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Sample records for reconnection takes place

  1. Asymmetric magnetic reconnection with a flow shear and applications to the magnetopause

    CERN Document Server

    Doss, C E; Cassak, P A; Wilder, F D; Eriksson, S; Drake, J F

    2015-01-01

    We perform a theoretical and numerical study of anti-parallel 2D magnetic reconnection with asymmetries in the density and reconnecting magnetic field strength in addition to a bulk flow shear across the reconnection site in the plane of the reconnecting fields, which commonly occurs at planetary magnetospheres. We predict the speed at which an isolated X-line is convected by the flow, the reconnection rate, and the critical flow speed at which reconnection no longer takes place for arbitrary reconnecting magnetic field strengths, densities, and upstream flow speeds, and confirm the results with two-fluid numerical simulations. The predictions and simulation results counter the prevailing model of reconnection at Earth's dayside magnetopause which says reconnection occurs with a stationary X-line for sub-Alfvenic magnetosheath flow, reconnection occurs but the X-line convects for magnetosheath flows between the Alfven speed and double the Alfven speed, and reconnection does not occur for magnetosheath flows g...

  2. Collisionless Magnetic Reconnection in Space Plasmas

    CERN Document Server

    Treumann, R A

    2014-01-01

    Magnetic reconnection requires the violation of the frozen-in condition which ties gyrating charged particles to the magnetic field inhibiting diffusion. Ongoing reconnection has been identified in near-Earth space as being responsible for the excitation of substorms, magnetic storms, generation of field aligned currents and their consequences, the wealth of auroral phenomena. Its theoretical understanding is now on the verge of being completed. Reconnection takes place in thin current sheets. Analytical concepts proceeded gradually down to the microscopic scale, the scale of the electron skin depth or inertial length, recognizing that current layers that thin do preferentially undergo spontaneous reconnection. Thick current layers start reconnecting when being forced by plasma inflow to thin. For almost half a century the physical mechanism of reconnection has remained a mystery. Spacecraft in situ observations in combination with sophisticated numerical simulations in two and three dimensions recently clari...

  3. Third Place Learning Environments: Perspective Sharing and Perspective Taking

    Directory of Open Access Journals (Sweden)

    Mara Alagic

    2009-11-01

    Full Text Available In this paper we deliberate on intercultural and global communication strategies of perspective sharing and perspective taking, and potential perspective transformation. Consideration to these strategies is given within the two instances of third place learning environments: (a Role-play simulation environment in which learners develop experiment with strategies for resolving intercultural misconceptions, and (b a professional virtual learning network that may provide just-in-time support for its members encountering disorienting dilemma. The central purpose of the second environment is actually development of knowledge basis for understanding of Third Place Learning.

  4. Reconnection by turbulence

    Science.gov (United States)

    BELMONT, G.; REZEAU, L.

    2001-12-01

    Transfers of mass and magnetic flux are known to take place through the magnetopause boundary. When looking for the cause of these transfers, several scenarios have been invoked in the literature: 1) quasi-stationary reconnection; 2) localized reconnection (FTEs) 3) growing reconnection due to a local instability (tearing); 4) impulsive penetration of a magnetosheath inhomogeneity. As the very existence of the transfers implies that the frozen-in condition must be broken at some place, all of the preceding scenarios can be termed "reconnection" scenarios. The larger difference between them is that the two first scenarios pre-suppose the existence of an external electrostatic field; while the two others make use of a self-consistent inductive electric field. The varying magnetic field giving rise to the inductive electric field is due the growth of the tearing mode in the third case, while it is due to the spatial gradients limiting the incident blob in the fourth one. We will present a new scenario, of the fourth type, where the original cause for reconnection is the existence of a magnetic turbulence convecting from the shock region and impinging the magnetopause. We first show that this turbulence is converted onto the Alfven mode in the boundary gradient, where it is trapped and amplified. We also show how it can allow for transfers through the boundary, for both the magnetic flux and the plasma. A non ideal effect is of course mandatory for allowing such transfers: our model is calculated in the frame of Hall MHD, which means that the ion inertia effects are taken into account in the Ohm's law; the finite Larmor radius effects, nevertheless, have not yet been included up to now. Finally, we show that the magnetic flux reconnected per second through a perpendicular elementary surface can be calculated as a function of the local parameters; we are thus able to propose the definition of a local "reconnection rate". Analyzing the numerical results corresponding to

  5. Collisionless Magnetic Reconnection in Space Plasmas

    Directory of Open Access Journals (Sweden)

    Rudolf A. Treumann

    2013-12-01

    Full Text Available Magnetic reconnection, the merging of oppositely directed magnetic fields that leads to field reconfiguration, plasma heating, jetting and acceleration, is one of the most celebrated processes in collisionless plasmas. It requires the violation of the frozen-in condition which ties gyrating charged particles to the magnetic field inhibiting diffusion. Ongoing reconnection has been identified in near-Earth space as being responsible for the excitation of substorms, magnetic storms, generation of field aligned currents and their consequences, the wealth of auroral phenomena. Its theoretical understanding is now on the verge of being completed. Reconnection takes place in thin current sheets. Analytical concepts proceeded gradually down to the microscopic scale, the scale of the electron skin depth or inertial length, recognizing that current layers that thin do preferentially undergo spontaneous reconnection. Thick current layers start reconnecting when being forced by plasma inflow to thin. For almost half a century the physical mechanism of reconnection has remained a mystery. Spacecraft in situ observations in combination with sophisticated numerical simulations in two and three dimensions recently clarified the mist, finding that reconnection produces a specific structure of the current layer inside the electron inertial (also called electron diffusion region around the reconnection site, the X line. Onset of reconnection is attributed to pseudo-viscous contributions of the electron pressure tensor aided by electron inertia and drag, creating a complicated structured electron current sheet, electric fields, and an electron exhaust extended along the current layer. We review the general background theory and recent developments in numerical simulation on collisionless reconnection. It is impossible to cover the entire field of reconnection in a short space-limited review. The presentation necessarily remains cursory, determined by our taste

  6. "I'm stronger than I thought": Native women reconnecting to body, health, and place.

    Science.gov (United States)

    Schultz, Katie; Walters, Karina L; Beltran, Ramona; Stroud, Sandy; Johnson-Jennings, Michelle

    2016-07-01

    This community-based research applied principles of wilderness experience programming and Indigenous knowledges in an exploratory intervention designed to address health disparities in a tribal community. Drawing on historical trauma frameworks, tribal members rewalked the Trail of Tears to consider its effect on contemporary tribal health. Qualitative data from tribal members suggest that engagement with place and experiential learning, particularly the physical and emotional challenge of the Trail, facilitated changes in health beliefs, attitudes, and behaviors. Deep engagement outside of traditional health service settings should be considered in interventions and may be particularly effective in promoting positive health behaviors in Native communities. PMID:27164432

  7. Start-Time of Magnetic Reconnection in Interplanetary Space

    Institute of Scientific and Technical Information of China (English)

    范全林; 魏奉思; 冯学尚

    2003-01-01

    Start-time of magnetic reconnection under typical interplanetary parameters has been numerically simulated by using the two-dimensional compressible magnetohydrodynamic equations with a third-order compact upwind scheme. Magnetic reconnection would occur near the interplanetary current sheet impacted by a plasmoid.Its initiation is associated with the interplanetary plasma parameter β and the momentum of the plasmoid.The higher the β value is, the faster the reconnection takes place. Meanwhile the reconnection occurs earlier with increasing the plasmoid momentum, and increasing driving velocity is more effective in initializing the reconnection than that of the plasma density when the other factors are kept to be the same. The evolution of the reconnection with the heliocentric distance is also investigated.

  8. Kiwifruit: taking its place in the global fruit bowl.

    Science.gov (United States)

    Ward, Carol; Courtney, David

    2013-01-01

    While the world total production of kiwifruit has increased by over 50% during the last decade, the kiwifruit remains a niche fruit, taking up an estimated 0.22% of the global fruit bowl, which is dominated by apples, oranges, and bananas. Even though kiwifruit's share of the global fruit bowl has remained largely unchanged over the past 15 years, the scope for growth in the category is significant, with the nutritional and production characteristics of kiwifruit being on the right side of key global consumer trends around health and sustainability. Taking advantage of these consumer trends is one of two key challenges for the global kiwifruit industry. The second challenge is to harness the diverse natural and cultivated range of kiwifruit varieties (colors, flavors, sizes, and shapes) to stimulate the interest of consumers and grow the share of kiwifruit in the fruit basket through selecting cultivars that can develop meaningful market segments and meet consumer demand. PMID:23394979

  9. Fast Collisionless Reconnection Condition and Self-Organization of Solar Coronal Heating

    CERN Document Server

    Uzdensky, Dmitri A

    2007-01-01

    I propose that solar coronal heating is a self-regulating process that keeps the coronal plasma roughly marginally collisionless. The self-regulating mechanism is based on the interplay of two effects. First, plasma density controls coronal energy release via the transition between the slow collisional Sweet--Parker regime and the fast collisionless reconnection regime. This transition takes place when the Sweet--Parker layer becomes thinner than the characteristic collisionless reconnection scale. I present a simple criterion for this transition in terms of the upstream plasma density and magnetic field and the global length of the reconnection layer. Second, coronal energy release by reconnection raises the ambient plasma density via chromospheric evaporation and this, in turn, temporarily inhibits subsequent reconnection involving the newly-reconnected loops. Over time, however, radiative cooling gradually lowers the density again below the critical value and fast reconnection again becomes possible. As a ...

  10. Key European Grid event to take place in Geneva

    CERN Multimedia

    2006-01-01

    EGEE'06 is the main conference of the EGEE project, which is co-funded by the European Union and hosted by CERN. More than 90 partners all over Europe and beyond are working together in EGEE to provide researchers in both academia and industry with access to major computing resources, independent of their geographic location. The largest user community of the EGEE Grid is the High-Energy Physics community and in particular the LHC experiments, which are already making heavy use of the infrastructure to prepare for data taking. However, with the many new challenges faced by EGEE in its second phase that started in April this year, an even broader audience than at previous EGEE conferences is expected. In particular, a large number of related Grid projects will feature prominently in both plenary and parallel sessions during the 5 days of this event. Industry will also be well represented, highlighting the EGEE project's commitment to technology transfer to industry. CERN is the host of the conference, which i...

  11. Reconnection in Marginally Collisionless Accretion Disk Coronae

    OpenAIRE

    Goodman, J.; Uzdensky, D.

    2008-01-01

    We point out that a conventional construction placed upon observations of accreting black holes, in which their nonthermal X-ray spectra are produced by inverse comptonization in a coronal plasma, suggests that the plasma is marginally collisionless. Recent developments in plasma physics indicate that fast reconnection takes place only in collisionless plasmas. As has recently been suggested for the Sun's corona, such marginal states may result from a combination of energy balance and the req...

  12. MHD simulations of three-dimensional Resistive Reconnection in a cylindrical plasma column

    CERN Document Server

    Striani, Edoardo; Vaidya, Bhargav; Bodo, Gianluigi; Ferrari, Attilio

    2016-01-01

    Magnetic reconnection is a plasma phenomenon where a topological rearrangement of magnetic field lines with opposite polarity results in dissipation of magnetic energy into heat, kinetic energy and particle acceleration. Such a phenomenon is considered as an efficient mechanism for energy release in laboratory and astrophysical plasmas. An important question is how to make the process fast enough to account for observed explosive energy releases. The classical model for steady state magnetic reconnection predicts reconnection times scaling as $S^{1/2}$ (where $S$ is the Lundquist number) and yields times scales several order of magnitude larger than the observed ones. Earlier two-dimensional MHD simulations showed that for large Lundquist number the reconnection time becomes independent of $S$ ("fast reconnection" regime) due to the presence of the secondary tearing instability that takes place for $S \\gtrsim 1 \\times 10^4$. We report on our 3D MHD simulations of magnetic reconnection in a magnetically confin...

  13. Nonlinear regimes of forced magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Vekstein, G., E-mail: g.vekstein@manchester.ac.uk [JBCA, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); STEL, Nagoya University, Nagoya, Aichi 464-8601 (Japan); Kusano, K. [STEL, Nagoya University, Nagoya, Aichi 464-8601 (Japan)

    2015-09-15

    This letter presents a self-consistent description of nonlinear forced magnetic reconnection in Taylor's model of this process. If external boundary perturbation is strong enough, nonlinearity in the current sheet evolution becomes important before resistive effects come into play. This terminates the current sheet shrinking that takes place at the linear stage and brings about its nonlinear equilibrium with a finite thickness. Then, in theory, this equilibrium is destroyed by a finite plasma resistivity during the skin-time, and further reconnection proceeds in the Rutherford regime. However, realization of such a scenario is unlikely because of the plasmoid instability, which is fast enough to develop before the transition to the Rutherford phase occurs. The suggested analytical theory is entirely different from all previous studies and provides proper interpretation of the presently available numerical simulations of nonlinear forced magnetic reconnection.

  14. Hadronisation Models and Colour Reconnection

    CERN Document Server

    Bierlich, Christian

    2016-01-01

    Enhanced production of hadrons with $s$-quark content has been observed in $pp$ collisions at LHC, and earlier in collisions of heavy nuclei. We review the string hadronisation formalism and correc- tions from rope hadronisation and colour reconnection, corrections that takes place in such dense environments, and are able to correctly describe data. Since such corrections are very sensitive to the modelling of transverse proton structure, we investigate two such models, and compare to final states. Finally we describe how such corrections can also give a possible explanation to collective phenomena observed in small systems.

  15. 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 t

  16. 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.

  17. Separatrices: the crux of reconnection

    CERN Document Server

    Lapenta, Giovanni; Divin, Andrey; Newman, David; Goldman, Martin

    2014-01-01

    Reconnection is one of the key processes in astrophysical and laboratory plasmas: it is the opposite of a dynamo. Looking at energy, a dynamo transforms kinetic energy in magnetic energy while reconnection takes magnetic energy and returns is to its kinetic form. Most plasma processes at their core involve first storing magnetic energy accumulated over time and then releasing it suddenly. We focus here on this release. A key concept in analysing reconnection is that of the separatrix, a surface (line in 2D) that separates the fresh unperturbed plasma embedded in magnetic field lines not yet reconnected with the hotter exhaust embedded in reconnected field lines. In kinetic physics, the separatrices become a layer where many key processes develop. We present here new results relative to the processes at the separatrices that regulate the plasma flow, the energisation of the species, the electromagnetic fields and the instabilities developing at the separatrices.

  18. DETERMINING THE FEATURES OF SPORTSWEAR TAKING PLACE IN FAST FASHION COLLECTIONS

    Directory of Open Access Journals (Sweden)

    Birsen ÇİLEROĞLU

    2014-07-01

    Full Text Available Spor ts occupies the first place among most siginificant factors increasing quality of life . It has b ecome difficult to allocate proper time for sports in the course of heavy work pace and flow of life . Such circumstances have led people to increase minor sport activities which could be done during short times allocated from daily living, thus, orienting people‟s clothing preference towards sportswear . The feeling of easiness and comfort sportswear offer to individuals enhances further such preference . The feeling of comfort individuals feel in their clothing depends on the presence of physiologic and psy chologic coherence between their bodies and environment . Demand for sportswear allowing easy - movement increased upon rise in life dynamism and standards, it began to be preferred regarding comfort of use and to take its place in daily clothing, too, define d as “casual” clothing . Spor tswear being preferred very much ; has caused the firms making and producing fashion and clothing design to give place in their collections to sportswear category . Particularly, in firms where model and clothing varieties are pl enty and new model design is made in short intervals, named as, “fast fashion” , tendency towards sportswear is growing increasingly . The sale rates of sportswear, utilization rates of which are growing increasingly, has maximum value among total clothing s ales in E - business field, too. In this research, it has been aimed to determine the features of sportswear taking place in “fast fashion” clothing collections . In order to accomplish this aim, 2014 collections of four different brands taking place in natio nal and international markets have been examined through visual analysis method . In the examinations; sportswear styles of the brand, model and style differences between brands and states of using 2014 fashion trends have been taken into account. The data obtained at the end of the analyses made have been

  19. Questions and Answers Regarding Actions to Take When Ending Shelter-in-Place

    Energy Technology Data Exchange (ETDEWEB)

    Shumpert, B.

    2003-12-30

    Shelter-in-place has found increasing acceptance as an effective protective action option for communities participating in the Chemical Stockpile Emergency Preparedness Program. Studies have confirmed that it can provide optimum protection under certain accident conditions. However, emergency managers and planners, as well as the public, continue to be troubled by the need to end sheltering when the plume has passed in order to avoid sustained exposure to the small amount of agent that has penetrated the shelter. One of the concerns posed by this necessity is uncertainty regarding what hazards will then be faced in the environment outside the shelter and what actions can be taken to avoid those hazards. This report attempts to address those uncertainties. It recognizes that there is an extremely low probability that the environment outside the shelter will be contaminated with chemical agent residue. However, as people comply with an official recommendation to leave their shelters, they probably can't be certain that the environment is free from contamination. Therefore, this report identifies and explains specific and simple actions they can take to avoid the possibility of exposure to chemical agent hazards outside their shelters. It addresses such issues as the actions people should take upon ending shelter-in-place, what clothing they should wear, how they should handle animals, and what they should do about food in their homes and produce in their gardens.

  20. Search for magnetic monopoles in magnetic reconnection regions

    CERN Document Server

    Zhang, Jun

    2015-01-01

    In order to satisfy the symmetry between electric and magnetic fields in the source free Maxwell's equations, electric charges might have magnetic counterparts: magnetic monopoles. Many methods and techniques are proposed to search for the monopoles, but no confirmed results have been obtained. Based on solar observations, we know that magnetic reconnections take place during eruptive solar activities. The magnetic field lines can be broken at first and then rejoined, implying that the magnetic fields are source-relevant at the broken moment. It is speculated that the magnetic lines undergo outward deflection movement during the broken moment, as the line tying effect disappears and the magnetic tension triggers the movement. The signal of the deflection is detected for the first time by EUV and H${\\alpha}$ observations in reconnection processes. We propose that the monopoles appear in magnetic reconnection regions at first, and then the annihilation of opposite polarity monopoles releases energy and perhaps ...

  1. 23 CFR 636.402 - What types of information exchange may take place after the release of the RFP document?

    Science.gov (United States)

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false What types of information exchange may take place after... What types of information exchange may take place after the release of the RFP document? Certain types.... These communication methods are optional. Type of information exchange When Purpose Parties involved...

  2. [Marketing approval and market surveillance of medical devices in Germany: Where does policy integration take place?].

    Science.gov (United States)

    Lang, Achim

    2014-01-01

    Since 2011 new regulatory measures regarding medical devices have been set up with the aim to eliminate obstacles to innovations and to find more coordinated ways to marketing authorisation and market surveillance. This essay investigates whether these new and existing coordination mechanisms build up to a Joined-up Government approach. The analysis shows that the regulatory process should be adjusted along several dimensions. First, many organisations lack awareness regarding their stakeholders and focus solely on their immediate organisational activities. Second, the regulatory process (marketing authorisation and market surveillance) is too fragmented for an effective communication to take place. Finally, the underlying strategy process is an ad-hoc approach lacking continuity and continued involvement of, in particular, the responsible federal ministries. PMID:25066351

  3. [Marketing approval and market surveillance of medical devices in Germany: Where does policy integration take place?].

    Science.gov (United States)

    Lang, Achim

    2014-01-01

    Since 2011 new regulatory measures regarding medical devices have been set up with the aim to eliminate obstacles to innovations and to find more coordinated ways to marketing authorisation and market surveillance. This essay investigates whether these new and existing coordination mechanisms build up to a Joined-up Government approach. The analysis shows that the regulatory process should be adjusted along several dimensions. First, many organisations lack awareness regarding their stakeholders and focus solely on their immediate organisational activities. Second, the regulatory process (marketing authorisation and market surveillance) is too fragmented for an effective communication to take place. Finally, the underlying strategy process is an ad-hoc approach lacking continuity and continued involvement of, in particular, the responsible federal ministries.

  4. Effect of electron inertia in two-fluid magnetic reconnection

    Science.gov (United States)

    Gomez, Daniel; Dmitruk, Pablo; Andrés, Nahuel

    2016-07-01

    In space plasmas, magnetic reconnection is an important energy conversion process. Within the traditional one-fluid resistive MHD description, the Sweet-Parker model leads to extremely low reconnection rates for virtually all space physics applications. Within the theoretical framework of two-fluid MHD, we retain the effects of the Hall current and electron inertia and neglect dissipative effects such as viscosity and electric resistivity. This description brings two new spatial scales into play, such as the ion and electron inertial lengths. In absence of resistive dissipation, reconnection can only be attained by the action of electron inertia. We performed two-fluid simulations using a pseudo-spectral code which yields exact conservation (to round-off errors) of the ideal invariants. Our simulations show that when the effects of electron inertia are retained, magnetic reconnection takes place. Moreover, in a stationary regime the reconnection rate is simply proportional to the ion inertial length, as also emerges from a scaling law derived from dimensional arguments.

  5. 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.

  6. Observing the release of twist by magnetic reconnection in a solar filament eruption

    Science.gov (United States)

    Xue, Zhike; Yan, Xiaoli; Cheng, Xin; Yang, Liheng; Su, Yingna; Kliem, Bernhard; Zhang, Jun; Liu, Zhong; Bi, Yi; Xiang, Yongyuan; Yang, Kai; Zhao, Li

    2016-06-01

    Magnetic reconnection is a fundamental process of topology change and energy release, taking place in plasmas on the Sun, in space, in astrophysical objects and in the laboratory. However, observational evidence has been relatively rare and typically only partial. Here we present evidence of fast reconnection in a solar filament eruption using high-resolution H-alpha images from the New Vacuum Solar Telescope, supplemented by extreme ultraviolet observations. The reconnection is seen to occur between a set of ambient chromospheric fibrils and the filament itself. This allows for the relaxation of magnetic tension in the filament by an untwisting motion, demonstrating a flux rope structure. The topology change and untwisting are also found through nonlinear force-free field modelling of the active region in combination with magnetohydrodynamic simulation. These results demonstrate a new role for reconnection in solar eruptions: the release of magnetic twist.

  7. Observing the release of twist by magnetic reconnection in a solar filament eruption

    Science.gov (United States)

    Xue, Zhike; Yan, Xiaoli; Cheng, Xin; Yang, Liheng; Su, Yingna; Kliem, Bernhard; Zhang, Jun; Liu, Zhong; Bi, Yi; Xiang, Yongyuan; Yang, Kai; Zhao, Li

    2016-01-01

    Magnetic reconnection is a fundamental process of topology change and energy release, taking place in plasmas on the Sun, in space, in astrophysical objects and in the laboratory. However, observational evidence has been relatively rare and typically only partial. Here we present evidence of fast reconnection in a solar filament eruption using high-resolution H-alpha images from the New Vacuum Solar Telescope, supplemented by extreme ultraviolet observations. The reconnection is seen to occur between a set of ambient chromospheric fibrils and the filament itself. This allows for the relaxation of magnetic tension in the filament by an untwisting motion, demonstrating a flux rope structure. The topology change and untwisting are also found through nonlinear force-free field modelling of the active region in combination with magnetohydrodynamic simulation. These results demonstrate a new role for reconnection in solar eruptions: the release of magnetic twist. PMID:27306479

  8. Comparison of test particle acceleration in torsional spine and fan reconnection regimes

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinpour, M., E-mail: hosseinpour@tabrizu.ac.ir; Mehdizade, M.; Mohammadi, M. A. [Plasma Physics Department, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2014-10-15

    Magnetic reconnection is a common phenomenon taking place in astrophysical and space plasmas, especially in solar flares which are rich sources of highly energetic particles. Torsional spine and fan reconnections are important mechanisms proposed for steady-state three-dimensional null-point reconnection. By using the magnetic and electric fields for these regimes, we numerically investigate the features of test particle acceleration in both regimes with input parameters for the solar corona. By comparison, torsional spine reconnection is found to be more efficient than torsional fan reconnection in an acceleration of a proton to a high kinetic energy. A proton can gain as high as 100 MeV of relativistic kinetic energy within only a few milliseconds. Moreover, in torsional spine reconnection, an accelerated particle can escape either along the spine axis or on the fan plane depending on its injection position. However, in torsional fan reconnection, the particle is only allowed to accelerate along the spine axis. In addition, in both regimes, the particle's trajectory and final kinetic energy depend on the injection position but adopting either spatially uniform or non-uniform localized plasma resistivity does not much influence the features of trajectory.

  9. Comparison of test particle acceleration in torsional spine and fan reconnection regimes

    International Nuclear Information System (INIS)

    Magnetic reconnection is a common phenomenon taking place in astrophysical and space plasmas, especially in solar flares which are rich sources of highly energetic particles. Torsional spine and fan reconnections are important mechanisms proposed for steady-state three-dimensional null-point reconnection. By using the magnetic and electric fields for these regimes, we numerically investigate the features of test particle acceleration in both regimes with input parameters for the solar corona. By comparison, torsional spine reconnection is found to be more efficient than torsional fan reconnection in an acceleration of a proton to a high kinetic energy. A proton can gain as high as 100 MeV of relativistic kinetic energy within only a few milliseconds. Moreover, in torsional spine reconnection, an accelerated particle can escape either along the spine axis or on the fan plane depending on its injection position. However, in torsional fan reconnection, the particle is only allowed to accelerate along the spine axis. In addition, in both regimes, the particle's trajectory and final kinetic energy depend on the injection position but adopting either spatially uniform or non-uniform localized plasma resistivity does not much influence the features of trajectory

  10. Model of Wagons’ Placing-In and Taking-Out Problem in a Railway Station and Its Heuristic Algorithm

    Directory of Open Access Journals (Sweden)

    Chuijiang Guo

    2014-01-01

    Full Text Available Placing-in and taking-out wagons timely can decrease wagons’ dwell time in railway stations, improve the efficiency of railway transportation, and reduce the cost of goods transportation. We took the locomotive running times between goods operation sites as weights, so the wagons’ placing-in and taking-out problem could be regarded as a single machine scheduling problem, 1pijCmax, which could be transformed into the shortest circle problem in a Hamilton graph whose relaxation problem was an assignment problem. We used a Hungarian algorithm to calculate the optimal solution of the assignment problem. Then we applied a broken circle and connection method, whose computational complexity was O(n2, to find the available satisfactory order of wagons’ placing-in and taking-out. Complex problems, such as placing-in and transferring combined, taking-out and transferring combined, placing-in and taking-out combined, or placing-in, transferring, and taking-out combined, could also be resolved with the extended algorithm. A representative instance was given to illustrate the reliability and efficiency of our results.

  11. Multiscale dynamics based on kinetic simulation of collisionless magnetic reconnection

    Science.gov (United States)

    Fujimoto, Keizo; Takamoto, Makoto

    2016-07-01

    Magnetic reconnection is a natural energy converter which allows explosive energy release of the magnetic field energy into plasma kinetic energy. The reconnection processes inherently involve multi-scale process. The breaking of the field lines takes place predominantly in a small region called the diffusion region formed near the x-line, while the fast plasma jets resulting from reconnection extend to a distance far beyond the ion kinetic scales from the x-line. There has been a significant gap in understanding of macro-scale and micro-scale processes. The macro-scale model of reconnection has been developed using the magnetohydrodynamics (MHD) equations, while the micro-scale processes around the x-line have been based on kinetic equations including the ion and electron inertia. The problem is that these two kinds of model have significant discrepancies. It has been believed without any guarantee that the microscopic model near the x-line would connect to the macroscopic model far downstream of the x-line. In order to bridge the gap between the macro and micro-scale processes, we have performed large-scale particle-in-cell simulations with the adaptive mesh refinement. The simulation results suggest that the microscopic processes around the x-line do not connect to the previous MHD model even in the region far downstream of the x-line. The slow mode shocks and the associated plasma acceleration do not appear at the exhaust boundary of kinetic reconnection. Instead, the ions are accelerated due to the Speiser motion in the current layer extending to a distance beyond the kinetic scales. The different acceleration mechanisms between the ions and electrons lead to the Hall current system in broad area of the exhaust. Therefore, the previous MHD model could be inappropriate for collisionless magnetic reconnection. Ref. K. Fujimoto & M. Takamoto, Phys. Plasmas, 23, 012903 (2016).

  12. Taking back place-names – from dusty library to digital life

    DEFF Research Database (Denmark)

    Knudsen, Bo Nissen

    mobility of the book format into a digital context – by making the content available as an application for mobile devices such as smart phones and iPads? Adding geocodes to the name articles could open up the possibility of a digital place-name lexicon allowing the end user to move around in a place...

  13. Spirit of place in science park. Take ZJ Inno-Park as an example

    OpenAIRE

    Wang, Biao; Adolphe, Luc

    2012-01-01

    International audience Concerning the environment feature and its stabilisation as well as its development, the theory of spirit of place is used in this article to analyse the main expressing forms of the spirit of place in science park, with an example from one of the most famous science parks in China, Zhangjiang Inno-Park. The aim of this article is to search and establish the character of the place in science park as well as its humane features, and to give some practical advices for ...

  14. An Experimental Investigation of the Process of Isotope Exchange that Takes Place when Heavy Water Is Exposed to the Atmosphere

    Science.gov (United States)

    Deeney, F. A.; O'Leary, J. P.

    2009-01-01

    We have used the recently developed method for rapid measurement of maximum density temperature to determine the rate at which hydrogen and deuterium isotope exchange takes place when a sample of heavy water is exposed to the atmosphere. We also provide a simple explanation for the observed linear rate of transition. (Contains 2 figures.)

  15. 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

  16. Solar flare mechanism based on magnetic arcade reconnection and island merging

    Energy Technology Data Exchange (ETDEWEB)

    C.Z. Chen; G.S. Choe

    2000-06-15

    The authors propose a model describing physical processes of solar flares based on resistive reconnection of magnetic field subject to continuous increase of magnetic shear in the arcade. The individual flaring process consists of magnetic reconnection of arcade field lines, generation of magnetic islands in the magnetic arcade, and coalescence of magnetic islands. When a magnetic arcade is sheared (either by foot point motion or by flux emergence), a current sheet is formed and magnetic reconnection can take place to form a magnetic island. A continuing increase of magnetic shear can trigger a new reconnection process and create a new island in the under lying arcade below the magnetic island. The new born island rises faster than the preceding island and merges with it to form one island. Before completing the island merging process, the new born island exhibits two phases of rising motion: a first phase with a slower rising speed and a second phase with a faster rising speed. The flare plasma heating occurs mainly due to magnetic reconnection in the current sheet under the new born island. The new born island represents the X-ray plasma ejecta which shows two phases of rising motion observed by Yohkoh [Ohyama and Shibata (1997)]. The first phase with slower new born island rising speed corresponds to the early phase of reconnection of line-tied field in the underlying current sheet and is considered as the preflare phase. In the second phase, the island coalescence takes place, and the underlying current sheet is elongated so that the line-tied arcade field reconnection rate is enhanced. This phase is interpreted as the impulsive phase or the flash phase of flares. The obtained reconnection electric field is large enough to accelerate electrons to an energy level higher than 10 keV, which is necessary for observed hard X-ray emissions. After merging of the islands is completed, magnetic reconnection continues in the current sheet under the integrated island for

  17. On the electron dynamics during island coalescence in asymmetric magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Cazzola, E., E-mail: emanuele.cazzola@wis.kuleuven.be; Innocenti, M. E., E-mail: mariaelena.innocenti@wis.kuleuven.be; Lapenta, G., E-mail: giovanni.lapenta@wis.kuleuven.be [Center for Mathematical Plasma Astrophysics, Department of Mathematics, K.U. Leuven (University of Leuven), Celestijnenlaan 200B, B-3001 Leuven (Belgium); Markidis, S., E-mail: markidis@pdc.kth.se [PDC Center for High Performance Computing, KTH Royal Institute of Technology, Teknikringen 14, 10044 Stockholm (Sweden); Goldman, M. V., E-mail: martin.goldman@Colorado.edu; Newman, D. L., E-mail: david.newman@colorado.edu [Center for Integrated Plasma Studies, University of Colorado Boulder, Gamow Tower, Boulder, Colorado 80309-0390 (United States)

    2015-09-15

    We present an analysis of the electron dynamics during rapid island merging in asymmetric magnetic reconnection. We consider a doubly periodic system with two asymmetric transitions. The upper layer is an asymmetric Harris sheet of finite width perturbed initially to promote a single reconnection site. The lower layer is a tangential discontinuity that promotes the formation of many X-points, separated by rapidly merging islands. Across both layers, the magnetic field and the density have a strong jump, but the pressure is held constant. Our analysis focuses on the consequences of electron energization during island coalescence. We focus first on the parallel and perpendicular components of the electron temperature to establish the presence of possible anisotropies and non-gyrotropies. Thanks to the direct comparison between the two different layers simulated, we can distinguish three main types of behavior characteristic of three different regions of interest. The first type represents the regions where traditional asymmetric reconnections take place without involving island merging. The second type of regions instead shows reconnection events between two merging islands. Finally, the third regions identify the regions between two diverging island and where typical signature of reconnection is not observed. Electrons in these latter regions additionally show a flat-top distribution resulting from the saturation of a two-stream instability generated by the two interacting electron beams from the two nearest reconnection points. Finally, the analysis of agyrotropy shows the presence of a distinct double structure laying all over the lower side facing the higher magnetic field region. This structure becomes quadrupolar in the proximity of the regions of the third type. The distinguishing features found for the three types of regions investigated provide clear indicators to the recently launched Magnetospheric Multiscale NASA mission for investigating magnetopause

  18. Multi-Hierarchy Simulation of Collisionless Driven Reconnection by Real-Space Decomposition

    International Nuclear Information System (INIS)

    The first results on analysis of collisionless driven reconnection with a multihierarchy simulation model are reported. In the multi-hierarchy simulation model, real space in a simulation consists of three parts: a magnetohydrodynamics (MHD) domain to deal with macroscopic dynamics, a particle-in-cell (PIC) domain to solve microscopic kinetic physics from the first principle, and an interface domain to interlock the two domains. By means of multi-hierarchy simulations, the influence of macroscopic dynamics on microscopic physics of magnetic reconnection is investigated. Dynamical behaviors of collisionless reconnection in the PIC domain depend strongly on plasma inflows from the MHD domain. It is found that if the width of an MHD inflow increases as vw ∼< vA0, where vA0 is the Alfvén speed at the upstream boundary, magnetic reconnection has only a single X-point., while in cases of vw∼>2.0vA0, reconnection with multiple X-points takes place

  19. Solar wind transport into magnetosphere caused by magnetic reconnection at high latitude magnetopause during northward IMF: Cluster-DSP conjunction observations

    Institute of Scientific and Technical Information of China (English)

    YAN GuangQing; SHEN Chao; LIU ZhenXing; M. DUNLOP; E. LUOEK; H. REME; C. M. OARR; ZHANG TieLong

    2008-01-01

    An event of Cluster-Double Star conjunction observations of magnetic reconnec-tion at high latitude magnetopause nightside of both cusps and solar wind trans-port into magnetosphere caused by such reconnection process has been investi-gated. During northward IMF, Cluster/SC1 observed accelerated flows and ion heating associated with magnetic reconnection at high latitude magnetopause night$1de of southern cusp. And Double Star observed cold dense solar wind plasma transported into dayside magnetosphere. The analysis on such conjunction observations shows that: (1) during northward IMF, magnetic reconnection occurs at high latitude nightside of southern cusp, accompanied by accelerated flows that are observed by Cluster/SC1; (2) the direction of the accelerated flows, with its sunward component Vx, dawnward component Vy, northward component Vz, is quite consistent with the theoretical anticipation under the condition of northward IMF with dawnward component By; (3) reconnection can heat plasma more in par-allel direction than in perpendicular direction, to a level of about 4 keV; (4) with reconnection taking place at high latitude magnetopause nightside of the southern cusp, TC-1 observed cold and dense plasma transported into magnetosphere; (5) by reconnection at high latitude magnetopause nightside of both cusps, solar wind flux tube can be captured by magnetosphere and pulled into dayside magneto-sphere.

  20. 23 CFR 636.401 - What types of information exchange may take place prior to the release of the RFP document?

    Science.gov (United States)

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false What types of information exchange may take place prior... What types of information exchange may take place prior to the release of the RFP document? Verbal or written information exchanges (such as in the first-phase of a two-phase selection procedure) must...

  1. INVESTIGATION OF PROCESSES THAT TAKE PLACE UNDER THE WARMING OF TITANIUM DIOXIDE, RECEIVED VIA HYDROLYSIS OF VARIOUS TITANIUM ALCO-OXIDES

    OpenAIRE

    Potapov, I.; Onorin, S.; Poylov, V.; Smirnov, S.; Puzanov, A.

    2011-01-01

    Processes that take place under the warming of titanium dioxide pre-cursors, received via hydrolysis of various titanium alco-oxides have been studied. Temperature intervals have been investigated within which processes of dehydration, deposition, and crystallization take place, as well as a phase composition of products that form under pre-cursors thermal processing.

  2. LIDAR for remote sensing of contaminations on water and earth surfaces taking place during oil-gas production

    Science.gov (United States)

    Pashayev, A.; Tagiyev, B.; Allahverdiyev, K.; Musayev, A.; Sadikhov, I.

    2015-12-01

    Remote sensing of contaminations on water and earth surfaces (oil spills, films) taking place during oil-gas extraction is an interesting and actual problem. This problem may be solved by using different methods of optical spectroscopy, including: •Raman scattering; •light induced breakdown spectroscopy (LIBS); •fluorescence spectroscopy. Fluorescence Light Detection and Ranging (LIDAR) LIDARs are successfully used for remote sensing of chemical and biological substances at atmosphere. A new laser induced fluorescence (LIF) KA-14 LIDAR system for detecting of oil spills on the sea surface was employed at the National Aviation Academy of Azerbaijan. LIDAR's parameters are as follows: •laser CFR 200- type QUANTEL, λ = 355 nm, beam Ø = 5.35 mm, f = 20 Hz, pulse duration τ = 7 ns, pulse power 60 mJ; •diameter of Newtonian- type telescope is 200 mm; •collimator expansion of the laser beam diameter- not less than 3; •angle range of telescope measurements relative to horizon: from -20 to +20 degree; •spectral range of measurements: from 380 to 750 nm, number of spectral channels- 32; •maximum range of measurements- not less than 250 m. This LIDAR is the first performing these kind of research not only on the Azerbaijan beach of Caspian sea, but also on the earth places of Absheron peninsula, where oil-gas production takes place. We hope that the performance of LIDAR will have an International recognition and will make noticeable input on the International Research of Caspian sea surfaces.

  3. On Turbulent Reconnection

    OpenAIRE

    Kim, Eun-Jin; Diamond, P. H.

    2001-01-01

    We examine the dynamics of turbulent reconnection in 2D and 3D reduced MHD by calculating the effective dissipation due to coupling between small-scale fluctuations and large-scale magnetic fields. Sweet-Parker type balance relations are then used to calculate the global reconnection rate. Two approaches are employed -- quasi-linear closure and an eddy-damped fluid model. Results indicate that despite the presence of turbulence, the reconnection rate remains inversely proportional to $\\sqrt{R...

  4. Plasmoids in Reconnecting Current Sheets: Solar and Terrestrial Contexts Compared

    CERN Document Server

    Lin, J; Farrugia, C J

    2008-01-01

    Magnetic reconnection plays a crucial role in violent energy conversion occurring in the environments of high electrical conductivity, such as the solar atmosphere, magnetosphere, and fusion devices. We focus on the morphological features of the process in two different environments, the solar atmosphere and the geomagnetic tail. In addition to indirect evidence that indicates reconnection in progress or having just taken place, such as auroral manifestations in the magnetosphere and the flare loop system in the solar atmosphere, more direct evidence of reconnection in the solar and terrestrial environments is being collected. Such evidence includes the reconnection inflow near the reconnecting current sheet, and the outflow along the sheet characterized by a sequence of plasmoids. Both turbulent and unsteady Petschek-type reconnection processes could account for the observations. We also discuss other relevant observational consequences of both mechanisms in these two settings. While on face value, these are...

  5. The albedo problem in the case of multiple synthetic scattering taking place in a plane-symmetric slab

    International Nuclear Information System (INIS)

    An approximate model based on an improved diffusion-type theory is established for treating multiple synthetic scattering in a homogeneous slab of finite thickness. As in the case of the exact treatment given in the preceding paper (Part I), it appears possible to transform the considered transport problem into an equivalent fictitious one involving multiple isotropic scattering, therefore permitting the application of an established corrected diffusion theory for treating isotropic scattering taking place in a convex homogeneous medium bounded by a vacuum in the presence of various types of sources. The approximate values of the reflection and transmission coefficients are compared with the rigorous values listed in Part I. In this way, the high accuracy of the approximation is clearly demonstrated. (author)

  6. Modeling of the thermohydraulic phenomena taking place during the quench of a superconducting magnet cooled with superfluid helium

    International Nuclear Information System (INIS)

    One of the main issues related to the conception of a superconducting magnet cooled by a superfluid helium bath (like the Iseult magnet) is to insure the magnet safety as well as the whole cryogenic facility safety in case of accidental quench. In order to find a solution to this problem, we first have to identify the physical mechanisms which drive the pressure rise during a quench. This is why our study deals with the modeling of the thermohydraulic phenomena taking place during such a magnet quench. First of all, we performed and analyzed local pressure rise experiments in a heated helium channel. A numerical thermohydraulic model was developed for this study. Quench experiments were then performed on an 8-T (Seht) superconducting coil cooled by a superfluid helium bath. These experiments allowed us to make a detailed analysis of the physical mechanisms which drive the global pressure rise in case of quench as well as the strong coupling between this pressure rise and the normal zone propagation. Following this analysis, a complete model of normal zone propagation and pressure rising during a quench was developed. This model is a first step toward predictive modeling of the pressure rise during the quench of a superconducting magnet cooled by a superfluid helium bath. (author)

  7. Fragment Driven Magnetic Reconnection

    CERN Document Server

    Galsgaard, K

    2004-01-01

    In this paper, we investigate a simple model where two, initially unconnected, flux systems are forced to interact in response to the imposed boundary driving by solving the non-ideal 3D MHD equations numerically. The reconnection rate of the dynamical process is determined and compared with the corresponding rate for the potential evolution of the magnetic field. This shows that the dynamic reconnection rate is about a factor of two smaller than the potential (perfect, instantaneous) rate for realistic solar driving velocities demonstrating that this three-dimensional magnetic reconnection process is fast. The energy input for a fixed advection distance is found to be independent of the driving velocity. The Joule dissipation associated with the reconnection process is also found to be basically dependent on the advection distance rather than driving velocity. This implies that the timescale for the event determines the effect the heating has on the temperature increase. Finally, the numerical experiments in...

  8. A THEMIS Survey of Flux Ropes and Traveling Compression Regions: Location of the Near-Earth Reconnection Site During Solar Minimum

    Science.gov (United States)

    Imber, S. M.; Slavin, J. A.; Auster, H. U.; Angelopoulos, V.

    2011-01-01

    A statistical study of flux ropes and traveling compression regions (TCRs) during the Time History of Events and Macroscale Interactions during Substorms (THEMIS) second tail season has been performed. A combined total of 135 flux ropes and TCRs in the range GSM X approx -14 to -31 R(sub E) were identified, many of these occurring in series of two or more events separated by a few tens of seconds. Those occurring within 10 min of each other were combined into aggregated reconnection events. For the purposes of this survey, these are most likely the products of reconnect ion occurring simultaneously at multiple, closely spaced x-lines as opposed to statistically independent episodes of reconnection. The 135 flux ropes and TCRs were grouped into 87 reconnection events; of these, 28 were moving tailward and 59 were moving Earthward. The average location of the near-Earth x-line determined from statistical analysis of these reconnection events is (X(sub GSM), Y*(sub GSM)) = (-30R(sub E), 5R(sub E)), where Y* includes a correction for the solar aberration angle. A strong east-west asymmetry is present in the tailward events, with >80% being observed at GSM Y* > O. Our results indicate that the Earthward flows are similarly asymmetric in the midtail region, becoming more symmetric inside - 18 R(sub E). Superposed epoch analyses indicate that the occurrence of reconnection closer to the Earth, i.e., X > -20 R(sub E), is associated with elevated solar wind velocity and enhanced negative interplanetary magnetic field B(sub z). Reconnection events taking place closer to the Earth are also far more effective in producing geomagnetic activity, judged by the AL index, than reconnection initiated beyond X approx -25 R(sub E).

  9. Boosting magnetic reconnection by viscosity and thermal conduction

    Science.gov (United States)

    Minoshima, Takashi; Miyoshi, Takahiro; Imada, Shinsuke

    2016-07-01

    Nonlinear evolution of magnetic reconnection is investigated by means of magnetohydrodynamic simulations including uniform resistivity, uniform viscosity, and anisotropic thermal conduction. When viscosity exceeds resistivity (the magnetic Prandtl number P r m > 1 ), the viscous dissipation dominates outflow dynamics and leads to the decrease in the plasma density inside a current sheet. The low-density current sheet supports the excitation of the vortex. The thickness of the vortex is broader than that of the current for P r m > 1 . The broader vortex flow more efficiently carries the upstream magnetic flux toward the reconnection region, and consequently, boosts the reconnection. The reconnection rate increases with viscosity provided that thermal conduction is fast enough to take away the thermal energy increased by the viscous dissipation (the fluid Prandtl number Pr < 1). The result suggests the need to control the Prandtl numbers for the reconnection against the conventional resistive model.

  10. Boosting Magnetic Reconnection by Viscosity and Thermal Conduction

    CERN Document Server

    Minoshima, Takashi; Imada, Shinsuke

    2016-01-01

    Nonlinear evolution of magnetic reconnection is investigated by means of magnetohydrodynamic simulations including uniform resistivity, uniform viscosity, and anisotropic thermal conduction. When viscosity exceeds resistivity (the magnetic Prandtl number Prm > 1), the viscous dissipation dominates outflow dynamics and leads to the decrease in the plasma density inside a current sheet. The low-density current sheet supports the excitation of the vortex. The thickness of the vortex is broader than that of the current for Prm > 1. The broader vortex flow more efficiently carries the upstream magnetic flux toward the reconnection region, and consequently boosts the reconnection. The reconnection rate increases with viscosity provided that thermal conduction is fast enough to take away the thermal energy increased by the viscous dissipation (the fluid Prandtl number Pr < 1). The result suggests the need to control the Prandtl numbers for the reconnection against the conventional resistive model.

  11. 49 CFR 40.41 - Where does a urine collection for a DOT drug test take place?

    Science.gov (United States)

    2010-10-01

    ... used for adulteration and substitution (e.g., water faucets, soap dispensers) and providing moist... could be used for adulteration and substitution (e.g., water faucets, soap dispensers) and place...

  12. Plasmoids in Reconnecting Current Sheets: Solar and Terrestrial Contexts Compared

    OpenAIRE

    Lin, J.; Cranmer, S. R.; Farrugia, C. J.

    2008-01-01

    Magnetic reconnection plays a crucial role in violent energy conversion occurring in the environments of high electrical conductivity, such as the solar atmosphere, magnetosphere, and fusion devices. We focus on the morphological features of the process in two different environments, the solar atmosphere and the geomagnetic tail. In addition to indirect evidence that indicates reconnection in progress or having just taken place, such as auroral manifestations in the magnetosphere and the flar...

  13. Cognitive Distance in and Between COP’s and Firms : Where do Exploitation and Exploration take Place, and How are they Connected?

    NARCIS (Netherlands)

    Nooteboom, B.

    2007-01-01

    This paper contributes to the analysis of where and how both exploitation and exploration may take place inside and between communities and organizations. It connects with the discussion of differences between communities of practice and epistemic communities. The analysis allows for differences in

  14. Cluster Observations of reconnection along the dusk flank of the magnetosphere

    Science.gov (United States)

    Escoubet, C.-Philippe; Grison, Benjamin; Berchem, Jean; Trattner, Karlheinz; Lavraud, Benoit; Pitout, Frederic; Soucek, Jan; Richard, Robert; Laakso, Harri; Masson, Arnaud; Dunlop, Malcolm; Dandouras, Iannis; Reme, Henri; Fazakerley, Andrew; Daly, Patrick

    2015-04-01

    which would be an indication that reconnection is also taking place near the exterior cusp quasi-simultaneously.

  15. 76 FR 40697 - Water and Wastewater Trade Mission to Australia Taking Place September 12-15, 2011; Now Opened to...

    Science.gov (United States)

    2011-07-11

    ... or production delays. In addition, AIMEX, Asia-Pacific's International Mining Exhibition, is taking... fee schedule that became effective May 1, 2008. See http://www.export.gov/newsletter/march2008... open and public manner, including publication in the Federal Register (...

  16. Interchange Reconnection Alfven Wave Generation

    CERN Document Server

    Lynch, B J; Li, Y

    2014-01-01

    Given recent observational results of interchange reconnection processes in the solar corona and the theoretical development of the S-Web model for the slow solar wind, we present further analysis of the 3D MHD simulation of interchange reconnection by Edmondson et al. (Astrophys. J. 707, 1427, 2009). Specifically, we analyze the consequences of the dynamic streamer belt jump that corresponds to flux opening by interchange reconnection. Information about the magnetic field restructuring by interchange reconnection is carried throughout the system by Alfven waves propagating away from the reconnection region, distributing the shear and twist imparted by the driving flows, including shedding the injected stress-energy and accumulated magnetic helicity along newly-open field lines. We quantify the properties of the reconnection-generated wave activity in the simulation. There is a localized high frequency component associated with the current sheet/reconnection site and an extended low frequency component associ...

  17. Reconnection in tokamaks

    International Nuclear Information System (INIS)

    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

  18. Colour Reconnection at LEPII

    CERN Document Server

    Abreu, P

    2001-01-01

    The preliminary results on the search of colour reconnection effects (CR) from the four experiments at LEP, Aleph, Delphi, L3 and Opal, are reviewed. Extreme models are excluded by studies of standard variables, and on going studies of a method first suggested by L3, the particle flow method, are yet inconclusive.

  19. Turbulent General Magnetic Reconnection

    Science.gov (United States)

    Eyink, G. L.

    2015-07-01

    Plasma flows with a magnetohydrodynamic (MHD)-like turbulent inertial range, such as the solar wind, require a generalization of general magnetic reconnection (GMR) theory. We introduce the slip velocity source vector per unit arclength of field line, the ratio of the curl of the non-ideal electric field in the generalized Ohm’s Law and magnetic field strength. It diverges at magnetic nulls, unifying GMR with null-point reconnection. Only under restrictive assumptions is the slip velocity related to the gradient of quasi-potential (which is the integral of parallel electric field along magnetic field lines). In a turbulent inertial range, the non-ideal field becomes tiny while its curl is large, so that line slippage occurs even while ideal MHD becomes accurate. The resolution is that ideal MHD is valid for a turbulent inertial range only in a weak sense that does not imply magnetic line freezing. The notion of weak solution is explained in terms of renormalization group (RG) type theory. The weak validity of the ideal Ohm’s law in the inertial range is shown via rigorous estimates of the terms in the generalized Ohm’s Law. All non-ideal terms are irrelevant in the RG sense and large-scale reconnection is thus governed solely by ideal dynamics. We discuss the implications for heliospheric reconnection, in particular for deviations from the Parker spiral model. Solar wind observations show that reconnection in a turbulence-broadened heliospheric current sheet, which is consistent with Lazarian-Vishniac theory, leads to slip velocities that cause field lines to lag relative to the spiral model.

  20. 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

  1. Inhomogeneous turbulence in magnetic reconnection

    Science.gov (United States)

    Yokoi, Nobumitsu

    2016-07-01

    Turbulence is expected to play an essential role in enhancing magnetic reconnection. Turbulence associated with magnetic reconnection is highly inhomogeneous: it is generated by inhomogeneities of the field configuration such as the velocity shear, temperature gradient, density stratification, magnetic shear, etc. This self-generated turbulence affects the reconnection through the turbulent transport. In this reconnection--turbulence interaction, localization of turbulent transport due to dynamic balance between several turbulence effects plays an essential role. For investigating inhomogeneous turbulence in a strongly nonlinear regime, closure or turbulence modeling approaches provide a powerful tool. A turbulence modeling approach for the magnetic reconnection is introduced. In the model, the mean-field equations with turbulence effects incorporated are solved simultaneously with the equations of turbulent statistical quantities that represent spatiotemporal properties of turbulence under the effect of large-scale field inhomogeneities. Numerical simulations of this Reynolds-averaged turbulence model showed that self-generated turbulence enhances magnetic reconnection. It was pointed out that reconnection states may be divided into three category depending on the turbulence level: (i) laminar reconnection; (ii) turbulent reconnection, and (iii) turbulent diffusion. Recent developments in this direction are also briefly introduced, which includes the magnetic Prandtl number dependence, spectral evolution, and guide-field effects. Also relationship of this fully nonlinear turbulence approach with other important approaches such as plasmoid instability reconnection will be discussed.

  2. Place Branding

    OpenAIRE

    Beckmann, Suzanne C.; Zenker, Sebastian

    2012-01-01

    Cities increasingly brand themselves as an attractive place for tourists, investors, business and workforce. Yet, most place branding efforts do not take the diversity of their stakeholders and the variety of place perceptions into account. Our study, however, reveals significant discrepancies between internal and external stakeholders’ mental representations of a place brand, using the city of Hamburg as an example. We therefore argue that place brand management needs to align its brand comm...

  3. Biosynthesis of intestinal microvillar proteins. Evidence for an intracellular sorting taking place in, or shortly after, exit from the Golgi complex

    DEFF Research Database (Denmark)

    Danielsen, E M; Cowell, G M

    1985-01-01

    of the enzyme to the apical plasma membrane. A crude membrane preparation from labelled explants was used in immunoelectrophoretic purification of membranes to determine at what stage during intracellular transport newly synthesized microvillar enzymes are sorted, i.e., accumulated in areas of the membrane from...... that for microvillar enzymes, the aspects of sorting studied take place in, or shortly after exit from, the Golgi complex....

