental results of astrophysical collisionless shock experiments from NIF

    Science.gov (United States)

    Park, Hye-Sook; Higginson, D.; Huntington, C.; Pollock, B.; Remington, B.; Rinderknecht, H.; Ross, J.; Ryutov, D.; Swadling, G.; Wilks, S.; Fiuza, F.; Sakawa, Y.; Spitkovsky, A.; Petrasso, R.; Li, C.; Zylstra, A.; Lamb, D.; Tzeferacos, P.; Gregori, G.; Meinecke, J.; Manuel, M.

    2017-10-01

    We discuss our laboratory experiments using the Omega and NIF lasers to investigate the dynamics of high Mach number collisionless shock formation in two interpenetrating plasma streams. It is believed that in astrophysical environments such shocks are the sites where seed magnetic fields are generated on a cosmologically fast timescale via the Weibel instability. Particle-in-cell (PIC) numerical simulations generate magnetic fields whose magnitude and scale are consistent with this concept. We will present recent experimental results as well as simulations and theoretical interpretations of these observations. The NIF experiments were able to observe the counter-streaming flow interactions through the transition from collisional to collisionless regimes. The latest proton radiography results will be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  17. Transport of parallel momentum by collisionless drift wave turbulence

    DEFF Research Database (Denmark)

    Diamond, P.H.; McDevitt, C.J.; Gurcan, O.E.

    2008-01-01

    This paper presents a novel, unified approach to the theory of turbulent transport of parallel momentum by collisionless drift waves. The physics of resonant and non‐resonant off‐diagonal contributions to the momentum flux is emphasized, and collisionless momentum exchange between waves...... and particles is accounted for. Two related momentum conservation theorems are derived. These relate the resonant particle momentum flux, the wave momentum flux and the refractive force. A perturbative calculation, in the spirit of Chapman‐Enskog theory, is used to obtain the wave momentum flux, which...... contributes significantly to the residual stress. A general equation for mean κ∥(〈κ∥〉) is derived and used to develop a generalized theory of symmetry breaking. The resonant particle momentum flux is calculated, and pinch and residual stress effects are identified. The implications of the theory for intrinsic...

  18. Transport of parallel momentum by collisionless drift wave turbulence

    DEFF Research Database (Denmark)

    Diamond, P.H.; McDevitt, C.J.; Gürcan, O.D.

    2008-01-01

    This paper presents a novel, unified approach to the theory of turbulent transport of parallel momentum by collisionless drift waves. The physics of resonant and nonresonant off-diagonal contributions to the momentum flux is emphasized, and collisionless momentum exchange between waves...... and particles is accounted for. Two related momentum conservation theorems are derived. These relate the resonant particle momentum flux, the wave momentum flux, and the refractive force. A perturbative calculation, in the spirit of Chapman-Enskog theory, is used to obtain the wave momentum flux, which...... contributes significantly to the residual stress. A general equation for mean k(parallel to) () is derived and used to develop a generalized theory of symmetry breaking. The resonant particle momentum flux is calculated, and pinch and residual stress effects are identified. The implications...

  19. Numerical simulations of energy transfer in two collisionless interpenetrating plasmas

    Directory of Open Access Journals (Sweden)

    Davis S.

    2013-11-01

    Full Text Available Ion stream instabilities are essential for collisionless shock formation as seen in astrophysics. Weakly relativistic shocks are considered as candidates for sources of high energy cosmic rays. Laboratory experiments may provide a better understanding of this phenomenon. High intensity short pulse laser systems are opening possibilities for efficient ion acceleration to high energies. Their collision with a secondary target could be used for collisionless shock formation. In this paper, using particle-in-cell simulations we are studying interaction of a sub-relativistic, laser created proton beam with a secondary gas target. We show that the ion bunch initiates strong electron heating accompanied by the Weibel-like filamentation and ion energy losses. The energy repartition between ions, electrons and magnetic fields are investigated. This yields insight on the processes occurring in the interstellar medium (ISM and gamma-ray burst afterglows.

  20. Renormalized Compton scattering and nonlinear damping of collisionless drift waves

    International Nuclear Information System (INIS)

    Krommes, J.A.

    1979-05-01

    A kinetic theory for the nonlinear damping of collisionless drift waves in a shear-free magnetic field is presented. The general formalism is a renormalized version of induced scattering on the ions and reduces correctly to weak turbulence theory. The approximation studied explicitly reduces to Compton scattering, systematizes thee earlier calculations of Dupree and Tetreault (DT) [Phys. Fluids 21, 425 (1978)], and extends that theory to finite ion gyroradius. Certain conclusions differ significantly from those of DT

  1. Description of collisionless plasmas by classical field equations

    International Nuclear Information System (INIS)

    Fraley, G.S.

    1975-10-01

    Classical field equations are derived from quantum fields to obtain a different and possibly simpler description of a collisionless plasma. The method is to take the simultaneous limit, Dirac constant, e, m → 0, of charged scalar fields and the electromagnetic field. Laplace transforms for perturbations in a uniform relativistic plasma are compared with corresponding results from the Maxwell--Vlasov equations. For the nonlinear case, a distribution function defined on the classical fields is shown to satisfy the Vlasov equation

  2. Plasma confinement in self-consistent, one-dimensional transport equilibria in the collisionless-ion regime of EBT operation

    International Nuclear Information System (INIS)

    Chang, C.S.; Miller, R.L.

    1983-01-01

    It has long been recognized that if an EBT-confined plasma could be maintained in the collisionless-ion regime, characterized by positive ambipolar potential and positive radial electric field, the particle loss rates could be reduced by a large factor. The extent to which the loss rate of energy could be reduced has not been as clearly determined, and has been investigated recently using a one-dimensional, time-dependent transport code developed for this purpose. We find that the energy confinement can be improved by roughly an order of magnitude by maintaining a positive radial electric field that increases monotonically with radius, giving a large ExB drift near the outer edge of the core plasma. The radial profiles of heat deposition required to sustain these equilibria will be presented, and scenarios for obtaining dynamical access to the equilibria will be discussed

  3. Fast reconnection of weak magnetic fields

    International Nuclear Information System (INIS)

    Zweibel, E.G.

    1998-01-01

    Fast magnetic reconnection refers to annihilation or topological rearrangement of magnetic fields on a timescale that is independent (or nearly independent) of the plasma resistivity. The resistivity of astrophysical plasmas is so low that reconnection is of little practical interest unless it is fast. Yet, the theory of fast magnetic reconnection is on uncertain ground, as models must avoid the tendency of magnetic fields to pile up at the reconnection layer, slowing down the flow. In this paper it is shown that these problems can be avoided to some extent if the flow is three dimensional. On the other hand, it is shown that in the limited but important case of incompressible stagnation point flows, every flow will amplify most magnetic fields. Although examples of fast magnetic reconnection abound, a weak, disordered magnetic field embedded in stagnation point flow will in general be amplified, and should eventually modify the flow. These results support recent arguments against the operation of turbulent resistivity in highly conducting fluids. copyright 1998 American Institute of Physics

  4. Simulation study of MHD relaxation and reconnection processes in RFP plasma

    International Nuclear Information System (INIS)

    Kusano, Kanya; Kunimoto, Kaito; Suzuki, Yoshio; Tamano, Teruo; Sato, Tetsuya

    1991-01-01

    The authors have studied several nonlinear processes in RFP plasma through the use of 3D MHD simulations. In particular, they have shed light on: (1) dynamo and self-sustainment in reversed-field pinch (RFP), (2) phase locking process in MHD relaxation, and (3) the heating and acceleration in magnetic reconnection process. First, the contributions of the kink (m = 1) mode (linearly unstable) and of the m = 0 mode (driven by nonlinear coupling) to the dynamo are qualitatively evaluated using a high accuracy simulation. It is found that, if the free energy to drive kink instabilities is as small as that in the actual experimental plasma, the m = 0 modes, driven nonlinearly, play a more important role for the flux generation than the kink modes. Secondly, numerical simulations of the self-sustainment process in a RFP are performed. It is confirmed that the self-sustainment process is a coherent oscillating process composed of the MHD relaxation and the resistive diffusion processes. Toroidal phase locking process of kink modes is numerically observed in simulations of self-reversal and self-sustainment processes. It has characteristics similar to the slinky mode observed in the OHTE experiment. A detailed investigation reveals that nonlinear coupling between the most unstable two kink modes governs the entire dynamics in all kink modes and leads to the phase locking process. They find that reconnection can accelerate plasma over a local Alfven speed. This is a result of the fact that the magnetic field in the downstream area plays a similar role to de Laval nozzle. They also investigate the heating mechanisms in reconnection process. It is revealed that the viscous heating rate is as large as the joule heating rate in the reconnection process. This result implies that the viscous heating in the reconnection process is an important candidate for the mechanism to explain the RFP experiments where the ion temperatures is higher than the electron temperature

  5. Modeling the Self-organized Critical Behavior of the Plasma Sheet Reconnection Dynamics

    Science.gov (United States)

    Klimas, Alex; Uritsky, Vadim; Baker, Daniel

    2006-01-01

    Analyses of Polar UVI auroral image data reviewed in our other presentation at this meeting (V. Uritsky, A. Klimas) show that bright night-side high-latitude UV emissions exhibit so many of the key properties of systems in self-organized criticality (SOC) that an alternate interpretation has become virtually impossible. It is now necessary to find and model the source of this behavior. We note that the most common models of self-organized criticality are numerical sandpiles. These are, at root, models that govern the transport of some quantity from a region where it is loaded to another where it is unloaded. Transport is enabled by the excitation of a local threshold instability; it is intermittent and bursty, and it exhibits a number of scale-free statistical properties. Searching for a system in the magnetosphere that is analogous and that, in addition, is known to produce auroral signatures, we focus on the reconnection dynamics of the plasma sheet. In our previous work, a driven reconnection model has been constructed and has been under study. The transport of electromagnetic (primarily magnetic) energy carried by the Poynting flux into the reconnection region of the model has been examined. All of the analysis techniques, and more, that have been applied to the auroral image data have also been applied to this Poynting flux. Here, we report new results showing that this model also exhibits so many of the key properties of systems in self-organized criticality that an alternate interpretation is implausible. Further, we find a strong correlation between these key properties of the model and those of the auroral UV emissions. We suggest that, in general, the driven reconnection model is an important step toward a realistic plasma physical model of self-organized criticality and we conclude, more specifically, that it is also a step in the right direction toward modeling the multiscale reconnection dynamics of the magnetotail.

  6. Modeling the Self-organized Critical Behavior of Earth's Plasma Sheet Reconnection Dynamics

    Science.gov (United States)

    Klimas, Alexander J.

    2006-01-01

    Analyses of Polar UVI auroral image data show that bright night-side high-latitude W emissions exhibit so many of the key properties of systems in self-organized criticality that an alternate interpretation has become virtually impossible. These analyses will be reviewed. It is now necessary to find and model the source of this behavior. We note that the most common models of self-organized criticality are numerical sandpiles. These are, at root, models that govern the transport of some quantity from a region where it is loaded to another where it is unloaded. Transport is enabled by the excitation of a local threshold instability; it is intermittent and bursty, and it exhibits a number of scale-free statistical properties. Searching for a system in the magnetosphere that is analogous and that, in addition, is known to produce auroral signatures, we focus on the reconnection dynamics of the magnetotail plasma sheet. In our previous work, a driven reconnection model has been constructed and has been under study. The transport of electromagnetic (primarily magnetic) energy carried by the Poynting flux into the reconnection region of the model has been examined. All of the analysis techniques (and more) that have been applied to the auroral image data have also been applied to this Poynting flux. New results will be presented showing that this model also exhibits so many of the key properties of systems in self-organized criticality that an alternate interpretation is implausible. A strong correlation between these key properties of the model and those of the auroral UV emissions will be demonstrated. We suggest that, in general, the driven reconnection model is an important step toward a realistic plasma physical model of self-organized criticality and we conclude, more specifically, that it is also a step in the right direction toward modeling the multiscale reconnection dynamics of the magnetotail.

  7. Estimates of magnetotail reconnection rate based on IMAGE FUV and EISCAT measurements

    Directory of Open Access Journals (Sweden)

    N. Østgaard

    2005-01-01

    Full Text Available Dayside merging between the interplanetary and terrestrial magnetic fields couples the solar wind electric field to the Earth's magnetosphere, increases the magnetospheric convection and results in efficient transport of solar wind energy into the magnetosphere. Subsequent reconnection of the lobe magnetic field in the magnetotail transports energy into the closed magnetic field region. Combining global imaging and ground-based radar measurements, we estimate the reconnection rate in the magnetotail during two days of an EISCAT campaign in November-December 2000. Global images from the IMAGE FUV system guide us to identify ionospheric signatures of the open-closed field line boundary observed by the two EISCAT radars in Tromsø (VHF and on Svalbard (ESR. Continuous radar and optical monitoring of the open-closed field line boundary is used to determine the location, orientation and velocity of the open-closed boundary and the ion flow velocity perpendicular to this boundary. The magnetotail reconnection electric field is found to be a bursty process that oscillates between 0mV/m and 1mV/m with ~10-15min periods. These ULF oscillations are mainly due to the motion of the open-closed boundary. In situ measurements earthward of the reconnection site in the magnetotail by Geotail show similar oscillations in the duskward electric field. We also find that bursts of increased magnetotail reconnection do not necessarily have any associated auroral signatures. Finally, we find that the reconnection rate correlates poorly with the solar wind electric field. This indicates that the magnetotail reconnection is not directly driven, but is an internal magnetospheric process. Estimates of a coupling efficiency between the solar wind electric field and magnetotail reconnection only seem to be relevant as averages over long time intervals. The oscillation mode at 1mHz corresponds to the internal cavity mode with additional lower frequencies, 0.5 and 0.8m

  8. James Clerk Maxwell Prize for Plasma Physics: The Physics of Magnetic Reconnection and Associated Particle Acceleration

    Science.gov (United States)

    Drake, James

    2010-11-01

    Solar and stellar flares, substorms in the Earth's magnetosphere, and disruptions in laboratory fusion experiments are driven by the explosive release of magnetic energy through the process of magnetic reconnection. During reconnection oppositely directed magnetic fields break and cross-connect. The resulting magnetic slingshots convert magnetic energy into high velocity flows, thermal energy and energetic particles. A major scientific challenge has been the multi-scale nature of the problem: a narrow boundary layer, ``the dissipation region,'' breaks field lines and controls the release of energy in a macroscale system. Significant progress has been made on fundamental questions such as how magnetic energy is released so quickly and why the release occurs as an explosion. At the small spatial scales of the dissipation region the motion of electrons and ions decouples, the MHD description breaks down and whistler and kinetic Alfven dynamics drives reconnection. The dispersive property of these waves leads to fast reconnection, insensitive to system size and weakly dependent on dissipation, consistent with observations. The evidence for these waves during reconnection in the magnetosphere and the laboratory is compelling. The role of turbulence within the dissipation region in the form of ``secondary islands'' or as a source of anomalous resistivity continues to be explored. A large fraction of the magnetic energy released during reconnection appears in the form of energetic electrons and protons -- up to 50% or more during solar flares. The mechanism for energetic particle production during magnetic reconnection has remained a mystery. Models based on reconnection at a single large x-line are incapable of producing the large numbers of energetic electrons seen in observations. Scenarios based on particle acceleration in a multi-x-line environment are more promising. In such models a link between the energy gain of electrons and the magnetic energy released, a

  9. Localized reconnection in the near jovian magnetotail

    Science.gov (United States)

    Russell; Khurana; Huddleston; Kivelson

    1998-05-15

    The oppositely directed magnetic field in the jovian magnetic tail is expected eventually to reconnect across the current sheet, allowing plasma produced deep inside the magnetosphere near Io's orbit to escape in the antisolar direction down the tail. The Galileo spacecraft found localized regions of strong northward and southward field components beyond about 50 jovian radii in the postmidnight, predawn sector of the jovian magnetosphere. These pockets of vertical magnetic fields can be stronger than the surrounding magnetotail and magnetodisk fields. They may result from episodic reconnection of patches of the near jovian magnetotail.

  10. Frozen flux violation, electron demagnetization and magnetic reconnection

    Science.gov (United States)

    Scudder, J. D.; Karimabadi, H.; Daughton, W.; Roytershteyn, V.

    2015-10-01

    We argue that the analogue in collisionless plasma of the collisional diffusion region of magnetic reconnection is properly defined in terms of the demagnetization of the plasma electrons that enable "frozen flux" slippage to occur. This condition differs from the violation of the "frozen-in" condition, which only implies that two fluid effects are involved, rather than the necessary slippage of magnetic flux as viewed in the electron frame. Using 2D Particle In Cell (PIC) simulations, this approach properly finds the saddle point region of the flux function. Our demagnetization conditions are the dimensionless guiding center approximation expansion parameters for electrons which we show are observable and determined locally by the ratio of non-ideal electric to magnetic field strengths. Proxies for frozen flux slippage are developed that (a) are measurable on a single spacecraft, (b) are dimensionless with theoretically justified threshold values of significance, and (c) are shown in 2D simulations to recover distinctions theoretically possible with the (unmeasurable) flux function. A new potentially observable dimensionless frozen flux rate, ΛΦ, differentiates significant from anecdotal frozen flux slippage. A single spacecraft observable, ϒ, is shown with PIC simulations to be essentially proportional to the unobservable local Maxwell frozen flux rate. This relationship theoretically establishes electron demagnetization in 3D as the general cause of frozen flux slippage. In simple 2D cases with an isolated central diffusion region surrounded by separatrices, these diagnostics uniquely identify the traditional diffusion region (without confusing it with the two fluid "ion-diffusion" region) and clarify the role of the separatrices where frozen flux violations do occur but are not substantial. In the more complicated guide and asymmetric 2D cases, substantial flux slippage regions extend out along, but inside of, the preferred separatrices, demonstrating that

  11. Effects of the reconnection electric field on crescent electron distribution functions in asymmetric guide field reconnection

    Science.gov (United States)

    Bessho, N.; Chen, L. J.; Hesse, M.; Wang, S.

    2017-12-01

    In asymmetric reconnection with a guide field in the Earth's magnetopause, electron motion in the electron diffusion region (EDR) is largely affected by the guide field, the Hall electric field, and the reconnection electric field. The electron motion in the EDR is neither simple gyration around the guide field nor simple meandering motion across the current sheet. The combined meandering motion and gyration has essential effects on particle acceleration by the in-plane Hall electric field (existing only in the magnetospheric side) and the out-of-plane reconnection electric field. We analyze electron motion and crescent-shaped electron distribution functions in the EDR in asymmetric guide field reconnection, and perform 2-D particle-in-cell (PIC) simulations to elucidate the effect of reconnection electric field on electron distribution functions. Recently, we have analytically expressed the acceleration effect due to the reconnection electric field on electron crescent distribution functions in asymmetric reconnection without a guide field (Bessho et al., Phys. Plasmas, 24, 072903, 2017). We extend the theory to asymmetric guide field reconnection, and predict the crescent bulge in distribution functions. Assuming 1D approximation of field variations in the EDR, we derive the time period of oscillatory electron motion (meandering + gyration) in the EDR. The time period is expressed as a hybrid of the meandering period and the gyro period. Due to the guide field, electrons not only oscillate along crescent-shaped trajectories in the velocity plane perpendicular to the antiparallel magnetic fields, but also move along parabolic trajectories in the velocity plane coplanar with magnetic field. The trajectory in the velocity space gradually shifts to the acceleration direction by the reconnection electric field as multiple bounces continue. Due to the guide field, electron distributions for meandering particles are bounded by two paraboloids (or hyperboloids) in the

  12. Reconnecting Youth. What Works Clearinghouse Intervention Report

    Science.gov (United States)

    What Works Clearinghouse, 2015

    2015-01-01

    "Reconnecting Youth" is an elective, credit-bearing course for students at risk of dropping out of school due to frequent absenteeism, low grades, or a history of dropping out. The curriculum focuses on building self-esteem, decision making, personal control, and interpersonal communication skills. The What Works Clearninghouse (WWC)…

  13. Improved theory of collisionless particle motion in stellarators

    International Nuclear Information System (INIS)

    Mynick, H.E.

    1983-01-01

    A theory of particle motion in stellarators is developed which, in contrast to previous work, is both realistic enough to account for collisionless detrapping, yet simple enough that most features of the orbits can be expressed in analytic, reasonably simple formulas. From the study of detrapping, a systematic, complete classification of possible orbit types emerges. The theory is valid for a class of stellarator configurations which contains the standard model traditionally envisaged, as well as somewhat more complex configurations recently found to have favorable transport properties. The reasons for the differences in transport between configurations are elucidated

  14. Magnetic Reconnection Rate in Space Plasmas: A Fractal Approach

    International Nuclear Information System (INIS)

    Materassi, Massimo; Consolini, Giuseppe

    2007-01-01

    Magnetic reconnection is generally discussed via a fluid description. Here, we evaluate the reconnection rate assuming a fractal topology of the reconnection region. The central idea is that the fluid hypothesis may be violated at the scales where reconnection takes place. The reconnection rate, expressed as the Alfven Mach number of the plasma moving toward the diffusion region, is shown to depend on the fractal dimension and on the sizes of the reconnection or diffusion region. This mechanism is more efficient than prediction of the Sweet-Parker model and even Petschek's model for finite magnetic Reynolds number. A good agreement also with rates given by Hall MHD models is found. A discussion of the fractal assumption on the diffusion region in terms of current microstructures is proposed. The comparison with in-situ satellite observations suggests the reconnection region to be a filamentary domain

  15. Electron heating and energy inventory during asymmetric reconnection in a laboratory plasma

    Science.gov (United States)

    Yoo, J.; Na, B.; Jara-Almonte, J.; Yamada, M.; Ji, H.; Roytershteyn, V.; Argall, M. R.; Fox, W.; Chen, L. J.

    2017-12-01

    Electron heating and the energy inventory during asymmetric reconnection are studied in the Magnetic Reconnection Experiment (MRX) [1]. In this plasma, the density ratio is about 8 across the current sheet. Typical features of asymmetric reconnection such as the large density gradients near the low-density-side separatrices, asymmetric in-plane electric field, and bipolar out-of-plane magnetic field are observed. Unlike the symmetric case [2], electrons are also heated near the low-density-side separatrices. The measured parallel electric field may explain the observed electron heating. Although large fluctuations driven by lower-hybrid drift instabilities are also observed near the low-density-side separatrices, laboratory measurements and numerical simulations reported here suggest that they do not play a major role in electron energization. The average electron temperature increase in the exhaust region is proportional to the incoming magnetic energy per an electron/ion pair but exceeds the scaling of the previous space observations [3]. This discrepancy is explained by differences in the boundary condition and system size. The profile of electron energy gain from the electric field shows that there is additional electron energy gain associated with the electron diamagnetic current besides a large energy gain near the X-line. This additional energy gain increases electron enthalpy, not the electron temperature. Finally, a quantitative analysis of the energy inventory during asymmetric reconnection is conducted. Unlike the symmetric case where the ion energy gain is about twice more than the electron energy gain [4], electrons and ions obtain a similar amount of energy during asymmetric reconnection. [1] J. Yoo et al., accepted for a publication in J. Geophys. Res. [2] J. Yoo et al., Phys. Plasmas 21, 055706 (2014). [3] T. Phan et al., Geophys. Res. Lett. 40, 4475 (2013). [4] M. Yamada et al., Nat. Comms. 5, 4474 (2014).

  16. The relation between reconnected flux, the parallel electric field, and the reconnection rate in a three-dimensional kinetic simulation of magnetic reconnection

    International Nuclear Information System (INIS)

    Wendel, D. E.; Olson, D. K.; Hesse, M.; Kuznetsova, M.; Adrian, M. L.; Aunai, N.; Karimabadi, H.; Daughton, W.

    2013-01-01

    We investigate the distribution of parallel electric fields and their relationship to the location and rate of magnetic reconnection in a large particle-in-cell simulation of 3D turbulent magnetic reconnection with open boundary conditions. The simulation's guide field geometry inhibits the formation of simple topological features such as null points. Therefore, we derive the location of potential changes in magnetic connectivity by finding the field lines that experience a large relative change between their endpoints, i.e., the quasi-separatrix layer. We find a good correspondence between the locus of changes in magnetic connectivity or the quasi-separatrix layer and the map of large gradients in the integrated parallel electric field (or quasi-potential). Furthermore, we investigate the distribution of the parallel electric field along the reconnecting field lines. We find the reconnection rate is controlled by only the low-amplitude, zeroth and first–order trends in the parallel electric field while the contribution from fluctuations of the parallel electric field, such as electron holes, is negligible. The results impact the determination of reconnection sites and reconnection rates in models and in situ spacecraft observations of 3D turbulent reconnection. It is difficult through direct observation to isolate the loci of the reconnection parallel electric field amidst the large amplitude fluctuations. However, we demonstrate that a positive slope of the running sum of the parallel electric field along the field line as a function of field line length indicates where reconnection is occurring along the field line

  17. Non-linear growth of double tearing mode: Explosive reconnection, plasmoid formation, and particle acceleration

    Science.gov (United States)

    Akramov, Tohir; Baty, Hubert

    2017-08-01

    The nonlinear evolution of double tearing modes (DTMs) is investigated within the framework of resistive magnetohydrodynamic (MHD) simulations in a two-dimensional Cartesian geometry. We have explored the explosive reconnection phase associated with the growth of the secondary structure-driven instability for a range of resistivity values. The time scale of the explosive phase (that is of order of a few Alfvénic time scales) is shown to be quasi-independent of the resistivity, even when fast growing plasmoids develop for the highest enough Lundquist number cases. Test particle accelerations are performed using the MHD explosive simulations as input parameters. Our results show that reconnection DTM dynamics is able to provide an efficient process for accelerating charged particles far beyond characteristic thermal velocities within the reconnection layers. The main acceleration mechanism is attributed to the strong inductive electric field generated by the island structure-driven instability, with an additional smaller contribution due to the presence of plasmoids. Finally, our results are used to discuss some features of the accelerated particle spectra during flaring activity in the solar corona.

  18. Reconnection at the high and low latitude magnetopause

    Science.gov (United States)

    Dunlop, Malcolm; Zhang, Qinghe; Yulia, Bogdanova; Zuyin, Pu; Hiroshi, Hasegawa; Karlheinz, Trattner; Chao, Shen; Jun, Zhong; Matthew, Taylor; Jean, Berchem; Jiankui, Shi; Benoit, Lavraud; Jonathen, Eastwood; Jiansen, He; Martin, Volwerk; Andrew, Fazakerley; David, Sibeck; Dragos, Constantinescu; Harald, Frey; Philippe, Escoubet

    2013-04-01

    Recent investigations have renewed the debate on the occurrence and location of magnetic reconnection (MR) on the Earth's dayside magnetopause, where evidence exists for predominantly component driven X-line regions, independent of guide field conditions, and extending across a wide range of preferred, and often multiple, locations. Recent findings in active sites of MR have also increased the theoretical understanding of the detailed structure within the ion diffusion region surrounding the magnetic X-line or null field, although direct measurements of this small region are still relatively rare. Nevertheless, investigations have benefitted from an unprecedented growth in complexity of multi-scale and multi-point, in situ measurements, on the small and meso-scale, from, for example, the Cluster and THEMIS space missions. Furthermore, during April to July 2007 a combination of 10 spacecraft (Cluster, THEMIS and Double Star TC-1) provided simultaneous monitoring of the dayside magnetopause across a wide range of local times. Here, we first investigate repeated sampling of the ion diffusion region and associated null magnetic field of a high-latitude reconnection site by the four Cluster spacecraft flying in formation to interpret the plasma structures surrounding the X-line, which is located on initially closed field-lines and where the magnetic field orientations inside and outside the magnetopause are close to anti-parallel. The plasma populations confirm details of the ion and electron mixing, time history and acceleration through the current layer. We secondly investigate the plasma distributions near X-line structures for key conjunctions of the Cluster, THEMIS and TC-1 spacecraft around the magnetopause, showing the operation of MR at wide locations along the expected sub-solar merging line. The results are also consistent with the occurrence of reconnection activity, simultaneously across the sub-solar and flank magnetopause, linked to the (large

  19. A Family of Vortices to Study Axisymmetric Vortex Breakdown and Reconnection

    Science.gov (United States)

    Young, Larry A.

    2007-01-01

    A new analytic model describing a family of vortices has been developed to study some of the axisymmetric vortex breakdown and reconnection fluid dynamic processes underlying body-vortex interactions that are frequently manifested in rotorcraft and propeller-driven fixed-wing aircraft wakes. The family of vortices incorporates a wide range of prescribed initial vorticity distributions -- including single or dual-core vorticity distributions. The result is analytical solutions for the vorticity and velocities for each member of the family of vortices. This model is of sufficient generality to further illustrate the dependence of vortex reconnection and breakdown on initial vorticity distribution as was suggested by earlier analytical work. This family of vortices, though laminar in nature, is anticipated to provide valuable insight into the vortical evolution of large-scale rotor and propeller wakes.

  20. Experimental study of ion heating and acceleration during magnetic reconnection

    International Nuclear Information System (INIS)

    Hsu, S.C.

    2000-01-01

    This dissertation reports an experimental study of ion heating and acceleration during magnetic reconnection, which is the annihilation and topological rearrangement of magnetic flux in a conductive plasma. Reconnection is invoked often to explain particle heating and acceleration in both laboratory and naturally occurring plasmas. However, a simultaneous account of reconnection and its associated energy conversion has been elusive due to the extreme inaccessibility of reconnection events, e.g. in the solar corona, the Earth's magnetosphere, or in fusion research plasmas. Experiments for this work were conducted on MRX (Magnetic Reconnection Experiment), which creates a plasma environment allowing the reconnection process to be isolated, reproduced, and diagnosed in detail. Key findings of this work are the identification of local ion heating during magnetic reconnection and the determination that non-classical effects must provide the heating mechanism. Measured ion flows are sub-Alfvenic and can provide only slight viscous heating, and classical ion-electron interactions can be neglected due to the very long energy equipartition time. The plasma resistivity in the reconnection layer is seen to be enhanced over the classical value, and the ion heating is observed to scale with the enhancement factor, suggesting a relationship between the magnetic energy dissipation mechanism and the ion heating mechanism. The observation of non-classical ion heating during reconnection has significant implications for understanding the role played by non-classical dissipation mechanisms in generating fast reconnection. The findings are relevant for many areas of space and laboratory plasma research, a prime example being the currently unsolved problem of solar coronal heating. In the process of performing this work, local measurements of ion temperature and flows in a well-characterized reconnection layer were obtained for the first time in either laboratory or observational

  1. Experimental study of ion heating and acceleration during magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, S.C.

    2000-01-28

    This dissertation reports an experimental study of ion heating and acceleration during magnetic reconnection, which is the annihilation and topological rearrangement of magnetic flux in a conductive plasma. Reconnection is invoked often to explain particle heating and acceleration in both laboratory and naturally occurring plasmas. However, a simultaneous account of reconnection and its associated energy conversion has been elusive due to the extreme inaccessibility of reconnection events, e.g. in the solar corona, the Earth's magnetosphere, or in fusion research plasmas. Experiments for this work were conducted on MRX (Magnetic Reconnection Experiment), which creates a plasma environment allowing the reconnection process to be isolated, reproduced, and diagnosed in detail. Key findings of this work are the identification of local ion heating during magnetic reconnection and the determination that non-classical effects must provide the heating mechanism. Measured ion flows are sub-Alfvenic and can provide only slight viscous heating, and classical ion-electron interactions can be neglected due to the very long energy equipartition time. The plasma resistivity in the reconnection layer is seen to be enhanced over the classical value, and the ion heating is observed to scale with the enhancement factor, suggesting a relationship between the magnetic energy dissipation mechanism and the ion heating mechanism. The observation of non-classical ion heating during reconnection has significant implications for understanding the role played by non-classical dissipation mechanisms in generating fast reconnection. The findings are relevant for many areas of space and laboratory plasma research, a prime example being the currently unsolved problem of solar coronal heating. In the process of performing this work, local measurements of ion temperature and flows in a well-characterized reconnection layer were obtained for the first time in either laboratory or observational

  2. Localized Oscillatory Energy Conversion in Magnetopause Reconnection

    Science.gov (United States)

    Burch, J. L.; Ergun, R. E.; Cassak, P. A.; Webster, J. M.; Torbert, R. B.; Giles, B. L.; Dorelli, J. C.; Rager, A. C.; Hwang, K.-J.; Phan, T. D.; Genestreti, K. J.; Allen, R. C.; Chen, L.-J.; Wang, S.; Gershman, D.; Le Contel, O.; Russell, C. T.; Strangeway, R. J.; Wilder, F. D.; Graham, D. B.; Hesse, M.; Drake, J. F.; Swisdak, M.; Price, L. M.; Shay, M. A.; Lindqvist, P.-A.; Pollock, C. J.; Denton, R. E.; Newman, D. L.

    2018-02-01

    Data from the NASA Magnetospheric Multiscale mission are used to investigate asymmetric magnetic reconnection at the dayside boundary between the Earth's magnetosphere and the solar wind. High-resolution measurements of plasmas and fields are used to identify highly localized ( 15 electron Debye lengths) standing wave structures with large electric field amplitudes (up to 100 mV/m). These wave structures are associated with spatially oscillatory energy conversion, which appears as alternatingly positive and negative values of J · E. For small guide magnetic fields the wave structures occur in the electron stagnation region at the magnetosphere edge of the electron diffusion region. For larger guide fields the structures also occur near the reconnection X-line. This difference is explained in terms of channels for the out-of-plane current (agyrotropic electrons at the stagnation point and guide field-aligned electrons at the X-line).

  3. Space weather. Ionospheric control of magnetotail reconnection.

    Science.gov (United States)

    Lotko, William; Smith, Ryan H; Zhang, Binzheng; Ouellette, Jeremy E; Brambles, Oliver J; Lyon, John G

    2014-07-11

    Observed distributions of high-speed plasma flows at distances of 10 to 30 Earth radii (R(E)) in Earth's magnetotail neutral sheet are highly skewed toward the premidnight sector. The flows are a product of the magnetic reconnection process that converts magnetic energy stored in the magnetotail into plasma kinetic and thermal energy. We show, using global numerical simulations, that the electrodynamic interaction between Earth's magnetosphere and ionosphere produces an asymmetry consistent with observed distributions in nightside reconnection and plasmasheet flows and in accompanying ionospheric convection. The primary causal agent is the meridional gradient in the ionospheric Hall conductance which, through the Cowling effect, regulates the distribution of electrical currents flowing within and between the ionosphere and magnetotail. Copyright © 2014, American Association for the Advancement of Science.

  4. General connected and reconnected fields in plasmas

    Science.gov (United States)

    Mahajan, Swadesh M.; Asenjo, Felipe A.

    2018-02-01

    For plasma dynamics, more encompassing than the magnetohydrodynamical (MHD) approximation, the foundational concepts of "magnetic reconnection" may require deep revisions because, in the larger dynamics, magnetic field is no longer connected to the fluid lines; it is replaced by more general fields (one for each plasma specie) that are weighted combination of the electromagnetic and the thermal-vortical fields. We study the two-fluid plasma dynamics plasma expressed in two different sets of variables: the two-fluid (2F) description in terms of individual fluid velocities, and the one-fluid (1F) variables comprising the plasma bulk motion and plasma current. In the 2F description, a Connection Theorem is readily established; we show that, for each specie, there exists a Generalized (Magnetofluid/Electro-Vortic) field that is frozen-in the fluid and consequently remains, forever, connected to the flow. This field is an expression of the unification of the electromagnetic, and fluid forces (kinematic and thermal) for each specie. Since the magnetic field, by itself, is not connected in the first place, its reconnection is never forbidden and does not require any external agency (like resistivity). In fact, a magnetic field reconnection (local destruction) must be interpreted simply as a consequence of the preservation of the dynamical structure of the unified field. In the 1F plasma description, however, it is shown that there is no exact physically meaningful Connection Theorem; a general and exact field does not exist, which remains connected to the bulk plasma flow. It is also shown that the helicity conservation and the existence of a Connected field follow from the same dynamical structure; the dynamics must be expressible as an ideal Ohm's law with a physical velocity. This new perspective, emerging from the analysis of the post MHD physics, must force us to reexamine the meaning as well as our understanding of magnetic reconnection.

  5. Global Magnetospheric Modeling of 3D Reconnection

    Science.gov (United States)

    Spicer, Daniel S.

    1999-01-01

    A review of approaches to the global modeling of the terrestrial magnetosphere, how these approaches are utilized to interpret satellite data, and how these approaches have been successful at predicting magnetospheric phenomena will be presented. In addition, the importance of the ionospheric boundary and its effect on the globally topology of the magnetospheric magnetic field will be reviewed. In particular, numerical results that are rapidly changing our view of magnetospheric reconnection within the magnetospheric magnetic field will be discussed.

  6. Distant plasma sheet ion distributions during reconnection

    OpenAIRE

    Owen, C. J.; Mist, R. T.

    2001-01-01

    Previous models of the plasma sheet following reconnection and current sheet acceleration predict 'lima-bean' ion distributions. These are inconsistent with observational constraints. We postulate that following initial interaction with the current sheet, a fraction of outflow ions are backscattered and re-encounter the current sheet. Fermi acceleration processes then generate an additional high-energy outflow population. In the backscatter region these ions form a complete shell in velocity ...

  7. Hermite Polynomials and the Inverse Problem for Collisionless Equilibria

    Science.gov (United States)

    Allanson, O.; Neukirch, T.; Troscheit, S.; Wilson, F.

    2017-12-01

    It is long established that Hermite polynomial expansions in either velocity or momentum space can elegantly encode the non-Maxwellian velocity-space structure of a collisionless plasma distribution function (DF). In particular, Hermite polynomials in the canonical momenta naturally arise in the consideration of the 'inverse problem in collisionless equilibria' (IPCE): "for a given macroscopic/fluid equilibrium, what are the self-consistent Vlasov-Maxwell equilibrium DFs?". This question is of particular interest for the equilibrium and stability properties of a given macroscopic configuration, e.g. a current sheet. It can be relatively straightforward to construct a formal solution to IPCE by a Hermite expansion method, but several important questions remain regarding the use of this method. We present recent work that considers the necessary conditions of non-negativity, convergence, and the existence of all moments of an equilibrium DF solution found for IPCE. We also establish meaningful analogies between the equations that link the microscopic and macrosopic descriptions of the Vlasov-Maxwell equilibrium, and those that solve the initial value problem for the heat equation. In the language of the heat equation, IPCE poses the pressure tensor as the 'present' heat distribution over an infinite domain, and the non-Maxwellian features of the DF as the 'past' distribution. We find sufficient conditions for the convergence of the Hermite series representation of the DF, and prove that the non-negativity of the DF can be dependent on the magnetisation of the plasma. For DFs that decay at least as quickly as exp(-v^2/4), we show non-negativity is guaranteed for at least a finite range of magnetisation values, as parameterised by the ratio of the Larmor radius to the gradient length scale. 1. O. Allanson, T. Neukirch, S. Troscheit & F. Wilson: From one-dimensional fields to Vlasov equilibria: theory and application of Hermite polynomials, Journal of Plasma Physics, 82

  8. Plasmoid statistics in relativistic magnetic reconnection

    Science.gov (United States)

    Petropoulou, M.; Christie, I. M.; Sironi, L.; Giannios, D.

    2018-04-01

    Plasmoids, overdense blobs of plasma containing magnetic fields and high-energy particles, are a self-consistent outcome of the reconnection process in the relativistic regime. Recent two-dimensional particle-in-cell (PIC) simulations have shown that plasmoids can undergo a variety of processes (e.g. mergers, bulk acceleration, growth, and advection) within the reconnection layer. We developed a Monte Carlo code, benchmarked with the recent PIC simulations, to examine the effects of these processes on the steady-state size and momentum distributions of the plasmoid chain. The differential plasmoid size distribution is shown to be a power law, ranging from a few plasma skin depths to ˜0.1 of the reconnection layer's length. The power-law slope is shown to be linearly dependent upon the ratio of the plasmoid acceleration and growth rates, which slightly decreases with increasing plasma magnetization. We perform a detailed comparison of our results with those of recent PIC simulations and briefly discuss the astrophysical implications of our findings through the representative case of flaring events from blazar jets.

  9. Why fast magnetic reconnection is so prevalent

    Science.gov (United States)

    Boozer, Allen H.

    2018-02-01

    Evolving magnetic fields are shown to generically reach a state of fast magnetic reconnection in which magnetic field line connections change and magnetic energy is released at an Alfvénic rate. This occurs even in plasmas with zero resistivity; only the finiteness of the mass of the lightest charged particle, an electron, is required. The speed and prevalence of Alfvénic or fast magnetic reconnection imply that its cause must be contained within the ideal evolution equation for magnetic fields, , where is the velocity of the magnetic field lines. For a generic , neighbouring magnetic field lines develop a separation that increases exponentially, as \\unicode[STIX]{x1D70E(\\ell ,t)}$ with the distance along a line. This exponentially enhances the sensitivity of the evolution to non-ideal effects. An analogous effect, the importance of stirring to produce a large-scale flow and enhance mixing, has been recognized by cooks through many millennia, but the importance of the large-scale flow to reconnection is customarily ignored. In part this is due to the sixty-year focus of recognition theory on two-coordinate models, which eliminate the exponential enhancement that is generic with three coordinates. A simple three-coordinate model is developed, which could be used to address many unanswered questions.

  10. Intermittent magnetic reconnection in TS-3 merging experiment

    International Nuclear Information System (INIS)

    Ono, Y.; Hayashi, Y.; Ii, T.; Tanabe, H.; Ito, S.; Kuwahata, A.; Ito, T.; Kamino, Y.; Yamada, T.; Inomoto, M.

    2011-01-01

    Ejection of current sheet with plasma mass causes impulsive and intermittent magnetic reconnection in the TS-3 spherical tokamak (ST) merging experiment. Under high guide toroidal field, the sheet resistivity is almost classical due to the sheet thickness much longer than the ion gyroradius. Large inflow flux and low current-sheet resistivity result in flux and plasma pileup followed by rapid growth of the current sheet. When the pileup exceeds a critical limit, the sheet is ejected mechanically from the squeezed X-point area. The reconnection (outflow) speed is slow during the flux/plasma pileup and is fast during the ejection, suggesting that intermittent reconnection similar to the solar flare increases the averaged reconnection speed. These transient effects enable the merging tokamaks to have the fast reconnection as well as the high-power reconnection heating, even when their current-sheet resistivity is low under high guide field.

  11. An Electromagnetic Drift Instability in the Magnetic Reconnection Experiment (MRX) and its Importance for Magnetic Reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Russell Kulsrud; Hantao Ji; Will Fox; Masaaki Yamada

    2005-06-07

    The role which resistivity plays in breaking magnetic field lines, heating the plasma, and plasma field slippage during magnetic reconnection is discussed. Magnetic fluctuations are observed in the MRX (Magnetic Reconnection Experiment) that are believed to provide resistive friction or wave resistivity. A localized linear theory has been proposed for their origin as an obliquely propagating Lower Hybrid Drift Instability. In this paper, the linear theory of the instability is summarized, and the resulting heating and slippage are calculated from quasi-linear theory. Making use of measured amplitudes of the magnetic fluctuations in the MRX the amount of these effects is estimated. Within the experimental uncertainties they are shown to be quite important for the magnetic reconnection process.

  12. Laminar wave train structure of collisionless magnetic slow shocks

    Science.gov (United States)

    Coroniti, F. V.

    1970-01-01

    The laminar wave train structure of collisionless magnetic slow shocks is investigated using two fluid hydromagnetics with ion cyclotron radius dispersion. For shock strengths less than the maximally strong switch-off shock, in the shock leading edge dispersive steepening forms a magnetic field gradient, while in the downstream flow dispersive propagation forms a trailing wave train; dispersion scale lengths are the ion inertial length if beta is smaller than 1 and the ion cyclotron radius if beta is greater than 1. In the switch-off slow shock leading edge, dispersion only produced rotations of the magnetic field direction; the gradient of the magnetic field magnitude, and hence the shock steepening length, is determined solely by resistive diffusion. The switch-off shock structure consists of a long trailing of magnetic rotations which are gradually damped by resistivity.

  13. Physics of Collisionless Shocks Space Plasma Shock Waves

    CERN Document Server

    Balogh, André

    2013-01-01

    The present book provides a contemporary systematic treatment of shock waves in high-temperature collisionless plasmas as are encountered in near Earth space and in Astrophysics. It consists of two parts. Part I develops the complete theory of shocks in dilute hot plasmas under the assumption of absence of collisions among the charged particles when the interaction is mediated solely by the self-consistent electromagnetic fields. Such shocks are naturally magnetised implying that the magnetic field plays an important role in their evolution and dynamics. This part treats both subcritical shocks, which dissipate flow energy by generating anomalous resistance or viscosity, and supercritical shocks. The main emphasis is, however, on super-critical shocks where the anomalous dissipation is insufficient to retard the upstream flow. These shocks, depending on the direction of the upstream magnetic field, are distinguished as quasi-perpendicular and quasi-parallel shocks which exhibit different behaviours, reflecti...

  14. Collisionless Plasma Modeling in an Arbitrary Potential Energy Distribution

    Science.gov (United States)

    Liemohn, M. W.; Khazanov, G. V.

    1997-01-01

    A new technique for calculating a collisionless plasma along a field line is presented. The primary feature of the new model is that it can handle an arbitrary (including nonmonotonic) potential energy distribution. This was one of the limiting constraints on the existing models in this class, and these constraints are generalized for an arbitrary potential energy composition. The formulation for relating current density to the field-aligned potential as well as formulas for density, temperature and energy flux calculations are presented for several distribution functions, ranging from a bi-Lorentzian with a loss cone to an isotropic Maxwellian. A comparison of these results with previous models shows that the formulation reduces.to the earlier models under similar assumptions.

  15. Collisionless shocks in self-interacting dark matter

    Science.gov (United States)

    Heikinheimo, Matti; Raidal, Martti; Spethmann, Christian; Veermäe, Hardi

    2018-01-01

    Self-interacting dark matter (DM) has been proposed as a solution to small scale problems in cosmological structure formation, and hints of DM self scattering have been observed in mergers of galaxy clusters. One of the simplest models for self-interacting DM is a particle that is charged under dark electromagnetism, a new gauge interaction analogous to the usual electromagnetic force, but operating on the DM particle instead of the visible particles. In this case, the collisional behaviour of DM is primarily due to the formation of collisionless shocks, that should affect the distribution of DM in merging galaxy clusters. We evaluate the time and length scales of shock formation in cluster mergers, and discuss the implications for modelling charged DM in cosmological simulations.

  16. Transport scaling in the collisionless-detrapping regime in stellarators

    International Nuclear Information System (INIS)

    Crume, E.C. Jr.; Shaing, K.C.; Hirshman, S.P.; van Rij, W.I.

    1987-09-01

    Stellarator transport scalings with electric field, geometry, and collision frequency in the reactor-relevant collisionless-detrapping regime are determined from numerical solutions of the drift kinetic equation. A new geometrical scaling, proportional to ε/sub t/sup 3/2/ rather than ε/sub t/ε/sub h/sup 1/2/, is found, where ε/sub t/ is the inverse aspect ratio and ε/sub h/ is the helical ripple. With the new scaling, no reduction in energy confinement time is associated with large helical ripple, which provides design flexibility. Integral expressions for the particle and heat fluxes that are useful for transport simulations are given. 11 refs

  17. RESOLVING THE FAN-SPINE RECONNECTION GEOMETRY OF A SMALL-SCALE CHROMOSPHERIC JET EVENT WITH THE NEW SOLAR TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Zhicheng; Chen, Bin; Goode, Philip R.; Cao, Wenda [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Boulevard, Newark, NJ 07102 (United States); Ji, Haisheng [Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 (United States)

    2016-03-01

    Jets are ubiquitously present in both quiet and active regions on the Sun. They are widely believed to be driven by magnetic reconnection. A fan-spine structure has been frequently reported in some coronal jets and flares, and has been regarded as a signature of ongoing magnetic reconnection in a topology consisting of a magnetic null connected by a fan-like separatrix surface and a spine. However, for small-scale chromospheric jets, clear evidence of such structures is rather rare, although it has been implied in earlier works that showed an inverted-Y-shaped feature. Here we report high-resolution (0.″16) observations of a small-scale chromospheric jet obtained by the New Solar Telescope (NST) using 10830 Å filtergrams. Bi-directional flows were observed across the separatrix regions in the 10830 Å images, suggesting that the jet was produced due to magnetic reconnection. At the base of the jet, a fan-spine structure was clearly resolved by the NST, including the spine and the fan-like surface, as well as the loops before and after the reconnection. A major part of this fan-spine structure, with the exception of its bright footpoints and part of the base arc, was invisible in the extreme ultraviolet and soft X-ray images (observed by the Atmosphere Imaging Assembly and the X-Ray Telescope, respectively), indicating that the reconnection occurred in the upper chromosphere. Our observations suggest that the evolution of this chromospheric jet is consistent with a two-step reconnection scenario proposed by Török et al.

  18. Simultaneous Observations of p-mode Light Walls and Magnetic Reconnection Ejections above Sunspot Light Bridges

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Yijun; Zhang, Jun; Li, Ting; Yang, Shuhong; Li, Xiaohong, E-mail: yijunhou@nao.cas.cn, E-mail: zjun@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2017-10-10

    Recent high-resolution observations from the Interface Region Imaging Spectrograph reveal bright wall-shaped structures in active regions (ARs), especially above sunspot light bridges. Their most prominent feature is the bright oscillating front in the 1400/1330 Å channel. These structures are named light walls and are often interpreted to be driven by p-mode waves. Above the light bridge of AR 12222 on 2014 December 06, we observed intermittent ejections superimposed on an oscillating light wall in the 1400 Å passband. At the base location of each ejection, the emission enhancement was detected in the Solar Dynamics Observatory 1600 Å channel. Thus, we suggest that in wall bases (light bridges), in addition to the leaked p-mode waves consistently driving the oscillating light wall, magnetic reconnection could happen intermittently at some locations and eject the heated plasma upward. Similarly, in the second event occurring in AR 12371 on 2015 June 16, a jet was simultaneously detected in addition to the light wall with a wave-shaped bright front above the light bridge. At the footpoint of this jet, lasting brightening was observed, implying magnetic reconnection at the base. We propose that in these events, two mechanisms, p-mode waves and magnetic reconnection, simultaneously play roles in the light bridge, and lead to the distinct kinetic features of the light walls and the ejection-like activities, respectively. To illustrate the two mechanisms and their resulting activities above light bridges, in this study we present a cartoon model.

