WorldWideScience

Sample records for reconnection takes place

  1. Reconnection Diffusion, Star Formation and Numerical Simulations

    OpenAIRE

    Lazarian, A.

    2013-01-01

    We consider fast magnetic reconnection that takes place within turbulent magnetic flux and show that the process results in diffusion of magnetic fields and matter, which we term reconnection diffusion. The process of reconnection diffusion is based on the model of 3D reconnection of weakly turbulent magnetic fields and is applicable to both fully ionized and partially ionized gas. The rate of reconnection diffusion does not depend on the level of ionization and therefore th...

  2. Magnetic field reconnection. Chapter 3.1.2

    International Nuclear Information System (INIS)

    A review of present knowledge regarding magnetic field reconnection is presented. Although it is of considerable importance in astrophysics, reconnection is still poorly undertstood due to the nonlinear magnetohydrodynamic processes taking place. (W.D.L.)

  3. 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...

  4. 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.

  5. Book review: Cyber war will not take place

    OpenAIRE

    Muravska, Julia

    2013-01-01

    "Cyber War Will Not Take Place." Thomas Rid. Hurst. April 2013. --- In 2005, the U.S. Air Force boasted it would now fly, fight, and win in cyberspace, the ‘fifth domain’ of warfare. This book takes stock to consider whether or not cyber war is a real threat. Thomas Rid argues that the focus on war and winning distracts from the real challenge of cyberspace: non-violent confrontation that may rival or even replace violence in surprising ways. Tracing the most significant hacks and attacks...

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

    OpenAIRE

    Mara Alagic; RIMMINGTON, GLYN M.; Tatiana Orel

    2009-01-01

    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 f...

  7. Magnetic Reconnection under Anisotropic MHD Approximation

    CERN Document Server

    Hirabayashi, K

    2013-01-01

    We study the formation of slow-mode shocks in collisionless magnetic reconnection by using one- and two-dimensional collisionless MHD codes based on the double adiabatic approximation and the Landau closure model. We 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. Our results showed that once magnetic reconnection takes place, a firehose-sense pressure anisotropy arises in the downstream region, and the generated slow shocks are quite weak comparing with those in an isotropic MHD. In spite of the weakness of the shocks, however, the resultant reconnection rate is 10-30% higher than that in an isotropic case. This 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.

  8. 49 CFR 40.221 - Where does an alcohol test take place?

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false Where does an alcohol test take place? 40.221... Testing § 40.221 Where does an alcohol test take place? (a) A DOT alcohol test must take place at an... suitable clean surface for writing. (e) If an alcohol testing site fully meeting all the visual and...

  9. 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...

  10. MAGNETIC RECONNECTION BETWEEN SMALL-SCALE LOOPS OBSERVED WITH THE NEW VACUUM SOLAR TELESCOPE

    International Nuclear Information System (INIS)

    Using the high tempo-spatial resolution H? images observed with the New Vacuum Solar Telescope, we report solid observational evidence of magnetic reconnection between two sets of small-scale, anti-parallel loops with an X-shaped topology. The reconnection process contains two steps: a slow step with a duration of more than several tens of minutes, and a rapid step lasting for only about three minutes. During the slow reconnection, two sets of anti-parallel loops gradually reconnect, and new loops are formed and stacked together. During the rapid reconnection, the anti-parallel loops approach each other quickly, and then rapid reconnection takes place, resulting in the disappearance of the former loops. In the meantime, new loops are formed and separate. The region between the approaching loops is brightened, and the thickness and length of this region are determined to be about 420 km and 1.4 Mm, respectively. During the rapid reconnection process, obvious brightenings at the reconnection site and apparent material ejections outward along reconnected loops are observed. These observed signatures are consistent with predictions by reconnection models. We suggest that the successive slow reconnection changes the conditions around the reconnection site and triggers instabilities, thus leading to the rapid approach of the anti-parallel loops and resulting in the rapid reconnection

  11. MAGNETIC RECONNECTION BETWEEN SMALL-SCALE LOOPS OBSERVED WITH THE NEW VACUUM SOLAR TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shuhong; Zhang, Jun [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Xiang, Yongyuan, E-mail: shuhongyang@nao.cas.cn [Fuxian Solar Observatory, Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China)

    2015-01-01

    Using the high tempo-spatial resolution H? images observed with the New Vacuum Solar Telescope, we report solid observational evidence of magnetic reconnection between two sets of small-scale, anti-parallel loops with an X-shaped topology. The reconnection process contains two steps: a slow step with a duration of more than several tens of minutes, and a rapid step lasting for only about three minutes. During the slow reconnection, two sets of anti-parallel loops gradually reconnect, and new loops are formed and stacked together. During the rapid reconnection, the anti-parallel loops approach each other quickly, and then rapid reconnection takes place, resulting in the disappearance of the former loops. In the meantime, new loops are formed and separate. The region between the approaching loops is brightened, and the thickness and length of this region are determined to be about 420 km and 1.4 Mm, respectively. During the rapid reconnection process, obvious brightenings at the reconnection site and apparent material ejections outward along reconnected loops are observed. These observed signatures are consistent with predictions by reconnection models. We suggest that the successive slow reconnection changes the conditions around the reconnection site and triggers instabilities, thus leading to the rapid approach of the anti-parallel loops and resulting in the rapid reconnection.

  12. 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 ...

  13. Social Reconnection Revisited: The Effects of Social Exclusion Risk on Reciprocity, Trust, and General Risk-Taking

    Science.gov (United States)

    Derfler-Rozin, Rellie; Pillutla, Madan; Thau, Stefan

    2010-01-01

    We hypothesize that people at risk of exclusion from groups will engage in actions that can socially reconnect them with others and test the hypothesis in four studies. We show that participants at risk of exclusion reciprocated the behavior of an unknown person (Study 1a) and a potential excluder (Study 1b) more compared to two control groups…

  14. 4th openlab Board of Sponsors Meeting takes place at CERN on July 6, 2005

    CERN Multimedia

    Patrice Loïez

    2005-01-01

    The 4th openlab Board of Sponsors Meeting is taking place at CERN, room 513, 1-024, the 6th July 2005. The meeting will open with an Executive Session in the presence of Dr. Robert Aymar, Director General of CERN

  15. Reconnection of magnetic field lines by clouds-in-cells plasma model

    International Nuclear Information System (INIS)

    A plasma computer experiment by the clouds-in-cells method is presented for the study of the evolutionary process of the reconnection of magnetic field lines, where initially there is a plane current sheet, i.e. antiparallel magnetic field lines. A plasma flow from outside toward the magnetic neutral sheet will cause the reconnection. The model is two-dimensional and positive and negative charges have the same mass. It is shown that rapid reconnection can easily take place, though the solution is obtained only for the vicinity of the resulting magnetic neutral point. The diffusion rate of the magnetic field at the neutral point is self-adjustable to a given reconnection rate, so that the reconnection rate can take any value up to the local Alfven velocity immediately outisde the field reversal region. (auth.)

  16. Particle simulation study of driven magnetic reconnection in a collisionless plasma

    International Nuclear Information System (INIS)

    Driven magnetic reconnection in a collisionless plasma, 'collisionless driven reconnection', is investigated by means of a 2.5 dimensional particle simulation. Magnetic reconnection develops in two steps, i.e., slow reconnection which takes place in the early stage of the compression when the current layer is compressed as thin as the orbit amplitude of an ion meandering motion (ion current layer), and subsequent fast reconnection which takes place in the late stage when the electron current is concentrated into the narrow region with spatial scale comparable to the orbit amplitude of an electron meandering motion (electron current layer). The global dynamic evolution of magnetic reconnection is controlled by the physics of the ion current layer. The maximum reconnection rate is roughly in proportion to the driving electric field. It is also found that both ion heating and electron heating take place in accordance with the formation of two current layers and the ion temperature becomes two or more times as high as the electron temperature. (author)

  17. On the processes taking place during the inculation period of pearlite and bainite transformations of austenite

    International Nuclear Information System (INIS)

    Investigated are incubation period of pearlite and bainite transformations of austenite of nickel-chromium steel (0.45% C; 2% Cr; 4% Ni; 0.3% Mo). The acoustic method is used. On the base of resonance frequencies measurements at different temperatures of isothermal hold-up evaluated is the activation energy of processes preceding correspondingly pearlite and bainite transformations. It is concluded according to the obtained results, that frequency change during isothermal hold-up takes place in two stages

  18. ERCP in acute pancreatitis: What takes place in routine clinical practice?

    OpenAIRE

    Armando Gabbrielli; Raffaele Pezzilli; Generoso Uomo; Alessandro Zerbi; Luca Frulloni; Paolo De Rai; Laura Castoldi; Guido Costamagna; Claudio Bassi; Valerio Di Carlo

    2010-01-01

    AIM: To evaluate the data from a survey carried out in Italy regarding the endoscopic approach to acute pancreatitis in order to obtain a picture of what takes place after the release of an educational project on acute pancreatitis sponsored by the Italian Association for the Study of the Pancreas.METHODS: Of the 1 173 patients enrolled in our survey, the most frequent etiological category was biliary forms (69.3%) and most patients had mild pancreatitis (85.8%).RESULTS: 344/1 173 (29.3%) und...