  4. Oscillation of Newly Formed Loops After Magnetic Reconnection in the Solar Chromosphere

    CERN Document Server

    Yang, Shuhong

    2016-01-01

    With the high spatial and temporal resolution H$\\alpha$ images from the New Vacuum Solar Telescope, we focus on two groups of loops with a X-shaped configuration in the dynamic chromosphere. We find that the anti-directed loops approach each other and reconnect continually. The connectivity of the loops is changed and new loops are formed and stack together. The stacked loops are sharply bent, implying that they are greatly impacted by the magnetic tension force. When another more reconnection process takes place, one new loop is formed and stacks with the previously formed ones. Meanwhile, the stacked loops retract suddenly and move toward the balance position, performing an overshoot movement, which led to an oscillation with an average period of about 45 s. The oscillation of newly formed loops after magnetic reconnection in the chromosphere is observed for the first time. We suggest that the stability of the stacked loops is destroyed due to the join of the last new loop and then suddenly retract under th...

  5. Micro-instabilities and anomalous transport effects in collisionless guide field reconnection

    Science.gov (United States)

    Munoz Sepulveda, Patricio Alejandro; Büchner, Jörg; Kilian, Patrick

    2016-07-01

    It is often the case that magnetic reconnection takes place in collisionless plasmas with a current aligned guide magnetic field, such as in the Solar corona. The general characteristics of this process have been exhaustively analyzed with theory and numerical simulations, under different approximations, since some time ago. However, some consequences and properties of the secondary instabilities arising spontaneously -other than tearing instability-, and their dependence on the guide field strength, have not been completely understood yet. For this sake, we use the results of fully kinetic 2D PIC numerical simulations of guide field reconnection. By using a mean field approach for the Generalized Ohm's law that explains the balance of the reconnected electric field, we find that some of the cross-streaming and gradient driven instabilities -in the guide field case- produce an additional anomalous transport term. The latter can be interpreted as a result of the enhanced correlated electromagnetic fluctuations, leading to a slow down of the current carriers and kinetic scale turbulence. We characterize these processes on dependence on the guide field strength, and explore the causal relation with the source of free energy driving the mentioned instabilities. Finally, we show the main consequences that a fully 3D approach have on all those phenomena in contrast to the reduced 2D description.

  6. Radiative Magnetic Reconnection in Astrophysics

    CERN Document Server

    Uzdensky, Dmitri A

    2015-01-01

    I review a new rapidly growing area of high-energy plasma astrophysics --- radiative magnetic reconnection, i.e., a reconnection regime where radiation reaction influences reconnection dynamics, energetics, and nonthermal particle acceleration. This influence be may be manifested via a number of astrophysically important radiative effects, such as radiation-reaction limits on particle acceleration, radiative cooling, radiative resistivity, braking of reconnection outflows by radiation drag, radiation pressure, viscosity, and even pair creation at highest energy densities. Self-consistent inclusion of these effects in magnetic reconnection theory and modeling calls for serious modifications to our overall theoretical approach to the problem. In addition, prompt reconnection-powered radiation often represents our only observational diagnostic tool for studying remote astrophysical systems; this underscores the importance of developing predictive modeling capabilities to connect the underlying physical condition...

  7. Placing the power of real options analysis into the hands of natural resource managers - taking the next step.

    Science.gov (United States)

    Nelson, Rohan; Howden, Mark; Hayman, Peter

    2013-07-30

    This paper explores heuristic methods with potential to place the analytical power of real options analysis into the hands of natural resource managers. The complexity of real options analysis has led to patchy or ephemeral adoption even by corporate managers familiar with the financial-market origins of valuation methods. Intuitively accessible methods for estimating the value of real options have begun to evolve, but their evaluation has mostly been limited to researcher-driven applications. In this paper we work closely with Bush Heritage Australia to evaluate the potential of real options analysis to support the intuitive judgement of conservation estate managers in covenanting land with uncertain future conservation value due to climate change. The results show that modified decision trees have potential to estimate the option value of covenanting individual properties while time and ongoing research resolves their future conservation value. Complementing this, Luehrman's option space has potential to assist managers with limited budgets to increase the portfolio value of multiple properties with different conservation attributes.

  8. Placing the power of real options analysis into the hands of natural resource managers - taking the next step.

    Science.gov (United States)

    Nelson, Rohan; Howden, Mark; Hayman, Peter

    2013-07-30

    This paper explores heuristic methods with potential to place the analytical power of real options analysis into the hands of natural resource managers. The complexity of real options analysis has led to patchy or ephemeral adoption even by corporate managers familiar with the financial-market origins of valuation methods. Intuitively accessible methods for estimating the value of real options have begun to evolve, but their evaluation has mostly been limited to researcher-driven applications. In this paper we work closely with Bush Heritage Australia to evaluate the potential of real options analysis to support the intuitive judgement of conservation estate managers in covenanting land with uncertain future conservation value due to climate change. The results show that modified decision trees have potential to estimate the option value of covenanting individual properties while time and ongoing research resolves their future conservation value. Complementing this, Luehrman's option space has potential to assist managers with limited budgets to increase the portfolio value of multiple properties with different conservation attributes. PMID:23702285

  9. Acceleration during magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Beresnyak, Andrey [Los Alamos National Laboratory; Li, Hui [Los Alamos National Laboratory

    2015-07-16

    The presentation begins with colorful depictions of solar x-ray flares and references to pulsar phenomena. Plasma reconnection is complex, could be x-point dominated or turbulent, field lines could break due to either resistivity or non-ideal effects, such as electron pressure anisotropy. Electron acceleration is sometimes observed, and sometimes not. One way to study this complex problem is to have many examples of the process (reconnection) and compare them; the other way is to simplify and come to something robust. Ideal MHD (E=0) turbulence driven by magnetic energy is assumed, and the first-order acceleration is sought. It is found that dissipation in big (length >100 ion skin depths) current sheets is universal and independent on microscopic resistivity and the mean imposed field; particles are regularly accelerated while experiencing curvature drift in flows driven by magnetic tension. One example of such flow is spontaneous reconnection. This explains hot electrons with a power-law tail in solar flares, as well as ultrashort time variability in some astrophysical sources.

  10. The Investigation of Mobbing Events Taking Place at Higher Education Institutions in Turkey Considering the Reflections on Media

    Directory of Open Access Journals (Sweden)

    Çubukçu Zühal

    2015-08-01

    considering that they are published nationally, reference newspapers and belong to different publication groups. The data used in this study was taken from the archive of the three newspapers. When the archives of the newspapers was scanned, the word “mobbing” was taken as key word for the search. In qualitative researches, newspapers are considered to be public archive and used as reference documents. The data obtained was grouped depending on the newspapers which it was taken from, on the year of publication, on where they took place, on the gender of the victims and on who the sufferers are.

  11. Can Iran take Russia's place?

    NARCIS (Netherlands)

    Ihle, R.

    2016-01-01

    Agricultural exports. Sales of European farm products to Russia have collapsed. Could there be an alternative market for our agricultural goods in Iran? Demand is growing there for processed foods as well as unprocessed commodities and feeds.

  12. Dynamics of Quantized Vortices Before Reconnection

    Science.gov (United States)

    Andryushchenko, V. A.; Kondaurova, L. P.; Nemirovskii, S. K.

    2016-04-01

    The main goal of this paper is to investigate numerically the dynamics of quantized vortex loops, just before the reconnection at finite temperature, when mutual friction essentially changes the evolution of lines. Modeling is performed on the base of vortex filament method using the full Biot-Savart equation. It was discovered that the initial position of vortices and the temperature strongly affect the dependence on time of the minimum distance δ (t) between tips of two vortex loops. In particular, in some cases, the shrinking and collapse of vortex loops due to mutual friction occur earlier than the reconnection, thereby canceling the latter. However, this relationship takes a universal square-root form δ ( t) =√{( κ/2π ) ( t_{*}-t) } at distances smaller than the distances, satisfying the Schwarz reconnection criterion, when the nonlocal contribution to the Biot-Savart equation becomes about equal to the local contribution. In the "universal" stage, the nearest parts of vortices form a pyramid-like structure with angles which neither depend on the initial configuration nor on temperature.

  13. Turbulent Plasmoid Reconnection

    CERN Document Server

    Widmer, Fabien; Yokoi, Nobumitsu

    2016-01-01

    The plasmoid instability may lead to fast magnetic reconnection through long current sheets(CS). It is well known that large-Reynolds-number plasmas easily become turbulent. We address the question whether turbulence enhances the energy conversion rate of plasmoid-unstable current sheets. We carry out appropriate numerical MHD simulations, but resolving simultaneously the relevant large-scale (mean-) fields and the corresponding small-scale, turbulent, quantities by means of direct numerical simulations (DNS) is not possible. Hence we investigate the influence of small scale turbulence on large scale MHD processes by utilizing a subgrid-scale (SGS) turbulence model. We verify the applicability of our SGS model and then use it to investigate the influence of turbulence on the plasmoid instability. We start the simulations with Harris-type and force-free CS equilibria in the presence of a finite guide field in the direction perpendicular to the reconnection plane. We use the DNS results to investigate the growt...

  14. 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.

  15. Numerical study of asymmetric driven reconnection at dayside magnetopause

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A two-dimensional compressible MHD code has been used to numerically study the asymmetric driven reconnection processes in the vicinity of the magnetopause. The initial magnetic field configuration is assumed to be in a mechanical equilibrium state. The cases with identical temperatures (Tm0/Ts0=1.0) and four different ratios of magnetic field strength (Q=Bm0/Bs0=1.0, 1.5, 2.0, 2.5), and the case with Tm0/Ts0=2.0 and Q=1.5 are investigated (Bm0, Tm0 and Bs0, Ts0 are the initial magnetic strength and temperature outside the current sheet on the magnetosphere and the magnetosheath, respectively ). When the magnetic field on the magnetosheath side is set as southward, a recurrent formation of multiple magnetic bubbles with various scales occurs under the action of the inward plasma flow imposed at the left and right boundaries. In the simulation, some bubbles coalesce into a bigger one and then it is convected out of the simulation domain; the others are convected through the top boundary all alone. Thus, the plasmoid events with different scales and different time intervals take place intermittently and the impulsive features of magnetic reconnection are clearly shown. The multiple magnetic islands are all high-temperature and large-density regions in comparison with the ambient environment. The bipolar signatures or fluctuant variations of normal magnetic field component are generated by the formation of multiple magnetic islands. This result is similar to the FTEs signature.

  16. Intuitive approach to magnetic reconnection

    Science.gov (United States)

    Kulsrud, Russell M.

    2011-11-01

    Two reconnection problems are considered. The first problem concerns global physics. The plasma in the global reconnection region is in magnetostatic equilibrium. It is shown that this equilibrium can be uniquely characterized by a set of constraints. During reconnection and independently of the local reconnection physics, these constraints can be uniquely evolved from any initial state. The second problem concerns Petschek reconnection. Petschek's model for fast reconnection, which is governed by resistive MHD equations with constant resistivity is not validated by numerical simulations. Malyshkin et al. [Phys. Plasmas 12, 102920 (2005)], showed that the reason for the discrepancy is that Petschek did not employ Ohm's law throughout the local diffusion region, but only at the X-point. A derivation of Petschek reconnection, including Ohm's law throughout the entire diffusion region, removes the discrepancy. This derivation is based largely on Petschek's original 1964 calculation [in AAS-NASA Symposium on Solar Flares (National Aeronautics and Space Administration, Washington, D.C., 1964), NASA SP50, p. 425]. A useful physical interpretation of the role which Ohm's law plays in the diffusion region is presented.

  17. Colour reconnection in WW events

    CERN Document Server

    D'Hondt, J

    2003-01-01

    Preliminary results are presented for a measurement of the kappa parameter used in the JETSET SK-I model of colour reconnection in W /sup +/W/sup -/ to qq'qq' events at LEP2. An update on the investigation of colour reconnection effects in hadronic decays of W pairs, using the particle flow in DELPHI is presented. A second method is based on the observation that two different m/sub W/ estimators have different sensitivity to the parametrised colour reconnection effect. Hence the difference between them is an observable with information content about kappa. (6 refs).

  18. Spontaneous magnetic reconnection. Collisionless reconnection and its potential astrophysical relevance

    Science.gov (United States)

    Treumann, R. A.; Baumjohann, W.

    2015-10-01

    The present review concerns the relevance of collisionless reconnection in the astrophysical context. Emphasis is put on recent developments in theory obtained from collisionless numerical simulations in two and three dimensions. It is stressed that magnetic reconnection is a universal process of particular importance under collisionless conditions, when both collisional and anomalous dissipation are irrelevant. While collisional (resistive) reconnection is a slow, diffusive process, collisionless reconnection is spontaneous. On any astrophysical time scale, it is explosive. It sets on when electric current widths become comparable to the leptonic inertial length in the so-called lepton (electron/positron) "diffusion region", where leptons de-magnetise. Here, the magnetic field contacts its oppositely directed partner and annihilates. Spontaneous reconnection breaks the original magnetic symmetry, violently releases the stored free energy of the electric current, and causes plasma heating and particle acceleration. Ultimately, the released energy is provided by mechanical motion of either the two colliding magnetised plasmas that generate the current sheet or the internal turbulence cascading down to lepton-scale current filaments. Spontaneous reconnection in such extended current sheets that separate two colliding plasmas results in the generation of many reconnection sites (tearing modes) distributed over the current surface, each consisting of lepton exhausts and jets which are separated by plasmoids. Volume-filling factors of reconnection sites are estimated to be as large as {generates small-scale turbulence. Imposed external turbulence tends to temporarily increase the reconnection rate. Reconnecting ultra-relativistic current sheets decay into large numbers of magnetic flux ropes composed of chains of plasmoids and lepton exhausts. They form highly structured current surfaces, "current carpets". By including synchrotron radiation losses, one favours tearing

  19. Energy exchanges in reconnection outflows

    CERN Document Server

    Lapenta, Giovanni; Newman, Davd L; Markidis, Stefano

    2016-01-01

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

  20. Turbulent Reconnection and Its Implications

    CERN Document Server

    Lazarian, Alex; Vishniac, Ethan T; Kowal, Grzegorz

    2015-01-01

    Magnetic reconnection is a process of magnetic field topology change, which is one of the most fundamental processes in magnetized plasmas. In most astrophysical environments the Reynolds numbers are large and therefore the transition to turbulence is inevitable. This turbulence must be taken into account for any theory of magnetic reconnection, since the initially laminar configurations can transit to the turbulence state, what is demonstrated by 3D high resolution numerical simulations. We discuss ideas of how turbulence can modify reconnection with the focus on the Lazarian & Vishniac (1999) reconnection model and present numerical evidence supporting the model and demonstrate that it is closely connected to the concept of Richardson diffusion and compatible with the Lagrangian dynamics of magnetized fluids. We point out that the Generalized Ohm's Law, that accounts for turbulent motion, predicts the subdominance of the microphysical plasma effects for a realistically turbulent media. We show that on o...

  1. Particle Acceleration at Reconnecting 3D Null Points

    Science.gov (United States)

    Stanier, A.; Browning, P.; Gordovskyy, M.; Dalla, S.

    2012-12-01

    Hard X-ray observations from the RHESSI spacecraft indicate that a significant fraction of solar flare energy release is in non-thermal energetic particles. A plausible acceleration mechanism for these are the strong electric fields associated with reconnection, a process that can be particularly efficient when particles become unmagnetised near to null points. This mechanism has been well studied in 2D, at X-points within reconnecting current sheets; however, 3D reconnection models show significant qualitative differences and it is not known whether these new models are efficient for particle acceleration. We place test particles in analytic model fields (eg. Craig and Fabling 1996) and numerical solutions to the the resistive magnetohydrodynamic (MHD) equations near reconnecting 3D nulls. We compare the behaviour of these test particles with previous results for test particle acceleration in ideal MHD models (Dalla and Browning 2005). We find that the fan model is very efficient due to an increasing "guide field" that stabilises particles against ejection from the current sheet. However, the spine model, which was the most promising in the ideal case, gives weak acceleration as the reconnection electric field is localised to a narrow cylinder about the spine axis.

  2. Thin Places

    OpenAIRE

    Lockwood, Sandra Elizabeth

    2013-01-01

    This inquiry into the three great quests of the twentieth century–the South Pole, Mount Everest, and the Moon–examines our motivations to venture into these sublime, yet life-taking places. The Thin Place was once the destination of the religious pilgrim seeking transcendence in an extreme environment. In our age, the Thin Place quest has morphed into a challenge to evolve beyond the confines of our own physiology; through human ingenuity and invention, we reach places not meant to accommod...

  3. Magnetic reconnection in Saturn's magnetotail: A comprehensive magnetic field survey

    Science.gov (United States)

    Smith, A. W.; Jackman, C. M.; Thomsen, M. F.

    2016-04-01

    Reconnection within planetary magnetotails is responsible for locally energizing particles and changing the magnetic topology. Its role in terms of global magnetospheric dynamics can involve changing the mass and flux content of the magnetosphere. We have identified reconnection related events in spacecraft magnetometer data recorded during Cassini's exploration of Saturn's magnetotail. The events are identified from deflections in the north-south component of the magnetic field, significant above a background level. Data were selected to provide full tail coverage, encompassing the dawn and dusk flanks as well as the deepest midnight orbits. Overall 2094 reconnection related events were identified, with an average rate of 5.0 events per day. The majority of events occur in clusters (within 3 h of other events). We examine changes in this rate in terms of local time and latitude coverage, taking seasonal effects into account. The observed reconnection rate peaks postmidnight with more infrequent but steady loss seen on the dusk flank. We estimate the mass loss from the event catalog and find it to be insufficient to balance the input from the moon Enceladus. Several reasons for this discrepancy are discussed. The reconnection X line location appears to be highly variable, though a statistical separation between events tailward and planetward of the X line is observed at a radial distance of between 20 and 30RS downtail. The small sample size at dawn prevents comprehensive statistical comparison with the dusk flank observations in terms of flux closure.

  4. Thick escaping magnetospheric ion layer in magnetopause reconnection with MMS observations

    Science.gov (United States)

    Nagai, T.; Kitamura, N.; Hasegawa, H.; Shinohara, I.; Yokota, S.; Saito, Y.; Nakamura, R.; Giles, B. L.; Pollock, C.; Moore, T. E.; Dorelli, J. C.; Gershman, D. J.; Paterson, W. R.; Avanov, L. A.; Chandler, M. O.; Coffey, V.; Sauvaud, J. A.; Lavraud, B.; Russell, C. T.; Strangeway, R. J.; Oka, M.; Genestreti, K. J.; Burch, J. L.

    2016-06-01

    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.

  5. 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.

  6. Evidence for collisionless magnetic reconnection at Mars

    Science.gov (United States)

    Eastwood, J. P.; Brain, D. A.; Halekas, J. S.; Drake, J. F.; Phan, T. D.; Øieroset, M.; Mitchell, D. L.; Lin, R. P.; Acuña, M.

    2008-01-01

    Using data from Mars Global Surveyor (MGS) in combination with Particle-In-Cell (PIC) simulations of reconnection, we present the first direct evidence of collisionless magnetic reconnection at Mars. The evidence indicates that the spacecraft passed through the diffusion region where reconnection is initiated and observed the magnetic field signatures of differential electron and ion motion - the Hall magnetic field - that uniquely indicate the reconnection process. These are the first such in-situ reconnection observations at an astronomical body other than the Earth. Reconnection may be the source of Mars' recently discovered auroral activity and the changing boundaries of the closed regions of crustal magnetic field.

  7. Diagnostics of solar flare reconnection

    Directory of Open Access Journals (Sweden)

    M. Karlický

    2004-01-01

    Full Text Available We present new diagnostics of the solar flare reconnection, mainly based on the plasma radio emission. We propose that the high-frequency (600-2000 MHz slowly drifting pulsating structures map the flare magnetic field reconnection. These structures correspond to the radio emission from plasmoids which are formed in the extended current sheet due to tearing and coalescence processes. An increase of the frequency drift of the drifting structures is interpreted as an increase of the reconnection rate. Using this model, time scales of slowly drifting pulsating structure observed during the 12 April 2001 flare by the Trieste radiopolarimeter with high time resolution (1 ms are interpreted as a radio manifestation of electron beams accelerated in the multi-scale reconnection process. For short periods Fourier spectra of the observed structure have a power-law form with power-law indices in the 1.3-1.6 range. For comparison the 2-D MHD numerical modeling of the multi-scale reconnection is made and it is shown that Fourier spectrum of the reconnection dissipation power has also a power-law form, but with power-law index 2. Furthermore, we compute a time evolution of plasma parameters (density, magnetic field etc in the 2-D MHD model of the reconnection. Then assuming a plasma radio emission from locations, where the 'double-resonance' instability generates the upper-hybrid waves due to unstable distribution function of suprathermal electrons, we model radio spectra. Effects of the MHD turbulence are included. The resulting spectra are compared with those observed. It is found, that depending on model parameters the lace bursts and the decimetric spikes can be reproduced. Thus, it is shown that the model can be used for diagnostics of the flare reconnection process. We also point out possible radio signatures of reconnection outflow termination shocks. They are detected as type II-like herringbone structures in the 200-700 MHz frequency range. Finally

  8. Reconnection at the Heliopause

    CERN Document Server

    Nickeler, D H; Nickeler, Dieter H.; Fahr, Hans-Joerg

    2005-01-01

    In this MHD-model of the heliosphere, we assume a Parker-type flow, and a Parker-type spiral magnetic field, which is extrapolated further downstream from the termination shock to the heliopause. We raise the question whether the heliopause nose region may be leaky with respect to fields and plasmas due to nonideal plasma dynamics, implying a breakdown of the magnetic barrier. We analyse some simple scenarios to find reconnection rates and circumstances, under which the heliosphere can be an "open" or a "closed" magnetosphere. We do not pretend to offer a complete solution for the heliosphere, on the basis of nonideal MHD theory, but present a prescription to find such a solution on the basis of potential fields including the knowledge of neutral points. As an example we imitate the Parker spiral as a monopole with a superposition of homogeneous asymptotical boundary conditions. We use this toy model for x < -R where R = 100 AU is the distance of the termination shock to describe the situation in the nose ...

  9. Fractal Reconnection in Solar and Stellar Environments

    CERN Document Server

    Shibata, Kazunari

    2016-01-01

    Recent space based observations of the Sun revealed that magnetic reconnection is ubiquitous in the solar atmosphere, ranging from small scale reconnection (observed as nanoflares) to large scale one (observed as long duration flares or giant arcades). Often the magnetic reconnection events are associated with mass ejections or jets, which seem to be closely related to multiple plasmoid ejections from fractal current sheet. The bursty radio and hard X-ray emissions from flares also suggest the fractal reconnection and associated particle acceleration. We shall discuss recent observations and theories related to the plasmoid-induced-reconnection and the fractal reconnection in solar flares, and their implication to reconnection physics and particle acceleration. Recent findings of many superflares on solar type stars that has extended the applicability of the fractal reconnection model of solar flares to much a wider parameter space suitable for stellar flares are also discussed.

  10. On Lorentz invariants in relativistic magnetic reconnection

    Science.gov (United States)

    Yang, Shu-Di; Wang, Xiao-Gang

    2016-08-01

    Lorentz invariants whose nonrelativistic correspondences play important roles in magnetic reconnection are discussed in this paper. Particularly, the relativistic invariant of the magnetic reconnection rate is defined and investigated in a covariant two-fluid model. Certain Lorentz covariant representations for energy conversion and magnetic structures in reconnection processes are also investigated. Furthermore, relativistic measures for topological features of reconnection sites, particularly magnetic nulls and separatrices, are analyzed.

  11. Magnetic reconnection: from the Sweet-Parker model to stochastic plasmoid chains

    Science.gov (United States)

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

    2016-01-01

    Magnetic reconnection is the topological reconfiguration of the magnetic field in a plasma, accompanied by the violent release of energy and particle acceleration. Reconnection is as ubiquitous as plasmas themselves, with solar flares perhaps the most popular example. Other fascinating processes where reconnection plays a key role include the magnetic dynamo, geomagnetic storms and the sawtooth crash in tokamaks. Over the last few years, the theoretical understanding of magnetic reconnection in large-scale fluid systems has undergone a major paradigm shift. The steady-state model of reconnection described by the famous Sweet-Parker (SP) theory, which dominated the field for  ˜50 years, has been replaced with an essentially time-dependent, bursty picture of the reconnection layer, dominated by the continuous formation and ejection of multiple secondary islands (plasmoids). Whereas in the SP model reconnection was predicted to be slow, a major implication of this new paradigm is that reconnection in fluid systems is fast (i.e. independent of the Lundquist number), provided that the system is large enough. This conceptual shift hinges on the realization that SP-like current layers are violently unstable to the plasmoid (tearing) instability—implying, therefore, that such current sheets are super-critically unstable and thus can never form in the first place. This suggests that the formation of a current sheet and the subsequent reconnection process cannot be decoupled, as is commonly assumed. This paper provides an introductory-level overview of the recent developments in reconnection theory and simulations that led to this essentially new framework. We briefly discuss the role played by the plasmoid instability in selected applications, and describe some of the outstanding challenges that remain at the frontier of this subject. Amongst these are the analytical and numerical extension of the plasmoid instability to (i) 3D and (ii) non-magnetohydrodynamics (MHD

  12. Signatures of Interchange Reconnection: STEREO, ACE and Hinode Observations Combined

    CERN Document Server

    Baker, D; Van Driel-Gesztelyi, L; Demoulin, P; Harra, L K; Lavraud, B; Davies, J A; Optiz, A; Luhmann, J G; Sauvaud, J A; Galvin, A B

    2009-01-01

    Combining STEREO, ACE and Hinode observations has presented an opportunity to follow a filament eruption and coronal mass ejection (CME) on the 17th of October 2007 from an active region (AR) inside a coronal hole (CH) into the heliosphere. This particular combination of `open' and closed magnetic topologies provides an ideal scenario for interchange reconnection to take place. With Hinode and STEREO data we were able to identify the emergence time and type of structure seen in the in-situ data four days later. On the 21st, ACE observed in-situ the passage of an ICME with `open' magnetic topology. The magnetic field configuration of the source, a mature AR located inside an equatorial CH, has important implications for the solar and interplanetary signatures of the eruption. We interpret the formation of an `anemone' structure of the erupting AR and the passage in-situ of the ICME being disconnected at one leg, as manifested by uni-directional suprathermal electron flux in the ICME, to be a direct result of i...

  13. Reconnectable Network with Limited Resources

    Institute of Scientific and Technical Information of China (English)

    史维更

    1991-01-01

    The reachability of a strongly connected network may be destroyed after link damage.Since many networks are directed or equivalent directed,connected by directed links with the potential for reversal.Therefore the reachability can be restored by reversing the direction of links.[1] has studied this matter under unlimited resources (transmitter and receiver) condition.In this paper the reconnectability of a network with limited number of receivers and transmitters is discussed.Also a linear time algorithm is given to find a reconnected reversal for limited receivers and transmitters.

  14. Transition to whistler mediated magnetic reconnection

    Science.gov (United States)

    Mandt, M. E.; Denton, R. E.; Drake, J. F.

    1994-01-01

    The transition in the magnetic reconnection rate from the resistive magnetohydrodynamic (MHD) regime where the Alfen wave controls reconnection to a regime in which the ions become unmagnetized and the whistler wave mediates reconnection is explored with 2-D hybrid simulations. In the whistler regime the electrons carry the currents while the ions provide a neutralizing background. A simple physical picture is presented illustrating the role of the whistler mediated reconnection is calculated analytically. The development of an out-of-plane component of the magnetic field is an observable signature of whistler driven reconnection.

  15. Reconnection in Solar Flares: Outstanding Questions

    Indian Academy of Sciences (India)

    Hiroaki Isobe; Kazunari Shibata

    2009-06-01

    Space observations of solar flares such as those from Yohkoh, SOHO,TRACE, and RHESSI have revealed a lot of observational evidence of magnetic reconnection in solar flares: cusp-shaped arcades, reconnection inflows, plasmoids, etc. Thus it has been established, at least phenomenologically, that magnetic reconnection does occur in solar flares. However, a number of fundamental questions and puzzles still remain in the physics of reconnection in solar flares. In this paper, we discuss the recent progresses and future prospects in the study of magnetic reconnection in solar flares from both theoretical and observational points of view.

  16. Magnetopause reconnection and interlinked flux tubes

    Directory of Open Access Journals (Sweden)

    F. R. Cardoso

    2013-10-01

    Full Text Available Magnetic reconnection can be a continuous or a transient process. Global magnetohydrodynamics (MHD simulations are important tools to understand the relevant magnetic reconnection mechanisms and the resulting magnetic structures. We have studied magnetopause reconnection using a global 3-D MHD simulation in which the interplanetary magnetic field (IMF has been set to large positive By and large negative Bz components, i.e., a south-duskward direction. Flux tubes have been observed even during these constant solar wind conditions. We have focused on the interlinked flux tubes event resulting from time-dependent, patchy and multiple reconnection. At the event onset, two reconnection modes seem to occur simultaneously: a time-dependent, patchy and multiple reconnection for the subsolar region; and, a steady and large-scale reconnection for the regions far from the subsolar site.

  17. Colour reconnection at LEP2

    CERN Document Server

    Abreu, P

    2002-01-01

    The preliminary results on the search of colour reconnection effects (CR) from the four experiments at LEP, ALEPH, DELPHI, L3 and OPAL, are reviewed. Extreme models are excluded by studies of standard variables, and on going studies of a method first suggested by L3, the particle flow method (D. Duchesneau, (2001)), are yet inconclusive. (22 refs).

  18. Reconnection in thin current sheets

    Science.gov (United States)

    Tenerani, Anna; Velli, Marco; Pucci, Fulvia; Rappazzo, A. F.

    2016-05-01

    It has been widely believed that reconnection is the underlying mechanism of many explosive processes observed both in nature and laboratory, but the question of reconnection speed and initial trigger have remained mysterious. How is fast magnetic energy release triggered in high Lundquist (S) and Reynolds (R) number plasmas?It has been shown that a tearing mode instability can grow on an ideal timescale, i.e., independent from the the Lundquist number, once the current sheet thickness becomes thin enough, or rather the inverse aspect ratio a/L reaches a scale a/L~S-1/3. As such, the latter provides a natural, critical threshold for current sheets that can be formed in nature before they disrupt in a few Alfvén time units. Here we discuss the transition to fast reconnection extended to simple viscous and kinetic models and we propose a possible scenario for the transition to explosive reconnection in high-Lundquist number plasmas, that we support with fully nonlinear numerical MHD simulations of a collapsing current sheet.

  19. NUMERICAL STUDIES OF WEAKLY STOCHASTIC MAGNETIC RECONNECTION

    Directory of Open Access Journals (Sweden)

    G. Kowal

    2009-01-01

    Full Text Available We study the e ects of turbulence on magnetic reconnection using three-dimensional numerical simulations.This is the rst attempt to test the model of fast magnetic reconnection proposed by Lazarian & Vishniac (1999, which assumes the presence of weak, small-scale magnetic eld structure near the current sheet. This a ects the rate of reconnection by reducing the transverse scale for reconnection ows and by allowing many independent ux reconnection events to occur simultaneously. We performed a number of simulations to test the dependencies of the reconnection speed, de ned as the ratio of the in ow velocity to the Alfv n speed, on the turbulence power, the injection scale and resistivity. Our results show that turbulence signi cantly a ects the topology of magnetic eld near the di usion region and increases the thickness of the out ow region. We con rm the predictions of the Lazarian & Vishniac model. In particular, we report the growth of the reconnection speed proportional to V 2 l , where Vl is the amplitude of velocity at the injection scale. It depends on the injection scale linj as (linj=L2=3, where L is the size of the system, which is somewhat faster but still roughly consistent with the theoretical expectations. We also show that for 3D reconnection the Ohmic resistivity is important in the local reconnection events only, and the global reconnection rate in the presence of turbulence does not depend on it.

  20. Particle acceleration at a reconnecting magnetic separator

    CERN Document Server

    Threlfall, J; Parnell, C E; Oskoui, S Eradat

    2014-01-01

    While the exact acceleration mechanism of energetic particles during solar flares is (as yet) unknown, magnetic reconnection plays a key role both in the release of stored magnetic energy of the solar corona and the magnetic restructuring during a flare. Recent work has shown that special field lines, called separators, are common sites of reconnection in 3D numerical experiments. To date, 3D separator reconnection sites have received little attention as particle accelerators. We investigate the effectiveness of separator reconnection as a particle acceleration mechanism for electrons and protons. We study the particle acceleration using a relativistic guiding-centre particle code in a time-dependent kinematic model of magnetic reconnection at a separator. The effect upon particle behaviour of initial position, pitch angle and initial kinetic energy are examined in detail, both for specific (single) particle examples and for large distributions of initial conditions. The separator reconnection model contains ...

  1. Properties of GRB Lightcurves from Magnetic Reconnection

    CERN Document Server

    Beniamini, Paz

    2015-01-01

    The energy dissipation mechanism within Gamma ray bursts' (GRBs) ultra-relativistic outflows that drive the prompt $\\gamma$-ray emission remains uncertain. Two leading candidates are internal shocks and magnetic reconnection. While the emission from internal shocks has been extensively studied, that from reconnection still has few quantitative predictions. We study the prompt GRB emission from magnetic reconnection and compare its expected temporal and spectral properties to observations. The main difference from internal shocks is that for magnetic reconnection one expects relativistic bulk motions with a Lorentz factor of $\\Gamma'\\gtrsim$a few in the mean rest frame of the outflow - the comoving frame. We consider a thin spherical shell (or reconnection layer) expanding at a bulk Lorentz factor $\\Gamma\\gg 1$ in which the emitting material moves with $\\Gamma'$ in the comoving frame along this layer in two anti-parallel directions (e.g. of the reconnecting field lines). The resulting relativistic beaming of t...

  2. Colour Reconnection - Models and Tests

    CERN Document Server

    Christiansen, Jesper R

    2015-01-01

    Recent progress on colour reconnection within the Pythia framework is presented. A new model is introduced, based on the SU(3) structure of QCD and a minimization of the potential string energy. The inclusion of the epsilon structure of SU(3) gives a new baryon production mechanism and makes it possible simultaneously to describe hyperon production at both $e^+e^-$ and pp colliders. Finally, predictions for $e^+e^-$ colliders, both past and potential future ones, are presented.

  3. Particle acceleration at reconnecting separator current layers

    OpenAIRE

    Threlfall, J.; E. H. Stevenson, J.; E. Parnell, C.; Neukirch, T.

    2015-01-01

    The aim of this work is to investigate and characterise particle behaviour in a 3D magnetohydrodynamic (MHD) model of a reconnecting magnetic separator. We use a relativistic guiding-centre test-particle code to investigate electron and proton acceleration in snapshots from 3D MHD separator reconnection experiments, and compare the results with findings from an analytical separator reconnection model studied in a previous investigation. The behaviour and acceleration of large distributions of...

  4. Identification of Colour Reconnection using Factorial Correlator

    Institute of Scientific and Technical Information of China (English)

    FU Jing-Hua; LIU Lian-Shou

    2000-01-01

    A new signal is proposed for the colour reconnection in the hadronic decay of W+ W- in e+e- collisions. Using Pythia Monte Carlo it is shown that factorial correlators for W+ and W- without colour reconnection are almost identical to unity, while those for the cases with colour reconnection fall down approximately linearly in the log log plot. This signal, being based on the factorial correlator, is more sensitive than the ones using only averaged quantities.

  5. Impulsive nature in collisional driven reconnection

    International Nuclear Information System (INIS)

    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)

  6. Collisionless Reconnection and Electron Demagnetization

    Science.gov (United States)

    Scudder, J. D.

    Observable, dimensionless properties of the electron diffusion region of collisionless magnetic reconnection are motivated and benchmarked in two and three dimensional Particle In Cell (PIC) simulations as appropriate for measurements with present state of the art spacecraft. The dimensionless quantities of this paper invariably trace their origin to breaking the magnetization of the thermal electrons. Several observable proxies are also motivated for the rate of frozen flux violation and a parameter \\varLambda _{\\varPhi } that when greater than unity is associated with close proximity to the analogue of the saddle point region of 2D reconnection usually called the electron diffusion region. Analogous regions to the electron diffusion region of 2D reconnection with \\varLambda _{\\varPhi } > 1 have been identified in 3D simulations. 10-20 disjoint diffusion regions are identified and the geometrical patterns of their locations illustrated. First examples of associations between local observables based on electron demagnetization and global diagnostics (like squashing) are also presented. A by product of these studies is the development of a single spacecraft determinations of gradient scales in the plasma.

  7. Dissipation in Relativistic Pair-Plasma Reconnection

    Science.gov (United States)

    Hesse, Michael; Zenitani, Seiji

    2007-01-01

    We present an investigation of the relativistic dissipation in magnetic reconnection. The investigated system consists of an electron-positron plasma. A relativistic generalization of Ohm's law is derived. We analyze a set of numerical simulations, composed of runs with and without guide magnetic field, and of runs with different species temperatures. The calculations indicate that the thermal inertia-based dissipation process survives in relativistic plasmas. For anti-parallel reconnection, it is found that the pressure tensor divergence remains the sole contributor to the reconnection electric field, whereas relativistic guide field reconnection exhibits a similarly important role of the bulk inertia terms.

  8. Does Non-Occurrence of Meiyu Take Place in Yangtze-Huaihe Basins during Summer of 2009?%2009年是空梅吗?

    Institute of Scientific and Technical Information of China (English)

    梁萍; 丁一汇

    2011-01-01

    Meiyu precipitation in Yangtze-Huaihe basins is abnormal in summer of 2009. During usual Meiyu period (i. e. from mid June to early July), Meiyu precipitation is too less than climatology to come up to the standard of occurrence of Meiyu. And some people view it as empty Meiyu or untypical Meiyu. But during the period from late July to the beginning of August, Meiyu belt retreats to Yangtze-Huaihe basins again. The so-called 'secondary Meiyu' or 'late Meiyu' has so abundant precipitation that standard of occurrence of Meiyu is satisfied. Why does Meiyu in 2009 exhibit characteristics of former weak and later severe precipitation? To answer the question, largescale circulation background and mechanism of abnormal Meiyu from the angle of interseasonal oscillation are discussed. The results indicate that: (1) Anomalous Asian summer monsoon provides largescale condition for the occurrence of Meiyu during the end of June to the beginning of July and from late July to the beginning of August, respectively. The former Meiyu which takes place during the period of distinctively weak Asian summer monsoon has short duration and low rainfall; while the latter occurred after the remarkable strengthening of Asian summer monsoon and meanwhile the time period usually with little rainfall, has long duration and severe precipitation. (2) Anomalously strong Northeast Cold Vortex with long duration blocks the northward advance of west Pacific subtropical high, which brings about late beginning of the first Meiyu period. And weak influences of moisture transport by summer monsoon attributes much to the lack of precipitation during the first Meiyu period. During the second Meiyu period, due to the southward retreat of the west Pacific subtropical high under the influence of strengthening of Northeast Cold Vortex, anomalous moisture transport from the west Pacific converges with those from North China in Yangtze-Huaihe basins, which exerts important effects on anomalously sustainable

  9. Designated Places

    Data.gov (United States)

    California Department of Resources — Census 2000 Place Names provides a seamless statewide GIS layer of places, including census designated places (CDP), consolidated cities, and incorporated places,...

  10. Spontaneous reconnection at a separator current layer. I. Nature of the reconnection

    CERN Document Server

    Stevenson, Julie E H

    2015-01-01

    Magnetic separators, which lie on the boundary between four topologically-distinct flux domains, are prime locations in three-dimensional magnetic fields for reconnection. Little is known about the details of separator reconnection and so the aim of this paper, which is the first of two, is to study the properties of magnetic reconnection at a single separator. Three-dimensional, resistive magnetohydrodynamic numerical experiments are run to study separator reconnection starting from a magnetohydrostatic equilibrium which contains a twisted current layer along a single separator linking a pair of opposite-polarity null points. The resulting reconnection occurs in two phases. The first is short involving rapid-reconnection in which the current at the separator is reduced by a factor of around 2.3. Most ($75\\%$) of the magnetic energy is converted during this phase, via Ohmic dissipation, directly into internal energy, with just $0.1\\%$ going into kinetic energy. During this phase the reconnection occurs along ...

  11. Hyper-resistive forced magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Vekstein, G., E-mail: g.vekstein@manchester.ac.uk [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom)

    2016-02-15

    We study Taylor's model of forced magnetic reconnection mediated by plasma hyper-resistivity. This includes both linear and nonlinear regimes of the process. It is shown how the onset of plasmoid instability occurs in the strongly nonlinear regime of forced reconnection.

  12. Pseudo-reconnection in MHD numerical simulation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A class of pseudo-reconnections caused by a shifted mesh in magnetohydrodynamics (MHD) simulations is reported. In terms of this mesh system, some non-physical results may be obtained in certain circumstances, e.g. magnetic reconnection occurs without resistivity. After comparison, another kind of mesh is strongly recommended.

  13. Magnetic Reconnection in a Laboratory Plasma

    Science.gov (United States)

    Ji, Hantao

    2006-04-01

    Magnetic reconnection plays an important role in determining the evolution of magnetic topology in relaxation processes in laboratory plasmas, magnetospheric substorms, solar flares, and more distant astrophysical plasmas. Often, magnetic reconnection is invoked to explain the observed rapid release of magnetic energy. A central question concerns why the observed reconnection rates are much faster than predictions made by classical theories, such as the Sweet-Parker model based on MHD with classical Spitzer resistivity. In general, the reconnection process is determined by both local plasma dynamics in the diffusion region as well as by global boundary conditions. Presently, there are two prevailing theories to explain the mechanism of local dissipation enhancement and fast reconnection, based on the generalized Ohm's law. One is anomalous resistivity due to wave particle interactions and the other is the Hall effect originated from separation of electron motion from ions. In this talk, I would like to present recent results on these fundamental issues of reconnection from a well- controlled laboratory experiment, Magnetic Reconnection Experiment (MRX). Both electromagnetic turbulence and out-of- plane quadrupole magnetic field (a hallmark of the Hall effect) have been observed during fast reconnection process, which is also strongly affected by boundary conditions. Physics insights based on these observations as well as their comparisons and implications to space, solar and astrophysical plasmas will be discussed.

  14. 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.

  15. Relativistic Magnetic Reconnection in the Laboratory

    CERN Document Server

    Raymond, A; McKelvey, A; Zulick, C; Alexander, N; Batson, T; Bhattacharjee, A; Campbell, P; Chen, H; Chvykov, V; Del Rio, E; Fitzsimmons, P; Fox, W; Hou, B; Maksimchuk, A; Mileham, C; Nees, J; Nilson, P M; Stoeckl, C; Thomas, A G R; Wei, M S; Yanovsky, V; Willingale, L; Krushelnick, K

    2016-01-01

    Magnetic reconnection is a fundamental plasma process involving an exchange of magnetic energy to plasma kinetic energy through changes in the magnetic field topology. In many astrophysical plasmas magnetic reconnection plays a key role in the release of large amounts of energy \\cite{hoshino1}, although making direct measurements is challenging in the case of high-energy astrophysical systems such as pulsar wind emissions \\cite{lyubarsky1}, gamma-ray bursts \\cite{thompson1}, and jets from active galactic nuclei \\cite{liu1}. Therefore, laboratory studies of magnetic reconnection provide an important platform for testing theories and characterising different regimes. Here we present experimental measurements as well as numerical modeling of relativistic magnetic reconnection driven by short-pulse, high-intensity lasers that produce relativistic plasma along with extremely strong magnetic fields. Evidence of magnetic reconnection was identified by the plasma's X-ray emission patterns, changes to the electron ene...

  16. 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.

  17. NS [Nuclear Safety] update. Current safety and security activities and developments taking place in the Department of Nuclear Safety and Security, Issue no. 6, March 2008

    International Nuclear Information System (INIS)

    The current issue presents information about the following activities: 1) International Conference on Illicit Nuclear Trafficking which took place in November 2007 in Edinburgh. The principal aim of the conference was to examine the threat and context of illicit nuclear trafficking of radioactive material, specifically, what is being done to combat such trafficking and where more needs to be done. The conference was also to consider how the obligations and commitments of the legally binding and non-binding international instruments could be and are being implemented by various States. 2) INSAG Message on Nuclear Safety Infrastructure in which the INSAG Chairman Richard Meserve addressed nuclear safety in the current context and various issues that warrant special attention. 3) approved for publication the Safety Requirements publication on Safety of Nuclear Fuel Cycle Facilities. 4) The Asian Nuclear Safety Network (ANSN)

  18. Effects of proton irradiation on a gas phase in which condensation takes place. I Negative Mg-26 anomalies and Al-26. [applied to solar and meteoritic composition

    Science.gov (United States)

    Heymann, D.; Dziczkaniec, M.; Walker, A.; Huss, G.; Morgan, J. A.

    1978-01-01

    In the present paper, isotopic effects in magnesium generated in a proton-irradiated gas phase are examined, taking only (p,n), (p,d), and (p, alpha) reactions in magnesium, aluminum, and silicon into consideration. In the presence of proton radiation, the three elements are 'removed' from the gas phase by condensation. It is required that a value of Al-26/Al-27 greater than 6 times 10 to the -5th must be reached, consistent with the value deduced by Lee Papanastassiou, and Wasserburg (1976) from their studies of the Allende meteorite. The calculations show that fast aluminum condensation reduces the required proton fluence substantially, that a significant fraction of aluminum remains uncondensed when the above value of the Al-26/Al-27 ratio is reached, that a detectable MG-24 excess is very likely to occur, that detectable negative MG-28 anomalies can be generated, and that proton fluxes and irradiation times can be varied simultaneously, and over a wide range of values, without significant changes in the required proton fluence.

  19. Magnetic reconnection as an element of turbulence

    Directory of Open Access Journals (Sweden)

    S. Servidio

    2011-10-01

    Full Text Available In this work, recent advances on the study of reconnection in turbulence are reviewed. Using direct numerical simulations of decaying incompressible two-dimensional magnetohydrodynamics (MHD, it was found that in fully developed turbulence complex processes of reconnection locally occur (Servidio et al., 2009, 2010a. In this complex scenario, reconnection is spontaneous but locally driven by the fields, with the boundary conditions provided by the turbulence. Matching classical turbulence analysis with a generalized Sweet-Parker theory, the statistical features of these multiple-reconnection events have been identified. A discussion on the accuracy of our algorithms is provided, highlighting the necessity of adequate spatial resolution. Applications to the study of solar wind discontinuities are reviewed, comparing simulations to spacecraft observations. New results are shown, studying the time evolution of these local reconnection events. A preliminary study on the comparison between MHD and Hall MHD is reported. Our new approach to the study of reconnection as an element of turbulence has broad applications to space plasmas, shedding a new light on the study of magnetic reconnection in nature.

  20. Magnetic reconnection in lower solar atmosphere

    Institute of Scientific and Technical Information of China (English)

    汪景琇

    1995-01-01

    Observations of vector magnetic field have provided the decisive constraint on the magnetic topology of solar active regions, thus offering an observational basis to identify various physical processes. Based on both magnetic field observations and theoretical discussions, it has been inferred that the magnetic flux cancellation, discovered from the line-of-sight magnetograms, reflects the interaction between magnetic loop systems and is most likely the slow magnetic reconnection in the lower solar atmosphere. This type of reconnections may affect the magnetic activities in the higher atmosphere by the way of transporting the magnetic energy and helicity and sometimes may cause fast reconnection in the corona, providing the necessary energy in solar flares.

  1. Kinetic Structure of the Reconnection Diffusion Region

    Science.gov (United States)

    Khotyaintsev, Yuri

    2016-04-01

    We present high-resolution multi-spacecraft observations of electromagnetic fields and particle distributions by Magnetospheric Multiscale (MMS) mission throughout a reconnection layer at the sub-solar magnetopause. We study which terms in the generalized Ohm's law balance the observed electric field throughout the region. We also study waves and particle distribution functions in order to identify kinetic boundaries created due to acceleration and trapping of electrons and ions as well as mixing of electron populations from different sides of the reconnecting layer. We discuss the interplay between particles, waves, and DC electric and magnetic fields, which clearly demonstrates kinetic and multi-scale nature of the reconnection diffusion region.

  2. Spontaneous reconnection at a separator current layer : I. Nature of the reconnection

    OpenAIRE

    E. H. Stevenson, Julie; E. Parnell, Clare

    2016-01-01

    Magnetic separators, which lie on the boundary between four topologically-distinct flux domains, are prime locations in three-dimensional magnetic fields for reconnection, especially in the magnetosphere between the planetary and interplanetary magnetic field and also in the solar atmosphere. Little is known about the details of separator reconnection and so the aim of this paper, which is the first of two, is to study the properties of magnetic reconnection at a single separator. Three-dimen...

  3. Dependence of anomalous resistivity on bulk drift velocity of electrons in the reconnecting current sheets in solar flares

    Institute of Scientific and Technical Information of China (English)

    Gui-Ping Wu; Guang-Li Huang; Hai-Sheng Ji

    2010-01-01

    Anomalous resistivity is critical for triggering fast magnetic reconnection in the nearly collisionless coronal plasma.Its nonlinear dependence on bulk drift velocity is usually assumed in MHD simulations.However,the mechanism for the production of anomalous resistivity and its evolution is still an open question.We numerically solved the one dimension Vlasov equation with the typical solar coronal parameters and realistic mass ratios to infer the relationship between anomalous resistivity and bulk drift velocity of electrons in the reconnecting current sheets as well as its nonlinear characteristics.Our principal findings are summarized as follows: 1)the relationship between the anomalous resistivity and bulk drift velocity of electrons relative to ions may be described as ηmax = 0.03724(vd/ve)5.702 Ω m for vd/ve in the range of 1.4-2.0 and ηmax = 0.8746(vd/ve)1.284 Ωm for vd/ve in the range of 2.5-4.5; 2)if drift velocity is just slightly larger than the threshold of ion-acoustic instability,the anomalous resistivity due to the wave-particle interactions is enhanced by about five orders as compared with classic resistivity due to Coulomb collisions.With the increase of drift velocity from 1.4ve to 4.5ve,the anomalous resistivity continues to increase 100 times; 3)in the rise phase of unstable waves,the anomalous resistivity has the same order as the one estimated from quasi-linear theory; after saturation of unstable waves,the anomalous resistivity decreases at least about one order as compared with its peak value; 4)considering that the final velocity of electrons ejected out of the reconnecting current sheet(RCS)decreases with the distance from the neutral point in the neutral plane,the anomalous resistivity decreases with the distance from the neutral point,which is favorable for the Petschek-like reconnection to take place.

  4. Interchange reconnection in a turbulent Corona

    CERN Document Server

    Rappazzo, A F; Ruffolo, D; Servidio, S; Velli, M

    2012-01-01

    Magnetic reconnection at the interface between coronal holes and loops, so-called interchange reconnection, can release the hotter, denser plasma from magnetically confined regions into the heliosphere, contributing to the formation of the highly variable slow solar wind. The interchange process is often thought to develop at the apex of streamers or pseudo-streamers, near Y and X-type neutral points, but slow streams with loop composition have been recently observed along fanlike open field lines adjacent to closed regions, far from the apex. However, coronal heating models, with magnetic field lines shuffled by convective motions, show that reconnection can occur continuously in unipolar magnetic field regions with no neutral points: photospheric motions induce a magnetohydrodynamic turbulent cascade in the coronal field that creates the necessary small scales, where a sheared magnetic field component orthogonal to the strong axial field is created locally and can reconnect. We propose that a similar mechan...

  5. Magnetic Reconnection in the Earth's Magnetosphere

    Science.gov (United States)

    Tsurutani, B. T.; Lakhina, G. S.

    1997-01-01

    The process of magnetic reconnection plays an important role during the interaction of the solar wind with the Earth's magnetosphere which leads to the exchange of mass, momentum, and energy between these two highly conducting plasmas.

  6. Resistive Magnetohydrodynamic Simulations of Relativistic Magnetic Reconnection

    Science.gov (United States)

    Zenitani, Seiji; Hesse, Michael; Klimas, Alex

    2010-01-01

    Resistive relativistic magnetohydrodynamic (RRMHD) simulations are applied to investigate the system evolution of relativistic magnetic reconnection. A time-split Harten-Lan-van Leer method is employed. Under a localized resistivity, the system exhibits a fast reconnection jet with an Alfv enic Lorentz factor inside a narrow Petschek-type exhaust. Various shock structures are resolved in and around the plasmoid such as the post-plasmoid vertical shocks and the "diamond-chain" structure due to multiple shock reflections. Under a uniform resistivity, Sweet-Parker-type reconnection slowly evolves. Under a current-dependent resistivity, plasmoids are repeatedly formed in an elongated current sheet. It is concluded that the resistivity model is of critical importance for RRMHD modeling of relativistic magnetic reconnection.

  7. Asymmetric Magnetic Reconnection in Solar Flare and Coronal Mass Ejection Current Sheets

    CERN Document Server

    Murphy, N A; Pope, C L; Raymond, J C; Winter, H D; Reeves, K K; Seaton, D B; van Ballegooijen, A A; Lin, J

    2012-01-01

    We present two-dimensional resistive magnetohydrodynamic simulations of line-tied asymmetric magnetic reconnection in the context of solar flare and coronal mass ejection current sheets. The reconnection process is made asymmetric along the inflow direction by allowing the initial upstream magnetic field strengths and densities to differ, and along the outflow direction by placing the initial perturbation near a conducting wall boundary that represents the photosphere. When the upstream magnetic fields are asymmetric, the post-flare loop structure is distorted into a characteristic skewed candle flame shape. The simulations can thus be used to provide constraints on the reconnection asymmetry in post-flare loops. More hard X-ray emission is expected to occur at the footpoint on the weak magnetic field side because energetic particles are more likely to escape the magnetic mirror. The footpoint on the weak magnetic field side is predicted to move more quickly because of the requirement in two dimensions that e...

  8. In-situ evidence of electron energization in the electron diffusion region of magnetotail reconnection

    CERN Document Server

    Oka, Mitsuo; Oieroset, Marit; Angelopoulos, Vassilis

    2016-01-01

    Magnetic reconnection is an explosive energy-release process in laboratory, space and astrophysical plasmas. While magnetic fields can `break' and `reconnect' in a very small region called the electron diffusion region (EDR), there have been conflicting theories as to whether this region can be a place of rapid energization of plasmas. Here we report a fortuitous encounter of the EDR by THEMIS in the Earth's magnetotail where significant heating and demagnetization of electrons were observed. Additional energization was observed on both sides (immediate upstream and downstream) of the EDR, leading to a total of more than an order of magnitude energization across this region. The results demonstrate that, despite its minuscule size, the EDR does indeed contribute to the overall process of electron energization via magnetic reconnection.