  19. Comparison of reconnection in magnetosphere and solar corona

    Science.gov (United States)

    Imada, Shinsuke; Hirai, Mariko; Isobe, Hiroaki; Oka, Mitsuo; Watanabe, Kyoko; Minoshima, Takashi

    One of the most famous rapid energy conversion mechanisms in space is a magnetic reconnec-tion. The general concept of a magnetic reconnection is that the rapid energy conversion from magnetic field energy to thermal energy, kinetic energy or non-thermal particle energy. The understanding of rapid energy conversion rates from magnetic field energy to other energy is the fundamental and essential problem in the space physics. One of the important goals for studying magnetic reconnection is to answer what plasma condition/parameter controls the energy conversion rates. Earth's magnetotail has been paid much attention to discuss a mag-netic reconnection, because we can discuss magnetic reconnection characteristics in detail with direct in-situ observation. Recently, solar atmosphere has been focused as a space laboratory for magnetic reconnection because of its variety in plasma condition. So far considerable effort has been devoted toward understanding the energy conversion rates of magnetic reconnection, and various typical features associated with magnetic reconnection have been observed in the Earth's magnetotail and the solar corona. In this talk, we first introduce the variety of plasma condition/parameter in solar corona and Earth's magnetotail. Later, we discuss what plasma condition/parameter controls the energy conversion from magnetic field to especially non-thermal particle. To compare non-thermal electron and ion acceleration in magnetic reconnection, we used Hard X-ray (electron) /Neu-tron monitor (ion) for solar corona and Geotail in-situ measurement (electron and ion) for magnetoatil. We found both of electron and ion accelerations are roughly controlled by re-connection electric field (reconnection rate). However, some detail points are different in ion and electron acceleration. Further, we will discuss what is the major difference between solar corona and Earth's magnetotail for particle acceleration.

  20. Kinetic modeling of particle acceleration in a solar null point reconnection region

    DEFF Research Database (Denmark)

    Baumann, Gisela; Haugbølle, Troels; Nordlund, Åke

    2013-01-01

    The primary focus of this paper is on the particle acceleration mechanism in solar coronal 3D reconnection null-point regions. Starting from a potential field extrapolation of a SOHO magnetogram taken on 2002 November 16, we first performed MHD simulations with horizontal motions observed by SOHO......-relativistic electron acceleration is mainly driven by a systematic electric field in the current sheet. A non-thermal population of electrons with a power-law distribution in energy forms, featuring a power-law index of about -1.75. This work provides a first step towards bridging the gap between macroscopic scales...

  1. Progress in the theory of magnetic reconnection phenomena

    International Nuclear Information System (INIS)

    Ottaviani, M.; Arcis, N.; Maget, P.; Zwingmann, W.; Grasso, D.; Militello, F.; Porcelli, F.

    2004-01-01

    Recent theoretical work on magnetic reconnection in hot plasma confinement devices is reviewed. The presentation highlights the common aspects of reconnection phenomena, and current research trends are emphasised. Progress in understanding the dynamics of slowly evolving modes of the tearing family, based on advanced analytic techniques and numerical simulation, as well as of faster modes that lead to internal disruptions, is reported. (authors)

  2. Magnetic Reconnection at a Three-dimensional Solar Null Point

    DEFF Research Database (Denmark)

    Frederiksen, Jacob Trier; Baumann, Gisela; Galsgaard, Klaus

    2012-01-01

    Using a specific solar null point reconnection case studied by Masson et al (2009; ApJ 700, 559) we investigate the dependence of the reconnection rate on boundary driving speed, numerical resolution, type of resistivity (constant or numerical), and assumed stratification (constant density or sol...

  3. Diffusion region in magnetopause reconnection observed by the MMS mission

    Science.gov (United States)

    Chen, Li-Jen

    2017-10-01

    The diffusion region is the primary location where the plasmas are energized to dissipate the magnetic energy in reconnection. The NASA Magnetospheric Multiscale (MMS) mission, capable of resolving sub-gyroscales of both electrons and ions, has created new frontiers in the state-of-the-art understanding of the diffusion region. The MMS detection of reconnection at Earth's magnetopause will be discussed to highlight the roles of demagnetized particle orbits and wave fluctuations in the reconnection dynamics. When the guide field is significantly weaker than the reconnecting magnetic field, the reconnection current layer is gyro-resistive and the electron distribution functions exhibit strong finite-gyroradius effects with crescent and counterstreaming characteristics. When the guide field is comparable to the reconnecting component, the electron jets are mainly the E cross B drift due to the polarization electric field and the guide magnetic field, and the energy conversion at the jet reversal is dominated by the wave electric field near the lower hybrid frequency. Insensitive to the guide-field, the dense magnetosheath electrons in the reconnection exhaust are transported, by wave turbulence, across the magnetospheric separatrix to modify the plasma properties and field structures in the magnetosphere. The MMS results will be compared with available laboratory measurements from the Magnetic Reconnection Experiment in Princeton, and challenges in diffusion region physics will be discussed. The MMS and MRX teams are acknowledged. Work is supported by NASA, DOE, and NSF.

  4. Suprathermal electron acceleration during reconnection onset in the magnetotail

    Directory of Open Access Journals (Sweden)

    A. Vaivads

    2011-10-01

    Full Text Available We study one event of reconnection onset associated to a small substorm on 27 September 2006 by using Cluster observations at inter-spacecraft separation of about 10 000 km. We focus on the acceleration of suprathermal electrons during different stages of reconnection. We show that several distinct stages of acceleration occur: (1 moderate acceleration during reconnection of pre-existing plasma sheet flux tubes, (2 stronger acceleration during reconnection of lobe flux tubes, (3 production of the most energetic electrons within dipolarization fronts (magnetic pile-up regions. The strongest acceleration is reached at the location of Bz maxima inside the magnetic pile-up region where the reconnection jet stops. Very strong localized dawn-dusk electric field are observed within the magnetic pile-up regions and are associated to most of the magnetic flux transport.

  5. Review of recent experiments on magnetic reconnection in laboratory plasmas

    International Nuclear Information System (INIS)

    Yamada, M.

    1995-02-01

    The present paper reviews recent laboratory experiments on magnetic reconnection. Examples will be drawn from electron current sheet experiments, merging spheromaks, and from high temperature tokamak plasmas with the Lundquist numbers exceeding 10 7 . These recent laboratory experiments create an environment which satisfies the criteria for MHD plasma and in which the global boundary conditions can be controlled externally. Experiments with fully three dimensional reconnection are now possible. In the most recent TFTR tokamak discharges, Motional Stark effect (MSE) data have verified the existence of a partial reconnection. In the experiment of spheromak merging, a new plasma acceleration parallel to the neutral line has been indicated. Together with the relationship of these observations to the analysis of magnetic reconnection in space and in solar flares, important physics issues such as global boundary conditions, local plasma parameters, merging angle of the field lines, and the 3-D aspects of the reconnection are discussed

  6. Two-dimensional Reconnection Dynamics Using Particle-In-Cell and Hall MHD Simulations: A Comparative Study

    Science.gov (United States)

    Bessho, N.; Bhattacharjee, A.; Chandran, B.

    2003-10-01

    We present results of two new studies on magnetic reconnection dynamics obtained from two-dimensional fully electromagnetic particle-in-cell (PIC) simulations, and compare them with results obtained from earlier Hall MHD theory and simulations using the same initial conditions. Our studies include realistic values of me/mi. The first study involves the scaling of the maximum electron outflow velocity from the reconnnection region in the GEM Reconnection Challenge as a function of the electron mass, which Hall MHD models predict to scale as the electron Alfven speed. (This study has significant implications for particle detectors from the upcoming NASA MMS mission.) The PIC simulations exhibit flows that are uniformly smaller than the electron Alfven speed, with deviations that increase in magnitude as the mass ratio reaches its actual physical value. The second study involves forced magnetic reconnection in a Harris sheet driven by external electric fields which produce inward boundary flows. It is observed in the PIC simulations that the reconnection rate in the linear regime increases algebraically in time, and is followed by a sudden near-explosive enhancement in the nonlinear regime, qualitatively similar to that seen in earlier Hall MHD simulations. Quantitative comparisons between PIC and previous Hall MHD theory and simulations will be reported.

  7. X-Line Retreat During Magnetic Reconnection

    Science.gov (United States)

    Oka, Mitsuo; Fujimoto, M.; Shinohara, I.

    2008-03-01

    In many astro- and space- physics situations, we observe energy release processes in vicinities of an obstacle. In the Earth's magnetotail, an Earthward plasma flow hits the magnetosphere which might end up with magnetic field pile-up and/or dipolarization of the magnetosphere. During solar flares, in view of magnetic reconnection model, a downward plasma jet collides with a magnetic flux tube at the bottom of the solar corona.In order to study energe release processes in these situations, we have set up a hard wall (symmetric boundary) to model either dipole magnetic field in the Earth's magnetosphere or magnetic loops in the solar corona. For simplicity, we have neglected any density gradient or magnetic field strucures. The initial configuration of the current sheet is therefore of a Harris-type. After initiating magnetic reconnection by a magnetic field purturbation, its time evolution is studied by means of full particle, PIC simulation.The prominent feature in our simulation is a slow motion of the X-point directing away from the wall, which we call `X-line Retreat'. Our preliminary results show retreat speed to be about 0.1 times the Alfven speed measured at the boundaries. In our talk, we will discuss the mechanism and cause of the X-line retreat as well as the structures of the diffusion region. Implication on particle acceleration will also be addressed.

  8. Hall MHD reconnection in cometary magnetotail

    International Nuclear Information System (INIS)

    Jovanovic, Dusan; Shukla, Padma Kant; Morfill, Gregor

    2005-01-01

    The fine structure of cometary tails (swirls, loops and blobs) is studied in the framework of resistive magnetic reconnection without a guide field in a dusty plasma. For a high-beta plasma (β ∼ 1) consisting of electrons, ions, and immobile dust grains, a two-fluid description is used to study electromagnetic perturbations with the frequency below Ωi, propagating at an arbitrary angle, and including the effects of Hall current. A zero-order current associated with the anti-parallel magnetic configuration may exist even in the limit of zero plasma temperature in a dusty plasma due to a symmetry breaking between electrons and ions by dust grains that yields an E-vector x B-vector current. In the perturbed state, a new linear electromagnetic mode is found in dusty plasma which is evanescent below the Rao cut-off frequency and has the characteristic wavelength comparable to the ion skin depth, which enables the reconnection at short spatial scales. The role of the dust is found to be twofold, yielding a new mode outside of the current sheet and altering the continuity conditions at its edge by an inhomogeneous Doppler shift associated with the E-vector x B-vector current

  9. Effect of magnetic reconnection in stellar plasma

    Science.gov (United States)

    Hammoud, M.; El Eid, M.; Darwish, M.

    2017-06-01

    An important phenomenon in Astrophysics is the process of magnetic reconnection (MGR), which is envisaged to understand the solar flares, coronal mass ejection, interaction of the solar wind with the Earth’s magnetic field (so called geomagnetic storm) and other phenomena. In addition, it plays a role in the formation of stars. MGR involves topological change of a set of magnetic field lines leading to a new equilibrium configuration of lower magnetic energy. The MGR is basically described in the framework of the Maxwell’s equations linked to Navier-Stockes equations. Nevertheless, many details are still not understood. In this paper, we investigate the MGR process in the framework of the Magnetohydrodynamic (MHD) model of a single conducting fluid using a modern powerful computational tool (OpenFOAM). We will show that the MGR process takes place only if resistivity exists. However, despite the high conductivity of the plasma, resistivity becomes effective in a very thin layer generating sharp gradients of the magnetic field, and thus accelerating the reconnection process. The net effect of MGR is that magnetic energy is converted into thermal and kinetic energies leading to heating and acceleration of charged particles. The Sun’s coronal ejection is an example of the MGR process.

  10. PARTICLE ACCELERATION AND HEATING BY TURBULENT RECONNECTION

    Energy Technology Data Exchange (ETDEWEB)

    Vlahos, Loukas; Pisokas, Theophilos; Isliker, Heinz; Tsiolis, Vassilis [Department of Physics, Aristotle University of Thessaloniki, GR-52124 Thessaloniki (Greece); Anastasiadis, Anastasios [Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, GR-15236 Penteli (Greece)

    2016-08-10

    Turbulent flows in the solar wind, large-scale current sheets, multiple current sheets, and shock waves lead to the formation of environments in which a dense network of current sheets is established and sustains “turbulent reconnection.” We constructed a 2D grid on which a number of randomly chosen grid points are acting as scatterers (i.e., magnetic clouds or current sheets). Our goal is to examine how test particles respond inside this large-scale collection of scatterers. We study the energy gain of individual particles, the evolution of their energy distribution, and their escape time distribution. We have developed a new method to estimate the transport coefficients from the dynamics of the interaction of the particles with the scatterers. Replacing the “magnetic clouds” with current sheets, we have proven that the energization processes can be more efficient depending on the strength of the effective electric fields inside the current sheets and their statistical properties. Using the estimated transport coefficients and solving the Fokker–Planck (FP) equation, we can recover the energy distribution of the particles only for the stochastic Fermi process. We have shown that the evolution of the particles inside a turbulent reconnecting volume is not a solution of the FP equation, since the interaction of the particles with the current sheets is “anomalous,” in contrast to the case of the second-order Fermi process.

  11. Magnetorotational Turbulence and Dynamo in a Collisionless Plasma

    Science.gov (United States)

    Kunz, Matthew

    2017-10-01

    Low-luminosity black-hole accretion flows are collisionless. A kinetic approach is thus necessary to understand the transport of heat and angular momentum, the acceleration of particles, and the growth and structure of the magnetic field in these systems. I present results from the first 6D kinetic simulation of magnetorotational turbulence and dynamo, which was performed using the hybrid-kinetic particle-in-cell code Pegasus. Special attention will be paid to the transport of angular momentum by the anisotropic-pressure stress, as well as to the ion-Larmor-scale kinetic instabilities (firehose, mirror, ion-cyclotron) that regulate it. The latter endow the plasma with an effective viscosity that is biased with respect to the magnetic-field direction and spatiotemporally variable. Energy spectra suggest an Alfvén-wave cascade at large scales and a kinetic-Alfvén-wave cascade at small scales, with strong small-scale density fluctuations and weak nonaxisymmetric density waves. Ions undergo nonthermal particle acceleration, their distribution accurately described by a κ distribution. Dedicated nonlinear studies of firehose and mirror instabilities in a shearing plasma will also be presented as a complement to the study of the magnetorotational instability. The profits, perils, and price of using a kinetic approach are discussed.

  12. Collisionless spectral-kinetic Simulation of the Multipole Resonance Probe

    Science.gov (United States)

    Dobrygin, Wladislaw; Szeremley, Daniel; Schilling, Christian; Oberrath, Jens; Eremin, Denis; Mussenbrock, Thomas; Brinkmann, Ralf Peter

    2012-10-01

    Plasma resonance spectroscopy is a well established plasma diagnostic method realized in several designs. One of these designs is the multipole resonance probe (MRP). In its idealized - geometrically simplified - version it consists of two dielectrically shielded, hemispherical electrodes to which an RF signal is applied. A numerical tool is under development, which is capable of simulating the dynamics of the plasma surrounding the MRP in electrostatic approximation. In the simulation the potential is separeted in an inner and a vacuum potential. The inner potential is influenced by the charged partilces and is calculated by a specialized Poisson solver. The vacuum potential fulfills Laplace's equetion and consists of the applied voltage of the probe as boundary condition. Both potentials are expanded in spherical harmonics. For a practical particle pusher implementation, the expansion must be appropriately truncated. Compared to a PIC simulation a grid is unnecessary to calculate the force on the particles. This work purpose is a collisionless kinetic simulation, which can be used to investigate kinetic effects on the resonance behavior of the MRP.[4pt] [1] M. Lapke et al., Appl. Phys. Lett. 93, 2008, 051502.

  13. Investigations of electrostatic ion waves in a collisionless plasma

    International Nuclear Information System (INIS)

    Michelsen, P.

    1980-06-01

    The author reviews a series of publications concerning theoretical and experimental investigations of electrostatic ion waves in a collisionless plasma. The experimental work was performed in the Risoe Q-machine under various operational conditions. Besides a description of this machine and the diagnostic techniques used for the measurements, two kinds of electrostatic waves are treated, namely, ion-acoustic waves and ion-cyclotron waves. Due to the relative simplicity of the ion-acoustic waves, these were treated in detail in order to get a more general understanding of the behaviour of the propagation properties of electrostatic waves. The problem concerning the difficulties in describing waves excited at a certain position and propagating in space by a proper mathematical model was especially considered in depth. Furthermore, ion-acoustic waves were investigated which propagated in a plasma with a density gradient, and afterwards in a plasma with an ion beam. Finally, a study of the electrostatic ion-cyclotron waves was undertaken, and it was shown that these waves were unstable in a plasma traversed by an ion beam. (Auth.)

  14. Longitudinal sound waves in a collisionless, quasineutral plasma

    Science.gov (United States)

    Ramos, J. J.

    2017-12-01

    The time evolution of slow sound waves in a homogeneous, collisionless and quasineutral plasma, in particular their Landau damping, is investigated using the kinetic-magnetohydrodynamics formulation of Ramos (J. Plasma Phys. vol. 81, 2015 p. 905810325; vol. 82, 2016 p. 905820607). In this approach, the electric field is eliminated from a closed, hybrid fluid-kinetic system that ensures automatically the fulfilment of the charge neutrality condition. Considering the time dependence of a spatial-Fourier-mode linear perturbation with wavevector parallel to the equilibrium magnetic field, this can be cast as a second-order self-adjoint problem with a continuum spectrum of real and positive squared frequencies. Therefore, a conventional resolution of the identity with a continuum basis of singular normal modes is guaranteed, which simplifies significantly a Van Kampen-like treatment of the Landau damping. The explicit form of such singular normal modes is obtained, along with their orthogonality relations. These are used to derive the damped time evolution of the fluid moments of solutions of initial-value problems, for the most general kinds of initial conditions. The non-zero parallel electric field is not used explicitly in this analysis, but it is calculated from any given solution after the later has been obtained.

  15. Particle injection and cosmic ray acceleration at collisionless parallel shocks

    International Nuclear Information System (INIS)

    Quest, K.B.

    1987-01-01

    The structure of collisionless parallel shocks is studied using one-dimensional hybrid simulations, with emphasis on particle injection into the first-order Fermi acceleration process. It is argued that for sufficiently high Mach number shocks, and in the absence of wave turbulence, the fluid firehose marginal stability condition will be exceeded at the interface between the upstream, unshocked, plasma and the heated plasma downstream. As a consequence, nonlinear, low-frequency, electromagnetic waves are generated and act to slow the plasma and provide dissipation for the shock. It is shown that large amplitude waves at the shock ramp scatter a small fraction of the upstream ions back into the upstream medium. These ions, in turn, resonantly generate the electromagnetic waves that are swept back into the shock. As these waves propagate through the shock they are compressed and amplified, allowing them to non-resonantly scatter the bulk of the plasma. Moreover, the compressed waves back-scatter a small fraction of the upstream ions, maintaining the shock structure in a quasi-steady state. The back-scattered ions are accelerated during the wave generation process to 2 to 4 times the ram energy and provide a likely seed population for cosmic rays. 49 refs., 7 figs

  16. MODELING THE Ly α FOREST IN COLLISIONLESS SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Sorini, Daniele; Oñorbe, José; Hennawi, Joseph F. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Lukić, Zarija, E-mail: sorini@mpia-hd.mpg.de [Lawrence Berkeley National Laboratory, CA 94720-8139 (United States)

    2016-08-20

    Cosmological hydrodynamic simulations can accurately predict the properties of the intergalactic medium (IGM), but only under the condition of retaining the high spatial resolution necessary to resolve density fluctuations in the IGM. This resolution constraint prohibits simulating large volumes, such as those probed by BOSS and future surveys, like DESI and 4MOST. To overcome this limitation, we present “Iteratively Matched Statistics” (IMS), a novel method to accurately model the Ly α forest with collisionless N -body simulations, where the relevant density fluctuations are unresolved. We use a small-box, high-resolution hydrodynamic simulation to obtain the probability distribution function (PDF) and the power spectrum of the real-space Ly α forest flux. These two statistics are iteratively mapped onto a pseudo-flux field of an N -body simulation, which we construct from the matter density. We demonstrate that our method can reproduce the PDF, line of sight and 3D power spectra of the Ly α forest with good accuracy (7%, 4%, and 7% respectively). We quantify the performance of the commonly used Gaussian smoothing technique and show that it has significantly lower accuracy (20%–80%), especially for N -body simulations with achievable mean inter-particle separations in large-volume simulations. In addition, we show that IMS produces reasonable and smooth spectra, making it a powerful tool for modeling the IGM in large cosmological volumes and for producing realistic “mock” skies for Ly α forest surveys.

  17. SCALING LAW OF RELATIVISTIC SWEET-PARKER-TYPE MAGNETIC RECONNECTION

    International Nuclear Information System (INIS)

    Takahashi, Hiroyuki R.; Kudoh, Takahiro; Masada, Youhei; Matsumoto, Jin

    2011-01-01

    Relativistic Sweet-Parker-type magnetic reconnection is investigated by relativistic resistive magnetohydrodynamic (RRMHD) simulations. As an initial setting, we assume anti-parallel magnetic fields and a spatially uniform resistivity. A perturbation imposed on the magnetic fields triggers magnetic reconnection around a current sheet, and the plasma inflows into the reconnection region. The inflows are then heated due to ohmic dissipation in the diffusion region and finally become relativistically hot outflows. The outflows are not accelerated to ultrarelativistic speeds (i.e., Lorentz factor ≅ 1), even when the magnetic energy dominates the thermal and rest mass energies in the inflow region. Most of the magnetic energy in the inflow region is converted into the thermal energy of the outflow during the reconnection process. The energy conversion from magnetic to thermal energy in the diffusion region results in an increase in the plasma inertia. This prevents the outflows from being accelerated to ultrarelativistic speeds. We find that the reconnection rate R obeys the scaling relation R≅S -0.5 , where S is the Lundquist number. This feature is the same as that of non-relativistic reconnection. Our results are consistent with the theoretical predictions of Lyubarsky for Sweet-Parker-type magnetic reconnection.

  18. A new magnetic reconnection paradigm: Stochastic plasmoid chains

    Science.gov (United States)

    Loureiro, Nuno

    2015-11-01

    Recent analytical and numerical research in magnetic reconnection has converged on the notion that reconnection sites (current sheets) are unstable to the formation of multiple magnetic islands (plasmoids), provided that the system is sufficiently large (or, in other words, that the Lundquist number of the plasma is high). Nonlinearly, plasmoids come to define the reconnection geometry. Their nonlinear dynamics is rather complex and best thought of as new form of turbulence whose properties are determined by continuous plasmoid formation and their subsequent ejection from the sheet, as well as the interaction (coalescence) between plasmoids of different sizes. The existence of these stochastic plasmoid chains has powerful implications for several aspects of the reconnection process, from determining the reconnection rate to the details and efficiency of the energy conversion and dissipation. In addition, the plasmoid instability may also directly bear on the little understood problem of the reconnection trigger, or onset, i.e., the abrupt transition from a slow stage of energy accumulation to a fast (explosive) stage of energy release. This talk will first provide a brief overview of these recent developments in the reconnection field. I will then discuss recent work addressing the onset problem in the context of a forming current sheet which becomes progressively more unstable to the plasmoid instability. Work partially supported by Fundação para a Ciência e Tecnologia via Grants UID/FIS/50010/2013 and IF/00530/2013.

  19. Total magnetic reconnection during a tokamak major disruption

    International Nuclear Information System (INIS)

    Goetz, J.A.

    1990-09-01

    Magnetic reconnection has long been considered to be the cause of sawtooth oscillations and major disruptions in tokamak experiments. Experimental confirmation of reconnection models has been hampered by the difficulty of direct measurement of reconnection, which would involve tracing field lines for many transits around the tokamak. Perhaps the most stringent test of reconnection in a tokamak involves measurement of the safety factor q. Reconnection arising from a single helical disturbance with mode numbers m and n should raise q to m/n everywhere inside of the original resonant surface. Total reconnection should also flatten the temperature and current density profiles inside of this surface. Disruptive instabilities have been studied in the Tokapole 2, a poloidal divertor tokamak. When Tokapole 2 is operated in the material limiter configuration, a major disruption results in current termination as in most tokamaks. However, when operated in the magnetic limiter configuration current termination is suppressed and major disruptions appear as giant sawtooth oscillations. The objective of this thesis is to determine if total reconnection is occurring during major disruptions. To accomplish this goal, the poloidal magnetic field has been directly measured in Tokapole 2 with internal magnetic coils. A full two-dimensional measurement over the central current channel has been done. From these measurements, the poloidal magnetic flux function is obtained and the magnetic surfaces are plotted. The flux-surface-averaged safety factor is obtained by integrating the local magnetic field line pitch over the experimentally obtained magnetic surface

  20. Experimental Investigation of the Neutral sheet Profile During Magnetic Reconnection

    International Nuclear Information System (INIS)

    Trintchouk, F.; Ji, H.; Yamada, M.; Kulsrud, R.; Hsu, S.; Carter, T.

    1999-01-01

    During magnetic reconnection, a ''neutral sheet'' current is induced, heating the plasma. The resultant plasma thermal pressure forms a stationary equilibrium with the opposing magnetic fields. The reconnection layer profile holds significant clues about the physical mechanisms which control reconnection. On the Magnetic Reconnection Experiment [M. Yamada et al., Phys. Plasmas 4, 1936 (1997)], a quasi steady-state and axisymmetric neutral sheet profile has been measured precisely using a magnetic probe array with spatial resolution equal to one quarter of the ion gyro-radius. It was found that the reconnecting field profile fits well with a Harris-type profile [E. G. Harris, Il Nuovo Cimento 23, 115 (1962)], B(x) approximately tanh(x/delta). This agreement is remarkable since the Harris theory does not take into account reconnection and associated electric fields and dissipation. An explanation for this agreement is presented. The sheet thickness delta is found to be approximately 0.4 times the ion skin depth, which agrees with a generalized Harris theory incorporating non-isothermal electron and ion temperatures and finite electric field. The detailed study of additional local features of the reconnection region is also presented

  1. MMS Encounters with Reconnection Diffusion Regions in the Earth's Magnetotail

    Science.gov (United States)

    Torbert, R. B.; Burch, J. L.; Argall, M. R.; Farrugia, C. J.; Alm, L.; Dors, I.; Payne, D.; Rogers, A. J.; Strangeway, R. J.; Phan, T.; Ergun, R.; Goodrich, K.; Lindqvist, P. A.; Khotyaintsev, Y. V.; Giles, B. L.; Rager, A. C.; Gershman, D. J.; Kletzing, C.

    2017-12-01

    The Magnetospheric Multiscale (MMS) fleet of four spacecraft traversed the Earth's magnetotail in May through August of 2017 with an apogee of 25 Re, and encountered diffusion regions characteristic of symmetric reconnection. This presentation will describe in-situ measurements of large electric fields, strong electron cross-tail and Hall currents, and electron velocity distributions (frequently crescent-shaped) that are commonly observed in these regions. Positive electromagnetic energy conversion is also typical. The characteristics of symmetric reconnection observations will be contrasted with those of asymmetric reconnection that MMS observed previously at the dayside magnetopause.

  2. Plasma Astrophysics, Part II Reconnection and Flares

    CERN Document Server

    Somov, Boris V

    2013-01-01

    This two-part book is devoted to classic fundamentals and current practices and perspectives of modern plasma astrophysics. This second part discusses the physics of magnetic reconnection and flares of electromagnetic origin in space plasmas in the solar system, single and double stars, relativistic objects, accretion disks and their coronae. More than 25% of the text is updated from the first edition, including the additions of new figures, equations and entire sections on topics such as topological triggers for solar flares and the magnetospheric physics problem. This book is aimed at professional researchers in astrophysics, but it will also be useful to graduate students in space sciences, geophysics, applied physics and mathematics, especially those seeking a unified view of plasma physics and fluid mechanics.

  3. Resistive instabilities and field line reconnection

    International Nuclear Information System (INIS)

    White, R.B.

    1980-05-01

    A review is given of the linear theory of reconnection for a plane current layer. The three basic modes are the Rippling Mode, the Gravitational Interchange Mode, and the Tearing Mode. A derivation is given of the magnetic field energy which provides the driving force for the tearing mode. The necessary concepts for the analysis of tearing modes in cylindrical geometry are introduced. The equations governing tearing mode evolution in a tokamak are expanded to lowest order in the inverse aspect ratio. The tearing mode in a toroidal device is closely related to the ideal magnetohydrodynamic kink mode, and this relationship is stressed in the derivations of the linear growth rates for modes with poloidal model number m > 2 and for the quite different m = 1 mode. The nonlinear theory of tearing mode development and the implications of this theory for the understanding of toroidal magnetic confinement devices is reviewed

  4. Density and spin modes in imbalanced normal Fermi gases from collisionless to hydrodynamic regime

    Science.gov (United States)

    Narushima, Masato; Watabe, Shohei; Nikuni, Tetsuro

    2018-03-01

    We study the mass- and population-imbalance effect on density (in-phase) and spin (out-of-phase) collective modes in a two-component normal Fermi gas. By calculating the eigenmodes of the linearized Boltzmann equation as well as the density/spin dynamic structure factor, we show that mass- and population-imbalance effects offer a variety of collective mode crossover behaviors from collisionless to hydrodynamic regimes. The mass-imbalance effect shifts the crossover regime to the higher-temperature, and a significant peak of the spin dynamic structure factor emerges only in the collisionless regime. This is in contrast to the case of mass- and population-balanced normal Fermi gases, where the spin dynamic response is always absent. Although the population-imbalance effect does not shift the crossover regime, the spin dynamic structure factor survives both in the collisionless and hydrodynamic regimes.

  5. Fast Magnetic Reconnection: Bridging Laboratory and Space Plasma Physics

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Amitava [University New Hampshire- Durham

    2012-02-16

    Recent developments in experimental and theoretical studies of magnetic reconnection hold promise for providing solutions to outstanding problems in laboratory and space plasma physics. Examples include sawtooth crashes in tokamaks, substorms in the Earth’s Magnetosphere, eruptive solar flares, and more recently, fast reconnection in laser-produced high energy density plasmas. In each of these examples, a common and long-standing challenge has been to explain why fast reconnection proceeds rapidly from a relatively quiescent state. In this talk, we demonstrate the advantages of viewing these problems and their solutions from a common perspective. We focus on some recent, surprising discoveries regarding the role of secondary plasmoid instabilities of thin current sheets. Nonlinearly, these instabilities lead to fast reconnection rates that are very weakly dependent on the Lundquist number of the plasma.

  6. From flares to nanoflares: magnetic reconnection on the Sun

    Science.gov (United States)

    Cargill, Peter

    2013-06-01

    Peter Cargill discusses the history and current thinking on magnetic reconnection, in the first James Dungey Lecture, which was given in the presence of Jim Dungey himself at the RAS on 11 January 2013.

  7. Experimental investigation of the trigger problem in magnetic reconnection

    International Nuclear Information System (INIS)

    Katz, Noam; Egedal, Jan; Fox, Will; Le, Ari; Vrublevskis, Arturs; Bonde, Jeff

    2011-01-01

    Magnetic reconnection releases magnetic energy not only in steady state, but also in time-dependent and often explosive events. Here, we investigate the trigger mechanism for this explosive release by using a toroidal experiment in the strong guide-field regime. We observe spontaneous reconnection events with exponentially growing reconnection rates, and we characterize the full 3D dynamics of these events using multiple internal probes. The reconnection is asymmetric: it begins at one toroidal location and propagates around in both directions. The spontaneous onset is facilitated by an interaction between the x-line current channel and a global mode, which appears in the electrostatic potential. It is this mode which breaks axisymmetry and enables a localized decrease in x-line current. We apply a simple model - which relies on ion polarization currents for current continuity - to reproduce the exponential growth and compute the growth rate. The result agrees well with the experimental growth rate.

  8. Electron-scale measurements of magnetic reconnection in space

    Science.gov (United States)

    Burch, J. L.; Torbert, R. B.; Phan, T. D.; Chen, L.-J.; Moore, T. E.; Ergun, R. E.; Eastwood, J. P.; Gershman, D. J.; Cassak, P. A.; Argall, M. R.; Wang, S.; Hesse, M.; Pollock, C. J.; Giles, B. L.; Nakamura, R.; Mauk, B. H.; Fuselier, S. A.; Russell, C. T.; Strangeway, R. J.; Drake, J. F.; Shay, M. A.; Khotyaintsev, Yu. V.; Lindqvist, P.-A.; Marklund, G.; Wilder, F. D.; Young, D. T.; Torkar, K.; Goldstein, J.; Dorelli, J. C.; Avanov, L. A.; Oka, M.; Baker, D. N.; Jaynes, A. N.; Goodrich, K. A.; Cohen, I. J.; Turner, D. L.; Fennell, J. F.; Blake, J. B.; Clemmons, J.; Goldman, M.; Newman, D.; Petrinec, S. M.; Trattner, K. J.; Lavraud, B.; Reiff, P. H.; Baumjohann, W.; Magnes, W.; Steller, M.; Lewis, W.; Saito, Y.; Coffey, V.; Chandler, M.

    2016-06-01

    Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy is converted into heat and kinetic energy of charged particles. Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth's magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field. We have (i) observed the conversion of magnetic energy to particle energy; (ii) measured the electric field and current, which together cause the dissipation of magnetic energy; and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region.

  9. Forced Hall magnetic reconnection: Parametric variation of the 'Newton Challenge'

    International Nuclear Information System (INIS)

    Huba, J.D.

    2006-01-01

    A parametric study of forced magnetic reconnection using a 2D Hall magnetohydrodynamic (MHD) code based on the 'Newton Challenge' is presented. The 'Newton Challenge' defined a magnetic reconnection problem in which reconnection was initiated by a spatially and temporally dependent inflow velocity on the upstream boundary. In this study the magnitude and time dependence of the inflow velocity are varied, as well as the length of the system and the boundary conditions. The general conclusion is that reconnection occurs sooner and faster for stronger impulsive drives (e.g., larger inflow velocities and longer time scales). The results are fairly insensitive to system length. Finally, the Hall MHD results are compared to results from a particle-in-cell simulation study

  10. MESSENGER observations of magnetic reconnection in Mercury's magnetosphere.

    Science.gov (United States)

    Slavin, James A; Acuña, Mario H; Anderson, Brian J; Baker, Daniel N; Benna, Mehdi; Boardsen, Scott A; Gloeckler, George; Gold, Robert E; Ho, George C; Korth, Haje; Krimigis, Stamatios M; McNutt, Ralph L; Raines, Jim M; Sarantos, Menelaos; Schriver, David; Solomon, Sean C; Trávnícek, Pavel; Zurbuchen, Thomas H

    2009-05-01

    Solar wind energy transfer to planetary magnetospheres and ionospheres is controlled by magnetic reconnection, a process that determines the degree of connectivity between the interplanetary magnetic field (IMF) and a planet's magnetic field. During MESSENGER's second flyby of Mercury, a steady southward IMF was observed and the magnetopause was threaded by a strong magnetic field, indicating a reconnection rate ~10 times that typical at Earth. Moreover, a large flux transfer event was observed in the magnetosheath, and a plasmoid and multiple traveling compression regions were observed in Mercury's magnetotail, all products of reconnection. These observations indicate that Mercury's magnetosphere is much more responsive to IMF direction and dominated by the effects of reconnection than that of Earth or the other magnetized planets.

  11. Integrating Kinetic Effects into Global Models for Reconnection

    Science.gov (United States)

    Antiochos, S. K.

    2012-01-01

    Magnetic reconnection is the most striking example of how the coupling between global and kinetic scales can lead to fast energy release. Explosive solar activity, such as coronal mass ejections and flares for example, is widely believed to be due to the release of magnetic energy stored on global scales by magnetic reconnection operating on kinetic scales. Understanding how processes couple across spatial scales is one of the most difficult challenges in all of physics, and is undoubtedly the main obstacle to developing predictive models for the Sun's activity. Consequently, the NASA Living With a Star Program selected a Focused Science Team to attack the problem of cross-scale coupling in reconnection. In this talk I will present some of the results of the Team and review our latest theories and methods for modeling the global-local coupling in solar reconnection.

  12. Total magnetic reconnection during a tokamak major disruption

    International Nuclear Information System (INIS)

    Goetz, J.A.; Dexter, R.N.; Prager, S.C.

    1990-07-01

    The safety factor within a tokamak plasma has been measured during a major disruption. During the disruption, the central safety factor jumps from below one to above one, while the total current is unchanged. This implies that total reconnection has occurred. This observation is in contract to the absence of total reconnection observed during a sawtooth oscillation in the same device. 11 refs., 6 figs

  13. Particle Acceleration Due to Coronal Non-null Magnetic Reconnection

    Science.gov (United States)

    Threlfall, James; Neukirch, Thomas; Parnell, Clare Elizabeth

    2017-03-01

    Various topological features, for example magnetic null points and separators, have been inferred as likely sites of magnetic reconnection and particle acceleration in the solar atmosphere. In fact, magnetic reconnection is not constrained to solely take place at or near such topological features and may also take place in the absence of such features. Studies of particle acceleration using non-topological reconnection experiments embedded in the solar atmosphere are uncommon. We aim to investigate and characterise particle behaviour in a model of magnetic reconnection which causes an arcade of solar coronal magnetic field to twist and form an erupting flux rope, crucially in the absence of any common topological features where reconnection is often thought to occur. We use a numerical scheme that evolves the gyro-averaged orbit equations of single electrons and protons in time and space, and simulate the gyromotion of particles in a fully analytical global field model. We observe and discuss how the magnetic and electric fields of the model and the initial conditions of each orbit may lead to acceleration of protons and electrons up to 2 MeV in energy (depending on model parameters). We describe the morphology of time-dependent acceleration and impact sites for each particle species and compare our findings to those recovered by topologically based studies of three-dimensional (3D) reconnection and particle acceleration. We also broadly compare aspects of our findings to general observational features typically seen during two-ribbon flare events.

  14. Kinetic features of magnetic reconnection in a plasmoid chain

    Science.gov (United States)

    Markidis, S.; Henri, P.; Lapenta, G.; Goldman, M. V.; Newman, D.; Eriksson, S.

    2012-04-01

    The kinetic features of plasmoid chain formation and evolution are investigated by two dimensional Particle-in-Cell simulations. Magnetic reconnection is initiated in multiple X points by the tearing instability. Plasmoids form and grow in size by continuously coalescing. Each chain plasmoid exhibits a strong out-of plane core magnetic field and an out-of-plane electron current that drives the coalescing process. The disappearance of the X points in the coalescence process are due to anti-reconnection, a magnetic reconnection where the plasma inflow and outflow are reversed with respect to the original reconnection flow pattern. Anti-reconnection is characterized by the Hall magnetic field quadrupole signature. Intense electric fields develop mainly in-plane normally to the separatrices and drive the ion dynamics in the plasmoids. Several bipolar electric field structures are localized along the separatrices. The analysis of the electron distribution function and phase space reveals the presence of counter-streaming electron beams and phase space electron holes along the reconnection separatrices.

  15. ASYMMETRIC MAGNETIC RECONNECTION IN WEAKLY IONIZED CHROMOSPHERIC PLASMAS

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Nicholas A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lukin, Vyacheslav S., E-mail: namurphy@cfa.harvard.edu [National Science Foundation, 4201 Wilson Boulevard, Arlington, VA 22230 (United States)

    2015-06-01

    Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection, the current sheet thins to the scale of the neutral–ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak-field (high-density) upstream region into the strong-field upstream region results from a neutral pressure gradient. Consequently, neutrals dragged along with the outflow are more likely to originate from the weak-field region. The Hall effect leads to the development of a characteristic quadrupole magnetic field modified by asymmetry, but the X-point geometry expected during Hall reconnection does not occur. All simulations show the development of plasmoids after an initial laminar phase.

  16. Frequently Occurring Reconnection Jets from Sunspot Light Bridges

    Science.gov (United States)

    Tian, Hui; Yurchyshyn, Vasyl; Peter, Hardi; Solanki, Sami K.; Young, Peter R.; Ni, Lei; Cao, Wenda; Ji, Kaifan; Zhu, Yingjie; Zhang, Jingwen; Samanta, Tanmoy; Song, Yongliang; He, Jiansen; Wang, Linghua; Chen, Yajie

    2018-02-01

    Solid evidence of magnetic reconnection is rarely reported within sunspots, the darkest regions with the strongest magnetic fields and lowest temperatures in the solar atmosphere. Using the world’s largest solar telescope, the 1.6 m Goode Solar Telescope, we detect prevalent reconnection through frequently occurring fine-scale jets in the Hα line wings at light bridges, the bright lanes that may divide the dark sunspot core into multiple parts. Many jets have an inverted Y-shape, shown by models to be typical of reconnection in a unipolar field environment. Simultaneous spectral imaging data from the Interface Region Imaging Spectrograph show that the reconnection drives bidirectional flows up to 200 km s‑1, and that the weakly ionized plasma is heated by at least an order of magnitude up to ∼80,000 K. Such highly dynamic reconnection jets and efficient heating should be properly accounted for in future modeling efforts of sunspots. Our observations also reveal that the surge-like activity previously reported above light bridges in some chromospheric passbands such as the Hα core has two components: the ever-present short surges likely to be related to the upward leakage of magnetoacoustic waves from the photosphere, and the occasionally occurring long and fast surges that are obviously caused by the intermittent reconnection jets.

  17. MAVEN observations of magnetic reconnection in the Martian magnetotail

    Science.gov (United States)

    Harada, Y.; Halekas, J. S.; McFadden, J. P.; Mitchell, D. L.; Mazelle, C. X.; Connerney, J. E. P.; Espley, J. R.; Larson, D. E.; Brain, D. A.; Andersson, L.; DiBraccio, G. A.; Collinson, G.; Livi, R.; Hara, T.; Ruhunusiri, S.; Jakosky, B. M.

    2015-12-01

    Magnetic reconnection is a fundamental process that changes magnetic field topology and converts magnetic energy into particle energy. Although reconnection may play a key role in controlling ion escape processes at Mars, the fundamental properties of local physics and global dynamics of magnetic reconnection in the Martian environment remain unclear owing to the lack of simultaneous measurements of ions, electrons, and magnetic fields by modern instrumentation. Here we present comprehensive MAVEN observations of reconnection signatures in the near-Mars magnetotail. The observed reconnection signatures include (i) Marsward bulk flows of H+, O+, and O2+ ions, (ii) counterstreaming ion beams along the current sheet normal direction, (iii) Hall magnetic fields, and (iv) trapped electrons with two-sided loss cones. The measured velocity distribution functions of different ion species exhibit mass-dependent characteristics which are qualitatively consistent with previous multi-species kinetic simulations and terrestrial tail observations. The MAVEN observations demonstrate that the near-Mars magnetotail provides a unique environment for studying multi-ion reconnection.

  18. Mechanism of Radial Redistribution of Energetic Trapped Ions Due to m=2/n=1 Internal Reconnection in Joint European Torus Shear Optimized Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    N.N. Gorelenkov; A. Gondhalekar; A.A. Korotkov; S.E. Sharapov; D. Testa; and Contributors to the EFDA-JET Workprogramme

    2002-01-18

    Internal radial redistribution of MeV energy ICRF-driven hydrogen minority ions was inferred from neutral particle analyzer measurements during large amplitude MHD activity leading to internal reconnection in Shear Optimized plasmas in the Joint European Torus (JET). A theory is developed for energetic ion redistribution during a reconnection driven by an m=2/n=1 internal kink mode. Plasma motion during reconnection generates an electric field which can change the energy and radial position of the energetic ions. The magnitude of ion energy change depends on the value of the safety factor at the plasma core from which the energetic ions are redistributed. A relation is found for corresponding change in canonical momentum. P(subscript phi), which leads to radial displacement of the ions. The model yields distinctive new features of energetic ion redistribution under such conditions. Predicted characteristics of ion redistribution are compared with the NPA measurements, and good correlation is found. Sometimes fast ions were transported to the plasma edge due to interaction with a long-lived magnetic island which developed after the reconnection and had chirping frequency in the laboratory frame. Convection of resonant ions trapped in a radially moving phase-space island is modeled to understand the physics of such events.

  19. Nonlocal collisionless and collisional electron transport in low temperature plasmas

    Science.gov (United States)

    Kaganovich, Igor

    2009-10-01

    The purpose of the talk is to describe recent advances in nonlocal electron kinetics in low-pressure plasmas. A distinctive property of partially ionized plasmas is that such plasmas are always in a non-equilibrium state: the electrons are not in thermal equilibrium with the neutral species and ions, and the electrons are also not in thermodynamic equilibrium within their own ensemble, which results in a significant departure of the electron velocity distribution function from a Maxwellian. These non-equilibrium conditions provide considerable freedom to choose optimal plasma parameters for applications, which make gas discharge plasmas remarkable tools for a variety of plasma applications, including plasma processing, discharge lighting, plasma propulsion, particle beam sources, and nanotechnology. Typical phenomena in such discharges include nonlocal electron kinetics, nonlocal electrodynamics with collisionless electron heating, and nonlinear processes in the sheaths and in the bounded plasmas. Significant progress in understanding the interaction of electromagnetic fields with real bounded plasma created by this field and the resulting changes in the structure of the applied electromagnetic field has been one of the major achievements of the last decade in this area of research [1-3]. We show on specific examples that this progress was made possible by synergy between full scale particle-in-cell simulations, analytical models, and experiments. In collaboration with Y. Raitses, A.V. Khrabrov, Princeton Plasma Physics Laboratory, Princeton, NJ, USA; V.I. Demidov, UES, Inc., 4401 Dayton-Xenia Rd., Beavercreek, OH 45322, USA and AFRL, Wright-Patterson AFB, OH 45433, USA; and D. Sydorenko, University of Alberta, Edmonton, Canada. [4pt] [1] D. Sydorenko, A. Smolyakov, I. Kaganovich, and Y. Raitses, IEEE Trans. Plasma Science 34, 895 (2006); Phys. Plasmas 13, 014501 (2006); 14 013508 (2007); 15, 053506 (2008). [0pt] [2] I. D. Kaganovich, Y. Raitses, D. Sydorenko, and

  20. High-speed photography of a 'switch-on' collisionless shock

    International Nuclear Information System (INIS)

    El-Khalafawy, T.A.; El-Nicklawy, M.M.; Bashara, A.B.; El-Masry, M.A.; Rudnev, N.J.

    1975-01-01

    The paper presents the results of the investigation of a 'switch-on' shock profile and the measurement of the wave velocity in the collisionless regime employing high-speed photography. Data for the electron temperature (Tsub(e)) ahead of and behind the wave front are presented here, and a Table with estimated and measured characteristic physical quantities. (author)

  1. Investigation of the stability of collision-less spherically symmetric systems

    Energy Technology Data Exchange (ETDEWEB)

    Polyachenko, V.L.; Shukhman, I.G. (AN SSSR, Leningrad. Inst. Teoreticheskoj Astronomii)

    The matrix equation star is suggested for investigating the large- scale stability of general spherical collisionless star systems. The equation derived is used for a stability analysis of Idlis one-parametric series of distribution functions. It is shown that the stability condition restricts strongly the permissible degree of anisotropy of the stellar velocity distribution.

  2. DICE/ColDICE: 6D collisionless phase space hydrodynamics using a lagrangian tesselation

    Science.gov (United States)

    Sousbie, Thierry

    2018-01-01

    DICE is a C++ template library designed to solve collisionless fluid dynamics in 6D phase space using massively parallel supercomputers via an hybrid OpenMP/MPI parallelization. ColDICE, based on DICE, implements a cosmological and physical VLASOV-POISSON solver for cold systems such as dark matter (CDM) dynamics.

  3. Self-consistency constraints on turbulent magnetic transport and relaxation in collisionless plasma

    International Nuclear Information System (INIS)

    Terry, P.W.; Diamond, P.H.; Hahm, T.S.

    1985-10-01

    Novel constraints on collisionless relaxation and transport in drift-Alfven turbulence are reported. These constraints arise due to the consideration of mode coupling and incoherent fluctuations and the proper application of self-consistency conditions. The result that electrostatic fluctuations alone regulate transport in drift-Alfven turbulence follows directly. Quasilinear transport predictions are discussed in light of these constraints

  4. Saturation regime of the collisionless drift instability in a hydrogen plasma column

    International Nuclear Information System (INIS)

    Boissier, R.

    1982-09-01

    The saturation regime of the collisionless drift instability is observed in a steady state hydrogen column. The steady state parameters are observed to relax around the average values. A quasilinear model is proposed to describe the dynamics of wave growth and density gradient decay

  5. Witnessing a Large-scale Slipping Magnetic Reconnection along a Dimming Channel during a Solar Flare

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Ju; Lee, Jeongwoo; Xu, Yan; Liu, Chang; Wang, Haimin [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102-1982 (United States); Liu, Rui [CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences, University of Science and Technology of China, Hefei 230026 (China); Cheung, Mark C. M. [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304 (United States); Zhu, Chunming, E-mail: ju.jing@njit.edu [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

    2017-06-20

    We report the intriguing large-scale dynamic phenomena associated with the M6.5 flare (SOL2015-06-22T18:23) in NOAA active region 12371, observed by RHESSI , Fermi , and the Atmospheric Image Assembly (AIA) and Magnetic Imager (HMI) on the Solar Dynamics Observatory ( SDO ). The most interesting feature of this event is a third ribbon (R3) arising in the decay phase, propagating along a dimming channel (seen in EUV passbands) toward a neighboring sunspot. The propagation of R3 occurs in the presence of hard X-ray footpoint emission and is broadly visible at temperatures from 0.6 MK to over 10 MK through the differential emission measure analysis. The coronal loops then undergo an apparent slipping motion following the same path of R3, after a ∼80 minute delay. To understand the underlying physics, we investigate the magnetic configuration and the thermal structure of the flaring region. Our results are in favor of a slipping-type reconnection followed by the thermodynamic evolution of coronal loops. In comparison with those previously reported slipping reconnection events, this one proceeds across a particularly long distance (∼60 Mm) over a long period of time (∼50 minutes) and shows two clearly distinguished phases: the propagation of the footpoint brightening driven by nonthermal particle injection and the apparent slippage of loops governed by plasma heating and subsequent cooling.