  19. 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 discussed regarding categories in clothing collections, fashion marketing and the way the sportswear features are reflected to the trends.

  20. Self-organized Te Redistribution during Driven Reconnection Processes in High Temperature Plasmas

    International Nuclear Information System (INIS)

    Two-dimensional (2-D) images of electron temperature fluctuations with a high temporal and spatial resolution were employed to study the sawtooth oscillation in TEXTOR tokamak plasmas. The new findings are: (1) 2-D images revealed that the reconnection is localized and permitted the determination of the physical dimensions of the reconnection zone in the poloidal and toroidal planes. (2) The combination of a pressure driven mode and a kink instability leads to an 'X-point' reconnection process. (3) Reconnection can take place anywhere along the q?1 rational magnetic surface (both high and low field sides). (4) Heat flow from the core to the outside of the inversion radius during the reconnection time is highly asymmetric and the behavior is collective. These new findings are compared with the characteristics of various theoretical models and experimental results for the study of the sawtooth oscillation in tokamak plasmas

  1. 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.

  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. Fast reconnection of magnetic fields in a plasma

    International Nuclear Information System (INIS)

    The reconnection process of magnetic fields in a plasma is analytically studied by perturbing the boundary conditions on a slab of incompressible plasma with a resonant surface inside. It is found, for small resistivity, that the reconnection takes place on an Alfven time scale and continues into a slow time scale t1 = eta/sup 1/3/t. Both time scales are faster than the usual tearing time scale. Furthermore, the plasma evolves globally from its initial equilibrium on the slow time scale and settles down to a different final equilibrium

  4. 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.

  5. DSC studies of retrogradation and amylose lipid complex transition taking place in gamma irradiated wheat starch

    Science.gov (United States)

    Cie?la, K.; Eliasson, A. C.

    2007-12-01

    The effect of gamma irradiation ( 60Co) with doses of 5-30 kGy on the amylose-lipid complex transition and retrogradation occurring in gels containing ca. 50% and ca. 20% wheat starch was studied by differential scanning calorimetry (DSC) during heating-cooling-heating cycles (up to three cycles). Transition of the amylose-lipid complex occurs in all the irradiated samples at a lower temperature as compared to the non-irradiated starch. That effect was larger when the radiation dose was higher. A further thermal treatment causes a decrease of the transition temperature in the irradiated samples, with no effect or increase of that temperature observed for the non-irradiated ones. Irradiation hinders retrogradation taking place in 50% gels but facilitates the process occurring in 20% gels. The differences between the irradiated and the non-irradiated samples are more evident in the every next heating or cooling cycle as well as after storage and in the case of ca. 50% suspensions as compared to ca. 20% suspensions. The results point out to the deterioration of the structure of the complexes formed in the irradiated starch as compared to the non-irradiated one.

  6. 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 ...

  7. OECD Global Science Forum's Astronomy Workshop to take place in Munich

    Science.gov (United States)

    2003-11-01

    On December 1 to 3, the city of Munich (Bavaria, Germany) will be the venue for a "Workshop on Large Scale Programmes and Projects in Astronomy and Astrophysics" organised by the Organisation for Economic Co-operation and Development (OECD) Global Science Forum in co-operation with the European Southern Observatory (ESO). The Workshop will be chaired by Ian Corbett (ESO). The Global Science Forum brings together science policy officials from the OECD countries. The delegates, who meet twice a year, look at a range of generic issues in science funding and seek to identify and maximise opportunities for international co-operation in basic scientific research. This Workshop was proposed by Germany and agreed by the delegates to the Global Science Forum in June. Government officials and scientists will be able to review in detail the information and the observational and technological advances needed for major progress in the field during the next 15- 20 years. The research subjects reviewed will cover the full range from planets, solar systems, life in the Universe, stars, galaxies, extreme objects to cosmology. Related technological challenges, virtual observatories and other data handling issues will also be considered. The primary objective is to specify the policy issues relating to priority-setting, planning, funding and, above all, international co-ordination and co-operation. The Workshop will focus on issues relevant to the process through which astronomy advances, and will highlight means to enhance that process in light of longer-term scientific and political trends. There will probably be a follow-up meeting early in 2004, from which a policy level report will be prepared for consideration by the Global Science Forum and so transmitted to governments. Eighteen delegations, from non-OECD as well as OECD countries, will attend, each consisting of senior programme managers from the national ministry, funding agency or research council, and one or more senior members of the national astronomical community. The International Astronomical Union (IAU) and the European Southern Observatory (ESO) are explicitly represented. Experts from the world-wide astronomy community have been invited to set the stage and provide input for the discussions. The choice by Germany and the OECD to make Munich the venue of this Global Science Forum Workshop is no coincidence. It is a recognition of the important role played by many institutions in the Munich region in the field of Astronomy and Astrophysics. They include the Ludwig-Maximilians-Universität where the Workshop will take place, the Max-Planck-Institut für Astrophysik, the Max-Planck Institut für Extraterrestrische Physik and the European Southern Observatory. These institutions are all participating in large programmes and projects in astronomy. ESO, for its part, is at the leading edge of world astronomy with its flagship facility, the Very Large Telescope in Paranal (Chile) and the newly started ALMA project at Chajnantor (Chile), being carried out in partnership between Europe and North America. Public Talks (Munich) on December 1, 2003 As a prelude to the Workshop, two public keynote presentations will take place on December 1 at the Deutsches Museum in Munich at 18:00 CET. The speakers are Malcolm Longair, Jacksonian Professor of Natural Philosophy and Head of Laboratory, Cavendish Laboratory, Cambridge (UK) and Martin Harwit, Professor Emeritus of Astronomy, Cornell University, and former Director of the National Air and Space Museum, Washington, DC (USA). The talks will be given in English and the entry to this public event is free. Professor Longair will speak on "Astrophysics and Cosmology in the Twenty-First Century" and Professor Harwit will speak on "The Growth of Understanding of our Universe". You can find more informaton on the Public Talks web page.

  8. ERCP in acute pancreatitis: What takes place in routine clinical practice?

    Directory of Open Access Journals (Sweden)

    Armando Gabbrielli

    2010-09-01

    Full Text Available AIM: To evaluate the data from a survey carried out in Italy regarding the endoscopic approach to acute pancreatitis in order to obtain a picture of what takes place after the release of an educational project on acute pancreatitis sponsored by the Italian Association for the Study of the Pancreas.METHODS: Of the 1 173 patients enrolled in our survey, the most frequent etiological category was biliary forms (69.3% and most patients had mild pancreatitis (85.8%.RESULTS: 344/1 173 (29.3% underwent endoscopic retrograde cholangiopancreatography (ERCP. The mean interval between the onset of symptoms and ERCP was 6.7 ± 5.0 d; only 89 examinations (25.9% were performed within 72 h from the onset of symptoms. The main indications for ERCP were suspicion of common bile duct stones (90.3%, jaundice (44.5%, clinical worsening of acute pancreatitis (14.2% and cholangitis (6.1%. Biliary and pancreatic ducts were visualized in 305 patients (88.7% and in 93 patients (27.0% respectively. The success rate in obtaining a cholangiogram was statistically higher (P = 0.003 in patients with mild acute pancreatitis (90.6% than in patients with severe disease (72.2%. Biliary endoscopic sphincterotomy was performed in 295 of the 305 patients (96.7% with no difference between mild and severe disease (P = 0.985. ERCP morbidity was 6.1% and mortality was 1.7%; the mortality was due to the complications of acute pancreatitis and not the endoscopic procedure.CONCLUSION: The results of this survey, as with those carried out in other countries, indicate a lack of compliance with the guidelines for the indications for interventional endoscopy.