  9. Turbulent magnetic fluctuations in laboratory reconnection

    Science.gov (United States)

    Von Stechow, Adrian; Grulke, Olaf; Klinger, Thomas

    2016-07-01

    The role of fluctuations and turbulence is an important question in astrophysics. While direct observations in space are rare and difficult dedicated laboratory experiments provide a versatile environment for the investigation of magnetic reconnection due to their good diagnostic access and wide range of accessible plasma parameters. As such, they also provide an ideal chance for the validation of space plasma reconnection theories and numerical simulation results. In particular, we studied magnetic fluctuations within reconnecting current sheets for various reconnection parameters such as the reconnection rate, guide field, as well as plasma density and temperature. These fluctuations have been previously interpreted as signatures of current sheet plasma instabilities in space and laboratory systems. Especially in low collisionality plasmas these may provide a source of anomalous resistivity and thereby contribute a significant fraction of the reconnection rate. We present fluctuation measurements from two complementary reconnection experiments and compare them to numerical simulation results. VINETA.II (Greifswald, Germany) is a cylindrical, high guide field reconnection experiment with an open field line geometry. The reconnecting current sheet has a three-dimensional structure that is predominantly set by the magnetic pitch angle which results from the superposition of the guide field and the in-plane reconnecting field. Within this current sheet, high frequency magnetic fluctuations are observed that correlate well with the local current density and show a power law spectrum with a spectral break at the lower hybrid frequency. Their correlation lengths are found to be extremely short, but propagation is nonetheless observed with high phase velocities that match the Whistler dispersion. To date, the experiment has been run with an external driving field at frequencies higher than the ion cyclotron frequency f_{ci}, which implies that the EMHD framework applies

  10. Recent advances in collisionless magnetic reconnection

    Science.gov (United States)

    Porcelli, F.; Borgogno, D.; Califano, F.; Grasso, D.; Ottaviani, M.; Pegoraro, F.

    2002-12-01

    One of the recurring problems in magnetic reconnection is the identification of the appropriate generalized Ohm's law. In weakly collisional plasmas with a strong magnetic guide field component, a fluid model may be adopted, where electron inertia and the electron pressure gradient play important roles. In the absence of collisions, electron inertia provides the mechanism for magnetic field-line breaking. Electron compressibility alters significantly the structure of the reconnection region and allows for faster reconnection rates, which are consistent with the fast relaxation times of sawtooth oscillations in tokamak plasmas. The Hall term may also become important when the guide field is weak. The very possibility of nonlinear, irreversible magnetic reconnection in the absence of dissipation is addressed. We show that in a collisionless plasma, magnetic islands can grow and reach a saturated state in a coarse-grained sense. Magnetic energy is transferred to kinetic energy in smaller and smaller spatial scale lengths through a phase mixing process. The same model is then applied to the interpretation of driven reconnection events in the vicinity of a magnetic X-line observed in the VTF experiment at MIT. The reconnection is driven by externally induced plasma flows in a background magnetic configuration that has a hyperbolic null in the reconnection plane and a magnetic guide field component perpendicular to that plane. In the limit where the guide field is strong, assuming the external drive to be sufficiently weak for a linear approximation to hold, a dynamic evolution of the system is obtained which does not reach a stationary state. The reconnection process develops in two phases: an initial phase, whose characteristic rate is a fraction of the Alfvén frequency, and a later one, whose rate is determined by the electron collision frequency.

  11. Magnetic Reconnection in Interplanetary Coronal Mass Ejections

    Science.gov (United States)

    Fermo, R. L.; Opher, M.; Drake, J. F.

    2014-12-01

    Magnetic reconnection is a ubiquitous phenomenon in many varied space and astrophysical plasmas, and as such plays an important role in the dynamics of interplanetary coronal mass ejections (ICMEs). It is widely regarded that reconnection is instrumental in the formation and ejection of the initial CME flux rope, but reconnection also continues to affect the dynamics as it propagates through the interplanetary medium. For example, reconnection on the leading edge of the ICME, by which it interacts with the interplanetary medium, leads to flux erosion. However, recent in situ observations by Gosling et al. found signatures of reconnection exhausts in the interior. In light of this data, we consider the stability properties of systems with this flux rope geometry with regard to their minimum energy Taylor state. Variations from this state will result in the magnetic field relaxing back towards the minimum energy state, subject to the constraints that the toroidal flux and magnetic helicity remain invariant. In reversed field pinches, this relaxation is mediated by reconnection in the interior of the system, as has been shown theoretically and experimentally. By treating the ICME flux rope in a similar fashion, we show analytically that the the elongation of the flux tube cross section in the latitudinal direction will result in a departure from the Taylor state. The resulting relaxation of the magnetic field causes reconnection to commence in the interior of the ICME, in agreement with the observations of Gosling et al. We present MHD simulations in which reconnection initiates at a number of rational surfaces, and ultimately produces a stochastic magnetic field. If the time scales for this process are shorter than the propagation time to 1 AU, this result explains why many ICME flux ropes no longer exhibit the smooth, helical flux structure characteristic of a magnetic cloud.

  12. Reconnection in a slow Coronal Mass Ejection

    Directory of Open Access Journals (Sweden)

    G. Poletto

    2008-10-01

    Full Text Available This paper aims at studying reconnection occurring in the aftermath of the 28 May 2004, CME, first imaged by the LASCO (Large Angle and Spectrometric Coronagraph C2 at 11:06 UT. The CME was observed in White Light and UV radiation: images acquired by the LASCO C2 and C3 coronagraphs and spectra acquired by UVCS (Ultraviolet Coronagraph Spectrometer allowed us to identify the level at which field lines, stretched outwards by the CME ejection, reconnect below the CME bubble. As the CME propagates outwards, reconnection occurs at increasingly higher levels. The process goes on at a low pace for several hours: here we give the profile of the reconnection rate vs. heliocentric distance over a time interval of ≈14 h after the CME onset, extending estimates of the reconnection rate to larger distances than previously inferred by other authors. The reconnection rate appears to decrease with time/altitude. We also calculate upper and lower limits to the density in the diffusion region between 4 and 7 R and conclude by comparing estimates of the classical and anomalous resistivity in the diffusion region with the value inferred from the data. The latter turns out to be ≥5 order of magnitudes larger than predicted by classical or anomalous theories, pointing to the need of identifying the process responsible for the observed value.

  13. Collisionless magnetic reconnection in a plasmoid chain

    Directory of Open Access Journals (Sweden)

    S. Markidis

    2012-02-01

    Full Text Available 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.

  14. Multiscale Modeling of Solar Coronal Magnetic Reconnection

    Science.gov (United States)

    Antiochos, Spiro K.; Karpen, Judith T.; DeVore, C. Richard

    2010-01-01

    Magnetic reconnection is widely believed to be the primary process by which the magnetic field releases energy to plasma in the Sun's corona. For example, in the breakout model for the initiation of coronal mass ejections/eruptive flares, reconnection is responsible for the catastrophic destabilizing of magnetic force balance in the corona, leading to explosive energy release. A critical requirement for the reconnection is that it have a "switch-on' nature in that the reconnection stays off until a large store of magnetic free energy has built up, and then it turn on abruptly and stay on until most of this free energy has been released. We discuss the implications of this requirement for reconnection in the context of the breakout model for CMEs/flares. We argue that it imposes stringent constraints on the properties of the flux breaking mechanism, which is expected to operate in the corona on kinetic scales. We present numerical simulations demonstrating how the reconnection and the eruption depend on the effective resistivity, i.e., the effective Lundquist number, and propose a model for incorporating kinetic flux-breaking mechanisms into MHO calculation of CMEs/flares.

  15. Observations and models of magnetic reconnection

    Science.gov (United States)

    Barta, Miroslav

    2015-08-01

    Magnetic reconnection is now almost unanimously considered to be a key plasma process for energy release in solar and stellar flares. Recent decade have seen rapid development in the theory, simulations and searching for observational evidences of magnetic reconnection being in action in the core of flares. Modern modeling approach involves many realistic aspects of magnetic reconnection such as intrinsically 3D nature of the process and, namely, its highly dynamic character connected with violent formation of plasmoids at many scales. The cascade of plasmoid formation represents natural process of fast, turbulent energy transfer to the kinetic dissipation scale. This concept, revealed by numerical simulations, has found its ground in the theory of (ideal) plasmoid instability in current layers with high aspect ratio. The plasmoid dominated reconnection regime is capable to account for many puzzling dilemmas in the flare physics ranging from the observation-demanded energy release rate vs. standard reconnection-regime timescales, observed organized large-scale structures vs. signatures of fragmented energy release etc. The talk aims at reviewing recent theoretical and simulation development in this direction and observational support for the concept of plasmoid-driven reconnection cascade namely in solar flares.

  16. Reconnection in a Weakly Stochastic Field

    CERN Document Server

    Lazarian, A

    1999-01-01

    We examine the effect of weak, small scale magnetic field structure on the rate of reconnection in a strongly magnetized plasma. We recover lower and upper limits on the reconnection rate, depending on the reaction of the magnetic field to stresses exerted from within the reconnection layer. Using Goldreich and Sridhar's model of strong turbulence in a magnetized plasma with negligible intermittency, we find that the lower limit for the reconnection speed is the Alfven speed times the magnetic Reynolds number to the power (-3/16). The upper limit on the reconnection speed is typically a large fraction of Alfven speed. We argue that generic reconnection in turbulent plasmas will normally occur at close to this upper limit. The fraction of magnetic energy that goes directly into electron heating scales as magnetic Reynolds number to the power (-2/5) and the thickness of the current sheet scales as Rm to the power (-3/5). A large fraction of the magnetic energy goes into high frequency Alfven waves. We claim tha...

  17. CHAIN RECONNECTIONS OBSERVED IN SYMPATHETIC ERUPTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Navin Chandra; Magara, Tetsuya [School of Space Research, Kyung Hee University, Yongin, Gyeonggi-Do, 446-701 (Korea, Republic of); Schmieder, Brigitte; Aulanier, Guillaume [LESIA, Observatoire de Paris, PSL Research University, CNRS Sarbonne Universités, Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Jansson, F-92195 Meudon (France); Guo, Yang, E-mail: navin@khu.ac.kr, E-mail: njoshi98@gmail.com [School of Astronomy and Space Science, Nanjing University, 210023 Nanjing (China)

    2016-04-01

    The nature of various plausible causal links between sympathetic events is still a controversial issue. In this work, we present multiwavelength observations of sympathetic eruptions, associated flares, and coronal mass ejections (CMEs) occurring on 2013 November 17 in two close active regions. Two filaments, i.e., F1 and F2, are observed in between the active regions. Successive magnetic reconnections, caused for different reasons (flux cancellation, shear, and expansion) have been identified during the whole event. The first reconnection occurred during the first eruption via flux cancellation between the sheared arcades overlying filament F2, creating a flux rope and leading to the first double-ribbon solar flare. During this phase, we observed the eruption of overlying arcades and coronal loops, which leads to the first CME. The second reconnection is believed to occur between the expanding flux rope of F2 and the overlying arcades of filament F1. We suggest that this reconnection destabilized the equilibrium of filament F1, which further facilitated its eruption. The third stage of reconnection occurred in the wake of the erupting filament F1 between the legs of the overlying arcades. This may create a flux rope and the second double-ribbon flare and a second CME. The fourth reconnection was between the expanding arcades of the erupting filament F1 and the nearby ambient field, which produced the bi-directional plasma flows both upward and downward. Observations and a nonlinear force-free field extrapolation confirm the possibility of reconnection and the causal link between the magnetic systems.

  18. 话语强占:网络民粹主义的传播实践%Taking the Vantage Place of Discourse: The Communication Practice of Online Populism

    Institute of Scientific and Technical Information of China (English)

    陈龙

    2011-01-01

    Taking the vantage place of discourse is a kind of communication practice of online populism. For controlling the public opinion, populists take some strategies such as imposing upon the charges, spreading false news, vituperating, romancing the events and so on. As one of the online behaviors, taking the vantage place of discourse can be rooted back to those social problems like untransparency of information and some unfair phenomena, which provide the breeding soil for populism. As a sort of online communication practice, taking the vantage place of discourse harms the society more and more seriously. Considering of that, the government should adjust the measures to cope with the crisis.%话语强占是网络民粹主义的一种传播实践,通过扣帽子、散布假消息、谩骂、渲染、人肉搜索、限制不同声音等策略,达到对舆论的控制。话语强占,作为民粹主义网络行为,源于信息的不透明、不畅通以及现实生活中客观存在的不公正、不公平现象,这些现象给网络民粹主义提供了滋生的土壤,在信息浑水状态下,话语强占可以达到话语压制的效果。网络场域各种力量的竞争,造成网络民粹主义对语用力量的追求,最终是为了达到对批判对象的群众广场审判。话语强占对社会的危害越来越大,政府应该对危机应对体系作出科学的调整。

  19. On fast reconnection in pair plasmas

    Science.gov (United States)

    Zocco, A.; Chacon, L.; Simakov, A.; Lukin, V.

    2008-11-01

    The relevance of two-fluid effects to fast magnetic reconnection in standard electron-proton plasmas is well-known. The currently accepted view is that such fast reconnection is enabled by fast dispersive waves, which originate in the ion-electron mass difference. However, electron-positron (pair) plasmas do not feature such mass difference, and thus do not support fast dispersive waves. Nevertheless, recent kinetic and fluid pair-plasmas simulations have demonstrated that fast magnetic reconnection is indeed possible, thus casting doubt on the accepted view. In this study, we develop an analytical fluid model for 2D reconnection in non-relativistic, large-guide-field, low-β pair plasmas, including inertia, resistivity, and parallel viscosity.^4 We conclude that fast reconnection is possible in the collisionless (viscosity-dominated) regime, but not in the collisional (resistivity-dominated) one. J. Birn et al., J. Geophys. Res. 106 (A3), pp. 3715--3719 (2001) M. A. Shay et al., Geophys. Res. Lett. 26, 2163 (1999); B. N. Rogers et al., Phys. Rev. Lett. 87, 195004 (2001) See e.g. S. Zenitani and M. Hoshino, Astrophys. J. 562, L63 (2001); N. Bessho and A. Bhattacharjee, Phys. Rev. Lett. 95, 245001 (2005); W. Daughton and H. Karimabadi, Phys. Plasmas 14, 72303 (2007). L. Chac'on, A. N. Simakov, V. S. Lukin, A. Zocco, Phys. Rev. Lett., 025003 (2008)

  20. Hall Reconnection in Partially Ionized Plasmas in the Magnetic Reconnection Experiment

    Science.gov (United States)

    Lawrence, Eric; Ji, Hantao; Yamada, Masaaki; Yoo, Jongsoo

    2011-10-01

    In many space and astrophysical plasmas, such as the solar chromosphere and protoplanetary disks, the degree of ionization can be quite low; often 1% or less. In addition, magnetic reconnection is thought to be a fundamental process in these plasmas. The presence of a large neutral atom population has at least two effects relevant to magnetic reconnection. First, electron-neutral collisions enhance resistive dissipation. Second, strong ion-neutral collisions increase effective ion inertia. This may increase the length scales on which fast Hall reconnection is predicted to occur. By using high gas fill pressures in the Magnetic Reconnection Experiment (MRX), we can study reconnection in partially or weakly ionized plasmas (nn /ne = 1 - - 200). A newly constructed magnetic probe array allows us to make magnetic measurements of the reconnection region with high spatial resolution and large spatial extent. This will allow us to diagnose, for example, the structure of the Hall quadrupole field in these conditions. Langmuir and spectroscopic diagnostics will also provide insight into how neutrals affect the reconnection process. These results will also be discussed in the context of ongoing theoretical work.

  1. Computer simulation of reconnection in planetary magnetospheres

    International Nuclear Information System (INIS)

    The earth's magnetosphere provides an ideal opportunity to model reconnection in well known geometries that are close enough to the idealized analytic models to make a comparison of the computer models with analytic theory meaningful. In addition more detailed, even three-dimensional, models can be used for a comparison with extended data from in situ observations. The computer studies have basically confirmed the reconnection picture that was based on two-dimensional steady state models and linear analytic theory. The three-dimensional models in particular have also added a lot more information on the reconnection process and the structure of flow, magnetic fields, and currents including many features that are consistent with observations and empirical models of geomagnetic substorms

  2. Drift Wave Turbulence and Magnetic Reconnection

    Science.gov (United States)

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

    2015-12-01

    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 and the magnetotail) 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. We specifically consider stabilization of the lower hybrid drift instability (LHDI) and the development of this instability in the presence of a sheared magnetic field. Further investigations of the relative importance of drift wave turbulence in the development of reconnection will also be considered.

  3. Activation of MHD reconnection on ideal timescales

    CERN Document Server

    Landi, S; Del Zanna, L; Tenerani, A; Pucci, F

    2016-01-01

    Magnetic reconnection in laboratory, space and astrophysical plasmas is often invoked to explain explosive energy release and particle acceleration. However, the timescales involved in classical models within the macroscopic MHD regime are far too slow to match the observations. Here we revisit the tearing instability by performing visco-resistive two-dimensional numerical simulations of the evolution of thin current sheets, for a variety of initial configurations and of values of the Lunquist number $S$, up to $10^7$. Results confirm that when the critical aspect ratio of $S^{1/3}$ is reached in the reconnecting current sheets, the instability proceeds on ideal (Alfv\\'enic) macroscopic timescales, as required to explain observations. Moreover, the same scaling is seen to apply also to the local, secondary reconnection events triggered during the nonlinear phase of the tearing instability, thus accelerating the cascading process to increasingly smaller spatial and temporal scales. The process appears to be ro...

  4. Exact solutions for steady reconnective annihilation revisited

    Science.gov (United States)

    Titov, Vyacheslav S.; Tassi, Emanuele; Hornig, Gunnar

    2004-10-01

    This work complements the previous studies on steady reconnective magnetic annihilation in three different geometries: the two-dimensional Cartesian and polar ones and the three-dimensional (3D) cylindrical one. A special class of diffusive solutions is found analytically in explicit form for all of the three geometries. In the 3D case it is extended to a much wider class of exact solutions describing reconnective magnetic annihilation at the separatrix spine line of a magnetic null point. One of the obtained solutions provides an explicit expression for the Craig-Fabling solution. It is also identified which of the steady flow regimes found are dynamically accessible.

  5. 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. PMID:9582116

  6. The structure of the magnetic reconnection exhaust boundary

    CERN Document Server

    Liu, Yi-Hsin; Swisdak, M

    2011-01-01

    The structure of shocks that form at the exhaust boundaries during collisionless reconnection of anti-parallel fields is studied using particle-in-cell (PIC) simulations and modeling based on the anisotropic magnetohydrodynamic equations. Large-scale PIC simulations of reconnection and companion Riemann simulations of shock development demonstrate that the pressure anisotropy produced by counterstreaming ions within the exhaust prevents the development of classical Petschek switch-off-slow shocks (SSS). The shock structure that does develop is controlled by the firehose stability parameter epsilon=1-mu_0(P_parallel-P_perpendicular)/ B^2 through its influence on the speed order of the intermediate and slow waves. Here P_parallel and P_perpendicular are the pressure parallel and perpendicular to the local magnetic field. The exhaust boundary is made up of a series of two shocks and a rotational wave. The first shock takes epsilon from unity upstream to a plateau of 0.25 downstream. The condition epsilon =0.25 i...

  7. Reconnection properties in collisionless plasma with open boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sun, H. E. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Ma, Z. W., E-mail: zwma@zju.edu.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Huang, J. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)

    2014-07-15

    Collisionless magnetic reconnection in a Harris current sheet with different initial thicknesses is investigated using a 21/2 -D Darwin particle-in-cell simulation with the magnetosonic open boundary condition. It is found that the thicknesses of the ion dissipation region and the reconnection current sheet, when the reconnection rate E{sub r} reaches its first peak, are independent of the initial thickness of the current sheet; while the peak reconnection rate depends on it. The peak reconnection rate increases with decrease of the current sheet thickness as E{sub r}∼a{sup −1/2}, where a is the initial current sheet half-thickness.

  8. The effects of plasmaspheric plumes on dayside reconnection

    Science.gov (United States)

    Ouellette, J. E.; Lyon, J. G.; Brambles, O. J.; Zhang, B.; Lotko, W.

    2016-05-01

    We summarize the results of a study on the impact of plasmaspheric plumes on dayside reconnection using a three-dimensional magnetospheric simulation code. We find that the mass loading of magnetospheric flux tubes slows local reconnection rates, though not as much as predicted by Borovsky et al. (2013) due to differences in how well the Cassak-Shay theory matches magnetospheric configurations with and without plasmaspheric plumes. Additionally, we find that in some circumstances reconnection activity is enhanced on either side of the plumes, which moderates its impact on the total dayside reconnection rate. These results provide evidence that plasmaspheric plumes have both local- and global-scale effects on dayside reconnection.

  9. Place Branding

    DEFF Research Database (Denmark)

    Medway, Dominic; Swanson, Kathryn; Neirotti, Lisa Delpy;

    2015-01-01

    Purpose: – The purpose of this paper is to report on a special session entitled “Place branding: Are we wasting our time?”, held at the American Marketing Association’s Summer Marketing Educators’ conference in 2014. Design/methodology/approach: – The report details the outcome of an Oxford......: – The outcome of the debate points towards a need for place brands to develop as more inclusive and organic entities, in which case it may be best for place practitioners to avoid creating and imposing a place brand and instead help shape it from the views of stakeholder constituencies. This shifts the notion...... of place branding towards an activity centred on “curation”. Originality/value: – The use of a competitive debating format as a means for exploring academic ideas and concepts in the place management field....

  10. Chain Reconnections observed in Sympathetic Eruptions

    CERN Document Server

    Joshi, Navin Chandra; Magara, Tetsuya; Guo, Yang; Aulanier, Guillaume

    2016-01-01

    The nature of various plausible causal links between sympathetic events is still a controversial issue. In this work, we present multi-wavelength observations of sympathetic eruptions, associated flares and coronal mass ejections (CMEs) occurring on 2013 November 17 in two close-by active regions. Two filaments i.e., F1 and F2 are observed in between the active regions. Successive magnetic reconnections, caused by different reasons (flux cancellation, shear and expansion) have been identified during the whole event. The first reconnection occurred during the first eruption via flux cancellation between the sheared arcades overlying filament F2, creating a flux rope and leading to the first double ribbon solar flare. During this phase we observed the eruption of overlaying arcades and coronal loops, which leads to the first CME. The second reconnection is believed to occur between the expanding flux rope of F2 and the overlying arcades of the filament F1. We suggest that this reconnection destabilized the equi...

  11. Scaling of Navier-Stokes trefoil reconnection

    CERN Document Server

    Kerr, Robert M

    2016-01-01

    The reconnection of a trefoil vortex knot is examined numerically to determine how its helicity and two of its vorticity norms behave. During an initial phase, the helicity is remarkably preserved, as reported in recent experiments (Scheeler et al. 2014a). In addition, the enstrophy ($Z$) has self-similar growth where all $\\sqrt{\

  12. VINETA II: a linear magnetic reconnection experiment.

    Science.gov (United States)

    Bohlin, H; Von Stechow, A; Rahbarnia, K; Grulke, O; Klinger, T

    2014-02-01

    A linear experiment dedicated to the study of driven magnetic reconnection is presented. The new device (VINETA II) is suitable for investigating both collisional and near collisionless reconnection. Reconnection is achieved by externally driving magnetic field lines towards an X-point, inducing a current in the background plasma which consequently modifies the magnetic field topology. Owing to the open field line configuration of the experiment, the current is limited by the axial sheath boundary conditions. A plasma gun is used as an additional electron source in order to counterbalance the charge separation effects and supply the required current. Two drive methods are used in the device. First, an oscillating current through two parallel conductors drive the reconnection. Second, a stationary X-point topology is formed by the parallel conductors, and the drive is achieved by an oscillating current through a third conductor. In the first setup, the magnetic field of the axial plasma current dominates the field topology near the X-point throughout most of the drive. The second setup allows for the amplitude of the plasma current as well as the motion of the flux to be set independently of the X-point topology of the parallel conductors. PMID:24593355

  13. Applying Relativistic Reconnection to Blazar Jets

    CERN Document Server

    Nalewajko, Krzysztof

    2016-01-01

    Rapid and luminous flares of non-thermal radiation observed in blazars require an efficient mechanism of energy dissipation and particle acceleration in relativistic active galactic nuclei (AGN) jets. Particle acceleration in relativistic magnetic reconnection is being actively studied by kinetic numerical simulations. Relativistic reconnection produces hard power-law electron energy distributions N(gamma) = N_0 gamma^(-p) exp(-gamma/gamma_max) with index p -> 1 and exponential cut-off Lorentz factor gamma_max ~ sigma in the limit of magnetization sigma = B^2/(4 pi w) >> 1 (where w is the relativistic enthalpy density). Reconnection in electron-proton plasma can additionally boost gamma_max by the mass ratio m_p/m_e. Hence, in order to accelerate particles to gamma_max ~ 10^6 in the case of BL Lacs, reconnection should proceed in plasma of very high magnetization sigma_max >~ 10^3. On the other hand, moderate mean jet magnetization values are required for magnetic bulk acceleration of relativistic jets, sigma...

  14. Transition from antiparallel to component magnetic reconnection

    Science.gov (United States)

    Swisdak, M.; Drake, J. F.; Shay, M. A.; McIlhargey, J. G.

    2005-05-01

    We study the transition between antiparallel and component collisionless magnetic reconnection with two-dimensional particle-in-cell simulations. The primary finding is that a guide field ≈0.1 times as strong as the asymptotic reconnecting field (roughly the field strength at which the electron Larmor radius is comparable to the width of the electron current layer) is sufficient to magnetize the electrons in the vicinity of the X line, thus causing significant changes to the structure of the electron dissipation region. This implies that great care should be exercised before concluding that magnetospheric reconnection is antiparallel. We also find that even for such weak guide fields, strong inward flowing electron beams form in the vicinity of the magnetic separatrices and Buneman unstable distribution functions arise at the X line itself. As in the calculations of Hesse et al. (2002) and Yin and Winske (2003) the nongyrotropic elements of the electron pressure tensor play the dominant role in decoupling the electrons from the magnetic field at the X line, regardless of the magnitude of the guide field and the associated strong variations in the pressure tensor's spatial structure. Despite these changes, and consistent with previous work, the reconnection rate does not vary appreciably with the strength of the guide field as it changes between 0 and a value equal to the asymptotic reversed field.

  15. Collisionless magnetic reconnection under anisotropic MHD approximation

    Science.gov (United States)

    Hirabayashi, Kota; Hoshino, Masahiro

    We study the formation of slow-mode shocks in collisionless magnetic reconnection by using one- and two-dimensional collisionless magneto-hydro-dynamic (MHD) simulations based on the double adiabatic approximation, which is an important step to bridge the gap between the Petschek-type MHD reconnection model accompanied by a pair of slow shocks and the observational evidence of the rare occasion of in-situ slow shock observation. According to our results, a pair of slow shocks does form in the reconnection layer. The resultant shock waves, however, are quite weak compared with those in an isotropic MHD from the point of view of the plasma compression and the amount of the magnetic energy released across the shock. Once the slow shock forms, the downstream plasma are heated in highly anisotropic manner and a firehose-sense (P_{||}>P_{⊥}) pressure anisotropy arises. The maximum anisotropy is limited by the marginal firehose criterion, 1-(P_{||}-P_{⊥})/B(2) =0. In spite of the weakness of the shocks, the resultant reconnection rate is kept at the same level compared with that in the corresponding ordinary MHD simulations. It is also revealed that the sequential order of propagation of the slow shock and the rotational discontinuity, which appears when the guide field component exists, changes depending on the magnitude of the guide field. Especially, when no guide field exists, the rotational discontinuity degenerates with the contact discontinuity remaining at the position of the initial current sheet, while with the slow shock in the isotropic MHD. Our result implies that the slow shock does not necessarily play an important role in the energy conversion in the reconnection system and is consistent with the satellite observation in the Earth's magnetosphere.

  16. Diffusive Shock Acceleration and Reconnection Acceleration Processes

    Science.gov (United States)

    Zank, G. P.; Hunana, P.; Mostafavi, P.; Le Roux, J. A.; Li, Gang; Webb, G. M.; Khabarova, O.; Cummings, A.; Stone, E.; Decker, R.

    2015-12-01

    Shock waves, as shown by simulations and observations, can generate high levels of downstream vortical turbulence, including magnetic islands. We consider a combination of diffusive shock acceleration (DSA) and downstream magnetic-island-reconnection-related processes as an energization mechanism for charged particles. Observations of electron and ion distributions downstream of interplanetary shocks and the heliospheric termination shock (HTS) are frequently inconsistent with the predictions of classical DSA. We utilize a recently developed transport theory for charged particles propagating diffusively in a turbulent region filled with contracting and reconnecting plasmoids and small-scale current sheets. Particle energization associated with the anti-reconnection electric field, a consequence of magnetic island merging, and magnetic island contraction, are considered. For the former only, we find that (i) the spectrum is a hard power law in particle speed, and (ii) the downstream solution is constant. For downstream plasmoid contraction only, (i) the accelerated spectrum is a hard power law in particle speed; (ii) the particle intensity for a given energy peaks downstream of the shock, and the distance to the peak location increases with increasing particle energy, and (iii) the particle intensity amplification for a particular particle energy, f(x,c/{c}0)/f(0,c/{c}0), is not 1, as predicted by DSA, but increases with increasing particle energy. The general solution combines both the reconnection-induced electric field and plasmoid contraction. The observed energetic particle intensity profile observed by Voyager 2 downstream of the HTS appears to support a particle acceleration mechanism that combines both DSA and magnetic-island-reconnection-related processes.

  17. Better Place

    DEFF Research Database (Denmark)

    Rask, Morten; Bakke, Nikolas; Lindhøj, Jan

    among others and that will drive the global transportation industry to becoming driven by electric vehicles (EVs). Better Place does this by selling its customers 'mileage' and a car without a battery. The case highlights the internationalisation process of Better Place from an international business...

  18. Ecological Mural as Community Reconnection

    Science.gov (United States)

    Kang Song, Young Imm; Gammel, Jo Ann

    2011-01-01

    Murals are particularly visually captivating forms of public art due to their size and accessibility. Mural images also capture public attention and provoke viewers to explore layers of meaning and find hidden stories. They are often in places that people come to visit, study, play, congregate and discuss matters that may relate to the content of…

  19. Three-dimensional magnetic reconnection through a moving magnetic null

    Directory of Open Access Journals (Sweden)

    V. S. Lukin

    2011-11-01

    Full Text Available A computational study of three-dimensional magnetic reconnection between two flux ropes through a moving reconnection site is presented. The configuration is considered in the context of two interacting spheromaks constrained by a perfectly conducting cylindrical boundary and oriented to form a single magnetic field null at its center. The initial magnetic field configuration is embedded into a uniform thermal plasma and is unstable to tilting. As the spheromaks tilt, their magnetic fields begin to reconnect at the null, subsequently displacing both the null and the reconnection site. The motion of the reconnection region and the magnetic null are shown to be correlated, with stronger correlation and faster reconnection observed in plasmas with lower thermal to magnetic pressure ratio. It is also shown that ion inertial effects allow for yet faster reconnection, but do not qualitatively change the dynamics of the process. Implications of the coupling between moving magnetic nulls and reconnection sites, as well as of possible mechanisms for fast reconnection through a moving reconnection region, are discussed. The simulations are conducted using both single-fluid and Hall MHD plasma models within the HiFi multi-fluid modeling framework.

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

    International Nuclear Information System (INIS)

    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. Taking Design Games Seriously

    DEFF Research Database (Denmark)

    Eriksen, Mette Agger; Brandt, Eva; Mattelmäki, Tuuli;

    2014-01-01

    Using design games at Participatory Design (PD) events is well acknowledged as a fruitful way of staging participation. As PD researchers, we have many such experiences, and we have argued that design games connect participants and promote equalizing power relations. However, in this paper, we...... will (self) critically re-connect and reflect on how people (humans) and materials (non-humans) continually participate and intertwine in various power relations in design game situations. The analysis is of detailed situated actions with one of our recent games, UrbanTransition. Core concepts mainly from...... Bruno Latour’s work on Actor-Network-Theory are applied. The aim is to take design games seriously by e.g. exploring how assemblages of humans and non-humans are intertwined in tacitly-but-tactically staging participation, and opening up for or hindering negotiations and decision-making, thus starting...

  2. Places Connected:

    DEFF Research Database (Denmark)

    Hansen, Annette Skovsted

    Nations Volunteer of Japanese nationality. Networks of personal ties, ideas, feelings, and material culture. By combining work on the experience of place with network historiography on migration and kinship, the paper presents a case on the function of the temporary encounter in human networks....... experience the places of Denmark and Japan temporarily integrate the national histories of these two countries in the histories of their home countries and vice versa. Thereby, I wish to offer a dynamic understanding of development history and globalization, which challenges the nationally bound histories...... experiences of place, however, when it is often the same people who experience many different places? Along with many other so-called donors in the 1950s, Denmark and Japan chose to invest in the education of own and other nationals involved in development and thereby financed personal connections between...

  3. Non-Maxwellian electron distribution functions due to self-generated turbulence in collisionless guide-field reconnection

    CERN Document Server

    Muñoz, P A

    2016-01-01

    Non-Maxwellian electron velocity space distribution functions (EVDF) are useful signatures of plasma conditions and non-local consequences of collisionless magnetic reconnection. In the past, the evolution of the EVDFs was investigated mainly for antiparallel or weak-guide-field reconnection. The shape of EVDFs is, however, not well known yet for oblique (or component-) reconnection in dependence on a finite guide magnetic field component perpendicular to the reconnection plane. In view of the multi-spacecraft mission MMS, we derive the non-Maxwellian features of EVDFs formed by collisionless magnetic reconnection starting from very weak ($b_g\\approx0$) up to very strong ($b_g=8$) guide-field strengths $b_g$, taking into account the feedback of the self-generated turbulence. For this sake, we carry out 2.5D fully-kinetic Particle-in-Cell (PiC) simulations using the ACRONYM code. We obtained anisotropic EVDFs and the distribution of electron beams propagating along the separatrices as well as in the exhaust re...

  4. Women take the island: nation, profession, place Women take the island: nation, profession, place

    Directory of Open Access Journals (Sweden)

    Ruth Morse

    2008-04-01

    Full Text Available The Tempest has been one of Shakespeare’s most adapted plays. Its stage history is concomitantly a history of the British theatre, from regularized comedy to semi-opera to pantomime to opera. It has had other lives, too, from its position in romantic ideas of Shakespeare’s biography and his so-called farewell to the stage, to a supporting role as witness for the nineteenth-century Darwinians’ idea of the missing link, to a veritable efflorescence of walk-on parts, cameos, and star vehicles in twentieth-century psychoanalytic and social arguments about European expansion.2 The play has given us individual poems and paintings, not to speak of screen-plays for several film adaptations. The Tempest has been one of Shakespeare’s most adapted plays. Its stage history is concomitantly a history of the British theatre, from regularized comedy to semi-opera to pantomime to opera. It has had other lives, too, from its position in romantic ideas of Shakespeare’s biography and his so-called farewell to the stage, to a supporting role as witness for the nineteenth-century Darwinians’ idea of the missing link, to a veritable efflorescence of walk-on parts, cameos, and star vehicles in twentieth-century psychoanalytic and social arguments about European expansion.2 The play has given us individual poems and paintings, not to speak of screen-plays for several film adaptations.

  5. Particle Acceleration in 3D Magnetic Reconnection

    Science.gov (United States)

    Dahlin, J.; Drake, J. F.; Swisdak, M.

    2015-12-01

    Magnetic reconnection is an important driver of energetic particles in phenomena such as magnetospheric storms and solar flares. Using kinetic particle-in-cell (PIC) simulations, we show that the stochastic magnetic field structure which develops during 3D reconnection plays a vital role in particle acceleration and transport. In a 2D system, electrons are trapped in magnetic islands which limits their energy gain. In a 3D system, however, the stochastic magnetic field enables the energetic electrons to access volume-filling acceleration regions and therefore gain energy much more efficiently than in the 2D system. We also examine the relative roles of two important acceleration drivers: parallel electric fields and a Fermi mechanism associated with reflection of charged particles from contracting field lines. We find that parallel electric fields are most important for accelerating low energy particles, whereas Fermi reflection dominates energetic particle production. We also find that proton energization is reduced in the 3D system.

  6. 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.

  7. 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.

  8. Magnetic reconnection: from MHD to QED

    CERN Document Server

    Bulanov, S V

    2016-01-01

    The paper examines the prospects of using laser plasmas for studying novel regimes of the magnetic field line reconnection and charged particle acceleration. Basic features of plasma dynamics in the three-dimensional configurations relevant to the formation of current sheets in a plasma are addressed by analyzing exact self-similar solutions of the magneto-hydrodynamics and electron magneto-hydrodynamics equations. Then the magnetic field annihilation in the ultrarelativistic limit is considered, when the opposite polarity magnetic field is generated in collisionless plasma by multiple laser pulses, in the regime with a dominant contribution of the displacement current exciting a strong large-scale electric field. This field leads to the conversion of the magnetic energy into the kinetic energy of accelerated particles inside a thin current sheet. Charged particle acceleration during magnetic field reconnection is discussed when radiation friction and quantum electrodynamics effects become dominant.

  9. On the Value of the Reconnection Rate

    CERN Document Server

    Comisso, Luca

    2016-01-01

    Numerical simulations have consistently shown that the reconnection rate in certain collisionless regimes can be fast, on the order of $0.1 v_A B_u$, where $v_A$ and $B_u$ are the Alfv\\'en speed and the reconnecting magnetic field upstream of the ion diffusion region. This particular value has been reported in myriad numerical simulations under disparate conditions. However, despite decades of research, the reasons underpinning this specific value remain mysterious. Here, we present an overview of this problem and discuss the conditions under which the "0.1 value" is attained. Furthermore, we explain why this problem should be interpreted in terms of the ion diffusion region length.

  10. On Tripolar Magnetic Reconnection and Coronal Heating

    CERN Document Server

    Pandey, K; Lohani, N K; Pandey, Kumud; Narain, Udit

    2003-01-01

    Using recent data for the photosphere-chromosphere region of the solar atmosphere the magnetic reconnection in tripolar geometry has been investigated through the procedure of Sturrock (1999). Particular attention has been given to the width of the reconnecting region, wave number of the rapidly growing tearing mode, island length scales, frequency of MHD fluctuations, tearing mode growth rate, energy dissipation rate and minimum magnetic field strength required to heat chromospheric plasma to coronal temperatures. It is found that small length scales are formed in the upper chromosphere. The maximum growth rate of tearing mode instability coincides with the peak in the energy dissipation rate both of which occur in the upper chromosphere at the same height. It is realized that the distribution of magnetic field with height is essential for a better understanding of the coronal heating problem.

  11. 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. PMID:25013068

  12. Magnetic reconnection between a solar filament and nearby coronal loops

    Science.gov (United States)

    Li, Leping; Zhang, Jun; Peter, Hardi; Priest, Eric; Chen, Huadong; Guo, Lijia; Chen, Feng; Mackay, Duncan

    2016-09-01

    Magnetic reconnection is difficult to observe directly but coronal structures on the Sun often betray the magnetic field geometry and its evolution. Here we report the observation of magnetic reconnection between an erupting filament and its nearby coronal loops, resulting in changes in the filament connection. X-type structures form when the erupting filament encounters the loops. The filament becomes straight, and bright current sheets form at the interfaces. Plasmoids appear in these current sheets and propagate bi-directionally. The filament disconnects from the current sheets, which gradually disperse and disappear, then reconnects to the loops. This evolution suggests successive magnetic reconnection events predicted by theory but rarely detected with such clarity in observations. Our results confirm the three-dimensional magnetic reconnection theory and have implications for the evolution of dissipation regions and the release of magnetic energy for reconnection in many magnetized plasma systems.

  13. Healthy Places

    Centers for Disease Control (CDC) Podcasts

    2007-04-10

    Every person has a stake in environmental public health. As the environment deteriorates, so does the physical and mental health of the people within it. Healthy places are those designed and built to improve the quality of life for all people who live, work, worship, learn, and play within their borders -- where every person is free to make choices amid a variety of healthy, available, accessible, and affordable options. The CDC recognizes significant health issues and places that are vital in developing the Healthy Places program and provides examples in this report.  Created: 4/10/2007 by CDC National Center for Environmental Health.   Date Released: 4/13/2007.

  14. Generation of Alfven Waves by Magnetic Reconnection

    OpenAIRE

    Kigure, Hiromitsu; Takahashi, Kunio; Shibata, Kazunari; Yokoyama, Takaaki; Nozawa, Satoshi

    2010-01-01

    In this paper, results of 2.5-dimensional magnetohydrodynamical simulations are reported for the magnetic reconnection of non-perfectly antiparallel magnetic fields. The magnetic field has a component perpendicular to the computational plane, that is, guide field. The angle theta between magnetic field lines in two half regions is a key parameter in our simulations whereas the initial distribution of the plasma is assumed to be simple; density and pressure are uniform except for the current s...

  15. Shear-Driven Reconnection in Kinetic Models

    Science.gov (United States)

    Black, C.; Antiochos, S. K.; Germaschewski, K.; Karpen, J. T.; DeVore, C. R.; Bessho, N.

    2015-12-01

    The explosive energy release in solar eruptive phenomena is believed to be due to magnetic reconnection. In the standard model for coronal mass ejections (CME) and/or solar flares, the free energy for the event resides in the strongly sheared magnetic field of a filament channel. The pre-eruption force balance consists of an upward force due to the magnetic pressure of the sheared field countered by a downward tension due to overlying unsheared field. Magnetic reconnection disrupts this force balance; therefore, it is critical for understanding CME/flare initiation, to model the onset of reconnection driven by the build-up of magnetic shear. In MHD simulations, the application of a magnetic-field shear is a trivial matter. However, kinetic effects are dominant in the diffusion region and thus, it is important to examine this process with PIC simulations as well. The implementation of such a driver in PIC methods is challenging, however, and indicates the necessity of a true multiscale model for such processes in the solar environment. The field must be sheared self-consistently and indirectly to prevent the generation of waves that destroy the desired system. Plasma instabilities can arise nonetheless. In the work presented here, we show that we can control this instability and generate a predicted out-of-plane magnetic flux. This material is based upon work supported by the National Science Foundation under Award No. AGS-1331356.

  16. Relativistic Two-fluid Simulations of Guide Field Magnetic Reconnection

    CERN Document Server

    Zenitani, Seiji; Klimas, Alex

    2009-01-01

    The nonlinear evolution of relativistic magnetic reconnection in sheared magnetic configuration (with a guide field) is investigated by using two-dimensional relativistic two-fluid simulations. Relativistic guide field reconnection features the charge separation and the guide field compression in and around the outflow channel. As the guide field increases, the composition of the outgoing energy changes from enthalpy-dominated to Poynting-dominated. The inertial effects of the two-fluid model play an important role to sustain magnetic reconnection. Implications for the single fluid magnetohydrodynamic approach and the physics models of relativistic reconnection are briefly addressed.

  17. Dissipation and reconnection in boundary-driven reduced magnetohydrodynamics

    International Nuclear Information System (INIS)

    We study the statistics of coherent current sheets, the population of X-type critical points, and reconnection rates in a coronal loop geometry, via numerical simulations of reduced magnetohydrodynamic turbulence. Current sheets and sites of reconnection (magnetic X-points) are identified in two-dimensional planes of the three-dimensional simulation domain. The geometry of the identified current sheets—including area, length, and width—and the magnetic dissipation occurring in the current sheets are statistically characterized. We also examine the role of magnetic reconnection, by computing the reconnection rates at the identified X-points and investigating their association with current sheets.

  18. Numerical examination of plasmoid-induced reconnection model for solar flares: the relation between plasmoid velocity and reconnection rate

    CERN Document Server

    Nishida, Keisuke; Shiota, Daikou; Takasaki, Hiroyuki; Magara, Tetsuya; Shibata, Kazunari

    2008-01-01

    The plasmoid-induced-reconnection model explaining solar flares based on bursty reconnection produced by an ejecting plasmoid suggests a possible relation between the ejection velocity of a plasmoid and the rate of magnetic reconnection. In this study, we focus on the quantitative description of this relation. We performed magnetohydrodynamic (MHD) simulations of solar flares by changing the values of resistivity and the plasmoid velocity. The plasmoid velocity has been changed by applying an additional force to the plasmoid to see how the plasmoid velocity affects the reconnection rate. An important result is that the reconnection rate has a positive correlation with the plasmoid velocity, which is consistent with the plasmoid-induced-reconnection model for solar flares. We also discuss an observational result supporting this positive correlation.

  19. Places to Go: Moodle

    Science.gov (United States)

    Downes, Stephen

    2006-01-01

    Educators are becoming increasingly interested in alternatives to learning management systems (LMS) Blackboard and WebCT. Stephen Downes's column Places to Go turns to one internationally popular open source LMS--Moodle. Downes takes the reader through Moodle's Web site, which is simultaneously a Web site about its LMS and an example of what its…

  20. Particle acceleration and transport in reconnecting twisted loops in a stratified atmosphere

    CERN Document Server

    Gordovskyy, Mykola; Kontar, Eduard; Bian, Nicolas

    2015-01-01

    Twisted coronal loops should be ubiquitous in the solar corona. Twisted magnetic fields contain excess magnetic energy, which can be released during magnetic reconnection, causing solar flares. The aim of this work is to investigate magnetic reconnection, and particle acceleration and transport in kink-unstable twisted coronal loops, with a focus on the effects of resistivity, loop geometry and atmospheric stratification. Another aim is to perform forward-modelling of bremsstrahlung emission and determine the structure of hard X-ray sources. We use a combination of magnetohydrodynamic (MHD) and test-particle methods. First, the evolution of the kinking coronal loop is considered using resistive MHD model, incorporating atmospheric stratification and loop curvature. Then, the obtained electric and magnetic fields and density distributions are used to calculate electron and proton trajectories using a guiding-centre approximation, taking into account Coulomb collisions. It is shown that electric fields in twist...

  1. Experiments on the effects of global force balance and local reconnection physics on magnetic reconnection with a guide field

    Science.gov (United States)

    Fox, W.; Sciortino, F.; Yoo, J.; Jara-Almonte, J.; Na, B.; Ji, H.; Yamada, M.

    2015-11-01

    In many plasma environments ranging from astrophysics to fusion, magnetic reconnection occurs with a finite guide field ranging from a fraction to many times the upstream reconnecting component. Theory and simulation yields a range of predictions of scaling of the rate of reconnection with guide field. Recent experiments on the Magnetic Reconnection Experiment observed a systematic decrease in reconnection rates with increasing guide field. Here we present a new set of experimental results on MRX with a controlled applied guide magnetic field ranging from 0 to approximately 3 times the upstream reconnection field, where we observe both global and local processes which affect the reconnection rate in the guide field regime. First, we observe and quantify the effects of global force balance, in particular global back pressure due to pileup of magnetic field in the downstream, which decreases the outflow of plasma from the current sheet and hence the reconnection rate. Second, we study the role of electron pressure in the generalized Ohm's law in the guide field regime and its role in setting the reconnection rate.

  2. Designed Places

    DEFF Research Database (Denmark)

    Stender, Marie

    The 2008 financial crisis has left traces in the built environment of Copenhagen like many other places: Building projects are left unfinished or their function or finish is changed due to new economic circumstances. An ethnographic exploration of these traces exposes central aspects of what...... like the forces of nature. Based on a fieldwork in three new housing developments in Copenhagen, this paper aims to bring the financial crisis ‘down to earth’ by examining the material shapes it has taken in the spaces of everyday life. The ethnographic cases in question are places that are somewhat...... over-designed: Not only the places’ architecture and built environment but also their identity, image and social life has been carefully planned for. At the same time their design and architectural layout bear witness to a seemingly longing for that which is unplanned and beyond design, thus staging...

  3. Places available**

    CERN Multimedia

    2003-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. TECHNICAL TRAINING Monique Duval tel. 74924 technical.training@cern.ch ** The number of places available may vary. Please check our Web site to find out the current availability. Places are available in the following courses: ACCESS 2000 - niveau 1 : 13 & 14.11.03 (2 jours) C++ for Particle Physicists : 17 – 21.11.03 (6 X 3-hour lectures) Programmation automate Schneider TSX Premium – niveau 2 : 18 – 21.11.03 (4 jours) JAVA 2 Enterprise Edition – Part 1 : WEB Applications : 20 & ...

  4. Places available

    CERN Multimedia

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. Places available The number of places available may vary. Please check our Web site to find out the current availability. Places are available in the following courses : Introduction à Outlook : 19.8.2004 (1 journée) Outlook (short course I) : E-mail : 31.8.2004 (2 hours, morning) Outlook (short course II) : Calendar, Tasks and Notes : 31.8.2004 (2 hours, afternoon) Instructor-led WBTechT Study or Follow-up for Microsoft Applications : 7.9.2004 (morning) Outlook (short course III) : Meetings and Delegation : 7.9.2004 (2 hours, afternoon) Introduction ...

  5. Places disponibles/Places available

    CERN Multimedia

    2004-01-01

    Etant donné le délai d'impression du Bulletin, ces places peuvent ne plus être disponibles au moment de sa parution. Veuillez consulter notre site Web pour avoir la dernière mise à jour. The number of places available may vary. Please check our Web site to find out the current availability. Des places sont disponibles dans les cours suivants : / Places are available in the following courses : Introduction à Outlook : 19.8.2004 (1 journée) Outlook (short course I) : E-mail : 31.8.2004 (2 hours, morning) Outlook (short course II) : Calendar, Tasks and Notes : 31.8.2004 (2 hours, afternoon) Instructor-led WBTechT Study or Follow-up for Microsoft Applications : 7.9.2004 (morning) Outlook (short course III) : Meetings and Delegation : 7.9.2004 (2 hours, afternoon) Introduction au VHDL et utilisation du simulateur NCVHDL de CADENCE : 7 & 8.9.2004 (2 jours) Joint PVSS JCOP Framework : 13 - 17.9.2004 (5 days) AutoCAD 2002 - niveau 1 : 13, 14, 23, 24.9.2004 (4 jours) Programmation S...

  6. Study of Multiple Scale Physics of Magnetic Reconnection on the FLARE (Facility for Laboratory Reconnection Experiments)

    Science.gov (United States)

    Ji, H.; Bhattacharjee, A.; Prager, S.; Daughton, W. S.; Bale, S. D.; Carter, T. A.; Crocker, N.; Drake, J. F.; Egedal, J.; Sarff, J.; Wallace, J.; Chen, Y.; Cutler, R.; Fox, W. R., II; Heitzenroeder, P.; Kalish, M.; Jara-Almonte, J.; Myers, C. E.; Ren, Y.; Yamada, M.; Yoo, J.

    2015-12-01

    The FLARE device (flare.pppl.gov) is a new intermediate-scale plasma experiment under construction at Princeton to study magnetic reconnection in regimes directly relevant to space, solar and astrophysical plasmas. The existing small-scale experiments have been focusing on the single X-line reconnection process either with small effective sizes or at low Lundquist numbers, but both of which are typically very large in natural plasmas. The configuration of the FLARE device is designed to provide experimental access to the new regimes involving multiple X-lines, as guided by a reconnection "phase diagram" [Ji & Daughton, PoP (2011)]. Most of major components of the FLARE device have been designed and are under construction. The device will be assembled and installed in 2016, followed by commissioning and operation in 2017. The planned research on FLARE as a user facility will be discussed on topics including the multiple scale nature of magnetic reconnection from global fluid scales to ion and electron kinetic scales. Results from scoping simulations based on particle and fluid codes and possible comparative research with space measurements will be presented.

  7. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74460

    2001-01-01

    Places are available in the following courses: Nouveautés de FileMaker : 20 - 23.03.01 (4 matins) Contract Follow-up : 9.4.01 (3 heures) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  8. Direct evidence for kinetic effects associated with solar wind reconnection.

    Science.gov (United States)

    Xu, Xiaojun; Wang, Yi; Wei, Fengsi; Feng, Xueshang; Deng, Xiaohua; Ma, Yonghui; Zhou, Meng; Pang, Ye; Wong, Hon-Cheng

    2015-01-01

    Kinetic effects resulting from the two-fluid physics play a crucial role in the fast collisionless reconnection, which is a process to explosively release massive energy stored in magnetic fields in space and astrophysical plasmas. In-situ observations in the Earth's magnetosphere provide solid consistence with theoretical models on the point that kinetic effects are required in the collisionless reconnection. However, all the observations associated with solar wind reconnection have been analyzed in the context of magnetohydrodynamics (MHD) although a lot of solar wind reconnection exhausts have been reported. Because of the absence of kinetic effects and substantial heating, whether the reconnections are still ongoing when they are detected in the solar wind remains unknown. Here, by dual-spacecraft observations, we report a solar wind reconnection with clear Hall magnetic fields. Its corresponding Alfvenic electron outflow jet, derived from the decouple between ions and electrons, is identified, showing direct evidence for kinetic effects that dominate the collisionless reconnection. The turbulence associated with the exhaust is a kind of background solar wind turbulence, implying that the reconnection generated turbulence has not much developed.

  9. Places available **

    CERN Multimedia

    2003-01-01

    Des places sont disponibles dans les cours suivants : Places are available in the following courses : DISP-2003 - Spring I Term : Introduction to Digital Signal Processing : 20, 27.2, 6, 13, 20, 27.3, 3.4.03 (7 X 2-hour lectures) AXEL-2003 - Introduction to Accelerators : 24 - 28.2.03 (10 X 1-hour lectures) AutoCAD 2002 - niveau 1 : 24, 25.2 & 3, 4.3.03 (4 jours) Introduction à Windows 2000 au CERN : 25.2.03 (1/2 journée) LabView base 2/LabView Basics 2 : 10 & 11.3.03 (2 jours/2 days) langue à définir/Language to be decided C++ for Particle Physicists : 10 - 14.3.03 (6 X 3-hour lectures) Introduction to PVSS : 10.3.03 (half day, afternoon) Basic PVSS : 11 - 13.3.03 (3 days) LabView avancé /LabView Advanced : 12 - 14.3.03 (3 jours/3days) Langue à définir/language to be decided AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 17, 18, 24 & 25.3.03 (6 jours) PVSS - JCOP Framework Tutorial : 14.3.03 (1 day) CLEAN-2002 : Working in a cleanroom : 2.4.03 (half-day, afternoon, free course, regis...