  6. Observations of significant flux closure by dual lobe reconnection

    Directory of Open Access Journals (Sweden)

    S. M. Imber

    2007-07-01

    Full Text Available We present an interval of dual lobe reconnection during which interplanetary magnetic field lines are captured by the magnetosphere by reconnecting at high latitudes in both the Northern and the Southern Hemispheres. This event was identified using measurements of the ionospheric convection flow and observations of the aurora using the SuperDARN radars and the IMAGE spacecraft. A cusp spot, characteristic of northward IMF, is clearly visible for a 30 min period enabling the ionospheric footprint of the Northern Hemisphere merging gap to be accurately determined. During the interval a strong burst of sunward flow across the dayside open/closed field line boundary (OCB is observed, which we interpret as the reconfiguration of the magnetosphere following a burst of reconnection. Noon-midnight and dawn-dusk keograms of the aurora show that the polar cap shrinks during the interval indicating that a large amount of flux was closed by the reconnection. Using the SuperDARN potential maps it is possible to calculate that the amount of flux closed during the interval is 0.13 GWb which represents approximately 10% of the pre-existing polar cap. The number of ions captured by the burst of dual lobe reconnection was calculated to be ~2.2×1031, more than sufficient to populate a cold, dense plasma sheet. That a dense plasma sheet was not subsequently observed is discussed in terms of subsequent changes in the IMF.

  7. The auroral and ionospheric flow signatures of dual lobe reconnection

    Directory of Open Access Journals (Sweden)

    S. M. Imber

    2006-11-01

    Full Text Available We present the first substantial evidence for the occurrence of dual lobe reconnection from ionospheric flows and auroral signatures. The process of dual lobe reconnection refers to an interplanetary magnetic field line reconnecting with lobe field lines in both the northern and southern hemispheres. Two bursts of sunward plasma flow across the noon portion of the open/closed field line boundary (OCB, indicating magnetic flux closure at the dayside, were observed in SuperDARN radar data during a period of strongly northward IMF. The OCB is identified from spacecraft, radar backscatter, and auroral observations. In order for dual lobe reconnection to take place, we estimate that the interplanetary magnetic field clock angle must be within ±10° of zero (North. The total flux crossing the OCB during each burst is small (1.8% and 0.6% of the flux contained within the polar cap for the two flows. A brightening of the noon portion of the northern auroral oval was observed as the clock angle passed through zero, and is thought to be due to enhanced precipitating particle fluxes due to the occurrence of reconnection at two locations along the field line. The number of solar wind protons captured by the flux closure process was estimated to be ~2.5×1030 (4 tonnes by mass, sufficient to populate the cold, dense plasma sheet observed following this interval.

  8. Flux Rope Acceleration and Enhanced Magnetic Reconnection Rate

    International Nuclear Information System (INIS)

    C.Z. Cheng; Y. Ren; G.S. Choe; Y.-J. Moon

    2003-01-01

    A physical mechanism of flares, in particular for the flare rise phase, has emerged from our 2-1/2-dimensional resistive MHD simulations. The dynamical evolution of current-sheet formation and magnetic reconnection and flux-rope acceleration subject to continuous, slow increase of magnetic shear in the arcade are studied by employing a non-uniform anomalous resistivity in the reconnecting current sheet under gravity. The simulation results directly relate the flux rope's accelerated rising motion with an enhanced magnetic reconnection rate and thus an enhanced reconnection electric field in the current sheet during the flare rise phase. The simulation results provide good quantitative agreements with observations of the acceleration of flux rope, which manifests in the form of SXR ejecta or erupting filament or CMEs, in the low corona. Moreover, for the X-class flare events studied in this paper the peak reconnection electric field is about O(10 2 V/m) or larger, enough to accelerate p articles to over 100 keV in a field-aligned distance of 10 km. Nonthermal electrons thus generated can produce hard X-rays, consistent with impulsive HXR emission observed during the flare rise phase

  9. Tripolar electric field Structure in guide field magnetic reconnection

    Science.gov (United States)

    Fu, Song; Huang, Shiyong; Zhou, Meng; Ni, Binbin; Deng, Xiaohua

    2018-03-01

    It has been shown that the guide field substantially modifies the structure of the reconnection layer. For instance, the Hall magnetic and electric fields are distorted in guide field reconnection compared to reconnection without guide fields (i.e., anti-parallel reconnection). In this paper, we performed 2.5-D electromagnetic full particle simulation to study the electric field structures in magnetic reconnection under different initial guide fields (Bg). Once the amplitude of a guide field exceeds 0.3 times the asymptotic magnetic field B0, the traditional bipolar Hall electric field is clearly replaced by a tripolar electric field, which consists of a newly emerged electric field and the bipolar Hall electric field. The newly emerged electric field is a convective electric field about one ion inertial length away from the neutral sheet. It arises from the disappearance of the Hall electric field due to the substantial modification of the magnetic field and electric current by the imposed guide field. The peak magnitude of this new electric field increases linearly with the increment of guide field strength. Possible applications of these results to space observations are also discussed.

  10. Ellerman bombs and UV bursts: reconnection at different atmospheric layers?

    Science.gov (United States)

    Hansteen, V. H.; Ortiz-Carbonell, A. N.; Rouppe van der Voort, L.

    2017-12-01

    The emergence of magnetic flux through the photosphere and into the outer solar atmosphere produces, amongst many other phenomena, the appearance of Ellerman bombs (EBs) in the photosphere. EBs are observed in the wings of H(alpha) and are highly likely to be due to reconnection in the photosphere, below the chromospheric canopy. However, signs of the reconnection process are also observed in several other spectral lines, typical of the chromosphere or transition region. An example are the UV bursts observed in the transition region lines of Si IV. In this work we analyze high cadence coordinated observations between the 1-m Swedish Solar Telescope and the IRIS spacecraft in order to study the possible relationship between reconnection events at different layers in the atmosphere, and in particular, the timing history between them. High cadence, high resolution H-alpha images from the SST provide us with the positions, timings and trajectories of Ellerman bombs in an emerging flux region. Simultaneous co-aligned IRIS slit-jaw images at 1400 and 1330 A and detailed Si IV spectra from the fast spectrograph raster allow us to study the transition region counterparts of those photospheric Ellerman bombs. Our main goal is to study whether there is a temporal relationship between the appearance of an EB and the appearance of a UV burst. Eventually we would like to investigate whether reconnection happens at discrete heights, or as a reconnection sheet spanning several layers at the same time.

  11. Structure of reconnection boundary layers in incompressible MHD

    International Nuclear Information System (INIS)

    Sonnerup, B.U.Oe.; Wang, D.J.

    1987-01-01

    The incompressible MHD equations with nonvanishing viscosity and resistivity are simplified by use of the boundary layer approximation to describe the flow and magnetic field in the exit flow regions of magnetic field reconnection configurations when the reconnection rate is small. The conditions are derived under which self-similar solutions exist of the resulting boundary layer equations. For the case of zero viscosity and resistivity, the equations describing such self-similar layers are then solved in terms of quadratures, and the resulting flow and field configurations are described. Symmetric solutions, relevant, for example, to reconnection in the geomagnetic tail, as well as asymmetric solutions, relevant to reconnection at the earth's magnetopause, are found to exist. The nature of the external solutions to which the boundary layer solutions should be matched is discussed briefly, but the actual matching, which is to occur at Alfven-wave characteristic curves in the boundary layer solutions, is not carried out. Finally, it is argued that the solutions obtained may also be used to describe the structure of the intense vortex layers observed to occur at magnetic separatrices in computer simulations and in certain analytical models of the reconnection process

  12. Ion-Scale Structure in Mercury's Magnetopause Reconnection Diffusion Region

    Science.gov (United States)

    Gershman, Daniel J.; Dorelli, John C.; DiBraccio, Gina A.; Raines, Jim M.; Slavin, James A.; Poh, Gangkai; Zurbuchen, Thomas H.

    2016-01-01

    The strength and time dependence of the electric field in a magnetopause diffusion region relate to the rate of magnetic reconnection between the solar wind and a planetary magnetic field. Here we use approximately 150 milliseconds measurements of energetic electrons from the Mercury Surface, Space Environment, GEochemistry, and Ranging (MESSENGER) spacecraft observed over Mercury's dayside polar cap boundary (PCB) to infer such small-scale changes in magnetic topology and reconnection rates. We provide the first direct measurement of open magnetic topology in flux transfer events at Mercury, structures thought to account for a significant portion of the open magnetic flux transport throughout the magnetosphere. In addition, variations in PCB latitude likely correspond to intermittent bursts of approximately 0.3 to 3 millivolts per meter reconnection electric fields separated by approximately 5 to10 seconds, resulting in average and peak normalized dayside reconnection rates of approximately 0.02 and approximately 0.2, respectively. These data demonstrate that structure in the magnetopause diffusion region at Mercury occurs at the smallest ion scales relevant to reconnection physics.

  13. Limiting velocity of reconnection in a current layer

    International Nuclear Information System (INIS)

    Podgornyj, A.N.; Syrovatskij, S.I.

    1981-01-01

    Formation of a plasma current layer from a strong perturbation wave with the Mach magnetic number Msub(a)=1 is investigated numerically within the framework of magnetic hydrodynamics. It is shown that velocity of plasma flowing into the layer is established as small one as compared with the Alfven velocity. At the current layer boundary the Mach magnetic number Msub(a, c)=0.14-0.2. A great decrease in plasma velocity to the current layer results from the counterpressure of a magnetic field, intensity of which near the layer increases due to the storage of magnetic force lines which do not yet reconnect. Calculational results demonstrate the existence of limiting velocity of magnetic reconnection constituting tenth shares of the Mach magnetic number. Influence of this phenomenon on a character of reconnection in the Earth magnetosphere is discussed

  14. Physical conditions in the reconnection layer in pulsar magnetospheres

    Energy Technology Data Exchange (ETDEWEB)

    Uzdensky, Dmitri A. [Center for Integrated Plasma Studies, Physics Department, University of Colorado, UCB 390, Boulder, CO 80309-0390 (United States); Spitkovsky, Anatoly, E-mail: uzdensky@colorado.edu, E-mail: anatoly@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2014-01-01

    The magnetosphere of a rotating pulsar naturally develops a current sheet (CS) beyond the light cylinder (LC). Magnetic reconnection in this CS inevitably dissipates a nontrivial fraction of the pulsar spin-down power within a few LC radii. We develop a basic physical picture of reconnection in this environment and discuss its implications for the observed pulsed gamma-ray emission. We argue that reconnection proceeds in the plasmoid-dominated regime, via a hierarchical chain of multiple secondary islands/flux ropes. The inter-plasmoid reconnection layers are subject to strong synchrotron cooling, leading to significant plasma compression. Using the conditions of pressure balance across these current layers, the balance between the heating by magnetic energy dissipation and synchrotron cooling, and Ampere's law, we obtain simple estimates for key parameters of the layers—temperature, density, and layer thickness. In the comoving frame of the relativistic pulsar wind just outside of the equatorial CS, these basic parameters are uniquely determined by the strength of the reconnecting upstream magnetic field. For the case of the Crab pulsar, we find them to be of order 10 GeV, 10{sup 13} cm{sup –3}, and 10 cm, respectively. After accounting for the bulk Doppler boosting due to the pulsar wind, the synchrotron and inverse-Compton emission from the reconnecting CS can explain the observed pulsed high-energy (GeV) and very high energy (∼100 GeV) radiation, respectively. Also, we suggest that the rapid relative motions of the secondary plasmoids in the hierarchical chain may contribute to the production of the pulsar radio emission.

  15. The Three Dimensional Structure and Dynamics of Magnetotail Reconnection

    Science.gov (United States)

    Walker, Raymond; Lapenta, Giovanni; Liang, Haoming; El Alaoui, Mostafa; Berchem, Jean; Goldstein, Melvyn

    2017-04-01

    Magnetic reconnection is a fundamental process by which magnetic energy is dissipated and converted into particle energy. In the next few months the Magnetosphere Multi-Scale Mission (MMS) will provide high resolution observations of reconnection and its consequences in the magnetotail. Of high priority will be observations of the electron diffusion region (EDR) where the actual process of reconnection is thought to occur. In preparation for the MMS observations we have investigated tail reconnection in a realistic magnetospheric configuration by using a new approach that combines a global magnetohydrodynamic simulation of the solar wind, magnetosphere and ionosphere system with a large scale (30X12X12RE) implicit particle-in-cell (iPic3D) simulation (see Lapenta et al., 2016 Geophys. Res. Lett. 43, 515-524, doi:10.1002/2015GL066689 for a discussion of the technique). In particular we have investigated the three dimensional structure and dynamics of tail reconnection during a substorm on February 15, 2008. We found that just earthward of the reconnection site the tail becomes highly structured in the Y direction in the GSM coordinate system. The structures result from an instability associated with strong shear flows in the Y direction within the current sheet. In particular we found that the work done by the magnetic field J•E in the electron frame alternated between positive and negative although the net J•E was positive. We used several methods for identifying the EDR (non-gyrotropy, slippage, the non-ideal terms in OHM's law as well as J•E) and found that all gave false positive results in some regions of the tail. However all of the approaches gave positive results in some of the small structures with J•E positive. These putative EDRs extended ( 2di, >1di, 1di) in the X, Y and Z directions.

  16. Scaling of Sweet-Parker reconnection with secondary islands

    International Nuclear Information System (INIS)

    Cassak, P. A.; Shay, M. A.; Drake, J. F.

    2009-01-01

    Sweet-Parker (collisional) magnetic reconnection at high Lundquist number is modified by secondary islands. Daughton et al. [Phys. Rev. Lett. 103, 065004 (2009)] suggested the Sweet-Parker model governs the fragmented current sheet segments. If true, the reconnection rate would increase by the square root of the number of secondary islands. High Lundquist number resistive magnetohydrodynamic simulations are presented which agree, in a time-averaged sense, with the predicted scaling. This result may have important implications for energy storage before a solar eruption and its subsequent release.

  17. Turbulence in Three Dimensional Simulations of Magnetopause Reconnection

    Science.gov (United States)

    Drake, J. F.; Price, L.; Swisdak, M.; Burch, J. L.; Cassak, P.; Dahlin, J. T.; Ergun, R.

    2017-12-01

    We present two- and three-dimensional particle-in-cell simulations of the 16 October 2015 MMS magnetopause reconnection event. While the two-dimensional simulation is laminar, turbulence develops at both the x-line and along the magnetic separatrices in the three-dimensional simulation. This turbulence is electromagnetic in nature, is characterized by a wavevector k given by kρ e ˜(m_e/m_i)0.25 with ρ e the electron Larmor radius, and appears to have the ion pressure gradient as its source of free energy. Taken together, these results suggest the instability is a variant of the lower-hybrid drift instability. The turbulence produces electric field fluctuations in the out-of-plane direction (the direction of the reconnection electric field) with an amplitude of around ± 10 mV/m, which is much greater than the reconnection electric field of around 0.1 mV/m. Such large values of the out-of-plane electric field have been identified in the MMS data. The turbulence in the simulation controls the scale lengths of the density profile and current layers in asymmetric reconnection, driving them closer to √ {ρ eρ_i } than the ρ e or de scalings seen in 2D reconnection simulations, where de is the electron inertial length. The turbulence is strong enough to make the magnetic field around the reconnection island chaotic and produces both anomalous resistivity and anomalous viscosity. Each contribute significantly to breaking the frozen-in condition in the electron diffusion region. The crescent-shaped features in velocity space seen both in MMS observations and in two-dimensional simulations survive, even in the turbulent environment of the three-dimensional system. We compare and contrast these results to a three-dimensional simulation of the 8 December 2015 MMS magnetopause reconnection event in which the reconnecting and out-of-plane guide fields are comparable. LHDI is still present in this event, although its appearance is modified by the presence of the guide

  18. Endogenous magnetic reconnection and associated high energy plasma processes

    Science.gov (United States)

    Coppi, B.; Basu, B.

    2018-02-01

    An endogenous reconnection process involves a driving factor that lays inside the layer where a drastic change of magnetic field topology occurs. A process of this kind is shown to take place when an electron temperature gradient is present in a magnetically confined plasma and the evolving electron temperature fluctuations are anisotropic. The width of the reconnecting layer remains significant even when large macroscopic distances are considered. In view of the fact that there are plasmas in the Universe with considerable electron thermal energy contents this feature can be relied upon in order to produce generation or conversion of magnetic energy, high energy particle populations and momentum and angular momentum transport.

  19. Measurement of the Transverse Spitzer Resistivity during Collisional Magnetic Reconnection

    International Nuclear Information System (INIS)

    Trintchouk, F.; Yamada, M.; Ji, H.; Kulsrud, R.M.; Carter, T.A.

    2000-01-01

    Measurement of the transverse resistivity was carried out in a reconnecting current sheet where the mean free path for the Coulomb collision is smaller than the thickness of the sheet. In a collisional neutral sheet without a guide field, the transverse resistivity is directly related to the reconnection rate. A remarkable agreement is found between the measured resistivity and the classical value derived by L. Spitzer. In his calculation the transverse resistivity for the electrons is higher than the parallel resistivity by a factor of 1.96. The measured values have verified this theory to within 30% errors

  20. Dissipation in relativistic pair-plasma reconnection: revisited

    Science.gov (United States)

    Zenitani, Seiji

    2018-01-01

    Basic properties of relativistic magnetic reconnection in electron–positron pair plasmas are investigated by using a particle-in-cell (PIC) simulation. We first revisit a problem by Hesse and Zenitani (2007 Phys. Plasmas 14 112102), who examined the kinetic Ohm’s law across the X line. We formulate a relativistic Ohm’s law by decomposing the stress–energy tensor. Then, the role of the new term, called the heat-flow inertial term, is examined in the PIC simulation data. We further evaluate the energy balance in the reconnection system. These analyses demonstrate physically transparent ways to diagnose relativistic kinetic data.

  1. Electrostatic Turbulence and Anomalous Effects in Reconnection Diffusion Region

    Science.gov (United States)

    Khotyaintsev, Y. V.; Graham, D. B.; Norgren, C.; Vaivads, A.; Li, W.; Divin, A. V.; Andre, M.; Markidis, S.; Lindqvist, P. A.; Peng, I. B.; Argall, M. R.; Ergun, R.; Le Contel, O.; Magnes, W.; Russell, C. T.; Giles, B. L.; Torbert, R. B.; Burch, J. L.

    2017-12-01

    Magnetic reconnection is a fundamental process whereby microscopicplasma processes cause macroscopic changes in magnetic field topology,so that initially separated plasmas become magnetically connected.Waves can produce particle diffusion, and anomalous resistivity, aswell as heat the plasma and accelerate plasma particles, all of whichcan impact ongoing reconnection. We report electrostatic turbulencedeveloping within the diffusion region of asymmetric magnetopausereconnection using observations by the Magnetospheric Multiscalemission and large-scale particle-in-cell simulations, and characterizeanomalous effects and plasma heating within the diffusion region. Ourobservations demonstrate that electrostatic turbulence plays animportant role in the electron-scale physics of asymmetricreconnection.

  2. High-power laser experiments to study collisionless shock in counter-streaming plasmas

    Science.gov (United States)

    Sakawa, Youichi; Kuramitsu, Y.; Morita, T.; Aoki, H.; Tanji, H.; Ide, T.; Norimatsu, T.; Kato, T.; Waugh, J.; Gregory, C.; Woolsey, N.; Diziere, A.; Koenig, M.; Zhang, Y.; Liu, X.; Wang, S.; Dong, Q.; Li, Y.; Zhong, J.; Zhang, J.; Takabe, H.

    2010-11-01

    In this paper we investigate laboratory experiments to study collisionless shock generation in counter-streaming plasmas using Gekko XII HIPER laser system (352 nm (3φ), 500 ps, < 1015 W/cm2) at ILE, Osaka University. 60 μm thick CH double-plane targets with the separation of 4.5 mm were used. Beams were irradiated on the 1st CH plane, and an ablation plasma was formed. Plasma from the 2nd CH was created by radiation and/or plasma from the 1st CH. The plasmas and shocks were diagnosed transverse to the main laser propagation direction using shadowgraphy, interferometrym, and SOP, etc. Counter-streaming plasmas were produced, and shock waves were observed. A particle-in-cell simulation predicted generation of an electrostatic shock. We also investigate an experimental proposal to demonstrate the formation of collisionless shocks through the self-generated magnetic fields due to the beam-Weibel instability.

  3. Collisionless two-fluid theory of toroidal ηi stability

    International Nuclear Information System (INIS)

    Mondt, J.; Weiland, J.

    1989-01-01

    A collisionless two-fluid theory based on a fourteen-moment generalization of the 'double-adiabatic' equations is developed to lowest order in the Larmor radius parameter, and applied to derive the toroidal η i stability boundary for all values of the ratio of the density gradient scale length divided by the field curvature length. The present model is an improvement over existing collisional two-fluid models in view of the collisionless nature of the η i instability, while retaining the advantage over kinetic theory of the practability of mode-coupling simulations. The linear stability boundary, linear growth rate and real frequency agree fairly accurately with draft-kinetic theory

  4. Collisionless damping of dust-acoustic waves in a charge varying dusty plasma with nonextensive ions

    International Nuclear Information System (INIS)

    Amour, Rabia; Tribeche, Mouloud

    2014-01-01

    The charge variation induced nonlinear dust-acoustic wave damping in a charge varying dusty plasma with nonextensive ions is considered. It is shown that the collisionless damping due to dust charge fluctuation causes the nonlinear dust acoustic wave propagation to be described by a damped Korteweg-de Vries (dK-dV) equation the coefficients of which depend sensitively on the nonextensive parameter q. The damping term, solely due to the dust charge variation, is affected by the ion nonextensivity. For the sake of completeness, the possible effects of nonextensivity and collisionless damping on weakly nonlinear wave packets described by the dK-dV equation are succinctly outlined by deriving a nonlinear Schrödinger-like equation with a complex nonlinear coefficient

  5. Collisionless damping of dust-acoustic waves in a charge varying dusty plasma with nonextensive ions

    Energy Technology Data Exchange (ETDEWEB)

    Amour, Rabia; Tribeche, Mouloud [Faculty of Physics, Theoretical Physics Laboratory (TPL), Plasma Physics Group (PPG), University of Bab-Ezzouar, USTHB, B.P. 32, El Alia, Algiers 16111 (Algeria)

    2014-12-15

    The charge variation induced nonlinear dust-acoustic wave damping in a charge varying dusty plasma with nonextensive ions is considered. It is shown that the collisionless damping due to dust charge fluctuation causes the nonlinear dust acoustic wave propagation to be described by a damped Korteweg-de Vries (dK-dV) equation the coefficients of which depend sensitively on the nonextensive parameter q. The damping term, solely due to the dust charge variation, is affected by the ion nonextensivity. For the sake of completeness, the possible effects of nonextensivity and collisionless damping on weakly nonlinear wave packets described by the dK-dV equation are succinctly outlined by deriving a nonlinear Schrödinger-like equation with a complex nonlinear coefficient.

  6. Meander reconnection method determines restoration success for macroinvertebrate communities in a German lowland river

    DEFF Research Database (Denmark)

    Lorenz, Stefan; Leszinski, Marc; Graeber, Daniel

    2016-01-01

    Re-meandering of degraded rivers is a frequently implemented measure in river restoration. A simple solution is reconnection of old meanders; however, its success likely depends on the reconnection method. We conducted a field study to analyze the benefits of a fully reconnected (fully opened...... meander, blocked main channel) and a partially reconnected meander (opened downstream, pipe bypass from main channel upstream, still open main channel) for macroinvertebrate communities in a German lowland river. Immediately upon reconnection of the two meanders, habitat diversity and macroinvertebrates...

  7. Energy flux due to electromagnetic fluctuations during guide field magnetic reconnection

    International Nuclear Information System (INIS)

    Kuwahata, Akihiro; Inomoto, Michiaki; Ono, Yasushi; Yanai, Ryoma

    2016-01-01

    Large electromagnetic fluctuations inside the current sheet and large reconnection electric fields are observed during fast magnetic reconnection in the presence of a guide field. The fluctuations transport 2.5% of the dissipated magnetic energy from the reconnection region. Although the energy gains of the ions and electrons are approximately 60% and 12%, respectively, of the dissipated magnetic energy after the fast reconnection, the energy of fluctuations is not comparable to their energy gains. The fluctuations do not directly contribute to the energy conversion but might cause the fast reconnection leading to the rapid release of magnetic energy. (author)

  8. Solar wind energy and electric field transfer to the Earth's magnetosphere VIA magnetopause reconnection

    International Nuclear Information System (INIS)

    Gonzalez, W.D.; Gonzalez, A.L.C.

    1981-01-01

    Some general expressions for the convection and parallel electric fields as well as for the energy transfer, due to magnetopause reconnection, are derived using a nose-reconnection model that takes into account the presence of the clefts. For the case of equal geomagnetic and magnetosheath field amplitudes, the expression for the power dissipated by the convection electric field reduces to the substorm parameter e widely discussed in the recent literature. This result suggests that magnetopause reconnection is defined at the nose with a tilted reconnection line, but that the convection electric field is related only to the dawn-dusk component of the reconnection electric field, as defined at high latitudes

  9. Study of Local Reconnection Physics in a Laboratory Plasma

    International Nuclear Information System (INIS)

    Hantao Ji; Troy Carter; Scott Hsu; Masaaki Yamada

    2001-01-01

    A short review of physics results obtained in the Magnetic Reconnection Experiment (MRX) is given with an emphasis on the local features of magnetic reconnection in a controlled environment. Stable two-dimensional current sheets are formed and sustained by induction using two internal coils. The observed reconnection rates are found to be quantitatively consistent with a generalized Sweet-Parker model which incorporates compressibility, unbalanced upstream-downstream pressure, and the effective resistivity. The latter is significantly enhanced over its classical values in the low collisionality regime. Strong local ion heating is measured by an optical probe during the reconnection process, and at least half of the increased ion energy must be due to nonclassical processes, consistent with the resistivity enhancement. Characteristics of high-frequency electrostatic and electromagnetic fluctuations detected in the current sheet suggest presence of the lower-hybrid-drift-like waves with significant magnetic components. The detailed structures of the current sheet are measured and compared with Harris theory and two-fluid theory

  10. Electron Heating and Acceleration in a Reconnecting Magnetotail

    Science.gov (United States)

    El-Alaoui, M.; Zhou, M.; Lapenta, G.; Berchem, J.; Richard, R. L.; Schriver, D.; Walker, R. J.

    2017-12-01

    Electron heating and acceleration in the magnetotail have been investigated intensively. A major site for this process is the reconnection region. However, where and how the electrons are accelerated in a realistic three-dimensional X-line geometry is not fully understood. In this study, we employed a three-dimensional implicit particle-in-cell (iPIC3D) simulation and large-scale kinetic (LSK) simulation to address these problems. We modeled a magnetotail reconnection event observed by THEMIS in an iPIC3D simulation with initial and boundary conditions given by a global magnetohydrodynamic (MHD) simulation of Earth's magnetosphere. The iPIC3D simulation system includes the region of fast outflow emanating from the reconnection site that drives dipolarization fronts. We found that current sheet electrons exhibit elongated (cigar-shaped) velocity distributions with a higher parallel temperature. Using LSK we then followed millions of test electrons using the electromagnetic fields from iPIC3D. We found that magnetotail reconnection can generate power law spectra around the near-Earth X-line. A significant number of electrons with energies higher than 50 keV are produced. We identified several acceleration mechanisms at different locations that were responsible for energizing these electrons: non-adiabatic cross-tail drift, betatron and Fermi acceleration. Relative contributions to the energy gain of these high energy electrons from the different mechanisms will be discussed.

  11. Proxy and in-situ studies of dayside magnetopause reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Scurry, L.; Russell, C.T. [California Univ., Los Angeles, CA (United States). Inst. of Geophysics and Planetary Physics; Gosling, J.T. [Los Alamos National Lab., NM (United States)

    1992-12-01

    The functional dependence of magnetic reconnection on solar wind parameters is examined utilizing the am geomagnetic index and satellite observations at the magnetopause. Several parameters in the solar wind are found to control geomagnetic activity. Reconnection is found to be most efficient when the interplanetary magnetic field is southward, although some activity remains when the IMF is horizontal and slightly northward. The reconnection efficiency increases with the solar wind dynamic pressure but decreases when the Mach number is greater than 7.5. These results are compared with the functional dependencies found by correlating solar wind and magnetosheath measurements with observations of accelerated tows at the magnetopause. Accelerated tows are found to occur most often when the interplanetary magnetic field is directed southward. However, accelerated flows do occur when the IMF is horizontal and northward. Accelerated flows are also affected by the magnetosheath beta such that higher beta inhibits their occurrence. The location of accelerated tows indicates that reconnection occurs mainly at the subsolar point.

  12. Magnetic reconnection and precursor effect in coaxial discharge

    International Nuclear Information System (INIS)

    Masoud, M.M.; Soliman, H.M.; El-Khalafawy, T.A.

    1988-01-01

    A precursor pulse was observed ahead of the plasma sheath produced by a coaxial electrode discharge system. The velocity of the precursor pulse was 4x10 7 cmS -1 and the velocity of the plasma sheath was 6x10 6 cmS -1 . The precursor pulse was unaffected when an axial magnetic field of 6 K.G. was applied to the propagation chamber, while the plasma sheath velocity increased and downstream structure were changed. The precursor pulse was split, sometimes, into two or more peaks, had the same shape and structure of the original one. The rest gas was heated up to 20 e.V. when the precursor pulse was destructed. The precursor pulse propagation mechanism and parameters showed that it had a solitary wave structure and behaviour. A reversed magnetic field was detected, when the plasma sheath had diamagnetic properties, where magnetic reconnection took place. Magnetic reconnection was responsible for energy transfiguration and wave generation. This was due to acceleration mechanism of charged particles occurred by the induced electric field at the moment of magnetic reconnection. The detected induced electric field had a high field intensity and fast rise time pulse. Several instabilities were referred to magnetic reconnection and the precursor pulse observed was a result of such instabilities

  13. Magnetotail Reconnection and Flux Circulation: Jupiter and Saturn Compared

    Science.gov (United States)

    Jackman, C. M.; Vogt, M. F.; Slavin, J. A.; Cowley, S. W. H.; Boardsen, S. A.

    2011-01-01

    The Jovian magnetosphere has been visited by eight spacecraft, and the magnetometer data have been used to identify dozens of plasmoids and 250 field dipolarizations associated with magnetic reconnection in the tail [e.g. Vogt et al., 2010]. Since the arrival of the Cassini spacecraft at Saturn in 2004, the magnetometer instrument has also been used to identify reconnection signatures. The deepest magnetotail orbits were in 2006, and during this time 34 signatures of plasmoids were identified. In this study we compare the statistical properties of plasmoids at Jupiter and Saturn such as duration, size, location, and recurrence period. Such parameters can be influenced by many factors, including the different Dungey cycle timescales and cross-magnetospheric potential drops at the two planets. We present superposed epoch analyses of plasmoids at the two planets to determine their average properties and to infer their role in the reconfiguration of the nightside of the magnetosphere. We examine the contributions of plasmoids to the magnetic flux transfer cycle at both planets. At Jupiter, there is evidence of an extended interval after reconnection where the field remains northward (analogous to the terrestrial post-plasmoid plasma sheet). At Saturn we see a similar feature, and calculate the amount of flux closed on average in reconnection events, leading us to an estimation of the recurrence rate of plasmoid release.

  14. Reconnection in Solar Flares: Outstanding Questions Hiroaki Isobe ...

    Indian Academy of Sciences (India)

    The idea of magnetic reconnection has been applied, not only to solar flares, but to various explosive phenomena in the solar atmosphere (e.g., Shibata et al. 1992;. ∗. Present address: Unit of Synergetic Studies for .... sheet, creating many small plasmoid as shown in the left panel of Fig. 1. This is remarkably similar to the.

  15. Reconnection Mediated by Magnetic Fractures and the Solar Flare

    Science.gov (United States)

    Haerendel, Gerhard

    2018-03-01

    Reconnection of sheared magnetic fields is commonly treated by regarding the component perpendicular to the antiparallel components as a largely inert guide field. In this paper an alternative is proposed in which the free energy residing in the shear field is being converted prior to reconnection. This happens in high-density, dissipative current sheets bordering the reconnection site. A global scenario is presented in which low-intensity currents out of the photosphere are converging into the narrow, high-intensity currents at high altitude. This is enabled by the obliqueness of the latter. The very short timescale of the energy conversion causes a lateral propagation of the current sheets. In a quasi-stationary situation, it balances the reconnection rate, which turns out to be much lower than in guide-field approaches. Another important consequence of the obliqueness is the field-parallel emission of runaway electrons. Accelerated up to tens of keV, they are possibly important contributors to the production of hard X-rays during the impulsive phase of a flare, but only in areas of upward-directed currents. Quantitative evaluation of the model predicts various potentially observable properties, such as width and propagation speed of the generated flare ribbons, spatial dependences of the electron spectrum, size of the area of energy deposition, and successive decrease of the shear angle between conjugate footpoints. The presented theoretical model can account for the observed brightness asymmetry of flare ribbons with respect to the direction of the vertical currents.

  16. Conditions for substorm onset by the fast reconnection mechanism

    Directory of Open Access Journals (Sweden)

    M. Ugai

    2008-12-01

    Full Text Available The fast reconnection mechanism, involving slow shocks and Alfvénic fast plasma jets, is most responsible for the explosive conversion of magnetic energy associated with geomagnetic substorms and solar flares. In this paper, the spontaneous fast reconnection model is applied to well-known phenomena of substorms. When the east-west width of the tail current sheet becomes 3–4 times larger than its north-south thickness, the fast reconnection mechanism can fully be established, which may lead to substorm onset. The resulting Alfvénic jet can exactly explain, both qualitatively and quantitatively, the in-situ satellite observations of the traveling compression regions (TCRs associated with large-scale plasmoids propagating down the tail. Also, the earthward fast reconnection jet causes drastic magnetic field dipolarization, so that the sheet current ahead of the magnetic loop of closed field lines suddenly turns its direction toward the loop footpoint and a large-scale current wedge is formed according to the growth of field-aligned currents. It is demonstrated that an MHD generator arises ahead of the magnetic loop and drives the current wedge to distinctly enhance the current density in a pair of thin layers of the loop footpoint, giving rise to drastic heating in the form of two ribbons.

  17. Adiabatic plasma equilibrium and application to a reconnection problem

    International Nuclear Information System (INIS)

    Zaharia, Sorin; Birn, J.

    2007-01-01

    The evolution of many plasma systems is adiabatic, i.e., plasma entropy is conserved in each magnetic flux tube. An apparently surprising result found recently from simulations of a forced magnetic reconnection problem (the 'Newton Challenge' [J. Birn et al., Phys. Plasmas 13, 092117 (2006)]) is that even in the presence of a dissipative process such as reconnection, the entropy within a flux tube can still be approximately conserved, due to the strong localization of the dissipation. To address plasma equilibrium with such adiabatic constraints, a novel code has been developed that computes equilibria with entropy profile as input, using the alternating dimension method [H. Grad et al., Proc. Natl. Acad. Sci. USA 72, 3789 (1975)]. The code alternates between solving the two-dimensional (2D) Grad-Shafranov equation to obtain the field configuration (flux function A) from the pressure profile P(A) and a 1D ordinary differential equation that uses the entropy conservation to derive the pressure function P(A) from a flux surface average. As a particular application, the code is used to compute equilibria relevant to the Newton Challenge, with a grid reflecting the reconnected state topology (with an X and an O point). The equilibria found agree very well with late stages of magnetohydrodynamic simulations of the Newton Challenge. This agreement not only validates the new code, but also proves that the final state approached by the reconnection simulations is indeed an equilibrium quasiadiabatically connected with the initial state. The results also show a significant release of magnetic energy through reconnection. Finally, other potential applications of the new code, especially to adiabatic evolution of space plasmas, are discussed

  18. Onset of 2D magnetic reconnection in the solar photosphere, chromosphere, and corona

    Science.gov (United States)

    Snow, B.; Botha, G. J. J.; McLaughlin, J. A.; Hillier, A.

    2018-01-01

    Aims: We aim to investigate the onset of 2D time-dependent magnetic reconnection that is triggered using an external (non-local) velocity driver located away from, and perpendicular to, an equilibrium Harris current sheet. Previous studies have typically utilised an internal trigger to initiate reconnection, for example initial conditions centred on the current sheet. Here, an external driver allows for a more naturalistic trigger as well as the study of the earlier stages of the reconnection start-up process. Methods: Numerical simulations solving the compressible, resistive magnetohydrodynamic (MHD) equations were performed to investigate the reconnection onset within different atmospheric layers of the Sun, namely the corona, chromosphere and photosphere. Results: A reconnecting state is reached for all atmospheric heights considered, with the dominant physics being highly dependent on atmospheric conditions. The coronal case achieves a sharp rise in electric field (indicative of reconnection) for a range of velocity drivers. For the chromosphere, we find a larger velocity amplitude is required to trigger reconnection (compared to the corona). For the photospheric environment, the electric field is highly dependent on the inflow speed; a sharp increase in electric field is obtained only as the velocity entering the reconnection region approaches the Alfvén speed. Additionally, the role of ambipolar diffusion is investigated for the chromospheric case and we find that the ambipolar diffusion alters the structure of the current density in the inflow region. Conclusions: The rate at which flux enters the reconnection region is controlled by the inflow velocity. This determines all aspects of the reconnection start-up process, that is, the early onset of reconnection is dominated by the advection term in Ohm's law in all atmospheric layers. A lower plasma-β enhances reconnection and creates a large change in the electric field. A high plasma-β hinders the

  19. Observations of Reconnection Flows in a Flare on the Solar Disk

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Juntao; Simões, P. J. A.; Jeffrey, N. L. S.; Fletcher, L.; Wright, P. J.; Hannah, I. G., E-mail: j.wang.4@research.gla.ac.uk [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2017-09-20

    Magnetic reconnection is a well-accepted part of the theory of solar eruptive events, though the evidence is still circumstantial. Intrinsic to the reconnection picture of a solar eruptive event, particularly in the standard model for two-ribbon flares (CSHKP model), are an advective flow of magnetized plasma into the reconnection region, expansion of field above the reconnection region as a flux rope erupts, retraction of heated post-reconnection loops, and downflows of cooling plasma along those loops. We report on a unique set of Solar Dynamics Observatory /Atmospheric Imaging Assembly imaging and Hinode /EUV Imaging Spectrometer spectroscopic observations of the disk flare SOL2016-03-23T03:54 in which all four flows are present simultaneously. This includes spectroscopic evidence for a plasma upflow in association with large-scale expanding closed inflow field. The reconnection inflows are symmetric, and consistent with fast reconnection, and the post-reconnection loops show a clear cooling and deceleration as they retract. Observations of coronal reconnection flows are still rare, and most events are observed at the solar limb, obscured by complex foregrounds, making their relationship to the flare ribbons, cusp field, and arcades formed in the lower atmosphere difficult to interpret. The disk location and favorable perspective of this event have removed these ambiguities giving a clear picture of the reconnection dynamics.

  20. Scales of guide field reconnection at the hydrogen mass ratio

    International Nuclear Information System (INIS)

    Lapenta, G.; Markidis, S.; Divin, A.; Goldman, M.; Newman, D.

    2010-01-01

    We analyze the signatures of component reconnection for a Harris current sheet with a guide field using the physical mass ratio of hydrogen. The study uses the fully kinetic particle in cell code IPIC3D to investigate the scaling with mass ratio of the following three main component reconnection features: electron density cavities along the separatrices, channels of fast electron flow within the cavities, and electron phase space holes due to the Buneman instability in the electron high speed channels. The width and strength of the electron holes and of the electron cavities are studied up the mass ratio proper of hydrogen, considering the effect of the simulation box size, and of the boundary conditions. The results compare favorably with the existing data from the Cluster and Themis missions and provide quantitative predictions for realistic conditions to be encountered by the planned magnetospheric multiscale mission.

  1. Moving grids for magnetic reconnection via Newton-Krylov methods

    KAUST Repository

    Yuan, Xuefei

    2011-01-01

    This paper presents a set of computationally efficient, adaptive grids for magnetic reconnection phenomenon where the current density can develop large gradients in the reconnection region. Four-field extended MagnetoHydroDynamics (MHD) equations with hyperviscosity terms are transformed so that the curvilinear coordinates replace the Cartesian coordinates as the independent variables, and moving grids\\' velocities are also considered in this transformed system as a part of interpolating the physical solutions from the old grid to the new grid as time advances. The curvilinear coordinates derived from the current density through the Monge-Kantorovich (MK) optimization approach help to reduce the resolution requirements during the computation. © 2010 Elsevier B.V. All rights reserved.

  2. Scales of guide field reconnection at the hydrogen mass ratio

    Science.gov (United States)

    Lapenta, G.; Markidis, S.; Divin, A.; Goldman, M.; Newman, D.

    2010-08-01

    We analyze the signatures of component reconnection for a Harris current sheet with a guide field using the physical mass ratio of hydrogen. The study uses the fully kinetic particle in cell code IPIC3D to investigate the scaling with mass ratio of the following three main component reconnection features: electron density cavities along the separatrices, channels of fast electron flow within the cavities, and electron phase space holes due to the Buneman instability in the electron high speed channels. The width and strength of the electron holes and of the electron cavities are studied up the mass ratio proper of hydrogen, considering the effect of the simulation box size, and of the boundary conditions. The results compare favorably with the existing data from the Cluster and Themis missions and provide quantitative predictions for realistic conditions to be encountered by the planned magnetospheric multiscale mission.

  3. Theory and Simulations of Incomplete Reconnection During Sawteeth Due to Diamagnetic Effects

    Science.gov (United States)

    Beidler, Matthew Thomas

    Tokamaks use magnetic fields to confine plasmas to achieve fusion; they are the leading approach proposed for the widespread production of fusion energy. The sawtooth crash in tokamaks limits the core temperature, adversely impacts confinement, and seeds disruptions. Adequate knowledge of the physics governing the sawtooth crash and a predictive capability of its ramifications has been elusive, including an understanding of incomplete reconnection, i.e., why sawteeth often cease prematurely before processing all available magnetic flux. In this dissertation, we introduce a model for incomplete reconnection in sawtooth crashes resulting from increasing diamagnetic effects in the nonlinear phase of magnetic reconnection. Physically, the reconnection inflow self-consistently convects the high pressure core of a tokamak toward the q=1 rational surface, thereby increasing the pressure gradient at the reconnection site. If the pressure gradient at the rational surface becomes large enough due to the self-consistent evolution, incomplete reconnection will occur due to diamagnetic effects becoming large enough to suppress reconnection. Predictions of this model are borne out in large-scale proof-of-principle two-fluid simulations of reconnection in a 2D slab geometry and are also consistent with data from the Mega Ampere Spherical Tokamak (MAST). Additionally, we present simulations from the 3D extended-MHD code M3D-C1 used to study the sawtooth crash in a 3D toroidal geometry for resistive-MHD and two-fluid models. This is the first study in a 3D tokamak geometry to show that the inclusion of two-fluid physics in the model equations is essential for recovering timescales more closely in line with experimental results compared to resistive-MHD and contrast the dynamics in the two models. We use a novel approach to sample the data in the plane of reconnection perpendicular to the (m,n)=(1,1) mode to carefully assess the reconnection physics. Using local measures of

  4. Acceleration mechanisms flares, magnetic reconnection and shock waves

    International Nuclear Information System (INIS)

    Colgate, S.A.

    1979-01-01

    Several mechanisms are briefly discussed for the acceleration of particles in the astrophysical environment. Included are hydrodynamic acceleration, spherically convergent shocks, shock and a density gradient, coherent electromagnetic acceleration, the flux tube origin, symmetries and instabilities, reconnection, galactic flares, intergalactic acceleration, stochastic acceleration, and astrophysical shocks. It is noted that the supernova shock wave models still depend critically on the presupernova star structure and the assumption of highly compact presupernova models for type I supernovae. 37 references

  5. An Integrative Review of Scientific Evidence for Reconnective Healing

    OpenAIRE

    Baldwin, Ann L.; Trent, Natalie L.

    2017-01-01

    Abstract Background: Biofield therapies offer a novel, non-invasive approach to treating chronic diseases based on assessing and adjusting an individual's physiological and emotional responses through their bio-energetic field. Reconnective Healing™ (RH) is defined as: “…not just energy healing, but instead a more comprehensive spectrum of healing composed of energy, light, and information.” Objectives: Several biofield therapies, such as Reiki, Therapeutic Touch and Johrei, have already been...

  6. The dependence of cusp ion signatures on the reconnection rate

    Directory of Open Access Journals (Sweden)

    S. K. Morley

    2003-04-01

    Full Text Available The interpretation of structure in cusp ion dispersions is important for helping to understand the temporal and spatial structure of magnetopause reconnection. "Stepped" and "sawtooth" signatures have been shown to be caused by temporal variations in the reconnection rate under the same physical conditions for different satellite trajectories. The present paper shows that even for a single satellite path, a change in the amplitude of any reconnection pulses can alter the observed signature and even turn sawtooth into stepped forms and vice versa. On 20 August 1998, the Defense Meteorological Satellite Program (DMSP craft F-14 crossed the cusp just to the south of Longyearbyen, returning on the following orbit. The two passes by the DMSP F-14 satellites have very similar trajectories and the open-closed field line boundary (OCB crossings, as estimated from the SSJ/4 precipitating particle data and Polar UVI images, imply a similarly-shaped polar cap, yet the cusp ion dispersion signatures differ substantially. The cusp crossing at 08:54 UT displays a stepped ion dispersion previously considered to be typical of a meridional pass, whereas the crossing at 10:38 UT is a sawtooth form ion dispersion, previously considered typical of a satellite travelling longitudinally with respect to the OCB. It is shown that this change in dispersed ion signature is likely to be due to a change in the amplitude of the pulses in the reconnection rate, causing the stepped signature. Modelling of the low-energy ion cutoff under different conditions has reproduced the forms of signature observed.Key words. Ionosphere (particle precipitation Magnetospheric physics (energetic particles, precipitating, magnetopause, cusp and boundary layers

  7. MESSENGER Observations of Magnetic Reconnection in Mercury's Magnetosphere

    Science.gov (United States)

    Slavin. James A.

    2009-01-01

    During MESSENGER'S second flyby of Mercury on October 6,2008, very intense reconnection was observed between the planet's magnetic field and a steady southward interplanetary magnetic field (IMF). The dawn magnetopause was threaded by a strong magnetic field normal to its surface, approx.14 nT, that implies a rate of reconnection approx.10 times the typical rate at Earth and a cross-magnetospheric electric potential drop of approx.30 kV. The highest magnetic field observed during this second flyby, approx.160 nT, was found at the core of a large dayside flux transfer event (FTE). This FTE is estimated to contain magnetic flux equal to approx.5% that of Mercury's magnetic tail or approximately one order of magnitude higher fraction of the tail flux than is typically found for FTEs at Earth. Plasmoid and traveling compression region (TCR) signatures were observed throughout MESSENGER'S traversal of Mercury's magnetotail with a repetition rate comparable to the Dungey cycle time of approx.2 min. The TCR signatures changed from south-north, indicating tailward motion, to north-south, indicating sunward motion, at a distance approx.2.6 RM (where RM is Mercury's radius) behind the terminator indicating that the near-Mercury magnetotail neutral line was crossed at that point. Overall, these new MESSENGER observations suggest that magnetic reconnection at the dayside magnetopause is very intense relative to what is found at Earth and other planets, while reconnection in Mercury's tail is similar to that in other planetary magnetospheres, but with a very short Dungey cycle time.

  8. Magnetic reconnection processes induced by a CME expansion

    Directory of Open Access Journals (Sweden)

    A. Bemporad

    2008-10-01

    Full Text Available On 10–11 December 2005 a slow CME occurred in the Western Hemisphere in between two coronal streamers. SOHO/MDI magnetograms show a multipolar magnetic configuration at the photosphere: a complex of active regions located at the CME source and two bipoles at the base of the lateral coronal streamers. White light observations reveal that the CME expansion affects both of them and induces the release of plasma within or close to the nearby streamers. These transient phenomena are possibly due to magnetic reconnections induced by the CME expansion and occurring inside the streamer current sheet or between the CME flanks and the streamer. These events have been observed by the SOHO/UVCS with the spectrometer slit centered at 1.8 R⊙ over about a full day. In this work we focus on the interaction between the CME and the streamer: the UVCS spectral interval included UV lines from ions at different temperatures of maximum formation such as O VI, Si XIII and Al Xi. These data gave us the opportunity to infer the evolution of plasma temperature and density at the reconnection site and adjacent regions. These are relevant to characterize secondary reconnection processes occurring during a CME development.