  9. ERCP in acute pancreatitis: What takes place in routine clinical practice?

    Science.gov (United States)

    Gabbrielli, Armando; Pezzilli, Raffaele; Uomo, Generoso; Zerbi, Alessandro; Frulloni, Luca; Rai, Paolo De; Castoldi, Laura; Costamagna, Guido; Bassi, Claudio; Carlo, Valerio Di

    2010-01-01

    AIM: To evaluate the data from a survey carried out in Italy regarding the endoscopic approach to acute pancreatitis in order to obtain a picture of what takes place after the release of an educational project on acute pancreatitis sponsored by the Italian Association for the Study of the Pancreas. METHODS: Of the 1 173 patients enrolled in our survey, the most frequent etiological category was biliary forms (69.3%) and most patients had mild pancreatitis (85.8%). RESULTS: 344/1 173 (29.3%) underwent endoscopic retrograde cholangiopancreatography (ERCP). The mean interval between the onset of symptoms and ERCP was 6.7 ± 5.0 d; only 89 examinations (25.9%) were performed within 72 h from the onset of symptoms. The main indications for ERCP were suspicion of common bile duct stones (90.3%), jaundice (44.5%), clinical worsening of acute pancreatitis (14.2%) and cholangitis (6.1%). Biliary and pancreatic ducts were visualized in 305 patients (88.7%) and in 93 patients (27.0%) respectively. The success rate in obtaining a cholangiogram was statistically higher (P = 0.003) in patients with mild acute pancreatitis (90.6%) than in patients with severe disease (72.2%). Biliary endoscopic sphincterotomy was performed in 295 of the 305 patients (96.7%) with no difference between mild and severe disease (P = 0.985). ERCP morbidity was 6.1% and mortality was 1.7%; the mortality was due to the complications of acute pancreatitis and not the endoscopic procedure. CONCLUSION: The results of this survey, as with those carried out in other countries, indicate a lack of compliance with the guidelines for the indications for interventional endoscopy. PMID:21160762

  10. Magnetic reconnection

    International Nuclear Information System (INIS)

    A review is given of the theory of magnetic reconnection in the framework of resistive magnetohydrodynamics (MHD). While most of the material refers to two-dimensional systems, the final sections give a brief outlook of problems arising in fully three-dimensional configurations. (orig.)

  11. 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.

  12. DSC studies of retrogradation and amylose-lipid transition taking place in gamma-irradiated wheat starch

    International Nuclear Information System (INIS)

    It has been already shown that degradation resulting from gamma irradiation induces a decrease in order of starch granules and influences gelatinisation taking place during heating of starch and flour suspensions. In presented paper, DSC (differential scanning calorimetry) studies were carried out for wheat starch, non-irradiated and irradiated using doses in the range from 5 to 30 kGy. The influence of the conditions applied during DSC measurements on the possibility to observe differences between the amylose-lipid complex transition and retrogradation taking place in the non-irradiated and particularly irradiated starch samples was checked. The better differentiation between the amylose-lipid complex transition taking place in particular samples accompanied by the better reproducity were obtained in the case of dense suspensions as compared to the watery suspensions as well as during the first analysis performed for the recrystallised gels

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

    DEFF Research Database (Denmark)

    Knudsen, Bo Nissen

    Danish place-names have been under publication since 1922 in the scientific series Danmarks Stednavne (Place-Names of Denmark) but only recently the huge project of a digitization of the series has been undertaken. Around 120,000 name articles are now on their way to the web as part of the Digital...... atlas of the Danish historical-administrative geography. Digitization and presentation of a scientific place-names edition poses many interesting problems in itself, especially regarding the variation over time in both the selection of names and the build-up of scholarly knowledge. How are we to convey...... physical 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...

  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. The structure of the magnetic reconnection exhaust boundary

    Science.gov (United States)

    Liu, Yi-Hsin

    2012-10-01

    Switch-off slow shocks (SSS) are the key structure of driving the outflow in Petschek's reconnection model. Observations of reconnection in the solar wind in particular seem to suggest that reconnection X-lines and associated exhausts grow to very large scales and resemble the open outflow geometry predicted by Petschek. However, direct observations of SSSs in the Earth's magnetosphere and the solar wind are infrequent. Since it is the release of magnetic energy downstream from the X-line that ultimately drives the outflow rather than the dynamics close to the X-line, the absence of the SSS in observations and kinetic simulations calls into question the conjecture that fast collisionless reconnection actually can scale to very large systems. Thus, a key requirement for demonstrating the fast energy release of reconnection that takes place in large systems is to pin down the specific mechanism driving the Alfvenic outflow. We present a large 2-D reconnection simulation and its companion Riemann problem using a Particle-In-Cell code. The self-generated firehose-sense temperature anisotropy (i.e., T| > T) by counterstreaming ions is found to be important in determining the structure of reconnection exhausts. This temperature anisotropy slows down the intermediate mode while speeds up the slow mode, and consequently prevents the formation of classical Switch-off Slow shocks in Petschek's model. Instead, the nonlinear coupling between the slow and intermediate waves constitutes the shock transition. A plateau of the firehose stability parameter 1-(?|-?)/2 at value 0.25 is observed inside these hybrid waves, which should also be observable in Earth's magnetotail and the solar wind. This special value is significant because it is the degeneracy point of slow and intermediate waves in anisotropic plasmas. The anisotropic Rankine-Hugoniot jump conditions are derived and compared with our simulations, while the pseudo-potentials of shocks are analyzed to explain the dynamics of forming these transition structures. The Wal'en relation is shown to fail at the core of reconnection exhausts, where the firehose instability is unstable. (Ref: Yi-Hsin Liu, J. F. Drake and M. Swisdak, The structure of the magnetic reconnection exhaust boundary, Phys. of Plasmas, 19, 022110, 2012)

  16. "Put Myself Into Your Place": Embodied Simulation and Perspective Taking in Autism Spectrum Disorders.

    Science.gov (United States)

    Conson, Massimiliano; Mazzarella, Elisabetta; Esposito, Dalila; Grossi, Dario; Marino, Nicoletta; Massagli, Angelo; Frolli, Alessandro

    2015-08-01

    Embodied cognition theories hold that cognitive processes are grounded in bodily states. Embodied processes in autism spectrum disorders (ASD) have classically been investigated in studies on imitation. Several observations suggested that unlike typical individuals who are able of copying the model's actions from the model's position, individuals with ASD tend to reenact the model's actions from their own egocentric perspective. Here, we performed two behavioral experiments to directly test the ability of ASD individuals to adopt another person's point of view. In Experiment 1, participants had to explicitly judge the left/right location of a target object in a scene from their own or the actor's point of view (visual perspective taking task). In Experiment 2, participants had to perform left/right judgments on front-facing or back-facing human body images (own body transformation task). Both tasks can be solved by mentally simulating one's own body motion to imagine oneself transforming into the position of another person (embodied simulation strategy), or by resorting to visual/spatial processes, such as mental object rotation (nonembodied strategy). Results of both experiments showed that individual with ASD solved the tasks mainly relying on a nonembodied strategy, whereas typical controls adopted an embodied strategy. Moreover, in the visual perspective taking task ASD participants had more difficulties than controls in inhibiting other-perspective when directed to keep one's own point of view. These findings suggested that, in social cognitive tasks, individuals with ASD do not resort to embodied simulation and have difficulties in cognitive control over self- and other-perspective. PMID:25663550

  17. New Private Infrastructure Projects in Developing Countries Continue to Take Place But Projects are Being Affected by the Financial Crisis

    OpenAIRE

    Izaguirre, Ada Karina

    2009-01-01

    Throughout the financial crisis, new private activity has continued to take place in developing countries with projects being tendered and brought to financial closure. In the first months of the full-scale of the financial crisis (Aug-Nov 2008), the rate of project closure was 26 percent lower than in the same period in 2007. However, since then private activity recovered and the project ...

  18. Low-Beta MHD Reconnection As a Showcase of Compressible Fluid Dynamics

    Science.gov (United States)

    Zenitani, S.

    2014-12-01

    In the solar corona, in the magnetosphere, and in other astrophysical settings, magnetic reconnection often occurs in a low-beta plasma. Unfortunately, less is known about low-beta reconnection, partially due to lack of attention and partially due to numerical difficulties. Recent MHD simulations revealed several new features of low-beta reconnection; For example, Zenitani et al.(2010,2011) [1,2] discovered a normal shock which is perpendicular to the Petschek shock and a repeated shock-reflection in front of a magnetic island. In this contribution, we extend earlier works with improved MHD codes and organize the results from the perspective of compressible fluid dynamics. In fluid dynamics, once a flow speed becomes comparable with the local sound speed, various compressible effects take place. This is the case for low-beta reconnection, because an Alfvenic reconnection jet becomes supersonic. Many phenomena can be understood as compressible fluid effects: the normal shock is equivalent to a recompression shock on a transonic airfoil, the shock-reflection corresponds to shock-diamonds in an over-expanded supersonic flow, the adiabatic acceleration similarly takes place as the Laval nozzle, and so on. They appear regardless of Sweet-Parker, plasmoid-mediated, or Petschek reconnections. We further discover another shock-diamonds in extreme cases. A critical condition for these hidden shocks is derived. All these issues can be applied to more extreme cases of relativistic reconnection, in which the sound speed is ``relatively'' slow. We will also address the relevance to the physics of extragalactic jets. References:[1] Zenitani, Hesse, & Klimas, ApJ, 716, L214 (2010).[2] Zenitani and Miyoshi, Phys. Plasmas, 18, 022105 (2011).