  10. Places available **

    CERN Multimedia

    2003-01-01

    Des places sont disponibles dans les cours suivants : Places are available in the following courses : C++ for Particle Physicists : 10 - 14.3.03 (6 X 3-hour lectures) Introduction to PVSS : 10.3.03 (half day, afternoon) Basic PVSS : 11 - 13.3.03 (3 days) PVSS - JCOP Framework Tutorial : 14.3.03 (1 day) CLEAN-2002 : Working in a cleanroom : 2.4.03 (half-day, afternoon, free course, registration required) LabView base 1/LabView Basics 1 : 9 - 11.4.03 (3 jours/3 days) Langue à définir/language to be decided DISP-2003 - Spring II Term : Advanced Digital Signal Processing : 30.4, 7, 14, 21.5.03 (4 X 2-hour lectures) AutoCAD 2002 - niveau 1 : 29, 30.4 et 7, 8.5.03 (4 jours) AutoCAD 2002 - niveau 2 : 5 & 6.5.03 (2 jours) AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 20, 21, 27 & 28.5.03 (6 jours) Formation Siemens SIMATIC /Siemens SIMATIC Training : Introduction à STEP7 /Introduction to STEP7 : 11 & 12.3.03 / 3 & 4.6.03 (2 jours/2 days) Programmation STEP7/STEP7 Programming : 31.3 - 4.4.03 / 16...

  11. Places available **

    CERN Multimedia

    2003-01-01

    Des places sont disponibles dans les cours suivants : Places are available in the following courses : Introduction à Windows 2000 au CERN : 25.2.03 (1/2 journée) LabView base 2/LabView Basics 2 : 10 & 11.3.03 (2 jours/2 days) langue à définir/Language to be decided C++ for Particle Physicists : 10 - 14.3.03 (6 X 3-hour lectures) Introduction to PVSS : 10.3.03 (half day, afternoon) Basic PVSS : 11 - 13.3.03 (3 days) LabView avancé /LabView Advanced : 12 - 14.3.03 (3 jours/3days) Langue à définir/Language to be decided AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 17, 18, 24 & 25.3.03 (6 jours) PVSS - JCOP Framework Tutorial : 14.3.03 (1 day) CLEAN-2002 : Working in a cleanroom : 2.4.03 (half-day, afternoon, free course, registration required) LabView base 1/LabView Basics 1 : 9 - 11.4.03 (3 jours/3 days) Langue à définir/Language to be decided DISP-2003 - Spring II Term : Advanced Digital Signal Processing : 30.4, 7, 14, 21.5.03 (4 X 2-hour lectures) AutoCAD 2002 - niveau 2 : 5 & 6.5.03 (...

  12. Places available **

    CERN Multimedia

    2003-01-01

    Des places sont disponibles dans les cours suivants : Places are available in the following courses : WorldFIP 2003 pour utilisateurs : 11-14.2.03 (4 jours) DISP-2003 ? Spring I Term : Introduction to Digital Signal Processing : 20, 27.2, 6, 13, 20, 27.3, 3.4.03 (7 X 2-hour lectures) AXEL-2003 - Introduction to Accelerators : 24-28.2.03 (10 X 1-hour lectures) AutoCAD 2002 - niveau 1 : 24, 25.2 & 3, 4.3.03 (4 jours) Introduction à Windows 2000 au CERN : 25.2.03 (1/2 journée) LabView base 2/LabView Basics 2 : 10 & 11.3.03 (2 jours/2 days) langue à définir/Language to be decided C++ for Particle Physicists : 10 ? 14.3.03 (6 X 3-hour lectures) Introduction to PVSS : 10.3.03 (half day, afternoon) Basic PVSS : 11 - 13.3.03 (3 days) LabView avancé /LabView Advanced : 12 - 14.3.03 (3 jours/3days) Langue à définir/language to be decided AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 17, 18, 24 & 25.3.03 (6 jours) PVSS - JCOP Framework Tutorial : 14.3.03 (1 day) MAGNE-03 - Magnetism for Technical Ele...

  13. Places available**

    CERN Multimedia

    2003-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. TECHNICAL TRAINING Monique Duval Tel. 74924technical.training@cern.ch ** The number of places available may vary. Please check our Web site to find out the current availability. Places are available in the following courses: MATLAB Fundamentals and Programming Techniques (ML01) : 2 & 3.12.03 (2 days) Oracle 8i : SQL : 3 - 5.12.03 (3 days) The EDMS MTF in practice : 5.12.03 (afternoon, free of charge) Modeling Dynamic Systems with Simulink (SL01) : 8 & 9.12.03 (2 days) Signal Processing with MATLAB (SG01) : 11 & 12.12.03 (2 days) The JAVA Programming Language - l...

  14. Places available**

    CERN Multimedia

    2003-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. TECHNICAL TRAINING Monique Duval tel. 74924 technical.training@cern.ch ** The number of places available may vary. Please check our Web site to find out the current availability. Places are available in the following courses: MATLAB Fundamentals and Programming Techniques (ML01) :2 & 3.12.03 (2 days) Oracle 8i : SQL : 3 - 5.12.03 (3 days) The EDMS MTF in practice : 5.12.03 (afternoon, free of charge) Modeling Dynamic Systems with Simulink (SL01) : 8 & 9.12.03 (2 days) Signal Processing with MATLAB (SG01) : 11 & ...

  15. Places available**

    CERN Multimedia

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. TECHNICAL TRAINING Monique Duval tel. 74924 technical.training@cern.ch ** The number of places available may vary. Please check our Web site to find out the current availability. Places are available in the following courses: The JAVA Programming Language Level 1 :9 & 10.1.2004 (2 days) The JAVA Programming Language Level 2 : 11 to 13.1.2004 (3 days) Hands-on Introduction to Python Programming : 16 - 18.2.2004 (3 days - free of charge) CLEAN-2002 : Working in a Cleanroom : 10.3.2004 (afternoon - free of charge) C++ for Particle Physicists : 8 - 12.3.2004...

  16. Places available**

    CERN Document Server

    Places are available in the following courses: Hands-on Introduction to Python Programming: 11-13.08.2003 (3 days) Introduction to the CERN Engineering Data Management System (EDMS): 26.08.2003 (1 day) The CERN Engineering Data Management System (EDMS) for Engineers: 27.08.2003 (1 day) CLEAN-2002 : Travailler en salle blanche : 4.09.2003 (une demi-journée) AutoCAD 2002 - Level 1: 4, 5, 15, 16.09.2003 (2 x 2 days) AutoCAD Mechanical 6 PowerPack : 17, 18, 25, 26.09.2003 et 2, 3.10.2003 (3 x 2 journées, français) AutoCAD 2002 - niveau 1 : 23, 24, 30.09.2003 et 1.10.2003 (2 x 2 journées) Introduction to the CERN Engineering Data Management System (EDMS): 23.09.2003 (1 day) The CERN Engineering Data Management System (EDMS) for Local Administrators: 24-25.09.2003 (2 days) AutoCAD 2002 - niveau 2 : 8 et 10.10.2003 (2 journées) CLEAN-2002: Working in a Cleanroom: 23.10.2003 (half day, p.m.) ** The number of places available may vary. Please check our Web site to find out the current availabili...

  17. Places available**

    CERN Multimedia

    2003-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. TECHNICAL TRAINING Monique Duval Tel. 74924 technical.training@cern.ch ** The number of places available may vary. Please check our Web site to find out the current availability. Places are available in the following courses: JAVA 2 Enterprise Edition - Part 1 : WEB Applications : 20 & 21.11.03(2 days) FrontPage 2000 - niveau 1 : 20 & 21.11.03 (2 jours) Oracle 8i : SQL : 3 - 5.12.03 (3 days) Oracle 8i : Programming with PL/SQL : 8 - 10.12.03 (3 days) The JAVA Programming Language - leve...

  18. Places available **

    CERN Document Server

    2003-01-01

    Des places sont disponibles dans les cours suivants : Places are available in the following course : Introduction to the CERN Engineering Data Management System : 28.1.03 (1 day) AutoCAD 2002 - niveau 1 : 24, 25.2 et 3, 4.3.03 (4 jours) AutoCAD 2002 - niveau 2 : 27 & 28.2.03 (2 jours) C++ for Particle Physicists : 10 - 14.3.03 (6 X 3 hour lectures) AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 17, 18, 24 & 25.3.03 (6 jours) CLEAN-2002 : Working in a cleanroom : 25.3.03 (half-day, afternoon, free course, registration required) Formation Siemens SIMATIC /Siemens SIMATIC Training : Introduction à STEP7 /Introduction to STEP7 : 11 & 12.3.03 / 3 & 4.6.03 (2 jours/2 days) Programmation STEP7/STEP7 Programming : 31.3 - 4.4.03 / 16 - 20.6.03 (5 jours/5 days) Réseau Simatic Net /Simatic Net Network : 15 & 16.4.03 / 26 & 27.6.03 Ces cours seront donnés en français ou anglais en fonction des demandes / These courses will be given in French or English following the requests. * Etant do...

  19. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses: Hands-on Introduction to Python Programming: 11-13.08.2003(3 days) Introduction to the CERN Engineering Data Management System (EDMS): 26.08.2003 (1 day) The CERN Engineering Data Management System (EDMS) for Engineers: 27.08.2003 (1 day) CLEAN-2002 : Travailler en salle blanche : 4.09.2003 (une demi-journée) AutoCAD 2002 - Level 1: 4, 5, 15, 16.09.2003 (2 x 2 days) AutoCAD Mechanical 6 PowerPack : 17, 18, 25, 26.09.2003 et 2, 3.10.2003 (3 x 2 journées, français) AutoCAD 2002 - niveau 1 : 23, 24, 30.09.2003 et 1.10.2003 (2 x 2 journées) Introduction to the CERN Engineering Data Management System (EDMS): 23.09.2003 (1 day) The CERN Engineering Data Management System (EDMS) for Local Administrators: 24-25.09.2003 (2 days) AutoCAD 2002 - niveau 2 : 8 et 10.10.2003 (2 journées) CLEAN-2002: Working in a Cleanroom: 23.10.2003 (half day, p.m.) ** The number of places available may vary. Please ch...

  20. Places available**

    CERN Document Server

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.TECHNICAL TRAINING Monique Duval tel. 74924 technical.training@cern.ch ** The number of places available may vary. Please check our Web site to find out the current availability. Places are available in the following courses: The JAVA Programming Language Level 1 : 9 & 10.1.2004 (2 days) The JAVA Programming Language Level 2 : 11 to 13.1.2004 (3 days) LabVIEW base 1 : 25 - 27.2.2004 (3 jours) CLEAN-2002 : Working in a Cleanroom : 10.3.2004 (afternoon - free of charge) C++ for Particle Physicists : 8 - 12.3.2004 ( 6 X 4-hour sessions) LabVIEW Basics 1 : 22 - 24.3.20...

  1. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses: Conception de PCB rapides dans le flot Cadence : 11.6.03 (matin) EXCEL 2000 - level 1 : 12 & 13.6.03 (2 days) Introduction to PVSS : 16.6.03 (p.m.) Basic PVSS : 17 - 19.6.03 (3 days) Réalisation de PCB rapides dans le flot Cadence : 17.6.03 (matin) PVSS - JCOP Framework Tutorial : 20.6.03 (1 day) Programmation automate Schneider : Programmation automate Schneider TSX Premium - 2ème niveau : 24 - 27.6.03 (4 jours) - audience : toute personne qui veux maitriser la mise en uvre et la programmation des fonctions spécialisées d'un automate TSX Premium - objectifs : maitriser la mise en uvre et la programmation des fonctions spécialisées d'un automate TSX Premium Cours de sécurité : Etre TSO au CERN : Prochaines sessions : 24, 25 & 27.6.03 - 4, 5 & 7.11.03 (session de 3 jours) ** The number of places available may vary. Please check our Web site to find out the current availability. If you wish to participate in one of these courses, pl...

  2. PLACES AVAILABLE

    CERN Multimedia

    Enseignement Technique; Tél. 74924; Technical Training; Monique Duval; Tel. 74924

    2000-01-01

    Places available Places are available in the following courses:   LabView hands-on 13.11.00 4 hours LabView Basics 1 14 - 16.11.00 3 days Nouveautés de WORD 19 et 20.10.00 2 jours ACCESS 1er niveau 30 - 31.10.00 2 jours Advanced aspects of the C language 2 - 3.11.00 2 days Introduction to Oracle SQL and PL/SQL 13 - 17.11.00 5 days C++ for Particle Physicists 20 - 24.11.00 6 lectures Develop PL/SQL Program Units 20 - 22.11.00 3 days Oracle Application Server Develop Web-Based Applications with PL/SQL 27 - 28.11.00 2 days Programmation TSX Premium 1 28.11 - 1.12.00 4 jours Programmation TSX Premium 2 12 - 15.12.00 4 jours If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an “application for training” form available from your Divisional Secretariat or from your DTO (Divisional Training Offi...

  3. Places available**

    CERN Multimedia

    2003-01-01

    If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. ** The number of places available may vary. Please check our Web site to find out the current availability. Places are available in the following courses : EXCEL 2000 - niveau 1 : 20 & 22.10.03 (2 jours) CLEAN-2002 : Working in a Cleanroom (free of charge) : 23.10.03 (half day) The EDMS-MTF in practice (free of charge) :  28 -  30.10.03 (6 half-day sessions) AutoCAD 2002 - Level 1 : 3, 4, 12, 13.11.03 (4 days) LabVIEW TestStand ver. 3 : 4 & 5.11.03 (2 days) Introduction to Pspice : 4.11.03 p.m. (half-day) Hands-on Introduction to Python Programm...

  4. Sustained lobe reconnection in Saturn's magnetotail

    Science.gov (United States)

    Thomsen, M. F.; Jackman, C. M.; Mitchell, D. G.; Hospodarsky, G.; Kurth, W. S.; Hansen, K. C.

    2015-12-01

    The degree to which solar wind driving may affect Saturn's magnetosphere is not yet fully understood. We present observations that suggest that under some conditions the solar wind does govern the character of the plasma sheet in Saturn's outer magnetosphere. On 16 September 2006, the Cassini spacecraft, at a radial distance of 37 Rs near local midnight, observed a sunward flowing ion population for ~5 h, which was accompanied by enhanced Saturn Kilometric Radiation emissions. We interpret this beam as the outflow from a long-lasting episode of Dungey-type reconnection, i.e., reconnection of previously open flux containing magnetosheath material. The beam occurred in the middle of a several-day interval of SKR activity and enhanced lobe magnetic field strength, apparently caused by the arrival of a solar wind compression region with significantly higher than average dynamic pressure. The arrival of the high-pressure solar wind also marked a change in the composition of the plasma-sheet plasma, from water-group-dominated material clearly of inner-magnetosphere origin to material dominated by light-ion composition, consistent with captured magnetosheath plasma. This event suggests that under the influence of prolonged high solar wind dynamic pressure, the tail plasma sheet, which normally consists of inner-magnetospheric plasma, is eroded away by ongoing reconnection that then involves open lobe field lines. This process removes open magnetic flux from the lobes and creates a more Earth-like, Dungey-style outer plasma sheet dominantly of solar wind origin. This behavior is potentially a recurrent phenomenon driven by repeating high-pressure streams (corotating interaction regions) in the solar wind, which also drive geomagnetic storms at Earth.

  5. Rapid Reconnection and Field Line Topology

    Science.gov (United States)

    Parker, E. N.; Rappazzo, A. F.

    Rapid reconnection of magnetic fields arises where the magnetic stresses push the plasma and field so as to increase the field gradient without limit. The intent of the present writing is to show the larger topological context in which this commonly occurs. Consider an interlaced field line topology as commonly occurs in the bipolar magnetic regions on the Sun. A simple model is constructed starting with a strong uniform magnetic field B 0 in the z-direction through an infinitely conducting fluid from the end plate z = 0 to z = L with the field lines tied at both end plates. Field line interlacing is introduced by smooth continuous random turbulent mixing of the footpoints at the end plates. This configuration is well suited to be modeled with the reduced magnetohydrodynamic (MHD) equations, with the equilibria given by the solutions of the 2D vorticity equation in this case. The set of continuous solutions to the "vorticity" equation have greatly restricted topologies, so almost all interlaced field topologies do not have continuous solutions. That infinite set represents the "weak" solutions of the vorticity equation, wherein there are surfaces of tangential discontinuity (current sheets) in the field dividing regions of smooth continuous field. It follows then that current sheets are to be found throughout interlaced fields, providing potential sites for rapid reconnection. That is to say, rapid reconnection and nanoflaring are expected throughout the bipolar magnetic fields in the solar corona, providing substantial heating to the ambient gas. Numerical simulations provide a direct illustration of the process, showing that current sheets thin on fast ideal Alfvén timescales down to the smallest numerically resolved scales. The asymmetric structure of the equilibria and the interlacing threshold for the onset of singularities are discussed. Current sheet formation and dynamics are further analyzed with dissipative and ideal numerical simulations.

  6. Conservation of writhe helicity under anti-parallel reconnection

    CERN Document Server

    Laing, Christian E; Sumners, De Witt L

    2014-01-01

    Reconnection is a fundamental event in many areas of science, from the interaction of vortices in classical and quantum fluids, and magnetic flux tubes in magnetohydrodynamics and plasma physics, to the recombination in polymer physics and DNA biology. By using fundamental results in topological fluid mechanics, the helicity of a flux tube can be calculated in terms of writhe and twist contributions. Here we show that the writhe is conserved under anti-parallel reconnection. Hence, for a pair of interacting flux tubes of equal flux, if the twist of the reconnected tube is the sum of the original twists of the interacting tubes, then helicity is conserved during reconnection. Thus, any deviation from helicity conservation is entirely due to the intrinsic twist inserted or deleted locally at the reconnection site. This result has important implications for helicity and energy considerations in various physical contexts.

  7. Turbulent Reconnection in Relativistic Plasmas And Effects of Compressibility

    CERN Document Server

    Takamoto, Makoto; Lazarian, Alexandre

    2015-01-01

    We report turbulence effects on magnetic reconnection in relativistic plasmas using 3-dimensional relativistic resistive magnetohydrodynamics simulations. We found reconnection rate became independent of the plasma resistivity due to turbulence effects similarly to non-relativistic cases. We also found compressible turbulence effects modified the turbulent reconnection rate predicted in non-relativistic incompressible plasmas; The reconnection rate saturates and even decays as the injected velocity approaches to the Alfv\\'en velocity. Our results indicate the compressibility cannot be neglected when compressible component becomes about half of incompressible mode occurring when the Alfv\\'en Mach number reaches about $0.3$. The obtained maximum reconnection rate is around $0.05$ to $0.1$, which will be able to reach around $0.1$ to $0.2$ if injection scales are comparable to the sheet length.

  8. Plasmoid Instability in High-Lundquist-Number Magnetic Reconnection

    CERN Document Server

    Huang, Yi-Min

    2013-01-01

    Our understanding of magnetic reconnection in resistive magnetohydrodynamics has gone through a fundamental change in recent years. The conventional wisdom is that magnetic reconnection mediated by resistivity is slow in laminar high Lundquist ($S$) plasmas, constrained by the scaling of the reconnection rate predicted by Sweet-Parker theory. However, recent studies have shown that when $S$ exceeds a critical value $\\sim10^{4}$, the Sweet-Parker current sheet is unstable to a super-Alfv\\'enic plasmoid instability, with a linear growth rate that scales as $S^{1/4}$. In the fully developed statistical steady state of two-dimensional resistive magnetohydrodynamic simulations, the normalized average reconnection rate is approximately 0.01, nearly independent of $S$, and the distribution function $f(\\psi)$ of plasmoid magnetic flux $\\psi$ follows a power law $f(\\psi)\\sim\\psi^{-1}$. When Hall effects are included, the plasmoid instability may trigger onset of Hall reconnection even when the conventional criterion f...

  9. Turbulent magnetic reconnection in 2D and 3D

    CERN Document Server

    Lazarian, A; Vishniac, E; Kulpa-Dubel, K; Otmianowska-Mazur, K

    2010-01-01

    Magnetic field embedded in a perfectly conducting fluid preserves its topology for all time. Although ionized astrophysical objects, like stars and galactic disks, are almost perfectly conducting, they show indications of changes in topology, `magnetic reconnection', on dynamical time scales. Reconnection can be observed directly in the solar corona, but can also be inferred from the existence of large scale dynamo activity inside stellar interiors. Solar flares and gamma ray busts are usually associated with magnetic reconnection. Previous work has concentrated on showing how reconnection can be rapid in plasmas with very small collision rates. Here we present numerical evidence, based on three dimensional simulations, that reconnection in a turbulent fluid occurs at a speed comparable to the rms velocity of the turbulence, regardless of the value of the resistivity. In particular, this is true for turbulent pressures much weaker than the magnetic field pressure so that the magnetic field lines are only slig...

  10. Plasma compression in magnetic reconnection regions in the solar corona

    CERN Document Server

    Provornikova, Elena; Lukin, Vyacheslav S

    2016-01-01

    It has been proposed that particles bouncing between magnetized flows converging in a reconnection region can be accelerated by the first order Fermi mechanism. Analytical considerations of this mechanism have shown that the spectral index of accelerated particles is related to the total plasma compression within the reconnection region similarly to the case of diffusive shock acceleration mechanism. As a first step to investigate the efficiency of Fermi acceleration in reconnection regions in producing hard energy spectra of particles in the solar corona, we explore the degree of plasma compression that can be achieved at reconnection sites. In particular, we aim to determine the conditions for the strong compressions to form. Using a two-dimensional resistive MHD numerical model we consider a set of magnetic field configurations where magnetic reconnection can occur including a Harris current sheet, a force-free current sheet, and two merging flux ropes. Plasma parameters are taken to be characteristic of t...

  11. Relativistic Reconnection: an Efficient Source of Non-Thermal Particles

    CERN Document Server

    Sironi, Lorenzo

    2014-01-01

    In magnetized astrophysical outflows, the dissipation of field energy into particle energy via magnetic reconnection is often invoked to explain the observed non-thermal signatures. By means of two- and three-dimensional particle-in-cell simulations, we investigate anti-parallel reconnection in magnetically-dominated electron-positron plasmas. Our simulations extend to unprecedentedly long temporal and spatial scales, so we can capture the asymptotic state of the system beyond the initial transients, and without any artificial limitation by the boundary conditions. At late times, the reconnection layer is organized into a chain of large magnetic islands connected by thin X-lines. The plasmoid instability further fragments each X-line into a series of smaller islands, separated by X-points. At the X-points, the particles become unmagnetized and they get accelerated along the reconnection electric field. We provide definitive evidence that the late-time particle spectrum integrated over the whole reconnection r...

  12. Whistler Mode Waves in Collisionless Magnetic Reconnection

    Institute of Scientific and Technical Information of China (English)

    GUO Jun; LU Quan-Ming; WANG Shui; WANG Yu-Ming; DOU Xian-Kang

    2004-01-01

    A 21/2-dimensional electromagnetic particle-in-cell (PIC) simulation code is used to investigate the wave phenomena in the plasma sheet of collisionless magnetic reconnection. The results show that these waves have the following characteristics: they are right-hand circularity polarized, with propagation direction nearly parallel to local magnetic field, and frequency between 0.07 and 0.17 times of local electron cyclotron frequency. Therefore we conclude that such waves are Whistler waves, and their possible excitation mechanisms are also discussed.

  13. Placing knowledge

    DEFF Research Database (Denmark)

    Adriansen, Hanne Kirstine; Valentin, Karen; Nielsen, Gritt B.

    Internationalisation of higher education is premised by a seeming paradox: On the one hand, academic knowledge strives to be universal in the sense that it claims to produce generalizable, valid and reliable knowledge that can be used, critiqued, and redeveloped by academics from all over the world......; on the other hand, the rationale for strengthening mobility through internationalisation is based on an imagination of the potentials of particular locations (academic institutions). Intrigued by this tension between universality and particularity in academic knowledge production, this paper presents...... preliminary findings from a project that study internationalisation of higher education as an agent in the interrelated processes of place-making and knowledge-making. The project is based on three case-studies. In this paper, focus is on PhD students’ change of research environment. This is used as a case...

  14. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: CLEAN-2002 : Travailler en salle blanche (cours gratuit) : 13.08.2002 (matin) Introduction to the CERN Enginnering Data Management System :  27.8.02  (1 day) The CERN Engineering Data Management System for Advanced Users :  28.8.02  (1 day) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. Technical Training Monique Duval Tel.74924 monique.duval@cern.ch    

  15. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: C++ Programming Level 2 - Traps & Pitfalls:  16 - 19.7.02 (4 days) Frontpage 2000 - level 1 :  22 - 23.7.02  (2 days) Introduction à Windows 2000 au CERN : 24.7.02 (après-midi) CLEAN-2002 : Travailler en salle blanche (cours gratuit) : 13.08.2002 (matin) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. Technical Training Monique Duval Tel.74924 monique.duval@cern.ch

  16. PLACES AVAILABLE

    CERN Multimedia

    TECHNICAL TRAINING; Tel. 74460

    2001-01-01

    Places are available in the following courses: The JAVA programming language level 1: 8 - 9.2.01 (2 days) AutoCAD 2D niveau 1 : 12 - 16.2.01 (5 jours) The JAVA programming language level 2: 19 - 21.2.01 (3 days) C++ for Particle Physicists: 5 - 9.3.01 (20 hrs on 5 days) Contract Follow-up : 12.3.01 (3 heures) The JAVA programming language level 2: 12 - 14.3.01 (3 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  17. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Utilisation du simulateur Simplorer : 30.5 - 1.6.01 (3 jours) Contract Follow-up : 11.6.01 (1/2 journée) LabView hands-on : 11.6.01 F ou E (1/2 journée) LabView Base 1 : 12 - 14.6.01 (3 jours) Habilitation électrique : superviseurs: 2 sessions d'une demi-journée les 12 et 19.6.01 If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  18. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: December 2002   PCAD Schémas - Débutants :  5 & 6.12.02  (2 jours) PCAD PCB - Débutants :  9 - 11.12.02  (3 jours) FrontPage 2000 - level 1:  9 & 10.12.02  (2 days) Introduction à la CAO Cadence (cours gratuit) :  10 & 11.12.02  (2 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. Technical Training Monique Duval Tel.74924 monique.duval@cern.ch

  19. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Introduction to Perl 5 : 2 - 3.7.01 (2 days) Introduction to Databases :  3 - 4.7.01 (2 days) JAVA programming language Level 2 : 4 - 6.7.01 (3 days) Enterprise JavaBeans :  9 - 11.7.01 (3 days) Design Patterns :  10 - 12.7.01 (3 days) C++ for Particle Physicists :  23 - 27.7.01 (6 3-hour lectures) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  20. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Introduction to Databases :  3 - 4.7.01 (2 days) The JAVA programming language Level 2 : 4 - 6.7.01 (3 days) Enterprise JavaBeans :  9 - 11.7.01 (3 days) Design Patterns :  10 - 12.7.01 (3 days) C++ for Particle Physicists :  23 - 27.7.01 (6 3-hour lectures) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  1. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Introduction à PowerPoint : 24.4.01 (1 journée) Introduction to Rational Rose: 7 - 8.5.01 (2 days) Programmation TSX Premium 2 : 7 - 11.5.01 (5 jours) EXCEL : 9, 10, 16, 17.5.01 (4 jours) LabView Base 2 : 15 - 16.5.01 (2 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  2. PLACES AVAIABLE

    CERN Multimedia

    TECHNICAL TRAINING; Tel. 74460

    2001-01-01

    Places are available in the following courses: The Java programming language (Level 1) : 8 - 9.2.01 (2 days) Architecture d'automatisme : 20 - 21.2.01 (2 jours) Programmation TSX Premium 1 (Schneider) : 26.2 - 2.3.01 (5 jours) C++ for Particle Physicists : 5 - 9.3.01 (6*3 hour lectures) The Java programming language (Level 2) : 12 - 14.3.2001 (3 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  3. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Introduction à PowerPoint : 24.4.01 (1 journée) Programmation TSX Premium 2 : 7 - 11.5.01 (5 jours) EXCEL : 9, 10, 16, 17.5.01 (4 jours) LabView Base 2 :  15 - 16.5.01 (2 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  4. Strongly Driven Magnetic Reconnection in a Magnetized High-Energy-Density Plasma

    Science.gov (United States)

    Fiksel, G.; Barnak, D. H.; Chang, P.-Y.; Haberberger, D.; Hu, S. X.; Ivancic, S.; Nilson, P. M.; Fox, W.; Deng, W.; Bhattacharjee, A.; Germaschewski, K.

    2014-10-01

    Magnetic reconnection in a magnetized high-energy-density plasma is characterized by measuring the dynamics of the plasma density and magnetic field between two counter-propagating and colliding plasma flows. The density and magnetic field were profiled using the 4 ω angular filter refractometry and fast proton deflectometry diagnostics, respectively. The plasma flows are created by irradiating oppositely placed plastic targets with 1.8-kJ, 2-ns laser beams on the OMEGA EP Laser System. The two plumes are magnetized by an externally controlled magnetic field with an x-type null point geometry with B = 0 at the midplane and B = 8 T at the targets. The interaction region is pre-filled with a low-density background plasma. The counterflowing super-Alfvénic plasma plumes sweep up and compress the magnetic field and the background plasma into a pair of magnetized ribbons, which collide, stagnate, and reconnect at the midplane, allowing for the first detailed observation of a stretched current sheet in laser-driven reconnection experiments. The measurements are in good agreement with first-principles particle-in-cell simulations. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and NLUF Grant DE-SC0008655.

  5. Places disponibles*/Places available **

    CERN Document Server

    2003-01-01

    Des places sont disponibles dans les cours suivants : Places are available in the following course : WorldFIP 2003 pour utilisateurs : 11 - 14.2.03 (4 jours) AutoCAD 2002 - niveau 1 : 24, 25.2 & 3, 4.3.03 (4 jours) Introduction à Windows 2000 au CERN : 25.2.03 (1/2 journée) AutoCAD 2002 - niveau 2 : 27 & 28.2.03 (2 jours) C++ for Particle Physicists : 10 - 14.3.03 (6 X 3 hour lectures) AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 17, 18, 24 & 25.3.03 (6 jours) CLEAN-2002 : Working in a cleanroom : 2.4.03 (half-day, afternoon, free course, registration required) Formation Siemens SIMATIC /Siemens SIMATIC Training : Introduction à STEP7 /Introduction to STEP7 : 11 & 12.3.03 / 3 & 4.6.03 (2 jours/2 days) Programmation STEP7/STEP7 Programming : 31.3 - 4.4.03 / 16 - 20.6.03 (5 jours/5 days) Réseau Simatic Net /Simatic Net Network : 15 & 16.4.03 / 26 & 27.6.03 Ces cours seront donnés en français ou anglais en fonction des demandes / These courses will be given in French o...

  6. Hall MHD reconnection in cometary magnetotail

    International Nuclear Information System (INIS)

    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

  7. Reconnection brightenings in the quiet solar photosphere

    CERN Document Server

    van der Voort, Luc H M Rouppe; Vissers, Gregal J M

    2016-01-01

    We describe a new quiet-Sun phenomenon which we call "Quiet-Sun Ellerman-like Brightenings" (QSEB). QSEBs are similar to Ellerman bombs (EB) in some respects but differ significantly in others. EBs are transient brightenings of the wings of the Balmer H-alpha line that mark strong-field photospheric reconnection in complex active regions. QSEBs are similar but smaller and less intense Balmer-wing brightenings that occur in quiet areas away from active regions. In the H-alpha wing we measure typical lengths of less than 0.5 arcsec, widths of 0.21 arcsec, and lifetimes of less than a minute. We discovered them using high-quality H-alpha imaging spectrometry from the Swedish 1-m Solar Telescope (SST) and show that in lesser-quality data they cannot be distinguished from more ubiquitous facular brightenings, nor in the ultraviolet diagnostics currently available from space platforms. We add evidence from concurrent SST spectropolarimetry that QSEBs also mark photospheric reconnection events, but in quiet regions ...

  8. Particle Acceleration and Heating by Turbulent Reconnection

    Science.gov (United States)

    Vlahos, Loukas; Pisokas, Theophilos; Isliker, Heinz; Tsiolis, Vassilis; Anastasiadis, Anastasios

    2016-08-01

    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.

  9. Collisionless reconnection: magnetic field line interaction

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2012-10-01

    Full Text Available Magnetic field lines are quantum objects carrying one quantum Φ0 = 2πh/e of magnetic flux and have finite radius λm. Here we argue that they possess a very specific dynamical interaction. Parallel field lines reject each other. When confined to a certain area they form two-dimensional lattices of hexagonal structure. We estimate the filling factor of such an area. Anti-parallel field lines, on the other hand, attract each other. We identify the physical mechanism as being due to the action of the gauge potential field, which we determine quantum mechanically for two parallel and two anti-parallel field lines. The distortion of the quantum electrodynamic vacuum causes a cloud of virtual pairs. We calculate the virtual pair production rate from quantum electrodynamics and estimate the virtual pair cloud density, pair current and Lorentz force density acting on the field lines via the pair cloud. These properties of field line dynamics become important in collisionless reconnection, consistently explaining why and how reconnection can spontaneously set on in the field-free centre of a current sheet below the electron-inertial scale.

  10. Reconnection brightenings in the quiet solar photosphere

    Science.gov (United States)

    Rouppe van der Voort, Luc H. M.; Rutten, Robert J.; Vissers, Gregal J. M.

    2016-08-01

    We describe a new quiet-Sun phenomenon which we call quiet-Sun Ellerman-like brightenings (QSEB). QSEBs are similar to Ellerman bombs (EB) in some respects but differ significantly in others. EBs are transient brightenings of the wings of the Balmer Hα line that mark strong-field photospheric reconnection in complex active regions. QSEBs are similar but smaller and less intense Balmer-wing brightenings that occur in quiet areas away from active regions. In the Hα wing, we measure typical lengths of less than 0.5 arcsec, widths of 0.23 arcsec, and lifetimes of less than a minute. We discovered them using high-quality Hα imaging spectrometry from the Swedish 1-m Solar Telescope (SST) and show that, in lesser-quality data, they cannot be distinguished from more ubiquitous facular brightenings, nor in the UV diagnostics currently available from space platforms. We add evidence from concurrent SST spectropolarimetry that QSEBs also mark photospheric reconnection events, but in quiet regions on the solar surface. The movies are available in electronic form at http://www.aanda.org

  11. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: LabView Base 1 :  23 - 25.9.02  (3 jours) Object-Oriented Analysis & Design using UML:  25 - 27.9.02  (3 days) LabView DAQ (E):  26 - 27.9.02  (2 days) Introduction to Oracle 8i : SQL and PL/SQL:  7 - 11.10.02  (5 days) CLEAN-2002 : Working in a Cleanroom (free of charge):  10.10.02  (half-day, p.m.) AutoCAD 2002 - niveau 2 :  14 - 15.10.02  (2 jours) Introduction à DesignSpace :  16.10.02  (1 journée) Introduction to DesignSpace:  17.10.02  (1 day) AutoCAD 2002 - Level 1:  17, 18, 24, 25.10.02  (4 days) AutoCAD Mechanical 6 PowerPack (F) :  21, 22, 23.10 et 4, 5, 6.11.02  (6 jours) Introduction à ANSYS/Introduction to ANSYS (langue à définir suivant demande/ Language to be chosen according to demand):...

  12. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: Java 2 Enterprise Edition - Part 2: Enterprise JavaBeans:  18 - 20.9.02  (3 days) AutoCAD 2002 - niveau 1 :  19, 20, 26, 27.9.02  (4 jours) LabView Base 1 :  23 - 25.9.02  (3 jours) Object-Oriented Analysis & Design using UML:  25 - 27.9.02  (3 days) LabView DAQ (E):  26 - 27.9.02  (2 days) Introduction to Oracle 8i : SQL and PL/SQL:  7 - 11.10.02  (5 days) CLEAN-2002 : Working in a Cleanroom (free of charge):  10.10.02  (half-day, p.m.) AutoCAD 2002 - niveau 2 :  14 - 15.10.02  (2 jours) Introduction à DesignSpace :  16.10.02  (1 journée) Introduction to DesignSpace:  17.10.02  (1 day) AutoCAD 2002 - Level 1:  17, 18, 24, 25.10.02  (4 days) AutoCAD Mechanical 6 PowerPack (F) :  21, 22, 23.10 et 4, 5, 6.11....

  13. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses: PIPES-2003 - Pratique du sertissage de tubes métalliques et multicouches :26.8.03(stage pratique) The CERN EDMS for Engineers (free of charge) : 27.8.03 (1 day) CLEAN-2002 : Travailler en salle blanche (séminaire gratuit) : 4.9.03(une demi-journée) The CERN EDMS for Local Administrators (free of charge) : 24 & 25.9.03 (2 days) HeREF-2003 : Techniques de la réfrigération Hélium (cours en français avec support en anglais) : 6 - 10.10.2003 (7 demi-journées) The Java Programming Language Level 1 : 6 - 7.10.2003 (2 days) Java 2 Enterprise Edition - Part 2 : Enterprise JavaBeans : 8 - 10.10.2003 (3 days) FileMaker - niveau 1 : 9 & 10.10.03 (2 jours) EXCEL 2000 - niveau 1 : 20 & 22.10.03 (2 jours) AutoCAD 2002 - niveau 1 : 20, 21, 27, 28.10.03 (4 jours) CLEAN-2002 : Working in a Cleanroom (free of charge) : 23.10.03 (half day) AutoCAD Mechanical 6 PowerPack (E) : 23, 24, 30, 31.10 & 12, 13.11.03 (6 days) AutoCAD 2002 - niveau 2...

  14. Places available **

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : CLEAN-2002 : Working in a cleanroom (free course, registration required): 11.4.03 (half-day, afternoon, ) LabView Basics 2 : 10 - 11.4.03 (3 days) DISP-2003 - Spring II Term : Advanced Digital Signal Processing : 30.4, 7, 14, 21.5.03 (4 X 2-hour lectures) AutoCAD 2002 - niveau 1 : 29, 30.4 et 7, 8.5.03 (4 jours) Oracle iDS Reports : Build Internet Reports : 5 - 9.5.03 (5 days) AutoCAD 2002 - niveau 2 : 5 & 6.5.03 (2 jours) AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 20, 21, 27 & 28.5.03 (6 jours) Formation Siemens SIMATIC /Siemens SIMATIC Training : Introduction à STEP7 /Introduction to STEP7 : 3 & 4.6.03 (2 jours/2 days) Programmation STEP7/STEP7 Programming : 31.3 - 4.4.03 / 16 - 20.6.03 (5 jours/5 days) Réseau Simatic Net /Simatic Net Network : 15 & 16.4.03 / 26 & 27.6.03 These courses will be given in French or English following the requests. Cours de sécurité : Etre TSO au CERN : Prochaines sessions : 24, 25 & 27.6....

  15. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : DISP-2003 - Spring II Term : Advanced Digital Signal Processing : 30.4, 7, 14, 21.5.03 (4 X 2-hour lectures) Oracle iDS Reports : Build Internet Reports : 5 - 9.5.03 (5 days) LabView DAQ (language to be defined) : 8 & 9.5.03 AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 20, 21, 27 & 28.5.03 (6 jours) AutoCAD 2002 - niveau 2 : 3 & 4.6.03 (2 jours) LabView DSC (language to be defined) : 19 & 20.6.03 Siemens SIMATIC Training : Introduction to STEP7 : 3 & 4.6.03 (2 days) STEP7 Programming : 16 - 20.6.03 (5 days) Simatic Net Network : 15 & 16.4.03 / 26 & 27.6.03 (sessions of 2 days) These courses will be given in French or English following the requests. Cours de sécurité : Etre TSO au CERN : Prochaines sessions : 24, 25 & 27.6.03 - 4, 5 & 7.11.03 (session de 3 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description ...

  16. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : CLEAN-2002 : Working in a cleanroom (free course, registration required): 11.4.03 (half-day, afternoon, ) LabView Basics 2 : 10 - 11.4.03 (3 days) DISP-2003 - Spring II Term : Advanced Digital Signal Processing : 30.4, 7, 14, 21.5.03 (4 X 2-hour lectures) AutoCAD 2002 - niveau 1 : 29, 30.4 et 7, 8.5.03 (4 jours) Oracle iDS Reports : Build Internet Reports : 5 - 9.5.03 (5 days) AutoCAD 2002 - niveau 2 : 5 & 6.5.03 (2 jours) AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 20, 21, 27 & 28.5.03(6 jours) Formation Siemens SIMATIC /Siemens SIMATIC Training : Introduction à STEP7 /Introduction to STEP7 : 3 & 4.6.03 (2 jours/2 days) Programmation STEP7/STEP7 Programming : 31.3 - 4.4.03 / 16 - 20.6.03 (5 jours/5 days) Réseau Simatic Net /Simatic Net Network : 15 & 16.4.03 / 26 & 27.6.03 These courses will be given in French or English following the requests. Cours de sécurité : Etre TSO au CERN : Prochaines sessions : 24, 25 & 27.6...

  17. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : Introduction to PVSS : 10.3.03 (half-day, afternoon) CLEAN-2002 : Working in a cleanroom : 2.4.03 (half-day, afternoon, free course, registration required) LabView Basics 1 : 9 - 11.4.03 (3 days) Language to be decided. DISP-2003 - Spring II Term : Advanced Digital Signal Processing : 30.4, 7, 14, 21.5.03 (4 X 2-hour lectures). AutoCAD 2002 - niveau 1 : 29, 30.4 et 7, 8.5.03 (4 jours) AutoCAD 2002 - niveau 2 : 5 & 6.5.03 (2 jours) AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 20, 21, 27 & 28.5.03 (6 jours) Siemens SIMATIC Training: Introduction to STEP7 : 3 & 4.6.03 (2 days) STEP7 Programming : 31.3 - 4.4.03 / 16 - 20.6.03 (5 days) Simatic Net Network : 15 & 16.4.03 / 26 & 27.6.03 These courses will be given in French or English following the requests. Cours de sécurité: Etre TSO au CERN : 3 sessions sont programmées pour 2003 : 25, 26 & 28.3.03 - 24, 25 & 27.6.03 - 4, 5 & 7.11.03 (sessions de 3 jours) ** The number o...

  18. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : DISP-2003 - Spring II Term : Advanced Digital Signal Processing : 30.4, 7, 14, 21.5.03 (4 X 2-hour lectures) Programmation de pilotes périphériques : 5 - 8.5.03 (4 jours) Oracle iDS Reports : Build Internet Reports : 5 - 9.5.03 (5 days) LabView DAQ (language to be defined) : 8 & 9.5.03 AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 20, 21, 27 & 28.5.0 (6 jours) FrontPage 2000 - niveau 1 : 20 & 21.5.03 (2 jours) AutoCAD 2002 - niveau 2 : 3 & 4.6.03 (2 jours) EXCEL 2000 - niveau 1 : 10 & 11.6.03 (2 jours) EXCEL 2000 - level 1 : 12 & 13.6.03 (2 days) PowerPoint 2000 (F) : 17 & 18.6.03 (2 jours) FrontPage 2000 - niveau 2 : 19 & 20.6.03 (2 jours) LabView DSC (langue à décider/language to be defined) : 19 & 20.6.03 EXCEL 2000 - niveau 2 : 24 & 25.6.03 (2 jours) Siemens SIMATIC Training : Introduction to STEP7 : 3 & 4.6.03 (2 days) STEP7 Programming : 16 - 20.6.03 (5 days) Simatic Net Network : 26 & 27.6.03 ...

  19. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : CLEAN-2002 : Working in a cleanroom (free course, registration required) : 2.4.03 (half-day, afternoon) LabView base 1/LabView Basics 1 (Langue à définir/ language to be decided) : 9 - 11.4.03 (3 jours/3 days) DISP-2003 - Spring II Term : Advanced Digital Signal Processing : 30.4, 7, 14, 21.5.03 (4 X 2-hour lectures) AutoCAD 2002 - niveau 1 : 29, 30.4 et 7, 8.5.03 (4 jours) AutoCAD 2002 - niveau 2 : 5 & 6.5.03 (2 jours) AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 20, 21, 27 & 28.5.03(6 jours) Formation Siemens SIMATIC /Siemens SIMATIC Training : Introduction à STEP7 /Introduction to STEP7 : 3 & 4.6.03 (2 jours/2 days) Programmation STEP7/STEP7 Programming : 31.3 - 4.4.03 / 16 - 20.6.03 (5 jours/5 days) Réseau Simatic Net /Simatic Net Network : 15 & 16.4.03 / 26 & 27.6.03 These courses will be given in French or English following the requests. Cours de sécurité : Etre TSO au CERN : 3 sessions sont programmées pour 2003 : 25...

  20. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : CLEAN-2002 : Working in a cleanroom (free course, registration required): 11.4.03 (half-day, afternoon) LabView Basics 2 : 10 - 11.4.03 (3 days) DISP-2003 - Spring II Term : Advanced Digital Signal Processing : 30.4, 7, 14, 21.5.03 (4 X 2-hour lectures) AutoCAD 2002 - niveau 1 : 29, 30.4 et 7, 8.5.03 (4 jours) Oracle iDS Reports : Build Internet Reports : 5 - 9.5.03 (5 days) AutoCAD 2002 - niveau 2 : 5 & 6.5.03 (2 jours) AutoCAD Mechanical 6 PowerPack (F) : 12, 13, 20, 21, 27 & 28.5.03(6 jours) Formation Siemens SIMATIC /Siemens SIMATIC Training : Introduction à STEP7 /Introduction to STEP7 : 3 & 4.6.03 (2 jours/2 days) Programmation STEP7/STEP7 Programming : 16 - 20.6.03 (5 jours/5 days) Réseau Simatic Net /Simatic Net Network : 15 & 16.4.03 / 26 & 27.6.03 These courses will be given in French or English following the requests. Cours de sécurité : Etre TSO au CERN : Prochaines sessions : 24, 25 & 27.6.03 - 4, 5 & 7....

  1. PLACES AVAILABLE

    CERN Multimedia

    TECHNICAL TRAINING; Tel. 74460

    2001-01-01

    Places are available in the following courses: Introduction to Databases : 23 - 24.1.01 (2 days) Advanced and Modern Databases : 25 - 26.01.01 (2 days) UNIX pour non-programmeurs : 31.1 - 2.2.01 (3 jours) JAVA for non-programmers : 5 - 7.2.01 (3 days) Contract Follow-up : 12.2.01 (3 heures) Introduction to Oracle SQL and PL/SQL : 12 - 16.2.01 (5 days) AutoCAD 2D niveau I : 12 - 16.2.02 (5 jours) The JAVA programming language level 2 : 19 - 21.2.2001 (3 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  2. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74460

    2001-01-01

    Places are available in the following courses: The JAVA programming language level 1 : 22 - 23.1.01 (2 days) Introduction to Databases : 23 - 24.1.01 (2 days) EXCEL : 24 - 25.1.01  et 1 - 2.2.01 (4 jours) Advanced and Modern Databases : 25 - 26.01.01 (2 days) UNIX pour non-programmeurs : 31.1 - 2.2.01 (3 jours) JAVA for non-programmers : 5 - 7.2.01 (3 days) Publier sur le Web :  6 - 8.2.01 (3 demi-journées) Contract Follow-up : 12.2.01 (3 heures) Introduction to Oracle SQL and PL/SQL : 12 - 16.2.01 (5 days) The JAVA programming language level 2 : 19 - 21.2.01 (3 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order...

  3. PLACES AVAILABLES

    CERN Multimedia

    Technical Training; Tel. 74924

    2000-01-01

    Places are available in the following courses:   C++ for Particle Physicists 20 - 24.11.00 6 lectures CANbus 20.11.00 1 journée CANopen 21 et 22.11.00 2 jours Sécutiré dans les installations cryogéniques 21 et 22.11.00 2 demi-journées The JAVA programming language level 2 27 ­ 29.11.00 3 days Contract Follow-up 27.11.00 3 heures 1/2 Cryogénie (introduction) 4 ­ 8.12.00 ANSYS Introduction : langue a décider suivant majorité 5 ­ 7.12.00 3 jours EXCEL 7, 8, 13 et 14.12.00 4 jours Contract Follow-up 15.12.00 3 heures 1/2 If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an “application for training” form available from your Divisional Secretariat or from your DTO (Divisional Training Officer)....

  4. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Utilisation du simulateur Simplorer : 30.5 - 1.6.01 (3 jours) JAVA programming language level 1: 11-12.6.01 (2 days) LabView hands-on F ou E : 11.6.01 (1/2 journée) Comprehensive VHDL for EPLD/FPGA Design : 11 - 15.6.01 (5 days) Introduction au Langage C : 13 - 15.6.01 (3 jours) LabView Base 1 : 12 - 14.6.01 (3 jours) Habilitation électrique : superviseurs : 2 sessions d'une demi-journée les 12 et 19.6.01 Migration de LabVIEW 5 vers LabVIEW 6i Migration from LabVIEW 5 to LabVIEW 6I :  15.6.01 (1/2 journée/half-day) Introduction to Perl 5 : 2 - 3.7.01 (2 days) JAVA programming language level 2 : 4 - 6.7.01 (3 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from ...

  5. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: LabView hands-on (bilingue/bilingual): 5.11.02 (matin/morning) LabView DAQ hands-on (bilingue/bilingual):  5.11.02  (après-midi afternoon) Introduction au PC et Windows 2000 au CERN:  6 & 7.11.02  (2 jours) Oracle 8i : Access the Database with Java:  7 & 8.11.02  (2 days) AutoCAD 2002 - niveau 2:  7 & 8.11.02  (2 jours) Introduction to PVSS (free of charge):  11.11.2002 pm  (1/2 day) Basic PVSS:  12 - 14.11.02  (3 days) EXCEL 2000 - niveau 1:  12 & 13.11.02  (2 jours) CLEAN-2002: Working in a Cleanroom (English, free of charge):  13.11.2002  (afternoon) LabView Base 1 :  13 - 15.11.02  (3 jours) AutoCAD 2002 - Level 1:  14, 15, 21, 22.11.2002  (4 days) LabVIEW - Advanced:  18 - 20.11.02  (3 days) Auto...

  6. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: November 2002   Java Programming Language level 1 :  28 & 29.11.02  (2 days) December 2002   LabVIEW - DSC (English) :  2 - 3.12.02  (2 days) FileMaker (Français) :  2 - 5.12.02  (4 jours) PCAD Schémas - Débutants :  5 & 6.12.02  (2 jours) PCAD PCB - Débutants :  9 - 11.12.02  (3 jours) FrontPage 2000 - level 1:  9 & 10.12.02  (2 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. Technical Training M...

  7. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: Introduction to Oracle 8i : SQL and PL/SQL:  7 - 11.10.02  (5 days) CLEAN-2002 : Working in a Cleanroom (free of charge):  10.10.02  (half-day, p.m.) LabView Hands-on (bilingue/bilingual) : 10.10.02 (matin/morning) LabView DAQ Hands-on (bilingue/bilingual)  10.10.02 (après-midi /afternoon) Introduction à DesignSpace :  16.10.02  (1 journée) Introduction to DesignSpace:  17.10.02  (1 day) AutoCAD Mechanical 6 PowerPack (F) :  21, 22, 23.10 et 4, 5, 6.11.02  (6 jours) Introduction à ANSYS/Introduction to ANSYS (langue à définir suivant demande/ Language to be chosen according to demand):  21 - 25.10.02  (5 jours/days) HREF-2002: Helium Refrigeration Techniques (English-French, bilingual) :  21 - 25.10.2002  (7 half days) HREF-2002: Techniques de la...

  8. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: ELEC-2002 : Spring Term :  9, 11, 16, 18, 23, 25, 30.4.02 (7 * 2.5 hours) Object-Oriented Analysis & Design: 16 - 19.4.02  (4 days) The CERN Engineering Data Management System for Advanced users:  16.4.02  (1 day) Migration from AutoCAD 14 towards AutoCAD Mechanical6 PowerPack:  17 - 19.4 and 2 &3.5.02  (5 days) AutoCAD - niveau 1 : 22, 23, 29, 30.4 et 6, 7.5.02 (6 jours) LabVIEW base 1 : 22 - 24.4.02 (3 jours) CLEAN 2002 : working in a cleanroom:  24.4.02  (half-day, pm) LabVIEW DSC (F) 25 & 26.4.02 (2 jours) AutoCAD : Mise à jour AutoCAD r-14 vers 2002 : 25 & 26.4.02 (2 jours) LabVIEW Basics 2 : 13 & 14.5.02 (2 days) EXCEL 2000 - niveau 1 : 15 & 16.5.02 (2 jours) LabVIEW DAQ (F) : 15 & 16.5.02 (2 jours) EXCEL 2000 - niveau 2 : 22 & 23.5.02 (2 jours) LabVIEW Basics 1:  3 - 5.6.02&a...

  9. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: C++ for Particle Physicists :  11 - 15.3.2002  (6 * 3 hour lectures) Programming the Web for Control Applications : 11, 12, 18, 19.3.2002  (4 * 2 hour lectures) Habilitation électrique : recyclage HT/BT (Français) : 13 - 14.3.2002 (2 * 2 heures) Introduction à la CAO CADENCE : 19 & 20.3.02 (2 jours) LabVIEW base 1 : 22 - 24.4.02 (3 jours) LabVIEW DSC (F) 25 & 26.4.02 (2 jours) LabVIEW Basics 2 : 13 & 14.5.02 (2 days) LabVIEW DAQ (F) : 15 & 16.5.02 (2 jours) Cours sur la migration AutoCAD :   AutoCAD : Mise à jour AutoCAD r-14 vers 2002 (2 jours) AutoCAD Mechanical PowerPack 6 basé sur AutoCAD 2002 (5 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fil...

  10. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: Habilitation électrique : recyclage HT/BT : 11 - 15.3.2002  (2 * 2 heures) PVSS Basics :  8 - 12.4.02  (5 days) ELEC-2002 : Spring Term :  9, 11, 16, 18, 23, 25, 30.4.02 (7 * 2.5 hours) LabVIEW base 1 : 22 - 24.4.02 (3 jours) LabVIEW DSC (F) 25 & 26.4.02 (2 jours) LabVIEW Basics 2 : 13 & 14.5.02 (2 days) LabVIEW DAQ (F) : 15 & 16.5.02 (2 jours) Cours sur la migration AutoCAD :   AutoCAD : Mise à jour AutoCAD r-14 vers 2002 (2 jours) AutoCAD Mechanical PowerPack 6 basé sur AutoCAD 2002 (5 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applica...