  9. Coordinated Cluster/Double Star observations of dayside reconnection signatures

    Directory of Open Access Journals (Sweden)

    M. W. Dunlop

    2005-11-01

    Full Text Available The recent launch of the equatorial spacecraft of the Double Star mission, TC-1, has provided an unprecedented opportunity to monitor the southern hemisphere dayside magnetopause boundary layer in conjunction with northern hemisphere observations by the quartet of Cluster spacecraft. We present first results of one such situation where, on 6 April 2004, both Cluster and the Double Star TC-1 spacecraft were on outbound transits through the dawnside magnetosphere. The observations are consistent with ongoing reconnection on the dayside magnetopause, resulting in a series of flux transfer events (FTEs seen both at Cluster and TC-1, which appear to lie north and south of the reconnection line, respectively. In fact, the observed polarity and motion of each FTE signature advocates the existence of an active reconnection region consistently located between the positions of Cluster and TC-1, with Cluster observing northward moving FTEs with +/- polarity, whereas TC-1 sees -/+ polarity FTEs. This assertion is further supported by the application of a model designed to track flux tube motion for the prevailing interplanetary conditions. The results from this model show, in addition, that the low-latitude FTE dynamics are sensitive to changes in convected upstream conditions. In particular, changing the interplanetary magnetic field (IMF clock angle in the model suggests that TC-1 should miss the resulting FTEs more often than Cluster and this is borne out by the observations.

  10. Small-Scale Dayside Magnetic Reconnection Analysis via MMS

    Science.gov (United States)

    Pritchard, K. R.; Burch, J. L.; Fuselier, S. A.; Webster, J.; Genestreti, K.; Torbert, R. B.; Rager, A. C.; Phan, T.; Argall, M. R.; Le Contel, O.; Russell, C. T.; Strangeway, R. J.; Giles, B. L.

    2017-12-01

    The Magnetospheric Multiscale (MMS) mission has the primary objective of understanding the physics of the reconnection electron diffusion region (EDR), where magnetic energy is transformed into particle energy. In this poster, we present data from an EDR encounter that occurred in late December 2016 at approximately 11:00 MLT with a moderate guide field. The spacecraft were in a tetrahedral formation with an average inter-spacecraft distance of approximately 7 kilometers. During this event electron crescent-shaped distributions were observed in the electron stagnation region as is typical for asymmetric reconnection. Based on the observed ion velocity jets, the spacecraft traveled just south of the EDR. Because of the close spacecraft separation, fairly accurate computation of the Hall, electron pressure divergence, and electron inertia components of the reconnection electric field could be made. In the region of the crescent distributions good agreement was observed, with the strongest component being the normal electric field and the most significant sources being electron pressure divergence and the Hall electric field. While the strongest currents were in the out-of-plane direction, the dissipation was strongest in the normal direction because of the larger magnitude of the normal electric field component. These results are discussed in light of recent 3D PIC simulations performed by other groups.

  11. Magnetospheric Multiscale Satellites Observations of Parallel Electric Fields Associated with Magnetic Reconnection

    Science.gov (United States)

    Ergun, R. E.; Goodrich, K. A.; Wilder, F. D.; Holmes, J. C.; Stawarz, J. E.; Eriksson, S.; Sturner, A. P.; Malaspina, D. M.; Usanova, M. E.; Torbert, R. B.; Lindqvist, P.-A.; Khotyaintsev, Y.; Burch, J. L.; Strangeway, R. J.; Russell, C. T.; Pollock, C. J.; Giles, B. L.; Hesse, M.; Chen, L. J.; Lapenta, G.; Goldman, M. V.; Newman, D. L.; Schwartz, S. J.; Eastwood, J. P.; Phan, T. D.; Mozer, F. S.; Drake, J.; Shay, M. A.; Cassak, P. A.; Nakamura, R.; Marklund, G.

    2016-06-01

    We report observations from the Magnetospheric Multiscale satellites of parallel electric fields (E∥ ) associated with magnetic reconnection in the subsolar region of the Earth's magnetopause. E∥ events near the electron diffusion region have amplitudes on the order of 100 mV /m , which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of E∥ events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These E∥ events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields.

  12. Physics of collisionless scrape-off-layer plasma during normal and off-normal Tokamak operating conditions.

    Energy Technology Data Exchange (ETDEWEB)

    Hassanein, A.; Konkashbaev, I.

    1999-03-15

    The structure of a collisionless scrape-off-layer (SOL) plasma in tokamak reactors is being studied to define the electron distribution function and the corresponding sheath potential between the divertor plate and the edge plasma. The collisionless model is shown to be valid during the thermal phase of a plasma disruption, as well as during the newly desired low-recycling normal phase of operation with low-density, high-temperature, edge plasma conditions. An analytical solution is developed by solving the Fokker-Planck equation for electron distribution and balance in the SOL. The solution is in good agreement with numerical studies using Monte-Carlo methods. The analytical solutions provide an insight to the role of different physical and geometrical processes in a collisionless SOL during disruptions and during the enhanced phase of normal operation over a wide range of parameters.

  13. The formation of rings and gaps in magnetically coupled disk-wind systems: ambipolar diffusion and reconnection

    Science.gov (United States)

    Suriano, Scott S.; Li, Zhi-Yun; Krasnopolsky, Ruben; Shang, Hsien

    2018-03-01

    Radial substructures in circumstellar disks are now routinely observed by ALMA. There is also growing evidence that disk winds drive accretion in such disks. We show through 2D (axisymmetric) simulations that rings and gaps develop naturally in magnetically coupled disk-wind systems on the scale of tens of au, where ambipolar diffusion (AD) is the dominant non-ideal MHD effect. In simulations where the magnetic field and matter are moderately coupled, the disk remains relatively laminar with the radial electric current steepened by AD into a thin layer near the midplane. The toroidal magnetic field sharply reverses polarity in this layer, generating a large magnetic torque that drives fast accretion, which drags the poloidal field into a highly pinched radial configuration. The reconnection of this pinched field creates magnetic loops where the net poloidal magnetic flux (and thus the accretion rate) is reduced, yielding dense rings. Neighbouring regions with stronger poloidal magnetic fields accrete faster, forming gaps. In better magnetically coupled simulations, the so-called `avalanche accretion streams' develop continuously near the disk surface, rendering the disk-wind system more chaotic. Nevertheless, prominent rings and gaps are still produced, at least in part, by reconnection, which again enables the segregation of the poloidal field and the disk material similar to the more diffusive disks. However, the reconnection is now driven by the non-linear growth of MRI channel flows. The formation of rings and gaps in rapidly accreting yet laminar disks has interesting implications for dust settling and trapping, grain growth, and planet formation.

  14. From Conformal Invariance towards Dynamical Symmetries of the Collisionless Boltzmann Equation

    Directory of Open Access Journals (Sweden)

    Stoimen Stoimenov

    2015-09-01

    Full Text Available Dynamical symmetries of the collisionless Boltzmann transport equation, or Vlasov equation, but under the influence of an external driving force, are derived from non-standard representations of the 2D conformal algebra. In the case without external forces, the symmetry of the conformally-invariant transport equation is first generalized by considering the particle momentum as an independent variable. This new conformal representation can be further extended to include an external force. The construction and possible physical applications are outlined.

  15. Nonlinear phenomena in collisionless plasmas. Progress report, September 1, 1974--August 31, 1975

    International Nuclear Information System (INIS)

    Aamodt, R.E.

    1975-01-01

    The nonlinear evolution of unstable collective modes common to conventional mirror machines is being analyzed in order to evaluate measurable saturation amplitudes, spectrum properties, and concomitant particle loss rates. The nonlinear dispersion relation for the classic drift-cone mode, including nonlinear E x B VECTOR convective cells is presently being evaluated to find its self-saturation properties. Large amplitude rf heating mechanisms, localized mode nonlinearities, and propagation and amplification of transverse modes in collisionless inhomogeneous plasmas have also been partially evaluated. (U.S.)

  16. A new formulation of theta pinch implosions - a collisionless wave model

    International Nuclear Information System (INIS)

    Tsui, K.H.

    Previous work in theta pinch implosions is characterized by anomalous resistivity owing its origin to plasma instabilities. A diametrically opposite collisionless model is proposed here that consists of an inhomogeneous wave equation. The electron velocities are solved by guiding center approximation. This model offers qualitative explanations to various effects like experimental Alfven scaling law, Alfven penetration time, sheath thickness, shock formation, shock width, piston thickness, Alfven Mach number. Although collision is not essential, the plasma has an apparent resistivity with an effective collision frequency of roughly the same as those anomalous ones used in turbulent model. (Author) [pt

  17. Charging-delay induced dust acoustic collisionless shock wave: Roles of negative ions

    International Nuclear Information System (INIS)

    Ghosh, Samiran; Bharuthram, R.; Khan, Manoranjan; Gupta, M. R.

    2006-01-01

    The effects of charging-delay and negative ions on nonlinear dust acoustic waves are investigated. It has been found that the charging-delay induced anomalous dissipation causes generation of dust acoustic collisionless shock waves in an electronegative dusty plasma. The small but finite amplitude wave is governed by a Korteweg-de Vries Burger equation in which the Burger term arises due to the charging-delay. Numerical investigations reveal that the charging-delay induced dissipation and shock strength decreases (increases) with the increase of negative ion concentration (temperature)

  18. An analytical method for the investigation of instability of a collisionless plasma in strong magnetic fields

    International Nuclear Information System (INIS)

    Zakharov, V.U.

    1993-01-01

    An analytical method for the investigation of special types of dispersion relations is presented. In particular, analysis of the propagation of small-amplitude hydromagnetic waves in a collisionless plasma in a strong magnetic field leads to such dispersion relations. The fifth-degree dispersion relation corresponding to a particular case is considered. The necessary stability condition for a steady state and conditions for the degeneration of small-amplitude waves are derived. A comparison with other methods for the analysis of similar dispersion relations is also presented. (author)

  19. Experimental investigation of a collisionless shock wave in a longitudinal magnetic field

    International Nuclear Information System (INIS)

    El-Khalafawy, T.A.; El-Nicklawy, M.; Beshara, A.B.; Abo-Ellil, M.S.

    1978-01-01

    The results of the experimental investigations of the parameters and the structure of a shock wave propagating along a static magnetic field are discussed. It is also shown that the wave observed experimentally represents a ''switch-on'' shock and its front structure is determined by the mechanism of the energy collisionless dissipation. In case of small Alfvene-Mach numbers I 3 smaller than the conductivity caused by Coulombs' collisions. The paper describes briefly the installation and also the probe methods of measuring the main plasma parameters, (the electron temperature Tsub(e) and the density nsub(e))

  20. Microstructure in two- and three-dimensional hybrid simulations of perpendicular collisionless shocks

    Czech Academy of Sciences Publication Activity Database

    Burgess, D.; Hellinger, Petr; Gingell, I.; Trávníček, Pavel M.

    2016-01-01

    Roč. 82, č. 4 (2016), 905820401/1-905820401/23 ISSN 0022-3778 Institutional support: RVO:68378289 Keywords : ion-acceleration * numerical simulations * bow shock * electron acceleration * cluster observations * self-reformation * magnetic-field * whistler waves * injection * nonstationarity Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.160, year: 2016 https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/microstructure-in-two- and -three-dimensional-hybrid-simulations-of-perpendicular-collisionless-shocks/F964EF89FB14A6504A49CFAD54970E2B

  1. Density filament and helical field line structures in three dimensional Weibel-mediated collisionless shocks

    International Nuclear Information System (INIS)

    Moritaka, Toseo; Kuramitsu, Yasuhiro; Sakawa, Youichi; Yamaura, Yuta; Ishikawa, Taishi; Takabe, Hideaki; Morita, Taichi

    2016-01-01

    Collisionless shocks mediated by Weibel instability are attracting attention for their relevance to experimental demonstrations of astrophysical shocks in high-intensity laser facilities. The three dimensional structure of Weibel-mediated shocks is investigated through a fully kinetic particle-in-cell simulation. The structures obtained are characterized by the following features: (i) helical magnetic field lines elongated in the direction upstream of the shock region, (ii) high and low density filaments inside the helical field lines. These structures originate from the interaction between counter-streaming plasma flow and magnetic vortexes caused by Weibel instability, and potentially affect the shock formation mechanism. (paper)

  2. Collisionless distribution function of charged particles ensemble in a tokamak magnetic configuration with magnetic island

    Science.gov (United States)

    Podturova, O. I.

    2017-10-01

    The collisionless distribution function of charged particle ensemble in the magnetic field of tokamak with a magnetic island is calculated. The calculation is based on the solution of the kinetic equation with source together with three-dimensional numerical calculations of charged particle trajectories. It is shown that in case of an inhomogeneous source trajectory, motion of trapped particles leads to anisotropization of the initially isotropic distribution of particle ensemble. The absence of contribution from the passing particles decreases the efficiency of spontaneous generation of a non-induction current in the magnetic island in comparison with the bootstrap effect in the system of nested magnetic surfaces.

  3. Spontaneous magnetic fluctuations and collisionless regulation of the Earth's plasma sheet

    Science.gov (United States)

    Moya, P. S.; Espinoza, C.; Stepanova, M. V.; Antonova, E. E.; Valdivia, J. A.

    2017-12-01

    Even in the absence of instabilities, plasmas often exhibit inherent electromagnetic fluctuations which are present due to the thermal motion of charged particles, sometimes called thermal (quasi-thermal) noise. One of the fundamental and challenging problems of laboratory, space, and astrophysical plasma physics is the understanding of the relaxation processes of nearly collisionless plasmas, and the resultant state of electromagnetic plasma turbulence. The study of thermal fluctuations can be elegantly addressed by using the Fluctuation-Dissipation Theorem that describes the average amplitude of the fluctuations through correlations of the linear response of the media with the perturbations of the equilibrium state (the dissipation). Recently, it has been shown that solar wind plasma beta and temperature anisotropy observations are bounded by kinetic instabilities such as the ion cyclotron, mirror, and firehose instabilities. The magnetic fluctuations observed within the bounded area are consistent with the predictions of the Fluctuation-Dissipation theorem even far below the kinetic instability thresholds, with an enhancement of the fluctuation level near the thresholds. Here, for the very first time, using in-situ magnetic field and plasma data from the THEMIS spacecraft, we show that such regulation also occurs in the Earth's plasma sheet at the ion scales and that, regardless of the clear differences between the solar wind and the magnetosphere environments, spontaneous fluctuation and their collisionless regulation seem to be fundamental features of space and astrophysical plasmas, suggesting the universality of the processes.

  4. Investigating the Formation and Sub-Structure of Unmagnetized Collisionless Shocks

    Science.gov (United States)

    Endrizzi, Douglass; Egedal, J.; Forest, C.; Greess, S.; Millet-Ayala, A.; Olson, J.; Ready, A.; Waleffe, R.; Gota, H.

    2017-10-01

    Collisionless shocks, where the shock thickness is much smaller than the collisional mean free path, are ubiquitous astrophysical phenomena. In all shocks, the Rankine-Hugoniot jump conditions are satisfied through entropy generation at the interface; the shock propagation angle with respect to the magnetic field affects the mechanism by which this entropy is generated. Two experiments on the Big Red Ball (BRB) at UW-Madison explored the formation mechanisms of parallel and perpendicular, unmagnetized and magnetized collisionless shocks with large (1 - 3 m) system sizes. In the first experiment, a 1 m diameter theta-pinch drove a supersonic (3 probes were used to measure electron density, temperature, plasma potential, and fluctuations in magnetic fields. Results showing the transition from above to below MA = 1 , measurements of electron precursors, exploration of subshock structure, evidence of instabilities in the shock formation process, and future work will be presented. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE 1256259.

  5. Laser plasma simulations of the generation processes of Alfven and collisionless shock waves in space plasma

    International Nuclear Information System (INIS)

    Prokopov, P A; Zakharov, Yu P; Tishchenko, V N; Shaikhislamov, I F; Boyarintsev, E L; Melekhov, A V; Ponomarenko, A G; Posukh, V G; Terekhin, V A

    2016-01-01

    Generation of Alfven waves propagating along external magnetic field B 0 and Collisionless Shock Waves propagating across B 0 are studied in experiments with laser- produced plasma and magnetized background plasma. The collisionless interaction of interpenetrating plasma flows takes place through a so-called Magnetic Laminar Mechanism (MLM) or Larmor Coupling. At the edge of diamagnetic cavity LP-ions produce induction electric field E φ which accelerates BP-ions while LP-ions rotate in opposite direction. The ions movement generates sheared azimuthal magnetic field B φ which could launches torsional Alfven wave. In previous experiments at KI-1 large scale facility a generation of strong perturbations propagating across B 0 with magnetosonic speed has been studied at a moderate value of interaction parameter δ∼0.3. In the present work we report on experiments at conditions of 5∼R2 and large Alfven-Mach number M A ∼10 in which strong transverse perturbations traveling at a scale of ∼1 m in background plasma at a density of ∼3*10 13 cm -3 is observed. At the same conditions but smaller M A ∼ 2 a generation, the structure and dynamic of Alfven wave with wavelength ∼0.5 m propagating along fields B 0 ∼100÷500 G for a distance of ∼2.5 m is studied. (paper)

  6. Equilibrium and low-frequency stability of a uniform density, collisionless, spherical Vlasov system

    International Nuclear Information System (INIS)

    Barnes, D.C.; Chacon, L.; Finn, J.M.

    2002-01-01

    Equilibrium and stability of a collisionless, spherical Vlasov system with uniform density are considered. Such an electron system is useful for the Periodically Oscillating Plasma Sphere (POPS) fusion system. In POPS the space charge of a uniform-density spherical electron cloud provides a harmonic well for an under-dense thermal ion population. Previous special solutions [D. C. Barnes, Phys. Plasmas 6, 4472 (1999)] are extended to arbitrary energy dependence. These equilibrium distribution functions and their first derivatives may be made nonsingular, in contrast to the previous solutions. Linear stability of general spherical equilibria is considered, and reduced to a one-dimensional calculation by the introduction of a spherical harmonic decomposition. All azimuthal mode numbers are degenerate. Using this formalism, the low-frequency stability of a collisionless, spherical Vlasov electron system coupled to a minority ion cloud is studied for the class of uniform-density electron equilibria found. In the low-frequency (adiabatic) limit, the general kinetic stability formalism can be integrated to find a closed form for the response of electron number density. The adiabatic response operator is shown to be self-adjoint. Computation of its eigenvalues proves the constant-density electrons/thermal ions system in POPS to be mostly stable to ion-electron electrostatic modes. Unstable modes are avoided unless central electrons have an extremely small energy spread. These results may also be useful for the consideration of gravitational and beam systems

  7. Particle acceleration via reconnection processes in the supersonic solar wind

    International Nuclear Information System (INIS)

    Zank, G. P.; Le Roux, J. A.; Webb, G. M.; Dosch, A.; Khabarova, O.

    2014-01-01

    An emerging paradigm for the dissipation of magnetic turbulence in the supersonic solar wind is via localized small-scale reconnection processes, essentially between quasi-2D interacting magnetic islands. Charged particles trapped in merging magnetic islands can be accelerated by the electric field generated by magnetic island merging and the contraction of magnetic islands. We derive a gyrophase-averaged transport equation for particles experiencing pitch-angle scattering and energization in a super-Alfvénic flowing plasma experiencing multiple small-scale reconnection events. A simpler advection-diffusion transport equation for a nearly isotropic particle distribution is derived. The dominant charged particle energization processes are (1) the electric field induced by quasi-2D magnetic island merging and (2) magnetic island contraction. The magnetic island topology ensures that charged particles are trapped in regions where they experience repeated interactions with the induced electric field or contracting magnetic islands. Steady-state solutions of the isotropic transport equation with only the induced electric field and a fixed source yield a power-law spectrum for the accelerated particles with index α = –(3 + M A )/2, where M A is the Alfvén Mach number. Considering only magnetic island contraction yields power-law-like solutions with index –3(1 + τ c /(8τ diff )), where τ c /τ diff is the ratio of timescales between magnetic island contraction and charged particle diffusion. The general solution is a power-law-like solution with an index that depends on the Alfvén Mach number and the timescale ratio τ diff /τ c . Observed power-law distributions of energetic particles observed in the quiet supersonic solar wind at 1 AU may be a consequence of particle acceleration associated with dissipative small-scale reconnection processes in a turbulent plasma, including the widely reported c –5 (c particle speed) spectra observed by Fisk and Gloeckler

  8. Magnetic reconnection during steady magnetospheric convection and other magnetospheric modes

    Directory of Open Access Journals (Sweden)

    B. Hubert

    2017-03-01

    Full Text Available We use remote sensing of the proton aurora with the IMAGE-FUV SI12 (Imager for Magnetopause to Aurora Global Exploration–Far Ultraviolet–Spectrographic Imaging at 121.8 nm instrument and radar measurements of the ionospheric convection from the SuperDARN (Super Dual Aurora Radar Network facility to estimate the open magnetic flux in the Earth's magnetosphere and the reconnection rates at the dayside magnetopause and in the magnetotail during intervals of steady magnetospheric convection (SMC. We find that SMC intervals occur with relatively high open magnetic flux (average  ∼  0.745 GWb, standard deviation  ∼  0.16 GWb, which is often found to be nearly steady, when the magnetic flux opening and closure rates approximately balance around 55 kV on average, with a standard deviation of 21 kV. We find that the residence timescale of open magnetic flux, defined as the ratio between the open magnetospheric flux and the flux closure rate, is roughly 4 h during SMCs. Interestingly, this number is approximately what can be deduced from the discussion of the length of the tail published by Dungey (1965, assuming a solar wind speed of  ∼  450 km s−1. We also infer an enhanced convection velocity in the tail, driving open magnetic flux to the nightside reconnection site. We compare our results with previously published studies in order to identify different magnetospheric modes. These are ordered by increasing open magnetic flux and reconnection rate as quiet conditions, SMCs, substorms (with an important overlap between these last two and sawtooth intervals.

  9. Magnetic Reconnection at the Earliest Stage of Solar Flux Emergence

    Science.gov (United States)

    Tian, Hui; Zhu, Xiaoshuai; Peter, Hardi; Zhao, Jie; Samanta, Tanmoy; Chen, Yajie

    2018-02-01

    On 2016 September 20, the Interface Region Imaging Spectrograph observed an active region during its earliest emerging phase for almost 7 hr. The Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory observed continuous emergence of small-scale magnetic bipoles with a rate of ∼1016 Mx s‑1. The emergence of magnetic fluxes and interactions between different polarities lead to the frequent occurrence of ultraviolet (UV) bursts, which exhibit as intense transient brightenings in the 1400 Å images. In the meantime, discrete small patches with the same magnetic polarity tend to move together and merge, leading to the enhancement of the magnetic fields and thus the formation of pores (small sunspots) at some locations. The spectra of these UV bursts are characterized by the superposition of several chromospheric absorption lines on the greatly broadened profiles of some emission lines formed at typical transition region temperatures, suggesting heating of the local materials to a few tens of thousands of kelvin in the lower atmosphere by magnetic reconnection. Some bursts reveal blue- and redshifts of ∼100 km s‑1 at neighboring pixels, indicating the spatially resolved bidirectional reconnection outflows. Many such bursts appear to be associated with the cancellation of magnetic fluxes with a rate of the order of ∼1015 Mx s‑1. We also investigate the three-dimensional magnetic field topology through a magnetohydrostatic model and find that a small fraction of the bursts are associated with bald patches (magnetic dips). Finally, we find that almost all bursts are located in regions of large squashing factor at the height of ∼1 Mm, reinforcing our conclusion that these bursts are produced through reconnection in the lower atmosphere.

  10. 2D numerical simulation of the resistive reconnection layer

    International Nuclear Information System (INIS)

    Uzdensky, D. A.; Kulsrud, R. M.

    2000-01-01

    In this paper the authors present a two-dimensional numerical simulation of a reconnection current layer in incompressible resistive magnetohydrodynamics with uniform resistivity in the limit of very large Lundquist numbers. They use realistic boundary conditions derived consistently from the outside magnetic field, and they also take into account the effect of the backpressure from flow into the separatrix region. They find that within a few Alfven times the system reaches a steady state consistent with the Sweet-Parker model, even if the initial state is Petschek-like

  11. Double tearing reconnection and the off-axis sawteeth crash

    International Nuclear Information System (INIS)

    Li Ding

    1998-01-01

    A theoretical model is developed for the onset of the off-axis sawteeth crash observed in TFTR reversed magnetic shear experiments. The dispersion relation of the double tearing mode is obtained from the solution structure of the ideal external kink equation. The onset of 'annular crash' is due to the fast reconnection of the hot and cold islands, triggered by the interaction of both branches of the double tearing mode. The onset of 'core crash' is mainly due to the coalescence between the hot islands, triggered by the explosive growth of the inner branch and the rapid expansion of the hot islands. (author)

  12. SAR Observation and Numerical Simulation of Internal Solitary Wave Refraction and Reconnection Behind the Dongsha Atoll

    Science.gov (United States)

    Jia, T.; Liang, J. J.; Li, X.-M.; Sha, J.

    2018-01-01

    The refraction and reconnection of internal solitary waves (ISWs) around the Dongsha Atoll (DSA) in the northern South China Sea (SCS) are investigated based on spaceborne synthetic aperture radar (SAR) observations and numerical simulations. In general, a long ISW front propagating from the deep basin of the northern SCS splits into northern and southern branches when it passes the DSA. In this study, the statistics of Envisat Advanced SAR (ASAR) images show that the northern and southern wave branches can reconnect behind the DSA, but the reconnection location varies. A previously developed nonlinear refraction model is set up to simulate the refraction and reconnection of the ISWs behind the DSA, and the model is used to evaluate the effects of ocean stratification, background currents, and incoming ISW characteristics at the DSA on the variation in reconnection locations. The results of the first realistic simulation agree with consecutive TerraSAR-X (TSX) images captured within 12 h of each other. Further sensitivity simulations show that ocean stratification, background currents, and initial wave amplitudes all affect the phase speeds of wave branches and therefore shift their reconnection locations while shapes and locations of incoming wave branches upstream of the DSA profoundly influence the subsequent propagation paths. This study clarifies the variation in reconnection locations of ISWs downstream of the DSA and reveals the important mechanisms governing the reconnection process, which can improve our understanding of the propagation of ISWs near the DSA.

  13. Onset of reconnection in thin current sheets: Three-dimensional particle simulations

    Science.gov (United States)

    Scholer, M.; Sidorenko, I.; Jaroschek, C.; Treumann, R. A.

    2003-04-01

    The onset of reconnection in thin current sheets is investigated by means of three-dimensional full particle (PIC) simulations. Instead of imposing reconnection ab initio (as done in the GEM reconnection challenge), reconnection is allowed to develop out of the numerical noise. We do not impose symmetry about the midplane, so that the drift kink instability, the Kelvin-Helmholtz instability, and the sausage instability are allowed for, and we use a relatively high mass ratio of m_i/m_e=160. Two cases are investigated: (1) a thin current sheet with exactly anti-parallel fields,(2) a thin current sheet with a guide field of the same order as the anti-parallel field. In bothe cases the lower hybrid drift instability develops at the boundary of the current layer. The electric field in the center accelerates the electrons, while the ions are unmagnetized. The current density increase and the corresponding thinning of the current sheet results in case (1) in rapid reconnection on a time scale of about 10 inverse ion gyro-frequencies. While reconnection is initially patchy, the neutral lines merge and reconnection becomes eventually two-dimensional. In case (2) reconnection occurs after considerbly longer times and is essentially from the beginning two-dimensional.

  14. Experimental verification of the role of electron pressure in fast magnetic reconnection with a guide field

    Science.gov (United States)

    Fox, W.

    2017-10-01

    Magnetic reconnection enables explosive conversion of magnetic field energy to plasma kinetic energy in space and laboratory plasmas. In many reconnecting plasmas in space, solar, and laboratory plasmas, reconnection proceeds in the presence of a finite guide field (GF) such that the magnetic field lines meet at an angle less than 180°, and in magnetic fusion devices the guide field can be the largest component of the field. We report detailed laboratory observations of the structure of reconnection current sheets in a two-fluid plasma regime with a guide magnetic field. We observe and quantitatively analyze the quadrupolar electron pressure variation in the ion-diffusion region, as originally predicted by extended magnetohydrodynamics simulations. The projection of the electron pressure gradient parallel to the magnetic field contributes significantly to balancing the parallel electric field, and the results demonstrate how parallel and perpendicular force balance are coupled in guide field reconnection and confirm basic theoretical models of the importance of electron pressure gradients for obtaining fast magnetic reconnection. I discuss connections to observations of reconnection with finite guide field by spacecraft missions, and implications for two-fluid reconnection in magnetic fusion devices.

  15. Search for Colour Singlet and Colour Reconnection Effects in Hadronic Z Decays at LEP

    CERN Document Server

    Achard, P; Aguilar-Benítez, M; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Anderhub, H; Andreev, V P; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Bajo, A; Baksay, G; Baksay, L; Baldew, S V; Banerjee, S; Banerjee, Sw; Barczyk, A; Barillère, R; Bartalini, P; Basile, M; Batalova, N; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Bellucci, L; Berbeco, R; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Biasini, M; Biglietti, M; Biland, A; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böhm, A; Boldizsar, L; Borgia, B; Bottai, S; Bourilkov, D; Bourquin, Maurice; Braccini, S; Branson, J G; Brochu, F; Burger, J D; Burger, W J; Cai, X D; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada, M; Chamizo-Llatas, M; Chang, Y H; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chiefari, G; Cifarelli, Luisa; Cindolo, F; Clare, I; Clare, R; Coignet, G; Colino, N; Costantini, S; de la Cruz, B; Cucciarelli, S; van Dalen, J A; De Asmundis, R; Déglon, P L; Debreczeni, J; Degré, A; Dehmelt, K; Deiters, K; Della Volpe, D; Delmeire, E; Denes, P; De Notaristefani, F; De Salvo, A; Diemoz, M; Dierckxsens, M; Dionisi, C; Dittmar, M; Doria, A; Dova, M T; Duchesneau, D; Duda, M; Echenard, B; Eline, A; El-Hage, A; El-Mamouni, H; Engler, A; Eppling, F J; Extermann, P; Falagán, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, M; Ferguson, T; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, F; Fisher, P H; Fisher, W; Fisk, I; Forconi, G; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gataullin, M; Gentile, S; Giagu, S; Gong, Z F; Grenier, G; Grimm, O; Grünewald, M W; Guida, M; van Gulik, R; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Hirschfelder, J; Hofer, H; Hohlmann, M; Holzner, G; Hou, S R; Hu, Y; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Käfer, D; Kaur, M; Kienzle-Focacci, M N; Kim, J K; Kirkby, Jasper; Kittel, E W; Klimentov, A; König, A C; Kopal, M; Koutsenko, V F; Kräber, M H; Krämer, R W; Krüger, A; Kunin, A; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Le Goff, J M; Leiste, R; Levtchenko, M; Levchenko, P M; Li, C; Likhoded, S; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lü, Y S; Luci, C; Luminari, L; Lustermann, W; Ma Wen Gan; Malgeri, L; Malinin, A; Maña, C; Mans, J; Martin, J P; Marzano, F; Mazumdar, K; McNeil, R R; Mele, S; Merola, L; Meschini, M; Metzger, W J; Mihul, A; Milcent, H; Mirabelli, G; Mnich, J; Mohanty, G B; Muanza, G S; Muijs, A J M; Musicar, B; Musy, M; Nagy, S; Natale, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Nisati, A; Novák, T; Nowak, H; Ofierzynski, R A; Organtini, G; Pal, I; Palomares, C; Paolucci, P; Paramatti, R; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Pedace, M; Pensotti, S; Perret-Gallix, D; Petersen, B; Piccolo, D; Pierella, F; Pioppi, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Pothier, J; Prokofev, D; Prokofiev, D O; Quartieri, J; Rahal-Callot, G; Rahaman, M A; Raics, P; Raja, N; Ramelli, R; Rancoita, P G; Ranieri, R; Raspereza, A V; Razis, P A; Ren, D; Rescigno, M; Reucroft, S; Riemann, S; Riles, K; Roe, B P; Romero, L; Rosca, A; Rosier-Lees, S; Roth, S; Rosenbleck, C; Rubio, J A; Ruggiero, G; Rykaczewski, H; Sakharov, A; Saremi, S; Sarkar, S; Salicio, J; Sánchez, E; Schäfer, C; Shchegelskii, V; Schopper, Herwig Franz; Schotanus, D J; Sciacca, C; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shumilov, E; Shvorob, A V; Son, D; Souga, C; Spillantini, P; Steuer, M; Stickland, D P; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Sushkov, S; Suter, H; Swain, J D; Szillási, Z; Tang, X W; Tarjan, P; Tauscher, Ludwig; Taylor, L; Tellili, B; Teyssier, D; Timmermans, C; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Tully, C; Tung, K L; Ulbricht, J; Valente, E; Van de Walle, R T; Vásquez, R; Veszpremi, V; Vesztergombi, G; Vetlitskii, I; Vicinanza, D; Viertel, Gert M; Villa, S; Vivargent, M; Vlachos, S; Vodopyanov, I; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Wadhwa, M; Wang, Q; Wang, X L; Wang, Z M; Weber, M; Wienemann, P; Wilkens, H; Wynhoff, S; Xia, L; Xu, Z Z; Yamamoto, J; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Yeh, S C; Zalite, A; Zalite, Yu; Zhang, Z P; Zhao, J; Zhu, G Y; Zhu, R Y; Zhuang, H L; Zichichi, A; Zimmermann, B; Zöller, M

    2004-01-01

    A search is performed in symmetric 3-jet hadronic Z decay events for evidence of colour singlet production or colour reconnection effects. Asymmetries in the angular separation of particles are found to be sensitive indicators of such effects. Upper limits on the level of colour singlet production and colour reconnection effects are established for a variety of models.

  16. Fluid Approximation of a Call Center Model with Redials and Reconnects

    NARCIS (Netherlands)

    S. Ding (Sihan); M. Frolkova (Masha); R.D. van der Mei (Rob); A.P. Zwart (Bert)

    2013-01-01

    htmlabstractIn many call centers, callers may call multiple times. Some of the calls are re-attempts after abandonments (redials), and some are re-attempts after connected calls (reconnects). The combination of redials and reconnects has not been considered when making staffing decisions, while

  17. Measurements of nonlinear Hall-driven reconnection in the reversed field pinch

    Science.gov (United States)

    Tharp, Timothy D.

    Complex organisms are able to develop because of the complex regulatory systems that control their gene expression. The first step in this regulation, transcription initiation, is controlled by transcription factors. Transcription factors are modular proteins composed of two distinct domains, the DNA binding domain and the regulatory domain. These molecules are involved in a plethora of important biological processes including embryogenesis, development, cell health, and cancer. Tissue enriched transcription factors Nkx-2.5 and Gata4 are involved in cardiac development and cardiac health. In this thesis the DNA binding specificity of Nkx-2.5 will be analyzed using a high throughput double stranded DNA platform called Cognate Site Identifier (CSI) arrays (Chapter 2). The full DNA binding specificity of Nkx-2.5 and Nkx-2.5 mutants will be visualized using Sequence Specificity Landscapes (SSLs). In Chapter 3, the definition of binding specificity will be investigated by evaluating a number of different DNA binding folds by CSI and SSLs. CSI and SSLs will also be used to evaluate different pyrrole/imidazole hairpin polyamides in order to better characterize these small molecule DNA binding domains. CSI and SSL data will be applied to the genome in order to explain the biological function an artificial transcription factor. Chapter 4 will discuss the mechanism of nonspecific DNA binding. The historical means of predicting DNA binding will be challenged by utilizing high throughput experiments. The effect of salt concentration on both specific and nonspecific binding will also be investigated. Finally, in Chapter 5, a generation of Protein DNA Dimerizer will be discussed. A PDD that regulates transcription on genomic DNA by binding cooperatively with the heart IF Gata4 will be characterized. These studies provide understanding of, and a means to control, how transcription factors sample the endless sea of DNA in the genome in order to regulate gene expression with such wonderful specificity.

  18. Fast magnetic-field annihilation in the relativistic collisionless regime driven by two ultrashort high-intensity laser pulses

    Czech Academy of Sciences Publication Activity Database

    Gu, Yanjun; Klimo, Ondřej; Kumar, D.; Liu, Y.; Singh, Sushil K.; Esirkepov, T.Z.; Bulanov, S.V.; Weber, Stefan A.; Korn, Georg

    2016-01-01

    Roč. 93, č. 1 (2016), 1-6, č. článku 013203. ISSN 1539-3755 R&D Projects: GA MŠk EF15_008/0000162 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : plasma * acceleration Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.288, year: 2014

  19. GENESIS OF INTERPLANETARY INTERMITTENT TURBULENCE: A CASE STUDY OF ROPE–ROPE MAGNETIC RECONNECTION

    Energy Technology Data Exchange (ETDEWEB)

    Chian, Abraham C.-L.; Loew, Murray H. [Department of Biomedical Engineering, George Washington University, Washington, DC 20052 (United States); Feng, Heng Q. [Institute of Space Physics, Luoyang Normal University, Luoyang (China); Hu, Qiang [Department of Space Science and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Miranda, Rodrigo A. [UnB-Gama Campus, and Plasma Physics Laboratory, Institute of Physics, University of Brasília (UnB), Brasília DF 70910-900 (Brazil); Muñoz, Pablo R. [Department of Physics and Astronomy, University of La Serena, Av. Juan Cisternas 1200, La Serena (Chile); Sibeck, David G. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Wu, De J., E-mail: abraham.chian@gmail.com [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

    2016-12-01

    In a recent paper, the relation between current sheet, magnetic reconnection, and turbulence at the leading edge of an interplanetary coronal mass ejection was studied. We report here the observation of magnetic reconnection at the interface region of two interplanetary magnetic flux ropes. The front and rear boundary layers of three interplanetary magnetic flux ropes are identified, and the structures of magnetic flux ropes are reconstructed by the Grad–Shafranov method. A quantitative analysis of the reconnection condition and the degree of intermittency reveals that rope–rope magnetic reconnection is the most likely site for genesis of interplanetary intermittency turbulence in this event. The dynamic pressure pulse resulting from this reconnection triggers the onset of a geomagnetic storm.

  20. Thick Escaping Magnetospheric Ion Layer in Magnetopause Reconnection with MMS Observations

    Science.gov (United States)

    Nagai, T.; Kitamura, N.; Hasagawa, H.; Shinohara, I.; Yokota, S.; Saito, Y.; Nakamura, R.; Giles, B. L.; Pollock, C.; Moore, T. E.; hide

    2016-01-01

    The structure of asymmetric magnetopause reconnection is explored with multiple point and high-time-resolution ion velocity distribution observations from the Magnetospheric Multiscale mission. On 9 September 2015, reconnection took place at the magnetopause, which separated the magnetosheath and the magnetosphere with a density ratio of 25:2. The magnetic field intensity was rather constant, even higher in the asymptotic magnetosheath. The reconnected field line region had a width of approximately 540 km. In this region, streaming and gyrating ions are discriminated. The large extension of the reconnected field line region toward the magnetosheath can be identified where a thick layer of escaping magnetospheric ions was formed. The scale of the magnetosheath side of the reconnected field line region relative to the scale of its magnetospheric side was 4.5:1.

  1. Scaling laws of resistive magnetohydrodynamic reconnection in the high-Lundquist-number, plasmoid-unstable regime

    International Nuclear Information System (INIS)

    Huang Yimin; Bhattacharjee, A.

    2010-01-01

    The Sweet-Parker layer in a system that exceeds a critical value of the Lundquist number (S) is unstable to the plasmoid instability. In this paper, a numerical scaling study has been done with an island coalescing system driven by a low level of random noise. In the early stage, a primary Sweet-Parker layer forms between the two coalescing islands. The primary Sweet-Parker layer breaks into multiple plasmoids and even thinner current sheets through multiple levels of cascading if the Lundquist number is greater than a critical value S c ≅4x10 4 . As a result of the plasmoid instability, the system realizes a fast nonlinear reconnection rate that is nearly independent of S, and is only weakly dependent on the level of noise. The number of plasmoids in the linear regime is found to scales as S 3/8 , as predicted by an earlier asymptotic analysis [N. F. Loureiro et al., Phys. Plasmas 14, 100703 (2007)]. In the nonlinear regime, the number of plasmoids follows a steeper scaling, and is proportional to S. The thickness and length of current sheets are found to scale as S -1 , and the local current densities of current sheets scale as S -1 . Heuristic arguments are given in support of theses scaling relations.

  2. Kinetic physics in exhausts formed by guide field reconnection within the magnetosheath, as observed by MMS

    Science.gov (United States)

    Mistry, R.; Eastwood, J. P.; Phan, T.; Cassak, P.; Shay, M. A.; Haggerty, C. C.; Oieroset, M.; Goldman, M. V.; Giles, B. L.; Gershman, D. J.; Paterson, W. R.; Russell, C. T.; Lindqvist, P. A.; Ergun, R.; Torbert, R. B.; Burch, J. L.; Zhao, C.; Strangeway, R. J.

    2016-12-01

    MMS has allowed, for the first time, particle observations of reconnection to be made on ion and electron scales. These extremely high resolution measurements can be used to investigate the kinetic physics of reconnection that are known to be essential to the dissipation mechanisms at play in the diffusion region. Kinetic effects, however, are not limited to the diffusion region, and both simulations and observations have shown that kinetic processes can occur in the exhaust region downstream of the reconnection site. Whilst the primary targets of MMS are reconnection at the magnetopause and magnetotail, excursions of the spacecraft into the magnetosheath allow for observations in the less frequently accessible reconnection regime of symmetric reconnection with large guide fields. Here we present MMS observations of magnetosheath reconnection exhausts made approximately 75 ion inertial lengths downstream of the X-line. These exhausts are observed in the magnetosheath-proper, and as such have relatively symmetric inflow conditions. Furthermore, these exhausts have guide fields of a strength comparable to that of the reconnecting magnetic field. We use high resolution MMS observations of these events to study the effects of guide fields on the exhausts that form in symmetric reconnection. We find that non-uniform electron heating which occurs near the X-line in the presence of a guide field persists downstream, at least to the distance of these observations. Additionally, the electron velocity is resolved below the ion kinetic scale, where it is highly disrupted compared to the case of anti-parallel reconnection, with narrow field-aligned electron flows towards the X-line. These flows result in the generation of Hall currents and magnetic fields within the exhaust region itself, allowing Hall effects to persist beyond the ion diffusion region. The effects of the guide field on counter-streaming ion beams within the exhaust are also presented, as well as brief periods

  3. Utility reconnection services : a new threat to vulnerable consumers?

    International Nuclear Information System (INIS)

    Lott, S.

    2002-10-01

    The current status of deregulation or restructuring of the energy and telecommunications sector in Canada and the United States was examined along with its impact on low-income consumers. In particular, this report examined the electricity, natural gas and telephone utilities and the extent to which reconnection services have emerged in Canada. With deregulation and utility restructuring, investment and pricing decisions are made according to market forces and competition. The core functions of the utility are unbundled into generation, transmission and distribution functions. The main impact on residential consumers is that their source of supply may change. This report also examined the regulatory responses to utility reconnection services and the impact of market segmentation in the energy sector. It focused on Canada's legislative framework that protects vulnerable consumers. It also examined the federal regulatory role in energy and telecommunications, siting Ontario as an example. It was noted that the experience in the United States with market segmentation and its negative impact on vulnerable consumers should provide some warnings for Canada. 75 refs

  4. BREAKOUT RECONNECTION OBSERVED BY THE TESIS EUV TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Reva, A. A.; Ulyanov, A. S.; Shestov, S. V.; Kuzin, S. V., E-mail: reva.antoine@gmail.com [Lebedev Physical Institute, Russian Academy of Sciences (Russian Federation)

    2016-01-10

    We present experimental evidence of the coronal mass ejection (CME) breakout reconnection, observed by the TESIS EUV telescope. The telescope could observe solar corona up to 2 R{sub ⊙} from the Sun center in the Fe 171 Å line. Starting from 2009 April 8, TESIS observed an active region (AR) that had a quadrupolar structure with an X-point 0.5 R{sub ⊙} above photosphere. A magnetic field reconstructed from the Michelson Doppler Imager data also has a multipolar structure with an X-point above the AR. At 21:45 UT on April 9, the loops near the X-point started to move away from each other with a velocity of ≈7 km s{sup −1}. At 01:15 UT on April 10, a bright stripe appeared between the loops, and the flux in the GOES 0.5–4 Å channel increased. We interpret the loops’ sideways motion and the bright stripe as evidence of the breakout reconnection. At 01:45 UT, the loops below the X-point started to slowly move up. At 15:10 UT, the CME started to accelerate impulsively, while at the same time a flare arcade formed below the CME. After 15:50 UT, the CME moved with constant velocity. The CME evolution precisely followed the breakout model scenario.

  5. Breakout Reconnection Observed by the TESIS EUV Telescope

    Science.gov (United States)

    Reva, A. A.; Ulyanov, A. S.; Shestov, S. V.; Kuzin, S. V.

    2016-01-01

    We present experimental evidence of the coronal mass ejection (CME) breakout reconnection, observed by the TESIS EUV telescope. The telescope could observe solar corona up to 2 R⊙ from the Sun center in the Fe 171 Å line. Starting from 2009 April 8, TESIS observed an active region (AR) that had a quadrupolar structure with an X-point 0.5 R⊙ above photosphere. A magnetic field reconstructed from the Michelson Doppler Imager data also has a multipolar structure with an X-point above the AR. At 21:45 UT on April 9, the loops near the X-point started to move away from each other with a velocity of ≈7 km s-1. At 01:15 UT on April 10, a bright stripe appeared between the loops, and the flux in the GOES 0.5-4 Å channel increased. We interpret the loops’ sideways motion and the bright stripe as evidence of the breakout reconnection. At 01:45 UT, the loops below the X-point started to slowly move up. At 15:10 UT, the CME started to accelerate impulsively, while at the same time a flare arcade formed below the CME. After 15:50 UT, the CME moved with constant velocity. The CME evolution precisely followed the breakout model scenario.

  6. BREAKOUT RECONNECTION OBSERVED BY THE TESIS EUV TELESCOPE

    International Nuclear Information System (INIS)

    Reva, A. A.; Ulyanov, A. S.; Shestov, S. V.; Kuzin, S. V.

    2016-01-01

    We present experimental evidence of the coronal mass ejection (CME) breakout reconnection, observed by the TESIS EUV telescope. The telescope could observe solar corona up to 2 R ⊙ from the Sun center in the Fe 171 Å line. Starting from 2009 April 8, TESIS observed an active region (AR) that had a quadrupolar structure with an X-point 0.5 R ⊙ above photosphere. A magnetic field reconstructed from the Michelson Doppler Imager data also has a multipolar structure with an X-point above the AR. At 21:45 UT on April 9, the loops near the X-point started to move away from each other with a velocity of ≈7 km s −1 . At 01:15 UT on April 10, a bright stripe appeared between the loops, and the flux in the GOES 0.5–4 Å channel increased. We interpret the loops’ sideways motion and the bright stripe as evidence of the breakout reconnection. At 01:45 UT, the loops below the X-point started to slowly move up. At 15:10 UT, the CME started to accelerate impulsively, while at the same time a flare arcade formed below the CME. After 15:50 UT, the CME moved with constant velocity. The CME evolution precisely followed the breakout model scenario

  7. Stability analysis of Kamimura-Dawson diffusion in a collisionless plasma

    International Nuclear Information System (INIS)

    Berryman, J.G.

    1983-01-01

    It has been predicted theoretically and observed experimentally that the cross-field particle diffusion coefficient is inversely proportional to density for a highly collisionless plasma in the presence of a sheared magnetic field. The asymptotic solution of the corresponding one-dimensional model equation n/sub t/ = [ln(n/n 0 )]/sub x/x on 0 0 is shown to have the form ln(n/n 0 ) = epsilon2/sup 1/2/ sin πx+epsilon 2 psi 2 (x)+epsilon 3psi 3 (x)+0(epsilon 4 ) where epsilon = A exp(-π 2 t/n 0 ), psi 2 and psi 3 are known functions, and the amplitude A alone is dependent on the initial data. The asymptotic behavior of the particle distribution can therefore be predicted from knowledge of the distribution at some earlier time

  8. Dynamic structure factor of the normal Fermi gas from the collisionless to the hydrodynamic regime

    International Nuclear Information System (INIS)

    Watabe, Shohei; Nikuni, Tetsuro

    2010-01-01

    The dynamic structure factor of a normal Fermi gas is investigated by using the moment method for the Boltzmann equation. We determine the spectral function at finite temperatures over the full range of crossover from the collisionless regime to the hydrodynamic regime. We find that the Brillouin peak in the dynamic structure factor exhibits a smooth crossover from zero to first sound as functions of temperature and interaction strength. The dynamic structure factor obtained using the moment method also exhibits a definite Rayleigh peak (ω∼0), which is a characteristic of the hydrodynamic regime. We compare the dynamic structure factor obtained by the moment method with that obtained from the hydrodynamic equations.

  9. Low Mach-number collisionless electrostatic shocks and associated ion acceleration

    Science.gov (United States)

    Pusztai, I.; TenBarge, J. M.; Csapó, A. N.; Juno, J.; Hakim, A.; Yi, L.; Fülöp, T.

    2018-03-01

    The existence and properties of low Mach-number (M≳ 1) electrostatic collisionless shocks are investigated with a semi-analytical solution for the shock structure. We show that the properties of the shock obtained in the semi-analytical model can be well reproduced in fully kinetic Eulerian Vlasov-Poisson simulations, where the shock is generated by the decay of an initial density discontinuity. Using this semi-analytical model, we study the effect of the electron-to-ion temperature ratio and the presence of impurities on both the maximum shock potential and the Mach number. We find that even a small amount of impurities can influence the shock properties significantly, including the reflected light ion fraction, which can change several orders of magnitude. Electrostatic shocks in heavy ion plasmas reflect most of the hydrogen impurity ions.

  10. Tree Particle-Mesh: An Adaptive, Efficient, and Parallel Code for Collisionless Cosmological Simulation

    Science.gov (United States)

    Bode, Paul; Ostriker, Jeremiah P.

    2003-03-01

    An improved implementation of an N-body code for simulating collisionless cosmological dynamics is presented. TPM (tree particle-mesh) combines the PM method on large scales with a tree code to handle particle-particle interactions at small separations. After the global PM forces are calculated, spatially distinct regions above a given density contrast are located; the tree code calculates the gravitational interactions inside these denser objects at higher spatial and temporal resolution. The new implementation includes individual particle time steps within trees, an improved treatment of tidal forces on trees, new criteria for higher force resolution and choice of time step, and parallel treatment of large trees. TPM is compared to P3M and a tree code (GADGET) and is found to give equivalent results in significantly less time. The implementation is highly portable (requiring a FORTRAN compiler and MPI) and efficient on parallel machines. The source code can be found on the World Wide Web.