  19. Modelling Magnetic Reconnection and Nano-flare Heating in the Solar Corona

    Science.gov (United States)

    Biggs, George; Asgari-Targhi, Mahboubeh

    2015-01-01

    Current models describing magnetic reconnection in the solar corona assume single reconnection events occurring at random crossings between magnetic flux tubes. However, in the avalanche model of magnetic reconnection, multiple reconnections are expected to occur. The purpose of this research is to first, calculate the point of the greatest stress between magnetic flux tubes and then to allow for dynamic evolution utilising the avalanche model. This represents a significant increase in sophistication over previous models. This undertaking is not purely theoretical since we compare the results of our modelling with HI-C data. Using key inputs from the HIC and AIA observations such as loop length and magnetic field strength, we predict the number of reconnection events likely to take place. As a single reconnection event cannot currently be directly observed, the distribution of flare events are recorded instead. The power law fit yielded as a result of our simulations is within the expected range given the observational evidence of flare distributions and temperature values in the corona. This provides further evidence to support the role of Nano-flares in the heating of the corona.

  20. Test particle acceleration in torsional spine magnetic reconnection

    Science.gov (United States)

    Hosseinpour, M.

    2014-10-01

    Three-dimensional (3D) magnetic reconnection is taking place commonly in astrophysical and space plasmas, especially in solar flares which are rich sources of highly energetic particles. One of the proposed mechanisms for steady-state 3D magnetic reconnection is "torsional spine reconnection". By using the magnetic and electric fields for "torsional spine reconnection", we numerically investigate the features of test particle acceleration with input parameters for the solar corona. We show that efficient acceleration of a relativistic proton is possible near the null point where it can gain up to 100 MeV of kinetic energy within a few milliseconds. However, varying the injection position results in different scenarios for proton acceleration. A proton is most efficiently accelerated when it is injected at the point where the magnetic field lines change their curvature in the fan plane. Moreover, a proton injected far away from the null point cannot be accelerated and, even in some cases, it is trapped in the magnetic field. In addition, adopting either spatially uniform or non-uniform localized plasma resistivity does not much influence the features of trajectory.

  1. Plasmoid-Induced-Reconnection and Fractal Reconnection

    CERN Document Server

    Shibata, K; Shibata, Kazunari; Tanuma, Syuniti

    2001-01-01

    As a key to undertanding the basic mechanism for fast reconnection in solar flares, plasmoid-induced-reconnection and fractal reconnection are proposed and examined. We first briefly summarize recent solar observations that give us hints on the role of plasmoid (flux rope) ejections in flare energy release. We then discuss the plasmoid-induced-reconnection model, which is an extention of the classical two-ribbon-flare model which we refer to as the CSHKP model. An essential ingredient of the new model is the formation and ejection of a plasmoid which play an essential role in the storage of magnetic energy (by inhibiting reconnection) and the induction of a strong inflow into reconnection region. Using a simple analytical model, we show that the plasmoid ejection and acceleration are closely coupled with the reconnection process, leading to a nonlinear instability for the whole dynamics that determines the macroscopic reconnection rate uniquely. Next we show that the current sheet tends to have a fractal stru...

  2. How the Dynamics of Flare Ribbons Can Help Us Understand the Three-dimensional Structure of Reconnection

    Science.gov (United States)

    Qiu, Jiong

    2015-04-01

    Magnetic reconnection occurs in magnetized plasmas in space and astrophysical environment and fusion experiments. It rapidly changes magnetic field converting magnetic energy into other forms. Energy release in solar flares is believed to be governed by reconnection taking place in the Sun's outer atmosphere, the corona. However, the corona is not always the easiest place to measure magnetic field and its change. During a flare, we also observe what happens at the boundary between the Sun's corona and interior, the chromosphere, to learn about reconnection process in the corona. Magnetic field in the Sun's outer atmosphere is line-tied at this boundary; energy flux is largely streamlined by magnetic field to where the field is rooted at this boundary, and quickly heats up the chromosphere, in a way similar to how auroras are produced by charged particles reaching the Earth's atmosphere at geomagnetic poles. Therefore, observing the impacted chromosphere during the flare allows us to track how much and how quickly magnetic flux is reconnected. Whereas probes in fusion experiments or spacecrafts in the Earth's magnetosphere usually sample multiple points for direct in-situ measurements, all reconnection events in the Sun's corona resulting in significant atmosphere heating can be mapped at the boundary with imaging observations of the Sun. From this mapping, we seek to reconstruct the geometry and evolution of reconnection, to understand the dual property of reconnection that is both sporadic and organizable in a flare, and to find out how much energy is released by each burst of reconnection. This talk will discuss recent results and challenges in this practice, inspired by observations of ribbons and loops of solar flares obtained from the Solar Dynamic Observatory and Interface Region Imaging Spectrograph.

  3. DSC Studies of Retrogradation and Amylose-Lipid Complex Transition Taking Place in Gamma Irradiated Wheat Starch

    International Nuclear Information System (INIS)

    Degradation resulting from gamma irradiation induces decrease in order of starch granules and influences the processes occurring in starch-water system. Differential scanning calorimetry (DSC) was applied at present for studying the effect of radiation with doses of 5 - 30 kGy on amylose-lipid complex transition and retrogradation occurring in wheat starch gels. Influence of the conditions applied during DSC measurements and intermediate storage was tested on the possibility to observe radiation effect. Wheat starch was irradiated with 60Co gamma rays in a gamma cell Issledovatiel placed in the Department of Radiation Chemistry, INCT. DSC measurements were performed for ca. 50% and ca. 20% gels during heating - cooling - heating cycles (up to 3 cycles) in the temperature range 10 - 150 degree at heating and cooling rates of 10, 5 and 2.5 degree min-1. The Seiko DSC 6200 calorimeter was used. Decrease in amylose-lipid complex transition temperature was found already after irradiation of wheat starch with a dose of 5 kGy showing modificatin of the complex structure. The differences between the irradiated and the non-irradiated samples became the easier seen in the every foregoing heating or cooling cycle as compared to the preceeding one. It is because that thermal treatment causes decrease of transition temperature in all the irradiated samples, with no effect or increase of that temperature observed in the non-irradiated ones. Irradiation hinders retrogradation taking place in ca. 50% gels but facilitates retrogradation occurring in ca. 20 % gels. Moreover, the expanded differences between the amylose-lipid complex formed in the irradiated and non-irradiated gels result due to their recrystallisation. Storage of the gels induces decrease in the temperature of the complex transition as compared to the last cycle of the first analysis. That decrease was, however, more significant in the case of all the irradiated samples than in the case of the initial sample. In result, the differences between the irradiated and the non-irradiated samples are easier detected after storage. The better differentiation between the amylose-lipid complex transition taking place in particular samples accompanied by the better reproducity were obtained in the case of ca. 50% suspensions as compared to ca. 20% suspensions submitted to the same treatment. The results are discussed in terms of the structural changes resulting in starch due to irradiation. The work was sponsored in the frame of research grant 2P06T 026 27 of Polish Ministry of Scientific Research and Information Technology

  4. DSC studies of retrogradation and amylose-lipid complex transition taking place in gamma irradiated wheat starch

    International Nuclear Information System (INIS)

    The effect of gamma irradiation (60Co) with doses of 5-30 kGy on the amylose-lipid complex transition and retrogradation occurring in gels containing ca. 50% and ca. 20% wheat starch was studied by differential scanning calorimetry (DSC) during heating-cooling-heating cycles (up to three cycles). Transition of the amylose-lipid complex occurs in all the irradiated samples at a lower temperature as compared to the non-irradiated starch. That effect was larger when the radiation dose was higher. A further thermal treatment causes a decrease of the transition temperature in the irradiated samples, with no effect or increase of that temperature observed for the non-irradiated ones. Irradiation hinders retrogradation taking place in 50% gels but facilitates the process occurring in 20% gels. The differences between the irradiated and the non-irradiated samples are more evident in the every next heating or cooling cycle as well as after storage and in the case of ca. 50% suspensions as compared to ca. 20% suspensions. The results point out to the deterioration of the structure of the complexes formed in the irradiated starch as compared to the non-irradiated one

  5. 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)

  6. Spreading of Magnetic Reconnection X-lines in Three Dimensions

    Science.gov (United States)

    Cassak, Paul; Shepherd, Lucas

    2012-03-01

    Naturally occurring magnetic reconnection often begins in a spatially localized region and spreads in the out-of-plane direction in time. A number of authors have studied this problem for magnetotail applications such as substorms and bursty bulk flows, for which the out-of-plane (guide) field is typically small. However, spreading also occurs in laboratory experiments and two-ribbon solar flares (such as the Bastille Day flare), and is inferred to occur at the dayside magnetopause. The reconnection site in each of these settings is known or thought to have a significant guide field. With no guide field, it was shown that the reconnection spreading is controlled by the species that carries the current. However, laboratory experiments with a large guide field (Katz et al., Phys. Rev. Lett., 104, 255004, 2010) revealed that spreading takes place in both directions at the Alfven speed based on the guide field. This implies a qualitative change of behavior as the guide field varies. We present a scaling argument for the condition on the guide field at which the nature of the spreading switches from being caused by current carriers to Alfven waves. Further, we show results of three-dimensional two-fluid simulations that agree with the theory. We discuss applications to observations.