  11. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: November 2002   Introduction to PVSS (free of charge): 11.11.02  (afternoon) EXCEL 2000 - niveau 1 :  12 & 13.11.02  (2 jours) CLEAN-2002: Working in a Cleanroom (English, free of charge):  13.11.2002  (afternoon) AutoCAD 2002 - niveau 1 :  14, 15, 21, 22.11.02  (4 jours) Hands-on Object-Oriented Design and Programming with C++:  19 - 21.11.02  (3 days)  EXCEL 2000 - niveau 2 :  25 & 26.11.02  (2 jours) FrontPage 2000 - niveau 1 :  27 & 28.11.02  (2 jours) December 2002   LabVIEW - DSC (English) :  2 - 3.12.02  (2 days) AutoCAD 2002 - niveau 2 :  2 & 3.12.02  (2 jours) FileMaker (Français) :  2 - 5.12.02  (4 jours) PCAD Schémas - Débutants :  5 & 6.12.02 ...

  12. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: Introduction to Oracle 8i : SQL and PL/SQL:  7 - 11.10.02  (5 days) CLEAN-2002 : Working in a Cleanroom (free of charge):  10.10.02  (half-day, p.m.) AutoCAD 2002 - niveau 2 :  14 - 15.10.02  (2 jours) Introduction à DesignSpace :  16.10.02  (1 journée) Introduction to DesignSpace:  17.10.02  (1 day) AutoCAD 2002 - Level 1:  17, 18, 24, 25.10.02  (4 days) AutoCAD Mechanical 6 PowerPack (F) :  21, 22, 23.10 et 4, 5, 6.11.02  (6 jours) Introduction à ANSYS/Introduction to ANSYS (langue à définir suivant demande/ Language to be chosen according to demand):  21 - 25.10.02  (5 jours/days) HREF-2002: Helium Refrigeration Techniques (English-French, bilingual) :  21 - 25.10.2002  (7 half days) HREF-2002: Techniques de la Réfri...

  13. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: The CERN Engineering Data Management System for Advanced users : 16.4.02  (1 day) Migration from AutoCAD 14 towards AutoCAD Mechanical6 PowerPack:  17 - 19.4 and 2 &3.5.02  (5 days) AutoCAD - niveau 1 : 22, 23, 29, 30.4 et 6, 7.5.02 (6 jours) LabVIEW base 1 : 22 - 24.4.02 (3 jours) CLEAN 2002 : working in a cleanroom:  24.4.02  (half-day, pm) LabVIEW DSC (F) 25 & 26.4.02 (2 jours) AutoCAD : Mise à jour AutoCAD r-14 vers 2002 : 25 & 26.4.02 (2 jours) Cotations selon les normes GPS de l'ISO : 29 - 30.4.02 (2 jours) Introduction to the CERN Engineering Data Management System:  7.5.02  (1 day) LabVIEW Basics 2: 13 & 14.5.02 (2 days) AutoCAD Mechanical 6 PowerPack (F) : 13-14, 17, 21, 27-28.5.02 (6 jours) WorldFIP - Généralités : 14.5.2002 (1/2 journée) WorldFIP - Développer avec Micr...

  14. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: ELEC-2002 : Spring Term :  9, 11, 16, 18, 23, 25, 30.4.02 (7 * 2.5 hours) Object-Oriented Analysis & Design: 16 - 19.4.02  (4 days) The CERN Engineering Data Management System for Advanced users:  16.4.02  (1 day) Migration from AutoCAD 14 towards AutoCAD Mechanical6 PowerPack:  17 - 19.4 and 2 &3.5.02  (5 days) AutoCAD - niveau 1 : 22, 23, 29, 30.4 et 6, 7.5.02 (6 jours) LabVIEW base 1 : 22 - 24.4.02 (3 jours) CLEAN 2002 : working in a cleanroom:  24.4.02  (half-day, pm) LabVIEW DSC (F) 25 & 26.4.02 (2 jours) AutoCAD : Mise à jour AutoCAD r-14 vers 2002 : 25 & 26.4.02 (2 jours) Cotations selon les normes GPS de l'ISO : 29 - 30.4.02 (2 jours) Introduction to the CERN Engineering Data Management System:  7.5.02  (1 day) LabVIEW Basics 2 : 13 & 14.5.02 (2 days) AutoCAD Mechanical 6 PowerPack (F) : 13-...

  15. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: PVSS Basics :  8 - 12.4.02  (5 days) AutoCAD : Mise à jour AutoCAD r-14 vers 2002 : 25 & 26.4.02 (2 jours) ELEC-2002 : Spring Term :  9, 11, 16, 18, 23, 25, 30.4.02 (7 * 2.5 hours) Object-Oriented Analysis & Design: 16 - 19.4.02  (4 days) Migration from AutoCAD 14 towards AutoCAD Mechanical6 PowerPack:  17 - 19.4 and 2 &3.5.02  (5 days) LabVIEW base 1 : 22 - 24.4.02 (3 jours) LabVIEW DSC (F) 25 & 26.4.02 (2 jours) LabVIEW Basics 2 : 13 & 14.5.02 (2 days) EXCEL 2000 - niveau 2 : 22 & 23.5.02 (2 jours) LabVIEW DAQ (F) : 15 & 16.5.02 (2 jours) LabVIEW Basics 1:  3 - 5.6.02  (3 days) LabVIEW DAQ (E):  6 & 7.6.02  (2 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that...

  16. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: Introduction à DesignSpace :  16.10.02  (1 journée) AutoCAD Mechanical 6 PowerPack (F) :  21, 22, 23.10 et 4, 5, 6.11.02  (6 jours) Introduction à ANSYS 21 - 25.10.02  (5 jours/days) HREF-2002: Helium Refrigeration Techniques (English-French, bilingual) :  21 - 25.10.2002  (7 half days) LabVIEW Basics 1 (English):  21 - 23.10.02  (3 days) LabVIEW Basics 2 (English):  24 & 25.10.02  (2 days) Oracle 8i : Access the Database with Java:  7 & 8.11.02  (2 days) AutoCAD 2002 - niveau 2 :  7 & 8.11.02  (2 jours) AutoCAD 2002 - Level 1:  14, 15, 21, 22.11.02  (4 days) LabVIEW - Advanced (English) :  18 - 20.11.2002  (3 days) AutoCAD 2002 - niveau 1 :  19, 20, 25, 26.11.02 (4 jours) Oracle iDS Designer: First Class:&...

  17. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: LabVIEW base 1 : 22 - 24.4.02 (3 jours) CLEAN 2002 : working in a cleanroom:  24.4.02  (half-day, pm) LabVIEW DSC (F) 25 & 26.4.02 (2 jours) AutoCAD : Mise à jour AutoCAD r-14 vers 2002 : 25 & 26.4.02 (2 jours) Cotations selon les normes GPS de l'ISO : 29 - 30.4.02 (2 jours) Introduction to the CERN Engineering Data Management System:  7.5.02  (1 day) LabVIEW Basics 2: 13 & 14.5.02 (2 days) AutoCAD Mechanical 6 PowerPack (F) : 13-14, 17, 21, 27-28.5.02 (6 jours) WorldFIP - Généralités : 14.5.2002 (1/2 journée) WorldFIP - Développer avec MicroFIP HANDLER : 14.5 - après-midi, 15.5.02 - matin (1 jour) WorldFIP - FullFIP FDM : FIP Device Manager (F) : 15.5 - après-midi, 16.5.02 - matin (1 jour) LabVIEW DAQ (F) : 15 & 16.5.02 (2 jours) EXCEL 2000 - niveau 2 : 22 & 23.5.02 (2 jours)...

  18. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: October 2002   Introduction to the CERN Engineering Data Management System (free of charge):  29.10.2002  (1 day) The CERN EDMS for Advanced users (free of charge):  30.10.2002  (1 day) November 2002   LabView hands-on (bilingue/bilingual): 5.11.02 (matin/morning) LabView DAQ hands-on (bilingue/bilingual):  5.11.02  (après-midi afternoon) Introduction au PC et Windows 2000 au CERN :  6 & 7.11.02  (2 jours) Oracle 8i : Access the Database with Java:  7 & 8.11.02  (2 days) AutoCAD 2002 - niveau 2 :  7 & 8.11.02  (2 jours) Introduction to PVSS (free of charge):  11.11.2002 pm  (1/2 day) Basic PVSS:  12 - 14.11.02  (3 days) EXCEL 2000 - niveau 1 :  12 & 13.11.02  (2 jours) CLEAN-2002: Working in a Cleanroom (English, free ...

  19. PLACES AVAILABLE

    CERN Multimedia

    Monique DUVAL

    2002-01-01

    Places are available in the following courses: LabView Basics 1 :  4 - 6.3.02  (3 days) CLEAN-2002 : Working in a Clean Room :  7.3.2002  (half day) LabView Base 2 : 11 & 12.3.02 (2 jours) C++ for Particle Physicists :  11 - 15.3.2002  (6 * 3 hour lectures) Programming the Web for Control Applications : 11, 12, 18, 19.3.2002  (4 * 2 hour lectures) Habilitation électrique : recyclage HT/BT (Français) : 13 - 14.3.2002 (2 * 2 heures) LabView Advanced :  13 - 15.3.02 (3 days) Introduction to the CERN Engineering Data Management System (EDMS) :  20.3.2002  (1 day) The CERN (EDMS) for Advanced Users :  21.3.2002  (1 day) LabVIEW DSC : 25 - 26.4.2002 (2 jours) LabVIEW DAQ : 15 - 16.5.2002 (2 jours) Cours sur la migration AutoCAD :   AutoCAD : Mise à jour AutoCAD r-14 vers 2002 (2 jours) AutoCAD Mechanical PowerPack 6 basé ...

  20. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: November 2002   LabView hands-on (bilingue/bilingual): 5.11.02 (matin/morning) LabView DAQ hands-on (bilingue/bilingual):  5.11.02  (après-midi afternoon) PCAD Schémas - Débutants :  5 & 6.11.02  (2 jours) PCAD PCB - Débutants :  9 - 11.11.02  (3 jours) Introduction au PC et Windows 2000 au CERN :  6 & 7.11.02  (2 jours) Oracle 8i : Access the Database with Java :  7 & 8.11.02  (2 days) Introduction to PVSS (free of charge):  11.11.2002 pm  (1/2 day) Basic PVSS:  12 - 14.11.02  (3 days) EXCEL 2000 - niveau 1 :  12 & 13.11.02  (2 jours) CLEAN-2002: Working in a Cleanroom (English, free of charge):  13.11.2002  (afternoon) LabView Base 1 :  13 - 15.11.02  (3 jours) AutoCAD 2002 - niveau 1 :  14, 15, 21, 22.11.02  (4 jours) LabVIEW - Advanced:  18 - 20.11.02  (3 days) Hands-on Object-Oriented Design and Programming with C++ :  19 - 21.11.02  (3 days)  LabVIEW - Basics 2:  21 - 22.11.02 ...

  1. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: November 2002   Hands-on Object-Oriented Design and Programming with C++:  19 - 21.11.02  (3 days)  December 2002   LabVIEW - DSC (English) :  2 - 3.12.02  (2 days) AutoCAD 2002 - niveau 2 :  2 & 3.12.02  (2 jours) FileMaker (Français) :  2 - 5.12.02  (4 jours) PCAD Schémas - Débutants :  5 & 6.12.02  (2 jours) PCAD PCB - Débutants :  9 - 11.12.02  (3 jours) FrontPage 2000 - level 1:  9 & 10.12.02  (2 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisiona...

  2. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses: The CERN EDMS for Local Administrators : 24 & 25.9.03 (2 days, free of charge) HeREF-2003 : Techniques de la réfrigération Hélium cours en français avec support en anglais) : 6 - 10.10.2003 (7 demi-journées) The Java Programming Language Level 1 : 6 - 7.10.2003 (2 days) Java 2 Enterprise Edition - Part 2 : Enterprise JavaBeans : 8 - 10.10.2003 (3 days) FileMaker - niveau 1 : 9 & 10.10.03 (2 jours) EXCEL 2000 - niveau 1 : 20 & 22.10.03 (2 jours) AutoCAD 2002 - niveau 1 : 20, 21, 27, 28.10.03 (4 jours) CLEAN-2002 : Working in a Cleanroom : 23.10.03 (half day, free of charge) AutoCAD 2002 - Level 1 : 3, 4, 12, 13.11.03 (4 days) AutoCAD 2002 - niveau 2 : 10 & 11.11.03 (2 jours) ACCESS 2000 - niveau 1 : 13 & 14.11.03 (2 jours) AutoCAD Mechanical 6 PowerPack (E) : 17, 18, 24, 25.11 & 1, 2.12.03 (6 days) FrontPage 2000 - niveau 1 : 20 & 21.11.03 (2 jours) MAGNE-03 : Magnétisme pour l'électrotechnique : 25 - 27.11.03 (3 jours) ...

  3. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: LabView DAQ  (F) : 7 & 8.2.02 (2 jours) Hands-on Object-Oriented Design & Programming with Java :  11 - 13.02.02 (3 days) PVSS basics :  18 - 22.2.02 (5 days) Introduction à Windows 2000 : 18.2.02 (1 demi-journée) Introduction to the CERN Engineering Data Management System :  20.2.02 (1 day) Introduction à la CAO CADENCE : 20 & 21.2.02 (2 jours) The CERN Engineering Data Management System for Advanced users :  21.2.02  (1 day) LabView Basics 1 :  4 - 6.3.02  (3 days) Introduction au VHDL et utilisation du simulateur de CADENCE : 6 & 7.3.02 (2 jours) LabView Base 2 : 11 & 12.3.02 (2 jours) C++ for Particle Physicists :  11 - 15.3.2002  (6 * 3 hour lectures) LabView Advanced :  13 - 15.3.02 (3 days) Cours sur la migration AutoCAD :   AutoCAD : Mise à...

  4. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: PVSS basics :  18 - 22.2.02 (5 days) Introduction à la CAO CADENCE : 20 & 21.2.02 (2 jours) LabView Basics 1 :  4 - 6.3.02  (3 days) Introduction au VHDL et utilisation du simulateur de CADENCE : 6 & 7.3.02 (2 jours) LabView Base 2 : 11 & 12.3.02 (2 jours) C++ for Particle Physicists :  11 - 15.3.2002  (6 * 3 hour lectures) LabView Advanced :  13 - 15.3.02 (3 days) Cours sur la migration AutoCAD :   AutoCAD : Mise à jour AutoCAD r-14 vers 2002 (2 jours) AutoCAD Mechanical PowerPack 6 basé sur AutoCAD 2002 (5 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO...

  5. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: Introduction à la CAO CADENCE : 20 & 21.2.02 (2 jours) LabView Basics 1 :  4 - 6.3.02  (3 days) Introduction au VHDL et utilisation du simulateur de CADENCE : 6 & 7.3.02 (2 jours) CLEAN-2002 : Working in a Clean Room :  7.3.2002  (1 day) LabView Base 2 : 11 & 12.3.02 (2 jours) C++ for Particle Physicists :  11 - 15.3.2002  (6 * 3 hour lectures) LabView Advanced :  13 - 15.3.02 (3 days) Cours sur la migration AutoCAD :   AutoCAD : Mise à jour AutoCAD r-14 vers 2002 (2 jours) AutoCAD Mechanical PowerPack 6 basé sur AutoCAD 2002 (5 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisiona...

  6. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: Introduction au PC et à Windows 2000 au CERN : 29 - 30.1.02 (2 jours) LabView Base 1 : 4 - 6.2.02 (3 jours) LabView DAQ  (F) : 7 & 8.2.02 (2 jours) Hands-on Object-Oriented Design & Programming with Java :  11 - 13.02.02 (3 days) PVSS basics :  18 - 22.2.02 (5 days) Introduction à Windows 2000 : 18.2.02 (1 demi-journée) Introduction to the CERN Engineering Data Management System :  20.2.02 (1 day) The CERN Engineering Data Management System for Advanced users :  21.2.02  (1 day) C++ for Particle Physicists :  11 - 15.3.2002  (6 * 3 hour lectures) Cours sur la migration AutoCAD : AutoCAD : Mise à jour AutoCAD r-14 vers 2002 (2 jours) AutoCAD Mechanical PowerPack 6 basé sur AutoCAD 2002 (5 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electr...

  7. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: LabVIEW Basics 1:  3 - 5.6.02  (3 days) AutoCAD 2002 - niveau 1 : 4, 5, 10, 11.6.02 (4 jours) PVSS Basics :  10 - 14.6.02  (5 days) Introduction to the CERN Engineering Data Management System :  11.6.02  (1 day) Java 2 Enterprise Edition - Part 2 : Enterprise JavaBeans :  11 - 13.6.02  (3 days) Introduction to Software Engineering :  11 - 12.6.02 (2 days) The CERN Engineering Data Management System for Advanced Users :  13.6.02  (1 day) AutoCAD Mechanical 6 PowerPack (F) :  13, 19 - 21, 27-28.6.02  (6 jours) The CERN Engineering Data Management System for Advanced users :  13.6.02  (1 day) The CERN Engineering Data Management System for Local Administrators :  18.6.02  (1 day) AutoCAD 2002 - niveau 2 :  24 - 25.6.02  (2 jours) Frontpage 2000 - niveau 2 :  25 - 26...

  8. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel 74924

    2002-01-01

    Places are available in the following courses: LabView hands-on : 21.01.02 (1/2 journée) LabView DAQ hands-on : 21.01.02 (1/2 journée) FileMaker Pro : 22 - 25.1.02 (4 jours) MS-Project 2000 : 24 & 25.01.02 (2 jours) Introduction au PC et à Windows 2000 au CERN : 29 - 30.1.02 (2 jours) LabView Base 1 : 4 - 6.2.02 (3 jours) LabView DAQ (E) : 7 & 8.02.02 (2 days) Hands-on Object-Oriented Design & Programming with Java : 11 - 13.02.02 (3 days) C++ for Particle Physicists : 11 - 15.3.2002 (6 * 3 hour lectures) Cours sur la migration AutoCAD : AutoCAD : Mise à jour AutoCAD r-14 vers 2002 (2 jours) AutoCAD Mechanical PowerPack 6 basé sur AutoCAD 2002 (5 jours) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO ...

  9. PLACES AVAILABLE

    CERN Multimedia

    Technical Traininf; Tel. 74924

    2001-01-01

    Places are available in the following courses: Electromagnetic Compatibility (EMC): Introduction (bilingual) :  3.12.01 (half-day) Habilitation électrique : superviseurs : 5.12.01 (1/2 journée) Introduction to the CERN Engineering Data Management System : 07.12.2001 (1 day) LabVIEW - Basics 1 :  10 - 12.12.01 (3 days) Introduction au PC et Windows 2000 : 12 & 14.12.01 (2 jours) LabVIEW - Basics 2 :  13 - 14.12.01 (2 days) Habilitation électrique : superviseurs : 17.12.2001 (1/2 journée) EXCEL 2000 - niveau 2 : 15 - 16.1.02 (2 jours) C++ Programming Level 2 - Traps and Pitfalls :  15 - 18.1.2002  (4 days) Nouveautés de WORD 2000 : 18.1.02 (1/2 journée) LabView hands-on : 21.01.02 (1/2 journée) LabView DAQ hands-on : 21.01.02 (1/2 journée) FileMaker Pro : 22 - 25.1.02 (4 jours) Introduction au PC et à Windows 2000 au CERN : 29 - 30.1....

  10. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2002-01-01

    Places are available in the following courses: LabView hands-on : 21.01.02 (1/2 journée) LabView DAQ hands-on : 21.01.02 (1/2 journée) FileMaker Pro : 22 - 25.1.02 (4 jours) MS-Project 2000 : 22, 24 & 25.01.02 (3 jours) Introduction au PC et à Windows 2000 au CERN : 29 - 30.1.02 (2 jours) LabView Base 1 : 4 - 6.2.02 (3 jours) LabView DAQ  (E) :  7 & 8.02.02 (2 days) Hands-on Object-Oriented Design & Programming with Java :  11 - 13.02.02 (3 days) PVSS basics :  11 - 15.2.02 (5 days) Introduction à Windows 2000 : 18.2.02 (1 demi-journée) Introduction to the CERN Engineering Data Management System :  20.2.02 (1 day) The CERN Engineering Data Management System for Advanced users :  21.2.02  (1 day) C++ for Particle Physicists :  11 - 15.3.2002  (6 * 3 hour lectures) Cours sur la migration AutoCAD : AutoCAD : Mise à...

  11. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel.74924

    2001-01-01

    Places are available in the following courses: Habilitation électrique : superviseurs : 5.12.01 (1/2 journée) LabVIEW - Basics 1 :  10 - 12.12.01 (3 days) Introduction au PC et Windows 2000 : 12 & 14.12.01 (2 jours) LabVIEW - Basics 2 :  13 - 14.12.01 (2 days) Habilitation électrique : superviseurs : 17.12.2001 (1/2 journée) EXCEL 2000 - niveau 2 : 15 - 16.1.02 (2 jours) Sécurité dans les installations cryogéniques: 15-17.1.2002 (2 demi-journées) C++ Programming Level 2 - Traps and Pitfalls :  15 - 18.1.2002  (4 days) ELEC-2002 Winter Term: Readout and system electronics for Physics  15.1.2002 - 7.2.2002 (8 half- days) Nouveautés de WORD 2000 : 18.1.02 (1/2 journée) LabView hands-on : 21.01.02 (1/2 journée) LabView DAQ hands-on : 21.01.02 (1/2 journée) FileMaker Pro : 22 - 25.1.02 (4 jours) Frontpage...

  12. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: LabVIEW - Basics 1 :  10 - 12.12.01 (3 days) Introduction to XML :  12 & 13.12.01 (2 days) Introduction au PC et Windows 2000 : 12 & 14.12.01 (2 jours) LabVIEW - Basics 2 :  13 - 14.12.01 (2 days) Habilitation électrique : superviseurs : 17.12.2001 (1/2 journée) MS-Project 2000 : 10 & 11.01.02 (2 jours) EXCEL 2000 - niveau 2 : 15 - 16.1.02 (2 jours) Sécurité dans les installations cryogéniques: 15-17.1.2002 (2 demi-journées) C++ Programming Level 2 - Traps and Pitfalls :  15 - 18.1.2002  (4 days) ELEC-2002 Winter Term: Readout and system electronics for Physics  15.1.2002 - 7.2.2002 (8 half- days) Nouveautés de WORD 2000 : 18.1.02 (1/2 journée) LabView hands-on : 21.01.02 (1/2 journée) LabView DAQ hands-on : 21.01.02 (1/2 journée) FileMaker Pro : 22 -...

  13. PLACES AVAILABLE

    CERN Multimedia

    Enseignement Technique; Tel. 74924

    2001-01-01

    Places are available in the following courses: MS-Project 2000 : 10 & 11.01.02 (2 jours) EXCEL 2000 - niveau 2 : 15 - 16.1.02 (2 jours) Sécurité dans les installations cryogéniques: 15-17.1.2002 (2 demi-journées) C++ Programming Level 2 - Traps and Pitfalls :  15 - 18.1.2002  (4 days) ELEC-2002 Winter Term: Readout and system electronics for Physics  15.1.2002 - 7.2.2002 (8 half- days) Nouveautés de WORD 2000 : 18.1.02 (1/2 journée) LabView hands-on : 21.01.02 (1/2 journée) LabView DAQ hands-on : 21.01.02 (1/2 journée) FileMaker Pro : 22 - 25.1.02 (4 jours) MS-Project 2000 : 24 & 25.01.02 (2 jours) Introduction au PC et à Windows 2000 au CERN : 29 - 30.1.02 (2 jours) LabView Base 1 : 4 - 6.2.02 (3 jours) LabView DAQ  (E) :  7 & 8.02.02 (2 days) Hands-on Object-Oriented Design & Programming with Java :&nbs...

  14. PLACES AVAILABLE

    CERN Document Server

    Enseignement Technique; Tél. 74924; Technical Training; Monique Duval; Tel. 74924

    2000-01-01

    Places are available in the following courses : Premiers pas avec votre PC 12 - 15.9.00 (4 demi-journées) WORD 20, 21 et 26, 27.9.2000 (4 jours) JAVA programming level 1 25 - 26.9.2000 (2 days) Gaz inflammables 1 26.9.2000 (1 journée) Advanced aspects of PERL 5 6.10.2000 (1 day) Initiation au WWW 10 - 12.10.00 (3 demi-journées) WORD : importer et manipuler des images 16.10.2000 (1 journée) FileMaker 17, 18 et 24, 25.10.00 (4 jours) Nouveautés de WORD 19 et 20.10.2000 (2 jours) ACCESS 1er niveau 30 - 31.10.00 (2 jours)Introduction à PowerPoint 6.11.00 (1 journée)Nouveautés d’EXCEL 7.11.2000(4 demi-journées)Excel 13, 14 et 20, 21.11.00 (4 jours) LabView hands-on 13.11.2000(4 hours)LabView Basics 1 14 - 16.11.2000 (3 days) MS-Project 1er niveau 14-17.11.00 (4 demi-journées) If you wish to participate in one of these courses, please discuss with your supervisor and apply elec...

  15. Places available**

    CERN Document Server

    2003-01-01

    Places are available in the following courses: CLEAN-2002 : Travailler en salle blanche (séminaire gratuit) : 4.9.03 (une demi-journée) The CERN EDMS for Local Administrators (free of charge) : 24 & 25.9.03 (2 days) HeREF-2003 : Techniques de la réfrigération Hélium (cours en français avec support en anglais) : 6 - 10.10.2003 (7 demi-journées) The Java Programming Language Level 1 : 6 - 7.10.2003 (2 days) Java 2 Enterprise Edition - Part 2 : Enterprise JavaBeans : 8 - 10.10.2003 (3 days) FileMaker - niveau 1 : 9 & 10.10.03 (2 jours) EXCEL 2000 - niveau 1 : 20 & 22.10.03 (2 jours) AutoCAD 2002 - niveau 1 : 20, 21, 27, 28.10.03 (4 jours) CLEAN-2002 : Working in a Cleanroom (free of charge) : 23.10.03 (half day) AutoCAD Mechanical 6 PowerPack (E) : 23, 24, 30, 31.10 & 12, 13.11.03 (6 days) AutoCAD 2002 - niveau 2 : 10 & 11.11.03 (2 jours)...

  16. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : The CERN EDMS for Local Administrators : 24 & 25.9.03 (2 days, free of charge) HeREF-2003 : Techniques de la réfrigération Hélium (cours en français avec support en anglais) : 6 - 10.10.2003 (7 demi-journées) The Java Programming Language Level 1 : 6 - 7.10.2003 (2 days) Java 2 Enterprise Edition - Part 2 : Enterprise JavaBeans : 8 - 10.10.2003 (3 days) FileMaker - niveau 1 : 9 & 10.10.03 (2 jours) EXCEL 2000 - niveau 1 : 20 & 22.10.03 (2 jours) AutoCAD 2002 - niveau 1 : 20, 21, 27, 28.10.03 (4 jours) CLEAN-2002 : Working in a Cleanroom : 23.10.03 (half day, free of charge) AutoCAD 2002 - Level 1 : 3, 4, 12, 13.11.03 (4 days) AutoCAD 2002 - niveau 2 : 10 & 11.11.03 (2 jours) ACCESS 2000 - niveau 1 : 13 & 14.11.03 (2 jours) AutoCAD Mechanical 6 PowerPack (E) : 17, 18, 24, 25.11 & 1, 2.12.03 (6...

  17. Places available **

    CERN Multimedia

    2003-01-01

    Places are available in the following courses: PIPES-2003 - Pratique du Sertissage de tubes métalliques et multicouches : 26.8.03 (stage pratique) The CERN Engineering Data Management System (EDMS) for Engineers : 27.8.03 (1 day, free of charge) CLEAN-2002 : Travailler en salle blanche : 4.9.03 (une demi-journée, séminaire gratuit) The CERN Engineering Data Management System (EDMS) for Local Administrators : 24 & 25.9.03 (2 days, free of charge) Siemens SIMATIC Training : Programmation STEP7 - niveau 1 : 29 - 2.10.03 (4 jours) - ouverture des inscriptions fin août Programmation STEP7 - niveau 2 : 13 - 17.10.03 (5 jours) - ouverture des inscriptions fin août Réseau Simatic Net : 22 & 23.10.03 (2 jours) - ouverture des inscriptions fin août CLEAN-2002 : Working in a Cleanroom : 23.20.03 (half day, free of charge) These courses will be given in French or Englis...

  18. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses: The CERN EDMS for Local Administrators (free of charge) : 24 & 25.9.03 (2 days) HeREF-2003 : Techniques de la réfrigération Hélium (cours en français avec support en anglais) : 6 - 10.10.2003 (7 demi-journées) The Java Programming Language Level 1 : 6 - 7.10.2003 (2 days) Java 2 Enterprise Edition - Part 2 : Enterprise JavaBeans : 8 - 10.10.2003 (3 days) FileMaker - niveau 1 : 9 & 10.10.03 (2 jours) EXCEL 2000 - niveau 1 : 20 & 22.10.03 (2 jours) AutoCAD 2002 - niveau 1 : 20, 21, 27, 28.10.03 (4 jours) CLEAN-2002 : Working in a Cleanroom (free of charge) : 23.10.03 (half day) AutoCAD Mechanical 6 PowerPack (E) : 23, 24, 30, 31.10 & 12, 13.11.03 (6 days) AutoCAD 2002 - niveau 2 : 10 & 11.11.03 (2 jours) ACCESS 2000 - niveau 1 : 13 & 14.11.03 (2 jours) FrontPage 2000 - niveau 1 : 20...

  19. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: LabView Hands-on (bilingue/bilingual - gratuit/free of charge) : 13.9.02 (a.m.) LabView DAQ Hands-on (bilingue/bilingual - gratuit/free of charge) : 13.9.02 (p.m.) AutoCAD 2002 - niveau 1 : 19, 20, 26, 27.9.02 (4 jours) LabView Base 1 : 23 - 25.9.02 (3 jours) LabView DAQ (E) : 26 - 27.9.02 (2 days) AutoCAD Mechanical 6 PowerPack (F) : 30.9, 1, 2, 9, 10, 11.10.02 (6 jours) CLEAN-2002 : Working in a Cleanroom (free of charge) : 10.10.02 (half-day, p.m.) AutoCAD 2002 - niveau 2 : 14 - 15.10.02 (2 jours) AutoCAD 2002 - Level 1 : 17, 18, 24, 25.10.02 (4 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : Technical Training or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Of...

  20. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Introduction à Windows 2000 au CERN : 2 sessions de _ journée les 24 et 25.9.01 PROFIBUS : 25 - 26.9.01 (2 jours) PROFIBUS : 27 - 28.9.01 (2 days) PowerPoint 2000 : 1 et 2.10.01 (2 jours) EXCEL 2000 - niveau 1 : 3 et 4.10.01 (2 jours) Automates et réseaux de terrain : 3 - 4.10.2001 (2 jours) PCAD Schémas - débutants : 4 - 5.10.01 (2 jours) Introduction à Outlook : 5.10.01 (1 journée) Frontpage 2000 - niveau 1 : 8 et 9.10.01 (2 jours) PCAD PCB - débutants : 8 - 10.10.01 (3 jours) C++ for Particle Physicists : 8 - 12.10.01 (6 3-hour lectures) MS-Project 2000 - niveau 1 : 15 - 18.10.01 (4 demi-journées) LabView Basics 1 :  15 - 17.10.01  (3 days) Programmation TSX Premium 1 : 15 - 19.10.01 (5 jours) WORD 2000 : importer et manipuler des images : 19.10.01 (1 journée) Programmation TSX Premium 1 : 22 - 26.10.01...

  1. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74460

    2001-01-01

    Places are available in the following courses: Introduction à PowerPoint : 26.2.01 (1 journée) Programmation TSX Premium 1 : 26.2 - 2.3.01 (5 jours) Premiers pas avec votre PC : 27.2 - 2.3.01 (4 matins) C++ for Particle Physicists :  5 - 9.3.01 (6*3 hour lectures) The CERN Engineering Data Management System for Electronic Design : 6.3.01 (1 day) The CERN Engineering Data Management System for Electronic Design : 7.3.01 (1 day) EXCEL : 6, 7 et 13, 14.3.01 (4 jours) The JAVA programming language level 2 : 12 - 14.3.01 (3 days) Nouveautés de FileMaker : 20 - 23.03.01 (4 matins) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be acc...

  2. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74460

    2001-01-01

    Places are available in the following courses: LabView Base 1 : 27-29.3.01 (3 jours) Contract Follow-up : 9.4.01 (3 heures) Introduction à PowerPoint : 24.4.01 (1 journée) Publier sur le Web : 25-27.4.01 (3 demi-journées) Programmation TSX Premium 2 : 15-16.5.01 (5 jours) LabView Base 2 : 27-29.3.01 (2 jours) Hands-on Object-oriented Analysis, Design & Programming with C++ :  23-27.4.01 (5 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at : http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.

  3. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Nouveautés d'EXCEL : 5.11.01 (1/2 journée) Introduction a Windows 2000 au CERN : 6.11.01 (1/2 journée) UNIX pour non-programmeurs : 5 - 7.11.01 (3 jours) Design Patterns :  7 - 8.11.01 (2 days) The Java programming language Level 1: 8 - 9.11.01 (2 days) Automates et réseaux de terrain : 13 & 14.11.01 (3 jours) Introduction à Windows 2000 au CERN : 12 - 14.11.01 (1/2 journée) Introduction to Windows 2000 at CERN :  14.11.01  (half-day) Introduction to PERL 5 :  15 - 16.11.01  (2 days) Introduction to C Programming :  21- 23.11.01 (3 days) Programmation TSX Premium 2 : 26 - 30.11.01 (5 jours) Contract Follow-up (F) : 26.11.01 (1/2 journée) Object-Oriented Analysis and Design :  27 - 30.11.2001  (4 days) Hands-on Object-Oriented Design and Programming with C++ :  11 - 13.12.2...

  4. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Introduction à Windows 2000 au CERN : 2 sessions de _ journée les 24 et 25.9.01 PROFIBUS : 25 - 26.9.01 (2 jours) PROFIBUS : 27 - 28.9.01 (2 days) EXCEL 2000 - niveau 1 : 3 et 4.10.01 (2 jours) Automates et réseaux de terrain : 3 - 4.10.2001 (2 jours) Introduction à Outlook : 5.10.01 (1 journée) Frontpage 2000 - niveau 1 : 8 et 9.10.01 (2 jours) C++ for Particle Physicists : 8 - 12.10.01 (6 lectures) MS-Project 2000 - niveau 1 : 15 - 18.10.01 (4 demi-journées) Programmation TSX Premium 1 : 15 - 19.10.01 (5 jours) WORD 2000 : importer et manipuler des images : 19.10.01 (1 journée) Programmation TSX Premium 1 : 22 - 26.10.01 (5 jours) UNIX pour non-programmeurs : 5 - 7.11.01 (3 jours) The Java programming language Level 1: 8 - 9.11.01 (2 days) Introduction to PERL 5 :  15 - 16.11.01  (2 days) Introduction to XML :  19 - 20.11.01 (2...

  5. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: PVSS Basics : 20 - 24.8.01 (5 days) PROFIBUS : 25 - 26.9.01 (2 jours) PROFIBUS : 27 - 28.9.01 (2 days) PCAD Schémas - débutants : 4 - 5.10.01 (2 jours) PCAD PCB - débutants : 8 - 10.10.01 (3 jours) Programming TSX Premium 1: 15 - 19.10.01 (5 days) Programmation TSX Premium 1 : 22 - 26.10.01 (5 jours) Programming TSX Premium 2: 19 - 23.11.01 (5 days) Programmation TSX Premium 2 : 26 - 30.11.01 (5 jours) The following LabView courses will be given in either English or French according to demand LabVIEW - Base 1 / LabVIEW - Basics 1 : 10 - 12.9.01 (3 jours / 3 days) LabVIEW - DAQ / LabVIEW - DAQ : 13 - 14.9.01 (2 jours / 2 days) LabVIEW - Base 1 / LabVIEW - Basics 1 : 15 - 17.10.01 (3 jours / 3 days) LabVIEW - Base 2 / LabVIEW - Basics 2 : 18 - 19.10.01 (2 jours / 2 days) LabVIEW - Base 1 / LabVIEW - Basics 1 : 12 - 14.11.01 (3 jours / 3 days) LabVIEW - DAQ / LabVIEW - DAQ : 15 - 16.11.01 (2 jours / 2...

  6. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Cadence Board Design tools : Upgrading to release 14 :  3 1-day sessions on 9, 10 & 11.10.01 MS-Project 2000 - niveau 1 : 15 - 18.10.01 (4 demi-journées) LabView Base 2 : 18 & 19.10.01 (2 jours) WORD 2000 : importer et manipuler des images : 19.10.01 (1 journée) Contract Follow-up (F) :  30.10.01 (1/2 journée) The CERN Engineering Data Management System for Electronics Design :  30.10.01 (1 day) UNIX pour non-programmeurs : 5 - 7.11.01 (3 jours) The Java programming language Level 1: 8 - 9.11.01 (2 days) LabView Base 1 : 12 - 14.11.01 (3 jours) Introduction to PERL 5 :  15 - 16.11.01  (2 days) Introduction to XML :  19 - 20.11.01 (2 days) Programming TSX Premium 1 :  19 - 23.11.01  (5 days) Introduction to C Programming :  21- 23.11.01 (3 days) The Java programming language Level 2:  26 - 28.11.01 (...

  7. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: MS-Project 2000 - niveau 1 : 15 - 18.10.01 (4 demi-journées) LabView Base 2 : 18 & 19.10.01 (2 jours) WORD 2000 : importer et manipuler des images : 19.10.01 (1 journée) Contract Follow-up (F) : 30.10.01 (1/2 journée) The CERN Engineering Data Management System for Electronics Design :  30.10.01 (1 day) UNIX pour non-programmeurs : 5 - 7.11.01 (3 jours) The Java programming language Level 1: 8 - 9.11.01 (2 days) LabView Base 1 : 12 - 14.11.01 (3 jours) Automates et réseaux de terrain : 13 & 14.11.01 (2 jours) Introduction to PERL 5 :  15 - 16.11.01  (2 days) Introduction to XML :  19 - 20.11.01 (2 days) Programming TSX Premium 1 :  19 - 23.11.01  (5 days) Introduction to C Programming :  21- 23.11.01 (3 days) The Java programming language Level 2:  26 - 28.11.01 (3 days) Programmation TSX Premium 2 : 26 ...

  8. PLACES AVAILABLES

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: PVSS Basics : 20 - 24.8.01 (5 days) PROFIBUS : 25 - 26.9.01 (2 jours) PROFIBUS : 27 - 28.9.01 (2 days) PCAD Schémas - débutants : 4 - 5.10.01 (2 jours) PCAD PCB - débutants : 8 - 10.10.01 (3 jours) Programming TSX Premium 1: 15 - 19.10.01 (5 days) Programmation TSX Premium 1 : 22 - 26.10.01 (5 jours) Programming TSX Premium 2: 19 - 23.11.01 (5 days) Programmation TSX Premium 2 : 26 - 30.11.01 (5 jours) The following LabView courses will be given in either English or French according to demand LabVIEW - Base 1 / LabVIEW - Basics 1 : 10 - 12.9.01 (3 jours / 3 days) LabVIEW - DAQ / LabVIEW - DAQ : 13 - 14.9.01 (2 jours / 2 days) LabVIEW - Base 1 / LabVIEW - Basics 1 : 15 - 17.10.01 (3 jours / 3 days) LabVIEW - Base 2 / LabVIEW - Basics 2 : 18 - 19.10.01 (2 jours / 2 days) LabVIEW - Base 1 / LabVIEW - Basics 1 : 12 - 14.11.01 (3 jours / 3 days) LabVIEW - DAQ / LabVIEW - DAQ : 15 - 16.11.01 (2 jours / 2...

  9. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : FrontPage 2000 - niveau 1 : 20 & 21.5.03 (2 jours) PIPES-2003 : Pratique du sertissage de tubes métalliques et multicouches : 21.5.03 (1 jour) Introduction à la CAO Cadence : de la saisie de schéma Concept-HDL au PCB : 20 & 22.5.03 (2 jours) AutoCAD 2002 - niveau 2 : 3 & 4.6.03 (2 jours) AutoCAD Mechanical 6 PowerPack (F) : 5, 6, 12, 13, 26, 27.6.03 (6 jours) EXCEL 2000 - niveau 1 : 10 & 11.6.03 (2 jours) Conception de PCB rapides dans le flot Cadence : 11.6.03 (matin) EXCEL 2000 - level 1 : 12 & 13.6.03 (2 days) PowerPoint 2000 (F) : 17 & 18.6.03 (2 jours) Réalisation de PCB rapides dans le flot Cadence : 17.6.03 (matin) FrontPage 2000 - niveau 2 : 19 & 20.6.03 (2 jours) LabView DSC (langue à décider/language to be defined) : 19 & 20.6.03 EXCEL 2000 - niveau 2 : 24 & 25.6.03 (2 jours) Siemens SIMATIC Training: Introduction to STEP7 : 3 & 4.6.03 (2 days) STEP7 Programming : 16 - 20.6.03 (5 days) Simatic...

  10. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: Contract Follow-up (F) : 30.10.01 (1/2 journée) The CERN Engineering Data Management System for Electronics Design :  30.10.01 (1 day) Nouveautés d'Excel 2000 : 5.11.01 (1/2 journée) UNIX pour non-programmeurs : 5 - 7.11.01 (3 jours) Introduction à Windows 2000 au CERN : 6.11.01 (1/2 journée) The Java programming language Level 1: 8 - 9.11.01 (2 days) LabView Base 1 : 12 - 14.11.01 (3 jours) LabVIEW DAQ (F) : 15 & 16.11.01 (2 jours) Automates et réseaux de terrain : 13 & 14.11.01 (2 jours) Introduction to PERL 5 :  15 - 16.11.01  (2 days) LabVIEW - DAQ : 15 - 16.11.01 (2 jours) Introduction to XML :  19 - 20.11.01 (2 days) Introduction to C Programming :  21- 23.11.01 (3 days) Programmation TSX Premium 2 : 26 - 30.11.01 (5 jours) Object-Oriented Analysis and Design :  27 - 30.11.2001 (4 days) Hands...

  11. Places available**

    CERN Multimedia

    2003-01-01

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  12. Places available**

    CERN Multimedia

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  19. 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.

  20. Simulation of turbulent magnetic reconnection in the smallscale solar wind

    Institute of Scientific and Technical Information of China (English)

    魏奉思; 胡强; R.Schwen; 冯学尚

    2000-01-01

    Some observational examples for the possible occurrence of the turbulent magnetic reconnection in the solar wind are found by analysing Helios spacecraft’s high resolution data. The phenom-ena of turbulent magnetic reconnections in small scale solar wind are simulated by introducing a third order accuracy upwind compact difference scheme to the compressible two-dimensional MHD flow. Numerical results verify that the turbulent magnetic reconnection process could occur in small scale in-terplanetary solar wind, which is a basic feature characterizing the magnetic reconnection in high-mag-netie Peynolds number ( RM = 2 000-10 000) solar wind. The configurations of the magnetic reconnection could evolve from a single X-line to a multiple X-line reconnection, exhibiting a complex picture of the formation, merging and evolution of magnetic islands, and finally the magnetic reconnection would evolve into a low-energy state. Its life-span of evolution is about one hour order of magnitude. Various magnetic and f

  1. Plasmoid Instabilities Mediated Three-Dimensional Magnetohydrodynamic Turbulent Reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yi-min [Princeton University; Guo, Fan [Los Alamos National Laboratory

    2015-07-21

    After some introductory remarks on fast reconnection in resistive MHD due to plasmoid instability, oblique tearing modes in 3D, and previous studies on 3D turbulent reconnection, the subject is presented under the following topics: 3D simulation setup, time evolution of the 3D simulation, comparison with Sweet-Parker and 2D plasmoid reconnection, and diagnostics of the turbulent state (decomposition of mean fields and fluctuations, power spectra of energy fluctuations, structure function and eddy anisotropy with respect to local magnetic field). Three primary conclusions were reached: (1) The results suggest that 3D plasmoid instabilities can lead to self-generated turbulent reconnection (evidence of energy cascade and development of inertial range, energy fluctuations preferentially align with the local magnetic field, which is one of the characteristics of MHD turbulence); (2) The turbulence is highly inhomogeneous, due to the presence of magnetic shear and outflow jets (conventional MHD turbulence theories or phenomenologies may not be applicable – e.g. scale-dependent anisotropy as predicted by Goldreich & Sridhar is not found); (3) 3D turbulent reconnection is different from 2D plasmoid-dominated reconnection in many aspects. However, in fully developed state, reconnection rates in 2D and 3D are comparable — this result needs to be further checked in higher S.

  2. Fast magnetic reconnection and particle acceleration in pair plasmas

    Science.gov (United States)

    Bessho, Naoki; Bhattacharjee, A.

    2009-11-01

    Magnetic reconnection without a guide field in both non-relativistic and relativistic regimes has been studied in pair plasmas by 2D PIC simulations. We have found that in both regimes, particle acceleration enhances reconnection rates by an interesting feedback effect. Reconnection rates in the impulsive phase become of the order of 1 when the background density in a Harris sheet equilibrium is of the order of 0.01 of the density in the current sheet. Fast reconnection becomes possible not only because of increase of the time derivative part of the inertial term in the generalized Ohm's law, but also by a positive feedback on the pressure tensor term, bootstrapped by particle acceleration that produces a reduction in the particle density in the diffusion region. In this impulsive phase, the extension of the diffusion region along the outflow region is accompanied by a broadening of the width of the current sheet in the inflow region, keeping the aspect ratio small and sustaining a large reconnection rate. The collisionless resistivity originating from non-ideal terms in the generalized Ohm's law becomes large and nearly spatially uniform along the diffusion region even after the extension of the diffusion region, and can account quantitatively for the fast reconnection rate. We will compare and contrast this with reconnection and particle acceleration in hydrogen plasmas.

  3. Privileged Girls: The Place of Femininity and Femininity in Place

    Science.gov (United States)

    Fahey, Johannah

    2014-01-01

    Constructions of femininity and attendant notions of feminism are being produced in different ways in different places around the world. This is a complicated global process that cannot be reduced to analyses that take place in nation states. This paper seeks to respond to and enhance Angela McRobbie's compelling argument about understandings…

  4. Places disponibles/Places available

    CERN Multimedia

    2004-01-01

    Si vous désirez participer à l'un des cours suivants, veuillez en discuter avec votre superviseur et vous inscrire électroniquement en direct depuis les pages de description des cours dans le Web que vous trouvez à l'adresse : http://www.cern.ch/Training/ ou remplissez une « demande de formation » disponible auprès du Secrétariat de votre Division ou de votre DTO (Délégué divisionnaire à la formation). Les places seront attribuées dans l'ordre de réception des inscriptions. If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Off...

  5. New 3D vision of magnetic reconnection revealed

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ An international consortium led by astronomers from CAS and Peking University recently made the first satellite observation of the full three-dimensional (3D) geometry structure of magnetic reconnection, a process whereby the lines of a complex magnetic field break and reconnect to alter its structure drastically. Their work was published in the September issue of Nature Physics. Experts say that this pioneering discovery will help construct theoretical models of magnetic reconnection, a universal phenomenon in space related to star formation, solar explosions and the entry of solar wind energy into the near-Earth environment.

  6. 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.

  7. Helicity conservation under quantum reconnection of vortex rings

    CERN Document Server

    Zuccher, Simone

    2016-01-01

    Here we show that under quantum reconnection, simulated by using the three-dimensional Gross- Pitaevskii equation, self-helicity of a system of two interacting vortex rings remains conserved. By resolving the fine structure of the vortex cores, we demonstrate that total length of the vortex system reaches a maximum at the reconnection time, while both writhe helicity and twist helicity remain separately unchanged throughout the process. Self-helicity is computed by two independent methods, and topological information is based on the extraction and analysis of geometric quantities such as writhe, total torsion and intrinsic twist of the reconnecting vortex rings.

  8. Analyses of Simulated Reconnection-Driven Solar Polar Jets

    Science.gov (United States)

    Roberts, M. A.; Uritsky, V. M.; Karpen, J. T.; DeVore, C. R.

    2014-12-01

    Solar polar jets are observed to originate in regions within the open field of solar coronal holes. These so called "anemone" regions are generally accepted to be regions of opposite polarity, and are associated with an embedded dipole topology, consisting of a fan-separatrix and a spine line emanating from a null point occurring at the top of the dome shaped fan surface. Previous analysis of these jets (Pariat et al. 2009,2010) modeled using the Adaptively Refined Magnetohydrodynamics Solver (ARMS) has supported the claim that magnetic reconnection across current sheets formed at the null point between the highly twisted closed field of the dipole and open field lines surrounding it releases the energy necessary to drive these jets. However, these initial simulations assumed a "static" environment for the jets, neglecting effects due to gravity, solar wind and the expanding spherical geometry. A new set of ARMS simulations taking into account these additional physical processes was recently performed. Initial results are qualitatively consistent with the earlier Cartesian studies, demonstrating the robustness of the underlying ideal and resistive mechanisms. We focus on density and velocity fluctuations within a narrow radial slit aligned with the direction of the spine of the jet, as well as other physical properties, in order to identify and refine their signatures in the lower heliosphere. These refined signatures can be used as parameters by which plasma processes initiated by these jets may be identified in situ by future missions such as Solar Orbiter and Solar Probe Plus.

  9. Distributed Active Synchronization Strategy for Microgrid Seamless Reconnection to the Grid under Unbalance and Harmonic Distortion

    DEFF Research Database (Denmark)

    Tang, Fen; Guerrero, Josep M.; Vasquez, Juan Carlos;

    2015-01-01

    converters, the synchronization process is quite different compared to the quasi-synchronism control in conventional power systems. Firstly, in order to address this concern, the microgrid synchronization criteria are derived. Based on these criteria, a novel distributed active synchronization strategy...... is proposed, which takes into account not only the fundamental component but also positive and negative sequences of the harmonic components. This way a seamless reconnection to the main grid can be performed. The proposed method is implemented in the secondary control level of a hierarchical control...

  10. Taking antacids

    Science.gov (United States)

    ... heart disease. You are on a low-sodium diet. You are already taking calcium. You are taking other medicines every day. You have had kidney stones. Alternate Names Heartburn - self-care References Ferrandino MN, ...

  11. The formation and stability of Petschek reconnection

    International Nuclear Information System (INIS)

    A combined analytical and numerical study of magnetic reconnection in two-dimensional resistive magnetohydrodynamics is carried out by using different explicit spatial variations of the resistivity. A special emphasis on the existence of stable/unstable Petschek's solutions is taken, comparing with the recent analytical model given by Forbes et al. [Phys. Plasmas 20, 052902 (2013)]. Our results show good quantitative agreement between the analytical theory and the numerical solutions for a Petschek-type solution to within an accuracy of about 10% or better. Our simulations also show that if the resistivity profile is relatively flat near the X-point, one of two possible asymmetric solutions will occur. Which solution occurs depends on small random perturbations of the initial conditions. The existence of two possible asymmetric solutions, in a system which is otherwise symmetric, constitutes an example of spontaneous symmetry breaking

  12. Reconnection in Spheromak formation and sustainment

    International Nuclear Information System (INIS)

    The Spheromak is a magnetic confinement device that is being explored in both the US and Japanese fusion programs. It is a member of the Compact Torus family of magnetic structures characterized by a set of closed, nested toroidal flux surfaces but without any coils, transformer cores, etc. protruding through the hole in the torus. The Speromak is closely elated to the Reversed Field Pinch (RFP) in that most of the magnetic field is produced by plasma currents flowing along the magnetic field lines (a near force free field) rather than by external coils. The Spheromak has magnetic field components of comparable strength in both the toroidal (azimuthal) and poloidal (in the plane perpendicular to the azimuthal unit vector) directions. The large internal magnetic energy in the Spheromak makes it rich in magnetohydrodynamic phenomena and reconnection, in particular, plays an important role in the formation, resistive decay and instability processes

  13. Particle Acceleration and Heating by Turbulent Reconnection

    CERN Document Server

    Vlahos, Loukas; Isliker, Heinz; Tsiolis, Vassilios; Anastasiadis, Anastasios

    2016-01-01

    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 {\\bf scatterers} (i.e.\\ magnetic clouds or current sheets). In particular, we study how test particles respond inside this collection of scatterers. We study the energy gain of individual particles, the evolution of their energy distribution, their escape time distribution and we determine the transport coefficients from the particle dynamics. We have shown that our model describes very well the second order Fermi energization of non relativistic plasmas in open or periodic numerical boxes, when using magnetic clouds as scatterers. Replacing the "magnetic clouds" with current sheets, we have proven that the processes are much more efficient and particle heating and acceleration depends on...

  14. 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. PMID:19407194

  15. GRBs from Magnetic Reconnection: Variability and Robustness of Lightcurves

    CERN Document Server

    Granot, Jonathan

    2016-01-01

    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 lightcurves are independent of their direction distribution within this layer. This renders previous results for a delta-function velocity-direction distribution (Beniamini & Granot 2016) applicable to a much more general class of reconnection models, which are suggested by numerica...

  16. 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. PMID:27174677

  17. Physical Conditions in the Reconnection Layer in Pulsar Magnetospheres

    CERN Document Server

    Uzdensky, Dmitri A

    2012-01-01

    The magnetosphere of a rotating pulsar naturally develops a current sheet beyond the light cylinder (LC). Magnetic reconnection in this current sheet 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 an 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 c...