  11. Collisionless damping of perpendicular magnetosonic pulses in a two-ion-species plasma

    International Nuclear Information System (INIS)

    Dogen, Daiju; Toida, Mieko; Ohsawa, Yukiharu

    1998-01-01

    One dimensional electromagnetic simulation code based on a three-fluid model is used to study evolution of perpendicular magnetosonic pulses in a two-ion-species plasma. A magnetosonic pulse accelerates heavy ions in the direction parallel to the wave front, which results in the excitation of a long-wavelength perturbation behind the original pulse. Thus the original pulse is damped even if the plasma is collisionless and the pulse amplitude is small. The damping rate of a solitary pulse is theoretically obtained. It decreases with increasing amplitude. The theory is in good agreement with the simulation result. Also, it is confirmed that small-amplitude periodic waves are not damped. (author)

  12. Linear Stability Analysis of a Collisionless Distribution Function for the Force-Free Harris Sheet

    Science.gov (United States)

    Wilson, Fiona; Neukirch, Thomas

    2013-04-01

    A discussion is presented of the first linear stability analysis of the collisionless distribution function recently found by Harrison and Neukirch for the force-free Harris sheet (Physical Review Letters 102, 135003, 2009). Macroscopic instabilities are considered, and the perturbations are assumed to be two-dimensional only. The stability analysis is based on the technique of integration over unperturbed orbits. Similarly to the Harris sheet case (Nuovo Cimento, 23:115, 1962), this is only possible by using approximations to the exact orbits, which are unknown. Furthermore, the approximations for the Harris sheet case cannot be used for the force-free Harris sheet, and so new techniques have to be developed in order to make analytical progress. In addition to the full problem, the long wavelength limit is considered, and the results of the two cases are compared. The dependence of the stability on various equilibrium parameters is investigated.

  13. Optical pyrometer system for collisionless shock experiments in high-power laser-produced plasmas.

    Science.gov (United States)

    Morita, T; Sakawa, Y; Kuramitsu, Y; Dono, S; Ide, T; Shibata, S; Aoki, H; Tanji, H; Sano, T; Shiroshita, A; Waugh, J N; Gregory, C D; Woolsey, N C; Takabe, H

    2012-10-01

    A temporally and spatially resolved optical pyrometer system has been fielded on Gekko XII experiments. The system is based on the self-emission measurements with a gated optical imager (GOI) and a streaked optical pyrometer (SOP). Both detectors measure the intensity of the self-emission from laser-produced plasmas at the wavelength of 450 nm with a bandpass filter with a width of ~10 nm in FWHM. The measurements were calibrated with different methods, and both results agreed with each other within 30% as previously reported [T. Morita et al., Astrophys. Space Sci. 336, 283 (2011)]. As a tool for measuring the properties of low-density plasmas, the system is applicable for the measurements of the electron temperature and density in collisionless shock experiments [Y. Kuramitsu et al., Phys. Rev. Lett. 106, 175002 (2011)].

  14. Electrostatic potential in a collisionless plasma flow along open magnetic field lines

    International Nuclear Information System (INIS)

    Sato, Kunihiro; Katayama, Hideaki; Miyawaki, Fujio

    1992-06-01

    Formation of the steady-state potential in a collisionless plasma flow along nonuniform magnetic field lines terminated at a wall is studied theoretically under the condition that a particle source in a plasma can be neglected. It is found that the plasma flow is required to satisfy the generalized Bohm criterion over the whole region for the formation of the steady-state continuous potential in the divergent magnetic field. A monotonically falling potential can build up from the inside of the magnetic throat to the wall only if the Bohm criterion is marginally satisfied at the throat. Numerical solutions to Poisson's equation show that a potential profile outside the throat is strongly dependent upon the particle density of electrons trapped between the throat and the wall. Controllability of the potential by increasing the trapped-electron density is discussed briefly. (author)

  15. Collisionless energy absorption in the short-pulse intense laser-cluster interaction

    International Nuclear Information System (INIS)

    Kundu, M.; Bauer, D.

    2006-01-01

    In a previous paper [Phys. Rev. Lett. 96, 123401 (2006)] we have shown by means of three-dimensional particle-in-cell simulations and a simple rigid-sphere model that nonlinear resonance absorption is the dominant collisionless absorption mechanism in the intense, short-pulse laser cluster interaction. In this paper we present a more detailed account of the matter. In particular we show that the absorption efficiency is almost independent of the laser polarization. In the rigid-sphere model, the absorbed energy increases by many orders of magnitude at a certain threshold laser intensity. The particle-in-cell results display maximum fractional absorption around the same intensity. We calculate the threshold intensity and show that it is underestimated by the common overbarrier ionization estimate

  16. Collisionless pitch angle scattering of plasma ions at the edge region of an FRC

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Toshiki; Tomita, Yukihiro; Momota, Hiromu [National Inst. for Fusion Science, Toki, Gifu (Japan); Shabrov, N.V.

    1997-07-01

    Motion of a plasma ion gyrating around the separatrix of a field-reversed configuration is studied. Numerical studies showed that action integral of a particle changes abruptly when a particle passes through the vicinity of a field null x-point. This phenomena is understood as collisionless stochastic scattering of pitch angle. In case of a particle with positive canonical angular momentum P{sub {theta}}, resultant correlation coefficients of action integral between before and after the scattering appear to be stochastic in some cases. As action integral increases for a particle with negative P{sub {theta}}, its motion tends to be adiabatic. If negative P{sub {theta}} of a particle approaches to zero, a stochastic motion is observed. (author)

  17. Phase space simulation of collisionless stellar systems on the massively parallel processor

    International Nuclear Information System (INIS)

    White, R.L.

    1987-01-01

    A numerical technique for solving the collisionless Boltzmann equation describing the time evolution of a self gravitating fluid in phase space was implemented on the Massively Parallel Processor (MPP). The code performs calculations for a two dimensional phase space grid (with one space and one velocity dimension). Some results from calculations are presented. The execution speed of the code is comparable to the speed of a single processor of a Cray-XMP. Advantages and disadvantages of the MPP architecture for this type of problem are discussed. The nearest neighbor connectivity of the MPP array does not pose a significant obstacle. Future MPP-like machines should have much more local memory and easier access to staging memory and disks in order to be effective for this type of problem

  18. Magnetic field amplification and evolution in turbulent collisionless magnetohydrodynamics: An application to the intracluster medium

    Energy Technology Data Exchange (ETDEWEB)

    Santos-Lima, R.; De Gouveia Dal Pino, E. M.; Kowal, G. [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, R. do Matão, 1226, São Paulo, SP 05508-090 (Brazil); Falceta-Gonçalves, D. [Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Rua Arlindo Bettio, 1000, São Paulo, SP 03828-000 (Brazil); Lazarian, A. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Nakwacki, M. S. [Instituto de Astronomía y Física del Espacio (IAFE), CONICET (Argentina)

    2014-02-01

    The amplification of magnetic fields (MFs) in the intracluster medium (ICM) is attributed to turbulent dynamo (TD) action, which is generally derived in the collisional-MHD framework. However, this assumption is poorly justified a priori, since in the ICM the ion mean free path between collisions is of the order of the dynamical scales, thus requiring a collisionless MHD description. The present study uses an anisotropic plasma pressure that brings the plasma within a parametric space where collisionless instabilities take place. In this model, a relaxation term of the pressure anisotropy simulates the feedback of the mirror and firehose instabilities, in consistency with empirical studies. Our three-dimensional numerical simulations of forced transonic turbulence, aiming the modeling of the turbulent ICM, were performed for different initial values of the MF intensity and different relaxation rates of the pressure anisotropy. We found that in the high-β plasma regime corresponding to the ICM conditions, a fast anisotropy relaxation rate gives results that are similar to the collisional-MHD model, as far as the statistical properties of the turbulence are concerned. Also, the TD amplification of seed MFs was found to be similar to the collisional-MHD model. The simulations that do not employ the anisotropy relaxation deviate significantly from the collisional-MHD results and show more power at the small-scale fluctuations of both density and velocity as a result of the action of the instabilities. For these simulations, the large-scale fluctuations in the MF are mostly suppressed and the TD fails in amplifying seed MFs.

  19. Low Altitude Solar Magnetic Reconnection, Type III Solar Radio Bursts, and X-ray Emissions.

    Science.gov (United States)

    Cairns, I H; Lobzin, V V; Donea, A; Tingay, S J; McCauley, P I; Oberoi, D; Duffin, R T; Reiner, M J; Hurley-Walker, N; Kudryavtseva, N A; Melrose, D B; Harding, J C; Bernardi, G; Bowman, J D; Cappallo, R J; Corey, B E; Deshpande, A; Emrich, D; Goeke, R; Hazelton, B J; Johnston-Hollitt, M; Kaplan, D L; Kasper, J C; Kratzenberg, E; Lonsdale, C J; Lynch, M J; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Ord, S M; Prabu, T; Roshi, A; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Wayth, R B; Waterson, M; Webster, R L; Whitney, A R; Williams, A; Williams, C L

    2018-01-26

    Type III solar radio bursts are the Sun's most intense and frequent nonthermal radio emissions. They involve two critical problems in astrophysics, plasma physics, and space physics: how collective processes produce nonthermal radiation and how magnetic reconnection occurs and changes magnetic energy into kinetic energy. Here magnetic reconnection events are identified definitively in Solar Dynamics Observatory UV-EUV data, with strong upward and downward pairs of jets, current sheets, and cusp-like geometries on top of time-varying magnetic loops, and strong outflows along pairs of open magnetic field lines. Type III bursts imaged by the Murchison Widefield Array and detected by the Learmonth radiospectrograph and STEREO B spacecraft are demonstrated to be in very good temporal and spatial coincidence with specific reconnection events and with bursts of X-rays detected by the RHESSI spacecraft. The reconnection sites are low, near heights of 5-10 Mm. These images and event timings provide the long-desired direct evidence that semi-relativistic electrons energized in magnetic reconnection regions produce type III radio bursts. Not all the observed reconnection events produce X-ray events or coronal or interplanetary type III bursts; thus different special conditions exist for electrons leaving reconnection regions to produce observable radio, EUV, UV, and X-ray bursts.

  20. The Properties of Reconnection Current Sheets in GRMHD Simulations of Radiatively Inefficient Accretion Flows

    Science.gov (United States)

    Ball, David; Özel, Feryal; Psaltis, Dimitrios; Chan, Chi-Kwan; Sironi, Lorenzo

    2018-02-01

    Non-ideal magnetohydrodynamic (MHD) effects may play a significant role in determining the dynamics, thermal properties, and observational signatures of radiatively inefficient accretion flows onto black holes. In particular, particle acceleration during magnetic reconnection events may influence black hole spectra and flaring properties. We use representative general relativistic magnetohydrodynamic (GRMHD) simulations of black hole accretion flows to identify and explore the structures and properties of current sheets as potential sites of magnetic reconnection. In the case of standard and normal evolution (SANE) disks, we find that in the reconnection sites, the plasma beta ranges from 0.1 to 1000, the magnetization ranges from 10‑4 to 1, and the guide fields are weak compared with the reconnecting fields. In magnetically arrested (MAD) disks, we find typical values for plasma beta from 10‑2 to 103, magnetizations from 10‑3 to 10, and typically stronger guide fields, with strengths comparable to or greater than the reconnecting fields. These are critical parameters that govern the electron energy distribution resulting from magnetic reconnection and can be used in the context of plasma simulations to provide microphysics inputs to global simulations. We also find that ample magnetic energy is available in the reconnection regions to power the fluence of bright X-ray flares observed from the black hole in the center of the Milky Way.

  1. Observing Formation of Flux Rope by Tether-cutting Reconnection in the Sun

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Zhike; Yan, Xiaoli; Yang, Liheng; Wang, Jincheng; Zhao, Li, E-mail: zkxue@ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences, Kunming Yunnan 650216 (China)

    2017-05-10

    Tether-cutting reconnection is considered as one mechanism for the formation of a flux rope. It has been proposed for more than 30 years; however, so far, direct observations of it are very rare. In this Letter, we present observations of the formation of a flux rope via tether-cutting reconnection in NOAA AR 11967 on 2014 February 2 by combining observations with the New Vacuum Solar Telescope and the Solar Dynamic Observatory . The tether-cutting reconnection occurs between two sets of highly sheared magnetic arcades. Comprehensive observational evidence of the reconnection is as follows: changes of the connections between the arcades, brightenings at the reconnection site, hot outflows, formation of a flux rope, slow-rise motion of the flux rope, and flux cancelation. The outflows are along three directions from the reconnection site to the footpoints with the velocities from 24 ± 1 km s{sup −1} to 69 ± 5 km s{sup −1}. Additionally, it is found that the newly formed flux rope connects far footpoints and has a left-handed twisted structure with many fine threads and a concave-up-shape structure in the middle. All the observations are in agreement with the tether-cutting model and provide evidence that tether-cutting reconnection leads to the formation of the flux rope associated with flux shear flow and cancelation.

  2. Detecting Spectroscopic Signatures of Magnetic Reconnection Along the Boundary of Coronal Holes

    Science.gov (United States)

    Wendeln, C. N.; Landi, E.

    2017-12-01

    Magnetic reconnection is an essential release mechanism of energy proposed for the highly variable solar wind and plays a direct role in leading to many astrophysical phenomena such as space weather events. Reconnection between open and closed magnetic field lines (i.e. along the boundary of coronal holes) releases coronal loop plasma into the heliosphere as the reconfiguration of the magnetic field accelerates plasma along two reconnection beams. In this investigation we will look for spectral signatures of reconnection occurring along the edges of coronal holes using observations from the EUV Imaging Spectrometer (EIS) onboard Hinode. We will use a novel direct observational method, which we have developed, for detecting magnetic reconnection in the solar atmosphere. Furthermore we will provide a constraint on the energetics at which reconnection occurs. Our preliminary results indicates the presence of spectral lines due to a magnetic reconnection event. Moreover, our preliminary diagnostics indicates that the amount of stray light contamination for the EIS instrument is greater than previously measured.

  3. Electron cyclotron maser instability (ECMI in strong magnetic guide field reconnection

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2017-08-01

    Full Text Available The ECMI model of electromagnetic radiation from electron holes is shown to be applicable to spontaneous magnetic reconnection. We apply it to reconnection in strong current-aligned magnetic guide fields. Such guide fields participate only passively in reconnection, which occurs in the antiparallel components to both sides of the guide-field-aligned current sheets with current carried by kinetic Alfvén waves. Reconnection generates long (the order of hundreds of electron inertial scales electron exhaust regions at the reconnection site X point, which are extended perpendicular to the current and the guide fields. Exhausts contain a strongly density-depleted hot electron component and have properties similar to electron holes. Exhaust electron momentum space distributions are highly deformed, exhibiting steep gradients transverse to both the reconnecting and guide fields. Such properties suggest application of the ECMI mechanism with the fundamental ECMI X-mode emission beneath the nonrelativistic guide field cyclotron frequency in localized source regions. An outline of the mechanism and its prospects is given. Potential applications are the kilometric radiation (AKR in auroral physics, solar radio emissions during flares, planetary emissions and astrophysical scenarios (radiation from stars and compact objects involving the presence of strong magnetic fields and field-aligned currents. Drift of the exhausts along the guide field maps the local field and plasma properties. Escape of radiation from the exhaust and radiation source region still poses a problem. The mechanism can be studied in 2-D particle simulations of strong guide field reconnection which favours 2-D, mapping the deformation of the electron distribution perpendicular to the guide field, and using it in the numerical calculation of the ECMI growth rate. The mechanism suggests also that reconnection in general may become a source of the ECMI with or without guide fields. This is

  4. Electron cyclotron maser instability (ECMI) in strong magnetic guide field reconnection

    Science.gov (United States)

    Treumann, Rudolf A.; Baumjohann, Wolfgang

    2017-08-01

    The ECMI model of electromagnetic radiation from electron holes is shown to be applicable to spontaneous magnetic reconnection. We apply it to reconnection in strong current-aligned magnetic guide fields. Such guide fields participate only passively in reconnection, which occurs in the antiparallel components to both sides of the guide-field-aligned current sheets with current carried by kinetic Alfvén waves. Reconnection generates long (the order of hundreds of electron inertial scales) electron exhaust regions at the reconnection site X point, which are extended perpendicular to the current and the guide fields. Exhausts contain a strongly density-depleted hot electron component and have properties similar to electron holes. Exhaust electron momentum space distributions are highly deformed, exhibiting steep gradients transverse to both the reconnecting and guide fields. Such properties suggest application of the ECMI mechanism with the fundamental ECMI X-mode emission beneath the nonrelativistic guide field cyclotron frequency in localized source regions. An outline of the mechanism and its prospects is given. Potential applications are the kilometric radiation (AKR) in auroral physics, solar radio emissions during flares, planetary emissions and astrophysical scenarios (radiation from stars and compact objects) involving the presence of strong magnetic fields and field-aligned currents. Drift of the exhausts along the guide field maps the local field and plasma properties. Escape of radiation from the exhaust and radiation source region still poses a problem. The mechanism can be studied in 2-D particle simulations of strong guide field reconnection which favours 2-D, mapping the deformation of the electron distribution perpendicular to the guide field, and using it in the numerical calculation of the ECMI growth rate. The mechanism suggests also that reconnection in general may become a source of the ECMI with or without guide fields. This is of particular

  5. Spacecraft Observations and Analytic Theory of Crescent-Shaped Electron Distributions in Asymmetric Magnetic Reconnection

    Science.gov (United States)

    Egedal, J.; Le, A.; Daughton, W.; Wetherton, B.; Cassak, P. A.; Chen, L.-J.; Lavraud, B.; Torbert, R. B.; Dorelli, J.; Gershman, D. J.; Avanov, L. A.

    2016-10-01

    Supported by a kinetic simulation, we derive an exclusion energy parameter EX providing a lower kinetic energy bound for an electron to cross from one inflow region to the other during magnetic reconnection. As by a Maxwell demon, only high-energy electrons are permitted to cross the inner reconnection region, setting the electron distribution function observed along the low-density side separatrix during asymmetric reconnection. The analytic model accounts for the two distinct flavors of crescent-shaped electron distributions observed by spacecraft in a thin boundary layer along the low-density separatrix.

  6. Noise-enhanced categorization in a recurrently reconnected neural network

    Science.gov (United States)

    Monterola, Christopher; Zapotocky, Martin

    2005-03-01

    We investigate the interplay of recurrence and noise in neural networks trained to categorize spatial patterns of neural activity. We develop the following procedure to demonstrate how, in the presence of noise, the introduction of recurrence permits to significantly extend and homogenize the operating range of a feed-forward neural network. We first train a two-level perceptron in the absence of noise. Following training, we identify the input and output units of the feed-forward network, and thus convert it into a two-layer recurrent network. We show that the performance of the reconnected network has features reminiscent of nondynamic stochastic resonance: the addition of noise enables the network to correctly categorize stimuli of subthreshold strength, with optimal noise magnitude significantly exceeding the stimulus strength. We characterize the dynamics leading to this effect and contrast it to the behavior of a more simple associative memory network in which noise-mediated categorization fails.

  7. Noise-enhanced categorization in a recurrently reconnected neural network

    International Nuclear Information System (INIS)

    Monterola, Christopher; Zapotocky, Martin

    2005-01-01

    We investigate the interplay of recurrence and noise in neural networks trained to categorize spatial patterns of neural activity. We develop the following procedure to demonstrate how, in the presence of noise, the introduction of recurrence permits to significantly extend and homogenize the operating range of a feed-forward neural network. We first train a two-level perceptron in the absence of noise. Following training, we identify the input and output units of the feed-forward network, and thus convert it into a two-layer recurrent network. We show that the performance of the reconnected network has features reminiscent of nondynamic stochastic resonance: the addition of noise enables the network to correctly categorize stimuli of subthreshold strength, with optimal noise magnitude significantly exceeding the stimulus strength. We characterize the dynamics leading to this effect and contrast it to the behavior of a more simple associative memory network in which noise-mediated categorization fails

  8. Confronting the challenges in reconnecting urban planning and public health.

    Science.gov (United States)

    Corburn, Jason

    2004-04-01

    Although public health and urban planning emerged with the common goal of preventing urban outbreaks of infectious disease, there is little overlap between the fields today. The separation of the fields has contributed to uncoordinated efforts to address the health of urban populations and a general failure to recognize the links between, for example, the built environment and health disparities facing low-income populations and people of color. I review the historic connections and lack thereof between urban planning and public health, highlight some challenges facing efforts to recouple the fields, and suggest that insights from ecosocial theory and environmental justice offer a preliminary framework for reconnecting the fields around a social justice agenda.

  9. On acceleration of plasmoids in magnetohydrodynamic simulations of magnetotail reconnection

    International Nuclear Information System (INIS)

    Scholer, M.; Hautz, R.

    1991-01-01

    The formation and acceleration of plasmoids is investigated by two-dimensional magnetohydrodynamic simulations. The initial equilibrium contains a plasma sheet with a northward magnetic field (B z ) component and a tailward pressure gradient. Reconnection is initiated by three different methods: Case A, a constant resistivity is applied everywhere and a tearing mode evolves, case B, a spatially localized resistivity is fixed in the near-Earth region, and case C, the resistivity is allowed to depend on the electrical current density. In case A, the authors obtain the same results as have been presented by Otto et al. (1990): the tearing instability releases the tension of the closed field lines so that the inherent pressure gradient of the two-dimensional system is not balanced anymore. The pressure gradient then sets the plasmoid into motion. Any sling-shot effect of open magnetic field lines is of minor importance. A completely different behavior has been found in cases B and C. In these cases the high-speed flow in the wedge-shaped region tailward of the near-Earth neutral line pushes against the detached plasmoid and drives it tailward. The ideal terms contributing to the acceleration are still only the pressure and the magnetic field term. However, in these cases the pressure is due to the dynamic pressure of the fast outflow from the reconnection region. The outflow in the wedge-shaped region on both sides of the neutral line is due to acceleration of plasma by tangential magnetic stresses at the slow mode shocks extending form the X line

  10. MMS Observations of Large Guide Field Symmetric Reconnection Between Colliding Reconnection Jets at the Center of a Magnetic Flux Rope at the Magnetopause

    Science.gov (United States)

    Oieroset, M.; Phan, T. D.; Haggerty, C.; Shay, M. A.; Eastwood, J. P.; Gershman, D. J.; Drake, J. F.; Fujimoto, M.; Ergun, R. E.; Mozer, F. S.; hide

    2016-01-01

    We report evidence for reconnection between colliding reconnection jets in a compressed current sheet at the center of a magnetic flux rope at Earth's magnetopause. The reconnection involved nearly symmetric Inflow boundary conditions with a strong guide field of two. The thin (2.5 ion-skin depth (d(sub i) width) current sheet (at approximately 12 d(sub i) downstream of the X line) was well resolved by MMS, which revealed large asymmetries in plasma and field structures in the exhaust. Ion perpendicular heating, electron parallel heating, and density compression occurred on one side of the exhaust, while ion parallel heating and density depression were shifted to the other side. The normal electric field and double out-of-plane (bifurcated) currents spanned almost the entire exhaust. These observations are in good agreement with a kinetic simulation for similar boundary conditions, demonstrating in new detail that the structure of large guide field symmetric reconnection is distinctly different from antiparallel reconnection.

  11. Compton harmonic resonances, stochastic instabilities, quasilinear diffusion, and collisionless damping with ultra-high intensity laser waves

    International Nuclear Information System (INIS)

    Rax, J.M.

    1992-04-01

    The dynamics of electrons in two-dimensional, linearly or circularly polarized, ultra-high intensity (above 10 18 W/cm 2 ) laser waves, is investigated. The Compton harmonic resonances are identified as the source of various stochastic instabilities. Both Arnold diffusion and resonance overlap are considered. The quasilinear kinetic equation, describing the evolution of the electron distribution function, is derived, and the associated collisionless damping coefficient is calculated. The implications of these new processes are considered and discussed

  12. On the electron-ion temperature ratio established by collisionless shocks

    Science.gov (United States)

    Vink, Jacco; Broersen, Sjors; Bykov, Andrei; Gabici, Stefano

    2015-07-01

    Astrophysical shocks are often collisionless shocks, in which the changes in plasma flow and temperatures across the shock are established not through Coulomb interactions, but through electric and magnetic fields. An open question about collisionless shocks is whether electrons and ions each establish their own post-shock temperature (non-equilibration of temperatures), or whether they quickly equilibrate in the shock region. Here we provide a simple, thermodynamic, relation for the minimum electron-ion temperature ratios that should be expected as a function of Mach number. The basic assumption is that the enthalpy-flux of the electrons is conserved separately, but that all particle species should undergo the same density jump across the shock, in order for the plasma to remain charge neutral. The only form of additional electron heating that we allow for is adiabatic heating, caused by the compression of the electron gas. These assumptions result in an analytic treatment of expected electron-ion temperature ratio that agrees with observations of collisionless shocks: at low sonic Mach numbers, Ms ≲ 2, the electron-ion temperature ratio is close to unity, whereas for Mach numbers above Ms ≈ 60 the electron-ion temperature ratio asymptotically approaches a temperature ratio of Te/Ti = me/ ⟨ mi ⟩. In the intermediate Mach number range the electron-ion temperature ratio scales as Te/Ti ∝ Ms-2. In addition, we calculate the electron-ion temperature ratios under the assumption of adiabatic heating of the electrons only, which results in a higher electron-ion temperature ratio, but preserves the Te/Ti ∝ Ms-2 scaling. We also show that for magnetised shocks the electron-ion temperature ratio approaches the asymptotic value Te/Ti = me/ ⟨ mi ⟩ for lower magnetosonic Mach numbers (Mms), mainly because for a strongly magnetised shock the sonic Mach number is larger than the magnetosonic Mach number (Mms ≤ Ms). The predicted scaling of the electron

  13. Shock formation and structure in magnetic reconnection with a streaming flow.

    Science.gov (United States)

    Wu, Liangneng; Ma, Zhiwei; Zhang, Haowei

    2017-08-18

    The features of magnetic reconnection with a streaming flow have been investigated on the basis of compressible resistive magnetohydrodynamic (MHD) model. The super-Alfvenic streaming flow largely enhances magnetic reconnection. The maximum reconnection rate is almost four times larger with super-Alfvenic streaming flow than sub-Alfvénic streaming flow. In the nonlinear stage, it is found that there is a pair of shocks observed in the inflow region, which are manifested to be slow shocks for sub-Alfvénic streaming flow, and fast shocks for super-Alfvénic streaming flow. The quasi-period oscillation of reconnection rates in the decaying phase for super-Alfvénic streaming flow is resulted from the different drifting velocities of the shock and the X point.

  14. A Model of Solar Flares Based on Arcade Field Reconnection and Merging of Magnetic Islands

    International Nuclear Information System (INIS)

    Choe, G.S.; Cheng, C.Z.

    2001-01-01

    Solar flares are intense, abrupt releases of energy in the solar corona. In the impulsive phase of a flare, the intensity of hard X-ray emission reaches a sharp peak indicating the highest reconnection rate. It is often observed that an X-ray emitting plasma ejecta (plasmoid) is launched before the impulsive phase and accelerated throughout the phase. Thus, the plasmoid ejection may not be an effect of fast magnetic reconnection as conventionally assumed, but a cause of fast reconnection. Based on resistive magnetohydrodynamic simulations, a solar flare model is presented, which can explain these observational characteristics of flares. In the model, merging of a newly generated magnetic island and a pre-existing island results in stretching and thinning of a current sheet, in which fast magnetic reconnection is induced. Recurrence of homologous flares naturally arises in this model. Mechanisms of magnetic island formation are also discussed

  15. Vortex Reconnections and Rebounds in Trapped Atomic Bose-Einstein Condensates

    Science.gov (United States)

    Serafini, Simone; Galantucci, Luca; Iseni, Elena; Bienaimé, Tom; Bisset, Russell N.; Barenghi, Carlo F.; Dalfovo, Franco; Lamporesi, Giacomo; Ferrari, Gabriele

    2017-04-01

    Reconnections and interactions of filamentary coherent structures play a fundamental role in the dynamics of fluids, redistributing energy and helicity among the length scales and inducing fine-scale turbulent mixing. Unlike ordinary fluids, where vorticity is a continuous field, in quantum fluids vorticity is concentrated into discrete (quantized) vortex lines turning vortex reconnections into isolated events, making it conceptually easier to study. Here, we report experimental and numerical observations of three-dimensional quantum vortex interactions in a cigar-shaped atomic Bose-Einstein condensate. In addition to standard reconnections, already numerically and experimentally observed in homogeneous systems away from boundaries, we show that double reconnections, rebounds, and ejections can also occur as a consequence of the nonhomogeneous, confined nature of the system.

  16. Vortex Reconnections and Rebounds in Trapped Atomic Bose-Einstein Condensates

    Directory of Open Access Journals (Sweden)

    Simone Serafini

    2017-05-01

    Full Text Available Reconnections and interactions of filamentary coherent structures play a fundamental role in the dynamics of fluids, redistributing energy and helicity among the length scales and inducing fine-scale turbulent mixing. Unlike ordinary fluids, where vorticity is a continuous field, in quantum fluids vorticity is concentrated into discrete (quantized vortex lines turning vortex reconnections into isolated events, making it conceptually easier to study. Here, we report experimental and numerical observations of three-dimensional quantum vortex interactions in a cigar-shaped atomic Bose-Einstein condensate. In addition to standard reconnections, already numerically and experimentally observed in homogeneous systems away from boundaries, we show that double reconnections, rebounds, and ejections can also occur as a consequence of the nonhomogeneous, confined nature of the system.

  17. Experimental verification of the role of electron pressure in fast magnetic reconnection with a guide field

    International Nuclear Information System (INIS)

    Fox, W.; Sciortino, F.; Stechow, A. von; Jara-Almonte, J.

    2017-01-01

    We report detailed laboratory observations of the structure of a reconnection current sheet in a two-fluid plasma regime with a guide magnetic field. We observe and quantitatively analyze the quadrupolar electron pressure variation in the ion-diffusion region, as originally predicted by extended magnetohydrodynamics simulations. The projection of the electron pressure gradient parallel to the magnetic field contributes significantly to balancing the parallel electric field, and the resulting cross-field electron jets in the reconnection layer are diamagnetic in origin. Furthermore, these results demonstrate how parallel and perpendicular force balance are coupled in guide field reconnection and confirm basic theoretical models of the importance of electron pressure gradients for obtaining fast magnetic reconnection.

  18. Multi-scale observations of magnetic reconnection: Cluster and MMS measurements of the reconnecting magnetopause at the subsolar region and dusk sector

    Science.gov (United States)

    Toledo Redondo, S.; Escoubet, C. P.; Lavraud, B.; Andre, M.; Coxon, J.; Fear, R. C.; Aunai, N.; Hwang, K. J.; Li, W.; Fuselier, S. A.; Giles, B. L.; Russell, C. T.; Burch, J. L.

    2017-12-01

    Magnetic reconnection is a fundamental plasma process that couples the shocked solar wind to the Earth's magnetosphere, allowing the interchange of energy and mass. The X line of magnetic reconnection lies along the magnetopause but its extent and orientation are only partially understood, despite its importance for understanding global solar wind - magnetosphere coupling. We have identified a series of conjunctions between the MMS and Cluster missions where they crossed simultaneously the magnetopause at locations separated by several Earth radii: MMS spacecraft were in the subsolar region while Cluster were in the dusk flank. We identify signatures of reconnection at both spacecraft, allowing us to draw new conclusions about the extent, orientation and time variations of the X line along the magnetopause.

  19. Magnetic reconnection in the low solar chromosphere with a more realistic radiative cooling model

    Science.gov (United States)

    Ni, Lei; Lukin, Vyacheslav S.; Murphy, Nicholas A.; Lin, Jun

    2018-04-01

    Magnetic reconnection is the most likely mechanism responsible for the high temperature events that are observed in strongly magnetized locations around the temperature minimum in the low solar chromosphere. This work improves upon our previous work [Ni et al., Astrophys. J. 852, 95 (2018)] by using a more realistic radiative cooling model computed from the OPACITY project and the CHIANTI database. We find that the rate of ionization of the neutral component of the plasma is still faster than recombination within the current sheet region. For low β plasmas, the ionized and neutral fluid flows are well-coupled throughout the reconnection region resembling the single-fluid Sweet-Parker model dynamics. Decoupling of the ion and neutral inflows appears in the higher β case with β0=1.46 , which leads to a reconnection rate about three times faster than the rate predicted by the Sweet-Parker model. In all cases, the plasma temperature increases with time inside the current sheet, and the maximum value is above 2 ×104 K when the reconnection magnetic field strength is greater than 500 G. While the more realistic radiative cooling model does not result in qualitative changes of the characteristics of magnetic reconnection, it is necessary for studying the variations of the plasma temperature and ionization fraction inside current sheets in strongly magnetized regions of the low solar atmosphere. It is also important for studying energy conversion during the magnetic reconnection process when the hydrogen-dominated plasma approaches full ionization.

  20. Global reconnection topology as inferred from plasma observations inside Kelvin-Helmholtz vortices

    Directory of Open Access Journals (Sweden)

    M. B. Bavassano Cattaneo

    2010-04-01

    Full Text Available During a long lasting period of northward interplanetary magnetic field and high solar wind speed (above 700 km/s, the Cluster spacecraft go across a number of very large rolled-up Kelvin-Helmholtz (KH vortices at the dusk magnetopause, close to the terminator. The peculiarity of the present event is a particular sequence of ions and electrons distribution functions observed repeatedly inside each vortex. In particular, whenever Cluster crosses the current layer inside the vortices, multiple field-aligned ion populations appear, suggesting the occurrence of reconnection. In addition, the ion data display a clear velocity filter effect both at the leading and at the trailing edge of each vortex. This effect is not present in the simultaneous electron data. Unlike other KH studies reported in the literature in which reconnection occurs within the vortices, in the present event the observations are not compatible with local reconnection, but are accounted for by lobe reconnection occurring along an extended X-line at the terminator in the Southern Hemisphere. The reconnected field lines "sink" across the magnetopause and then convect tailward-duskward where they become embedded in the vortices. Another observational evidence is the detected presence of solar wind plasma on the magnetospheric side of the vortices, which confirms unambiguously the occurrence of mass transport across the magnetopause already reported in the literature. The proposed reconnection scenario accounts for all the observational aspects, regarding both the transport process and the kinetic signatures.

  1. The Roles of Fluid Compression and Shear in Electron Energization during Magnetic Reconnection

    Science.gov (United States)

    Li, Xiaocan; Guo, Fan; Li, Hui; Birn, Joachim

    2018-03-01

    Particle acceleration in space and astrophysical reconnection sites is an important unsolved problem in studies of magnetic reconnection. Earlier kinetic simulations have identified several acceleration mechanisms that are associated with particle drift motions. Here, we show that, for sufficiently large systems, the energization processes due to particle drift motions can be described as fluid compression and shear, and that the shear energization is proportional to the pressure anisotropy of energetic particles. By analyzing results from fully kinetic simulations, we show that the compression energization dominates the acceleration of high-energy particles in reconnection with a weak guide field, and the compression and shear effects are comparable when the guide field is 50% of the reconnecting component. Spatial distributions of those energization effects reveal that reconnection exhausts, contracting islands, and island-merging regions are the three most important regions for compression and shear acceleration. This study connects particle energization by particle guiding-center drift motions with that due to background fluid motions, as in the energetic particle transport theory. It provides foundations for building particle transport models for large-scale reconnection acceleration such as those in solar flares.

  2. Physics of the saturation of particle acceleration in relativistic magnetic reconnection

    Science.gov (United States)

    Kagan, Daniel; Nakar, Ehud; Piran, Tsvi

    2018-05-01

    We investigate the saturation of particle acceleration in relativistic reconnection using two-dimensional particle-in-cell simulations at various magnetizations σ. We find that the particle energy spectrum produced in reconnection quickly saturates as a hard power law that cuts off at γ ≈ 4σ, confirming previous work. Using particle tracing, we find that particle acceleration by the reconnection electric field in X-points determines the shape of the particle energy spectrum. By analysing the current sheet structure, we show that physical cause of saturation is the spontaneous formation of secondary magnetic islands that can disrupt particle acceleration. By comparing the size of acceleration regions to the typical distance between disruptive islands, we show that the maximum Lorentz factor produced in reconnection is γ ≈ 5σ, which is very close to what we find in our particle energy spectra. We also show that the dynamic range in Lorentz factor of the power-law spectrum in reconnection is ≤40. The hardness of the power law combined with its narrow dynamic range implies that relativistic reconnection is capable of producing the hard narrow-band flares observed in the Crab nebula but has difficulty producing the softer broad-band prompt gamma-ray burst emission.

  3. Kinetic simulations of magnetic reconnection in presence of a background O+ population

    Science.gov (United States)

    Markidis, S.; Lapenta, G.; Bettarini, L.; Goldman, M.; Newman, D.; Andersson, L.

    2011-09-01

    Particle-in-Cell simulations of magnetic reconnection with an H+ current sheet and a mixed background plasma of H+ and O+ ions are completed using physical mass ratios. Four main results are shown. First, the O+ presence slightly decreases the reconnection rate and the magnetic reconnection evolution depends mainly on the lighter H+ ion species in the presented simulations. Second, the Hall magnetic field is characterized by a two-scale structure in presence of O+ ions: it reaches sharp peak values in a small area in proximity of the neutral line, and then decreases slowly over a large region. Third, the two background species initially separate in the outflow region because H+ and O+ ions are accelerated by different mechanisms occurring on different timescales and with different strengths. Fourth, the effect of a guide field on the O+ dynamics is studied: the O+ presence does not change the reconnected flux and all the characteristic features of guide field magnetic reconnection are still present. Moreover, the guide field introduces an O+ circulation pattern between separatrices that enhances high O+ density areas and depletes low O+ density regions in proximity of the reconnection fronts. The importance and the validity of these results are finally discussed.

  4. Physics of the saturation of particle acceleration in relativistic magnetic reconnection

    Science.gov (United States)

    Kagan, Daniel; Nakar, Ehud; Piran, Tsvi

    2018-02-01

    We investigate the saturation of particle acceleration in relativistic reconnection using two-dimensional particle-in-cell simulations at various magnetizations σ. We find that the particle energy spectrum produced in reconnection quickly saturates as a hard power law that cuts off at γ ≈ 4σ, confirming previous work. Using particle tracing, we find that particle acceleration by the reconnection electric field in X-points determines the shape of the particle energy spectrum. By analyzing the current sheet structure, we show that physical cause of saturation is the spontaneous formation of secondary magnetic islands that can disrupt particle acceleration. By comparing the size of acceleration regions to the typical distance between disruptive islands, we show that the maximum Lorentz factor produced in reconnection is γ ≈ 5σ, which is very close to what we find in our particle energy spectra. We also show that the dynamic range in Lorentz factor of the power law spectrum in reconnection is ≤40. The hardness of the power law combined with its narrow dynamic range implies that relativistic reconnection is capable of producing the hard narrowband flares observed in the Crab Nebula but has difficulty producing the softer broadband prompt GRB emission.

  5. Strong ion accelerating by collisionless magnetosonic shock wave propagating perpendicular to a magnetic field

    International Nuclear Information System (INIS)

    Ohsawa, Yukiharu.

    1984-12-01

    A 2-1/2 dimensional fully relativistic, fully electromagnetic particle code is used to study a time evolution of nonlinear magnetosonic pulse propagating in the direction perpendicular to a magnetic field. The pulse is excited by an instantaneous piston acceleration, and evolves totally self-consistently. Large amplitude pulse traps some ions and accelerates them parallel to the wave front. They are detrapped when their velocities become of the order of the sum of the ExB drift velocity and the wave phase velocity, where E is the electric field in the direction of wave propagation. The pulse develops into a quasi-shock wave in a collisionless plasma by a dissipation due to the resonant ion acceleration. Simple nonlinear wave theory for a cold plasma well describes the shock properties observed in the simulation except for the effects of resonant ions. In particular, magnitude of an electric potential across the shock region is derived analytically and is found to be in good agreement with our simulations. The potential jump is proportional to B 2 , and hence the ExB drift velocity of the trapped ions is proportional to B. (author)

  6. Mechanism of collisionless sound damping in dilute Bose gas with condensate

    Directory of Open Access Journals (Sweden)

    Yu. Slyusarenko

    2013-06-01

    Full Text Available We develop a microscopic theory of sound damping due to Landau mechanism in dilute gas with Bose condensate. It is based on the coupled evolution equations of the parameters describing the system. These equations have been derived in earlier works within a microscopic approach which employs the Peletminskii-Yatsenko reduced description method for quantum many-particle systems and Bogoliubov model for a weakly nonideal Bose gas with a separated condensate. The dispersion equations for sound oscillations were obtained by linearization of the mentioned evolution equations in the collisionless approximation. They were analyzed both analytically and numerically. The expressions for sound speed and decrement rate were obtained in high and low temperature limiting cases. We have shown that at low temperature the dependence of obtained quantities on temperature varies significantly from those one obtained by other authors in the semi-phenomenological approaches. Possible effects connected with non-analytic temperature dependence of dispersion characteristics of the system were also indicated.

  7. ENTROPY PRODUCTION IN COLLISIONLESS SYSTEMS. II. ARBITRARY PHASE-SPACE OCCUPATION NUMBERS

    International Nuclear Information System (INIS)

    Barnes, Eric I.; Williams, Liliya L. R.

    2012-01-01

    We present an analysis of two thermodynamic techniques for determining equilibria of self-gravitating systems. One is the Lynden-Bell (LB) entropy maximization analysis that introduced violent relaxation. Since we do not use the Stirling approximation, which is invalid at small occupation numbers, our systems have finite mass, unlike LB's isothermal spheres. (Instead of Stirling, we utilize a very accurate smooth approximation for ln x!.) The second analysis extends entropy production extremization to self-gravitating systems, also without the use of the Stirling approximation. In addition to the LB statistical family characterized by the exclusion principle in phase space, and designed to treat collisionless systems, we also apply the two approaches to the Maxwell-Boltzmann (MB) families, which have no exclusion principle and hence represent collisional systems. We implicitly assume that all of the phase space is equally accessible. We derive entropy production expressions for both families and give the extremum conditions for entropy production. Surprisingly, our analysis indicates that extremizing entropy production rate results in systems that have maximum entropy, in both LB and MB statistics. In other words, both thermodynamic approaches lead to the same equilibrium structures.

  8. A fully kinetic, self-consistent particle simulation model of the collisionless plasma--sheath region

    International Nuclear Information System (INIS)

    Procassini, R.J.; Birdsall, C.K.; Morse, E.C.

    1990-01-01

    A fully kinetic particle-in-cell (PIC) model is used to self-consistently determine the steady-state potential profile in a collisionless plasma that contacts a floating, absorbing boundary. To balance the flow of particles to the wall, a distributed source region is used to inject particles into the one-dimensional system. The effect of the particle source distribution function on the source region and collector sheath potential drops, and particle velocity distributions is investigated. The ion source functions proposed by Emmert et al. [Phys. Fluids 23, 803 (1980)] and Bissell and Johnson [Phys. Fluids 30, 779 (1987)] (and various combinations of these) are used for the injection of both ions and electrons. The values of the potential drops obtained from the PIC simulations are compared to those from the theories of Emmert et al., Bissell and Johnson, and Scheuer and Emmert [Phys. Fluids 31, 3645 (1988)], all of which assume that the electron density is related to the plasma potential via the Boltzmann relation. The values of the source region and total potential drop are found to depend on the choice of the electron source function, as well as the ion source function. The question of an infinite electric field at the plasma--sheath interface, which arises in the analyses of Bissell and Johnson and Scheuer and Emmert, is also addressed

  9. Nonstationarity of a two-dimensional quasiperpendicular supercritical collisionless shock by self-reformation

    International Nuclear Information System (INIS)

    Lembege, B.; Savoini, P.

    1992-01-01

    Two-dimensional electromagnetic particle simulations evidence a self-reformation of the shock front for a collisionless supercritical magnetosonic shock propagating at angle θ 0 around 90 degree, where θ 0 is the angle between the normal to the shock front and the upstream magnetostatic field. This self-reformation is due to reflected ions which accumulate in front of the shock and is observed (i) in both electric and magnetic components, (ii) for both resistive and nonresistive two-dimensional shocks, and (iii) over a cyclic time period equal to the mean ion gyroperiod measured downstream in the overshoot; resistive effects may be self-consistently included or excluded for θ 0 congruent 90 degree according to a judicious choice of the upstream magnetostatic field orientation. The self-reformation leads to a nonstationary behavior of the shock; however, present results show evidence that the shock becomes stationary for θ less than a critical value θ r , below which the self-reformation disappears. Present results are compared to previous works where one/two-dimensional hybrid and particle codes have been used, and to experimental measurements

  10. Carter constant induced mechanism for generation of anisotropic kinetic equilibria in collisionless N-body systems

    Science.gov (United States)

    Cremaschini, Claudio; Stuchlík, Zdeněk

    A new intrinsically-relativistic kinetic mechanism for generation of nonisotropic relativistic kinetic equilibria in collisionless N-body systems is pointed out. The theory is developed in the framework of the covariant Vlasov statistical description. The new effect is based on the constraints placed by the conservation laws of neutral single-particle dynamics in prescribed background curved-spacetimes demonstrating existence of Killing tensors. As an illustration, the particular case of the Kerr spacetime admitting the so-called Carter constant for the particle geodesic motion is considered. The general functional form of the equilibrium kinetic distribution function (KDF) is determined and an explicit realization in terms of Gaussian-like distributions is provided. It is shown that, due to the Carter constant, these equilibrium KDFs exhibit an anisotropic phase-space functional dependence in terms of the single-particle 4-velocity components, giving rise to corresponding nonisotropic continuum fluid fields. The qualitative properties of the equilibrium stress-energy tensor associated with these systems are discussed, with a particular emphasis on the related occurrence of temperature anisotropy effects. The theory is susceptible of astrophysical applications, including in particular the statistical properties of dark matter (DM) halos around stellar-mass or galactic-center black holes.

  11. Electrostatic and magnetic instabilities in the transition layer of a collisionless weakly relativistic pair shock

    Science.gov (United States)

    Dieckmann, M. E.; Bret, A.

    2018-01-01

    Energetic electromagnetic emissions by astrophysical jets like those that are launched during the collapse of a massive star and trigger gamma-ray bursts are partially attributed to relativistic internal shocks. The shocks are mediated in the collisionless plasma of such jets by the filamentation instability of counterstreaming particle beams. The filamentation instability grows fastest only if the beams move at a relativistic relative speed. We model here with a particle-in-cell simulation, the collision of two cold pair clouds at the speed c/2 (c: speed of light). We demonstrate that the two-stream instability outgrows the filamentation instability for this speed and is thus responsible for the shock formation. The incomplete thermalization of the upstream plasma by its quasi-electrostatic waves allows other instabilities to grow. A shock transition layer forms, in which a filamentation instability modulates the plasma far upstream of the shock. The inflowing upstream plasma is progressively heated by a two-stream instability closer to the shock and compressed to the expected downstream density by the Weibel instability. The strong magnetic field due to the latter is confined to a layer 10 electron skin depths wide.

  12. Magnetic reconnection in numerical simulations of the Bastille day flare

    Science.gov (United States)

    Vincent, A. P.; Charbonneau, P.

    2011-12-01

    If neither waves nor adiabatic heating due to compression are taken into account, coronal heating may be obtained in numerical simulations from current dissipation inside solar flares. To increase Joule heating locally we used a model for hyper resistivity (Klimas et al., 2004: Journal of Geophysical Research, 109, 2218-2231). Here the change in resistivity is due to small scale (less than 1Mm in our simulations) current density fluctuations. Whenever the current exceeds a cut-off value, magnetic resistivity jumps sharply to reach a maximum locally thus increasing magnetic gradients at the border of the flare. In this way, not only the current increases but also the maximum is slowly displaced and simulations of the full set of 3-D MHD equations show a progression westward as can be seen in SOHO-EIT images of the ''slinky''. In our simulations of the Bastille day flare, most of the reconnection events take place just above the transition and mostly follow the neutral line but it is Spitzer thermal diffusivity together with radiative cooling that illuminates magnetic arcades in a way similar to what can be seen in extreme ultra-violet animations of the slinky.

  13. Particle Acceleration and Fractional Transport in Turbulent Reconnection

    Science.gov (United States)

    Isliker, Heinz; Pisokas, Theophilos; Vlahos, Loukas; Anastasiadis, Anastasios

    2017-11-01

    We consider a large-scale environment of turbulent reconnection that is fragmented into a number of randomly distributed unstable current sheets (UCSs), and we statistically analyze the acceleration of particles within this environment. We address two important cases of acceleration mechanisms when particles interact with the UCS: (a) electric field acceleration and (b) acceleration by reflection at contracting islands. Electrons and ions are accelerated very efficiently, attaining an energy distribution of power-law shape with an index 1-2, depending on the acceleration mechanism. The transport coefficients in energy space are estimated from test-particle simulation data, and we show that the classical Fokker-Planck (FP) equation fails to reproduce the simulation results when the transport coefficients are inserted into it and it is solved numerically. The cause for this failure is that the particles perform Levy flights in energy space, while the distributions of the energy increments exhibit power-law tails. We then use the fractional transport equation (FTE) derived by Isliker et al., whose parameters and the order of the fractional derivatives are inferred from the simulation data, and solving the FTE numerically, we show that the FTE successfully reproduces the kinetic energy distribution of the test particles. We discuss in detail the analysis of the simulation data and the criteria that allow one to judge the appropriateness of either an FTE or a classical FP equation as a transport model.

  14. MMS Observations of Vorticity Near Sites of Magnetic Reconnection

    Science.gov (United States)

    Paterson, W. R.; Giles, B. L.; Avanov, L. A.; Boardsen, S. A.; Dorelli, J.; Gershman, D. J.; Mackler, D. A.; Moore, T. E.; Pollock, C. J.; Schiff, C.; Shuster, J. R.; Viñas, A. F.; Russell, C. T.; Strangeway, R. J.; Burch, J. L.; Torbert, R. B.