  7. Observations of Electron Vorticity in the Inner Plasmasheet and Its Relationship to Reconnection

    Science.gov (United States)

    Gurgiolo, Chris A.; Goldstein, Melvyn L.; Matthaeus, William H.; Vinas, Adolfo -F.

    2011-01-01

    Spatial derivatives of the electron moments can be estimated using data from the four Cluster spacecraft. Using spatial derivatives of the velocity we have computed the vorticity in the plasmasheet for several crossings. What we have found is that vorticity appears to be a common feature in the inner plasmasheet. We will show a number of examples. In at least some of the observations the vorticity is well correlated with the passage of Cluster through the ion diffusion region of known reconnection events. That most of the vorticity events observed are reconnection related cannot be dismissed and in fact observations of vorticity may provide a means to locate times when the Cluster spacecraft are magnetically connected to regions where reconnection is taking place. Understanding the role and source of the vorticity should advance our understanding of the dissipation of the turbulence associated with reconnection. In the course of the presentation we will also touch on the methods used to estimate the spatial derivatives as well as the limitations and assumptions involved.

  8. Young People Take Their Rightful Places as Full and Contributing Members of a World Class Workforce: Philadelphia Youth Network Annual Report 2006

    Science.gov (United States)

    Philadelphia Youth Network, 2006

    2006-01-01

    The title of this year's annual report has particular meaning for all of the staff at the Philadelphia Youth Network. The phrase derives from Philadelphia Youth Network's (PYN's) new vision statement, developed as part of its recent strategic planning process, which reads: All of our city's young people take their rightful places as full and…

  9. Magnetic Reconnection in Astrophysical Environments

    CERN Document Server

    Lazarian, A; Vishniac, E; Kowal, G

    2014-01-01

    Magnetic reconnection is a process that changes magnetic field topology in highly conducting fluids. Traditionally, magnetic reconnection was associated mostly with solar flares. In reality, the process must be ubiquitous as astrophysical fluids are magnetized and motions of fluid elements necessarily entail crossing of magnetic frozen in field lines and magnetic reconnection. We consider magnetic reconnection in realistic 3D geometry in the presence of turbulence. This turbulence in most astrophysical settings is of pre-existing nature, but it also can be induced by magnetic reconnection itself. In this situation turbulent magnetic field wandering opens up reconnection outflow regions, making reconnection fast. We discuss Lazarian \\& Vishniac (1999) model of turbulent reconnection, its numerical and observational testings, as well as its connection to the modern understanding of the Lagrangian properties of turbulent fluids. We show that the predicted dependences of the reconnection rates on the level of...

  10. 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.

    2011-02-01

    A statistical study of flux ropes and traveling compression regions (TCRs) during the Time History of Events and Macroscale Interactions during Substorms second tail season has been performed. A combined total of 135 flux ropes and TCRs in the range GSM X ˜ -14 to -31 RE 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 reconnection 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 (XGSM, Y*GSM) = (-30RE, 5RE), 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* > 0. Our results indicate that the Earthward flows are similarly asymmetric in the midtail region, becoming more symmetric inside -18 RE. Superposed epoch analyses indicate that the occurrence of reconnection closer to the Earth, i.e., X > -20 RE, is associated with elevated solar wind velocity and enhanced negative interplanetary magnetic field BZ. 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 ˜ -25 RE.

  11. Asymmetric Magnetic Reconnection in Weakly Ionized Chromospheric Plasmas

    CERN Document Server

    Murphy, Nicholas A

    2015-01-01

    Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection, the current sheet thins to the scale of the neutral-ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak field (high ...

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

    International Nuclear Information System (INIS)

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

  13. Ion Acceleration During Magnetic Reconnection

    Science.gov (United States)

    Drake, J. F.; Swisdak, M.; Phan, T. D.; Cassak, P. A.; Shay, M. A.; Lepri, S. T.; Quataert, E.; Lin, R. P.; Zurbuchen, T. H.

    2008-12-01

    We explore the mechanism for ion acceleration during magnetic reconnection to understand the energetic particle spectra produced during flares and in the solar wind. Reconnection driven ion acceleration is initiated as particles move from upstream into the Alfvenic exhaust. In the case of a weak guide field, protons and higher mass particles behave like pickup particles in that they abruptly cross a narrow boundary layer and find themselves in a region of Alfvenic outflow. Their motion then mimics that of a classic pickup ion, gaining an Alfvenic ExB flow in the jet and a thermal speed close to the Alfven speed. In the case of a strong guide field particle acceleration is strongly enhanced for ions with high mass-to-charge (m/q) ratio since these particles act as pick-up particles while small m/q particles are adiabatic. Once ions become super-Aflvenic their acceleration is, like electrons, dominated by Fermi reflection during island contraction and their energy increases until it is limited by firehose marginal stability. The ion distribution function for super-Alfvenic ions then takes the form of a v-5 distribution. During reconnection in a multi-island environment, as in flares, strong enhancements in high m/q ions are expected. This picture is consistent with several observations related to flare and local solar wind ion acceleration: (1) the ubiquitous observations of energy proportional to mass; (2) strong enhancements in high m/q ions during impulsive flares; and (3) the temperature increments of solar wind exhausts.

  14. Stuck between a ROC and a hard place? Barriers to the take up of green energy in the UK

    International Nuclear Information System (INIS)

    This paper examines the UK mechanisms for ensuring future investment in renewable energy through consumer adoption of green energy tariffs and the Renewable Obligation Certificate (ROC) system. Using a national survey and focus groups the stated willingness by UK customers to pay a premium for renewable or green energy and actual take up of such tariffs is assessed. Substantial differences between willingness to pay for and the adoption of green energy tariffs are reported. This disparity is linked to a range of factors including consumer confusion, lack of supply, complexities of constructing 'green source' tariffs under the ROC system and a lack of customer trust. It is concluded that the re-definition of the green energy market in favour of 'green source' tariffs, greater direct compliance with the Renewable Obligation by addressing supply constraints, and efforts in providing clearer information and choices for consumers via a compulsory green energy accreditation scheme are required if willing consumers' are to contribute to investment in renewable energy. (author)

  15. Skewed magnetic field lines reconnection

    International Nuclear Information System (INIS)

    Three-dimensional time-dependent reconnection of skewed magnetic field lines is studied. Reconnection is shown to be possible only in the limited oval-shaped part of the current sheet, which was called the reconnection zone. The size of the reconnection zone is defined by the reconnection line length, the behaviour of the electric field in the diffusion region as well as by the angle between the reconnecting fields. Reconnected magnetic flux has the same direction as it has in the Petschek's model near the reconnection line (normal flux), but it changes its sign in the rest of the reconnection zone (anomalous flux). The magnetic energy is converted into the kinetic one in the normal flux region, and the reverse process occurs in the anomalous flux region, so the energy balance is fulfilled within the reconnection region. An electric double layer emerges along the reconnection zone, which emits Alfven waves, these carryin away the energy released in the reconnection process. The solution obtained may be useful in various problems of cosmic plasma physics, e.g. MHD waves generation on the Sun, carrying magnetic flux away from its surface, origin of solar cosmic rays, etc

  16. Forced magnetic reconnection

    International Nuclear Information System (INIS)

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

  17. 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

    Full Text Available The business-life related competition established in modern communities has also brought about some other problems. The attacks and intimidation attempts have introduced the term of “mobbing” which is defined as regular and continuous psychological violence faced by people always trying to produce and win from those who they work with. The term of “mobbing” has recently become a popular academic issue which has been sophisticatedly handled in relevant literature. Mobbing is defined as the act of continuous and systematic intimidation purposefully performed by either some employees or employers on some employees through emotional violence. As mobbing is considered to be significant for both corporate and employee, the starting point of this study was to investigate how mobbing acts are reflected on newspapers as they are mass communication means. One of the most important means of media is print media. Print media is the first means of media when mentioned about media. Newspapers are means through which people are always kept up to date about the latest news in civilized societies. With this regard, the most basic purpose of this study is to investigate the news about the mobbing events experienced in higher education system under the light of national policy documents and reports. The study was carried out based on a qualitative approach. The news released in print media was chosen purposefully as print media means report news in a detailed way, have an evidential value and can be read again on demand. The research group in this study consists of the mobbing news released on Hurriyet, Sabah and Zaman which are newspapers published in Turkey between the years of 2009-2013. These newspapers were purposefully chosen based on criterion sampling method. The most basic understanding underlying this sampling method is to study on all cases which meet the standards set prior to the start of the study. The newspapers mentioned above were chosen 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.

  18. 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

  19. 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...