  18. Fast collisionless reconnection and electron heating in strongly magnetized plasmas

    CERN Document Server

    Loureiro, N F; Zocco, A

    2013-01-01

    Magnetic reconnection in strongly magnetized (low-beta), weakly collisional plasmas is investigated using a novel fluid-kinetic model [Zocco & Schekochihin, Phys. Plasmas 18, 102309 (2011)] which retains non-isothermal electron kinetics. It is shown that electron heating via Landau damping (linear phase mixing) is the dominant dissipation mechanism. In time, electron heating occurs after the peak of the reconnection rate; in space, it is concentrated along the separatrices of the magnetic island. For sufficiently large systems, the peak reconnection rate is $cE_{max}\\approx 0.2v_AB_{y,0}$, where $v_A$ is the Alfv\\'en speed based on the reconnecting field $B_{y,0}$. The island saturation width is the same as in MHD models except for small systems, when it becomes comparable to the kinetic scales.

  19. Relating reconnection rate, exhaust structure and effective resistivity

    International Nuclear Information System (INIS)

    The magnetic reconnection structure consists of a central diffusion region (CDR) and a cone or wedge shaped reconnection exhaust containing accelerated plasma flows and electromagnetic fluctuations. We predict here the relationship among the exhaust half-cone angle (θe), the half width (w) of the CDR, the outflow velocity Vo, and the effective resistivity (ηeff), which includes the effects of all the nonideal terms in the generalized Ohm's law. The effective resistivity is defined as the ratio of reconnection electric field Erec to the current density Jy at the X point and it essentially represents the loss of momentum from the current-carrying plasma particles due to scattering by waves, their inertia or outflux from the CDR. The relation is checked against relevant results previously reported from laboratory experiments, space observations, and simulations, showing excellent agreement. The relation can be used for estimating the ad-hoc effective resistivity often used in magnetohydrodynamic modeling of reconnection

  20. Total magnetic reconnection during a tokamak major disruption

    International Nuclear Information System (INIS)

    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

  1. Overlapping cusp ion injections: An explanation invoking magnetopause reconnection

    OpenAIRE

    Lockwood, Mike

    1995-01-01

    An explanation of overlapping cusp ion injections is presented using the pulsating cusp model of the effects of magnetopause reconnection. It is shown that two populations of cusp ions, covering separated energy ranges, can be seen simultaneously by low- or mid-altitude satellites because of the combined effect of the acceleration and the straightening of newly-opened field lines as they evolve away from the reconnection site. Observations of such signatures, recently reported in data from th...

  2. Universal Reconnection of Non-Abelian Cosmic Strings

    CERN Document Server

    Eto, M; Marmorini, G; Nitta, M; Ohashi, K; Vinci, W; Eto, Minoru; Hashimoto, Koji; Marmorini, Giacomo; Nitta, Muneto; Ohashi, Keisuke; Vinci, Walter

    2006-01-01

    We show that local/semilocal strings in Abelian/non-Abelian gauge theories with critical couplings always reconnect classically in collision, by using moduli space approximation. The moduli matrix formalism explicitly identifies a well-defined set of the vortex moduli parameters. Our analysis of generic geodesic motion in terms of those shows right-angle scattering in head-on collision of two vortices, which is known to give the reconnection of the strings.

  3. 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.

  4. Electron Whistler Mode Waves Associated with Collisionless Magnetic Reconnection

    Institute of Scientific and Technical Information of China (English)

    GUO Jun; YU Bin; GUO Guang-Hai; ZHAO Bo

    2011-01-01

    @@ The results of particle-in-cell (PIC) simulations are presented on the evolution of the electron whistler waves during the collisionless magnetic reconnection.The simulation results show that the electron whistler waves with frequency higher than the lower hybrid frequency are found to occur in the electrons outflow region.Moreover, the present results indicate that these electron whistler waves with high-frequency in the region greater than an ion inertial scale of the x-line are irrelevant to the fast reconnection, but are generated as a result of the reconnection processes.%The results of particle-in-cell (PIC) simulations are presented on the evolution of the electron whistler waves during the collisionless magnetic reconnection. The simulation results show that the electron whistler waves with frequency higher than the lower hybrid frequency are found to occur in the electrons outflow region. Moreover,the present results indicate that these electron whistler waves with high-frequency in the region greater than an ion inertial scale of the x-line are irrelevant to the fast reconnection, but are generated as a result of the reconnection processes.

  5. X-Point Reconnection from Shear Driving in Kinetic Simulations

    Science.gov (United States)

    Black, C.; Antiochos, S. K.; DeVore, C. R.; Germaschewski, K.; Bessho, N.; Karpen, J. T.

    2014-12-01

    The explosive energy release in solar eruptive phenomena such as CMEs/eruptive flares and coronal jets is believed to be due to magnetic reconnection. Magnetic free energy builds up slowly in the corona due to footpoint stressing by the photospheric motions. Along with the free energy, current sheets build up at coronal nulls, which eventually triggers fast reconnection and explosive energy release. This basic scenario has been modeled extensively by MHD simulations and applied to both CMEs/eruptive flares and jets, but the reconnection itself is well-known to be due to kinetic processes. Consequently, it is imperative that shear-driven X-point reconnection be modeled in a fully kinetic system so as to test and guide the MHD results. In MHD simulations, the application of a magnetic-field shear at the system boundary is a trivial matter, but this is definitely not the case for a kinetic system, because the electric currents need to be fully consistent with all the mass motions. We present the first results of reconnection in a 2D X-Point geometry due to a velocity shear driver perpendicular to the plane of reconnection. We compare the results to high-resolution MHD simulations and discuss the implications for coronal activity.

  6. Reconnection dynamics with secondary tearing instability in compressible Hall plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Z. W., E-mail: zwma@zju.edu.cn; Wang, L. C.; Li, L. J. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)

    2015-06-15

    The dynamics of a secondary tearing instability is systematically investigated based on compressible Hall magnetohydrodynamic. It is found that in the early nonlinear phase of magnetic reconnection before onset of the secondary tearing instability, the geometry of the magnetic field in the reconnection region tends to form a Y-type structure in a weak Hall regime, instead of an X-type structure in a strong Hall regime. A new scaling law is found that the maximum reconnection rate in the early nonlinear stage is proportional to the square of the ion inertial length (γ∝d{sub i}{sup 2}) in the weak Hall regime. In the late nonlinear phase, the thin elongated current sheet associated with the Y-type geometry of the magnetic field breaks up to form a magnetic island due to a secondary tearing instability. After the onset of the secondary tearing mode, the reconnection rate is substantially boosted by the formation of the X-type geometries of magnetic field in the reconnection regions. With a strong Hall effect, the maximum reconnection rate linearly increases with the increase of the ion inertial length (γ∝d{sub i})

  7. Reconnection dynamics with secondary tearing instability in compressible Hall plasmas

    International Nuclear Information System (INIS)

    The dynamics of a secondary tearing instability is systematically investigated based on compressible Hall magnetohydrodynamic. It is found that in the early nonlinear phase of magnetic reconnection before onset of the secondary tearing instability, the geometry of the magnetic field in the reconnection region tends to form a Y-type structure in a weak Hall regime, instead of an X-type structure in a strong Hall regime. A new scaling law is found that the maximum reconnection rate in the early nonlinear stage is proportional to the square of the ion inertial length (γ∝di2) in the weak Hall regime. In the late nonlinear phase, the thin elongated current sheet associated with the Y-type geometry of the magnetic field breaks up to form a magnetic island due to a secondary tearing instability. After the onset of the secondary tearing mode, the reconnection rate is substantially boosted by the formation of the X-type geometries of magnetic field in the reconnection regions. With a strong Hall effect, the maximum reconnection rate linearly increases with the increase of the ion inertial length (γ∝di)

  8. Critical Differences of Asymmetric Magnetic Reconnection from Standard Models

    Science.gov (United States)

    Nitta, S.; Wada, T.; Fuchida, T.; Kondoh, K.

    2016-09-01

    We have clarified the structure of asymmetric magnetic reconnection in detail as the result of the spontaneous evolutionary process. The asymmetry is imposed as ratio k of the magnetic field strength in both sides of the initial current sheet (CS) in the isothermal equilibrium. The MHD simulation is carried out by the HLLD code for the long-term temporal evolution with very high spatial resolution. The resultant structure is drastically different from the symmetric case (e.g., the Petschek model) even for slight asymmetry k = 2. (1) The velocity distribution in the reconnection jet clearly shows a two-layered structure, i.e., the high-speed sub-layer in which the flow is almost field aligned and the acceleration sub-layer. (2) Higher beta side (HBS) plasma is caught in a lower beta side plasmoid. This suggests a new plasma mixing process in the reconnection events. (3) A new large strong fast shock in front of the plasmoid forms in the HBS. This can be a new particle acceleration site in the reconnection system. These critical properties that have not been reported in previous works suggest that we contribute to a better and more detailed knowledge of the reconnection of the standard model for the symmetric magnetic reconnection system.

  9. The local dayside reconnection rate for oblique interplanetary magnetic fields

    CERN Document Server

    Komar, Colin M

    2016-01-01

    We present an analysis of local properties of magnetic reconnection at the dayside magnetopause for various interplanetary magnetic field (IMF) orientations in global magnetospheric simulations. This has heretofore not been practical because it is difficult to locate where reconnection occurs for oblique IMF, but new techniques make this possible. The approach is to identify magnetic separators, the curves separating four regions of differing magnetic topology, which map the reconnection X-line. The electric field parallel to the X-line is the local reconnection rate. We compare results to a simple model of local two-dimensional asymmetric reconnection. To do so, we find the plasma parameters that locally drive reconnection in the magnetosheath and magnetosphere in planes perpendicular to the X-line at a large number of points along the X-line. The global magnetohydrodynamic simulations are from the three-dimensional Block-Adaptive, Tree Solarwind Roe-type Upwind Scheme (BATS-R-US) code with a uniform resisti...

  10. Properties of GRB light curves from magnetic reconnection

    Science.gov (United States)

    Beniamini, Paz; Granot, Jonathan

    2016-07-01

    The energy dissipation mechanism within gamma-ray burst (GRB) outflows, driving their extremely luminous prompt γ-ray emission is still uncertain. The leading candidates are internal shocks and magnetic reconnection. While the emission from internal shocks has been extensively studied, that from reconnection still has few quantitative predictions. We study the expected prompt-GRB emission from magnetic reconnection and compare its temporal and spectral properties to observations. The main difference from internal shocks is that for reconnection one expects relativistic bulk motions with Lorentz factors Γ'≳ a few in the jet's bulk frame. We consider such motions of the emitting material in two antiparallel directions (e.g. of the reconnecting magnetic-field lines) within an ultrarelativistic (with Γ ≫ 1) thin spherical reconnection layer. The emission's relativistic beaming in the jet's frame greatly affects the light curves. For emission at radii R0 tracking (for Γ' > 2). However, the relativistic turbulence mode is more likely to be relevant for the prompt sub-MeV emission and can naturally account also for the peak luminosity - peak frequency correlation.

  11. ‘We are a community [but] that takes a certain amount of energy’: Exploring shared visions, social action, and resilience in place-based community-led energy initiatives

    International Nuclear Information System (INIS)

    Highlights: • We engage with conceptual characteristics of 3 community-led energy case studies. • We examine data from interviews to explore the issues community energy groups face. • Shared visions, social action and social resilience are important to community energy. • Creating and maintaining shared visions, social action and social resilience is extremely challenging. - Abstract: In UK energy policy, community-led energy initiatives are increasingly being imbued with transformative power to facilitate low carbon transitions. The ways that such expectations for communities are manifesting in practice remains, however, relatively poorly understood. In particular, key conceptual developments in unpacking what constitutes ‘community’ that highlight the significance of ‘place’ along with important characteristics, such as shared visions, collective social action, and resilience, have yet to be comprehensively explored in the context of community-led energy initiatives. This paper uses an interpretive stance to engage with these conceptual ideas about community and provides insights into the nature of community and its meaning for developing energy-related initiatives and realising the wider goals of energy policy. The paper draws on data from in-depth qualitative, longitudinal interviews undertaken in two residential communities and one purely workplace-based community, which are engaged in community energy initiatives. We argue that there are difficulties and ambiguities in creating shared visions, achieving social action, and developing resilience that are related to the specificities of community in place, but that all three characteristics are likely to be important for the making of sustainable places

  12. Take the Floor

    OpenAIRE

    Godts, Marc

    2014-01-01

    A Closed Circuit Projection, projecting the Floor on the Wall Proposition to exhibit the floor on which the conference takes place. Example of such an installation by means of a closed circuit projection that captures and streams the conference floor to project it on one of the walls of the conference. Like a mirror, installing a delay, and by means of that delay, a reflection, allowing us to see us, take, occupy and share the floor.

  13. In Place of Fishing

    DEFF Research Database (Denmark)

    Ounanian, Kristen

    2016-01-01

    the imposition of transferable catch shares, this research takes a holistic approach to studying coastal communities. This study focuses on instances of transition from a greater presence of the fishing industry to new configurations of fisheries, maritime sectors, and tourism. Situated in places in......, affecting certain segments of the community more severely than others. In addition, the transition to tourism dependence holds a somewhat precarious future for coastal communities in temperate areas. In some cases, heritage and community identity remain strongly connected to the surviving fishing industry...

  14. Holography of D-Brane Reconnection

    CERN Document Server

    Berg, M; Samtleben, H; Berg, Marcus; Hohm, Olaf; Samtleben, Henning

    2007-01-01

    Gukov, Martinec, Moore and Strominger found that the D1-D5-D5' system with the D5-D5' angle at 45 degrees admits a deformation "rho" preserving supersymmetry. Under this deformation, the D5-branes and D5'-branes reconnect along a single special Lagrangian manifold. We construct the near-horizon limit of this brane setup (for which no supergravity solution is currently known), imposing the requisite symmetries perturbatively in the deformation rho. Reducing to the three-dimensional effective gauged supergravity, we compute the scalar potential and verify the presence of a deformation with the expected properties. We compute the conformal dimensions as functions of rho. This spectrum naturally organizes into N=3 supermultiplets, corresponding to the 3/16 preserved by the brane system. We give some remarks on the symmetric orbifold CFT for Q_D5=Q_D5', outline the computation of rho-deformed correlators in this theory, and probe computations in our rho-deformed background.

  15. Magnetohydrodynamic Turbulence and Reconnection in the Magnetotail

    Science.gov (United States)

    El-Alaoui, Mostafa; Richard, Robert L.; Ashour-Abdalla, Maha; Goldstein, Melvyn L.; Walker, Raymond J.

    2011-01-01

    We have used a global MHD simulation with high spatial resolution to investigate the origin and properties of turbulence in the plasma sheet. In this simulation we imposed a steady southward IMF with a magnitude of 5 nT at the upstream simulation boundary for more than three hours followed by ninety minutes of northward IMF of the same magnitude. The solar wind number density was 20 cm-3, the thermal pressure was 20 pPa, and the velocity was 500 km/s in the x direction. The moderately high dynamic pressure confined the magnetotail to the high-grid resolution region. Even for these nominal solar wind parameters and steady driving the plasma sheet became turbulent. The power spectral densities and probability distribution functions computed from the simulations were comparable to those obtained from spacecraft observations. The largest scale vortices were associated with reconnection outflows and, in the southward IMF case, with the diversion of high speed flows in the near-Earth region. Both time and space domain analyses revealed that there were three scales present, the large scale of the driving processes, the intermediate inertial scale and the dissipative scale.

  16. Kinetic Vlasov Simulations of collisionless magnetic Reconnection

    CERN Document Server

    Schmitz, H

    2006-01-01

    A fully kinetic Vlasov simulation of the Geospace Environment Modeling (GEM) Magnetic Reconnection Challenge is presented. Good agreement is found with previous kinetic simulations using particle in cell (PIC) codes, confirming both the PIC and the Vlasov code. In the latter the complete distribution functions $f_k$ ($k=i,e$) are discretised on a numerical grid in phase space. In contrast to PIC simulations, the Vlasov code does not suffer from numerical noise and allows a more detailed investigation of the distribution functions. The role of the different contributions of Ohm's law are compared by calculating each of the terms from the moments of the $f_k$. The important role of the off--diagonal elements of the electron pressure tensor could be confirmed. The inductive electric field at the X--Line is found to be dominated by the non--gyrotropic electron pressure, while the bulk electron inertia is of minor importance. Detailed analysis of the electron distribution function within the diffusion region revea...

  17. Kinetic Vlasov simulations of collisionless magnetic reconnection

    Science.gov (United States)

    Schmitz, H.; Grauer, R.

    2006-09-01

    A fully kinetic Vlasov simulation of the Geospace Environment Modeling Magnetic Reconnection Challenge is presented. Good agreement is found with previous kinetic simulations using particle in cell (PIC) codes, confirming both the PIC and the Vlasov code. In the latter the complete distribution functions fk (k=i,e) are discretized on a numerical grid in phase space. In contrast to PIC simulations, the Vlasov code does not suffer from numerical noise and allows a more detailed investigation of the distribution functions. The role of the different contributions of Ohm's law are compared by calculating each of the terms from the moments of the fk. The important role of the off-diagonal elements of the electron pressure tensor could be confirmed. The inductive electric field at the X line is found to be dominated by the nongyrotropic electron pressure, while the bulk electron inertia is of minor importance. Detailed analysis of the electron distribution function within the diffusion region reveals the kinetic origin of the nongyrotropic terms.

  18. Observational Signatures of Magnetic Reconnection in the Extended Corona

    Science.gov (United States)

    Savage, Sabrina; West, Matthew; Seaton, Daniel B.; Kobelski, Adam

    2016-05-01

    Observational signatures of reconnection have been studied extensively in the lower corona for decades, successfully providing insight into energy release mechanisms in the region above post-flare arcade loops and below 1.5 solar radii. During large eruptive events, however, energy release continues to occur well beyond the presence of reconnection signatures at these low heights. Supra-arcade downflows (SADs) and downflowing loops (SADLs) are particularly useful measures of continual reconnection in the corona as they may indicate the presence and path of retracting post-reconnection loops. SADs and SADLs have been faintly observed up to 18 hours beyond the passage of corona mass ejections through the SOHO/LASCO field of view, but a recent event from 2014 October 14 associated with giant arches provides very clear observations of these downflows for days after the initial eruption. We report on this unique event and compare these findings with observational signatures of magnetic reconnection in the extended corona for more typical eruptions.

  19. Orientation of the X-line in asymmetric magnetic reconnection

    Science.gov (United States)

    Aunai, N.; Hesse, M.; Lavraud, B.; Dargent, J.; Smets, R.

    2016-08-01

    > Magnetic reconnection can occur in current sheets separating magnetic fields sheared by any angle and of arbitrarily different amplitudes. In such asymmetric and non-coplanar systems, it is not yet understood what the orientation of the X-line will be. Studying how this orientation is determined locally by the reconnection process is important to understand systems such as the Earth magnetopause, where reconnection occurs in regions with large differences in upstream plasma and field properties. This study aims at determining what the local X-line orientation is for different upstream magnetic shear angles in an asymmetric set-up relevant to the Earth's magnetopause. We use two-dimensional hybrid simulations and vary the simulation plane orientation with regard to the fixed magnetic field profile and search for the plane maximizing the reconnection rate. We find that the plane defined by the bisector of upstream fields maximizes the reconnection rate and this appears not to depend on the magnetic shear angle, domain size or upstream plasma and asymmetries.

  20. 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.

  1. 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.

    2016-06-01

    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 ~150 ms 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 ~0.3-3 mV/m reconnection electric fields separated by ~5-10 s, resulting in average and peak normalized dayside reconnection rates of ~0.02 and ~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.

  2. On the characterization of magnetic reconnection in global MHD simulations

    Directory of Open Access Journals (Sweden)

    T. V. Laitinen

    2006-11-01

    Full Text Available The conventional definition of reconnection rate as the electric field parallel to an x-line is problematic in global MHD simulations for several reasons: the x-line itself may be hard to find in a non-trivial geometry such as at the magnetopause, and the lack of realistic resistivity modelling leaves us without reliable non-convective electric field. In this article we describe reconnection characterization methods that avoid those problems and are practical to apply in global MHD simulations. We propose that the reconnection separator line can be identified as the region where magnetic field lines of different topological properties meet, rather than by local considerations. The global convection associated with reconnection is then quantified by calculating the transfer of mass, energy or magnetic field across the boundary of closed and open field line regions. The extent of the diffusion region is determined from the destruction of electromagnetic energy, given by the divergence of the Poynting vector. Integrals of this energy conversion provide a way to estimate the total reconnection efficiency.

  3. Stochastic electron acceleration during turbulent reconnection in strong shock waves

    Science.gov (United States)

    Matsumoto, Yosuke

    2016-04-01

    Acceleration of charged particles is a fundamental topic in astrophysical, space and laboratory plasmas. Very high energy particles are commonly found in the astrophysical and planetary shocks, and in the energy releases of solar flares and terrestrial substorms. Evidence for relativistic particle production during such phenomena has attracted much attention concerning collisionless shock waves and magnetic reconnection, respectively, as ultimate plasma energization mechanisms. While the energy conversion proceeds macroscopically, and therefore the energy mostly flows to ions, plasma kinetic instabilities excited in a localized region have been considered to be the main electron heating and acceleration mechanisms. We present that efficient electron energization can occur in a much larger area during turbulent magnetic reconnection from the intrinsic nature of a strong collisionless shock wave. Supercomputer simulations have revealed a multiscale shock structure comprising current sheets created via an ion-scale Weibel instability and resulting energy dissipation through magnetic reconnection. A part of the upstream electrons undergoes first-order Fermi acceleration by colliding with reconnection jets and magnetic islands, giving rise to a nonthermal relativistic population downstream. The dynamics has shed new light on magnetic reconnection as an agent of energy dissipation and particle acceleration in strong shock waves.

  4. Observational Signatures of Magnetic Reconnection in the Extended Corona

    Science.gov (United States)

    Savage, Sabrina; West, Matthew J.; Seaton, Daniel B.; Kobelski, Adam

    2016-01-01

    Observational signatures of reconnection have been studied extensively in the lower corona for decades, successfully providing insight into energy release mechanisms in the region above post-flare arcade loops and below 1.5 solar radii. During large eruptive events, however, energy release continues to occur well beyond the presence of reconnection signatures at these low heights. Supra-Arcade Downflows (SADs) and Supra-Arcade Downflowing Loops (SADLs) are particularly useful measures of continual reconnection in the corona as they may indicate the presence and path of retracting post-reconnection loops. SADs and SADLs have been faintly observed up to 18 hours beyond the passage of coronas mass ejections through the SOHO/LASCO field of view, but a recent event from 2014 October 14 associated with giant arches provides very clear observations of these downflows for days after the initial eruption. We report on this unique event and compare these findings with observational signatures of magnetic reconnection in the extended corona for more typical eruptions.

  5. On the longitudinal extent of magnetopause reconnection pulses

    Directory of Open Access Journals (Sweden)

    M. Lockwood

    Full Text Available The open magnetosphere model of cusp ion injection, acceleration and precipitation is used to predict the dispersion characteristics for fully pulsed magnetic reconnection at a low-latitude magnetopause X-line. The resulting steps, as would be seen by a satellite moving meridionally and normal to the ionospheric projection of the X-line, are compared with those seen by satellites moving longitudinally, along the open/closed boundary. It is shown that two observed cases can be explained by similar magnetosheath and reconnection characteristics, and that the major differences between them are well explained by the different satellite paths through the events. Both cases were observed in association with poleward-moving transient events seen by ground-based radar, as also predicted by the theory. The results show that the reconnection is pulsed but strongly imply it cannot also be spatially patchy, in the sense of isolated X-lines which independently are intermittently active. Furthermore they show that the reconnection pulses responsible for the poleward-moving events and the cusp ion steps, must cover at least 3 h of magnetic local time, although propagation of the active reconnection region may mean that it does not extend this far at any one instant of time.

  6. A new fast reconnection model in a collisionless regime

    CERN Document Server

    Tsiklauri, David

    2008-01-01

    Based on the first principles (by balancing the advection with the electron pressure tensor in the generalised Ohm's law, and using the conservation of mass) a simple model of magnetic reconnection in a collisionless regime is formulated. In addition to its importance from the fundamental point of view, the collisionless reconnection model offers a much faster reconnection rate ($M_{c'less}={(d_i/2)}^{1/2}$) than Sweet-Parker's classical one ($M_{sp}=S^{-1/2}$). The width of the diffusion region (current sheet) in the collisionless regime is found to be $\\delta_{c'less}={(d_i/2)}^{1/2}L$, which is much larger than the Sweet-Parker width ($\\delta_{sp}=S^{-1/2}L$) for the space plasma conditions. Amongst other issues, this alleviates e.g. the problem of interpretation of solar flares by means of reconnection, as for the typical solar coronal parameters the obtained collisionless reconnection time can be $< 10$ minutes, as opposed to Sweet-Parker's equivalent value of $<$ year. The new theoretical reconnec...

  7. Statistical study of reconnection exhausts in the solar wind

    International Nuclear Information System (INIS)

    Magnetic reconnection is a fundamental process that changes magnetic field configuration and converts a magnetic energy to flow energy and plasma heating. This paper presents a survey of the plasma and magnetic field parameters inside 418 reconnection exhausts identified in the WIND data from 1995-2012. The statistical analysis is oriented on the re-distribution of the magnetic energy released due to reconnection between a plasma acceleration and its heating. The results show that both the portion of the energy deposited into heat as well as the energy spent on the acceleration of the exhaust plasma rise with the magnetic shear angle in accord with the increase of the magnetic flux available for reconnection. The decrease of the normalized exhaust speed with the increasing magnetic shear suggests a decreasing efficiency of the acceleration and/or the increasing efficiency of heating in high-shear events. However, we have found that the already suggested relation between the exhaust speed and temperature enhancement would be rather considered as an upper limit of the plasma heating during reconnection regardless of the shear angle.

  8. Effects of social anxiety and group membership of potential affiliates on social reconnection after ostracism

    OpenAIRE

    TSUMURA, Kenta; Murata, Koji

    2015-01-01

    After being ostracized, people would try to socially reconnect with others. However, people high in social anxiety (HSA) might be more unwilling to reconnect with new affiliates than people low in social anxiety (LSA) because HSA individuals are more pessimistic and fear about the interaction with others. Particularly, it might be more difficult for HSA individuals to reconnect with outgroup members. As a result, HSA ostracized participants showed a greater desire to reconnect with ingroup me...

  9. What is taking place in science classrooms?: A case study analysis of teaching and learning in seventh-grade science of one Alabama school and its impact on African American student learning

    Science.gov (United States)

    Norman, Lashaunda Renea

    This qualitative case study investigated the teaching strategies that improve science learning of African American students. This research study further sought the extent the identified teaching strategies that are used to improve African American science learning reflect culturally responsive teaching. Best teaching strategies and culturally responsive teaching have been researched, but there has been minimal research on the impact that both have on science learning, with an emphasis on the African American population. Consequently, the Black-White achievement gap in science persists. The findings revealed the following teaching strategies have a positive impact on African American science learning: (a) lecture-discussion, (b) notetaking, (c) reading strategies, (d) graphic organizers, (e) hands-on activities, (f) laboratory experiences, and (g) cooperative learning. Culturally responsive teaching strategies were evident in the seventh-grade science classrooms observed. Seven themes emerged from this research data: (1) The participating teachers based their research-based teaching strategies used in the classroom on all of the students' learning styles, abilities, attitudes towards science, and motivational levels about learning science, with no emphasis on the African American student population; (2) The participating teachers taught the state content standards simultaneously using the same instructional model daily, incorporating other content areas when possible; (3) The participating African American students believed their seventh-grade science teachers used a variety of teaching strategies to ensure science learning took place, that science learning was fun, and that science learning was engaging; (4) The participating African American students genuinely liked their teacher; (5) The participating African American students revealed high self-efficacy; (6) The African American student participants' parents value education and moved to Success Middle School

  10. Blazar flares powered by plasmoids in relativistic reconnection

    CERN Document Server

    Petropoulou, Maria; Sironi, Lorenzo

    2016-01-01

    Powerful flares from blazars with short ($\\sim$ min) variability timescales are challenging for current models of blazar emission. Here, we present a physically motivated ab initio model for blazar flares based on the results of recent particle-in-cell (PIC) simulations of relativistic magnetic reconnection. PIC simulations demonstrate that quasi-spherical plasmoids filled with high-energy particles and magnetic fields are a self-consistent by-product of the reconnection process. By coupling our PIC-based results (i.e., plasmoid growth, acceleration profile, particle and magnetic content) with a kinetic equation for the evolution of the electron distribution function we demonstrate that relativistic reconnection in blazar jets can produce powerful flares whose temporal and spectral properties are consistent with the observations. In particular, our model predicts correlated synchrotron and synchrotron self-Compton flares of duration of several hours--days powered by the largest and slowest moving plasmoids th...

  11. Magnetic Reconnection on Jet-Accretion disk Systems

    CERN Document Server

    Pino, Elisabete M de Gouveia Dal; Kadowaki, Luis H S; Khiali, Behoruz; Kowal, Grzergorz; Mizuno, Yosuke; Singh, Chandra B

    2016-01-01

    Fast Magnetic Reconnection is currently regarded as an important process also beyond the solar system, specially in magnetically dominated regions of galactic and extragalactic sources like the surrounds of black holes and relativistic jets. In this lecture we discuss briefly the theory of fast magnetic reconnection, specially when driven by turbulence which is very frequent in Astrophysical flows, and its implications for relativistic particle acceleration. Then we discuss these processes in the context of the sources above, showing recent analytical and multidimensional numerical MHD studies that indicate that fast reconnection can be a powerful process to accelerate particles to relativistic velocities, produce the associated high energy non-thermal emission, and account for efficient conversion of magnetic into kinetic energy in these flows.

  12. Two types of whistler waves in the hall reconnection region

    Science.gov (United States)

    Huang, S. Y.; Fu, H. S.; Yuan, Z. G.; Vaivads, A.; Khotyaintsev, Y. V.; Retino, A.; Zhou, M.; Graham, D. B.; Fujimoto, K.; Sahraoui, F.; Deng, X. H.; Ni, B.; Pang, Y.; Fu, S.; Wang, D. D.; Zhou, X.

    2016-07-01

    Whistler waves are believed to play an important role during magnetic reconnection. Here we report the near-simultaneous occurrence of two types of the whistler-mode waves in the magnetotail Hall reconnection region. The first type is observed in the magnetic pileup region of downstream and propagates away to downstream along the field lines and is possibly generated by the electron temperature anisotropy at the magnetic equator. The second type, propagating toward the X line, is found around the separatrix region and probably is generated by the electron beam-driven whistler instability or Čerenkov emission from electron phase-space holes. These observations of two different types of whistler waves are consistent with recent kinetic simulations and suggest that the observed whistler waves are a consequence of magnetic reconnection.

  13. Magnetic reconnection between a solar filament and nearby coronal loops

    CERN Document Server

    Li, Leping; Peter, Hardi; Priest, Eric; Chen, Huadong; Guo, Lijia; Chen, Feng; Mackay, Duncan

    2016-01-01

    Magnetic reconnection, the rearrangement of magnetic field topology, is a fundamental physical process in magnetized plasma systems all over the universe1,2. Its process is difficult to be directly observed. Coronal structures, such as coronal loops and filament spines, often sketch the magnetic field geometry and its changes in the solar corona3. Here we show a highly suggestive observation of magnetic reconnection between an erupting solar filament and its nearby coronal loops, resulting in changes in connection of the filament. X-type structures form when the erupting filament encounters the loops. The filament becomes straight, and bright current sheets form at the interfaces with the loops. Many plasmoids appear in these current sheets and propagate bi-directionally. The filament disconnects from the current sheets, which gradually disperse and disappear, reconnects to the loops, and becomes redirected to the loop footpoints. This evolution of the filament and the loops suggests successive magnetic recon...

  14. Effects of electron inertia in collisionless magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Andrés, Nahuel, E-mail: nandres@iafe.uba.ar; Gómez, Daniel [Instituto de Astronomía y Física del Espacio, CC. 67, suc. 28, 1428, Buenos Aires (Argentina); Departamento de Física, Facultad de Ciencias Exactas y Naturales, Univrsidad de Buenos Aires, Pabellón I, 1428, Buenos Aires (Argentina); Martin, Luis; Dmitruk, Pablo [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Univrsidad de Buenos Aires, Pabellón I, 1428, Buenos Aires (Argentina)

    2014-07-15

    We present a study of collisionless magnetic reconnection within the framework of full two-fluid MHD for a completely ionized hydrogen plasma, retaining the effects of the Hall current, electron pressure and electron inertia. We performed 2.5D simulations using a pseudo-spectral code with no dissipative effects. We check that the ideal invariants of the problem are conserved down to round-off errors. Our numerical results confirm that the change in the topology of the magnetic field lines is exclusively due to the presence of electron inertia. The computed reconnection rates remain a fair fraction of the Alfvén velocity, which therefore qualifies as fast reconnection.

  15. Turbulent reconnection of magnetic bipoles in stratified turbulence

    CERN Document Server

    Jabbari, Sarah; Mitra, Dhrubaditya; Kleeorin, Nathan; Rogachevskii, Igor

    2016-01-01

    We consider strongly stratified forced turbulence in a plane-parallel layer with helicity and corresponding large-scale dynamo action in the lower part and nonhelical turbulence in the upper. The magnetic field is found to develop strongly concentrated bipolar structures near the surface. They form elongated bands with a sharp interface between opposite polarities. Unlike earlier experiments with imposed magnetic field, the inclusion of rotation does not strongly suppress the formation of these structures. We perform a systematic numerical study of this phenomenon by varying magnetic Reynolds number, scale separation ratio, and Coriolis number. We also focus on the formation of the current sheet between bipolar regions where reconnection of oppositely oriented field lines occurs. We determine the reconnection rate by measuring either the inflow velocity in the vicinity of the current sheet or by measuring the electric field in the reconnection region. We demonstrate that for small Lundquist number, S1000, the...

  16. Numerical simulations of magnetic reconnection in the lower solar atmosphere

    Institute of Scientific and Technical Information of China (English)

    Xiao-Yan Xu; Cheng Fang; Ming-De Ding; Dan-Hui Gao

    2011-01-01

    Observations indicate that Ellerman bombs (EBs) and chromospheric microflares both occur in the lower solar atmosphere, and share many common features,such as temperature enhancements, accompanying jet-like mass motions, short lifetime, and so on. These strongly suggest that EBs and chromospheric microflares could both probably be induced by magnetic reconnection in the lower solar atmosphere.With gravity, ionization and radiation considered, we perform two-dimensional numerical simulations of magnetic reconnection in the lower solar atmosphere. The influence of different parameters, such as intensity of the magnetic field and anomalous resistivity, on the results are investigated. Our result demonstrates that the temperature increases are mainly due to the joule dissipation caused by magnetic reconnection.The spectral profiles of EBs and chromospheric microflares are calculated with the non-LTE radiative transfer theory and compared with observations. It is found that the typical features of the two phenomena can be qualitatively reproduced.

  17. Three-Dimensional Modeling of Guide-Field Magnetic Reconnection

    Science.gov (United States)

    Hesse, Michael

    2005-01-01

    The dissipation mechanism of guide field magnetic reconnection remains a subject of intense scientific interest. On one hand, one set of recent studies have shown that particle inertia-based processes, which include thermal and bulk inertial effects, provide the reconnection electric field in the diffusion region. On the other hand, a second set of studies emphasizes the role of wave-particle interactions in providing anomalous resistivity in the diffusion region. In this presentation, we analyze three-dimensional PIC simulations of guide-field magnetic reconnection. Specific emphasis will be on the question whether thermal-inertia processes, mediated by the electron pressure tensor, remain a viable dissipation mechanism in fully three-dimensional systems.

  18. Does social exclusion motivate interpersonal reconnection? Resolving the "porcupine problem".

    Science.gov (United States)

    Maner, Jon K; DeWall, C Nathan; Baumeister, Roy F; Schaller, Mark

    2007-01-01

    Evidence from 6 experiments supports the social reconnection hypothesis, which posits that the experience of social exclusion increases the motivation to forge social bonds with new sources of potential affiliation. Threat of social exclusion led participants to express greater interest in making new friends, to increase their desire to work with others, to form more positive impressions of novel social targets, and to assign greater rewards to new interaction partners. Findings also suggest potential boundary conditions to the social reconnection hypothesis. Excluded individuals did not seem to seek reconnection with the specific perpetrators of exclusion or with novel partners with whom no face-to-face interaction was anticipated. Furthermore, fear of negative evaluation moderated responses to exclusion such that participants low in fear of negative evaluation responded to new interaction partners in an affiliative fashion, whereas participants high in fear of negative evaluation did not.

  19. Magnetic reconnection in the near-Mars magnetotail: MAVEN observations

    Science.gov (United States)

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

    2015-11-01

    We report Mars Atmosphere and Volatile EvolutioN (MAVEN) observations of electrons, ions, and magnetic fields which provide comprehensive demonstration of magnetic reconnection signatures in the Martian magnetotail. In the near-Mars tail current sheet at XMSO˜-1.3RM, trapped electrons with two-sided loss cones were observed, indicating the closed magnetic field topology. In the closed field region, MAVEN observed Hall magnetic field signatures and Marsward bulk flows of H+, O+, and O2+ ions, which suggest the presence of X lines tailward from the spacecraft. Velocity distribution functions of the reconnection outflow ions exhibit counterstreaming beams separated along the current sheet normal, and their bulk velocities in the outflow direction inversely depend on ion mass. These characteristics are in qualitative agreement with previous multispecies kinetic simulations. The near-Mars magnetotail provides a unique environment for studying multi-ion reconnection.

  20. Reconnection dynamics and normal fluid mutual friction in superfluid turbulence

    CERN Document Server

    Laurie, Jason

    2014-01-01

    We investigate the forcing of the normal fluid via mutual friction in finite temperature superfluid turbulence in helium-4, paying particular attention to the role of quantized vortex reconnections. Through the use of the vortex filament model, we produce three experimentally relevant vortex tangles each with different topological properties in steady state conditions. Subsequently we investigate, through statistical analysis, how the mutual friction force upon the normal fluid is affected by the characteristic of each of the vortex tangles. Finally, by monitoring the vortex reconnection events, we show how reconnections produce areas of relatively high curvature and superfluid velocity leading to regions of high normal fluid mutual friction, particularly for the homogeneous and isotropic tangles.

  1. Beaming of particles and synchrotron radiation in relativistic magnetic reconnection

    CERN Document Server

    Kagan, Daniel; Piran, Tsvi

    2016-01-01

    Relativistic reconnection has been invoked as a mechanism for particle acceleration in numerous astrophysical systems. According to idealised analytical models reconnection produces a bulk relativistic outflow emerging from the reconnection sites (X-points). The resulting radiation is therefore highly beamed. Using two-dimensional particle-in-cell (PIC) simulations, we investigate particle and radiation beaming, finding a very different picture. Instead of having a relativistic average bulk motion with isotropic electron velocity distribution in its rest frame, we find that the bulk motion of particles in X-points is similar to their Lorentz factor gamma, and the particles are beamed within about 5/gamma. On the way from the X-point to the magnetic islands, particles turn in the magnetic field, forming a fan confined to the current sheet. Once they reach the islands they isotropise after completing a full Larmor gyration and their radiation is not strongly beamed anymore. The radiation pattern at a given freq...

  2. Localized electron heating during magnetic reconnection in MAST

    Science.gov (United States)

    Yamada, T.; Tanabe, H.; Watanabe, T. G.; Hayashi, Y.; Imazawa, R.; Inomoto, M.; Ono, Y.; Gryaznevich, M.; Scannell, R.; Michael, C.; The MAST Team

    2016-10-01

    Significant increase in the plasma temperature above 1 keV was measured during the kilogauss magnetic field reconnection of two merging toroidal plasmas under the high-guide field and collision-less conditions. The electron temperature was observed to peak significantly at the X-point inside the current sheet, indicating Joule heating caused by the toroidal electric field along the X-line. This peaked temperature increases significantly with the guide field, in agreement with the electron mean-free path calculation. The slow electron heating in the downstream suggests energy conversion from ions to electrons through ion-electron collisions in the bulk plasma as the second electron heating mechanism in the bulk plasma. The electron density profile clearly reveals the electron density pile-up / fast shock structures in the downstream of reconnection, suggesting energy conversion from ion flow energy to ion thermal energy as well as significant ion heating by reconnection outflow.

  3. Suppression of collisionless magnetic reconnection in asymmetric current sheets

    CERN Document Server

    Liu, Yi-Hsin

    2016-01-01

    Using fully kinetic simulations, we study the suppression of asymmetric reconnection in the limit where the diamagnetic drift speed >> Alfven speed and the magnetic shear angle is moderate. We demonstrate that the slippage between electrons and the magnetic flux facilitates reconnection, and can even result in fast reconnection that lacks one of the outflow jets. Through comparing a case where the diamagnetic drift is supported by the temperature gradient with a companion case that has a density gradient instead, we identify a robust suppression mechanism. The drift of the x-line is slowed down locally by the asymmetric nature of the current sheet and the resulting tearing modes, then the x-line is run over and swallowed by the faster-moving following flux.

  4. Evolution of field line helicity during magnetic reconnection

    CERN Document Server

    Russell, Alexander J B; Hornig, Gunnar; Wilmot-Smith, Antonia L

    2015-01-01

    We investigate the evolution of field line helicity for non-zero magnetic fields that connect two boundaries, with emphasis on localized finite-B magnetic reconnection. Total (relative) magnetic helicity is already recognized as an important topological constraint on magnetohydrodynamic processes. Field line helicity offers further advantages because it preserves all topological information and can distinguish between different magnetic fields with the same total helicity. Magnetic reconnection changes field topology and field line helicity reflects these changes; the goal of this paper is to characterize that evolution. We start by deriving the evolution equation for field line helicity and examining its terms, also obtaining a simplified form for cases where dynamics are localized within the domain. The main result, which we support using kinematic examples, is that during localized reconnection in a topologically complex magnetic field, the evolution of field line helicity is dominated by a work-like term ...

  5. Radiative Signatures of Reconnection in X-ray Binary Spectral States

    Science.gov (United States)

    Uzdensky, Dmitri

    by several groups including ours indicate that reconnection can be a very efficient mechanism for nonthermal particle acceleration. However, these studies have not yet been adapted to XRB environments, e.g., they have not included the effects of prompt inverse-Compton cooling in the intense radiation environment and the possible effects of unequal electron and ion temperatures. We propose to conduct a series of first-principle numerical studies of particle acceleration and radiation in magnetic reconnection under the physical conditions similar to those expected in accreting black hole coronae and hot accretion flows, including the presence of the powerful background radiation bath. We will use our radiative particle-in-cell (PIC) code Zeltron that self-consistently takes into account the radiation reaction effects on the particle motion and simultaneously computes the produced synchrotron and inverse-Compton radiation. Comparing the results of our calculations with the observations of X-ray spectra in different spectral states will allow us to reverse-engineer the machinery of BH coronae and hot accretion flows and determine the physical conditions (the degree of magnetization/plasma-beta; the ambient radiative environment, etc.) of the plasma corresponding to these states. This in turn will enable us to test the existing theories of accretion physics that attempt to explain the existence and origin of these states. In addition, our simulations will probe radiative effects on reconnection inside the accretion disk proper, which should shed light on the processes governing the transitions between the spectral states.

  6. Observations of Magnetic Reconnection and Plasma Dynamics in Mercury's Magnetosphere

    Science.gov (United States)

    DiBraccio, Gina A.

    Mercury's magnetosphere is formed as a result of the supersonic solar wind interacting with the planet's intrinsic magnetic field. The combination of the weak planetary dipole moment and intense solar wind forcing of the inner heliosphere creates a unique space environment, which can teach us about planetary magnetospheres. In this work, we analyze the first in situ orbital observations at Mercury, provided by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. Magnetic reconnection and the transport of plasma and magnetic flux are investigated using MESSENGER Magnetometer and Fast Imaging Plasma Spectrometer measurements. Here, we report our results on the effect of magnetic reconnection and plasma dynamics on Mercury's space environment: (1) Mercury's magnetosphere is driven by frequent, intense magnetic reconnection observed in the form of magnetic field components normal to the magnetopause, BN, and as helical bundles of flux, called magnetic flux ropes, in the cross-tail current sheet. The high reconnection rates are determined to be a direct consequence of the low plasma beta, the ratio of plasma to magnetic pressure, in the inner heliosphere. (2) As upstream solar wind conditions vary, we find that reconnection occurs at Mercury's magnetopause for all orientations of the interplanetary magnetic field, independent of shear angle. During the most extreme solar wind forcing events, the influence of induction fields generated within Mercury's highly conducting core are negated by erosion due to persistent magnetopause reconnection. (3) We present the first observations of Mercury's plasma mantle, which forms as a result of magnetopause reconnection and allows solar wind plasma to enter into the high-latitude magnetotail through the dayside cusps. The energy dispersion observed in the plasma mantle protons is used to infer the cross-magnetosphere electric field, providing a direct measurement of solar wind momentum

  7. Studies of Fragmentation and Colour Reconnection at LEP

    OpenAIRE

    Azzurri, P.

    2006-01-01

    Hadronic events at the Z pole have been investigated in search for Colour Reconnection effects and QCD coherence. Colour Reconnection effects are searched for in three-jet events and the data results are compared to the predictions of different Monte Carlo models. QCD colour coherence effects are tested through the multiplicity distributions of hadrons with restricted momenta, and the LEP1 e+e- data is compared to HERA e+p data under the equivalence assumption of the e+e- hemisphere with the ...

  8. Taking Turns

    Science.gov (United States)

    Hopkins, Brian

    2010-01-01

    Two people take turns selecting from an even number of items. Their relative preferences over the items can be described as a permutation, then tools from algebraic combinatorics can be used to answer various questions. We describe each person's optimal selection strategies including how each could make use of knowing the other's preferences. We…

  9. Effects from switching on PIC simulations: Geospace Environmental Modeling (GEM) reconnection setup revisited

    Science.gov (United States)

    Bourdin, P. A.; Nakamura, T.; Narita, Y.

    2015-12-01

    Electromagnetic Parcile-In-Cell (PIC) simulations are widely used to study plasma phenomena where kinetic scales are coupled to fluid scales. One of these phenomena is the evolution of magnetic reconnection. Switch-on effects have been described earlier for magneto-/hydrodynamic (MHD and HD) simulations, where oscillations are ignited by the initial condition and the usual instantaneous way of starting a simulation run. Here we revisit the GEM setup (a Harris current sheet) and demonstrate the immediate generation of oscillations propagating perpendicular to the magnetic shear layer (in Bz). Also we show how these oscillations do not dissipate quickly and will later be mode-converted to generate wave power, first in By, much later also in Bx (pointing along the shear direction). One needs to take care not to interpret these oscillations as physical wave modes associated with the nature of reconnection. We propose a method to prevent such switch-on effects from the beginning, that should be considered for implementation in other PIC simulation codes as well.

  10. Implications of L1 observations for slow solar wind formation by solar reconnection

    Science.gov (United States)

    Kepko, L.; Viall, N. M.; Antiochos, S. K.; Lepri, S. T.; Kasper, J. C.; Weberg, M.

    2016-05-01

    While the source of the fast solar wind is known to be coronal holes, the source of the slow solar wind has remained a mystery. Long time scale trends in the composition and charge states show strong correlations between solar wind velocity and plasma parameters, yet these correlations have proved ineffective in determining the slow wind source. We take advantage of new high time resolution (12 min) measurements of solar wind composition and charge state abundances at L1 and previously identified 90 min quasiperiodic structures to probe the fundamental timescales of slow wind variability. The combination of new high temporal resolution composition measurements and the clearly identified boundaries of the periodic structures allows us to utilize these distinct solar wind parcels as tracers of slow wind origin and acceleration. We find that each 90 min (2000 Mm) parcel of slow wind has near-constant speed yet exhibits repeatable, systematic charge state and composition variations that span the entire range of statistically determined slow solar wind values. The classic composition-velocity correlations do not hold on short, approximately hourlong, time scales. Furthermore, the data demonstrate that these structures were created by magnetic reconnection. Our results impose severe new constraints on slow solar wind origin and provide new, compelling evidence that the slow wind results from the sporadic release of closed field plasma via magnetic reconnection at the boundary between open and closed flux in the Sun's atmosphere.

  11. Brand new authentic places

    DEFF Research Database (Denmark)

    Stender, Marie

    How are places and material surroundings ascribed with meaning when new residential neighbourhoods are designed, branded and taken into use? Existing research on housing, neighbourhoods and urban design tends to take the perspective of either the architect or the user rather than to explore...... the relation and interplay between the two. This study strives to fill this gap by ethnographically tracing the process from design to occupancy including the role of branding as a means to create authenticity. The concept of authenticity is often associated with old houses and neighbourhoods, but also in new...... of community. The project explores the inherent paradox of such staging of authenticity by way of three research questions: 1) How are new houses and areas made authentic through stories told through material design and branding? 2) What different concepts of authenticity are at stake? 3) How are the stories...

  12. Laboratory Observation of Resistive Electron Tearing in a Two-Fluid Reconnecting Current Sheet.

    Science.gov (United States)

    Jara-Almonte, Jonathan; Ji, Hantao; Yamada, Masaaki; Yoo, Jongsoo; Fox, William

    2016-08-26

    The spontaneous formation of plasmoids via the resistive electron tearing of a reconnecting current sheet is observed in the laboratory. These experiments are performed during driven, antiparallel reconnection in the two-fluid regime within the Magnetic Reconnection Experiment. It is found that plasmoids are present even at a very low Lundquist number, and the number of plasmoids scales with both the current sheet aspect ratio and the Lundquist number. The reconnection electric field increases when plasmoids are formed, leading to an enhanced reconnection rate. PMID:27610861

  13. Brazilian physicists take centre stage

    Science.gov (United States)

    Curtis, Susan

    2014-06-01

    With the FIFA World Cup taking place in Brazil this month, Susan Curtis travels to South America's richest nation to find out how its physicists are exploiting recent big increases in science funding.

  14. Optimization of placing-in and taking-out wagons on branch-shaped railway lines based on genetic and ant colony algorithm%基于遗传蚁群算法的树枝型铁路取送车问题优化

    Institute of Scientific and Technical Information of China (English)

    雷友诚; 涂祖耀; 桂卫华; 吴志飞; 闫福全

    2011-01-01

    Aiming at the distribution of railway line and a combinatorial mode of placing-in and taking-out wagons at an enterprise railway freight station, a mathematical model of optimal operation for placing-in and taking-out wagons in the branch-shaped private line was established, which is deduced as a typical traveling salesman problem(TSP). Meanwhile, a combination of genetic algorithm and ant colony algorithm called GACA was presented to resolve the large-scale combinatorial optimization problem. The genetic algorithm was adopted to generate pheromone to distribute. And the ant colony algorithm was used to find an accurate solution. As a result, the searching efficiency and the time efficiency of the combinatorial algorithm are both greatly improved. Combined with an example, the optimal solution of the placing-in and taking-out wagons problem is found.%针对企业铁路货运站的铁路线分布特点和“连送带取”的作业方式,建立树枝型专用线取送车的数学模型,将其归纳为一个典型的旅行商问题.同时提出一种融合遗传算法和蚁群算法特点的遗传蚁群算法(GACA)来解决这种大规模组合优化问题;采用遗传算法生成信息素分布,利用蚁群算法求精确解,有效提高算法的时间效率和求解效率.结合实例计算求得了企业取送车作业问题的最优解.

  15. Cassini in situ observations of long-duration magnetic reconnection in Saturn's magnetotail

    CERN Document Server

    Arridge, Christopher S; Jackman, Caitriona M; Poh, Gang-Kai; Slavin, James A; Thomsen, Michelle F; André, Nicolas; Jia, Xianzhe; Kidder, Ariah; Lamy, Laurent; Radioti, Aikaterina; Reisenfeld, Dan B; Sergis, Nick; Volwerk, Martin; Walsh, Andrew P; Zarka, Philippe; Coates, Andrew J; Dougherty, Michele K

    2015-01-01

    Magnetic reconnection is a fundamental process in solar system and astrophysical plasmas, through which stored magnetic energy associated with current sheets is converted into thermal, kinetic and wave energy. Magnetic reconnection is also thought to be a key process involved in shedding internally produced plasma from the giant magnetospheres at Jupiter and Saturn through topological reconfiguration of the magnetic field. The region where magnetic fields reconnect is known as the diffusion region and in this letter we report on the first encounter of the Cassini spacecraft with a diffusion region in Saturn's magnetotail. The data also show evidence of magnetic reconnection over a period of 19 h revealing that reconnection can, in fact, act for prolonged intervals in a rapidly rotating magnetosphere. We show that reconnection can be a significant pathway for internal plasma loss at Saturn. This counters the view of reconnection as a transient method of internal plasma loss at Saturn. These results, although d...

  16. Conversion of magnetic energy in the magnetic reconnection layer of a laboratory plasma

    International Nuclear Information System (INIS)

    Magnetic reconnection, in which magnetic field lines break and reconnect to change their topology, occurs throughout the universe. The essential feature of reconnection is that it energizes plasma particles by converting magnetic energy. Despite the long history of reconnection research, how this energy conversion occurs remains a major unresolved problem in plasma physics. Here we report that the energy conversion in a laboratory reconnection layer occurs in a much larger region than previously considered. The mechanisms for energizing plasma particles in the reconnection layer are identified, and a quantitative inventory of the converted energy is presented for the first time in a well defined reconnection layer; 50% of the magnetic energy is converted to particle energy, 2/3 of which transferred to ions and 1/3 to electrons. Our results are compared with simulations and space measurements, for a key step toward resolving one of the most important problems in plasma physics

  17. Magnetic reconnection: from the Sweet-Parker model to stochastic plasmoid chains

    CERN Document Server

    Loureiro, N F

    2015-01-01

    (abridged) Magnetic reconnection is the topological reconfiguration of the magnetic field in a plasma, accompanied by the violent release of energy and particle acceleration. Reconnection is as ubiquitous as plasmas themselves, with solar flares perhaps the most popular example. Over the last few years, the theoretical understanding of magnetic reconnection in large-scale fluid systems has undergone a major paradigm shift. The steady-state model of reconnection described by the famous Sweet-Parker (SP) theory, which dominated the field for ~50 years, has been replaced with an essentially time-dependent, bursty picture of the reconnection layer, dominated by the continuous formation and ejection of multiple secondary islands (plasmoids). Whereas in the SP model reconnection was predicted to be slow, a major implication of this new paradigm is that reconnection in fluid systems is fast (i.e., independent of the Lundquist number), provided that the system is large enough. This conceptual shift hinges on the real...