    2017-12-01

    With highly capable plasma instruments on four spacecraft flown in tetrahedral formation, it is possible for MMS investigators to approximate spatial derivatives of the plasma parameters observed. Here, we examine vorticity of the electron and ion components of the plasma computed from the curl of velocity as measured by the Fast Plasma Investigation (FPI). Vorticity of magnetospheric plasma has not previously been studied on scales of tens-of-km to less than 10 km, which are the typical inter-spacecraft separations for MMS. Nor has it been explored on time scales of 30 ms for electrons and 150 ms for ions, which are the burst data rates for the FPI spectrometers. Review of observations from the magnetopause and magnetotail phases of the mission finds increases in vorticity associated with near encounters with the electron diffusion region, with nearby regions of measurable current, and with elevated electron and ion temperatures. These are suggestive of a possible role for turbulence in magnetic reconnection. In this presentation we provide an assessment of the quality of these measurements and discuss their potential significance.

  15. Nonlinear Modeling of Forced Magnetic Reconnection with Transient Perturbations

    Science.gov (United States)

    Beidler, Matthew T.; Callen, James D.; Hegna, Chris C.; Sovinec, Carl R.

    2017-10-01

    Externally applied 3D magnetic fields in tokamaks can penetrate into the plasma and lead to forced magnetic reconnection, and hence magnetic islands, on resonant surfaces. Analytic theory has been reasonably successful in describing many aspects of this paradigm with regard to describing the time asymptotic-steady state. However, understanding the nonlinear evolution into a low-slip, field-penetrated state, especially how MHD events such as sawteeth and ELMs precipitate this transition, is in its early development. We present nonlinear computations employing the extended-MHD code NIMROD, building on previous work by incorporating a temporally varying external perturbation as a simple model for an MHD event that produces resonant magnetic signals. A parametric series of proof-of-principle computations and accompanying analytical theory characterize the transition into a mode-locked state with an emphasis on detailing the temporal evolution properties. Supported by DOE OFES Grants DE-FG02-92ER54139, DE-FG02-86ER53218, and the U.S. DOE FES Postdoctoral Research program administered by ORISE and managed by ORAU under DOE contract DE-SC0014664.

  16. Energetic Particles of keV–MeV Energies Observed near Reconnecting Current Sheets at 1 au

    Energy Technology Data Exchange (ETDEWEB)

    Khabarova, Olga V. [Heliophysical Laboratory, Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN), Moscow (Russian Federation); Zank, Gary P. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35805 (United States)

    2017-07-01

    We provide evidence for particle acceleration up to ∼5 MeV at reconnecting current sheets in the solar wind based on both case studies and a statistical analysis of the energetic ion and electron flux data from the five Advanced Composition Explorer Electron, Proton, and Alpha Monitor (EPAM) detectors. The case study of a typical reconnection exhaust event reveals (i) a small-scale peak of the energetic ion flux observed in the vicinity of the reconnection exhaust and (ii) a long-timescale atypical energetic particle event (AEPE) encompassing the reconnection exhaust. AEPEs associated with reconnecting strong current sheets last for many hours, even days, as confirmed by statistical studies. The case study shows that time-intensity profiles of the ion flux may vary significantly from one EPAM detector to another partially because of the local topology of magnetic fields, but mainly because of the impact of upstream magnetospheric events; therefore, the occurrence of particle acceleration can be hidden. The finding of significant particle energization within a time interval of ±30 hr around reconnection exhausts is supported by a superposed epoch analysis of 126 reconnection exhaust events. We suggest that energetic particles initially accelerated via prolonged magnetic reconnection are trapped and reaccelerated in small- or medium-scale magnetic islands surrounding the reconnecting current sheet, as predicted by the transport theory of Zank et al. Other mechanisms of initial particle acceleration can contribute also.

  17. In Situ Observations of a Magnetosheath High-Speed Jet Triggering Magnetopause Reconnection

    Science.gov (United States)

    Hietala, H.; Phan, T.; Angelopoulos, V.; Oieroset, M.; Archer, M. O.; Karlsson, T.; Plaschke, F.

    2017-12-01

    The dayside solar wind-magnetosphere interaction is mediated by the magnetosheath. Magnetosheath high-speed jets (HSJs) - dynamic pressure enhancements typically of 1 Earth radius (RE) in size - impact the magnetopause several times per hour, i.e., much more frequently than any other known dayside transient. When HSJs hit the magnetopause, they may cause large amplitude yet localized boundary indentations, inciting magnetospheric waves. Possible consequences of these impacts include dropouts and other variations in radiation belt electron populations, and diffuse `throat' aurora. There have also been various indirect observations suggesting that magnetopause reconnection may occur in association with HSJ impacts. Here we present the first in situ evidence suggesting that a magnetosheath high-speed jet triggered magnetopause reconnection. We consider a HSJ impact that was part of a series of jets observed by THEMIS in the string-of-pearls configuration on August 7, 2007. The inter-probe separations ranged from 2RE to 0.07RE, allowing us to investigate this multi-scale process. According to OMNI data, the IMF was northward during this impact, i.e., unfavorable for low latitude magnetopause reconnection. First the magnetopause moved inwards past THB (the outermost probe) to a location between THE and THA (the innermost probe). In the magnetosheath THB observed a HSJ with a large velocity directed towards the magnetopause (VN 300km/s). After the HSJ the magnetopause moved back out. Before the HSJ (outbound crossing), there is no evidence for reconnection at the four probes. After the HSJ (inbound crossing), there were clear reconnection outflows (VL -250km/s), implying that reconnection was triggered by the HSJ impact. We infer that this was likely due to the HSJ's high dynamic pressure ( 4 nPa, 8 times the ambient magnetosheath dynamic pressure) compressing the thick (60-70 di), high shear (140-160°) magnetopause until it was thin enough to reconnect.

  18. Formation of a transient front structure near reconnection point in 3-D PIC simulations

    Science.gov (United States)

    Vapirev, A. E.; Lapenta, G.; Divin, A.; Markidis, S.; Henri, P.; Goldman, M.; Newman, D.

    2013-04-01

    Massively parallel numerical simulations of magnetic reconnection are presented in this study. Electromagnetic full-particle implicit code iPIC3D is used to study the dynamics and 3-D evolution of reconnection outflows. Such features as Hall magnetic field, inflow and outflow, and diffusion region formation are very similar to 2-D particle-in-cell (PIC) simulations. In addition, it is well known that instabilities develop in the current flow direction or oblique directions. These modes could provide for anomalous resistivity and diffusive drag and can serve as additional proxies for magnetic reconnection. In our work, the unstable evolution of reconnection transient front structures is studied. Reconnection configuration in the absence of guide field is considered, and it is initialized with a localized perturbation aligned in the cross-tail direction. Our study suggests that the instabilities lead to the development of finger-like density structures on ion-electron hybrid scales. These structures are characterized by a rapid increase of the magnetic field, normal to the current sheet (Bz). A small decrease in the magnetic field component parallel to the reconnection X line and the component perpendicular to the current sheet is observed in the region ahead of the front. The instabilities form due to fact that the density gradient inside the front region is opposite to the direction of the acceleration Lorentz force. Such density structures may possibly further develop into larger-scale earthward flux transfer events during magnetotail reconnection. In addition, oscillations mainly in the magnetic and electric fields and the electron density are observed shortly before the arrival of the main front structure which is consistent with recent THEMIS observations.

  19. X-RAY EMISSION FROM SUPERNOVAE IN DENSE CIRCUMSTELLAR MATTER ENVIRONMENTS: A SEARCH FOR COLLISIONLESS SHOCKS

    International Nuclear Information System (INIS)

    Ofek, E. O.; Gal-Yam, A.; Yaron, O.; Arcavi, I.; Fox, D.; Cenko, S. B.; Filippenko, A. V.; Bloom, J. S.; Sullivan, M.; Gnat, O.; Frail, D. A.; Horesh, A.; Kulkarni, S. R.; Corsi, A.; Quimby, R. M.; Gehrels, N.; Nugent, P. E.; Kasliwal, M. M.; Bildsten, L.; Poznanski, D.

    2013-01-01

    The optical light curve of some supernovae (SNe) may be powered by the outward diffusion of the energy deposited by the explosion shock (the so-called shock breakout) in optically thick (τ ∼> 30) circumstellar matter (CSM). Recently, it was shown that the radiation-mediated and radiation-dominated shock in an optically thick wind must transform into a collisionless shock and can produce hard X-rays. The X-rays are expected to peak at late times, relative to maximum visible light. Here we report on a search, using Swift/XRT and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense CSM. Our sample includes 19 Type IIn SNe, one Type Ibn SN, and eight hydrogen-poor superluminous SNe (SLSN-I such as SN 2005ap). Two SNe (SN 2006jc and SN 2010jl) have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSM. However, the X-ray emission from SN 2006jc can also be explained as originating in an optically thin region. Thus, we propose that the optical light curve of SN 2010jl is powered by shock breakout in CSM. We suggest that two other events (SN 2010al and SN 2011ht) were too X-ray bright during the SN maximum optical light to be explained by the shock-breakout model. We conclude that the light curves of some, but not all, SNe IIn/Ibn are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all of the SLSN-I events, our X-ray limits are not deep enough and were typically obtained too early (i.e., near the SN maximum light) for definitive conclusions about their nature. Late-time X-ray observations are required in order to further test whether these SNe are indeed embedded in dense CSM. We review the conditions required for a shock breakout in a wind profile. We argue that the timescale, relative to maximum light, for the SN to peak in X-rays is a probe of the column density and the density profile above the

  20. Whistler waves, core ion heating, and nonstationarity in oblique collisionless shocks

    International Nuclear Information System (INIS)

    Scholer, Manfred; Burgess, David

    2007-01-01

    One-dimensional full particle simulations of supercritical collisionless shocks with an ion and electron beta of 0.1 (particle to magnetic field pressure) over a wide Alfven Mach number range and range of shock normal-magnetic field angles between Θ Bn =60 deg. and Θ Bn =80 deg. are presented. The whistler critical Mach number M w , below which a linear phase-standing whistler can exist, is proportional to the square root of the ion-to-electron mass ratio and to cos Θ Bn . In small mass ratio simulations of oblique shocks, M w can be artificially small and close to the first critical Mach number M c , above which the process of ion reflection is needed in order to achieve shock dissipation. We use in the simulations the physical ion-to-electron mass ratio so that M c and M w are well separated. This also allows excitation of the modified two-stream instability (MTSI) between incoming ions and electrons. We find that in oblique but close to perpendicular (Θ Bn ≥80 deg.) shocks, upstream whistler waves do occur, but reformation is due to accumulation of reflected-gyrating ions at the upstream edge of the foot. In less oblique shocks above the whistler critical Mach number, the whistler amplitude in the foot upstream of the ramp grows, leading to vortices of the incoming ions and the reflected ions in velocity phase space, and eventually to phase mixing. The shock re-forms at the upstream edge of the whistler wave train, which is particularly evident in very high Mach number shocks where the scale of the foot is large compared with the whistler wave train. After reformation, the region with phase-mixed incoming and reflected ions constitutes a hot core downstream of the shock ramp. In this whistler induced reformation process, the MTSI results mainly in heating of the incoming ions in the foot

  1. More than six hundred new families of Newtonian periodic planar collisionless three-body orbits

    Science.gov (United States)

    Li, XiaoMing; Liao, ShiJun

    2017-12-01

    The famous three-body problem can be traced back to Isaac Newton in the 1680s. In the 300 years since this "three-body problem" was first recognized, only three families of periodic solutions had been found, until 2013 when Šuvakov and Dmitrašinović [Phys. Rev. Lett. 110, 114301 (2013)] made a breakthrough to numerically find 13 new distinct periodic orbits, which belong to 11 new families of Newtonian planar three-body problem with equal mass and zero angular momentum. In this paper, we numerically obtain 695 families of Newtonian periodic planar collisionless orbits of three-body system with equal mass and zero angular momentum in case of initial conditions with isosceles collinear configuration, including the well-known figure-eight family found by Moore in 1993, the 11 families found by Šuvakov and Dmitrašinović in 2013, and more than 600 new families that have never been reported, to the best of our knowledge. With the definition of the average period T = T/L f, where L f is the length of the so-called "free group element", these 695 families suggest that there should exist the quasi Kepler's third law T* ≈ 2:433 ± 0:075 for the considered case, where T ≈ = T | E|3/2 is the scale-invariant average period and E is its total kinetic and potential energy, respectively. The movies of these 695 periodic orbits in the real space and the corresponding close curves on the "shape sphere" can be found via the website: http://numericaltank.sjtu.edu.cn/three-body/three-body.htm.

  2. Nonstationarity of strong collisionless quasiperpendicular shocks: Theory and full particle numerical simulations

    International Nuclear Information System (INIS)

    Krasnoselskikh, V.V.; Lembege, B.; Savoini, P.; Lobzin, V.V.

    2002-01-01

    Whistler waves are an intrinsic feature of the oblique quasiperpendicular collisionless shock waves. For supercritical shock waves, the ramp region, where an abrupt increase of the magnetic field occurs, can be treated as a nonlinear whistler wave of large amplitude. In addition, oblique shock waves can possess a linear whistler precursor. There exist two critical Mach numbers related to the whistler components of the shock wave, the first is known as a whistler critical Mach number and the second can be referred to as a nonlinear whistler critical Mach number. When the whistler critical Much number is exceeded, a stationary linear wave train cannot stand ahead of the ramp. Above the nonlinear whistler critical Mach number, the stationary nonlinear wave train cannot exist anymore within the shock front. This happens when the nonlinear wave steepening cannot be balanced by the effects of the dispersion and dissipation. In this case nonlinear wave train becomes unstable with respect to overturning. In the present paper it is shown that the nonlinear whistler critical Mach number corresponds to the transition between stationary and nonstationary dynamical behavior of the shock wave. The results of the computer simulations making use of the 1D full particle electromagnetic code demonstrate that the transition to the nonstationarity of the shock front structure is always accompanied by the disappearance of the whistler wave train within the shock front. Using the two-fluid MHD equations, the structure of nonlinear whistler waves in plasmas with finite beta is investigated and the nonlinear whistler critical Mach number is determined. It is suggested a new more general proof of the criteria for small amplitude linear precursor or wake wave trains to exist

  3. Noncoplanar magnetic fields at collisionless shocks: A test of a new approach

    International Nuclear Information System (INIS)

    Gosling, J.T.; Winske, D.; Thomsen, M.F.

    1988-01-01

    Within the foot and ramp of a fast mode collisionless shock the magnetic field rotates out of the plane of coplanarity defined by the upstream magnetic field and the shock normal. As previously noted (Goodrich and Scudder, 1984), the sense of this rotation is such as to reduce the cross-shock potential drop when measured in the deHoffman-Teller frame relative to that measured in the normal incidence frame. From a consideration of the requirement that there be zero current in the coplanarity plane downstream of the shock, Jones and Ellison (1987) have argued that the field rotation and potential drop difference are a consequence of unequal ion and electron masses, and have derived an expression for the spatial integral of the noncoplanar field component in terms of the electron current within the shock layer. Moreover, by assuming that the ion current within the shock layer is negligible compared to the electron current, they derive equations which predict the magnitude of both the field rotation and the potential drop difference in terms of upstream quantities and the field jump at the shock. We have tested their equations with ISEE 1 and 2 plasma and field measurements at the Earth's bow shock and by means of numerical simulations. We find substantial support for their suggestion that the field rotation and thus also the frame dependence of the potential drop are fundamentally a consequence of unequal ion and electron masses. Further, for subcritical shocks (low Mach number) one can neglect the ion current to predict both the sign and the magnitude of the field rotation and potential drop difference. However, at supercritical shocks (high Mach numbers) the ion current associated with reflected, gyrating ions cannot be neglected, and the final equations of Jones and Ellison seriously underestimate the magnitude of the field rotation and the potential drop difference at these shocks

  4. An in situ Comparison of Electron Acceleration at Collisionless Shocks under Differing Upstream Magnetic Field Orientations

    International Nuclear Information System (INIS)

    Masters, A.; Dougherty, M. K.; Sulaiman, A. H.; Stawarz, Ł.; Reville, B.; Sergis, N.; Fujimoto, M.; Burgess, D.; Coates, A. J.

    2017-01-01

    A leading explanation for the origin of Galactic cosmic rays is acceleration at high-Mach number shock waves in the collisionless plasma surrounding young supernova remnants. Evidence for this is provided by multi-wavelength non-thermal emission thought to be associated with ultrarelativistic electrons at these shocks. However, the dependence of the electron acceleration process on the orientation of the upstream magnetic field with respect to the local normal to the shock front (quasi-parallel/quasi-perpendicular) is debated. Cassini spacecraft observations at Saturn’s bow shock have revealed examples of electron acceleration under quasi-perpendicular conditions, and the first in situ evidence of electron acceleration at a quasi-parallel shock. Here we use Cassini data to make the first comparison between energy spectra of locally accelerated electrons under these differing upstream magnetic field regimes. We present data taken during a quasi-perpendicular shock crossing on 2008 March 8 and during a quasi-parallel shock crossing on 2007 February 3, highlighting that both were associated with electron acceleration to at least MeV energies. The magnetic signature of the quasi-perpendicular crossing has a relatively sharp upstream–downstream transition, and energetic electrons were detected close to the transition and immediately downstream. The magnetic transition at the quasi-parallel crossing is less clear, energetic electrons were encountered upstream and downstream, and the electron energy spectrum is harder above ∼100 keV. We discuss whether the acceleration is consistent with diffusive shock acceleration theory in each case, and suggest that the quasi-parallel spectral break is due to an energy-dependent interaction between the electrons and short, large-amplitude magnetic structures.

  5. Time-dependence in relativistic collisionless shocks: theory of the variable

    Energy Technology Data Exchange (ETDEWEB)

    Spitkovsky, A

    2004-02-05

    We describe results from time-dependent numerical modeling of the collisionless reverse shock terminating the pulsar wind in the Crab Nebula. We treat the upstream relativistic wind as composed of ions and electron-positron plasma embedded in a toroidal magnetic field, flowing radially outward from the pulsar in a sector around the rotational equator. The relativistic cyclotron instability of the ion gyrational orbit downstream of the leading shock in the electron-positron pairs launches outward propagating magnetosonic waves. Because of the fresh supply of ions crossing the shock, this time-dependent process achieves a limit-cycle, in which the waves are launched with periodicity on the order of the ion Larmor time. Compressions in the magnetic field and pair density associated with these waves, as well as their propagation speed, semi-quantitatively reproduce the behavior of the wisp and ring features described in recent observations obtained using the Hubble Space Telescope and the Chandra X-Ray Observatory. By selecting the parameters of the ion orbits to fit the spatial separation of the wisps, we predict the period of time variability of the wisps that is consistent with the data. When coupled with a mechanism for non-thermal acceleration of the pairs, the compressions in the magnetic field and plasma density associated with the optical wisp structure naturally account for the location of X-ray features in the Crab. We also discuss the origin of the high energy ions and their acceleration in the equatorial current sheet of the pulsar wind.

  6. An in situ Comparison of Electron Acceleration at Collisionless Shocks under Differing Upstream Magnetic Field Orientations

    Energy Technology Data Exchange (ETDEWEB)

    Masters, A.; Dougherty, M. K. [The Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2AZ (United Kingdom); Sulaiman, A. H. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Stawarz, Ł. [Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Krakow (Poland); Reville, B. [School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN (United Kingdom); Sergis, N. [Office of Space Research and Technology, Academy of Athens, Soranou Efesiou 4, 11527 Athens (Greece); Fujimoto, M. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Burgess, D. [School of Physics and Astronomy, Queen Mary University of London, London E1 4NS (United Kingdom); Coates, A. J., E-mail: a.masters@imperial.ac.uk [Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking RH5 6NT (United Kingdom)

    2017-07-10

    A leading explanation for the origin of Galactic cosmic rays is acceleration at high-Mach number shock waves in the collisionless plasma surrounding young supernova remnants. Evidence for this is provided by multi-wavelength non-thermal emission thought to be associated with ultrarelativistic electrons at these shocks. However, the dependence of the electron acceleration process on the orientation of the upstream magnetic field with respect to the local normal to the shock front (quasi-parallel/quasi-perpendicular) is debated. Cassini spacecraft observations at Saturn’s bow shock have revealed examples of electron acceleration under quasi-perpendicular conditions, and the first in situ evidence of electron acceleration at a quasi-parallel shock. Here we use Cassini data to make the first comparison between energy spectra of locally accelerated electrons under these differing upstream magnetic field regimes. We present data taken during a quasi-perpendicular shock crossing on 2008 March 8 and during a quasi-parallel shock crossing on 2007 February 3, highlighting that both were associated with electron acceleration to at least MeV energies. The magnetic signature of the quasi-perpendicular crossing has a relatively sharp upstream–downstream transition, and energetic electrons were detected close to the transition and immediately downstream. The magnetic transition at the quasi-parallel crossing is less clear, energetic electrons were encountered upstream and downstream, and the electron energy spectrum is harder above ∼100 keV. We discuss whether the acceleration is consistent with diffusive shock acceleration theory in each case, and suggest that the quasi-parallel spectral break is due to an energy-dependent interaction between the electrons and short, large-amplitude magnetic structures.

  7. New evidence for efficient collisionless heating of electrons at the reverse shock of a young supernova remnant

    International Nuclear Information System (INIS)

    Yamaguchi, Hiroya; Petre, Robert; Eriksen, Kristoffer A.; Badenes, Carles; Hughes, John P.; Brickhouse, Nancy S.; Foster, Adam R.; Patnaude, Daniel J.; Slane, Patrick O.; Smith, Randall K.

    2014-01-01

    Although collisionless shocks are ubiquitous in astrophysics, certain key aspects of them are not well understood. In particular, the process known as collisionless electron heating, whereby electrons are rapidly energized at the shock front, is one of the main open issues in shock physics. Here, we present the first clear evidence for efficient collisionless electron heating at the reverse shock of Tycho's supernova remnant (SNR), revealed by Fe K diagnostics using high-quality X-ray data obtained by the Suzaku satellite. We detect Kβ (3p → 1s) fluorescence emission from low-ionization Fe ejecta excited by energetic thermal electrons at the reverse shock front, which peaks at a smaller radius than Fe Kα (2p → 1s) emission dominated by a relatively highly ionized component. Comparisons with our hydrodynamical simulations imply instantaneous electron heating to a temperature 1000 times higher than expected from Coulomb collisions alone. The unique environment of the reverse shock, which is propagating with a high Mach number into rarefied ejecta with a low magnetic field strength, puts strong constraints on the physical mechanism responsible for this heating and favors a cross-shock potential created by charge deflection at the shock front. Our sensitive observation also reveals that the reverse shock radius of this SNR is about 10% smaller than the previous measurement using the Fe Kα morphology from the Chandra observations. Since strong Fe Kβ fluorescence is expected only from low-ionization plasma where Fe ions still have many 3p electrons, this feature is key to diagnosing the plasma state and distribution of the immediate postshock ejecta in a young SNR.

  8. New Evidence for Efficient Collisionless Heating of Electrons at the Reverse Shock of a Young Supernova Remnant

    Science.gov (United States)

    Yamaguchi, Hiroya; Eriksen, Kristoffer A.; Badenes, Carles; Hughes, John P.; Brickhouse, Nancy S.; Foster, Adam R.; Patnaude, Daniel J.; Petre, Robert; Slane, Patrick O.; Smith, Randall K.

    2013-01-01

    Although collisionless shocks are ubiquitous in astrophysics, certain key aspects of them are not well understood. In particular, the process known as collisionless electron heating, whereby electrons are rapidly energized at the shock front, is one of the main open issues in shock physics. Here, we present the first clear evidence for efficient collisionless electron heating at the reverse shock of Tycho's supernova remnant (SNR), revealed by Fe K diagnostics using high-quality X-ray data obtained by the Suzaku satellite. We detect K beta (3p yields 1s) fluorescence emission from low-ionization Fe ejecta excited by energetic thermal electrons at the reverse shock front, which peaks at a smaller radius than Fe K alpha (2p yields 1s) emission dominated by a relatively highly ionized component. Comparisons with our hydrodynamical simulations imply instantaneous electron heating to a temperature 1000 times higher than expected from Coulomb collisions alone. The unique environment of the reverse shock, which is propagating with a high Mach number into rarefied ejecta with a low magnetic field strength, puts strong constraints on the physical mechanism responsible for this heating and favors a cross-shock potential created by charge deflection at the shock front. Our sensitive observation also reveals that the reverse shock radius of this SNR is about 10% smaller than the previous measurement using the Fe K alpha morphology from the Chandra observations. Since strong Fe K beta fluorescence is expected only from low-ionization plasma where Fe ions still have many 3p electrons, this feature is key to diagnosing the plasma state and distribution of the immediate postshock ejecta in a young SNR.

  9. Plasmoid-Mediated Reconnection and Turbulence in Laboratory and Space Plasmas

    Science.gov (United States)

    Bhattacharjee, Amitava

    2017-10-01

    Among recent new developments, the so-called plasmoid instability of thin current sheets has challenged classical nonlinear reconnection models. Within the framework of the resistive MHD model, this instability alters qualitatively the predictions of the classical Sweet-Parker model, leading to a new nonlinear regime of fast reconnection in which the reconnection rate itself becomes independent of the Lundquist number. This regime has also been seen in Hall MHD as well as fully kinetic simulations. Plasmoids, which can grow by coalescence to large sizes, provide a powerful mechanism for coupling between large (global) and small (kinetic) scales as well as an efficient accelerator of particles to high energies. A new phase diagram of fast reconnection has been proposed, informing the design of experiments (such as the FLARE experiment at Princeton, and TREX at Madison). In 3D, the instability produces self-generated and strongly anisotropic turbulence in which the reconnection rate for the mean magnetic field remains approximately at the 2D value, but the energy spectrum deviates strongly from standard MHD turbulence phenomenology. Applications of the theory to observations in laboratory (including fusion) and space (both magnetospheric and solar) plasmas will be discussed.

  10. Comparative study of three reconnection X line models at the Earth's dayside magnetopause using in situ observations

    Science.gov (United States)

    Souza, V. M.; Gonzalez, W. D.; Sibeck, D. G.; Koga, D.; Walsh, B. M.; Mendes, O.

    2017-04-01

    This work examines the large-scale aspects of magnetic field reconnection at the Earth's dayside magnetopause. We use two sets of reconnection events, which are identified mostly by the in situ detection of accelerated and Alfvénic plasma flows. We intercompare three analytical models that predict the reconnection X line location and orientation, namely, the Trattner et al. (2007) and Swisdak and Drake (2007) models and also a modified version of the component merging model. In the first set of reconnection observations, we show three fortuitous, quasi-simultaneous dayside magnetopause crossing events where two widely separated spacecraft detect reconnection signatures, and the X line location and orientation can be inferred from the observations. We compare X line model predictions to those inferred from observations. These three reconnection events indicate the presence of an extended (>7 Earth radii in length), component-type reconnection X line on Earth's dayside magnetopause connecting and structuring the reconnection signatures at locations far apart. In the second set of reconnection events, we analyze the X line models' performance in predicting the observed reconnection outflow direction, i.e., its north-south and/or east-west senses, in a total of 75 single, rather than multiple and quasi-simultaneous, magnetopause crossing events, where reconnection-associated plasma flows were clearly present. We found that the Swisdak and Drake's (2007) X line model performs slightly better, albeit not statistically significant, when predicting both accelerated plasma flow north-south and east-west components in 73% and 53% of the cases, respectively, as compared to the Trattner et al. (2007) model (70% north-south and 42% east-west) and the modified component merging model (66% north-south and 50% east-west).

  11. Comparative Study of Three Reconnection X-Line Models at the Earth's Dayside Magnetopause Using In Situ Observations

    Science.gov (United States)

    Souza, V. M. C. E. S.; Gonzalez, W.; Sibeck, D. G.; Koga, D.; Walsh, B.; Mendes, O., Jr.

    2017-12-01

    This work examines the large-scale aspects of magnetic field reconnection at the Earth's dayside magnetopause. We use two sets of reconnection events, which are identified mostly by the in situ detection of accelerated and Alfvénic plasma flows. We intercompare three analytical models that predict the reconnection X-line location and orientation, namely the Trattner et al., (2007) and Swisdak and Drake (2007) models, and also a modified version of the component merging model (Gonzalez and Mozer 1974, Sonnerup 1974). In the first set of reconnection observations, we show three fortuitous, quasi-simultaneous dayside magnetopause crossing events where two widely separated spacecraft detect reconnection signatures, and the X-line location and orientation can be inferred from the observations. We compare X-line model predictions to those inferred from observations. These three reconnection events indicate the presence of an extended (>7 Earth radii in length), component-type reconnection X-line on Earth's dayside magnetopause connecting and structuring the reconnection signatures at locations far apart. In the second set of reconnection events, we analyze the X-line models' performance in predicting the observed reconnection outflow direction, i.e., its north-south and/or east-west senses, in a total of 75 single, rather than multiple and quasi-simultaneous, magnetopause crossing events, where reconnection-associated plasma flows were clearly present. We found that the Swisdak and Drake's (2007) X-line model performs slightly better, albeit not statistically significant, when predicting both accelerated plasma flow north-south and east-west components in 73% and 53% of the cases, respectively, as compared to the Trattner et al., (2007) model (70% north-south, 42% east-west), and the modified component merging model (66% north-south, 50% east-west).

  12. Collisionless coupling of a high- β expansion to an ambient, magnetized plasma. I. Rayleigh model and scaling

    Science.gov (United States)

    Bonde, Jeffrey

    2018-04-01

    The dynamics of a magnetized, expanding plasma with a high ratio of kinetic energy density to ambient magnetic field energy density, or β, are examined by adapting a model of gaseous bubbles expanding in liquids as developed by Lord Rayleigh. New features include scale magnitudes and evolution of the electric fields in the system. The collisionless coupling between the expanding and ambient plasma due to these fields is described as well as the relevant scaling relations. Several different responses of the ambient plasma to the expansion are identified in this model, and for most laboratory experiments, ambient ions should be pulled inward, against the expansion due to the dominance of the electrostatic field.

  13. Particle dynamics and current-free double layers in an expanding, collisionless, two-electron-population plasma

    Science.gov (United States)

    Hairapetian, G.; Stenzel, R. L.

    1991-01-01

    The expansion of a two-electron-population, collisionless plasma into vacuum has been examined in detail. Plasma density, plasma potential, electric field, and particle disribution functions have been measured in situ. It is demonstrated that the presence of a low-pressure (P not less than 2 x 10 to the -5th torr) background neutral gas modifies the expansion of the plasma. A new plasma source creating dense, pulsed discharge plasma with a low background pressure (P not greater than 2 x 10 to the -6th torr) has been developed to perform in situ measurements of the temporal and spatial plasma evolution during its expansion into vacuum.

  14. A closed set of conservation laws and the evolution of the electron magnetic moment in the collisionless solar wind

    International Nuclear Information System (INIS)

    Alexander, P.

    1993-01-01

    A hydromagnetic equation system for the interplanetary collisionless solar wind is used to derive a set of conservation laws for that medium. It is found that every equation of the original system, including the closure relation, is related to one conservation law. The set that has been derived does not only include the traditional laws, but also a new one for the magnetic moment of the electrons. The conservation set is then used to obtain the space constants for the solar coronal expansion. The new law yields a constant that has not been predicted by other models

  15. Library of Cards: Reconnecting the Scholar and the Library

    Directory of Open Access Journals (Sweden)

    Mita Williams

    2016-03-01

    Full Text Available This paper is based on a presentation I gave at the Access Conference in Toronto, Ontario on September 10th, 2015. Both the presentation and this paper are explorations in three parts. The first part is a short history lesson on the use of paper cards by scholars and librarians, which led to the introduction of the “Scholar’s Box.” The second part asks the question: Can we consider Zotero as the Scholar’s Box of the digital age when it cannot capture important metadata such as linked open data? It is recognized that this is not just a shortcoming of Zotero: research is surprisingly still very difficult to share between scholars, libraries, and writing tools. This is due to an inability to capture the “invisible text” when we copy and paste citations from one application to another. The third part establishes that the digital card is now the dominant design pattern of web and mobile, and notes that these systems are largely restricted to proprietary platforms, which restricts the movement of cards between systems. This paper then suggests how we might transform the historical Scholar’s Box, by using HTML5 index cards from Cardstack.io as a means to bring new forms of sharing on the web, and, in doing so, reconnect the scholar to the library. Cet article est basé sur un exposé que j’ai donné à Access Conference à Toronto le 10 septembre 2015. L’exposé et cet article sont des explorations en trois parties. La première partie est une leçon d’histoire courte sur l’usage des cartes en papier par les spécialistes et les bibliothécaires, qui a mené à l’introduction du “Scholar’s Box”. La seconde partie pose la question: Est-ce que nous pouvons considérer Zotero comme le “Scholar’s Box” de l’âge numérique, même s’il ne peut pas capturer des métadonnées importantes telles que les données liées ouvertes? On reconnaît que ce n’est pas seulement une lacune de Zotero: étonnement, la recherche est

  16. An Integrative Review of Scientific Evidence for Reconnective Healing.

    Science.gov (United States)

    Baldwin, Ann L; Trent, Natalie L

    2017-08-01

    Biofield therapies offer a novel, non-invasive approach to treating chronic diseases based on assessing and adjusting an individual's physiological and emotional responses through their bio-energetic field. Reconnective Healing ™ (RH) is defined as: "…not just energy healing, but instead a more comprehensive spectrum of healing composed of energy, light, and information." Several biofield therapies, such as Reiki, Therapeutic Touch and Johrei, have already been reviewed in the literature but RH has received little attention even though it is taught and practiced worldwide. This review provides a critical assessment of RH as a healing modality. Scientific research articles published in peer-reviewed journals addressing RH were identified using relevant databases and archives. Information was extracted from each article that met selection criteria for evaluation of quality of reporting and design. This review summarizes and critically evaluates the five currently published peer-reviewed research papers involving RH and assesses whether RH provides consistent physiological outcomes between the studies. These results, taken together, suggest: (i) exposure of a healer or healee to RH, either directly or indirectly, amplifies their degree of autonomic arousal and energy, (ii) RH can reduce pain and improve range of motion in people with shoulder limitations, and (iii) when individuals experience RH as a group, their autonomic nervous systems simultaneously show sudden similar responses consistent with the idea that RH is mitigated by entrainment of biofields. Since these studies are extremely varied in design it is not possible at this point to reach conclusions about the general effectiveness of RH. More clinical and physiological research performed on different populations under a range of conditions is needed in order to support this healthcare approach.

  17. Polarisation of microwave emission from reconnecting twisted coronal loops

    Science.gov (United States)

    Gordovskyy, M.; Browning, P. K.; Kontar, E. P.

    2017-08-01

    Context. Magnetic reconnection and particle acceleration due to the kink instability in twisted coronal loops can be a viable scenario for confined solar flares. Detailed investigation of this phenomenon requires reliable methods for observational detection of magnetic twist in solar flares, which may not be possible solely through extreme UV and soft X-ray thermal emission. Polarisation of microwave emission in flaring loops can be used as one of the detection criteria. Aims: The aim of this study is to investigate the effect of magnetic twist in flaring coronal loops on the polarisation of gyro-synchrotron microwave (GSMW) emission, and determine whether it could provide a means for magnetic twist detection. Methods: We consider time-dependent magnetohydrodynamic and test-particle models developed using the LARE3D and GCA codes to investigate twisted coronal loops that relax after kink instability. Synthetic GSMW emission maps (I and V Stokes components) are calculated using GX simulator. Results: It is found that flaring twisted coronal loops produce GSMW radiation with a gradient of circular polarisation across the loop. However, these patterns may be visible only for a relatively short period of time owing to fast magnetic reconfiguration after the instability. Their visibility also depends on the orientation and position of the loop on the solar disk. Typically, it would be difficult to see these characteristic polarisation patterns in a twisted loop seen from the top (I.e. close to the centre of the solar disk), but easier in a twisted loop seen from the side (I.e. observed very close to the limb).

  18. Cosmic rays and stochastic magnetic reconnection in the heliotail

    Directory of Open Access Journals (Sweden)

    P. Desiati

    2012-06-01

    Full Text Available Galactic cosmic rays are believed to be generated by diffusive shock acceleration processes in Supernova Remnants, and the arrival direction is likely determined by the distribution of their sources throughout the Galaxy, in particular by the nearest and youngest ones. Transport to Earth through the interstellar medium is expected to affect the cosmic ray properties as well. However, the observed anisotropy of TeV cosmic rays and its energy dependence cannot be explained with diffusion models of particle propagation in the Galaxy. Within a distance of a few parsec, diffusion regime is not valid and particles with energy below about 100 TeV must be influenced by the heliosphere and its elongated tail. The observation of a highly significant localized excess region of cosmic rays from the apparent direction of the downstream interstellar flow at 1–10 TeV energies might provide the first experimental evidence that the heliotail can affect the transport of energetic particles. In particular, TeV cosmic rays propagating through the heliotail interact with the 100–300 AU wide magnetic field polarity domains generated by the 11 yr cycles. Since the strength of non-linear convective processes is expected to be larger than viscous damping, the plasma in the heliotail is turbulent. Where magnetic field domains converge on each other due to solar wind gradient, stochastic magnetic reconnection likely occurs. Such processes may be efficient enough to re-accelerate a fraction of TeV particles as long as scattering processes are not strong. Therefore, the fractional excess of TeV cosmic rays from the narrow region toward the heliotail direction traces sightlines with the lowest smearing scattering effects, that can also explain the observation of a harder than average energy spectrum.

  19. An Integrative Review of Scientific Evidence for Reconnective Healing

    Science.gov (United States)

    Trent, Natalie L.

    2017-01-01

    Abstract Background: Biofield therapies offer a novel, non-invasive approach to treating chronic diseases based on assessing and adjusting an individual's physiological and emotional responses through their bio-energetic field. Reconnective Healing™ (RH) is defined as: “…not just energy healing, but instead a more comprehensive spectrum of healing composed of energy, light, and information.” Objectives: Several biofield therapies, such as Reiki, Therapeutic Touch and Johrei, have already been reviewed in the literature but RH has received little attention even though it is taught and practiced worldwide. This review provides a critical assessment of RH as a healing modality. Methods: Scientific research articles published in peer-reviewed journals addressing RH were identified using relevant databases and archives. Information was extracted from each article that met selection criteria for evaluation of quality of reporting and design. This review summarizes and critically evaluates the five currently published peer-reviewed research papers involving RH and assesses whether RH provides consistent physiological outcomes between the studies. Results: These results, taken together, suggest: (i) exposure of a healer or healee to RH, either directly or indirectly, amplifies their degree of autonomic arousal and energy, (ii) RH can reduce pain and improve range of motion in people with shoulder limitations, and (iii) when individuals experience RH as a group, their autonomic nervous systems simultaneously show sudden similar responses consistent with the idea that RH is mitigated by entrainment of biofields. Conclusions: Since these studies are extremely varied in design it is not possible at this point to reach conclusions about the general effectiveness of RH. More clinical and physiological research performed on different populations under a range of conditions is needed in order to support this healthcare approach. PMID:28654301

  20. Transition form collisional to kinetic reconnection in large-scale plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Daughton, William S [Los Alamos National Laboratory; Roytershteyn, Vadim S [Los Alamos National Laboratory; Albright, Brian J [Los Alamos National Laboratory; Yin, Lin [Los Alamos National Laboratory; Bowers, Kevin J [Los Alamos National Laboratory; Karimabadi, Homa [UCSD

    2009-01-01

    Using first-principles fully kinetic simulations with a Fokker-Planck collision operator, it is demonstrated that Sweet-Parker reconnection layers are unstable to a chain of plasmoids (secondary islands) for Lundquist numbers beyond S >{approx} 1000. The instability is increasingly violent at higher Lundquist number, both in terms of the number of plasmoids produced and the super-Alfvenic growth rate. A dramatic enhancement in the reconnection rate is observed when the half-thickness of the current sheet between two plasmoids approaches the ion inertial length. During this transition, the reconnection electric field rapidly exceeds the runaway limit, resulting in the formation of electron-scale current layers that are unstable to the continual formation of new plasmoids.

  1. RECONNECTION IN THREE DIMENSIONS: THE ROLE OF SPINES IN THREE ERUPTIVE FLARES

    International Nuclear Information System (INIS)

    Jardins, Angela Des; Canfield, Richard; Longcope, Dana; Fordyce, Crystal; Waitukaitis, Scott

    2009-01-01

    In order to better understand magnetic reconnection and particle acceleration in solar flares, we compare the RHESSI hard X-ray (HXR) footpoint motions of three flares with a detailed study of the corresponding topology given by a Magnetic Charge Topology model. We analyze the relationship between the footpoint motions and topological spine lines and find that the examined footpoint sources move along spine lines. We present a three-dimensional topological model in which this movement can be understood. As reconnection proceeds, flux is transferred between the reconnecting domains, causing the separator to move. The movement of the separator's chromospheric ends, identified with the HXR footpoints, is along those spine lines on which the separator ends.

  2. Formation of hard power laws in the energetic particle spectra resulting from relativistic magnetic reconnection.

    Science.gov (United States)

    Guo, Fan; Li, Hui; Daughton, William; Liu, Yi-Hsin

    2014-10-10

    Using fully kinetic simulations, we demonstrate that magnetic reconnection in relativistic plasmas is highly efficient at accelerating particles through a first-order Fermi process resulting from the curvature drift of particles in the direction of the electric field induced by the relativistic flows. This mechanism gives rise to the formation of hard power-law spectra in parameter regimes where the energy density in the reconnecting field exceeds the rest mass energy density σ ≡ B(2)/(4πnm(e)c(2))>1 and when the system size is sufficiently large. In the limit σ ≫ 1, the spectral index approaches p = 1 and most of the available energy is converted into nonthermal particles. A simple analytic model is proposed which explains these key features and predicts a general condition under which hard power-law spectra will be generated from magnetic reconnection.

  3. The Kelvin-Helmholtz instability, differential rotation, and three-dimensional, localized, magnetic reconnection

    International Nuclear Information System (INIS)

    Knoll, D.A.; Brackbill, J.U.

    2002-01-01

    Results are presented from a study of three-dimensional magnetic reconnection caused by a Kelvin-Helmholtz instability and differential rotation. Specifically, subsonic and sub-Alfvenic flow is considered, which is Kelvin-Helmholtz stable in the direction of the magnetic field, but unstable perpendicular to the magnetic field. The flow is modeled by the resistive magnetohydrodynamics equations in three dimensions with constant resistivity. As a result of differential rotation (a gradient in vorticity parallel to the initial field), localized transient reconnection is observed on the Kelvin-Helmholtz time scale. Current amplification is observed along with the generation of parallel current. Results indicate that the observed transient reconnection rate is insensitive to resistivity (even with a constant resistivity model), but is sensitive to the initial flow shear

  4. Splitter target for controlling magnetic reconnection in relativistic laser plasma interactions

    Science.gov (United States)

    Gu, Y. J.; Bulanov, S. S.; Korn, G.; Bulanov, S. V.

    2018-04-01

    The utilization of a conical target irradiated by a high power laser is proposed to study fast magnetic reconnection in relativistic plasma interactions. Such target, placed in front of the near critical density gas jet, splits the laser pulse, forming two parallel laser pulses in the 2D case and a donut shaped pulse in the 3D case. The magnetic annihilation and reconnection occur in the density downramp region of the subsequent gas jet. The magnetic field energy is converted into the particle kinetic energy. As a result, a backward accelerated electron beam is obtained as a signature of reconnection. The above mechanisms are demonstrated using particle-in-cell simulations in both 2D and 3D cases. Facilitating the synchronization of two laser beams, the proposed approach can be used in designing the corresponding experiments on studying fundamental problems of relativistic plasma physics.

  5. Recovery through reconnection: a cultural design for family bereavement in Taiwan.

    Science.gov (United States)

    Hsu, Min-Tao; Kahn, David L; Yee, Der-Heuy; Lee, Wei-Lun

    2004-10-01

    Using reanalyzed data from ethnographic research performed in Taiwan during the 1990s, the authors inspect Taiwanese cultural patterns as they affect adaptation to loss in the form of death. The data include participant observations and the narratives of 52 widows and 30 of their children. An analysis of interview transcripts suggests that the most common form of return to a harmony house among the participants was achieving a sense of reconnection with the deceased. According to the narratives, the Taiwanese concept of reconnection entails (a) maintaining the status quo, (b) restoring images of the deceased in family affairs, and (c) communicating with the dead. Each theme represents the efforts of bereaved families to retain a sense of wholeness (a central Chinese goal) and to preserve symbolic images of fathers and husbands. The authors suggest that reconnection is a culturally specific and accepted means of resolving grief among Taiwanese.

  6. Numerical simulation of ion dynamics in the magnetotail magnetic turbulence: On collisionless conductivity

    Directory of Open Access Journals (Sweden)

    A. Greco

    2000-01-01

    Full Text Available The ion dynamics in the distant Earth's magnetotail is studied in the case that a cross tail electric field and reconnection parity magnetic turbulence are present in the neutral sheet. A test particle simulation is performed for the ions, and moments of the ion distribution function are obtained as a function of the magnetic fluctuation level, δB/B0, and of the value of the cross tail electric field, Ey. It is found that magnetic turbulence can split the current carrying region into a double current sheet, in agreement with inferences from observations in the distant magnetotail. The problem of ion conductivity is addressed by varying the value of the cross tail electric field from zero to the observed one: we find that Ohm's law is not enforced, and that a non local, system dependent conductivity is necessary to describe the ion response to the electric field. Also, it appears that the relation between current and electric field may be nonlinear.

  7. Kinetic Model of Electric Potentials in Localized Collisionless Plasma Structures under Steady Quasi-gyrotropic Conditions

    Science.gov (United States)

    Schindler, K.; Birn, J.; Hesse, M.

    2012-01-01

    Localized plasma structures, such as thin current sheets, generally are associated with localized magnetic and electric fields. In space plasmas localized electric fields not only play an important role for particle dynamics and acceleration but may also have significant consequences on larger scales, e.g., through magnetic reconnection. Also, it has been suggested that localized electric fields generated in the magnetosphere are directly connected with quasi-steady auroral arcs. In this context, we present a two-dimensional model based on Vlasov theory that provides the electric potential for a large class of given magnetic field profiles. The model uses an expansion for small deviation from gyrotropy and besides quasineutrality it assumes that electrons and ions have the same number of particles with their generalized gyrocenter on any given magnetic field line. Specializing to one dimension, a detailed discussion concentrates on the electric potential shapes (such as "U" or "S" shapes) associated with magnetic dips, bumps, and steps. Then, it is investigated how the model responds to quasi-steady evolution of the plasma. Finally, the model proves useful in the interpretation of the electric potentials taken from two existing particle simulations.

  8. Structure of Exhausts in Magnetic Reconnection with an X-line of Finite Extent

    Energy Technology Data Exchange (ETDEWEB)

    Shepherd, L. S.; Cassak, P. A. [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States); Drake, J. F. [Department of Physics and the Institute for Physical Science and Technology and the Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742 (United States); Gosling, J. T. [Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, CO 80303 (United States); Phan, T.-D. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Shay, M. A. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

    2017-10-20

    We present quantitative predictions of the structure of reconnection exhausts in three-dimensional magnetic reconnection with an X-line of finite extent in the out-of-plane direction. Sasunov et al. showed that they have a tilted ribbon-like shape bounded by rotational discontinuities and tangential discontinuities. We show analytically and numerically that this prediction is largely correct. When there is an out-of-plane (guide) magnetic field, the presence of the upstream field that does not reconnect acts as a boundary condition in the normal direction, which forces the normal magnetic field to be zero outside the exhaust. This condition constrains the normal magnetic field inside the exhaust to be small. Thus, rather than the ribbon tilting in the inflow direction, the exhaust remains collimated in the normal direction and is forced to expand nearly completely in the out-of-plane direction. This exhaust structure is in stark contrast to the two-dimensional picture of reconnection, where reconnected flux expands in the normal direction. We present analytical predictions for the structure of the exhausts in terms of upstream conditions. The predictions are confirmed using three-dimensional resistive-magnetohydrodynamic simulations with a finite-length X-line achieved using a localized (anomalous) resistivity. Implications to reconnection in the solar wind are discussed. In particular, the results can be used to estimate a lower bound for the extent of the X-line in the out-of-plane direction solely using single-spacecraft data taken downstream in the exhausts.

  9. Aspect Ratio Effects in the Driven, Flux-Core Spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, E B; Romero-Talam?s, C A; LoDestro, L L; Wood, R D; McLean, H S

    2009-03-02

    Resistive magneto-hydrodynamic simulations are used to evaluate the effects of the aspect ratio, A (length to radius ratio) in a spheromak driven by coaxial helicity injection. The simulations are benchmarked against the Sustained Spheromak Physics Experiment (SSPX) [R. D. Wood, et al., Nucl. Nucl. Fusion 45, 1582 (2005)]. Amplification of the bias ('gun') poloidal flux is fit well by a linear dependence (insensitive to A) on the ratio of gun current and bias flux above a threshold dependent on A. For low flux amplifications in the simulations the n = 1 mode is coherent and the mean-field geometry looks like a tilted spheromak. Because the mode has relatively large amplitude the field lines are open everywhere, allowing helicity penetration. Strongly-driven helicity injection at A {le} 1.4 in simulations generates reconnection events which open the magnetic field lines; this state is characteristic of SSPX. Near the spheromak tilt-mode limit, A {approx} 1.67 for a cylindrical flux conserver, the tilt approaches 90{sup o}; reconnection events are not generated up to the strongest drives simulated. The time-sequence of these events suggests that they are representative of a chaotic process. Implications for spheromak experiments are discussed.

  10. The history of re-connection and the concept of the solar wind plasma with relatively small electrical conductivity

    Science.gov (United States)

    Chertkov, A. D.