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

    International Nuclear Information System (INIS)

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

  1. 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...

  2. Colour reconnection in Herwig

    International Nuclear Information System (INIS)

    As the LHC's quick step-up in luminosity necessarily comes with increasing pile-up activity accompanying every event of interest, the Monte Carlo event generators have to come up with proper models of soft inclusive hadron collisions. Moreover, an irreducible background of hadronic activity, the underlying event, is adherent to the single hard hadron collisions themselves. We report on colour reconnection in Herwig, which provides improvements in these two fields of current research.

  3. 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.

  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. Does fast magnetic reconnection exist?

    Science.gov (United States)

    Priest, E. R.; Forbes, T. G.

    1992-01-01

    The main features of the Priest-Forbes (1986) and Priest-Lee (1990) models of magnetic reconnection in astrophysical plasmas are discussed, and the Priest-Lee model is generalized to include inflow pressure gradients and thus different regimes of reconnection. It is shown that different scaling results can be obtained depending on the boundary conditions. These results are compared to the ones observed in the numerical experiments of Biskamp (1986) and Lee and Fu (1986). It is concluded that numerical experiments with suitably designed boundary conditions are likely to exhibit fast reconnection, and that such reconnection is a common process in astrophysical and space plasmas.

  6. 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

    Pig small intestinal mucosal explants, labelled with [35S]-methionine, were fractionated into Mg2+-precipitated (intracellular and basolateral) and microvillar membranes, and the orientation of newly synthesized aminopeptidase N (EC 3.4.11.2) in vesicles from the two fractions was studied by its ...... for microvillar enzymes, the aspects of sorting studied take place in, or shortly after exit from, the Golgi complex.......Pig small intestinal mucosal explants, labelled with [35S]-methionine, were fractionated into Mg2+-precipitated (intracellular and basolateral) and microvillar membranes, and the orientation of newly synthesized aminopeptidase N (EC 3.4.11.2) in vesicles from the two fractions was studied by its...

  7. Asymmetric Magnetic Reconnection in Weakly Ionized Chromospheric Plasmas

    Science.gov (United States)

    Murphy, Nicholas A.; Lukin, Vyacheslav S.

    2015-06-01

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

  8. Reconnections of Wave Vortex Lines

    Science.gov (United States)

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

    2012-01-01

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

  9. Hall assisted forced magnetic reconnection

    Science.gov (United States)

    Vekstein, G.; Bian, N. H.

    2006-12-01

    The role of the Hall effect in forced magnetic reconnection is investigated analytically for the so-called Taylor problem. In the latter, a tearing stable slab plasma equilibrium, which is chosen here to be a simple magnetic field reversal, is subjected to a small-amplitude boundary deformation that drives magnetic reconnection (hence the adjective "forced" ) at the neutral surface within the plasma. It is shown that such reconnection becomes substantially accelerated by the Hall effect when the nondimensional parameter di=(c/?pi)/a exceeds S-1/5. Here, c /?pi is the ion inertial skin depth, a is the width of the plasma slab, and S ?1 is the Lundquist number of a highly conducting plasma. Two different types of external perturbation are considered. In the case of continuous quasistatic driving, with a frequency ? such that ??A?1, ?A being the Alfvén transit time, various reconnection regimes are identified. The corresponding heating rates, which are determined by the parameters di, S, and ??A, are derived. In the case of a "one-off" reconnection event, we demonstrate when and how the transition from the Hall regime to the magnetohydrodynamic regime occurs in the course of the reconnection process. It is found that the peak instantaneous reconnection rate scales as d?1(0)/dt ˜di1/2S-1/2(B0?0/?A), where ?1(0) is the reconnected magnetic flux, B0 is the magnetic field strength, and ?0 is the amplitude of the boundary deformation.

  10. Reconnections of Wave Vortex Lines

    Science.gov (United States)

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

    2012-01-01

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

  11. THEMIS Reconnection Animation

    Science.gov (United States)

    2006-01-01

    As the Sun's ionized and magnetized particles are passing by Earth they impart mechanical energy which is transformed into magnetic energy by compressing the tail. The tail field lines eventually merge (or 'reconnect') and slingshot particles towards and away from Earth, thereby converting magnetic into particle energy. This energy finds itself along field lines and powers the aurora on the one hand, and down the tail via the expulsion of a plasma blob, a plasmoid, on the other. This storage-and-release process of solar wind energy by the magnetosphere is called a substorm.

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

    Science.gov (United States)

    Lapenta, Giovanni; Markidis, Stefano; Goldman, Martin V.; Newman, David L.

    2015-08-01

    The primary target of the Magnetospheric MultiScale (MMS) mission is the electron-scale diffusion layer around reconnection sites. Here we study where these regions are found in full three-dimensional simulations. In two dimensions the sites of electron diffusion, defined as the regions where magnetic topology changes and electrons move with respect to the magnetic field lines, are located near the reconnection site. But in three dimensions we find that the reconnection exhaust far from the primary reconnection site also becomes host to secondary reconnection sites. Four diagnostics are used to demonstrate the point: the direct observation of topology impossible without secondary reconnection, the direct measurement of topological field line breakage, the measurement of electron jets emerging from secondary reconnection regions, and the violation of the frozen-in condition. We conclude that secondary reconnection occurs in a large part of the exhaust, providing many more chances for MMS to find itself in the right region to hit its target.

  13. Magnetic reconnection launcher

    Science.gov (United States)

    Cowan, Maynard (Albuquerque, NM)

    1989-01-01

    An electromagnetic launcher includes a plurality of electrical stages which are energized sequentially in synchrony with the passage of a projectile. Each stage of the launcher includes two or more coils which are arranged coaxially on either closed-loop or straight lines to form gaps between their ends. The projectile has an electrically conductive gap-portion that passes through all the gaps of all the stages in a direction transverse to the axes of the coils. The coils receive an electric current, store magnetic energy, and convert a significant portion of the stored magnetic energy into kinetic energy of the projectile by magnetic reconnection as the gap portion of the projectile moves through the gap. The magnetic polarity of the opposing coils is in the same direction, e.g. N-S-N-S. A gap portion of the projectile may be made from aluminum and is propelled by the reconnection of magnetic flux stored in the coils which causes accelerating forces to act upon the projectile at both the rear vertical surface of the projectile and at the horizontal surfaces of the projectile near its rear. The gap portion of the projectile may be flat, rectangular and longer than the length of the opposing coils and fit loosely within the gap between the opposing coils.

  14. Investigations of the Reconnecting Current Sheets in Solar Eruptions

    Science.gov (United States)

    Lin, Jun; Li, J.; Forbes, T. G.; Ko, Y.; Raymond, J. C.; van Ballegooijen, A. A.; Vourlidas, A.

    2006-06-01

    Observations and theories continuously provide evidence of formation and development of the reconnecting current sheets during major eruptions. Because the high electric conductivity and the force-free environment of the solar corona, the current sheet is usually confined in a small volume compared to the other structures involved in the eruption in order to allow the energy conversion or magnetic reconnection to take place at a plausible rate. The work investigating the sizes, especially thickness, of the current sheet developed by the eruption in reality was never conducted before since it is believed that the current sheet is too thin to be observable. It has often been stated that the thickness is limited either by the Lamor radius of particles, which is about tens of meters in the coronal environment, or by the mean-free-path of particles in the region where the interaction between particles and ion-acoustic waves occurs. In the latter case, the particle mean-free-path is a few kilometers. Here we use a set of unique observations provided by the UVCS and LASCO experiments on SOHO to determine the thickness, d, and furthermore the electric resistivity, etae, of the current sheets for three eruptive events. We find that d ranges from 1.0 x 104 km to 6.0 x 105 km, and etae from 1.0 x 105 ohm m to 4.0 x 106 ohm m. These values of etae are 12-14 orders of magnitude greater than the classical collisional resistivity, 4-6 orders of magnitude greater than estimates of anomalous resistivity, and even 1-3 orders greater than those often used for solar flares. The existence of such large values for d and etae suggests that large scale turbulent processes are operating within the current sheet. Understanding how a high level of turbulence can develop so rapidly is a challenging goal for future research.

  15. 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).

  16. Mathematical Modeling of a Cs(I – Sr(II – Bentonite – Magnetite Sorption System, Simulating the Processes Taking Place in a Deep Geological Repository

    Directory of Open Access Journals (Sweden)

    H. Filipská

    2005-01-01

    Full Text Available The derivation of mathematical models of systems consisting of Cs(I or Sr(II and of bentonite (B, magnetite (M or their mixtures (B+M are described. The paper deals especially with modeling of the protonation and sorption processes occurring on the functional groups of the solid phase, namely on so called edge sites and layer sites. The two types of sites have different properties and, as a result, three types of Surface Complexation Models (SCM are used for edge sites, viz. two electrostatic SCMs: the Constant Capacitance Model (CCM and the Diffusion Double Layer Model (DLM, and one without electrostatic correction: the Chemical Model (CEM. The processes taking place on the layer sites are described by means of the Ion Exchange Model (IExM. In the course of modeling, the speciation of the given metal in the liquid (aqueous phase has to be taken into account. In principle, the model of protonation or sorption processes is based on the reactions occurring in the aqueous phase and on the surface of the solid phase, and comprises not only the equations of the equilibrium constants of the individual reactions, but also the mass and charge balance equations. The algorithm of the numerical solution is compatible with FAMULUS 3.5 (a Czech software product quite extensively used at Czech universities in the last decade, the bookcase codes of which are utilized. 