  18. Theory and Applications of Non-Relativistic and Relativistic Turbulent Reconnection

    CERN Document Server

    Lazarian, A; Takamoto, M; Pino, E M de Gouveia Dal; Cho, J

    2015-01-01

    Realistic astrophysical environments are turbulent due to the extremely high Reynolds numbers. Therefore, the theories of reconnection intended for describing astrophysical reconnection should not ignore the effects of turbulence on magnetic reconnection. Turbulence is known to change the nature of many physical processes dramatically and in this review we claim that magnetic reconnection is not an exception. We stress that not only astrophysical turbulence is ubiquitous, but also magnetic reconnection itself induces turbulence. Thus turbulence must be accounted for in any realistic astrophysical reconnection setup. We argue that due to the similarities of MHD turbulence in relativistic and non-relativistic cases the theory of magnetic reconnection developed for the non-relativistic case can be extended to the relativistic case and we provide numerical simulations that support this conjecture. We also provide quantitative comparisons of the theoretical predictions and results of numerical experiments, includi...

  19. Distinct characteristics of asymmetric magnetic reconnections: Observational results from the exhaust region at the dayside magnetopause

    Science.gov (United States)

    Zhang, Y. C.

    2016-06-01

    Magnetic reconnection plays a key role in the conversion of magnetic energy into the thermal and kinetic energy of plasma. On either side of the diffusion region in space plasma, the conditions for the occurrence of reconnections are usually not symmetric. Previous theoretical studies have predicted that reconnections under asymmetric conditions will bear different features compared with those of symmetric reconnections, and numerical simulations have verified these distinct features. However, to date, the features of asymmetric reconnections have not been thoroughly investigated using in situ observations; thus, some results from theoretical studies and simulations have not been tested with observations sufficiently well. Here, spacecraft observations are used in a statistical investigation of asymmetric magnetic reconnection exhaust at the dayside magnetopause. The resulting observational features are consistent with the theoretical predictions. The results presented here advance our understanding of the development of reconnections under asymmetric conditions.

  20. Effects of Hall Current in the Driven Reconnection with Various Scales

    Institute of Scientific and Technical Information of China (English)

    YANG Hong-Ang; JIN Shu-Ping

    2004-01-01

    In the driven reconnection process with various scales, the effect of Hall current is studied numerically using a Hall magnetohydrodynamics (MHD) code derived from a multi-step implicit scheme. In the cases with Lc/di ≤ 1.0 (Lcis the half-thickness of initial current layer, di is the ion inertial length), the features of Hall MHD reconnection are shown as follows: a quasi-steady single X-line reconnection is obtained, the By component with a quadrupolar structure is generated and the maximum reconnection rate is larger than 0.11. In the cases with Lc/di > 1.0, the effect of Hall current on the reconnection dynamics weakens and Hall MHD reconnection is gradually transformed into resistive MHD reconnection as Lc/di increases.

  1. Can Three-Dimensional Instabilities Enable Fast Reconnection?

    Science.gov (United States)

    McClymont, Alexander N.

    1997-05-01

    Most studies of magnetic reconnection have assumed a two-dimensional geometry. Gas swept into the current sheet halts the collapse to the near-singularity required to effectively dissipate magnetic energy. The gas is squeezed out of the current sheet along the separatrices at the local sound speed (McClymont and Craig, 1996, Ap. J. 466, 487). Although this allows collapse to proceed (at a slower pace) it is not yet clear whether all the gas can be removed, particularly in a closed system. Therefore it is of interest to examine how relaxing invariance along the third dimension might allow escape of gas from the current sheet and reconnection to proceed at an explosive rate. Uchida and Sakurai (1977, Solar Phys. 51, 413) have examined the possibility of reconnection rate enhancement by the three-dimensional interchange instability. Some three-dimensional analyses (e.g. Craig and Fabling, 1995, Ap. J. 462, 969) have assumed analytic forms of solution which preclude many outcomes. Another three dimensional simulation (Strauss, 1993, Geophys. Res. Lett., 20, 325) assumes a strong magnetic field along the current sheet. We discuss ideal instabilities and other phenomena which might allow gas to escape more effectively from the current sheet, and enhance the reconnection rate.

  2. Turbulent reconnection of magnetic bipoles in stratified turbulence

    Science.gov (United States)

    Jabbari, S.; Brandenburg, A.; Mitra, Dhrubaditya; Kleeorin, N.; Rogachevskii, I.

    2016-07-01

    We consider strongly stratified forced turbulence in a plane-parallel layer with helicity and corresponding large-scale dynamo action in the lower part and non-helical turbulence in the upper. The magnetic field is found to develop strongly concentrated bipolar structures near the surface. They form elongated bands with a sharp interface between opposite polarities. Unlike earlier experiments with imposed magnetic field, the inclusion of rotation does not strongly suppress the formation of these structures. We perform a systematic numerical study of this phenomenon by varying magnetic Reynolds number, scale-separation ratio, and Coriolis number. We focus on the formation of a current sheet between bipolar regions where reconnection of oppositely oriented field lines occurs. We determine the reconnection rate by measuring either the inflow velocity in the vicinity of the current sheet or by measuring the electric field in the reconnection region. We demonstrate that for large Lundquist numbers, S > 103, the reconnection rate is nearly independent of S in agreement with results of recent numerical simulations performed by other groups in simpler settings.

  3. Slow shock formation and temperature anisotropy in collisionless magnetic reconnection

    Science.gov (United States)

    Higashimori, K.; Hoshino, M.

    2011-12-01

    We perform a two-dimensional simulation by using an electromagnetic hybrid code to study the formation of slow-mode shocks in collisionless magnetic reconnection in low beta plasmas, and we argue that one of important agents of the formation of slow shocks is the ion temperature anisotropy enhanced at the shock downstream region. As magnetic reconnection develops, it is known that the parallel temperature along the magnetic field becomes large in association with the anisotropic PSBL ion beams, and this temperature anisotropy has a tendency to suppress the formation of slow shock. Although preceding studies on magnetic reconnection with kinetic codes have shown such ion temperature anisotropy along the reconnection layer, the direct relation between formation of slow shocks and the ion temperature anisotropy has not been investigated. Based on our simulation result, we found that the slow shock formation is suppressed due to the large temperature anisotropy near the X-type region, but the downstream ion temperature anisotropy relaxes with increasing the distance from the magnetic neutral point. As a result, two pairs of current structures, which are the strong evidence of dissipation of magnetic field in slow shocks, are formed at the distance |x| > 115 λ i from the neutral point.

  4. Global and local disturbances in the magnetotail during reconnection

    Directory of Open Access Journals (Sweden)

    T. V. Laitinen

    2007-05-01

    Full Text Available We examine Cluster observations of a reconnection event at xGSM=−15.7 RE in the magnetotail on 11 October 2001, when Cluster recorded the current sheet for an extended period including the entire duration of the reconnection event. The onset of reconnection is associated with a sudden orientation change of the ambient magnetic field, which is also observed simultaneously by Goes-8 at geostationary orbit. Current sheet oscillations are observed both before reconnection and during it. The speed of the flapping motions is found to increase when the current sheet undergoes the transition from quiet to active state, as suggested by an earlier statistical result and now confirmed within one single event. Within the diffusion region both the tailward and earthward parts of the quadrupolar magnetic Hall structure are recorded as an x-line passes Cluster. We report the first observations of the Hall structure conforming to the kinks in the current sheet. This results in relatively strong fluctuations in Bz, which are shown to be the Hall signature tilted in the yz plane with the current sheet.

  5. Predicted signatures of pulsed reconnection in ESR data

    Directory of Open Access Journals (Sweden)

    C. J. Davis

    Full Text Available Early in 1996, the latest of the European incoherent-scatter (EISCAT radars came into operation on the Svalbard islands. The EISCAT Svalbard Radar (ESR has been built in order to study the ionosphere in the northern polar cap and in particular, the dayside cusp. Conditions in the upper atmosphere in the cusp region are complex, with magnetosheath plasma cascading freely into the atmosphere along open magnetic field lines as a result of magnetic reconnection at the dayside magnetopause. A model has been developed to predict the effects of pulsed reconnection and the subsequent cusp precipitation in the ionosphere. Using this model we have successfully recreated some of the major features seen in photometer and satellite data within the cusp. In this paper, the work is extended to predict the signatures of pulsed reconnection in ESR data when the radar is pointed along the magnetic field. It is expected that enhancements in both electron concentration and electron temperature will be observed. Whether these enhancements are continuous in time or occur as a series of separate events is shown to depend critically on where the open/closed field-line boundary is with respect to the radar. This is shown to be particularly true when reconnection pulses are superposed on a steady background rate.

  6. 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.

  7. 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.

  8. Study of Local Reconnection Physics in a Laboratory Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Hantao Ji; Troy Carter; Scott Hsu; Masaaki Yamada

    2001-06-11

    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.

  9. 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.

  10. Aviation Expo Taking off

    Institute of Scientific and Technical Information of China (English)

    Liu Xinwen; Bai Yifeng

    2007-01-01

    @@ The 12nd Beijing Aviation Expo(Aviation Expo/China 2007) was held this September 19-22 at the China International Exhibition Center.Beijing Aviation Expo is the ONLY aviation exhibition (Civil & Military,including Airport & Air Traffic Control) organized in Beijing,taking place every two years.It is also the most influential aviation exhibition with the longest history in China.

  11. Does the measurement take place when nobody observes it?

    CERN Document Server

    Gurvitz, Shmuel

    2016-01-01

    We consider {\\em non-selective} continuous measurements of a particle tunneling to a reservoir of finite band-width ($\\Lambda$). The particle is continuously monitored by frequent projective measurements ("quantum trajectory"), separated by a time-interval $\\tau$. A simple analytical expression for the decay rate has been obtained. For Markovian reservoirs ($\\Lambda\\to\\infty$), no effect of the measurements is found. Otherwise for a finite $\\Lambda$, the decay rate always depends on the measurement time $\\tau$. This result is compared with alternative calculations, with no intermediate measurements, but when the measurement device is included in the Schr\\"odinger evolution. We found that the detector affects the system by the decoherence rate ($\\Gamma_d$), related to the detector's signal. Although both treatments are different, the final results become very close for $\\tau=2/\\Gamma_d$. This $\\tau$ corresponds to the minimal time for which the detector's signal can be distinguished by an "observer". This indi...

  12. I could never take the place of your man

    DEFF Research Database (Denmark)

    Andersen, Poul Houman; Munksgaard, Kristin B.

    and we coin the term network picturing to describe this process. We develop a theoretical framework that links network pictures and the patterned processes of interaction in business network routines. Here, we argue that the resistance managers' meet in their change efforts is likely, even if the change......We explore the dynamic tensions between the strategic change intentions by business actors and the rigidities of routines in business networks. We capture strategic change acts using the recent advances in the literature on network pictures as way to understand the value creation logics of managers...... efforts do not directly rival or contradict that of other actors in the exchange party in a resource-dependency sense, but may be caused simply by disrupting the existing business network. We use three case studies to illustrate and further explore the tensions between network picturing and network...

  13. A Case Study of How Teaching Practice Process Takes Place

    Science.gov (United States)

    Yalin Ucar, Meltem

    2012-01-01

    The process of "learning" carries an important role in the teaching practice which provides teacher candidates with professional development. Being responsible for the learning experiences in that level, cooperating teacher, teacher candidate, mentor and practice school are the important variables which determine the quality of the teaching…

  14. Magnetic Reconnection Onset and Energy Release at Current Sheets

    Science.gov (United States)

    DeVore, C. R.; Antiochos, Spiro K.

    2015-04-01

    Reconnection and energy release at current sheets are important at the Sun (coronal heating, coronal mass ejections, flares, and jets) and at the Earth (magnetopause flux transfer events and magnetotail substorms) and other magnetized planets, and occur also at the interface between the Heliosphere and the interstellar medium, the heliopause. The consequences range from relatively quiescent heating of the ambient plasma to highly explosive releases of energy and accelerated particles. We use the Adaptively Refined Magnetohydrodynamics Solver (ARMS) model to investigate the self-consistent formation and reconnection of current sheets in an initially potential 2D magnetic field containing a magnetic null point. Unequal stresses applied to the four quadrants bounded by the X-line separatrix distort the potential null into a double-Y-type current sheet. We find that this distortion eventually leads to onset of fast magnetic reconnection across the sheet, with copious production, merging, and ejection of magnetic islands due to plasmoid instability. In the absence of a mechanism for ideal instability or loss of equilibrium of the global structure, however, this reconnection leads to minimal energy release. Essentially, the current sheet oscillates about its force-free equilibrium configuration. When the structure is susceptible to a large-scale rearrangement of the magnetic field, on the other hand, the energy release becomes explosive. We identify the conditions required for reconnection to transform rapidly a large fraction of the magnetic free energy into kinetic and other forms of plasma energy, and to restructure the current sheet and its surrounding magnetic field dramatically. We discuss the implications of our results for understanding heliophysical activity, particularly eruptions, flares, and jets in the corona.Our research was supported by NASA’s Heliophysics Supporting Research and Living With a Star Targeted Research and Technology programs.

  15. Taking Part

    DEFF Research Database (Denmark)

    Ulfstjerne, Michael Alexander; Woodworth, Max

    2016-01-01

    desires to participate in urban expansion and to seize for oneself a portion of the local bonanzas in natural resources, property, and finance. The socio-spatial impacts of the financialization of the everyday environment are discussed in relation to urban transformation, the production of a “ghost town......This article examines how a resource bonanza in Ordos Municipality, Inner Mongolia Autonomous Region, in the 2000s translated into broad-based participation in informal lending networks and drove a remarkable, but short-lived, phase of urban expansion and private wealth accumulation. Local lending...... networks inflated enormous credit and property bubbles, which ultimately burst in 2011 with severe ramifications for Ordos's urban expansion and households' livelihoods. Based on fifteen months of ethnographic fieldwork in Ordos, the analysis advances the idea of “taking part” to explore the interconnected...

  16. Take heart!

    CERN Multimedia

    Alizée Dauvergne

    2010-01-01

    Recently, ten new semi-automatic defibrillators were installed at various locations around CERN. This is a preventive measure intended to provide cardiac arrest victims with the best possible response. The first responder could be you!   The Director-General has welcomed the initiative of the Medical Service and Fire Brigade for the installation of ten new semi-automatic defibrillators. You have probably seen them on your way to the restaurant, for example:  brand new semi-automatic defibrillators, ready for an emergency. Housed in a white wall-mounted case, the bright red defibrillators are marked with a white heart symbol crossed by a lightning bolt (see photo). The defibrillator is designed so that anyone can use it. “Anyone can use it, you don’t need to be a health professional,” says Dr Reymond from CERN's Medical Service. Together with the CERN Fire Brigade, he is behind the initiative to have these units put in place. And with good reason, as the unit...

  17. Taking Leave?

    CERN Document Server

    2000-01-01

    Planning a holiday? Then if you're a member of the personnel, you'll need to use the Laboratory's new leave system that will be put in place on 1 October. Leave allocations don't change - you are entitled to just as much holiday as before - but instead of being credited annually, your leave will be credited on a monthly basis, and this information will be communicated on your salary slip. The reason for the change is that with the various new leave schemes such as Recruitment by Saved Leave (RSL) and the Progressive Retirement Programme (PRP), a streamlined procedure was required for dealing with all kinds of leave. In the new system, each member of the personnel will have leave accounts to which leave will be credited monthly from the payroll and debited each time an absence is registered in the CERN Electronic Document Handling system (EDH). Leave balances will appear on monthly pay slips, and full details of leave transactions and balances will be available through EDH at all times. As the leave will be c...

  18. Stress at Work Place

    Directory of Open Access Journals (Sweden)

    Mohammad A. Shahrour

    2010-06-01

    Full Text Available One of hardest forms of stresses to avoid is that work place or job stress Job stress refers to stress experienced by an individual at or because of issues at their work place The term work related stress has many meanings and it causes different levels of anxiety. Not all challenges at work can be called stress as some of these challenges drive employees upward, and empower them to learn new skills or push them to work harder to achieve a certain goal. So, this type of challenges cannot be considered as true stress True job stress is a condition that not only destroys employee desire to work, but also his or her energy, getting them to suffer both emotionally and physically. Warning signs of stress at work when people feel overwhelmed they feel lacking confidence, become irritated or withdrawn, less productive, less effective and their work less rewarding if these warning passed unnoticed then signs and symptoms of stress will appear. Signs and Symptoms of Excessive 4. Personal conflicts with supervisors Workplace Stress or other employees 5. Feeling insecure at work ( 1. Feeling anxious, agitated, constantly threatened with criticism depressed or apathetic or job loss 2. Loss of interest at work 6. Discrimination ( race, sex or age 3. Difficulty in attention and 7. Discouragement (to feel concentration incompetent and worthless 4. Insomnia and sleep problems 8. Sexual harassment 5. Feeling fatigue 9. Lack of flexibility in work hours 6. Muscle tension and headaches 10. Poor work environment 7. Stomach problems or different 11. Developments in technology body aches 8. Social withdrawal How to Deal with Work Place Stress 9. Loss of sex drive 10. Using alcohol or drugs to cope Fortunately, there is a lot that you can do to manage and reduce stress at work. Different Causes of Job Stress General Guidelines: 1. Poor work conditions and having no say over such conditions A. Taking responsibility for 2. Unreasonable demands from improving your

  19. Extreme Particle Acceleration via Magnetic Reconnection in the Crab Nebula

    Science.gov (United States)

    Cerutti, Benoit; Uzdensky, D. A.; Begelman, M. C.

    2012-01-01

    The discovery by Agile and Fermi of intense day-long synchrotron gamma-ray flares above 100 MeV in the Crab Nebula challenges classical models of pulsar wind nebulae and particle acceleration. We argue that the flares are powered by magnetic reconnection in the nebula. Using relativistic test-particle simulations, we show that particles are naturally focused into a thin fan beam, deep inside the reconnection layer where the magnetic field is small. The particles then suffer less from synchrotron losses and pile up at the maximum energy given by the electric potential drop in the layer. Applying this model to the Crab Nebula, we find that the emerging synchrotron emission spectrum above 100 MeV is consistent with the September 2010 flare observations. No detectable emission is expected at other wavelengths. This scenario provides a viable explanation for the Crab Nebula gamma-ray flares.

  20. 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.

  1. Heat Transfer and Reconnection Diffusion in Turbulent Magnetized Plasmas

    CERN Document Server

    Lazarian, A

    2011-01-01

    It is well known that magnetic fields constrain motions of charged particles, impeding the diffusion of charged particles perpendicular to magnetic field direction. This modification of transport processes is of vital importance for a wide variety of astrophysical processes including cosmic ray transport, transfer of heavy elements in the interstellar medium, star formation etc. Dealing with these processes one should keep in mind that in realistic astrophysical conditions magnetized fluids are turbulent. In this review we single out a single transport process, namely, heat transfer and consider how it occurs in the presence of the magnetized turbulence. We show that the ability of magnetic field lines to constantly change topology and connectivity is at the heart of the correct description of the 3D magnetic field stochasticity in turbulent fluids. This ability is ensured by fast magnetic reconnection in turbulent fluids and puts forward the concept of reconnection diffusion at the core of the physical pictu...

  2. The plasmoid instability during asymmetric inflow magnetic reconnection

    CERN Document Server

    Murphy, Nicholas A; Shen, Chengcai; Lin, Jun; Ni, Lei

    2013-01-01

    Theoretical studies of the plasmoid instability generally assume that the reconnecting magnetic fields are symmetric. We relax this assumption by performing two-dimensional resistive magnetohydrodynamic simulations of the plasmoid instability during asymmetric inflow magnetic reconnection. Magnetic asymmetry modifies the onset, scaling, and dynamics of this instability. Magnetic islands develop preferentially into the weak magnetic field upstream region. Outflow jets from individual X-points impact plasmoids obliquely rather than directly as in the symmetric case. Consequently, deposition of momentum by the outflow jets into the plasmoids is less efficient, the plasmoids develop net vorticity, and shear flow slows down secondary merging between islands. Secondary merging events have asymmetry along both the inflow and outflow directions. Downstream plasma is more turbulent in cases with magnetic asymmetry because islands are able to roll around each other after exiting the current sheet. As in the symmetric c...

  3. 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 solar......-like). The MHD simulations start out from a potential magnetic field containing a null-point, obtained from a SOHO magnetogram extrapolation approximately 8 hours before a C-class flare was observed. The magnetic field is stressed with a boundary motion pattern similar to the horizontal motions observed by SOHO...... during the period preceding the flare. The general behavior is nearly independent of driving speed and numerical resolution, and is also very similar in stratified and unstratified models, provided only that the boundary motions are slow enough....

  4. Fast magnetic reconnection due to anisotropic electron pressure

    Science.gov (United States)

    Cassak, Paul; Baylor, Robert; Fermo, Raymond; Beidler, Matthew; Shay, Michael; Swisdak, Marc; Drake, James; Karimabadi, Homa

    2015-11-01

    A new regime of fast magnetic reconnection with an out-of-plane (guide) magnetic field is reported in which the key role is played by an electron pressure anisotropy described by the Chew-Goldberger-Low gyrotropic equations of state in the generalized Ohm's law, which even dominates the Hall term. A description of the physical cause of this behavior is provided and two-dimensional fluid simulations are used to confirm the results. The electron pressure anisotropy causes the out-of-plane magnetic field to develop a quadrupole structure of opposite polarity to the Hall magnetic field and gives rise to dispersive waves. In addition to being important for understanding what causes reconnection to be fast, this mechanism should dominate in plasmas with low plasma beta and a high in-plane plasma beta with electron temperature comparable to or larger than ion temperature, so it could be relevant in the solar wind and some tokamaks.

  5. Secondary fast reconnecting instability in the sawtooth crash

    CERN Document Server

    Del Sarto, Daniele

    2016-01-01

    In this work we consider magnetic reconnection in thin current sheets with both resistive and electron inertia effects. When the current sheet is produced by a primary instability of the internal kink type, the analysis of secondary instabilities indicates that reconnection proceeds on a time scale much shorter than the primary instability characteristic time. In the case of a sawtooth crash, non-collisional physics becomes important above a value of the Lundquist number which scales like S ~ (R/d_e)^{12/5}, in terms of the tokamak major radius R and of the electron skin depth d_e. This value is commonly achieved in present day devices. As collisionality is further reduced, the characteristic rate increases, approaching Alfv\\'enic values when the primary instability approaches the collisionless regime.

  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

    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......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...... were recorded for three years with sampling in spring and in summer each year. The results of a principal response curve analysis show that the macroinvertebrate community in the fully reconnected meander reflected main channel reference conditions after 1.5 years. The macroinvertebrate community...

  7. Three-dimensional shock formation in the spontaneous fast reconnection evolution

    Science.gov (United States)

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

    2011-12-01

    Shock structure associated with magnetic reconnection is studied using three-dimensional magneto-hydro-dynamics simulations on the basis of the spontaneous fast reconnection model. In the two-dimensional reconnection, the angle between the slow shock pair (thickness of the plasma sheet) is smaller (thinner) in the region with higher reconnection rate. On the other hand, in the three-dimensional reconnection, the reconnection rate in the diffusion region is not uniform in the direction of sheet current, and the angle between the shock pair at the center of the diffusion region should be smallest. However, the profile of the angle in the direction of sheet current is not satisfied with this relationship. It is shown that this structure is caused by the inflow from the direction of the positive and negative sheet current and the inflow of the magnetic flux accompanied with it.

  8. Fast magnetic reconnection supported by sporadic small-scale Petschek-type shocks

    Energy Technology Data Exchange (ETDEWEB)

    Shibayama, Takuya, E-mail: shibayama@stelab.nagoya-u.ac.jp; Nakabou, Takashi [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Kusano, Kanya [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kanazawa-ku, Yokohama, Kanagawa 236-0001 (Japan); Miyoshi, Takahiro [Department of Physical Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Vekstein, Grigory [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom)

    2015-10-15

    Standard magnetohydrodynamic (MHD) theory predicts reconnection rate that is far too slow to account for a wide variety of reconnection events observed in space and laboratory plasmas. Therefore, it was commonly accepted that some non-MHD (kinetic) effects play a crucial role in fast reconnection. A recently renewed interest in simple MHD models is associated with the so-called plasmoid instability of reconnecting current sheets. Although it is now evident that this effect can significantly enhance the rate of reconnection, many details of the underlying multiple-plasmoid process still remain controversial. Here, we report results of a high-resolution computer simulation which demonstrate that fast albeit intermittent magnetic reconnection is sustained by numerous small-scale Petschek-type shocks spontaneously formed in the current sheet due to its plasmoid instability.

  9. The Onset of Ion Heating During Magnetic Reconnection with a Strong Guide Field

    CERN Document Server

    Drake, J F

    2014-01-01

    The onset of the acceleration of ions during magnetic reconnection is explored via particle-in-cell simulations in the limit of a strong ambient guide field that self-consistently and simultaneously follow the motions of protons and $\\alpha$ particles. Heating parallel to the local magnetic field during reconnection with a guide field is strongly reduced compared with the reconnection of anti-parallel magnetic fields. The dominant heating of thermal ions during guide field reconnection results from pickup behavior of ions during their entry into reconnection exhausts and dominantly produces heating perpendicular rather than parallel to the local magnetic field. Pickup behavior requires that the ion transit time across the exhaust boundary (with a transverse scale of the order of the ion sound Larmor radius) be short compared with the ion cyclotron period. This translates into a threshold in the strength of reconnecting magnetic field that favors the heating of ions with high mass-to-charge. A simulation with ...

  10. Perspective Taking in Workplaces

    Directory of Open Access Journals (Sweden)

    Zappalà Salvatore

    2014-07-01

    Full Text Available Workplaces are often described as places in which individuals are motivated by their self-interests and in which negative events like time pressure, anxiety, conflict with co-workers, miscomprehensions, difficulties in solving problems, not-transmitted or not-exchanged information that lead to mistakes, and in some cases to injuries, stress or control, are part of everyday life (Dormann & Zapf, 2002; Schabracq, Winnubst and Cooper, 2003. Such situations are often the result of the limited comprehension of needs, skills, or information available to colleagues, supervisors, subordinates, clients or providers. However, workplaces are also places in which employees take care of clients, support colleagues and subordinates (Rhoades & Eisenberger, 2002, are enthusiastic about their job (Bakker et al., 2008, are motivated by leaders that encourage employees to transcend their own self-interests for the good of the group or the organization and provide them with the confidence to perform beyond expectations (Bass, 1997. Thus positive relationships at work are becoming a new interdisciplinary domain of inquiry (Dutton & Ragins, 2006. Within this positive relationships framework, in this paper we focus on a positive component of workplaces, and particularly on an individual cognitive and emotional process that has an important role in the workplace because it facilitates interpersonal relations and communications: it is the perspective taking process. In order to describe perspective taking, we will refer to some empirical studies and particularly to the review published by Parker, Atkins and Axtell in 2008 on the International Review of Industrial and Organizational Psychology.

  11. Application of PDSLin to the magnetic reconnection problem

    Science.gov (United States)

    Yuan, Xuefei; Li, Xiaoye S.; Yamazaki, Ichitaro; Jardin, Stephen C.; Koniges, Alice E.; Keyes, David E.

    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.

  12. 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.

  13. First order Fermi acceleration driven by magnetic reconnection

    CERN Document Server

    Drury, Luke O'C

    2012-01-01

    A box model is used to study first order Fermi acceleration driven by magnetic reconnection. It is shown, at least in this simple model, that the spectral index of the accelerated particles is related to the total compression in the same way as in diffusive shock acceleration and is not, as has been suggested, a universal $E^{-5/2}$ spectrum. The acceleration time-scale is estimated and some comments made about the applicability of the process.

  14. Urban Apiculture – A Way to Reconnect Society and Nature?

    OpenAIRE

    Claussnitzer, Marco

    2014-01-01

    In recent years honeybees have attracted a great deal of attention, an attention that seems to be rather unlikely when one looks at the general relationship between humans and the environment, which is often taken for granted. This study aims to look into one kind of corporate initiative in urban apiculture to reconnect humans and nature again. In particular the focus is on motivation, implementation and the impact these initiatives have on sustainable development. A transdisciplinary approac...

  15. Beaming of Particles and Synchrotron Radiation in Relativistic Magnetic Reconnection

    Science.gov (United States)

    Kagan, Daniel; Nakar, Ehud; Piran, Tsvi

    2016-08-01

    Relativistic reconnection has been invoked as a mechanism for particle acceleration in numerous astrophysical systems. According to idealized analytical models, reconnection produces a bulk relativistic outflow emerging from the reconnection sites (X-points). The resulting radiation is therefore highly beamed. Using two-dimensional particle-in-cell simulations, we investigate particle and radiation beaming, finding a very different picture. Instead of having a relativistic average bulk motion with an isotropic electron velocity distribution in its rest frame, we find that the bulk motion of the particles in X-points is similar to their Lorentz factor γ, and the particles are beamed within ˜ 5/γ . On the way from the X-point to the magnetic islands, particles turn in the magnetic field, forming a fan confined to the current sheet. Once they reach the islands they isotropize after completing a full Larmor gyration and their radiation is no longer strongly beamed. The radiation pattern at a given frequency depends on where the corresponding emitting electrons radiate their energy. Lower-energy particles that cool slowly spend most of their time in the islands and their radiation is not highly beamed. Only particles that quickly cool at the edge of the X-points generate a highly beamed fan-like radiation pattern. The radiation emerging from these fast cooling particles is above the burn-off limit (˜100 MeV in the overall rest frame of the reconnecting plasma). This has significant implications for models of gamma-ray bursts and active galactic nuclei that invoke beaming in that frame at much lower energies.

  16. Experimental Demonstration of the Collisionless Plasmoid Instability below the Ion Kinetic Scale during Magnetic Reconnection

    Science.gov (United States)

    Olson, J.; Egedal, J.; Greess, S.; Myers, R.; Clark, M.; Endrizzi, D.; Flanagan, K.; Milhone, J.; Peterson, E.; Wallace, J.; Weisberg, D.; Forest, C. B.

    2016-06-01

    The spontaneous formation of magnetic islands is observed in driven, antiparallel magnetic reconnection on the Terrestrial Reconnection Experiment. We here provide direct experimental evidence that the plasmoid instability is active at the electron scale inside the ion diffusion region in a low collisional regime. The experiments show the island formation occurs at a smaller system size than predicted by extended magnetohydrodynamics or fully collisionless simulations. This more effective seeding of magnetic islands emphasizes their importance to reconnection in naturally occurring 3D plasmas.

  17. Generation of Alfvenic Waves and Turbulence in Magnetic Reconnection Jets

    Science.gov (United States)

    Hoshino, M.

    2014-12-01

    The magneto-hydro-dynamic (MHD) linear stability for the plasma sheet with a localized bulk plasma flow parallel to the neutral sheet is investigated. We find three different unstable modes propagating parallel to the anti-parallel magnetic field line, and we call them as "streaming tearing'', "streaming sausage'', and "streaming kink'' mode. The streaming tearing and sausage modes have the tearing mode-like structure with symmetric density fluctuation to the neutral sheet, and the streaming kink mode has the asymmetric fluctuation. The growth rate of the streaming tearing mode decreases with increasing the magnetic Reynolds number, while those of the streaming sausage and kink modes do not strongly depend on the Reynolds number. The wavelengths of these unstable modes are of the order of the thickness of plasma sheet, which behavior is almost same as the standard tearing mode with no bulk flow. Roughly speaking the growth rates of three modes become faster than the standard tearing mode. The situation of the plasma sheet with the bulk flow can be realized in the reconnection exhaust with the Alfvenic reconnection jet, and the unstable modes may be regarded as one of the generation processes of Alfvenic turbulence in the plasma sheet during magnetic reconnection.

  18. 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.

  19. The Transition from Anti-Parallel to Component Magnetic Reconnection

    CERN Document Server

    Swisdak, M; Shay, M A; McIlhargey, J G

    2005-01-01

    We study the transition between anti-parallel and component collisionless magnetic reconnection with 2D particle-in-cell simulations. The primary finding is that a guide field \\approx 0.1 times as strong as the asymptotic reconnecting field -- roughly the field strength at which the electron Larmor radius is comparable to the width of the electron current layer -- is sufficient to magnetize the electrons in the vicinity of the x-line, thus causing significant changes to the structure of the electron dissipation region. This implies that great care should be exercised before concluding that magnetospheric reconnection is antiparallel. We also find that even for such weak guide fields strong inward-flowing electron beams form in the vicinity of the magnetic separatrices and Buneman-unstable distribution functions arise at the x-line itself. As in the calculations of {\\it Hesse et al.} [2002] and {\\it Yin and Winske} [2003], the non-gyrotropic elements of the electron pressure tensor play the dominant role in de...

  20. Hyperbolic method for magnetic reconnection process in steady state magnetohydrodynamics

    Science.gov (United States)

    Baty, Hubert; Nishikawa, Hiroaki

    2016-06-01

    A recent numerical approach for solving the advection-diffusion and Navier-Stokes equations is extended for the first time to a magnetohydrodynamic (MHD) model, aiming in particular consistent improvements over classical methods for investigating the magnetic reconnection process. In this study, we mainly focus on a two-dimensional incompressible set of resistive MHD equations written in flux-vorticity scalar variables. The originality of the method is based on hyperbolic reformulation of the dissipative terms, leading to the construction of an equivalent hyperbolic first-order (spatial derivatives) system. This enables the use of approximate Riemann solvers for handling dissipative and advective flux in the same way. A simple second-order finite-volume discretization on rectangular grids using an upwind flux is employed. The advantages of this method are illustrated by a comparison to two particular analytical steady state solutions of the inviscid magnetic reconnection mechanism, namely the magnetic annihilation and the reconnective diffusion problems. In particular, the numerical solution is obtained with the same order of accuracy for the solution and gradient for a wide range of magnetic Reynolds numbers, without any deterioration characteristic of more conventional schemes. The amelioration of the hyperbolic method and its extension to time-dependent MHD problems related to solar flares mechanisms is also discussed.

  1. Magnetic Reconnection in the Spheromak: Physics and Consequences

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, E B; Cohen, B I; Hill, D N; LoDestro, L L; McLean, H S; Romero-Talamas, C A; Wood, R D; Sovinec, C R

    2006-02-28

    Magnetic reconnection in the spheromak changes magnetic topology by conversion of injected toroidal flux into poloidal flux and by magnetic surface closure (or opening) in a slowly decaying spheromak. Results from the Sustained Spheromak Physics Experiment, SSPX, are compared with resistive MHD simulations using the NIMROD code. Voltage spikes on the SSPX gun during spheromak formation are interpreted as reconnection across a negative-current layer close to the mean-field x-point. Field lines are chaotic during these events, resulting in rapid electron energy loss to the walls and the low T{sub e} < 50 eV seen in experiment and simulation during strong helicity injection. Closure of flux surfaces (and high T{sub e}) can occur between voltage spikes if they are sufficiently far apart in time; these topology changes are not reflected in the impedance of the axisymmetric gun. Possible future experimental scenarios in SSPX are examined in the presence of the constraints imposed by reconnection physics.

  2. Place in Transition

    DEFF Research Database (Denmark)

    Mikkelsen, Jacob Bjerre; Lange, Ida Sofie Gøtzsche

    redefinition of oil rigs from an urban design perspective. The paper constitutes a theoretical basis for future design scenarios - exemplified through visionary urban design proposals for a specific site in the city of Esbjerg, Denmark. Relocating rigs to an urban context initiates discussions of conception of...... 'Place' questioning the fixity of 'Place' (Jensen 2010). Scoped through a relational sense of place (Massey 1993) and the potential of exploring new relations between places (Burns & Kahn 2005), the paper challenges the notion of 'Place as God' (Hvattum 2010). These places in transition contest the...

  3. Places of remembrance in citizenship education

    Directory of Open Access Journals (Sweden)

    KInga Majchrzak

    2012-06-01

    Full Text Available The text starts with a short introduction. Then the concept of place is defined and its inherent characteristics are described: its symbolism, multi-sided nature and multidisciplinary connotations. Afterwards the principles of place-based pedagogy are presented and it’s eclectic character is pointed out. Then, attempt is made to explain the idea of the places of remembrance from the standpoint of history and pedagogy. In the final part the author relates to educational potential of places of remembrance and takes a stance on the role of places of remembrance in citizenship education.

  4. Reconnect on Facebook: The Role of Information Seeking Behavior and Individual- and Relationship-Level Factors.

    Science.gov (United States)

    Ramirez, Artemio; Sumner, Erin M; Hayes, Jameson

    2016-08-01

    Social network sites (SNSs) such as Facebook function as both venues for reconnecting with associates from a user's past and sources of social information about them. Yet, little is known about what factors influence the initial decision to reconnect with a past associate. This oversight is significant given that SNSs and other platforms provide an abundance of social information that may be utilized for reaching such decisions. The present study investigated the links among relational reconnection, information seeking (IS) behavior, and individual- and relationship-level factors in user decisions to reconnect on Facebook. A national survey of 244 Facebook users reported on their most recent experience of receiving a friend request from someone with whom they had been out of contact for an extended period. Results indicated that uncertainty about the potential reconnection partner and forecast about the reconnection's potential reward level significantly predicted IS behavior (passive on both target and mutual friends' SNS pages as well as active). However, the emergence of their two-way interaction revealed that the forecasts moderated the IS-uncertainty link on three of the strategies (extractive, both passive approaches). Moreover, social anxiety, sociability, uncertainty about the partner, the forecast about the reconnection's reward level, and extractive and passive (target SNS pages) strategies significantly predicted user decisions to reconnect. Future directions for research on relational reconnection on SNSs are offered. PMID:27447301

  5. Inertial-Range Reconnection in Magnetohydrodynamic Turbulence and in the Solar Wind.

    Science.gov (United States)

    Lalescu, Cristian C; Shi, Yi-Kang; Eyink, Gregory L; Drivas, Theodore D; Vishniac, Ethan T; Lazarian, Alexander

    2015-07-10

    In situ spacecraft data on the solar wind show events identified as magnetic reconnection with wide outflows and extended "X lines," 10(3)-10(4) times ion scales. To understand the role of turbulence at these scales, we make a case study of an inertial-range reconnection event in a magnetohydrodynamic simulation. We observe stochastic wandering of field lines in space, breakdown of standard magnetic flux freezing due to Richardson dispersion, and a broadened reconnection zone containing many current sheets. The coarse-grain magnetic geometry is like large-scale reconnection in the solar wind, however, with a hyperbolic flux tube or apparent X line extending over integral length scales.

  6. Direct observation of high-speed plasma outflows produced by magnetic reconnection in solar impulsive events

    CERN Document Server

    Wang, Tongjiang; Qiu, Jiong

    2007-01-01

    Spectroscopic observations of a solar limb flare recorded by SUMER on SOHO reveal, for the first time, hot fast magnetic reconnection outflows in the corona. As the reconnection site rises across the SUMER spectrometer slit, significant blue- and red-shift signatures are observed in sequence in the Fe XIX line, reflecting upflows and downflows of hot plasma jets, respectively. With the projection effect corrected, the measured outflow speed is between 900-3500 km/s, consistent with theoretical predictions of the Alfvenic outflows in magnetic reconnection region in solar impulsive events. Based on theoretic models, the magnetic field strength near the reconnection region is estimated to be 19-37 Gauss.

  7. Measuring the dayside reconnection rate during an interval of due northward interplanetary magnetic field

    Directory of Open Access Journals (Sweden)

    G. Chisham

    2004-12-01

    Full Text Available This study presents, for the first time, detailed spatiotemporal measurements of the reconnection electric field in the Northern Hemisphere ionosphere during an extended interval of northward interplanetary magnetic field. Global convection mapping using the SuperDARN HF radar network provides global estimates of the convection electric field in the northern polar ionosphere. These are combined with measurements of the ionospheric footprint of the reconnection X-line to determine the spatiotemporal variation of the reconnection electric field along the whole X-line. The shape of the spatial variation is stable throughout the interval, although its magnitude does change with time. Consequently, the total reconnection potential along the X-line is temporally variable but its typical magnitude is consistent with the cross-polar cap potential measured by low-altitude satellite overpasses. The reconnection measurements are mapped out from the ionosphere along Tsyganenko model magnetic field lines to determine the most likely reconnection location on the lobe magnetopause. The X-line length on the lobe magnetopause is estimated to be ~6–11 RE in extent, depending on the assumptions made when determining the length of the ionospheric X-line. The reconnection electric field on the lobe magnetopause is estimated to be ~0.2mV/m in the peak reconnection region.

    Key words. Space plasma physics (Magnetic reconnection – Magnetospheric physics (Magnetopause, cusp and boundary layers – Ionosphere (Plasma convection

  8. The hall effect in magnetic reconnection: Hybrid versus Hall-less hybrid simulations

    Science.gov (United States)

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

    2009-04-01

    To understand the role of the Hall effect during fast magnetic reconnection, hybrid simulations with and without the Hall term in the generalized Ohm's Law are compared, as done originally by Karimabadi et al. (2004). It is found that reconnection with the Hall term is fast, but reconnection in the so-called Hall-less hybrid simulations is Sweet-Parker like (slow) when the resistivity is constant and uniform. These results re-affirm the importance of the Hall term in allowing fast reconnection in the hybrid model.

  9. My Place Is Not Your Place

    DEFF Research Database (Denmark)

    Zenker, Sebastian; Beckmann, Suzanne C.

    2013-01-01

    Purpose – Cities increasingly compete with each other for attracting tourists, investors, companies, or residents. Marketers therefore focus on establishing the city as a brand, disregarding that the perception and knowledge of a city differ dramatically between the target audiences. Hence, place......-ended-question survey with 334 participants. Findings – Structural differences for the city brand perceptions of two different target groups and the differences between perceptions of an external and internal target group are highlighted. The results and the managerial implications for place marketers are discussed...... branding should emphasize much more the perceptions of the different target groups and develop strategies for advanced place brand management. The aim of this paper is to assess the important discrepancies between the city brand perceptions of different target groups with the help of network analysis...

  10. Place Branding in Systems of Place

    DEFF Research Database (Denmark)

    Zenker, Sebastian; Andéhn, Mikael

    2015-01-01

    of place is thought to influence the prospects of branding campaigns and introduce and discuss how reassociation can serve as means of mitigation of negative supranational belongingness. In doing so, we discuss also the challenges of interregional branding in this regard, where perceptions of two (or more.......g. the European Union or Africa). Using the example of nation branding for Sudan and Slovenia, one can identify supranational places such as “sub-Saharan Africa” or “Eastern Europe”, carrying their own highly salient and often negative meaning in much of the Western world. We explore how association to a system...

  11. Populated Places of Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — This coverage contains points that represent populated places, ie. cities, towns, villages or any other named place where people live. The coverage was developed...

  12. A woman's rightful place?

    Science.gov (United States)

    1993-04-01

    Rural development projects in sub-Saharan Africa tend not to succeed because they do not consider women's role and their significance, even though women constitute 70% of agricultural workers, 80% of food producers, 100% of people who prepare meals, and 60-90% do food marketing. Development specialists ignore women because they are not involved in political activities and in decision making. As long as women and women's contributions are not considered, rural development projects will remain inefficient and development will not take place. Thus, projects must include women as agents and beneficiaries of development in key sectors of the economy. Rural development specialists must also consider the effect male labor emigration has on rural women. For example, drought has forced many men to leave their villages, leaving a work force consisting of 95% women to fight desertification. All too often, women have no or limited land ownership rights, thereby keeping them from improving the land, e.g., planting perennial fruit crops. They also tend to be hired hands rather than food producers. They cannot obtain bank loans because they do not own land, and because they are often illiterate (over 90% female illiteracy in 28 African countries), they can neither understand nor complete bank loan forms. Rural development projects further alienate women by aiming training programs to men or by using male agricultural extension agents. Women react to this alienation by rejecting projects that do not benefit them and follow more profitable activities which sometimes interfere with projects. Thus, rural development programs need to invest in women to ensure viable and efficient sustainable development.

  13. Creating Places for People

    Directory of Open Access Journals (Sweden)

    Mehron Kirk

    2013-01-01

    Full Text Available The design of places has a huge impact on the success of urban areas. It has a role in helping develop a vision and identity within the built environment.  Designing public spaces must be centred around the place - its physical characteristics, activities that happen within it, and the emotional reaction of a place. The success of places is governed by the perception of those who use it; we can influence this as designers and continue to create places where people want to live, work, learn and play.

  14. A Study on the Place Attachment Differences of Residents in Tourism Destination: Take Gulangyu Island as an Example%旅游目的地的居民地方依恋差异研究——以鼓浪屿为例

    Institute of Scientific and Technical Information of China (English)

    曾启鸿; 袁书琪

    2011-01-01

    Place attachment is a long time research topic in tourism geography. However, when Chinese people do tourism planning and manage the destination, most of them also pay attention to the management of real environment or recreation facilities. Few people study the place attachment relationship between the resident and the destination. This study takes Gulangyu as an example. By a large number of questionnaires, using relevant statistical software and mathematical analysis, the paper analyzes the relationship between place attachment and the background, ways of tourism and frequency of visitation of local residents, the result shows that such as gender, cultural level,living time,occupation and whether the local people have an impact on the place attachment of residents. However, such as age and activities have no impact on the place attachment of residents, some differences of residents' place attachment are found. On the basis of the study, the paper analyzes the residents cluster basing on the difference of place attachment. Four types of resident are identified; "the daily life", "the emotion approval" , "the sparsely leaving" and "the vital function".%地方依恋近年来成为旅游研究热点.目前国内对旅游地的规划研究与经营管理上,大多还重视实质环境上的经营管理,或是对于旅游设施的投入,并未对居民与游憩地点之间的地方依恋关系进行研究.本研究以鼓浪屿旅游区为例,通过问卷调查,利用相关统计软件和数理分析,了解旅游区的当地居民对特定地方所产生的地方意识,揭示居民的个人背景、旅游活动以及使用频率等因子与地方依恋的关系.研究结果表明:1)不同性别、教育程度及职业的居民在地方依恋的表现上有显著差异;年龄对居民地方依恋的表现没有显著差异;是否是本地人的居民在地方依恋的表现上有显著差异;2)居民的活动行为不同对地方依恋

  15. Final Report: Laboratory Studies of Spontaneous Reconnection and Intermittent Plasma Objects

    Energy Technology Data Exchange (ETDEWEB)

    Egedal-Pedersen, Jan [Massachusetts Institute of Technology; Porkolab, Miklos [Massachusetts Institute of Technology

    2011-05-31

    The study of the collisionless magnetic reconnection constituted the primary work carried out under this grant. The investigations utilized two magnetic configurations with distinct boundary conditions. Both configurations were based upon the Versatile Toroidal Facility (VTF) at the MIT Plasma Science and Fusion Center and the MIT Physics Department. The NSF/DOE award No. 0613734, supported two graduate students (now Drs. W. Fox and N. Katz) and material expenses. The grant enabled these students to operate the VTF basic plasma physics experiment on magnetic reconnection. The first configuration was characterized by open boundary conditions where the magnetic field lines interface directly with the vacuum vessel walls. The reconnection dynamics for this configuration has been methodically characterized and it has been shown that kinetic effects related to trapped electron trajectories are responsible for the high rates of reconnection observed. This type of reconnection has not been investigated before. Nevertheless, the results are directly relevant to observations by the Wind spacecraft of fast reconnection deep in the Earth magnetotail. The second configuration was developed to be relevant to specifically to numerical simulations of magnetic reconnection, allowing the magnetic field-lines to be contained inside the device. The configuration is compatible with the presence of large current sheets in the reconnection region and reconnection is observed in fast powerful bursts. These reconnection events facilitate the first experimental investigations of the physics governing the spontaneous onset of fast reconnection. In the Report we review the general motivation of this work and provide an overview of our experimental and theoretical results enabled by the support through the awards.

  16. A Comparative Study of the Perception on Place-feature of Urban Historic District between Residents and Tourists---Taking Chaozhou Ancient City for Instance%城市历史街区“地方性”的居民感知与游客感知的比较研究∗--以广东潮州古城区为例

    Institute of Scientific and Technical Information of China (English)

    廖春花

    2015-01-01

    Urban historic district displays a city's character,and keeps the most complete memories of the city,and Place-feature is the best fascination of urban historic districts.Urban historic districts in China are now under the critical impact of the economi-cal globalization and the speeding national urbanization,and many a historic district of distinct identity has perished in the course of urban development,and most Chinese cities suffer from a drab uniformity.To solve cities’"characteristic crisis",we must pay great attention to the conservation and revitalization of urban historic districts,and need to assure the inheritance and continuity of the place-feature of urban historic districts.So it is necessary to learn and analyze the local residents'perception about the place-feature of urban historic districts.Taking Chaozhou ancient city for instance,by means of sampling questionnaire survey,the the-sis investigates and analyzes the perception of local residents and tourists in Chaozhou Ancient City about the place-feature of ur-ban historic districts and Chaozhou culture.%城市历史街区是一个城市特色的集中体现,是构成一座城市魅力与活力的核心地区,“地方性”就是城市历史街区的基本特征。旅游开发已经成为城市历史街区地方性重构的一种常用方式,也是城市历史街区进行地方性保护的一种有效途径。在城市历史街区的旅游开发中,了解和分析外来游客与本地居民对城市地方性的认知差异,有助于城市文化旅游的有序发展、消除旅游活动中“主客”之间可能存在的文化摩擦。以广东省潮州古城区为例,以抽样问卷调查为手段,调查和分析了外来游客与本地居民对潮州文化及其地方性感知的差异情况。

  17. Management and communication courses – Places available

    CERN Multimedia

    2012-01-01

    There are places available in some management and communication courses taking place in the period January to March 2013.   For more information on the course, click on the course title, which will bring you to the training catalogue. You can then sign-up on-line. For advice, you can contact: Erwin Mosselmans, tel. 74125, erwin.mosselmans@cern.ch Nathalie Dumeaux, tel. 78144, nathalie.dumeaux@cern.ch Courses in English (or bilingual) Session Duration Language Availability How to get, as a supervisor, the most out of the annual interview 21 January 1 day English 2 places Project Engineering 24 and 25 January 2 days English 6 places How to get, as a supervisor, the most out of the annual interview 31 January 1 day English 6 places Conflict Resolution for Managers 19 and 20 February 2 days English One more place Project Scheduling & Costing 6 and 7 March 2 days English 2 places Communicati...

  18. Parallel Electric Fields Associated with Sub-Solar Reconnection: MMS Observations

    Science.gov (United States)

    Ergun, Robert; Goodrich, Katherine; Wilder, Frederick; Holmes, Justin; Stawarz, Julia; Sturner, Andrew; Eriksson, Stefan; Malaspina, David; Unsanova, Maria; Torbert, Roy; Lindqvist, Per-Arne; Khotyaintsev, Yuri; Burch, James; Strangeway, Robert; Russel, Christopher; Giles, Barbara; Pollock, Craig

    2016-04-01

    We present MMS observations of parallel electric fields associated with sub-solar magnetic reconnection and provide an early interpretation of their implications on the reconnection processes. The MMS satellites have observed many instances of large-amplitude parallel electric fields (10's to greater than 100 mV/m) that appear to lie on or near the magnetic reconnection separatrix, in particular, near a strong current layer on the magnetospheric-side separatrix. These parallel electric field events are directly associated with magnetic reconnection and, on most occasions, are recorded by more than one of the MMS spacecraft. We see several types of parallel electric fields. We interpret purely parallel electrostatic waves and the evolved nonlinear states of these waves as mixing of cold plasma with warm magnetosheath plasma on a freshly reconnected field line. Large-amplitude spikes associated with tangled magnetic fields represent possible secondary reconnection events. Whistler waves and evolved non-linear whistler waves are associated with associated with mixing of plasmas. These observations suggest that (1) magnetic reconnection is often "patchy" and results in tangled magnetic field lines and that (2) cold plasma (<10 eV) is often present in sub-solar reconnection.

  19. The physics of magnetic reconnection onset at the subsolar magnetopause: MMS observations

    Science.gov (United States)

    Retinò, Alessandro

    2016-04-01

    Magnetic reconnection is a fundamental process occurring in thin current sheets where a change in the magnetic field topology leads to fast magnetic energy conversion into charged particles energy. A key yet poorly understood aspect is how reconnection is initiated in the diffusion region by microphysical processes occurring at electron scales, the so-called onset problem. Reconnection onset leads to the energization of particles around reconnection sites, yet the exact energization mechanisms are also not yet fully understood. Simulations have provided some suggestions on the mechanisms responsible for onset and particle energization, however direct observations have been scarce so far. The four-spacecraft Magnetospheric Multiscale Mission (NASA/MMS) has been launched in March 2015 and allows, for the first time, in-situ observations of reconnection diffusion regions with adequate resolution to study electron scales. Here we present MMS observations in diffusion regions at the subsolar magnetopause and we investigate the conditions for reconnection onset. We select a few events with multiple crossings of the magnetopause current sheet for which signatures of absence of reconnection are rapidly followed by signatures of reconnection, and compare the measured electric field with the electric field due to both kinetic effects (electron pressure tensor, electron inertia terms) and to anomalous resistivity associated to different wave modes (e.g. lower hybrid waves, whistler waves, etc.). We also analyze electron distribution functions to study the mechanisms of electron energization in the diffusion region.

  20. Teenagers and Risk-Taking at Camp.

    Science.gov (United States)

    Woods, Ann

    2002-01-01

    Teen risk-taking is normal, healthy developmental behavior. Teens act out their fantasies--good and bad--at camp because it is a safe place away from parents. Signs of unhealthy risk-taking, camp staff responses, and how the September 11 tragedy might affect risk-taking are discussed. Sidebars describe tips for understanding adolescent behavior…

  1. Ellerman Bombs, Type II White-light Flares and Magnetic Reconnection in the Solar Lower Atmosphere

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ellerman bombs and Type II white-light flares share many common features despite the large energy gap between them. Both are considered to result from local heating in the solar lower atmosphere. This paper presents numerical simulations of magnetic reconnection occurring in such a deep atmosphere, with the aim to account for the common features of the two phenomena. Our numerical results manifest the following two typical characteristics of the assumed reconnection process: (1) magnetic reconnection saturates in ~600-900 s, which is just the lifetime of the two phenomena; (2) ionization in the upper chromosphere consumes quite a large part of the energy released through reconnection, making the heating effect most significant in the lower chromosphere. The application of the reconnection model to the two phenomena is discussed in detail.