    1995-01-01

    Petschek's 're-connection' model, aspiring to be universal, treated as a boundary problem meets unresolvable difficulties connected with impossibility to specify correctly boundary and initial conditions. This problem was incorrectly formulated. Hence, ineradicable logarithmic singularities occurred on the boundary surfaces. Attempts to eliminate them by incorporating the finite electrical conductivity are incorrect. This should lead to the change in the equation type, boundary condition type and in consequence to the change in solutions. Besides, the slow mode shocks cannot be driven by small internal source. As an alternative a new plasma concept is suggested. The state of fully ionized plasma in space depends completely on the entropy of the plasma heating source and on the process in which plasma is involved. The presumptive source of the solar wind creation - the induction electric field of the solar origin - has very low entropy. The state of plasma should be very far from the thermodynamic equilibrium. Debye's screening is not complete. The excitation of the powerful resonant self-consistent electric fields in plasma provides low electric conductivity. The MHD problems should be treated in frameworks of dissipative theories.

  11. THE EFFECT OF LARGE-SCALE MAGNETIC TURBULENCE ON THE ACCELERATION OF ELECTRONS BY PERPENDICULAR COLLISIONLESS SHOCKS

    International Nuclear Information System (INIS)

    Guo Fan; Giacalone, Joe

    2010-01-01

    We study the physics of electron acceleration at collisionless shocks that move through a plasma containing large-scale magnetic fluctuations. We numerically integrate the trajectories of a large number of electrons, which are treated as test particles moving in the time-dependent electric and magnetic fields determined from two-dimensional hybrid simulations (kinetic ions and fluid electron). The large-scale magnetic fluctuations effect the electrons in a number of ways and lead to efficient and rapid energization at the shock front. Since the electrons mainly follow along magnetic lines of force, the large-scale braiding of field lines in space allows the fast-moving electrons to cross the shock front several times, leading to efficient acceleration. Ripples in the shock front occurring at various scales will also contribute to the acceleration by mirroring the electrons. Our calculation shows that this process favors electron acceleration at perpendicular shocks. The current study is also helpful in understanding the injection problem for electron acceleration by collisionless shocks. It is also shown that the spatial distribution of energetic electrons is similar to in situ observations. The process may be important to our understanding of energetic electrons in planetary bow shocks and interplanetary shocks, and explaining herringbone structures seen in some type II solar radio bursts.

  12. Physics of the intermediate layer between a plasma and a collisionless sheath and mathematical meaning of the Bohm criterion

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, N. A.; Benilov, M. S. [Departamento de Fisica, CCCEE, Universidade da Madeira Largo do Municipio, 9000 Funchal (Portugal)

    2012-07-15

    A transformation of the ion momentum equation simplifies a mathematical description of the transition layer between a quasi-neutral plasma and a collisionless sheath and clearly reveals the physics involved. Balance of forces acting on the ion fluid is delicate in the vicinity of the sonic point and weak effects come into play. For this reason, the passage of the ion fluid through the sonic point, which occurs in the transition layer, is governed not only by inertia and electrostatic force but also by space charge and ion-atom collisions and/or ionization. Occurrence of different scenarios of asymptotic matching in the plasma-sheath transition is analyzed by means of simple mathematical examples, asymptotic estimates, and numerical calculations. In the case of a collisionless sheath, the ion speed distribution plotted on the logarithmic scale reveals a plateau in the intermediate region between the sheath and the presheath. The value corresponding to this plateau has the meaning of speed with which ions leave the presheath and enter the sheath; the Bohm speed. The plateau is pronounced reasonably well provided that the ratio of the Debye length to the ion mean free path is of the order of 10{sup -3} or smaller. There is no such plateau if the sheath is collisional and hence no sense in talking of a speed with which ions enter the sheath.

  13. The dynamics of electron and ion holes in a collisionless plasma

    Directory of Open Access Journals (Sweden)

    B. Eliasson

    2005-01-01

    Full Text Available We present a review of recent analytical and numerical studies of the dynamics of electron and ion holes in a collisionless plasma. The new results are based on the class of analytic solutions which were found by Schamel more than three decades ago, and which here work as initial conditions to numerical simulations of the dynamics of ion and electron holes and their interaction with radiation and the background plasma. Our analytic and numerical studies reveal that ion holes in an electron-ion plasma can trap Langmuir waves, due the local electron density depletion associated with the negative ion hole potential. Since the scale-length of the ion holes are on a relatively small Debye scale, the trapped Langmuir waves are Landau damped. We also find that colliding ion holes accelerate electron streams by the negative ion hole potentials, and that these streams of electrons excite Langmuir waves due to a streaming instability. In our Vlasov simulation of two colliding ion holes, the holes survive the collision and after the collision, the electron distribution becomes flat-topped between the two ion holes due to the ion hole potentials which work as potential barriers for low-energy electrons. Our study of the dynamics between electron holes and the ion background reveals that standing electron holes can be accelerated by the self-created ion cavity owing to the positive electron hole potential. Vlasov simulations show that electron holes are repelled by ion density minima and attracted by ion density maxima. We also present an extension of Schamel's theory to relativistically hot plasmas, where the relativistic mass increase of the accelerated electrons have a dramatic effect on the electron hole, with an increase in the electron hole potential and in the width of the electron hole. A study of the interaction between electromagnetic waves with relativistic electron holes shows that electromagnetic waves can be both linearly and nonlinearly

  14. Particle acceleration in relativistic magnetized collisionless pair shocks: a survey of magnetic inclination angles

    Science.gov (United States)

    Sironi, Lorenzo

    We investigate particle acceleration in relativistic magnetized collisionless pair shocks with two-dimensional particle-in-cell numerical simulations. For fixed upstream bulk Lorentz factor γ0 = 15 and magnetic to kinetic energy fraction σ = 0.1, we explore a range of inclination angles θ between the magnetic field and the shock normal. The inclination is measured in the downstream rest frame and the magnetic field lies in a plane perpendicular to the simulation plane. The downstream energy spectrum for subluminal shocks consists of a relativistic Maxwellian and a high-energy power-law tail modified by an exponential cutoff. For parallel shocks (θ = 0° ), the tail accounts for ˜ 1% of the downstream particle number and ˜ 5% of the energy, and its energy spectral index is -2.7 ± 0.1. Accelerated particles bounce between the upstream and the downstream, and the upstream scattering is provided by oblique filaments, which have both an electromagnetic and an electrostatic component. Such filaments propagate towards the shock and are generated by the accelerated particles that escape upstream. For larger inclination angles the acceleration efficiency increases, and particles are efficiently boosted by the motional upstream electric field when gyrating across the shock. Close to the superluminality threshold θ ≈ 30° , the number and energy fractions of downstream accelerated particles are ˜ 3% and ˜ 12% respectively; the spectral index of the corresponding power-law tail is -2.4 ± 0.1. When the shock becomes superluminal (θ 30° ), the acceleration efficiency abruptly drops. Our results show that the range of upstream-frame inclination angles suitable for efficient acceleration in relativistic magnetized pair shocks is indeed very small 30° /γ0 , as suggested by previous Monte-Carlo simulations. Self-generated shock turbulence is shown to be not large enough to overcome the kinematic constraints for superluminal shocks. These findings place constraints

  15. MR-2016 US-Japan Workshop on Magentic Reconnection Travel Support

    Energy Technology Data Exchange (ETDEWEB)

    Forest, Cary [Univ. of Wisconsin, Madison, WI (United States)

    2017-06-12

    The US-Japan workshop on Magnetic Reconnection (MR2016), was held in Napa California from March 7th through 11th, 2016. Details about the program, including invited speakers can be found here: (http://www.magneticreconnection.org/mr2016). Background: The MR Workshop is an international meeting that began in 2000 with its original focus on magnetic reconnection serving as a link between the research groups in US and Japan. Since then, the meeting has grown and is now recognized as one of the primary international workshops on magnetic reconnection. In its format, researchers from both the laboratory community and from the space research community have held 12 workshops bringing together the diverse researchers from the space and laboratory experimental fields. Plasma physics is the common language that ties together all scientists who study the waves, particle acceleration and heating, magnetic reconnection, dynamos, global and micro-stability of plasmas, magnetic turbulence and plasma’s transport problems. The meeting received $9,575 from the U.S. Dept. of Energy funding. This support was used to cover the registration fees ($575 per person) and accommodations for ten junior colleagues (graduate students and postdocs). Applications were solicited and then reviewed by the program committee based on recommendations from the applicants’ advisers.

  16. Magnetic reconnection in Earth's magnetotail: Energy conversion and its earthward-tailward asymmetry

    Science.gov (United States)

    Lu, San; Pritchett, P. L.; Angelopoulos, V.; Artemyev, A. V.

    2018-01-01

    Magnetic reconnection, a fundamental plasma process, releases magnetic energy and converts it to particle energy, by accelerating and heating ions and electrons. This energy conversion plays an important role in the Earth's magnetotail. A two-dimensional particle-in-cell simulation is performed to study such a conversion in a magnetotail topology, one with a nonzero Bz, and the energy conversion is found to be more efficient in the earthward outflow than in the tailward outflow. Such earthward-tailward asymmetry is manifested not only in j .E but also in Poynting flux, Hall electromagnetic fields, bulk kinetic energy flux, enthalpy flux, heat flux, bulk acceleration, heating, and suprathermal particle energization, all of which are more prevalent on the earthward side. Such asymmetries are consistent with spacecraft observations reported in the literature. Our study shows that in the magnetotail, most of the energy converted by reconnection flows predominantly toward the Earth and has the potential of being geoeffective, rather than being expelled to the solar wind by the tailward flow. The energy conversion asymmetry arises from the presence of the non-zero normal magnetic field, the stronger lobe magnetic field, and the stronger cross-tail current earthward of the reconnection site in the pre-reconnecting thin current sheet.

  17. Measurement of ion velocity profiles in a magnetic reconnection layer via current sheet jogging

    Science.gov (United States)

    Stein, G.; Yoo, J.; Yamada, M.; Ji, H.; Dorfman, S.; Lawrence, E.; Myers, C.; Tharp, T.

    2011-10-01

    In many laboratory plasmas, constructing stationary Langmuir and Mach probe arrays with resolution on the order of electron skin depth is technically difficult, and can introduce significant plasma perturbations. However, complete two- dimensional profiles of plasma density, electron temperature, and ion flow are important for studying the transfer of energy from magnetic fields to particles during magnetic reconnection. Through the use of extra ``Shaping Field'' coils in the Magnetic Reconnection Experiment (MRX) at the Princeton Plasma Physics Laboratory, the inward motion of the current sheet in the reconnection layer can be accelerated, or ``jogged,'' allowing the measurement of different points across the sheet with stationary probes. By acquiring data from Langmuir probes and Mach probes at different locations in the MRX with respect to the current sheet center, profiles of electron density and temperature and a vector plot of two-dimensional ion velocity in the plane of reconnection are created. Results from probe measurements will be presented and compared to profiles generated from computer simulation.

  18. Generation mechanism of the whistler-mode waves in the plasma sheet prior to magnetic reconnection

    Czech Academy of Sciences Publication Activity Database

    Wei, X. H.; Cao, J. B.; Zhou, G. C.; Fu, H. S.; Santolík, Ondřej; Reme, H.; Dandouras, I.; Cornilleau, N.; Fazakerley, A.

    2013-01-01

    Roč. 52, č. 1 (2013), s. 205-210 ISSN 0273-1177 Institutional support: RVO:68378289 Keywords : whistler-mode waves * electron temperature anisotropy * Reconnection * the plasma sheet Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.238, year: 2013 http://www.sciencedirect.com/science/article/pii/S0273117713001221

  19. Magnetic reconnection in 3D magnetosphere models: magnetic separators and open flux production

    Science.gov (United States)

    Glocer, A.; Dorelli, J.; Toth, G.; Komar, C. M.; Cassak, P.

    2014-12-01

    There are multiple competing definitions of magnetic reconnection in 3D (e.g., Hesse and Schindler [1988], Lau and Finn [1990], and Boozer [2002]). In this work we focus on separator reconnection. A magnetic separator can be understood as the 3D analogue of a 2D x line with a guide field, and is defined by the line corresponding to the intersection of the separatrix surfaces associated with the magnetic nulls. A separator in the magnetosphere represents the intersection of four distinct magnetic topologies: solar wind, closed, open connected to the northern hemisphere, and open connected to the southern hemisphere. The integral of the parallel electric field along the separator defines the rate of open flux production, and is one measure of the reconnection rate. We present three methods for locating magnetic separators and apply them to 3D resistive MHD simulations of the Earth's magnetosphere using the BATS-R-US code. The techniques for finding separators and determining the reconnection rate are insensitive to IMF clock angle and can in principle be applied to any magnetospheric model. The present work examines cases of high and low resistivity, for two clock angles. We also examine the separator during Flux Transfer Events (FTEs) and Kelvin-Helmholtz instability.

  20. Dynamics and waves near multiple magnetic null points in reconnection diffusion region

    Czech Academy of Sciences Publication Activity Database

    Deng, X. H.; Zhou, M.; Li, S. Y.; Baumjohann, W.; Andre, M.; Cornilleau, N.; Santolík, Ondřej; Pontin, D. I.; Reme, H.; Lucek, E.; Fazakerley, A. N.; Decreau, P.; Daly, P.; Nakamura, R.; Tang, R. X.; Hu, Y. H.; Pang, Y.; Büchner, J.; Zhao, H.; Vaivads, A.; Pickett, J. S.; Ng, C. S.; Lin, X.; Fu, S.; Yuan, Z. G.; Su, Z. W.; Wang, J. F.

    2009-01-01

    Roč. 114, - (2009), A07216/1-A07216/7 ISSN 0148-0227 Institutional research plan: CEZ:AV0Z30420517 Keywords : waves * dynamics * reconnection * diffusion Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.082, year: 2009

  1. A study of different colour reconnection settings for Pythia8 generator using underlying event observables

    CERN Document Server

    The ATLAS collaboration

    2017-01-01

    A study of the performance of various colour reconnection models included in the Pythia8 Monte Carlo event generator is performed using leading charged-particle underlying event data in three centre-of-mass energies from Run 1 and Run 2, measured in ATLAS. Each model can be tuned to describe the data reasonably well.

  2. SLIPPING MAGNETIC RECONNECTIONS WITH MULTIPLE FLARE RIBBONS DURING AN X-CLASS SOLAR FLARE

    International Nuclear Information System (INIS)

    Zheng, Ruisheng; Chen, Yao; Wang, Bing

    2016-01-01

    With the observations of the Solar Dynamics Observatory , we present the slipping magnetic reconnections with multiple flare ribbons (FRs) during an X1.2 eruptive flare on 2014 January 7. A center negative polarity was surrounded by several positive ones, and three FRs appeared. The three FRs showed apparent slipping motions, and hook structures formed at their ends. Due to the moving footpoints of the erupting structures, one tight semi-circular hook disappeared after the slippage along its inner and outer edges, and coronal dimmings formed within the hook. The east hook also faded as a result of the magnetic reconnection between the arcades of a remote filament and a hot loop that was impulsively heated by the under flare loops. Our results are accordant with the slipping magnetic reconnection regime in three-dimensional standard model for eruptive flares. We suggest that the complex structures of the flare are likely a consequence of the more complex flux distribution in the photosphere, and the eruption involves at least two magnetic reconnections.

  3. Magnetic reconnection and stochastic plasmoid chains in high-Lundquist-number plasmas

    KAUST Repository

    Loureiro, N. F.

    2012-04-13

    A numerical study of magnetic reconnection in the large-Lundquist-number (S), plasmoid-dominated regime is carried out for S up to 10 7. The theoretical model of Uzdensky [Phys. Rev. Lett. 105, 235002 (2010)] is confirmed and partially amended. The normalized reconnection rate is Ẽ eff ∼ 0.02 independently of S for S ≫ 10 4. The plasmoid flux (ψ) and half-width (w x) distribution functions scale as f (ψ) ∼ - ψ -2 and f (w x) ∼ w x -2. The joint distribution of ψ and w x shows that plasmoids populate a triangular region w x ≲ψ/B 0, where B 0 is the reconnecting field. It is argued that this feature is due to plasmoid coalescence. Macroscopic "monster" plasmoids with w x ∼ 10 % of the system size are shown to emerge in just a few Alfvén times, independently of S, suggesting that large disruptive events are an inevitable feature of large-S reconnection. © 2012 American Institute of Physics.

  4. Magnetic Reconnection as a Driver for a Sub-ion-scale Cascade in Plasma Turbulence

    Czech Academy of Sciences Publication Activity Database

    Franci, L.; Cerri, S.S.; Califano, F.; Landi, S.; Papini, E.; Verdini, A.; Matteini, L.; Jenko, F.; Hellinger, Petr

    2017-01-01

    Roč. 850, č. 1 (2017), L16/1-L16/6 ISSN 2041-8205 R&D Projects: GA ČR GA15-10057S Institutional support: RVO:67985815 Keywords : magnetic reconnection * solar wind * turbulence Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 5.522, year: 2016

  5. Electron Acceleration by Cascading Reconnection in the Solar Corona. II. Resistive Electric Field Effects

    Czech Academy of Sciences Publication Activity Database

    Zhou, X.; Büchner, J.; Bárta, Miroslav; Gan, W.; Liu, S.

    2016-01-01

    Roč. 827, č. 2 (2016), 94/1-94/14 ISSN 0004-637X Institutional support: RVO:67985815 Keywords : acceleration of particles * magnetic reconnection * magnetohydrodynamics Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.533, year: 2016

  6. Electron Acceleration by Cascading Reconnection in the Solar Corona. I. Magnetic Gradient and Curvature Drift Effects

    Czech Academy of Sciences Publication Activity Database

    Zhou, X.; Büchner, J.; Bárta, Miroslav; Gan, W.; Liu, S.

    2015-01-01

    Roč. 815, č. 1 (2015), 6/1-6/17 ISSN 0004-637X Institutional support: RVO:67985815 Keywords : acceleration of particles * magnetic reconnection * magnetohydrodynamics Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.909, year: 2015

  7. Constraining reconnection region conditions using imaging and spectroscopic analysis of a coronal jet

    Science.gov (United States)

    Brannon, Sean; Kankelborg, Charles

    2017-08-01

    Coronal jets typically appear as thin, collimated structures in EUV and X-ray wavelengths, and are understood to be initiated by magnetic reconnection in the lower corona or upper chromosphere. Plasma that is heated and accelerated upward into coronal jets may therefore carry indirect information on conditions in the reconnection region and current sheet located at the jet base. On 2017 October 14, the Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) observed a series of jet eruptions originating from NOAA AR 12599. The jet structure has a length-to-width ratio that exceeds 50, and remains remarkably straight throughout its evolution. Several times during the observation bright blobs of plasma are seen to erupt upward, ascending and subsequently descending along the structure. These blobs are cotemporal with footpoint and arcade brightenings, which we believe indicates multiple episodes of reconnection at the structure base. Through imaging and spectroscopic analysis of jet and footpoint plasma we determine a number of properties, including the line-of-sight inclination, the temperature and density structure, and lift-off velocities and accelerations of jet eruptions. We use these properties to constrain the geometry of the jet structure and conditions in reconnection region.

  8. The Genomic Signature of Population Reconnection Following Isolation: From Theory to HIV

    Directory of Open Access Journals (Sweden)

    Nicolas Alcala

    2016-01-01

    Full Text Available Ease of worldwide travel provides increased opportunities for organisms not only to colonize new environments but also to encounter related but diverged populations. Such events of reconnection and secondary contact of previously isolated populations are widely observed at different time scales. For example, during the quaternary glaciation, sea water level fluctuations caused temporal isolation of populations, often to be followed by secondary contact. At shorter time scales, population isolation and reconnection of viruses are commonly observed, and such events are often associated with epidemics and pandemics. Here, using coalescent theory and simulations, we describe the temporal impact of population reconnection after isolation on nucleotide differences and the site frequency spectrum, as well as common summary statistics of DNA variation. We identify robust genomic signatures of population reconnection after isolation. We utilize our development to infer the recent evolutionary history of human immunodeficiency virus 1 (HIV-1 in Asia and South America, successfully retrieving the successive HIV subtype colonization events in these regions. Our analysis reveals that divergent HIV-1 subtype populations are currently admixing in these regions, suggesting that HIV-1 may be undergoing a process of homogenization, contrary to popular belief.

  9. Fragmenting and Reconstructing Identity: Struggles of Appalachian Women Attempting To Reconnect to Their Native American Heritage.

    Science.gov (United States)

    Trollinger, Linda Burcham

    This qualitative study drew on the stories and reflections of six Appalachian women of Native American descent to explore their experiences of reconnecting with their lost Native identity. This paper visualizes those experiences in light of the relationships between personal realities and structural influences. Historically, Native identities have…

  10. Multispacecraft observations of the electron current sheet, neighboring magnetic islands, and electron acceleration during magnetotail reconnection

    Czech Academy of Sciences Publication Activity Database

    Chen, L. J.; Bessho, N.; Lefebvre, B.; Vaith, H.; Asnes, A.; Santolík, Ondřej; Fazakerley, A.; Puhl-Quinn, P.; Bhattacharjee, A.; Khotyaintsev, Y.; Daly, P.; Torbert, R.

    2009-01-01

    Roč. 16, - (2009), 056501/1-056501/12 ISSN 1070-664X Institutional research plan: CEZ:AV0Z30420517 Keywords : magnetotail reconnection * electron current sheet * multispacecraft observations Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.475, year: 2009

  11. On the location of dayside magnetic reconnection during an interval of duskward oriented IMF

    Directory of Open Access Journals (Sweden)

    J. A. Wild

    2007-02-01

    Full Text Available We present space- and ground-based observations of the signatures of magnetic reconnection during an interval of duskward-oriented interplanetary magnetic field on 25 March 2004. In situ field and plasma measurements are drawn from the Double Star and Cluster satellites during traversals of the pre-noon sector dayside magnetopause at low and high latitudes, respectively. These reveal the typical signatures of flux transfer events (FTEs, namely bipolar perturbations in the magnetic field component normal to the local magnetopause, enhancements in the local magnetic field strength and mixing of magnetospheric and magnetosheath plasmas. Further evidence of magnetic reconnection is inferred from the ground-based signatures of pulsed ionospheric flow observed over an extended interval. In order to ascertain the location of the reconnection site responsible for the FTEs, a simple model of open flux tube motion over the surface of the magnetopause is employed. A comparison of the modelled and observed motion of open flux tubes (i.e. FTEs and plasma flow in the magnetopause boundary layer indicates that the FTEs observed at both low and high latitudes were consistence with the existence of a tilted X-line passing through the sub-solar region, as suggested by the component reconnection paradigm. While a high latitude X-line (as predicted by the anti-parallel description of reconnection may have been present, we find it unlikely that it could have been responsible for the FTEs observed in the pre-noon sector under the observed IMF conditions. Finally, we note that throughout the interval, the magnetosphere was bathed in ULF oscillations within the solar wind electric field. While no one-to-one correspondence with the pulsed reconnection rate suggested by the ground-based observation of pulsed ionospheric flow has been demonstrated, we note that similar periodicity oscillations were observed throughout the solar wind-magnetosphere-ionosphere system. These

  12. MAGNETIZATION OF CLOUD CORES AND ENVELOPES AND OTHER OBSERVATIONAL CONSEQUENCES OF RECONNECTION DIFFUSION

    International Nuclear Information System (INIS)

    Lazarian, A.; Esquivel, A.; Crutcher, R.

    2012-01-01

    Recent observational results for magnetic fields in molecular clouds reviewed by Crutcher seem to be inconsistent with the predictions of the ambipolar diffusion theory of star formation. These include the measured decrease in mass to flux ratio between envelopes and cores, the failure to detect any self-gravitating magnetically subcritical clouds, the determination of the flat probability distribution function (PDF) of the total magnetic field strengths implying that there are many clouds with very weak magnetic fields, and the observed scaling B∝ρ 2/3 that implies gravitational contraction with weak magnetic fields. We consider the problem of magnetic field evolution in turbulent molecular clouds and discuss the process of magnetic field diffusion mediated by magnetic reconnection. For this process that we termed 'reconnection diffusion', we provide a simple physical model and explain that this process is inevitable in view of the present-day understanding of MHD turbulence. We address the issue of the expected magnetization of cores and envelopes in the process of star formation and show that reconnection diffusion provides an efficient removal of magnetic flux that depends only on the properties of MHD turbulence in the core and the envelope. We show that as the amplitude of turbulence as well as the scale of turbulent motions decrease from the envelope to the core of the cloud, the diffusion of the magnetic field is faster in the envelope. As a result, the magnetic flux trapped during the collapse in the envelope is being released faster than the flux trapped in the core, resulting in much weaker fields in envelopes than in cores, as observed. We provide simple semi-analytical model calculations which support this conclusion and qualitatively agree with the observational results. Magnetic reconnection is also consistent with the lack of subcritical self-gravitating clouds, with the observed flat PDF of field strengths, and with the scaling of field strength

  13. Particle acceleration with anomalous pitch angle scattering in 2D magnetohydrodynamic reconnection simulations

    Science.gov (United States)

    Borissov, A.; Kontar, E. P.; Threlfall, J.; Neukirch, T.

    2017-09-01

    The conversion of magnetic energy into other forms (such as plasma heating, bulk plasma flows, and non-thermal particles) during solar flares is one of the outstanding open problems in solar physics. It is generally accepted that magnetic reconnection plays a crucial role in these conversion processes. In order to achieve the rapid energy release required in solar flares, an anomalous resistivity, which is orders of magnitude higher than the Spitzer resistivity, is often used in magnetohydrodynamic (MHD) simulations of reconnection in the corona. The origin of Spitzer resistivity is based on Coulomb scattering, which becomes negligible at the high energies achieved by accelerated particles. As a result, simulations of particle acceleration in reconnection events are often performed in the absence of any interaction between accelerated particles and any background plasma. This need not be the case for scattering associated with anomalous resistivity caused by turbulence within solar flares, as the higher resistivity implies an elevated scattering rate. We present results of test particle calculations, with and without pitch angle scattering, subject to fields derived from MHD simulations of two-dimensional (2D) X-point reconnection. Scattering rates proportional to the ratio of the anomalous resistivity to the local Spitzer resistivity, as well as at fixed values, are considered. Pitch angle scattering, which is independent of the anomalous resistivity, causes higher maximum energies in comparison to those obtained without scattering. Scattering rates which are dependent on the local anomalous resistivity tend to produce fewer highly energised particles due to weaker scattering in the separatrices, even though scattering in the current sheet may be stronger when compared to resistivity-independent scattering. Strong scattering also causes an increase in the number of particles exiting the computational box in the reconnection outflow region, as opposed to along the

  14. Use of Data Mining and Computer Vision Algorithms in Studies of Magnetic Reconnection

    Science.gov (United States)

    Sipes, T.; Karimabadi, H.; Gosling, J. T.; Phan, T.; Yilmaz, A.

    2011-12-01

    Knowledge discovery from large data sets collected from spacecraft measurements as well as petascale simulations remains a major obstacle to scientific progress. For example, our recent 3D kinetic simulation of reconnection included over 3 trillion particles and generated well over 200 TB of data. Similarly identification of interesting features in spacecraft data can be quite time consuming and by definition focuses on simpler features as human eye has limited capability in deciphering complex patterns and dependencies. Machine learning algorithms offer a solution to this problem. Here we present our latest results on use of machine learning algorithms in analysis of (i) 2D and 3D kinetic simulations of reconnection and (ii) reconnection events in the solar wind using Wind data. The results are quite promising and point to the power of these techniques to find hidden relationships. For example, identification of flux ropes in the solar wind remains quite controversial since unlike the magnetopause where one can search for bipolar signatures of the magnetic field component in the boundary normal coordinates, there are no generally agreed upon method of identifying them. As a preparation for this, we show results of our technique applied to time series generated from simulations of flux ropes. We find that the algorithms were not only able to detect flux ropes in the simulation data very accurately, but they were also able to distinguish crossings across a flux rope versus those along the axis of a flux rope. In case of spacecraft data, our models were able to detect crossings of the reconnection exhausts and distinguish them from non-exhausts. Finally, we use machine learning algorithms to compare the crossings of reconnection exhausts from simulations and spacecraft observations in the solar wind.

  15. Low and middle altitude cusp particle signatures for general magnetopause reconnection rate variations. 1: Theory

    Science.gov (United States)

    Lockwood, M.; Smith, M. F.

    1994-01-01

    We present predictions of the signatures of magnetosheath particle precipitation (in the regions classified as open low-latitude boundary layer, cusp, mantle and polar cap) for periods when the interplanetary magnetic field has a southward component. These are made using the 'pulsating cusp' model of the effects of time-varying magnetic reconnection at the dayside magnetopause. Predictions are made for both low-altitude satellites in the topside ionosphere and for midaltitude spacecraft in the magnetosphere. Low-altitude cusp signatures, which show a continuous ion dispersion signature, reveal 'quasi-steady reconnection' (one limit of the pulsating cusp model), which persists for a period of at least 10 min. We estimate that 'quasi-steady' in this context corresponds to fluctuations in the reconnection rate of a factor of 2 or less. The other limit of the pulsating cusp model explains the instantaneous jumps in the precipitating ion spectrum that have been observed at low altitudes. Such jumps are produced by isolated pulses of reconnection: that is, they are separated by intervals when the reconnection rate is zero. These also generate convecting patches on the magnetopause in which the field lines thread the boundary via a rotational discontinuity separated by more extensive regions of tangential discontinuity. Predictions of the corresponding ion precipitation signatures seen by midaltitude spacecraft are presented. We resolve the apparent contradiction between estimates of the width of the injection region from midaltitude data and the concept of continuous entry of solar wind plasma along open field lines. In addition, we reevaluate the use of pitch angle-energy dispersion to estimate the injection distance.

  16. GAMMA-RAY BURSTS FROM MAGNETIC RECONNECTION: VARIABILITY AND ROBUSTNESS OF LIGHT CURVES

    Energy Technology Data Exchange (ETDEWEB)

    Granot, Jonathan [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Ra’anana 4353701 (Israel)

    2016-01-10

    The dissipation mechanism that powers gamma-ray bursts (GRBs) remains uncertain almost half a century after their discovery. The two main competing mechanisms are the extensively studied internal shocks and the less studied magnetic reconnection. Here we consider GRB emission from magnetic reconnection accounting for the relativistic bulk motions that it produces in the jet's bulk rest frame. Far from the source the magnetic field is almost exactly normal to the radial direction, suggesting locally quasi-spherical thin reconnection layers between regions of oppositely directed magnetic field. We show that if the relativistic motions in the jet's frame are confined to such a quasi-spherical uniform layer, then the resulting GRB light curves are independent of their direction distribution within this layer. This renders previous results for a delta-function velocity-direction distribution applicable to a much more general class of reconnection models, which are suggested by numerical simulations. Such models that vary in their velocity-direction distribution differ mainly in the size of the bright region that contributes most of the observed flux at a given emission radius or observed time. The more sharply peaked this distribution, the smaller this bright region, and the stronger the light curve variability that may be induced by deviations from a uniform emission over the thin reconnection layer, which may be expected in a realistic GRB outflow. This is reflected both in the observed image at a given observed time and in the observer-frame emissivity map at a given emission radius, which are calculated here for three simple velocity-direction distributions.

  17. Search for Colour Reconnection Effects in $e^+ e^- \\to W^+ W^- \\to hadrons$ through Particle-Flow Studies at LEP

    CERN Document Server

    Achard, P; Aguilar-Benítez, M; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Anderhub, H; Andreev, V P; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Bajo, A; Baksay, G; Baksay, L; Baldew, S V; Banerjee, S; Banerjee, Sw; Barczyk, A; Barillère, R; Bartalini, P; Basile, M; Batalova, N; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Bellucci, L; Berbeco, R; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Biasini, M; Biglietti, M; Biland, A; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böhm, A; Boldizsar, L; Borgia, B; Bottai, S; Bourilkov, D; Bourquin, Maurice; Braccini, S; Branson, J G; Brochu, F; Burger, J D; Burger, W J; Cai, X D; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada, M; Chamizo-Llatas, M; Chang, Y H; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chiefari, G; Cifarelli, Luisa; Cindolo, F; Clare, I; Clare, R; Coignet, G; Colino, N; Costantini, S; de la Cruz, B; Cucciarelli, S; van Dalen, J A; De Asmundis, R; Déglon, P L; Debreczeni, J; Degré, A; Dehmelt, K; Deiters, K; Della Volpe, D; Delmeire, E; Denes, P; De Notaristefani, F; De Salvo, A; Diemoz, M; Dierckxsens, M; Dionisi, C; Dittmar, M; Doria, A; Dova, M T; Duchesneau, D; Duda, M; Echenard, B; Eline, A; El-Hage, A; El-Mamouni, H; Engler, A; Eppling, F J; Extermann, P; Falagán, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, M; Ferguson, T; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Fisher, W; Fisk, I; Forconi, G; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gataullin, M; Gentile, S; Giagu, S; Gong, Z F; Grenier, G; Grimm, O; Grünewald, M W; Guida, M; van Gulik, R; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Hakobyan, R S; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Hirschfelder, J; Hofer, H; Hohlmann, M; Holzner, G; Hou, S R; Hu, Y; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Käfer, D; Kaur, M; Kienzle-Focacci, M N; Kim, J K; Kirkby, Jasper; Kittel, E W; Klimentov, A; König, A C; Kopal, M; Koutsenko, V F; Kräber, M H; Krämer, R W; Krüger, A; Kunin, A; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Le Goff, J M; Leiste, R; Levtchenko, M; Levchenko, P M; Li, C; Likhoded, S; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lü, Y S; Luci, C; Luminari, L; Lustermann, W; Ma Wen Gan; Malgeri, L; Malinin, A; Maña, C; Mans, J; Martin, J P; Marzano, F; Mazumdar, K; McNeil, R R; Mele, S; Merola, L; Meschini, M; Metzger, W J; Mihul, A; Milcent, H; Mirabelli, G; Mnich, J; Mohanty, G B; Muanza, G S; Muijs, A J M; Musicar, B; Musy, M; Nagy, S; Natale, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Nisati, A; Nowak, H; Ofierzynski, R A; Organtini, G; Pal, I; Palomares, C; Paolucci, P; Paramatti, R; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Pedace, M; Pensotti, S; Perret-Gallix, D; Petersen, B; Piccolo, D; Pierella, F; Pioppi, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Pothier, J; Prokofev, D; Prokofiev, D O; Quartieri, J; Rahal-Callot, G; Rahaman, M A; Raics, P; Raja, N; Ramelli, R; Rancoita, P G; Ranieri, R; Raspereza, A V; Razis, P A; Ren, D; Rescigno, M; Reucroft, S; Riemann, S; Riles, K; Roe, B P; Romero, L; Rosca, A; Rosier-Lees, S; Roth, S; Rosenbleck, C; Rubio, J A; Ruggiero, G; Rykaczewski, H; Sakharov, A; Saremi, S; Sarkar, S; Salicio, J; Sánchez, E; Schäfer, C; Shchegelskii, V; Schopper, Herwig Franz; Schotanus, D J; Sciacca, C; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shumilov, E; Shvorob, A V; Son, D; Souga, C; Spillantini, P; Steuer, M; Stickland, D P; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Sushkov, S; Suter, H; Swain, J D; Szillási, Z; Tang, X W; Tarjan, P; Tauscher, Ludwig; Taylor, L; Tellili, B; Teyssier, D; Timmermans, C; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Tully, C; Tung, K L; Ulbricht, J; Valente, E; Van de Walle, R T; Vásquez, R; Veszpremi, V; Vesztergombi, G; Vetlitskii, I; Vicinanza, D; Viertel, Gert M; Villa, S; Vivargent, M; Vlachos, S; Vodopyanov, I; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Wadhwa, M; Wang, Q; Wang, X L; Wang, Z M; Weber, M; Wienemann, P; Wilkens, H; Wynhoff, S; Xia, L; Xu, Z Z; Yamamoto, J; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Yeh, S C; Zalite, A; Zalite, Yu; Zhang, Z P; Zhao, J; Zhu, G Y; Zhu, R Y; Zhuang, H L; Zichichi, A; Zimmermann, B; Zöller, M

    2003-01-01

    A search for colour reconnection effects in hadronic decays of W pairs is performed with the L3 detector at centre-of-mass energies between 189 and 209 GeV. The analysis is based on the study of the particle flow between jets associated to the same W boson and between two different W bosons in qqqq events. The ratio of particle yields in the different interjet regions is found to be sensitive to colour reconnection effects implemented in some hadronisation models. The data are compared to different models with and without such effects. An extreme scenario of colour reconnection is ruled out.

  18. Homologous Circular-ribbon Flares Driven by Twisted Flux Emergence

    Science.gov (United States)

    Xu, Z.; Yang, K.; Guo, Y.; Zhao, J.; Zhao, Z. J.; Kashapova, L.

    2017-12-01

    In this paper, we report two homologous circular-ribbon flares associated with two filament eruptions. They were well observed by the New Vacuum Solar Telescope and the Solar Dynamics Observatory on 2014 March 5. Prior to the flare, two small-scale filaments enclosed by a circular pre-flare brightening lie along the circular polarity inversion line around the parasitic polarity, which has shown a continuous rotation since its first appearance. Two filaments eventually erupt in sequence associated with two homologous circular-ribbon flares and display an apparent writhing signature. Supplemented by the nonlinear force-free field extrapolation and the magnetic field squashing factor investigation, the following are revealed. (1) This event involves the emergence of magnetic flux ropes into a pre-existing polarity area, which yields the formation of a 3D null-point topology in the corona. (2) Continuous input of the free energy in the form of a flux rope from beneath the photosphere may drive a breakout-type reconnection occurring high in the corona, supported by the pre-flare brightening. (3) This initiation reconnection could release the constraint on the flux rope and trigger the MHD instability to first make filament F1 lose equilibrium. The subsequent more violent magnetic reconnection with the overlying flux is driven during the filament rising. In return, the eruption of filament F2 is further facilitated by the reduction of the magnetic tension force above. These two processes form a positive feedback to each other to cause the energetic mass eruption and flare.

  19. Width dependent collisionless electron dynamics in the static fields of the shock ramp, 2, Phase space portrait

    Directory of Open Access Journals (Sweden)

    M. Gedalin

    1997-01-01

    Full Text Available We study numerically in detail the behaviour of electrons in the strongly inhomogeneous static magnetic and electric fields, which are typical for thin quasiperpendicular collisionless shocks. We pay particular attention to the dependence of the final electron velocities on their initial velocities, for different shock widths. Electrons are completely magnetized when the shock is wide, but become demagnetized, and the energies that they acquire rapidly increase with the steepening of the field structure. One of the clear manifestations of the electron demagnetization is the loss of even approximate one-to-one correspondence of the downstream perpendicular velocity to the upstream perpendicular velocity. Electron reflection occurs despite the large cross-shock potential which accelerates electrons along the magnetic field (the regime of complete magnetization or across the shock (strong demagnetization. The reflected ion fraction is sensitive to the potential, magnetic field jump, and ramp width.

  20. Growth and propagation of self-generated magnetic dipole vortices in collisionless shocks produced by interpenetrating plasmas

    Science.gov (United States)

    Naseri, N.; Bochkarev, S. G.; Ruan, P.; Bychenkov, V. Yu.; Khudik, V.; Shvets, G.

    2018-01-01

    Collisionless shocks generated by colliding relativistic plasmas are studied using particle-in-cell (PIC) simulations. The shock is produced due to the Weibel instabilities that generate current and density filaments and small-scale magnetic fields that are amplified from initial fluctuations. Localized regions of the strong magnetic field in the form of magnetic dipole vortices upstream of the shock are observed in the simulation developed during the nonlinear evolution of the electron and ion filaments. The vortices developing from the merger and subsequent pinching of the small-scale filaments are shown to be moving in the direction opposite to that of the shock. We also found an analytical estimate of the drift velocity of the vortices that are confirmed by the PIC simulations.

  1. Relativistic self-focusing of intense laser beam in thermal collisionless quantum plasma with ramped density profile

    Directory of Open Access Journals (Sweden)

    S. Zare

    2015-04-01

    Full Text Available Propagation of a Gaussian x-ray laser beam has been analyzed in collisionless thermal quantum plasma with considering a ramped density profile. In this density profile due to the increase in the plasma density, an earlier and stronger self-focusing effect is noticed where the beam width oscillates with higher frequency and less amplitude. Moreover, the effect of the density profile slope and the initial plasma density on the laser propagation has been studied. It is found that, by increasing the initial density and the ramp slope, the laser beam focuses faster with less oscillation amplitude, smaller laser spot size and more oscillations. Furthermore, a comparison is made among the laser self-focusing in thermal quantum plasma, cold quantum plasma and classical plasma. It is realized that the laser self-focusing in the quantum plasma becomes stronger in comparison with the classical regime.

  2. Reconstruction of a large-scale reconnection exhaust structure in the solar wind

    Directory of Open Access Journals (Sweden)

    W.-L. Teh

    2009-02-01

    Full Text Available We recover two-dimensional (2-D magnetic field and flow field configurations from three spacecraft encounters with a single large-scale reconnection exhaust structure in the solar wind, using a new reconstruction method (Sonnerup and Teh, 2008 based on the ideal single-fluid MHD equations in a steady-state, 2-D geometry. The reconstruction is performed in the rest frame of the X-line, where the flow into, and the plasma jetting within, the exhaust region are clearly visible. The event was first identified by Phan et al. (2006 in the ACE, Cluster, and Wind data sets; they argued that quasi-steady reconnection persisted for over 2 h at a long (390 RE X-line. The reconnection exhaust is sandwiched between two discontinuities, both of which contain elements of intermediate- and slow-mode behavior; these elements are co-located rather than being spatially separated. These composite discontinuities do not satisfy the coplanarity condition or the standard MHD jump conditions. For all three spacecraft, the Walén regression line slope was positive (negative for the leading (trailing discontinuity. Our MHD reconstruction shows that: (1 the X-line orientation was close to the bisector of the overall magnetic shear angle and exhibited a slow rotating motion toward the Sun-Earth line; (2 the X-line moved earthward, dawnward, and southward; (3 the reconnection electric field was small (~0.02 mV/m on average and gradually decreased from the first crossing (ACE to the last (Wind. The magnetic field and flow field configurations recovered from ACE and Cluster are similar while those recovered from Wind also include a magnetic island and an associated vortex. Reconnection persisted for at least 2.4 h involving inflow into the exhaust region from its two sides. Time-dependence in the reconnection electric fields seen by ACE and Wind indicates local temporal variations in the field configuration. In addition to the reconstruction results, we provide a description

  3. Reconstruction of a large-scale reconnection exhaust structure in the solar wind

    Directory of Open Access Journals (Sweden)

    W.-L. Teh

    2009-02-01

    Full Text Available We recover two-dimensional (2-D magnetic field and flow field configurations from three spacecraft encounters with a single large-scale reconnection exhaust structure in the solar wind, using a new reconstruction method (Sonnerup and Teh, 2008 based on the ideal single-fluid MHD equations in a steady-state, 2-D geometry. The reconstruction is performed in the rest frame of the X-line, where the flow into, and the plasma jetting within, the exhaust region are clearly visible. The event was first identified by Phan et al. (2006 in the ACE, Cluster, and Wind data sets; they argued that quasi-steady reconnection persisted for over 2 h at a long (390 RE X-line. The reconnection exhaust is sandwiched between two discontinuities, both of which contain elements of intermediate- and slow-mode behavior; these elements are co-located rather than being spatially separated. These composite discontinuities do not satisfy the coplanarity condition or the standard MHD jump conditions. For all three spacecraft, the Walén regression line slope was positive (negative for the leading (trailing discontinuity. Our MHD reconstruction shows that: (1 the X-line orientation was close to the bisector of the overall magnetic shear angle and exhibited a slow rotating motion toward the Sun-Earth line; (2 the X-line moved earthward, dawnward, and southward; (3 the reconnection electric field was small (~0.02 mV/m on average and gradually decreased from the first crossing (ACE to the last (Wind. The magnetic field and flow field configurations recovered from ACE and Cluster are similar while those recovered from Wind also include a magnetic island and an associated vortex. Reconnection persisted for at least 2.4 h involving inflow into the exhaust region from its two sides. Time-dependence in the reconnection electric fields seen by ACE and Wind indicates local temporal variations in the field configuration. In addition to the reconstruction results, we

  4. Strategic Floodplain Reconnection Along the Lower Tisza and Lower Illinois Rivers: Identifying Opportunities, Tradeoffs, and Limitations

    Science.gov (United States)

    Guida, R.; Remo, J. W.; Secchi, S.; Swanson, T.; Kiss, T.

    2015-12-01

    During the late 19th and into the 20th Centuries, the Tisza and Illinois Rivers were highly altered through the construction of levees and dams to reclaim their floodplain-wetland systems for agriculture and to facilitate navigation. In recent decades, flood levels have continued to rise due to aggradation on the confined floodplains reducing flood-conveyance capacity. As a result, "Room for the River" proposals have gained more prominence. Our overarching hypothesis is that strategically reconnecting these rivers to their floodplains will reduce flood levels and increase ecological habitat while limiting socioeconomic impacts. In this study, we assessed several reconnection scenarios, including levee setbacks and removals, for the Lower Tisza River (LTR; Hungary) and the Lower Illinois River (LIR; Illinois, USA). To model water-surface elevations (WSELs) for the 5- through 500-year flood events, we employed HEC-RAS (1D) and SOBEK (1D/2D) hydraulic models. To determine socioeconomic tradeoffs using these modeled WSELs, we developed a corresponding suite of expected annual damages (EADs) using FEMA's Hazus-MH flood-loss modeling software for buildings and integrated geospatial and soil productivity indices to estimate agricultural losses. To assess ecosystem benefits of reconnection along the LTR, we used historic wetland extent as a proxy for increasing needed floodplain habitats. For the LIR, we performed habitat screening using Land Capability Potential Index and other assessment tools to estimate potential ecosystem benefits. Results indicate that levee removal and/or setbacks may reduce flood heights up to 1.6 m along the LTR and over 1.0 m along the LIR. While urban areas have the highest EADs, several lower-production agricultural areas show potential for reducing flood heights while minimizing damages. Strategic-floodplain reconnection benefits along the LTR and LIR include over half of historically-significant wetlands being reconnected and the creation of

  5. CICART Center For Integrated Computation And Analysis Of Reconnection And Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Amitava [Univ. of New Hampshire, Durham, NH (United States)

    2016-03-27

    CICART is a partnership between the University of New Hampshire (UNH) and Dartmouth College. CICART addresses two important science needs of the DoE: the basic understanding of magnetic reconnection and turbulence that strongly impacts the performance of fusion plasmas, and the development of new mathematical and computational tools that enable the modeling and control of these phenomena. The principal participants of CICART constitute an interdisciplinary group, drawn from the communities of applied mathematics, astrophysics, computational physics, fluid dynamics, and fusion physics. It is a main premise of CICART that fundamental aspects of magnetic reconnection and turbulence in fusion devices, smaller-scale laboratory experiments, and space and astrophysical plasmas can be viewed from a common perspective, and that progress in understanding in any of these interconnected fields is likely to lead to progress in others. The establishment of CICART has strongly impacted the education and research mission of a new Program in Integrated Applied Mathematics in the College of Engineering and Applied Sciences at UNH by enabling the recruitment of a tenure-track faculty member, supported equally by UNH and CICART, and the establishment of an IBM-UNH Computing Alliance. The proposed areas of research in magnetic reconnection and turbulence in astrophysical, space, and laboratory plasmas include the following topics: (A) Reconnection and secondary instabilities in large high-Lundquist-number plasmas, (B) Particle acceleration in the presence of multiple magnetic islands, (C) Gyrokinetic reconnection: comparison with fluid and particle-in-cell models, (D) Imbalanced turbulence, (E) Ion heating, and (F) Turbulence in laboratory (including fusion-relevant) experiments. These theoretical studies make active use of three high-performance computer simulation codes: (1) The Magnetic Reconnection Code, based on extended two-fluid (or Hall MHD) equations, in an Adaptive Mesh

  6. CICART Center For Integrated Computation And Analysis Of Reconnection And Turbulence

    International Nuclear Information System (INIS)

    Bhattacharjee, Amitava

    2016-01-01

    CICART is a partnership between the University of New Hampshire (UNH) and Dartmouth College. CICART addresses two important science needs of the DoE: the basic understanding of magnetic reconnection and turbulence that strongly impacts the performance of fusion plasmas, and the development of new mathematical and computational tools that enable the modeling and control of these phenomena. The principal participants of CICART constitute an interdisciplinary group, drawn from the communities of applied mathematics, astrophysics, computational physics, fluid dynamics, and fusion physics. It is a main premise of CICART that fundamental aspects of magnetic reconnection and turbulence in fusion devices, smaller-scale laboratory experiments, and space and astrophysical plasmas can be viewed from a common perspective, and that progress in understanding in any of these interconnected fields is likely to lead to progress in others. The establishment of CICART has strongly impacted the education and research mission of a new Program in Integrated Applied Mathematics in the College of Engineering and Applied Sciences at UNH by enabling the recruitment of a tenure-track faculty member, supported equally by UNH and CICART, and the establishment of an IBM-UNH Computing Alliance. The proposed areas of research in magnetic reconnection and turbulence in astrophysical, space, and laboratory plasmas include the following topics: (A) Reconnection and secondary instabilities in large high-Lundquist-number plasmas, (B) Particle acceleration in the presence of multiple magnetic islands, (C) Gyrokinetic reconnection: comparison with fluid and particle-in-cell models, (D) Imbalanced turbulence, (E) Ion heating, and (F) Turbulence in laboratory (including fusion-relevant) experiments. These theoretical studies make active use of three high-performance computer simulation codes: (1) The Magnetic Reconnection Code, based on extended two-fluid (or Hall MHD) equations, in an Adaptive Mesh

  7. The Response Time of the Magnetopause Reconnection Location to Changes in the Solar Wind: MMS Case Study

    Science.gov (United States)

    Trattner, K. J.; Burch, J. L.; Ergun, R.; Fuselier, S. A.; Gomez, R. G.; Grimes, E. W.; Lewis, W. S.; Mauk, B.; Petrinec, S. M.; Pollock, C. J.