  17. 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 {magnetic flux ropes exhibiting turbulent magnetic power spectra of very flat power-law shape W_b? k^{-? } in wavenumber k with power becoming as low as ? ? 2. Spontaneous reconnection 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-mode reconnection over the drift-kink deformation of the current sheet. Lepton acceleration occurs in the reconnection-electric field in multiple encounters with the exhausts and plasmoids. This is a Fermi-like process. It results in power-law tails on the lepton energy distribution. This effect becomes pronounced in ultra-relativistic reconnection where it yields extremely hard lepton power-law energy spectra approaching F(? )? ? ^{-1}, with ? the lepton energy. The synchrotron radiation limit becomes substantially exceeded. Relativistic reconnection is a probable generator of current and magnetic turbulence, and a mechanism that produces high-energy radiation. It is also identified as the ultimate dissipation mechanism of the mechanical energy in collisionless magnetohydrodynamic turbulent cascades via lepton-inertial-scale turbulent current filaments. In this case, the volume-filling factor is large. Magnetic turbulence causes strong plasma heating of the entire turbulent volume and violent acceleration via spontaneous lepton-scale reconnection. This may lead to high-energy particle populations filling the whole volume. In this case, it causes non-thermal radiation spectra that span the entire interval from radio waves to gamma rays.

  18. Plasmoid Ejections and Loop Contractions in an Eruptive M7.7 Solar Flare: Evidence of Particle Acceleration and Heating in Magnetic Reconnection Outflows

    CERN Document Server

    Liu, Wei; Petrosian, Vahe'

    2013-01-01

    Where particle acceleration and plasma heating take place in relation to magnetic reconnection is a fundamental question for solar flares. We report analysis of an M7.7 flare on 2012 July 19 observed by SDO/AIA and RHESSI. Bi-directional outflows in forms of plasmoid ejections and contracting cusp-shaped loops originate between an erupting flux rope and underlying flare loops at speeds of typically 200-300 km/s up to 1050 km/s. These outflows are associated with spatially separated double coronal X-ray sources with centroid separation decreasing with energy. The highest temperature is located near the nonthermal X-ray loop-top source well below the original heights of contracting cusps near the inferred reconnection site. These observations suggest that the primary loci of particle acceleration and plasma heating are in the reconnection outflow regions, rather than the reconnection site itself. In addition, there is an initial ascent of the X-ray and EUV loop-top source prior to its recently recognized descen...

  19. Reconnection of superfluid vortex bundles.

    Science.gov (United States)

    Alamri, Sultan Z; Youd, Anthony J; Barenghi, Carlo F

    2008-11-21

    Using the vortex filament model and the Gross-Pitaevskii nonlinear Schroedinger equation, we show that bundles of quantized vortex lines in He II are structurally robust and can reconnect with each other maintaining their identity. We discuss vortex stretching in superfluid turbulence and show that, during the bundle reconnection process, kelvin waves of large amplitude are generated, in agreement with the finding that helicity is produced by nearly singular vortex interactions in classical Euler flows. PMID:19113421

  20. Can magnetopause reconnection drive Saturn's magnetosphere?

    Science.gov (United States)

    Masters, A.; Fujimoto, M.; Hasegawa, H.; Russell, C. T.; Coates, A. J.; Dougherty, M. K.

    2014-03-01

    While solar wind-driven compression of Saturn's magnetosphere is an important trigger of magnetospheric dynamics, the importance of magnetopause reconnection has been the subject of debate. Here we use Cassini observations at Saturn's magnetopause to address this open issue. Measured conditions at the boundary suggest a typical reconnection electric field strength of order 0.01 mV m-1. Although the strongest reconnection electric fields correspond to a compressed magnetosphere, compressed conditions do not guarantee a relatively strong reconnection electric field at the magnetopause location sampled by the spacecraft. By considering northward Interplanetary Magnetic Field (IMF), we predict reconnection voltages (open magnetic flux production rates) for the strongest driving of Saturn's magnetosphere by magnetopause reconnection. The typical northward IMF reconnection voltage is less than 100 kV for a wide range of reconnection X line lengths. This suggests that magnetopause reconnection is not a major driver of dynamics in Saturn's magnetosphere, except possibly on rare occasions.

  1. 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, we mention H? spectra of the 18 September 1995 eruptive prominence which indicate the bi-directional plasma flow as expected in the reconnection process.

  2. Helicity, Reconnection, and Dynamo Effects

    International Nuclear Information System (INIS)

    The inter-relationships between magnetic helicity, magnetic reconnection, and dynamo effects are discussed. In laboratory experiments, where two plasmas are driven to merge, the helicity content of each plasma strongly affects the reconnection rate, as well as the shape of the diffusion region. Conversely, magnetic reconnection events also strongly affect the global helicity, resulting in efficient helicity cancellation (but not dissipation) during counter-helicity reconnection and a finite helicity increase or decrease (but less efficiently than dissipation of magnetic energy) during co-helicity reconnection. Close relationships also exist between magnetic helicity and dynamo effects. The turbulent electromotive force along the mean magnetic field (alpha-effect), due to either electrostatic turbulence or the electron diamagnetic effect, transports mean-field helicity across space without dissipation. This has been supported by direct measurements of helicity flux in a laboratory plasma. When the dynamo effect is driven by electromagnetic turbulence, helicity in the turbulent field is converted to mean-field helicity. In all cases, however, dynamo processes conserve total helicity except for a small battery effect, consistent with the observation that the helicity is approximately conserved during magnetic relaxation

  3. Magnetic reconnection models of flares

    Science.gov (United States)

    Forbes, T. G.

    1988-01-01

    The most feasible energy source for solar and stellar flares is the energy stored in coronal magnetic fields. To convert a significant fraction of this energy into heat and kinetic energy in a short time requires rapid change in the topology of the magnetic fields, and hence, rapid reconnection of field lines. Recent numerical and analytical models of solar flares suggest that the magnetic energy released by reconnection drives chromospheric ablation in the flare ribbons. Simple theoretical arguments based on compressible reconnection theory predict that the temperature of the ablated plasma should be about 1.03 x 10 to the 6th B exp 0.62 K where B is the coronal magnetic field strength in Gauss.

  4. 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) regimes. New results are reported in both cases.

  5. The Spreading of X-lines in Three Dimensions during Magnetic Reconnection with a Guide Field

    Science.gov (United States)

    Shepherd, L. S.; Cassak, P.

    2011-12-01

    Naturally occurring magnetic reconnection often begins in a spatially localized region and spreads in the out-of-plane direction as time progresses. This has been studied by a number of authors for magnetotail applications such as substorms and bursty bulk flows, for which the out-of-plane (guide) field is typically small. However, this same behavior has been observed in laboratory experiments, in two-ribbon solar flares (such as the Bastille Day flare), and at the dayside of the magnetopause. In each of these settings, a significant guide field is present. Without a guide field, it was shown that the reconnection spreading is controlled by the species that carries the current. However, laboratory experiments with a large guide field (Katz et al., Phys. Rev. Lett., 104, 255004, 2010) revealed that the spreading takes place in both directions at the Alfven speed based on the guide magnetic field. We present three-dimensional two-fluid numerical simulations to address the condition on the guide field at which the nature of the spreading switches from being caused by the current carriers to being caused by Alfven waves. Applications for the corona will be discussed.

  6. 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.

  7. Reconnection and merging of positive streamers in air

    CERN Document Server

    Nijdam, S; van Veldhuizen, E M; Ebert, U

    2008-01-01

    Pictures show that streamer or sprite discharge channels emerging from the same electrode sometimes seem to reconnect or merge though their heads carry electric charge of the same polarity; one might therefore suspect that reconnections are an artifact of the two-dimensional projection in the pictures. Here we use stereo-photography to investigate the full three-dimensional structure of such events. We analyze reconnection, possibly an electrostatic effect in which a late thin streamer reconnects to an earlier thick streamer channel, and merging, a suggested photoionization effect in which two simultaneously propagating streamer heads merge into one new streamer. We use four different anode geometries (one tip, two tips, two asymmetric protrusions in a plate, and a wire), placed 40 mm above a flat cathode plate in ambient air. A positive high voltage pulse is applied to the anode, creating a positive corona discharge. This discharge is studied with a fast ICCD camera, in many cases combined with optics to ena...