  2. Model of Reconnection of Weakly Stochastic Magnetic Field and its Implications

    CERN Document Server

    Lazarian, A

    2008-01-01

    We discuss the model of magnetic field reconnection in the presence of turbulence introduced by us approximately ten years ago. The model does not require any plasma effects to be involved in order to make the reconnection fast. In fact, it shows that the degree of magnetic field stochasticity controls the reconnection. The turbulence in the model is assumed to be subAlfvenic, with the magnetic field only slightly perturbed. This ensures that the reconnection happens in generic astrophysical environments and the model does not appeal to any unphysical concepts, similar to the turbulent magnetic diffusivity concept, which is employed in the kinematic magnetic dynamo. The interest to that model has recently increased due to successful numerical testings of the model predictions. In view of this, we discuss implications of the model, including the first-order Fermi acceleration of cosmic rays, that the model naturally entails, bursts of reconnection, that can be associated with Solar flares, as well as, removal ...

  3. Magnetic Reconnection and Turbulent Mixing From ISM to Clusters of Galaxies

    CERN Document Server

    Lazarian, A

    2004-01-01

    Magnetic reconnection, or the ability of the magnetic field lines that are frozen in plasma to change their topology, is a fundamental problem of magnetohydrodynamics (MHD). We briefly examine the problem starting with the well-known Sweet-Parker scheme, discuss effects of tearing modes, anomalous resistivity and the concept of hyperresistivity. We show that the field stochasticity by itself provides a way to enable fast reconnection even if, at the scale of individual turbulent wiggles, the reconnection happens at the slow Sweet-Parker rate. We show that fast reconnection allows efficient mixing of magnetic field in the direction perpendicular to the local direction of magnetic field. While the idea of stochastic reconnection still requires numerical confirmation, our numerical simulations testify that mixing motions perpendicular to the local magnetic field are up to high degree hydrodynamical. This suggests that the turbulent heat transport should be similar to that in non-magnetized turbulent fluid, namel...

  4. Stochastic reacceleration of relativistic electrons by turbulent reconnection: a mechanism for cluster-scale radio emission ?

    CERN Document Server

    Brunetti, G

    2016-01-01

    In this paper we investigate a situation where relativistic particles are reaccelerated diffusing across regions of reconnection and magnetic dynamo in super-Alfvenic, incompressible large-scale turbulence. We present an exploratory study of this mechanism in the intra-cluster-medium (ICM). In view of large-scale turbulence in the ICM we adopt a reconnection scheme that is based on turbulent reconnection and MHD turbulence. In this case particles are accelerated and decelerated in a systematic way in reconnecting and magnetic-dynamo regions, respectively, and on longer time-scales undergo a stochastic process diffusing across these sites (similar to second-order Fermi). Our study extends on larger scales numerical studies that focused on the acceleration in and around turbulent reconnecting regions. We suggest that this mechanism may play a role in the reacceleration of relativistic electrons in galaxy clusters providing a new physical scenario to explain the origin of cluster-scale diffuse radio emission. In...

  5. Structures of magnetic null points in reconnection diffusion region: Cluster observations

    Institute of Scientific and Technical Information of China (English)

    HU YunHui; R.NAKAMURA; W.BAUMJOHANN; H.R'EME; C.M.CARR; DENG XiaoHua; ZHOU Meng; TANG RongXin; ZHAO Hui; FU Song; SU ZhiWen; WANG JingFang; YUAN ZhiGang

    2008-01-01

    Magnetic reconnection is a very important and fundamental plasma process in transferring energy from magnetic field into plasma. Previous theory, numerical simulations and observations mostly concen-trate on 2-dimensional (2D) model; however, magnetic reconnection is a 3-dimensional (3D) nonlinear process in nature. The properties of reconnection in 3D and its associated singular structure have not been resolved completely. Here we investigate the structures and characteristics of null points inside the reconnection diffusion region by introducing the discretized Poincaré index through Gauss integral and using magnetic field data with high resolution from the four satellites of Cluster mission. We esti-mate the velocity and trajectory of null points by calculating its position in different times, and compare and discuss the observations with different reconnection models with null points based on character-istics of electric current around null points.

  6. Flow reversals in turbulent convection via vortex reconnections

    CERN Document Server

    Chandra, Mani

    2012-01-01

    We employ detailed numerical simulations to probe the mechanism of flow reversals in two-dimensional turbulent convection. We show that the reversals occur via vortex reconnection of two attracting corner rolls having same sign of vorticity, thus leading to major restructuring of the flow. Large fluctuations in heat transport are observed during the reversal due to this flow reconfiguration. The flow configurations during the reversals have been analyzed quantitatively using large-scale modes. Using these tools, we also show why flow reversals occur for a restricted range of Rayleigh and Prandt numbers.

  7. Pressure-driven reconnection and quasi periodical oscillations in plasmas

    Science.gov (United States)

    Paccagnella, R.

    2014-03-01

    This paper presents a model for an ohmically heated plasma in which a feedback exists between thermal conduction and transport, on one side, and the magneto-hydro-dynamical stability of the system, on the other side. In presence of a reconnection threshold for the magnetic field, a variety of periodical or quasi periodical oscillations for the physical quantities describing the system are evidenced. The model is employed to interpret the observed quasi periodical oscillations of electron temperature and perturbed magnetic field around the so called "Single Helical" state in the reversed field pinch, but its relevance for other periodical phenomena observed in magnetic confinement systems, especially in tokamaks, is suggested.

  8. Color reconnection at future e+e- colliders

    International Nuclear Information System (INIS)

    The effects of color reconnection (CR) at e+e- colliders are revisited, with focus on recently developed CR models. The new models are compared with the LEP2 measurements for e+e- → W+W- → q1 anti q2q3 anti q4 and found to lie within their limits. Prospects for constraints from new high-luminosity e+e- colliders are discussed. The novel arena of CR in Higgs decays is introduced, and it is illustrated by shifts in angular correlations that would be used to set limits on a potential CP-odd admixture of the 125 GeV Higgs state. (orig.)

  9. CORE ELECTRON HEATING IN SOLAR WIND RECONNECTION EXHAUSTS

    International Nuclear Information System (INIS)

    We present observational evidence of core electron heating in solar wind reconnection exhausts. We show two example events, one which shows clear heating of the core electrons within the exhaust, and one which demonstrates no heating. The event with heating occurred during a period of high inflow Alfvén speed (V AL), while the event with no heating had a low V AL. This agrees with the results of a recent study of magnetopause exhausts, and suggests that similar core electron heating can occur in both symmetric (solar wind) and asymmetric (magnetopause) exhausts

  10. The value of place

    Science.gov (United States)

    Dentzau, Michael W.

    2014-03-01

    This commentary seeks to expand the dialogue on place-based science education presented in Katie Lynn Brkich's article, where the connections fifth grade students make between their formal earth science curriculum and their lived experiences are highlighted. The disconnect between the curriculum the students are offered and their immediate environment is clear, and we are presented with examples of how they strive to make connections between the content and what they are familiar with—namely their surroundings. "Place" is identified as a term with complex meanings and interpretations, even in the scope of place-based science education, and understanding how the term is used in any given scenario is essential to understanding the implications of place-based education. Is place used as a location, locale or a sense of place? To understand "place" is to acknowledge that for the individual, it is highly situational, cultural and personal. It is just such attributes that make place-based education appealing, and potentially powerful, pedagogically on one hand, yet complex for implementation on the other. The argument is posed that place is particularly important in the context of education about the environment, which in its simplest manifestation, connects formal science curriculum to resources that are local and tangible to students. The incorporation of place in such a framework seeks to bridge the gap between formal school science subjects and students' lived experiences, yet acknowledges the tensions that can arise between accommodating place meanings and the desire to acculturate students into the language of the scientific community. The disconnect between guiding policy frameworks and the reality of the Next Generation Science Standards is addressed opening an avenue for further discussion of the importance of socio-cultural frameworks of science learning in an ever increasing era of accountability.

  11. Using radiative energy losses to constrain the magnetisation and magnetic reconnection rate at the base of black hole jets

    CERN Document Server

    Potter, William J

    2016-01-01

    We calculate the severe radiative energy losses which occur at the base of black hole jets using a relativistic fluid jet model, including in-situ acceleration of non-thermal leptons by magnetic reconnection. Our results demonstrate that including a self-consistent treatment of radiative energy losses is necessary to perform accurate MHD simulations of powerful jets and that jet spectra calculated via post-processing are liable to vastly overestimate the amount of non-thermal emission. If no more than 95% of the initial total jet power is radiated away by the plasma travels as it travels along the length of the jet, we can place a lower bound on the magnetisation of the jet plasma at the base of the jet. For typical powerful jets, we find that the plasma at the jet base is required to be highly magnetised, with at least 10,000 times more energy contained in magnetic fields than in non-thermal leptons. Using a simple power-law model of magnetic reconnection, motivated by simulations of collisionless reconnecti...

  12. Teaching Bodies in Place

    Science.gov (United States)

    Jones, Stephanie; Woglom, James F.

    2013-01-01

    Background/Context: This piece draws on literature in justice-oriented teacher education, feminist pedagogy, and postmodern notions of bodies and place to make sense of data generated from a three-year study of an undergraduate teacher education course. A feminist lens was used to engage a body- and place-focused pedagogy that aimed to engage…

  13. Technical training: places available

    CERN Multimedia

    HR Department

    2007-01-01

    CERN Technical Training: Open Courses (April - June 2007) The following course sessions are currently scheduled in the framework of the CERN Technical Training Programme 2007:   AutoCAD 2006 - niveau 1 (course in French): 25.4.- 26.4.2007 & 2.5. - 3.5.2007 (4 days in 2 modules, 5 places available) AutoCAD 2006 - niveau 1 (course in French): 27.6.- 28.6.2007 & 3.7. - 4.7.2007 (4 days in 2 modules, 5 places available) AutoCAD Mechanical 2006 (course in French) 21.6.-22.6.2007 (2 days, 8 places available) * NEW COURSE* Automate de securite S7 (course in French) 14.5.-16.5.2007 (3 days, 4 places available) * NEW COURSE* Automate de securite S7 (course in French): 9.5.-11.5.2007 (3 days, 4 places available) JCOP - Joint PVSS-JCOP Frameswork (course in English): 21.5.-25.5.2007 (5 days, 12 places available) JCOP - Finite State Machines in the JCOP Frameswork (course in English): 12.6.-14.6.2007 (3 days, 12 places available) LabVIEW Basics 1 (in English): 2.-4.5.2007 (3 days, 7 places ...

  14. Technical training - places available

    CERN Multimedia

    2012-01-01

    If you would like more information on a course, or for any other inquiry/suggestions, please contact Technical.Training@cern.ch Valeria Perez Reale, Learning Specialist, Technical Programme Coordinator (Tel.: 62424) Eva Stern and Elise Romero, Technical Training Administration (Tel.: 74924) HR Department »Electronics design Next Session Duration Language Availability Comprehensive VHDL for FPGA Design 08-Oct-12 to 12-Oct-12 5 days English 3 places available Foundations of Electromagnetism and Magnet Design (EMAG) 14-Nov-12 to 27-Nov-12 6 days English 20 places available Impacts de la suppression du plomb (RoHS) en électronique 26-Oct-12 to 26-Oct-12 8 hours French 15 places available Introduction to VHDL 10-Oct-12 to 11-Oct-12 2 days English 7 places available LabVIEW Real Time and FPGA 13-Nov-12 to 16-Nov-12 5 days French 5 places available »Mechanical design Next Se...

  15. Using the fingerprints of solar magnetic reconnection to identify the elemental building blocks of the slow solar wind

    Science.gov (United States)

    Kepko, Larry; Viall, Nicholeen M.; Kasper, Justin; Lepri, Sue

    2015-04-01

    While the source of the fast solar wind is well understood to be linked to coronal holes, the source of the slow solar wind has remained elusive. Many previous studies of the slow solar wind have examined trends in the composition and charge states over long time scales and found strong relationships between the solar wind velocity and these plasma parameters. These relationships have been used to constrain models of solar wind source and acceleration. In this study, we take advantage of high time resolution (12 min) measurements of solar wind composition and charge-state abundances recently reprocessed by the ACE Solar Wind Ion Composition Spectrometer (SWICS) science team to probe the timescales of solar wind variability at relatively small scales. We study an interval of slow solar wind containing quasi-periodic 90 minute structures and show that they are remnants of solar magnetic reconnection. Each 90-minute parcel of slow solar wind, though the speed remains steady, exhibits the complete range of charge state and composition variations expected for the entire range of slow solar wind, which is repeated again in the next 90-minute interval. These observations show that previous statistical results break down on these shorter timescales, and impose new and important constraints on models of slow solar wind creation. We conclude by suggesting these structures were created through interchange magnetic reconnection and form elemental building blocks of the slow solar wind. We also discuss the necessity of decoupling separately the process(es) responsible for the release and acceleration.

  16. Measurements of Fast Magnetic Reconnection Driven by Relativistic Electrons

    Science.gov (United States)

    Raymond, Anthony; McKelvey, Andrew; Zulick, Calvin; Chuanfei, Dong; Maksimchuk, Anatoly; Thomas, Alexander; Yanovsky, Victor; Krushelnick, Karl; Willingale, Louise; Chykov, Vladimir; Nilson, Phil; Chen, Hui; Williams, Gerald; Bhattacharjee, Amitava; Fox, Will

    2015-11-01

    Magnetic reconnection is a process whereby opposing magnetic field lines are forced together and topologically rearrange, resulting in lower magnetic potential energy and in corresponding plasma heating. Such occurrences are ubiquitous in astrophysics as well as appearing in laboratory plasmas such as in ICF in the form of instabilities. We report measurements in the domain of ultra-fast, ultra-intense lasers, in which the mechanism responsible follows from radially expanding surface electrons with v ~ c . Results are compared from two laser facilities (HERCULES and Omega EP), both of which produced two relativistic intensity pulses focused within close proximity onto copper foils. A spherical X-ray crystal was used to image the Kα radiation induced by electron currents, revealing the midplane diffusion region wherein electrons are accelerated into the target by the electric field generated during reconnection. The characteristics of this signal are studied as a function of the focal spot separation, laser energy, and pulse duration. The results are then compared to 3D PIC simulations.

  17. Orientation of x-lines in asymmetric magnetic reconnection

    Science.gov (United States)

    Liu, Yi-Hsin; Hesse, Michael; Kuznetsova, Masha

    2015-11-01

    At Earth's magnetopause, reconnection proceeds asymmetrically between magnetosheath plasmas, namely solar wind plasmas compressed by Earth's bow shock, and magnetospheric plasmas. In an asymmetric configuration, it is unclear if there is a simple principle to determine the orientation of the x-line. Using fully kinetic simulations, we study this issue and a spatially localized perturbation is employed to induce a single x-line, that has sufficient freedom to choose its orientation in three-dimensional systems. The effect of ion to electron mass ratio is investigated, and the x-line appears to bisect the magnetic shear angle across the current sheet in the large mass ratio limit. The deviation from the bisection angle in the lower mass ratio limit can be explained by the physics of tearing instability. The local physics control of the x-line orientation studied in this slab geometry could potentially interplay with global geometrical effects to determine the location of collisionless magnetic reconnection at Earth's magnetopause.

  18. Magnetic reconnection acceleration of astrophysical jets for different jet geometries

    International Nuclear Information System (INIS)

    The acceleration mechanisms of relativistic jets are of great importance for understanding various astrophysical phenomena such as gamma-ray bursts, active galactic nuclei and microquasars. One of the most popular scenarios is that the jets are initially Poynting-flux dominated and succumb to magnetohydrodynamic instability leading to magnetic reconnections. We suggest that the reconnection timescale and efficiency could strongly depend on the geometry of the jet, which determines the length scale on which the orientations of the field lines change. In contrast to a usually-assumed conical jet, the acceleration of a collimated jet can be found to be more rapid and efficient (i.e. a much more highly saturated Lorentz factor can be reached) while the jets with lateral expansion show the opposite behavior. The shape of the jet could be formed due to the lateral squeezing on the jet by the stellar envelope of a collapsing massive star or the interaction of the jet with stellar winds. (paper)

  19. Localized Electron Heating by Strong Guide-Field Magnetic Reconnection

    Science.gov (United States)

    Guo, Xuehan; Sugawara, Takumichi; Inomoto, Michiaki; Yamasaki, Kotaro; Ono, Yasushi; UTST Team

    2015-11-01

    Localized electron heating of magnetic reconnection was studied under strong guide-field (typically Bt 15Bp) using two merging spherical tokamak plasmas in Univ. Tokyo Spherical Tokamak (UTST) experiment. Our new slide-type two-dimensional Thomson scattering system documented for the first time the electron heating localized around the X-point. The region of high electron temperature, which is perpendicular to the magnetic field, was found to have a round shape with radius of 2 [cm]. Also, it was localized around the X-point and does not agree with that of energy dissipation term Et .jt . When we include a guide-field effect term Bt / (Bp + αBt) for Et .jt where α =√{ (vin2 +vout2) /v∥2 } , the energy dissipation area becomes localized around the X-point, suggesting that the electrons are accelerated by the reconnection electric field parallel to the magnetic field and thermalized around the X-point. This work was supported by JSPS A3 Foresight Program ``Innovative Tokamak Plasma Startup and Current Drive in Spherical Torus,'' a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS) Fellows 15J03758.

  20. Jet formation in solar atmosphere due to magnetic reconnection

    CERN Document Server

    González-Avilés, J J; Fedun, V

    2016-01-01

    Using numerical simulations, we show that jets with features of type II spicules and cold coronal jets corresponding to temperatures $10^{4}$ K can be formed due to magnetic reconnection in a scenario in presence of magnetic resistivity. For this we model the low chromosphere-corona region using the C7 equilibrium solar atmosphere model and assuming Resistive MHD rules the dynamics of the plasma. The magnetic filed configurations we analyze correspond to two neighboring loops with opposite polarity. The separation of the loops' feet determines the thickness of a current sheet that triggers a magnetic reconnection process, and the further formation of a high speed and sharp structure. We analyze the cases where the magnetic filed strength of the two loops is equal and different. In the first case, with a symmetric configuration the spicules raise vertically whereas in an asymmetric configuration the structure shows an inclination. With a number of simulations carried out under a 2.5D approach, we explore vario...

  1. Helicity, topology, and Kelvin waves in reconnecting quantum knots

    Science.gov (United States)

    Clark di Leoni, P.; Mininni, P. D.; Brachet, M. E.

    2016-10-01

    Helicity is a topological invariant that measures the linkage and knottedness of lines, tubes, and ribbons. As such, it has found myriads of applications in astrophysics, fluid dynamics, atmospheric sciences, and biology. In quantum flows, where topology-changing reconnection events are a staple, helicity appears as a key quantity to study. However, the usual definition of helicity is not well posed in quantum vortices, and its computation based on counting links and crossings of centerline vorticity can be downright impossible to apply in complex and turbulent scenarios. We present a definition of helicity which overcomes these problems and which gives the expected result in the large-scale limit. With it, we show that certain reconnection events can excite Kelvin waves and other complex motions of the centerline vorticity, which slowly deplete helicity as they interact nonlinearly, thus linking the theory of vortex knots with observations of quantum fluids. This process also results in the depletion of helicity in a fully turbulent quantum flow, in a way reminiscent of the decay of helicity in classical fluids.

  2. Turbulent transport in 2D collisionless guide field reconnection

    CERN Document Server

    Muñoz, P A; Kilian, P

    2016-01-01

    Transport in collisionless plasmas is usually called anomalous, being due to the interaction between the particles and the self-generated turbulence by their collective interactions. 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. We analyze the anomalous transport properties by using 2.5D Particle-in-Cell (PiC) 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 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 st...

  3. OBSERVATION OF MAGNETIC RECONNECTION DRIVEN BY GRANULAR SCALE ADVECTION

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-06-01

    We report the first evidence of magnetic reconnection driven by advection in a rapidly developing large granule using high spatial resolution observations of a small surge event (base size {approx} 4'' Multiplication-Sign 4'') with the 1.6 m aperture New Solar Telescope at the Big Bear Solar Observatory. The observations were carried out in narrowband (0.5 A) He I 10830 A and broadband (10 A) TiO 7057 A. Since He I 10830 A triplet has a very high excitation level and is optically thin, its filtergrams enable us to investigate the surge from the photosphere through the chromosphere into the lower corona. Simultaneous space data from the Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory were used in the analysis. It is shown that the surge is spatio-temporally associated with magnetic flux emergence in the rapidly developing large granule. During the development of the granule, its advecting flow ({approx}2 km s{sup -1}) squeezed the magnetic flux into an intergranular lane area, where a magnetic flux concentration was formed and the neighboring flux with opposite magnetic polarity was canceled. During the cancellation, the surge was produced as absorption in He I 10830 A filtergrams while simultaneous EUV brightening occurred at its base. The observations clearly indicate evidence of a finest-scale reconnection process driven by the granule's motion.

  4. Breakout Reconnection Observed by the TESIS EUV Telescope

    CERN Document Server

    Reva, Anton; Shestov, Sergey; Kuzin, Sergey

    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 $R_\\odot$ from the Sun center in the Fe 171 \\AA\\ line. Starting from 2009 April 8 TESIS, observed an active region (AR) that had a quadrupolar structure with an X-point 0.5 $R_\\odot$ above photosphere. A reconstructed from the MDI data magnetic field 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 $\\approx$ 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 \\AA\\ 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...

  5. 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.

  6. 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.

  7. Planned place of birth

    DEFF Research Database (Denmark)

    Overgaard, Charlotte; Coxon, Kirstie; Stewart, Mary

    Title Planned place of birth: issues of choice, access and equity. Outline In Northern European countries, giving birth is generally safe for healthy women with uncomplicated pregnancies, and their babies. However, place of birth can affect women’s outcomes and experiences of birth. Whilst tertiary...... in Denmark Coxon K et al: Planned place of birth in England: perceptions of accessing obstetric units, midwife led units and home birth amongst women and their partners. How these papers interrelate These papers draw upon recent research in maternity care, undertaken in Denmark and in England. In both...

  8. Management and communication courses – Places available

    CERN Multimedia

    2013-01-01

    There are places available in some management and communication courses taking place in the period April to June 2013.   For more information on the course, click on the course title, this will bring you to the training catalogue. You can then sign-up online. For advice, you can contact: - Erwin Mosselmans, tel. 74125, erwin.mosselmans@cern.ch - Nathalie Dumeaux, tel. 78144, nathalie.dumeaux@cern.ch Courses in English (or bilingual) Sessions Duration Language Availability Managing stress 29 and 30 May 2 days English 3 places Making Presentations 30, 31 May & 25 June 3 days English 2 places Communicating Effectively - Residential course 4 to 6 June 3 days Bilingual 9 places Handling difficult conversations (Adapted from Dealing with Conflict) 7 and 14 June and 13 September 3 days English 6 places Voice and Nonverbal Behaviour in Speech Communication 17 and 18 June 1 day 4 hours English 7 plac...

  9. Technical training - Places available

    CERN Multimedia

    2012-01-01

    If you would like more information on a course, or for any other inquiry/suggestions, please contact Technical.Training@cern.ch Valeria Perez Reale, Learning Specialist, Technical Programme Coordinator (Tel.: 62424) Eva Stern and Elise Romero, Technical Training Administration (Tel.: 74924)   Electronics design Next Session Duration Language Availability Certified LabVIEW Associate Developer (CLAD) 06-Dec-12 to 06-Dec-12 1 hour English One more place available Compatibilité électromagnetique (CEM): Applications 23-Nov-12 to 23-Nov-12 3.5 hours English 3 places available Compatibilité électromagnétique (CEM): Introduction 23-Nov-12 to 23-Nov-12 3 hours English 43 places available Effets des Radiations sur les composants et systèmes électroniques 11-Dec-12 to 12-Dec-12 1 day 4 hours French 9 places available LabVIEW for beginners ...

  10. History, Criticism and Place

    DEFF Research Database (Denmark)

    Hinds, Mat; Carter, Adrian; Malpas, Jeff

    2012-01-01

    Rory Spence and Richard Leplastrier shared a conversation and friendship that lasted 20years until Spence's death in 2004. The discussions focused largely upon issues of place, distilled through the practice of Leplastrier....

  11. Marine Place Names

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains the geographic place names for features in the U.S territorial waters and outer continental shelf. These names can be used to find or define...

  12. Iris si iv line profiles: An indication for the plasmoid instability during small-scale magnetic reconnection on the sun

    CERN Document Server

    Innes, Davina; Huang, YiMin; Bhattacharjee, Amitava

    2015-01-01

    Our understanding of the process of fast reconnection has undergone a dramatic change in the last 10 years driven, in part, by the availability of high-resolution numerical simulations that have consistently demonstrated the break-up of current sheets into magnetic islands, with reconnection rates that become independent of Lundquist number, challenging the belief that fast magnetic reconnection in flares proceeds via the Petschek mechanism that invokes pairs of slow-mode shocks connected to a compact diffusion region. The reconnection sites are too small to be resolved with images but these reconnection mechanisms, Petschek and the plasmoid instability, have reconnection sites with very different density and velocity structures and so can be distinguished by high-resolution line-profiles observations. Using IRIS spectroscopic observations we obtain a survey of typical line profiles produced by small-scale events thought to be reconnection sites on the Sun. Slit-jaw images are used to investigate the plasma h...

  13. Technical training - Places available

    CERN Multimedia

    2012-01-01

    If you would like more information on a course, or for any other inquiry/suggestions, please contact Technical.Training@cern.ch Valeria Perez Reale, Learning Specialist, Technical Programme Coordinator (Tel.: 62424) Eva Stern and Elise Romero, Technical Training Administration (Tel.: 74924) HR Department Electronic Design Next Session Duration Language Availability Comprehensive VHDL for FPGA Design 08-Oct-12 to 12-Oct-12 5 days English 4 places Electrostatique / Protection ESD 28-Sep-12 to 28-Sep-12 3 hours French 25 places Impacts de la suppression du plomb (RoHS) en électronique 26-Oct-12 to 26-Oct-12 8 hours French 14 places Introduction to VHDL 10-Oct-12 to 11-Oct-12 2 days English 9 places LabVIEW Real Time and FPGA 13-Nov-12 to 16-Nov-12 5 days French 5 places LabVIEW for Experts 24-Sep-12 to 28-Sep-12 5 days English 6 places LabVIEW for beginners 15-Oct-12 to 17-...

  14. Particle Heating and Energization During Magnetic Reconnection Events in MST Plasmas

    Science.gov (United States)

    Dubois, Ami M.; Almagri, A. F.; Anderson, J. K.; den Hartog, D. J.; Forest, C.; Nornberg, M.; Sarff, J. S.

    2015-11-01

    Magnetic reconnection plays an important role in particle transport, energization, and acceleration in space, astrophysical, and laboratory plasmas. In MST reversed field pinch plasmas, discrete magnetic reconnection events release large amounts of energy from the equilibrium magnetic field, resulting in non-collisional ion heating. However, Thomson Scattering measures a decrease in the thermal electron temperature. Recent fast x-ray measurements show an enhancement in the high energy x-ray flux during reconnection, where the coupling between edge and core tearing modes is essential for enhanced flux. A non-Maxwellian energetic electron tail is generated during reconnection, where the power law spectral index (γ) decreases from 4.3 to 1.8 and is dependent on density, plasma current, and the reversal parameter. After the reconnection event, γ increases rapidly to 5.8, consistent with the loss of energetic electrons due to stochastic thermal transport. During the reconnection event, the change in γ is correlated with the change in magnetic energy stored in the equilibrium field, indicating that the released magnetic energy may be an energy source for electron energization. Recent experimental and computational results of energetic electron tail formation during magnetic reconnection events will be presented. This work is supported by the U.S. DOE and the NSF.

  15. BIDIRECTIONAL OUTFLOWS AS EVIDENCE OF MAGNETIC RECONNECTION LEADING TO A SOLAR MICROFLARE

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Jie; Ding, M. D.; Li, Ying; Yang, Kai; Cheng, Xin; Fang, Cheng [School of Astronomy and Space Science, Nanjing University, Nanjing 210023 (China); Chen, Feng [Max-Plank-Institut für Sonnensystemforschung, D-37077, Göttingen (Germany); Cao, Wenda, E-mail: dmd@nju.edu.cn [Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314-9672 (United States)

    2016-03-20

    Magnetic reconnection is a rapid energy release process that is believed to be responsible for flares on the Sun and stars. Nevertheless, such flare-related reconnection is mostly detected to occur in the corona, while there have been few studies concerning the reconnection in the chromosphere or photosphere. Here, we present both spectroscopic and imaging observations of magnetic reconnection in the chromosphere leading to a microflare. During the flare peak time, chromospheric line profiles show significant blueshifted/redshifted components on the two sides of the flaring site, corresponding to upflows and downflows with velocities of ±(70–80) km s{sup −1}, comparable with the local Alfvén speed as expected by the reconnection in the chromosphere. The three-dimensional nonlinear force-free field configuration further discloses twisted field lines (a flux rope) at a low altitude, cospatial with the dark threads in He i 10830 Å images. The instability of the flux rope may initiate the flare-related reconnection. These observations provide clear evidence of magnetic reconnection in the chromosphere and show the similar mechanisms of a microflare to those of major flares.

  16. How does mass loading impact local versus global control on dayside reconnection?

    Science.gov (United States)

    Zhang, B.; Brambles, O. J.; Wiltberger, M.; Lotko, W.; Ouellette, J. E.; Lyon, J. G.

    2016-03-01

    This paper investigates the effects of magnetospheric mass loading on the control of dayside magnetic reconnection using global magnetospheric simulations. The study iys motivated by a recent debate on whether the integrated dayside magnetic reconnection rate is solely controlled by local processes (local-control theory) or global merging processes (global-control theory). The local-control theory suggests that the integrated dayside reconnection rate is controlled by the local plasma parameters. The global-control theory argues that the integrated rate is determined by the net force acting on the flow in the magnetosheath rather than the local microphysics. Controlled numerical simulations using idealized ionospheric outflow specifications suggest a possible mixed-control theory, that is, (1) a small amount of mass loading at the dayside magnetopause only redistributes local reconnection rate without a significant change in the integrated reconnection rate and (2) a large amount of mass loading reduces both local reconnection rates and the integrated reconnection rate on the dayside. The transition between global-control- and local-control-dominated regimes depends on (but not limited to) the source region, the amount, the location, and the spatial extension of the mass loading at the dayside magnetopause.

  17. Simulation of turbulent magnetic reconnection in the small-scale solar wind

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Some observational examples for the possible occurrence of the turbulent magnetic reconnection in the solar wind are found by analysing Helios spacecraft's high resolution data. The phenomena of turbulent magnetic reconnections in small scale solar wind are simulated by introducing a third order accuracy upwind compact difference scheme to the compressible two_dimensional MHD flow. Numerical results verify that the turbulent magnetic reconnection process could occur in small scale interplanetary solar wind, which is a basic feature characterizing the magnetic reconnection in high_magnetic Reynolds number (RM=2 000-10 000) solar wind. The configurations of the magnetic reconnection could evolve from a single X_line to a multiple X-line reconnection, exhibiting a complex picture of the formation, merging and evolution of magnetic islands, and finally the magnetic reconnection would evolve into a low_energy state. Its life_span of evolution is about one hour order of magnitude. Various magnetic and flow signatures are recorded in the numerical test for different evolution stages and along different crossing paths, which could in principle explain and confirm the observational samples from the Helios spacecraft. These results are helpful for revealing the basic physical processes in the solar wind turbulence.

  18. The Suitability Evaluation of the Intangible Cultural Heritage Tourism Development---Taking Hui’an Female’s Gathering Place as an Example%非物质文化遗产旅游开发适宜性评价研究*--以惠安女聚集地为例

    Institute of Scientific and Technical Information of China (English)

    朱赟; 叶新才

    2015-01-01

    Referring to FAO land suitability evaluation and the evaluation system of traditional tourism resources,the paper con-structs the evaluation system of intangible cultural heritage tourism suitability from the perspective of intangible cultural heritage quality,social and economic conditions and the ecological environment,and uses a combined method of AHP and expert consulta-tion to determine the index weight.Meanwhile,the paper takes Hui’an female’s gathering place as an example to do the empiri-cal research.Through the comprehensive evaluation of the intangible cultural heritage resources of three towns,the development model of Chongwu Town is decided as deeply-developed theme park of intangible cultural heritage;Xiaozuo Town is moderate-de-veloped real-life staged scenery of intangible cultural heritage,and the model of Jingfeng Town is limited-developed museum of in-tangible cultural heritage.By choosing the suitable tourism development model,the paper wishes to help realize the inheritance and protection of the intangible cultural heritage resources of Hui’an female gathering place motivated by tourism development.%参考 FAO土地适宜性评价同传统旅游资源评价体系,从非物质文化遗产质量、社会经济条件和生态环境条件的角度构建非物质文化遗产旅游开发适宜性评价体系,采用层次分析与专家咨询相结合的方法确定指标权重。同时以惠安女聚集地为例进行实证研究,通过对三镇非物质文化遗产资源的综合评价分析,确定崇武镇为深度开发的非遗主题公园开发模式,小岞镇为适度开发的非遗实景舞台剧开发模式,净峰镇为限制开发的非遗博物馆模式。以期通过合理的旅游开发模式选择,实现旅游开发带动的惠安女聚集地非物质文化遗产资源的传承与保护。

  19. Spatial distribution of Mercury's flux ropes and reconnection fronts: MESSENGER observations

    Science.gov (United States)

    Sun, W. J.; Fu, S. Y.; Slavin, J. A.; Raines, J. M.; Zong, Q. G.; Poh, G. K.; Zurbuchen, T. H.

    2016-08-01

    We perform a statistical study of flux ropes and reconnection fronts based on MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER) magnetic field and plasma observations to study the implications for the spatial distribution of reconnection sites in Mercury's near magnetotail. The results show important differences of temporal and spatial distributions as compared to Earth. We have surveyed the plasma sheet crossings between -2 RM and -3 RM downtail from the planet, i.e., the location of Near-Mercury Neutral Line (NMNL). Plasma sheets were defined to be regions with β ≥ 0.5. Using this definition, 39 flux ropes and 86 reconnection fronts were identified in the plasma sheet. At Mercury, the distributions of flux ropes and reconnection fronts show clear dawn-dusk asymmetry with much higher occurrence rate on the dawnside plasma sheet than on the duskside. This suggests that magnetic reconnection in Mercury's magnetotail occurs more frequently in the dawnside than in the duskside plasma sheet, which is different than the observations in Earth's magnetotail showing more reconnection signatures in the duskside plasma sheet. The distribution of plasma sheet thickness shows that plasma sheet near the midnight is the thinnest part and does not show obvious asymmetry. Thus, the reasons that cause magnetic reconnection to preferentially occur on the dawnside of the magnetotail at Mercury may not be the plasma sheet thickness and require further study. The peak occurrence rates of flux ropes and reconnection fronts in Mercury's plasma sheet are ~ 60 times higher than that of Earth's values, which we interpret to be due to the highly variable magnetospheric conditions at Mercury. Such higher occurrence rate of magnetic reconnection would generate more plasma flows in the dawnside plasma sheet than in the duskside. These plasma flows would mostly brake and initiate the substorm dipolarization on the postmidnight sector at Mercury rather than the

  20. Two-spacecraft observations of reconnection at the magnetopause: Model results and data comparison

    Science.gov (United States)

    Penz, T.; Farrugia, C. J.; Ivanova, V. V.; Semenov, V. S.; Biernat, H. K.; Torbert, R.

    We revisit an example of “quasi-steady” magnetic reconnection at the dayside magnetopause on February 11, 1998, observed by Equator-S and Geotail at the dawnside magnetopause. Phan et al. [Phan, T.D. et al., 2000. Extended magnetic reconnection at the Earth’s magnetopause from detection of bi-directional jets. Nature 404, 848 850.] reported oppositely directed jets at these spacecrafts and inferred a length of the reconnection line of about 38RE. Pinnock et al. [Pinnock, M., Chisham, G., Coleman, I.J., Freeman, M.P., Hairston, M., Villain, J.-P., 2003. The location and rate of dayside reconnection during an interval of southward interplanetary magnetic field. Ann. Geophys. 21, 1467 1482.] used measurements from SuperDARN radars to show that the reconnection electric field was variable. Here we complement this work by obtaining snapshots of the reconnection electric field from the in situ observations. To do this, we apply a reconstruction method based on a model of compressible Petschek-type magnetic reconnection. This independent method uses magnetic field observations as input data to calculate the reconnection electric field. We obtain average values of Erec in the range of 0.4 2.4 mV/m. Further we infer a distance perpendicular to the reconnection line of 0.4 0.6RE. The model results are compared with the two studies mentioned above. It thus appears that while the transfer of momentum for this event is indeed large-scale, the actual rate depends on the time it is measured.

  1. Investigation of the viscous reconnection phenomenon of two vortex tubes through spectral simulations

    Science.gov (United States)

    Beardsell, Guillaume; Dufresne, Louis; Dumas, Guy

    2016-09-01

    This paper aims to shed further light on the viscous reconnection phenomenon. To this end, we propose a robust and efficient method in order to quantify the degree of reconnection of two vortex tubes. This method is used to compare the evolutions of two simple initial vortex configurations: orthogonal and antiparallel. For the antiparallel configuration, the proposed method is compared with alternative estimators and it is found to improve accuracy since it can account properly for the formation of looping structures inside the domain. This observation being new, the physical mechanism for the formation of those looping structures is discussed. For the orthogonal configuration, we report results from simulations that were performed at a much higher vortex Reynolds number (ReΓ ≡ circulation/viscosity = 104) and finer resolution (N3 = 10243) than previously presented in the literature. The incompressible Navier-stokes equations are solved directly (Direct Numerical Simulation or DNS) using a Fourier pseudospectral algorithm with triply periodic boundary conditions. The associated zero-circulation constraint is circumvented by solving the governing equations in a proper rotating frame of reference. Using ideas similar to those behind our method to compute the degree of reconnection, we split the vorticity field into its reconnected and non-reconnected parts, which allows to create insightful visualizations of the evolving vortex topology. It also allows to detect regions in the vorticity field that are neither reconnected nor non-reconnected and thus must be associated to internal looping structures. Finally, the Reynolds number dependence of the reconnection time scale Trec is investigated in the range 500 ≤ ReΓ ≤ 10 000. For both initial configurations, the scaling is generally found to vary continuously as ReΓ is increased from T rec ˜ R eΓ - 1 to T rec ˜ R eΓ - 1 / 2 , thus providing quantitative support for previous claims that the reconnection

  2. A review of the monitored data of'adverse events following immunization'taking place in Yiwu city in 2012%义乌市2012年疑似预防接种异常反应监测情况分析

    Institute of Scientific and Technical Information of China (English)

    王轩; 楼灵巧; 楼挺

    2014-01-01

    目的:分析2012年义乌市疑似预防接种异常反应( Adverse Events Following Immunization,AEFI)的监测资料,评价AEFI监测系统运行状况,探讨监测中可能存在的问题。方法采用描述性流行病学方法分析2012年义乌市AEFI监测资料。结果2012年义乌市AEFI监测系统共报告病例54例,其中一般反应21例(38.89%),异常反应29例(53.70%),偶合症4例(7.41%)。 AEFI总报告发生率为6.59人次/10万剂;48 h报告及时率及调查率均为100%。病例报告数较多的是百白破疫苗(10例)和麻风疫苗(6例),而报告发生率较高的为乙脑(灭活)疫苗(124.44人次/10万剂)、流脑A+C结合疫苗(98.89人次/10万剂)及7价肺炎疫苗(40.05人次/10万剂)。结论2012年义乌市AEFI监测系统总体运转情况良好。但由于多种因素的影响,异常反应的报告比重大于一般反应,部分二类疫苗的报告发生率也较高,提示需强化人员监测意识,提高监测敏感性。%Objective To analyze the monitored data of ‘adverse events following immunization ( AEFI ) taking place in Yiwu city during 2012 so as to test the performance of the AEFI monitoring system and identify possible problem( s) therein. Method The monitored data of AEFI taking place in Yiwu during 2012 were collected with descriptive epidemiological method.Findings 54 AEFI cases were reported in Yiwu during 2012, including 21 cases with general vaccine reaction (38.89%), 29 cases with abnormal vaccine reaction (53.70%), and 4 cases with coincidental event (7.41%).The incidence rate of AEFI was 6.59 people/100000.The reported and investigated rates within 48h were 100%.The most reported vaccines were DPT vaccine (10 cases) and MR vaccine (6 cases), and the vaccines with the highest incidence reported were JE-i (124.44 people/100000), Men-AC conjugate vaccine(98.89 people/100000) and Pneumococcal 7-valent

  3. Electron scale nested quadrupole Hall field in Cluster observations of magnetic reconnection

    CERN Document Server

    Jain, Neeraj

    2014-01-01

    This Letter presents the first evidence of a new and unique feature of spontaneous reconnection at multiple sites in electron current sheet, viz. nested quadrupole structure of Hall field at electron scales, in Cluster observations. The new nested quadrupole is a consequence of electron scale processes in reconnection. Whistler response of the upstream plasma to the interaction of electron flows from neighboring reconnection sites produces a large scale quadrupole Hall field enclosing the quadrupole fields of the multiple sites, thus forming a nested structure. Electron-magnetohydrodynamic simulations of an electron current sheet yields mechanism of the formation of nested quadrupole.

  4. Spacecraft observations and analytic theory of crescent-shaped electron distributions in asymmetric magnetic reconnection

    CERN Document Server

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

    2016-01-01

    Supported by a kinetic simulation, we derive an exclusion energy parameter $\\cal{E}_X$ 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.

  5. Magnetotail Current Sheet Thinning and Magnetic Reconnection Dynamics in Global Modeling of Substorms

    Science.gov (United States)

    Kuznetsova, M. M.; Hesse, M.; Rastaetter, L.; Toth, G.; DeZeeuw, D. L.; Gombosi, T. I.

    2008-01-01

    Magnetotail current sheet thinning and magnetic reconnection are key elements of magnetospheric substorms. We utilized the global MHD model BATS-R-US with Adaptive Mesh Refinement developed at the University of Michigan to investigate the formation and dynamic evolution of the magnetotail thin current sheet. The BATSRUS adaptive grid structure allows resolving magnetotail regions with increased current density up to ion kinetic scales. We investigated dynamics of magnetotail current sheet thinning in response to southwards IMF turning. Gradual slow current sheet thinning during the early growth phase become exponentially fast during the last few minutes prior to nightside reconnection onset. The later stage of current sheet thinning is accompanied by earthward flows and rapid suppression of normal magnetic field component $B-z$. Current sheet thinning set the stage for near-earth magnetic reconnection. In collisionless magnetospheric plasma, the primary mechanism controlling the dissipation in the vicinity of the reconnection site is non-gyrotropic effects with spatial scales comparable with the particle Larmor radius. One of the major challenges in global MHD modeling of the magnetotail magnetic reconnection is to reproduce fast reconnection rates typically observed in smallscale kinetic simulations. Bursts of fast reconnection cause fast magnetic field reconfiguration typical for magnetospheric substorms. To incorporate nongyritropic effects in diffusion regions we developed an algorithm to search for magnetotail reconnection sites, specifically where the magnetic field components perpendicular to the local current direction approaches zero and form an X-type configuration. Spatial scales of the diffusion region and magnitude of the reconnection electric field are calculated self-consistently using MHD plasma and field parameters in the vicinity of the reconnection site. The location of the reconnection sites and spatial scales of the diffusion region are updated

  6. Plasma wave signatures in the magnetotail reconnection region - MHD simulation and ray tracing

    Science.gov (United States)

    Omura, Yoshiharu; Green, James L.

    1993-01-01

    An MHD simulation was performed to obtain a self-consistent model of magnetic field and plasma density near the X point reconnection region. The MHD model was used to perform extensive ray tracing calculations in order to clarify the propagation characteristics of the plasma waves near the X point reconnection region. The dynamic wave spectra possibly observed by the Geotail spacecraft during a typical cross-tail trajectory are reconstructed. By comparing the extensive ray tracing calculations with the plasma wave data from Geotail, it is possible to perform a kind of 'remote sensing' to identify the location and structure of potential X point reconnection regions.

  7. Recent studies in satellite observations of three-dimensional magnetic reconnection

    Institute of Scientific and Technical Information of China (English)

    XIAO ChiJie; WANG XiaoGang; PU ZuYin; MA ZhiWei; ZHAO Hui; ZHOU GuiPing; WANG JingXiu; LIU ZhenXing

    2007-01-01

    Magnetic reconnection is a main process converting the magnetic energy into thermal and kinetic energy in plasmas. It is one of the fundamental problems of crucial importance not only to space plasmas physics and space weather studies,such as the solar flare, coronal mass ejections and magnetospheric substorms, but also to the stability analysis in magnetically confined fusion. In general, except for cases with periodical boundary conditions, three-dimensional (3D) magnetic reconnection occurs on magnetic separatrices generated by magnetic nulls. Here we briefly introduce/review the theories and some recent satellite observations of 3D magnetic reconnection. Topics to be further studied are also discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zank, G. P.; Le Roux, J. A.; Webb, G. M.; Dosch, A. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Khabarova, O. [Heliophysical Laboratory, Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation RAS (IZMIRAN), Troitsk, Moscow 142190 (Russian Federation)

    2014-12-10

    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{sub A} )/2, where M{sub A} is the Alfvén Mach number. Considering only magnetic island contraction yields power-law-like solutions with index –3(1 + τ {sub c}/(8τ{sub diff})), where τ {sub c}/τ{sub 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{sub diff}/τ {sub 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 {sup –5} (c particle

  9. A magnetic reconnection mechanism for the generation of anomalous cosmic rays

    Science.gov (United States)

    Drake, James; Opher, Merav; Swisdak, Marc; Chamoun, Jacob

    The recent observations of the anomalous cosmic ray (ACR) energy spectrum as Voyagers 1 and 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 the current layers break up into a turbulent bath of magnetic islands that merge to release a large fraction of the energy in the sectored magnetic field. Most of the magnetic energy goes into energetic ions with significant but smaller amounts of energy going into electrons. The dominant acceleration mechanism is through reflection in contracting islands, a first-order Fermi mechanism. Particle energy gain is regulated by the approach to the marginal firehose condition. The ACR differ-ential energy spectrum for all of the ion species takes the form of a power law with a spectral index slightly above 1.5, which is consistent with observations.

  10. Parks, People and Places

    DEFF Research Database (Denmark)

    Molin, Julie Frøik

    This thesis suggests, by applying a ‘place’ perspective, that involving users in operational management of green spaces holds potentials for enhancing ‘place attachment’ of urban inhabitants. As this can also build their commitment to decision making on their local living environment, green space...... approach to green space maintenance. To guide the exploration a theoretical framework was developed inductively, structured around concepts of environmental governance in combination with strategic approaches to green space management. The framework is operationalised by analyses of the governance...... dimensions ‘actors’, ‘resources’ and ‘rules’. Moreover, the impacts of place-based governance processes on green space quality are examined via a review of previous scientific articles. The thesis concludes that place-based governance offers potential for bringing users and managers closer together, through...

  11. Context in place

    DEFF Research Database (Denmark)

    Nordentoft, Helle Merete; Thomsen, Rie

    The purpose of this paper is to provide a theoretical framework - i.e. a vocabulary - for understanding the importance of integrating context in analyses of guidance practices. The paper delineates a conceptual landscape of context based on social practice and interactional theories on context. We...... studies on interdisciplinary clinical supervision and work place guidance in which there appears to be a mismatch between intended outcomes and actual events. The analyses demonstrate and support that 'the place' seems - to influence partipants' responses in the guidance sessions and, therefore, must be...... specifically argue for a more grounded approach to the conception of context - a topographic approach - in which the physical setting - i.e. 'the place' becomes an inevitable part of analyses of guidance practices in order to understand participants' sense-making processes. In the paper we draw on two case...

  12. Space vs. Place

    DEFF Research Database (Denmark)

    Zimmerman, Chris; Madsen, Rene; Hammer Eliassen, Henrik;

    2016-01-01

    of these spaces and events as place-based experiences. In doing so, these two layers of space-based movements and place-based experiences reveal the appropriation of affordances and choices of aesthetic appreciation by the crowd at large of what is subjectively and relatively meaningful, actionable, and valuable....... of Importance’. Second, we elaborate on methods deployed for collecting both mobile GPS and social media traces that the smart phone generates in physical spaces. Third, we compare and contrast the automatically geocoded presence in space and at events with the intentionally socially tagged consumption...

  13. Ageing in Communal Place

    DEFF Research Database (Denmark)

    Aarhus, Rikke; Ballegaard, Stinne Aaløkke; Grönvall, Erik;

    2009-01-01

    In this paper we adopt the position that design of social media for the elderly and virtual senior communities may be informed by studying ‘real’ senior communities. Since current research efforts target the role of social media and virtual communities for supporting seniors ageing in place, i...... these findings apply to designers of social media technologies. .......e. in their homes, housing communities seem a natural place to begin this enquiry. We conducted observations and informal interviews in six different senior dwellings. In this paper we present the key findings from these visits related to social interaction and the formation of communities and explicate how...

  14. Ageing in communal place

    DEFF Research Database (Denmark)

    Aarhus, Rikke; Ballegaard, Stinne Aaløkke; Grönvall, Erik;

    2009-01-01

    In this paper we adopt the position that design of social media for the elderly and virtual senior communities may be informed by studying `real´senior communities. Since current research efforts target the role of social media and virtual communities for supporting seniors ageing in place, i...... these findings apply to designers of social media technologies........e. in their homes, housing communities seems a natural place to begin this enquiry. We conducted observations and informal interviews in six different senior dwellings. In this paper we present the key findings from these visits related to social interaction and the formation of communities and explicate how...

  15. Stress at Work Place

    OpenAIRE

    Mohammad A. Shahrour

    2010-01-01

    One of hardest forms of stresses to avoid is that work place or job stress Job stress refers to stress experienced by an individual at or because of issues at their work place The term work related stress has many meanings and it causes different levels of anxiety. Not all challenges at work can be called stress as some of these challenges drive employees upward, and empower them to learn new skills or push them to work harder to achieve a certain goal. So, this type of challenges cannot be c...

  16. Take Caution When Bats Are Near

    Science.gov (United States)

    ... in humans have so far been limited to Malaysia, Singapore, India, and Bangladesh. Both viruses can cause ... outdoor activities take place, such as hiking or camping. While there have been instances of humans exposed ...

  17. Electromagnetic Armor Based on the Principles of Reconnection Electromagnetic Launcher

    Institute of Scientific and Technical Information of China (English)

    Yu Haiqing; Li Weitao; Gao Haizhen

    2015-01-01

    Active electromagnetic armor is the latest concept of defense system, and it is highly probable for this technology to be applied to many domains such as future tanks, armored vehicles and the armor of warships. The studies on active electromagnetic defense technology in the world have a history of decades. But, there still exist bottlenecks and the interceptor is one of them. This paper studies the problem of interceptors based on the principles of reconnection electromagnetic launcher and presents a kind of simulation model of it. A small scale laboratory model is made, and related experimental researches and theoretical analyses have been carried out when the projectiles are different kinds of material and shape. Satisfactory results are reached and agree with the theoretical analyses.

  18. Spatial Distribution of Energetic Electrons during Magnetic Reconnection

    Institute of Scientific and Technical Information of China (English)

    WANG Aong-Sheng; LU Quan-Ming; GUO Jun; WANG Shui

    2008-01-01

    @@ Electron acceleration by the inductive electric field near the X point in magnetic reconnection is an important generation mechanism for energetic electrons. Particle simulations have revealed that most of energetic electrons reside in the magnetic field line pileup region, and a depletion of energetic electrons can be found near the centre of the diffusion region [Phys. Plasmas, 13 (2006) 012309]. We report direct measurement of energetic electron in and around the ion diffusion region in near-Earth tail by the cluster, and our observations confirm the above predictions: a depletion of the high-energy electron fluxes is detected near the centre of the diffusion region. At the same time, the plasma temperature has a similar profile in the diffusion region.

  19. Bifurcation analysis of magnetic reconnection in Hall-MHD-systems

    Science.gov (United States)

    Homann, Holger; Grauer, Rainer

    2005-08-01

    The influence of the Hall-term on the width of the magnetic islands of the tearing-mode is examined. We applied the center manifold (CMF) theory to a magnetohydrodynamic (MHD)-system. The MHD-system was chosen to be incompressible and includes in addition to viscosity the Hall-term in Ohm’s law. For certain values of physical parameters the corresponding center manifold is two-dimensional and therefore the original partial differential equations could be reduced to a two-dimensional system of ordinary ones. This amplitude equations exhibit a pitchfork-bifurcation which corresponds to the occurrence of the tearing-mode. Eigenvalue-problems and linear equations due to the center manifold reduction were solved numerically with the Arpack++-library. An important result of this analysis is the growth of the tearing mode island width by increasing the Hall-parameter, a feature which has been observed in recent numerical simulations of collisionless reconnection.

  20. Fast reconnection in relativistic plasmas: the magnetohydrodynamics tearing instability revisited

    Science.gov (United States)

    Del Zanna, L.; Papini, E.; Landi, S.; Bugli, M.; Bucciantini, N.

    2016-08-01

    Fast reconnection operating in magnetically dominated plasmas is often invoked in models for magnetar giant flares, for magnetic dissipation in pulsar winds, or to explain the gamma-ray flares observed in the Crab nebula; hence, its investigation is of paramount importance in high-energy astrophysics. Here we study, by means of two-dimensional numerical simulations, the linear phase and the subsequent non-linear evolution of the tearing instability within the framework of relativistic resistive magnetohydrodynamics (MHD), as appropriate in situations where the Alfvén velocity approaches the speed of light. It is found that the linear phase of the instability closely matches the analysis in classical MHD, where the growth rate scales with the Lundquist number S as S-1/2, with the only exception of an enhanced inertial term due to the thermal and magnetic energy contributions. In addition, when thin current sheets of inverse aspect ratio scaling as S-1/3 are considered, the so-called ideal tearing regime is retrieved, with modes growing independently of S and extremely fast, on only a few light crossing times of the sheet length. The overall growth of fluctuations is seen to solely depend on the value of the background Alfvén velocity. In the fully non-linear stage, we observe an inverse cascade towards the fundamental mode, with Petschek-type supersonic jets propagating at the external Alfvén speed from the X-point, and a fast reconnection rate at the predicted value {R}˜ (ln S)^{-1}.