    2016-01-01

    Reconnection at the Earth's magnetopause is the mechanism by which magnetic fields in different regions change topology to create open magnetic field lines that allow energy, mass, and momentum to flow into the magnetosphere. It is the primary science goal of the recently launched MMS mission to unlock the mechanism of magnetic reconnection with a novel suite of plasma and field instruments. This study investigates several magnetopause crossings in the vicinity of the X-line on 19 September 2015 and compares the observed X-line location with predictions from the Maximum Magnetic Shear model. Rotations of the interplanetary magnetic field OMF) during the magnetopause crossings together with the close proximity of the four MMS satellites are used to determine the response time of the reconnection X-line location to changes in the IMF. The reconnection location exhibits a continuous motion during slow changes in the IMF but a delayed response to sudden changes in the IMF.

  8. Comparison of MMS data and virtual simulation data relative to secondary reconnection within a flux rope in the magnetopause

    Science.gov (United States)

    Lapenta, Giovanni; Oieroset, Marit; Phan, Tai; Eastwood, Jonathan; Goldman, Martin; Newman, David L.; Russel, Christopher; Strangeway, Robert; Paterson, William; Giles, Barbara; Lavraud, Benoit; Khotyaintsev, Yuri; Ergun, Robert; Torbert, Roy; Burch, James

    2017-04-01

    Recently Øieroset et al. [2016] reported evidence for reconnection between colliding reconnection jets in a compressed current sheet at the center of a magnetic flux rope at Earth's magnetopause. Here, we set up a simulation with parameters similar to those observed: in particular we used the same guide field ratio to the in plane field. The initial state is a Harris sheet with mass ratio 256 and temperature ratio 10. The domain is 3D with box size 20x15x10 di. Reconnection is initiated at the two edges of the box by seeding an initial localized x-line. Reconnection starts at the two x-lines by design due to the strong perturbation. The subsequent evolution shows reconnection taking root in the initially seeded x-lines. Later an instability develops within the flux rope, likely similar to those reported in Lapenta et al. [2015], and secondary reconnection starts in a ring near the center of the flux rope. The analogy with the kink mode of laboratory and solar wind flux ropes[Lapenta et al., 2006] is striking and future work will be needed to investigate if the instability satisfies the Kruskal-Shafranov limit [Shafranov, 1957, Kruskal and Tuck, 1958]. At late times, the primary reconnection site becomes inactive and the secondary reconnection site becomes dominant. In this later stage, agyrotropy and J · E' are stronger in the center. But more strikingly, the ions are outflowing predominantly away from the secondary reconnection site in the central region of the flux rope and the ring near the center where reconnection signatures (agyrotropy and J · E') are strongest. The electron pressure presents several intense loci, identifying where strong electron energization by secondary reconnection takes place. The results of the simulation are studied producing synthetic virtual satellite diagnostics obtained from the simulation results but with a format similar to in situ spacecraft observations. With these data formats the results can be more readily be compared

  9. Theory of neoclassical ion temperature-gradient-driven turbulence

    Science.gov (United States)

    Kim, Y. B.; Diamond, P. H.; Biglari, H.; Callen, J. D.

    1991-02-01

    The theory of collisionless fluid ion temperature-gradient-driven turbulence is extended to the collisional banana-plateau regime. Neoclassical ion fluid evolution equations are developed and utilized to investigate linear and nonlinear dynamics of negative compressibility ηi modes (ηi≡d ln Ti/d ln ni). In the low-frequency limit (ωB2p. As a result of these modifications, growth rates are dissipative, rather than sonic, and radial mode widths are broadened [i.e., γ˜k2∥c2s(ηi -(2)/(3) )/μi, Δx˜ρs(Bt/Bp) (1+ηi)1/2, where k∥, cs, and ρs are the parallel wave number, sound velocity, and ion gyroradius, respectively]. In the limit of weak viscous damping, enhanced neoclassical polarization persists and broadens radial mode widths. Linear mixing length estimates and renormalized turbulence theory are used to determine the ion thermal diffusivity in both cases. In both cases, a strong favorable dependence of ion thermal diffusivity on Bp (and hence plasma current) is exhibited. Furthermore, the ion thermal diffusivity for long wavelength modes exhibits favorable density scaling. The possible role of neoclassical ion temperature-gradient-driven modes in edge fluctuations and transport in L-phase discharges and the L to H transition is discussed.

  10. Oblique interaction of a laminar vortex ring with a non-deformable free surface: Vortex reconnection and breakdown

    International Nuclear Information System (INIS)

    Balakrishnan, S K; Thomas, T G; Coleman, G N

    2011-01-01

    Direct Numerical Simulation (DNS) is used to study the interaction of a laminar vortex ring with a non-deformable, free-slip surface at an oblique angle of incidence. The interaction leads to the well-known phenomenon of vortex reconnection. It was found that the reconnection process leads to rapid production of small-scale vortical structures. This phenomenon was found to be related to the kinematics of the reconection process.

  11. THE FORMATION OF AN INVERSE S-SHAPED ACTIVE-REGION FILAMENT DRIVEN BY SUNSPOT MOTION AND MAGNETIC RECONNECTION

    Energy Technology Data Exchange (ETDEWEB)

    Yan, X. L.; Xue, Z. K.; Wang, J. C.; Yang, L. H. [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Priest, E. R. [Mathematics Institute, University of St Andrews, St Andrews, KY16 9SS (United Kingdom); Guo, Q. L., E-mail: yanxl@ynao.ac.cn [College of Mathematics Physics and Information Engineering, Jiaxing University, Jiaxing 314001 (China)

    2016-11-20

    We present a detailed study of the formation of an inverse S-shaped filament prior to its eruption in active region NOAA 11884 from 2013 October 31 to November 2. In the initial stage, clockwise rotation of a small positive sunspot around the main negative trailing sunspot formed a curved filament. Then the small sunspot cancelled with the negative magnetic flux to create a longer active-region filament with an inverse S-shape. At the cancellation site a brightening was observed in UV and EUV images and bright material was transferred to the filament. Later the filament erupted after cancellation of two opposite polarities below the upper part of the filament. Nonlinear force-free field extrapolation of vector photospheric fields suggests that the filament may have a twisted structure, but this cannot be confirmed from the current observations.

  12. Colour reconnection in $e^{+}e^{-} \\rightarrow W^{+}W^{-}$ at $\\sqrt{s}=189-209 GeV$

    CERN Document Server

    Abbiendi, G.; Akesson, P.F.; Alexander, G.; Anagnostou, G.; Anderson, K.J.; Asai, S.; Axen, D.; Bailey, I.; Barberio, E.; Barillari, T.; Barlow, R.J.; Batley, R.J.; Bechtle, P.; Behnke, T.; Bell, Kenneth Watson; Bell, P.J.; Bella, G.; Bellerive, A.; Benelli, G.; Bethke, S.; Biebel, O.; Boeriu, O.; Bock, P.; Boutemeur, M.; Braibant, S.; Brown, Robert M.; Burckhart, H.J.; Campana, S.; Capiluppi, P.; Carnegie, R.K.; Carter, A.A.; Carter, J.R.; Chang, C.Y.; Charlton, D.G.; Ciocca, C.; Csilling, A.; Cuffiani, M.; Dado, S.; De Roeck, A.; De Wolf, E.A.; Desch, K.; Dienes, B.; Dubbert, J.; Duchovni, E.; Duckeck, G.; Duerdoth, I.P.; Etzion, E.; Fabbri, F.; Ferrari, P.; Fiedler, F.; Fleck, I.; Ford, M.; Frey, A.; Gagnon, P.; Gary, John William; Geich-Gimbel, C.; Giacomelli, G.; Giacomelli, P.; Giunta, Marina; Goldberg, J.; Gross, E.; Grunhaus, J.; Gruwe, M.; Gunther, P.O.; Gupta, A.; Hajdu, C.; Hamann, M.; Hanson, G.G.; Harel, A.; Hauschild, M.; Hawkes, C.M.; Hawkings, R.; Hemingway, R.J.; Herten, G.; Heuer, R.D.; Hill, J.C.; Horvath, D.; Igo-Kemenes, P.; Ishii, K.; Jeremie, H.; Jovanovic, P.; Junk, T.R.; Kanzaki, J.; Karlen, D.; Kawagoe, K.; Kawamoto, T.; Keeler, R.K.; Kellogg, R.G.; Kennedy, B.W.; Kluth, S.; Kobayashi, T.; Kobel, M.; Komamiya, S.; Kramer, T.; Krasznahorkay, A.; Krieger, P.; von Krogh, J.; Kuhl, T.; Kupper, M.; Lafferty, G.D.; Landsman, H.; Lanske, D.; Lellouch, D.; Letts, J.; Levinson, L.; Lillich, J.; Lloyd, S.L.; Loebinger, F.K.; Lu, J.; Ludwig, A.; Ludwig, J.; Mader, W.; Marcellini, S.; Martin, A.J.; Mashimo, T.; Mattig, Peter; McKenna, J.; McPherson, R.A.; Meijers, F.; Menges, W.; Merritt, F.S.; Mes, H.; Meyer, Niels T.; Michelini, A.; Mihara, S.; Mikenberg, G.; Miller, D.J.; Mohr, W.; Mori, T.; Mutter, A.; Nagai, K.; Nakamura, I.; Nanjo, H.; Neal, H.A.; Nisius, R.; O'Neale, S.W.; Oh, A.; Oreglia, M.J.; Orito, S.; Pahl, C.; Pasztor, G.; Pater, J.R.; Pilcher, J.E.; Pinfold, J.; Plane, David E.; Pooth, O.; Przybycien, M.; Quadt, A.; Rabbertz, K.; Rembser, C.; Renkel, P.; Roney, J.M.; Rossi, A.M.; Rozen, Y.; Runge, K.; Sachs, K.; Saeki, T.; Sarkisyan, E.K.G.; Schaile, A.D.; Schaile, O.; Scharff-Hansen, P.; Schieck, J.; Schorner-Sadenius, T.; Schroder, Matthias; Schumacher, M.; Seuster, R.; Shears, T.G.; Shen, B.C.; Sherwood, P.; Skuja, A.; Smith, A.M.; Sobie, R.; Soldner-Rembold, S.; Spano, F.; Stahl, A.; Strom, David M.; Strohmer, R.; Tarem, S.; Tasevsky, M.; Teuscher, R.; Thomson, M.A.; Torrence, E.; Toya, D.; Tran, P.; Trigger, I.; Trocsanyi, Z.; Tsur, E.; Turner-Watson, M.F.; Ueda, I.; Ujvari, B.; Vollmer, C.F.; Vannerem, P.; Vertesi, R.; Verzocchi, M.; Voss, H.; Vossebeld, J.; Ward, C.P.; Ward, D.R.; Watkins, P.M.; Watson, A.T.; Watson, N.K.; Wells, P.S.; Wengler, T.; Wermes, N.; Wilson, G.W.; Wilson, J.A.; Wolf, G.; Wyatt, T.R.; Yamashita, S.; Zer-Zion, D.; Zivkovic, Lidija

    2006-01-01

    The effects of the final state interaction phenomenon known as colour reconnection are investigated at centre-of-mass energies in the range $\\sqrt{s}~ 189-209 GeV using the OPAL detector at LEP. Colour reconnection is expected to affect observables based on charged particles in hadronic decays of W+W-. Measurements of inclusive charged particle multiplicities, and of their angular distribution with respect to the four jet axes of the events, are used to test models of colour reconnection. The data are found to exclude extreme scenarios of the Sjostrand-Khoze Type I (SK-I) model and are compatible with other models, both with and without colour reconnection effects. In the context of the SK-I model, the best agreement with data is obtained for a reconnection probability of 37%. Assuming no colour reconnection, the charged particle multiplicity in hadronically decaying W bosons is measured to be (nqqch) = 19.38+-0.05(stat.)+-0.08 (syst.).

  13. Observation of suprathermal electrons during magnetic reconnection at the sawtooth instability in DIII-D TOKAMAK

    CERN Document Server

    Savrukhin, R V

    2002-01-01

    OAK A271 Observation of suprathermal electrons during magnetic reconnection at the sawtooth instability in DIII-D TOKAMAK. Intense bursts of x-ray and electron cyclotron emission are observed during sawtooth instabilities in high-temperature plasmas in the DIII-D tokamak. The bursts are initiated around the X-point of the m = 1, n = 1 magnetic island at the beginning of the sawtooth crash and are displaced to larger radii later during the temperature collapse. Reconstruction of the magnetic configuration using motional Stark effect (MSE) data and numerical simulations indicates that the bursts can be connected with suprathermal electrons (E sub r approx 30-40 keV) generated during reconnection of the magnetic field around the q = 1 surface.

  14. Magnetospheric Multiscale Observations of the Electron Diffusion Region of Large Guide Field Magnetic Reconnection

    Science.gov (United States)

    Eriksson, S.; Wilder, F. D.; Ergun, R. E.; Schwartz, S. J.; Cassak, P. A.; Burch, J. L.; Chen, Li-Jen; Torbert, R. B.; Phan, T. D.; Lavraud, B.; hide

    2016-01-01

    We report observations from the Magnetospheric Multiscale (MMS) satellites of a large guide field magnetic reconnection event. The observations suggest that two of the four MMS spacecraft sampled the electron diffusion region, whereas the other two spacecraft detected the exhaust jet from the event. The guide magnetic field amplitude is approximately 4 times that of the reconnecting field. The event is accompanied by a significant parallel electric field (E(sub parallel lines) that is larger than predicted by simulations. The high-speed (approximately 300 km/s) crossing of the electron diffusion region limited the data set to one complete electron distribution inside of the electron diffusion region, which shows significant parallel heating. The data suggest that E(sub parallel lines) is balanced by a combination of electron inertia and a parallel gradient of the gyrotropic electron pressure.

  15. Magnetic Reconnection and Modification of the Hall Physics Due to Cold Ions at the Magnetopause

    Science.gov (United States)

    Andre, M.; Li, W.; Toldeo-Redondo, S.; Khotyaintsev, Yu. V.; Vaivads, A.; Graham, D. B.; Norgren, C.; Burch, J.; Lindqvist, P.-A.; Marklund, G.; hide

    2016-01-01

    Observations by the four Magnetospheric Multiscale spacecraft are used to investigate the Hall physics of a magnetopause magnetic reconnection separatrix layer. Inside this layer of currents and strong normal electric fields, cold (eV) ions of ionospheric origin can remain frozen-in together with the electrons. The cold ions reduce the Hall current. Using a generalized Ohms law, the electric field is balanced by the sum of the terms corresponding to the Hall current, the v x B drifting cold ions, and the divergence of the electron pressure tensor. A mixture of hot and cold ions is common at the subsolar magnetopause. A mixture of length scales caused by a mixture of ion temperatures has significant effects on the Hall physics of magnetic reconnection.

  16. Magnetopause reconnection rate estimates for Jupiter's magnetosphere based on interplanetary measurements at ~5AU

    Directory of Open Access Journals (Sweden)

    J. D. Nichols

    2006-03-01

    Full Text Available We make the first quantitative estimates of the magnetopause reconnection rate at Jupiter using extended in situ data sets, building on simple order of magnitude estimates made some thirty years ago by Brice and Ionannidis (1970 and Kennel and Coroniti (1975, 1977. The jovian low-latitude magnetopause (open flux production reconnection voltage is estimated using the Jackman et al. (2004 algorithm, validated at Earth, previously applied to Saturn, and here adapted to Jupiter. The high-latitude (lobe magnetopause reconnection voltage is similarly calculated using the related Gérard et al. (2005 algorithm, also previously used for Saturn. We employ data from the Ulysses spacecraft obtained during periods when it was located near 5AU and within 5° of the ecliptic plane (January to June 1992, January to August 1998, and April to October 2004, along with data from the Cassini spacecraft obtained during the Jupiter flyby in 2000/2001. We include the effect of magnetospheric compression through dynamic pressure modulation, and also examine the effect of variations in the direction of Jupiter's magnetic axis throughout the jovian day and year. The intervals of data considered represent different phases in the solar cycle, such that we are also able to examine solar cycle dependency. The overall average low-latitude reconnection voltage is estimated to be ~230 kV, such that the average amount of open flux created over one solar rotation is ~500 GWb. We thus estimate the average time to replenish Jupiter's magnetotail, which contains ~300-500 GWb of open flux, to be ~15-25 days, corresponding to a tail length of ~3.8-6.5 AU. The average high-latitude reconnection voltage is estimated to be ~130 kV, associated with lobe "stirring". Within these averages, however, the estimated voltages undergo considerable variation. Generally, the low-latitude reconnection voltage exhibits a "background" of ~100 kV that is punctuated by one or two significant

  17. 3D PIC investigation of pileup regions in the outflow of magnetic reconnection

    Science.gov (United States)

    Lapenta, Giovanni; Vapirev, A.; Markidis, S.; Goldman, M.; Newman, D.

    2013-10-01

    As the magnetic field energy, the electrons and the ions exit a reconnection region eventually they pile up against the larger scale plasma per-existent around the reconnection region. Recent work has focused on uncovering interesting processes developing there. Satellite crossings in the Earth magnetosphere have identified such regions. In the case of an Earthward propagating flow the pile up region becomes a so-called dipolarization front. The name derives from the tendency of these fronts to re-establish a more dipolar-like field closer to the Earth, when compared with the pre-existing stretched configuration of the magnetotail. We have recently conducted a fully 3D PIC study of these regions. Here we focus on new 3D diagnostics designed to identify topological features and investigate the processes of energy exchange and particle dynamics.

  18. Developer Driven and User Driven Usability Evaluations

    DEFF Research Database (Denmark)

    Bruun, Anders

    2013-01-01

    to measure performance of usability evaluation efforts. These criteria cover thoroughness, validity, reliability, downstream utility and cost effectiveness. This leads to my overall research question: Can we provide support that enables software development practitioners and users to drive usability...... evaluations, and how do they perform with respect to the quality criteria? I studied the developer driven and user driven approaches by firstly conducting literature surveys related to each of these topics followed by artificial settings research and finally by conducting research in natural settings....... The four primary findings from my studies are: 1) The developer driven approach reveals a high level of thoroughness and downstream utility. 2) The user driven approach has higher performance regarding validity 3) The level of reliability is comparable between the two approaches. 4) The user driven...

  19. Plasmoid dynamics in flare reconnection and the frequency drift of the drifting pulsating structure

    Czech Academy of Sciences Publication Activity Database

    Bárta, Miroslav; Karlický, Marian; Žemlička, R.

    2008-01-01

    Roč. 253, 1-2 (2008), s. 173-189 ISSN 0038-0938 R&D Projects: GA ČR GA205/07/1100; GA AV ČR IAA300030701 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flares * magnetic reconnection * radio bursts Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.774, year: 2008

  20. Vortex Reconnection or Breakdown Subsequent to Perpendicular Collision With A Solid Body

    Science.gov (United States)

    Young, Larry A.

    1999-01-01

    This paper analytically examines the unsteady fluid dynamics of a vortex filament subsequent to a normal collision of the vortex with a solid body. In particular, the breakdown or reconnection phenomena, post-collision, for a vortex filament is studied. The paper does not investigate the collision dynamics process itself. The derived exact solution is based upon the laminar viscous form of the Helmholtz equations.

  1. FAST MAGNETIC RECONNECTION IN THE SOLAR CHROMOSPHERE MEDIATED BY THE PLASMOID INSTABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Ni, Lei; Kliem, Bernhard; Lin, Jun [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Wu, Ning, E-mail: leini@ynao.ac.cn [School of Tourism and Geography, Yunnan Normal University, Kunming 650031 (China)

    2015-01-20

    Magnetic reconnection in the partially ionized solar chromosphere is studied in 2.5 dimensional magnetohydrodynamic simulations including radiative cooling and ambipolar diffusion. A Harris current sheet with and without a guide field is considered. Characteristic values of the parameters in the middle chromosphere imply a high magnetic Reynolds number of ∼10{sup 6}-10{sup 7} in the present simulations. Fast magnetic reconnection then develops as a consequence of the plasmoid instability without the need to invoke anomalous resistivity enhancements. Multiple levels of the instability are followed as it cascades to smaller scales, which approach the ion inertial length. The reconnection rate, normalized to the asymptotic values of magnetic field and Alfvén velocity in the inflow region, reaches values in the range ∼0.01-0.03 throughout the cascading plasmoid formation and for zero as well as for strong guide field. The outflow velocity reaches ≈40 km s{sup –1}. Slow-mode shocks extend from the X-points, heating the plasmoids up to ∼8 × 10{sup 4} K. In the case of zero guide field, the inclusion of both ambipolar diffusion and radiative cooling causes a rapid thinning of the current sheet (down to ∼30 m) and early formation of secondary islands. Both of these processes have very little effect on the plasmoid instability for a strong guide field. The reconnection rates, temperature enhancements, and upward outflow velocities from the vertical current sheet correspond well to their characteristic values in chromospheric jets.

  2. HEATING MECHANISMS IN THE LOW SOLAR ATMOSPHERE THROUGH MAGNETIC RECONNECTION IN CURRENT SHEETS

    Energy Technology Data Exchange (ETDEWEB)

    Ni, Lei; Lin, Jun [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Roussev, Ilia I. [Division of Geosciences, National Science Foundation Arlington, Virginia (United States); Schmieder, Brigitte, E-mail: leini@ynao.ac.cn [Observatoire de Paris, LESIA, Meudon (France)

    2016-12-01

    We simulate several magnetic reconnection processes in the low solar chromosphere/photosphere; the radiation cooling, heat conduction and ambipolar diffusion are all included. Our numerical results indicate that both the high temperature (≳8 × 10{sup 4} K) and low temperature (∼10{sup 4} K) magnetic reconnection events can happen in the low solar atmosphere (100–600 km above the solar surface). The plasma β controlled by plasma density and magnetic fields is one important factor to decide how much the plasma can be heated up. The low temperature event is formed in a high β magnetic reconnection process, Joule heating is the main mechanism to heat plasma and the maximum temperature increase is only several thousand Kelvin. The high temperature explosions can be generated in a low β magnetic reconnection process, slow and fast-mode shocks attached at the edges of the well developed plasmoids are the main physical mechanisms to heat the plasma from several thousand Kelvin to over 8 × 10{sup 4} K. Gravity in the low chromosphere can strongly hinder the plasmoid instability and the formation of slow-mode shocks in a vertical current sheet. Only small secondary islands are formed; these islands, however, are not as well developed as those in the horizontal current sheets. This work can be applied to understand the heating mechanism in the low solar atmosphere and could possibly be extended to explain the formation of common low temperature Ellerman bombs (∼10{sup 4} K) and the high temperature Interface Region Imaging Spectrograph (IRIS) bombs (≳8 × 10{sup 4}) in the future.

  3. Comment on Lockwood and Davis, "On the longitudinal extent of magnetopause reconnection pulses"

    Directory of Open Access Journals (Sweden)

    W. J. Heikkila

    1999-02-01

    Full Text Available Lockwood and Davis (1996 present a concise description of magnetopause reconnection pulses, with the claimed support of three types of observations: (1 flux transfer events (FTE, (2 poleward-moving auroral forms on the dayside, and (3 steps in cusp ion dispersion characteristics. However, there are a number of errors and misconceptions in the paper that make their conclusions untenable. They do not properly take account of the fact that the relevant processes operate in the presence of a plasma. They fail to notice that the source of energy (a dynamo with E · J<0 must be close to the region of dissipation (the electrical load with E · J>0 in transient phenomena, since energy (or information cannot travel faster than the group velocity of waves in the medium (here the Alfvén velocity VA. In short, Lockwood and Davis use the wrong contour in their attempt to evaluate the electromotive force (emf. This criticism goes beyond their article: a dynamo is not included in the usual definition of reconnection, only the reconnection load. Without an explicit source of energy in the assumed model, the idea of magnetic reconnection is improperly posed. Recent research has carried out a superposed epoch analysis of conditions near the dayside magnetopause and has found the dynamo and the load, both within the magnetopause current sheet. Since the magnetopause current is from dawn to dusk, the sign of E · J reflects the sign of the electric field. The electric field reverses, within the magnetopause; this can be discovered by an application of Lenz's law using the concept of erosion of the magnetopause. The net result is plasma transfer across the magnetopause to feed the low latitude boundary layer, at least partly on closed field lines, and viscous interaction as the mechanism by which solar wind plasma couples to the magnetosphere.

  4. Analysis of the gravitational coupled collisionless Boltzmann-poisson equations and numerical simulations of the formation of self-gravitating systems

    International Nuclear Information System (INIS)

    Roy, Fabrice

    2004-01-01

    We study the formation of self-gravitating systems and their properties by means of N-body simulations of gravitational collapse. First, we summarize the major analytical results concerning the collisionless Boltzmann equation and the Poisson's equation which describe the dynamics of collisionless gravitational systems. We present a study of some analytical solutions of this coupled system of equations. We then present the software used to perform the simulations. Some of this has been parallelized and implemented with the aid of MPI. For this reason we give a brief overview of it. Finally, we present the results of the numerical simulations. Analysis of these results allows us to explain some features of self-gravitating systems and the initial conditions needed to trigger the Antonov instability and the radial orbit instability. (author) [fr

  5. Observations of Supra-arcade Fans: Instabilities at the Head of Reconnection Jets

    Science.gov (United States)

    Innes, D. E.; Guo, L.-J.; Bhattacharjee, A.; Huang, Y.-M.; Schmit, D.

    2014-11-01

    Supra-arcade fans are bright, irregular regions of emission that develop during eruptive flares above flare arcades. The underlying flare arcades are thought to be a consequence of magnetic reconnection along a current sheet in the corona. At the same time, theory predicts plasma jets from the reconnection sites which are extremely difficult to observe directly because of their low densities. It has been suggested that the dark supra-arcade downflows (SADs) seen falling through supra-arcade fans may be low-density jet plasma. The head of a low-density jet directed toward higher-density plasma would be Rayleigh-Taylor unstable, and lead to the development of rapidly growing low- and high-density fingers along the interface. Using Solar Dynamics Observatory/Atmospheric Imaging Assembly 131 Å images, we show details of SADs seen from three different orientations with respect to the flare arcade and current sheet, and highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with three-dimensional magnetohydrodynamic simulations suggests that SADs are the result of secondary instabilities of the Rayleigh-Taylor type in the exhaust of reconnection jets.

  6. Observations of supra-arcade fans: instabilities at the head of reconnection jets

    International Nuclear Information System (INIS)

    Innes, D. E.; Guo, L.-J.; Schmit, D.; Bhattacharjee, A.; Huang, Y.-M.

    2014-01-01

    Supra-arcade fans are bright, irregular regions of emission that develop during eruptive flares above flare arcades. The underlying flare arcades are thought to be a consequence of magnetic reconnection along a current sheet in the corona. At the same time, theory predicts plasma jets from the reconnection sites which are extremely difficult to observe directly because of their low densities. It has been suggested that the dark supra-arcade downflows (SADs) seen falling through supra-arcade fans may be low-density jet plasma. The head of a low-density jet directed toward higher-density plasma would be Rayleigh-Taylor unstable, and lead to the development of rapidly growing low- and high-density fingers along the interface. Using Solar Dynamics Observatory/Atmospheric Imaging Assembly 131 Å images, we show details of SADs seen from three different orientations with respect to the flare arcade and current sheet, and highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with three-dimensional magnetohydrodynamic simulations suggests that SADs are the result of secondary instabilities of the Rayleigh-Taylor type in the exhaust of reconnection jets.

  7. Evaluation of Geese Theatre's Re-Connect program: addressing resettlement issues in prison.

    Science.gov (United States)

    Harkins, Leigh; Pritchard, Cecilia; Haskayne, Donna; Watson, Andy; Beech, Anthony R

    2011-06-01

    This study examined the impact of Geese Theatre's Re-Connect program on a sample of offenders who attended it. This program used theatre performance, experiential exercises, skills practice role-plays, and metaphors such as the masks to invite a group of offenders to consider and explore issues connected with their release and reconnecting with a life outside prison. Pre- and postprogram psychometric tests, behavior ratings, and interviews were completed to assess the effectiveness of the program. Significant changes were observed from pre- to posttreatment in terms of self-efficacy, motivation to change, and improved confidence in skills (i.e., social and friendship, occupational, family and intimacy, dealing with authority, alternatives to aggression or offending, and self-management and self-control skills). Improved behavior and engagement within the program was observed over the 3 days of the program. Interviews also revealed the positive impact the program had on the participants. This provides evidence supporting the short-term effectiveness of the Re-Connect program.

  8. 3D Reconnection and SEP Considerations in the CME-Flare Problem

    Science.gov (United States)

    Moschou, S. P.; Cohen, O.; Drake, J. J.; Sokolov, I.; Borovikov, D.; Alvarado Gomez, J. D.; Garraffo, C.

    2017-12-01

    Reconnection is known to play a major role in particle acceleration in both solar and astrophysical regimes, yet little is known about its connection with the global scales and its comparative contribution in the generation of SEPs with respect to other acceleration mechanisms, such as the shock at a fast CME front, in the presence of a global structure such as a CME. Coupling efforts, combining both particle and global scales, are necessary to answer questions about the fundamentals of the energetic processes evolved. We present such a coupling modeling effort that looks into particle acceleration through reconnection in a self-consistent CME-flare model in both particle and fluid regimes. Of special interest is the supra-thermal component of the acceleration due to the reconnection that will at a later time interact colliding with the solar atmospheric material of the more dense chromospheric layer and radiate in hard X- and γ-rays for super-thermal electrons and protons respectively. Two cutting edge computational codes are used to capture the global CME and flare dynamics, specifically a two fluid MHD code and a 3D PIC code for the flare scales. Finally, we are connecting the simulations with current observations in different wavelengths in an effort to shed light to the unified CME-flare picture.

  9. Kinetic Evidence of Magnetic Reconnection Due to Kelvin-Helmholtz Waves

    Science.gov (United States)

    Li, W.; Andre, M.; Khotainstev, Yu. V.; Vaivads, A.; Graham, D. B.; Toledo-Redondo, S.; Norgren, C.; Henri, P.; Wang, C.; Tang, B. B.; hide

    2016-01-01

    The Kelvin-Helmholtz (ICH) instability at the Earth's magnetopause is predominantly excited during northward interplanetary magnetic field (IMF). Magnetic reconnection due to KH waves has been suggested as one of the mechanisms to transfer solar wind plasma into the magnetosphere. We investigate KH waves observed at the magnetopause by the Magnetospheric Multlscale (MMS) mission; in particular, we study the trailing edges of KH waves with Alfvenic ion jets. We observe gradual mixing of magnetospheric and magnetosheath ions at the boundary layer. The magnetospheric electrons with energy up to 80 keV are observed on the magnetosheath side of the jets, which indicates that they escape into the magnetosheath through reconnected magnetic field lines. At the same time, the low-energy (below 100eV) magnetosheath electrons enter the magnetosphere and are heated in the field-aligned direction at the high-density edge of the jets. Our observations provide unambiguous kinetic evidence for ongoing reconnection due to KH waves.

  10. Magnetic Reconnection May Control the Ion-scale Spectral Break of Solar Wind Turbulence

    Science.gov (United States)

    Vech, Daniel; Mallet, Alfred; Klein, Kristopher G.; Kasper, Justin C.

    2018-03-01

    The power spectral density of magnetic fluctuations in the solar wind exhibits several power-law-like frequency ranges with a well-defined break between approximately 0.1 and 1 Hz in the spacecraft frame. The exact dependence of this break scale on solar wind parameters has been extensively studied but is not yet fully understood. Recent studies have suggested that reconnection may induce a break in the spectrum at a “disruption scale” {λ }{{D}}, which may be larger than the fundamental ion kinetic scales, producing an unusually steep spectrum just below the break. We present a statistical investigation of the dependence of the break scale on the proton gyroradius ρ i , ion inertial length d i , ion sound radius ρ s , proton–cyclotron resonance scale ρ c , and disruption scale {λ }{{D}} as a function of {β }\\perp i. We find that the steepest spectral indices of the dissipation range occur when β e is in the range of 0.1–1 and the break scale is only slightly larger than the ion sound scale (a situation occurring 41% of the time at 1 au), in qualitative agreement with the reconnection model. In this range, the break scale shows a remarkably good correlation with {λ }{{D}}. Our findings suggest that, at least at low β e , reconnection may play an important role in the development of the dissipation range turbulent cascade and cause unusually steep (steeper than ‑3) spectral indices.

  11. Statistical Properties of Ribbon Evolution and Reconnection Electric Fields in Eruptive and Confined Flares

    Science.gov (United States)

    Hinterreiter, J.; Veronig, A. M.; Thalmann, J. K.; Tschernitz, J.; Pötzi, W.

    2018-03-01

    A statistical study of the chromospheric ribbon evolution in Hα two-ribbon flares was performed. The data set consists of 50 confined (62%) and eruptive (38%) flares that occurred from June 2000 to June 2015. The flares were selected homogeneously over the Hα and Geostationary Operational Environmental Satellite (GOES) classes, with an emphasis on including powerful confined flares and weak eruptive flares. Hα filtergrams from the Kanzelhöhe Observatory in combination with Michelson Doppler Imager (MDI) and Helioseismic and Magnetic Imager (HMI) magnetograms were used to derive the ribbon separation, the ribbon-separation velocity, the magnetic-field strength, and the reconnection electric field. We find that eruptive flares reveal statistically larger ribbon separation and higher ribbon-separation velocities than confined flares. In addition, the ribbon separation of eruptive flares correlates with the GOES SXR flux, whereas no clear dependence was found for confined flares. The maximum ribbon-separation velocity is not correlated with the GOES flux, but eruptive flares reveal on average a higher ribbon-separation velocity (by ≈ 10 km s-1). The local reconnection electric field of confined (cc=0.50 ±0.02) and eruptive (cc=0.77 ±0.03) flares correlates with the GOES flux, indicating that more powerful flares involve stronger reconnection electric fields. In addition, eruptive flares with higher electric-field strengths tend to be accompanied by faster coronal mass ejections.

  12. Investigation of Colour Reconnection in WW Events with the DELPHI detector at LEP-2

    CERN Document Server

    Abdallah, J; Adam, W; Adzic, P; Albrecht, T; Alemany-Fernandez, R; Allmendinger, T; Allport, P P; Amaldi, Ugo; Amapane, N; Amato, S; Anashkin, E; Andreazza, A; Andringa, S; Anjos, N; Antilogus, P; Apel, W D; Arnoud, Y; Ask, S; Åsman, B; Augustin, J E; Augustinus, A; Baillon, P; Ballestrero, A; Bambade, P; Barbier, R; Bardin, D; Barker, G J; Baroncelli, A; Battaglia, M; Baubillier, M; Becks, K H; Begalli, M; Behrmann, A; Ben-Haim, E; Benekos, N; Benvenuti, A; Bérat, C; Berggren, M; Berntzon, L; Bertrand, D; Besancon41, M; Besson, N; Bloch, D; Blom, M; Bluj, M; Bonesini, M; Boonekamp, M; Booth, P S L; Borisov, G; Botner, O; Bouquet, B; Bowcock, T J V; Boyko, I; Bracko, M; Brenner, R; Brodet, E; Brückman, P; Brunet8, J M; Buschbeck55, B; Buschmann, P; Calvi, M; Camporesi, T; Canale, V; Carena, F; Castro, N; Cavallo, F; Chapkin, M; Charpentier, P; Checchia, P; Chierici, R; Shlyapnikov, P; Chudoba, J; Chung, S U; Cieslik, K; Collins, P; Contri, R; Cosme, G; Cossutti, F; Costa, M J; Crennell, D J; Cuevas-Maestro, J; D'Hondt, J; Dalmau, J; Da Silva, T; Da Silva, W; Della Ricca, G; De Angelis, A; de Boer, Wim; De Clercq, C; De Lotto, B; De Maria, N; De Min, A; De Paula, L; Di Ciaccio, L; Di Simone, A; Doroba, K; Drees, J; Eigen, G; Ekelöf, T J C; Ellert, M; Elsing, M; Espirito-Santo, M C; Fanourakis, G K; Fassouliotis, D; Feindt, M; Fernández, J; Ferrer, A; Ferro, F; Flagmeyer, U; Föth, H; Fokitis, E; Fulda-Quenzer, F; Fuster, J; Gandelman, M; García, C; Gavillet, P; Gazis, E; Gokieli, R; Golob, B; Gómez-Ceballos, G; Gonçalves, P; Graziani, E; Grosdidier, G; Grzelak, K; Guy, J; Haag, C; Hallgren, A; Hamacher, K; Hamilton, K; Haug, S; Hauler, F; Hedberg, V; Hennecke, M; Herr, H; Hoffman, J; Holmgren, S O; Holt, P J; Houlden, M A; Jackson, J N; Jarlskog, G; Jarry, P; Jeans, D; Johansson, E K; Johansson, P D; Jonsson, P; Joram, C; Jungermann, L; Kapusta, F; Katsanevas, S; Katsoufis, E; Kernel, G; Kersevan, B P; Kerzel, U; King, B T; Kjaer, N J; Kluit, P; Kokkinias, P; Kourkoumelis, C; Kuznetsov, O; Krumshtein, Z; Kucharczyk, M; Lamsa, J; Leder, G; Ledroit, F; Leinonen, L; Leitner, R; Lemonne, J; Lepeltier, V; Lesiak, T; Liebig, W; Liko, D; Lipniacka, A; Lopes, J H; López, J M; Loukas, D; Lutz, P; Lyons, L; MacNaughton, J; Malek, A; Maltezos, S; Mandl, F; Marco, J; Marco, R; Maréchal, B; Margoni, M; Marin, J C; Mariotti, C; Markou, A; Martínez-Rivero, C; Masik, J; Mastroyiannopoulos, N; Matorras, F; Matteuzzi, C; Mazzucato, F; Mazzucato, M; McNulty, R; Meroni, C; Migliore, E; Mitaroff, W A; Mjörnmark, U; Moa, T; Moch, R; Mönig, K; Monge, R; Montenegro, J; Moraes, D; Moreno, S; Morettini, P; Müller, U; Münich, K; Mulders, M; Mundim, L; Murray, W; Muryn, B; Myatt, G; Myklebust, T; Nassiakou, M; Navarria, F; Nawrocki, K; Nicolaidou, R; Nikolenko, M; Oblakowska-Mucha, A; Obraztsov, V F; Olshevskii, A G; Onofre, A; Orava, R; Österberg, K; Ouraou, A; Oyanguren, A; Paganoni, M; Paiano, S; Palacios, J P; Palka, H; Papadopoulou, T D; Pape, L; Parkes, C; Parodi, F; Parzefall, U; Passeri, A; Passon, O; Peralta, L; Perepelitsa, V; Perrotta, A; Petrolini, A; Piedra, J; Pieri, L; Pierre, F; Pimenta, M; Piotto, E; Podobnik, T; Poireau, V; Pol, M E; Polok, G; Pozdnyakov, V; Pukhaeva, N; Pullia, A; Rames, J; Read, A; Rebecchi, P; Rehn, J; Reid, D; Reinhardt, R; Renton, P B; Richard, F; Rídky, J; Rivero, M; Rodríguez, D; Romero, A; Ronchese, P; Roudeau, P; Rovelli, T; Ruhlmann-Kleider, V; Ryabtchikov, D; Sadovskii, A; Salmi, L; Salt, J; Sander, C; Savoy-Navarro, A; Schwickerath, U; Sekulin, R; Siebel, M; Sisakian, A; Smadja, G; Smirnova, O; Sokolov, A; Sopczak, A; Sosnowski, R; Spassoff, Tz; Stanitzki, M; Stocchi, A; Strauss, J; Stugu, B; Szczekowski, M; Szeptycka, M; Szumlak, T; Tabarelli de Fatis, T; Taffard, A C; Tegenfeldt, F; Timmermans, J; Tkatchev, L; Tobin, M; Todorovova, S; Tomé, B; Tonazzo, A; Tortosa, P; Travnicek, P; Treille, D; Tristram, G; Trochimczuk, M; Troncon, C; Turluer, M L; Tyapkin, I A; Tyapkin, P; Tzamarias, S; Uvarov, V; Valenti, G; van Dam, P; Van Eldik, J; Van Remortel, N; Van Vulpen, I; Vegni, G; Veloso, F; Venus, W; Verdier, P; Verzi, V; Vilanova, D; Vitale, L; Vrba, V; Wahlen, H; Washbrook, A J; Weiser, C; Wicke, D; Wickens, J; Wilkinson, G; Winter, M; Witek, M; Yushchenko, O; Zalewska-Bak, A; Zalewski, P; Zavrtanik, D; Zhuravlov, V; Zimin, N; Zintchenko, A; Zupan, M

    2007-01-01

    In the reaction e+e- -> WW -> (q_1 qbar_2)(q_3 qbar_4) the usual hadronization models treat the colour singlets q_1 qbar_2 and q_3 qbar_4 coming from two W bosons independently. However, since the final state partons may coexist in space and time, cross-talk between the two evolving hadronic systems may be possible during fragmentation through soft gluon exchange. This effect is known as Colour Reconnection. In this article the results of the investigation of Colour Reconnection effects in fully hadronic decays of W pairs in DELPHI at LEP are presented. Two complementary analyses were performed, studying the particle flow between jets and W mass estimators, with negligible correlation between them, and the results were combined and compared to models. In the framework of the SK-I model, the value for its kappa parameter most compatible with the data was found to be: kappa_{SK-I} = 2.2^{+2.5}_{-1.3} corresponding to the probability of reconnection P_{reco} to be in the range 0.31 < P_{reco} < 0.68 at 68%...

  13. Observational Evidence of Magnetic Reconnection for Brightenings and Transition Region Arcades in IRIS Observations

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jie; Li, Hui; Feng, Li [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, CAS, Nanjing 210008 (China); Schmieder, Brigitte; Pariat, Etienne [LESIA, Observatoire de Paris, Section de Meudon, F-92195, Meudon Principal Cedex (France); Zhu, Xiaoshuai [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Grubecka, Michalina, E-mail: nj.lihui@pmo.ac.cn [Astronomical Institute, University of Wrocław, Kopernika 11, 51-622, Wrocław (Poland)

    2017-02-10

    By using a new method of forced-field extrapolation, we study the emerging flux region AR11850 observed by the Interface Region Imaging Spectrograph and Solar Dynamical Observatory . Our results suggest that the bright points (BPs) in this emerging region exhibit responses in lines formed from the upper photosphere to the transition region, which have relatively similar morphologies. They have an oscillation of several minutes according to the Atmospheric Imaging Assembly data at 1600 and 1700 Å. The ratio between the BP intensities measured in 1600 and 1700 Å filtergrams reveals that these BPs are heated differently. Our analysis of the Helioseismic and Magnetic Imager vector magnetic field and the corresponding topology in AR11850 indicates that the BPs are located at the polarity inversion line and most of them are related to magnetic reconnection or cancelation. The heating of the BPs might be different due to different magnetic topology. We find that the heating due to the magnetic cancelation would be stronger than the case of bald patch reconnection. The plasma density rather than the magnetic field strength could play a dominant role in this process. Based on physical conditions in the lower atmosphere, our forced-field extrapolation shows consistent results between the bright arcades visible in slit-jaw image 1400 Å and the extrapolated field lines that pass through the bald patches. It provides reliable observational evidence for testing the mechanism of magnetic reconnection for the BPs and arcades in the emerging flux region, as proposed in simulation studies.

  14. The Vehicle Integrated Performance Analysis Experience: Reconnecting With Technical Integration

    Science.gov (United States)

    McGhee, D. S.

    2006-01-01

    Very early in the Space Launch Initiative program, a small team of engineers at MSFC proposed a process for performing system-level assessments of a launch vehicle. Aimed primarily at providing insight and making NASA a smart buyer, the Vehicle Integrated Performance Analysis (VIPA) team was created. The difference between the VIPA effort and previous integration attempts is that VIPA a process using experienced people from various disciplines, which focuses them on a technically integrated assessment. The foundations of VIPA s process are described. The VIPA team also recognized the need to target early detailed analysis toward identifying significant systems issues. This process is driven by the T-model for technical integration. VIPA s approach to performing system-level technical integration is discussed in detail. The VIPA process significantly enhances the development and monitoring of realizable project requirements. VIPA s assessment validates the concept s stated performance, identifies significant issues either with the concept or the requirements, and then reintegrates these issues to determine impacts. This process is discussed along with a description of how it may be integrated into a program s insight and review process. The VIPA process has gained favor with both engineering and project organizations for being responsive and insightful

  15. Formation and Initiation of Erupting Flux Rope and Embedded Filament Driven by Photospheric Converging Motion

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Xiaozhou; Gan, Weiqun [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, 210008 Nanjing (China); Xia, Chun; Keppens, Rony, E-mail: zhaoxz@pmo.ac.cn, E-mail: wqgan@pmo.ac.cn, E-mail: chun.xia@kuleuven.be, E-mail: rony.keppens@kuleuven.be [Centre for mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium)

    2017-06-01

    In this paper, we study how a flux rope (FR) is formed and evolves into the corresponding structure of a coronal mass ejection (CME) numerically driven by photospheric converging motion. A two-and-a-half-dimensional magnetohydrodynamics simulation is conducted in a chromosphere-transition-corona setup. The initial arcade-like linear force-free magnetic field is driven by an imposed slow motion converging toward the magnetic inversion line at the bottom boundary. The convergence brings opposite-polarity magnetic flux to the polarity inversion, giving rise to the formation of an FR by magnetic reconnection and eventually to the eruption of a CME. During the FR formation, an embedded prominence gets formed by the levitation of chromospheric material. We confirm that the converging flow is a potential mechanism for the formation of FRs and a possible triggering mechanism for CMEs. We investigate the thermal, dynamical, and magnetic properties of the FR and its embedded prominence by tracking their thermal evolution, analyzing their force balance, and measuring their kinematic quantities. The phase transition from the initiation phase to the acceleration phase of the kinematic evolution of the FR was observed in our simulation. The FR undergoes a series of quasi-static equilibrium states in the initiation phase; while in the acceleration phase the FR is driven by Lorentz force and the impulsive acceleration occurs. The underlying physical reason for the phase transition is the change of the reconnection mechanism from the Sweet–Parker to the unsteady bursty regime of reconnection in the evolving current sheet underneath the FR.

  16. ENERGY RELEASE AND TRANSFER IN SOLAR FLARES: SIMULATIONS OF THREE-DIMENSIONAL RECONNECTION

    International Nuclear Information System (INIS)

    Birn, J.; Fletcher, L.; Hesse, M.; Neukirch, T.

    2009-01-01

    Using three-dimensional magnetohydrodynamic simulations we investigate energy release and transfer in a three-dimensional extension of the standard two-ribbon flare picture. In this scenario, reconnection is initiated in a thin current sheet (suggested to form below a departing coronal mass ejection) above a bipolar magnetic field. Two cases are contrasted: an initially force-free current sheet (low beta) and a finite-pressure current sheet (high beta), where beta represents the ratio between gas (plasma) and magnetic pressure. The energy conversion process from reconnection consists of incoming Poynting flux turned into up- and downgoing Poynting flux, enthalpy flux, and bulk kinetic energy flux. In the low-beta case, the outgoing Poynting flux is the dominant contribution, whereas the outgoing enthalpy flux dominates in the high-beta case. The bulk kinetic energy flux is only a minor contribution in the downward direction. The dominance of the downgoing Poynting flux in the low-beta case is consistent with an alternative to the thick target electron beam model for solar flare energy transport, suggested recently by Fletcher and Hudson, whereas the enthalpy flux may act as an alternative transport mechanism. For plausible characteristic parameters of the reconnecting field configuration, we obtain energy release timescales and energy output rates that compare favorably with those inferred from observations for the impulsive phase of flares. Significant enthalpy flux and heating are found even in the initially force-free case with very small background beta, resulting mostly from adiabatic compression rather than Ohmic dissipation. The energy conversion mechanism is most easily understood as a two-step process (although the two steps may occur essentially simultaneously): the first step is the acceleration of the plasma by Lorentz forces in layers akin to the slow shocks in the Petschek reconnection model, involving the conversion of magnetic energy to bulk kinetic

  17. Ion acceleration in electrostatic collisionless shock: on the optimal density profile for quasi-monoenergetic beams

    Science.gov (United States)

    Boella, E.; Fiúza, F.; Stockem Novo, A.; Fonseca, R.; Silva, L. O.

    2018-03-01

    A numerical study on ion acceleration in electrostatic shock waves is presented, with the aim of determining the best plasma configuration to achieve quasi-monoenergetic ion beams in laser-driven systems. It was recently shown that tailored near-critical density plasmas characterized by a long-scale decreasing rear density profile lead to beams with low energy spread (Fiúza et al 2012 Phys. Rev. Lett. 109 215001). In this work, a detailed parameter scan investigating different plasma scale lengths is carried out. As result, the optimal plasma spatial scale length that allows for minimizing the energy spread while ensuring a significant reflection of ions by the shock is identified. Furthermore, a new configuration where the required profile has been obtained by coupling micro layers of different densities is proposed. Results show that this new engineered approach is a valid alternative, guaranteeing a low energy spread with a higher level of controllability.

  18. The Role of Self-Organized Criticality in the Substorm Phenomenon and its Relation to Localized Reconnection in the Magnetospheric Plasma Sheet

    Science.gov (United States)

    Klimas, Alex J.; Valdivia, J. A.; Vassiliadis, D.; Baker, D. N.; Hesse, M.; Takalo, J.

    1999-01-01

    Evidence is presented that suggests there is a significant self-organized criticality (SOC) component in the dynamics of substorms in the magnetosphere. Observations of BBFs, fast flows, localized dipolarizations, plasma turbulence, etc. are taken to show that multiple localized reconnection sites provide the basic avalanche phenomenon in the establishment of SOC in the plasma sheet. First results are presented from a continuing plasma physical study of this avalanche process. A one-dimensional resistive MHD model of a magnetic field reversal is discussed. Resistivity, in this model, is self-consistently generated in response to the excitation of an idealized current-driven instability. When forced by convection of magnetic flux into the field reversal region, the model yields rapid magnetic field annihilation through a dynamic behavior that is shown to exhibit many of the characteristics of SOC. Over a large range of forcing strengths, the annihilation rate is sh