  8. Fast Reconnection in a Weakly Stochastic Field

    International Nuclear Information System (INIS)

    We discuss a generic mechanism for fast reconnection based on a small level of field stochasticity. The presence of noise boosts the reconnection rate in two ways. First, individual field lines enter and leave the reconnection zone on length scales which are much shorter than the transverse scale of the reconnection zone. Second, the reconnection layer involves the simultaneous reconnection of many independent flux elements. The net effect is that the reconnection speed is limited only by the ejection of plasma from a diffusion-broadened zone around the actual reconnection layer, and is independent of the plasma resistivity. Using Goldreich and Sridhar's model of strong turbulence in a magnetized plasma with negligible intermittency, we find that the reconnection speed in a turbulent medium is close to VA.M2, where M is the ratio of the plasma turbulent velocity to the Alfven speed. Plausible alternative models of MHD turbulence change this result only slightly. The fraction of magnetic energy that goes directly into electron heating is of order RB-2/5M8/5 (where RB is the Lundquist number), so that the usual assumption that reconnection leads to ohmic heating does not hold. A somewhat larger fraction of the magnetic energy, ?RB-1/5M6/5, goes into high frequency Alfven waves. The remainder of the energy liberated by reconnection goes turbulent motions on the scale of the reconnection sheet length. The current sheet remains thin, of order RB-3/5M-2/5 times the current sheet length. We claim that the qualitative sense of these conclusions, that reconnection is fast even though current sheets are narrow, is almost independent of the local physics of reconnection and the nature of the turbulent cascade. We comment briefly on the nature of magnetic flares. (author)

  9. Multiple Spacecraft Study of the Impact of Turbulence on Reconnection Rates

    Science.gov (United States)

    Wendel, Deirdre; Goldstein, Melvyn; Figueroa-Vinas, Adolfo; Adrian, Mark; Sahraoui, Fouad

    2011-01-01

    Magnetic turbulence and secondary island formation have reemerged as possible explanations for fast reconnection. Recent three-dimensional simulations reveal the formation of secondary islands that serve to shorten the current sheet and increase the accelerating electric field, while both simulations and observations witness electron holes whose collapse energizes electrons. However, few data studies have explicitly investigated the effect of turbulence and islands on the reconnection rate. We present a more comprehensive analysis of the effect of turbulence and islands on reconnection rates observed in space. Our approach takes advantage of multiple spacecraft to find the location of the spacecraft relative to the inflow and the outflow, to estimate the reconnection electric field, to indicate the presence and size of islands, and to determine wave vectors indicating turbulence. A superposed epoch analysis provides independent estimates of spatial scales and a reconnection electric field. We apply k-filtering and a new method adopted from seismological analyses to identify the wavevectors. From several case studies of reconnection events, we obtain preliminary estimates of the spectral scaling law, identify wave modes, and present a method for finding the reconnection electric field associated with the wave modes.

  10. TCR comodulation of nonengaged TCR takes place by a protein kinase C and CD3 gamma di-leucine-based motif-dependent mechanism

    DEFF Research Database (Denmark)

    Bonefeld, Charlotte Menné; Rasmussen, B. A.; Lauritsen, J P; von Essen, Marina; Odum, Niels; Andersen, Peter S; Geisler, Carsten

    2003-01-01

    One of the earliest events following TCR triggering is TCR down-regulation. However, the mechanisms behind TCR down-regulation are still not fully known. Some studies have suggested that only directly triggered TCR are internalized, whereas others studies have indicated that, in addition to...... triggered receptors, nonengaged TCR are also internalized (comodulated). In this study, we used transfected T cells expressing two different TCR to analyze whether comodulation took place. We show that TCR triggering by anti-TCR mAb and peptide-MHC complexes clearly induced internalization of nonengaged TCR...

  11. NS [Nuclear Safety] update. Current safety and security activities and developments taking place in the Department of Nuclear Safety and Security, Issue no. 8, September 2008

    International Nuclear Information System (INIS)

    The current issue presents information about the following activities: 1) International Workshops on Denial of Shipments raise awareness of suppliers, recipients, regulators, carriers/consignors and international organizations of the problems relating to denials of radioactive shipments to determine effective measures to prevent or reduce the instances of shipment denials and delays. 2) Communication and knowledge Management in the Department of Nuclear Safety and Security (NS). 3) Nuclear Security at the Beijing Olympics - an excellent example of the IAEA's work in protecting large scale public events. 4) The Incident and Emergency Centre's Participation in the ConvEx 3 Exercise, 9-10 July 2008, which took place at the Laguna Verde nuclear power plant in Mexico. During the 43 hour long exercise, the Incident and Emergency Centre (IEC) was fully activated. Staff members participating in the exercise represented different departments within the IAEA and the diversity of their knowledge and experience ensured an effective response

  12. 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)

  13. 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...

  14. Indeterminacy and instability in Petschek reconnection

    International Nuclear Information System (INIS)

    We explain two puzzling aspects of Petschek's model for fast reconnection. One is its failure to occur in plasma simulations with uniform resistivity. The other is its inability to provide anything more than an upper limit for the reconnection rate. We have found that previously published analytical solutions based on Petschek's model are structurally unstable if the electrical resistivity is uniform. The structural instability is associated with the presence of an essential singularity at the X-line that is unphysical. By requiring that such a singularity does not exist, we obtain a formula that predicts a specific rate of reconnection. For uniform resistivity, reconnection can only occur at the slow, Sweet-Parker rate. For nonuniform resistivity, reconnection can occur at a much faster rate provided that the resistivity profile is not too flat near the X-line. If this condition is satisfied, then the scale length of the nonuniformity determines the reconnection rate

  15. Patchy Reconnection in the Solar Corona

    CERN Document Server

    Guidoni, Silvina E

    2011-01-01

    Supra-arcade downflows (SADs) and supra-arcade downflowing loops (SADLs) descending from reconnection regions toward solar post-flare arcades seem to be two different observational signatures of retracting, isolated reconnected flux tubes with irreducible three-dimensional geometries. This dissertation describes work in refining and improving a novel model of patchy reconnection, where only a small bundle of field lines is reconnected across a current sheet and forms a reconnected thin flux tube. Traditional models have not been able to explain why some of the observed SADs appear to be hot and relatively devoid of plasma. The present work shows that plasma depletion naturally occurs in flux tubes that are reconnected across nonuniform current sheets and slide trough regions of decreasing magnetic field magnitude. Moreover, through a detailed theoretical analysis of generalized thin flux tube equations, we show that the addition to the model of pressure-driven parallel dynamics, as well as temperature-depende...

  16. Indeterminacy and instability in Petschek reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Forbes, Terry G. [Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824 (United States); Priest, Eric R. [Institute of Mathematics, University of St. Andrews, Fife KY16 9SS, Scotland (United Kingdom); Seaton, Daniel B. [SIDC-Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels (Belgium); Litvinenko, Yuri E. [Department of Mathematics, University of Waikato, P.O. 3105, Hamilton (New Zealand)

    2013-05-15

    We explain two puzzling aspects of Petschek's model for fast reconnection. One is its failure to occur in plasma simulations with uniform resistivity. The other is its inability to provide anything more than an upper limit for the reconnection rate. We have found that previously published analytical solutions based on Petschek's model are structurally unstable if the electrical resistivity is uniform. The structural instability is associated with the presence of an essential singularity at the X-line that is unphysical. By requiring that such a singularity does not exist, we obtain a formula that predicts a specific rate of reconnection. For uniform resistivity, reconnection can only occur at the slow, Sweet-Parker rate. For nonuniform resistivity, reconnection can occur at a much faster rate provided that the resistivity profile is not too flat near the X-line. If this condition is satisfied, then the scale length of the nonuniformity determines the reconnection rate.

  17. 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.

  18. Solar flares: an extremum of reconnection

    International Nuclear Information System (INIS)

    Three points are emphasized: that the solar flare is that particular astrophysical phenomenon that is the extremum of reconnection, no other phenomenon demands as rapid magnetic flux annihilation as is seen in the solar flare; that plasma physics experiments can and should be performed in the laboratory that model reconnection as we observe it in astrophysics; and that stochastic field lines derived from something similar to Alfven wave turbulence are a necessary part of reconnection

  19. Driven reconnection and bursty bulk flows

    OpenAIRE

    Pandey, B.P.; Lakhina, G. S.

    2001-01-01

    The energetics of driven magnetic reconnections induced by the deformation of the magnetopause boundary due to the solar wind-magnetosphere interaction are studied. The bursty type reconnection ensues due to the forcing of the magnetopause boundary by the solar wind. For typical plasma parameters in the inner central plasma sheet (ICPS), the magnetic energy release during the reconnection is estimated and it is found that the available free energy is comparable to the observed kinetic ...

  20. Magnetic Reconnection in a Compressible MHD Plasma

    Science.gov (United States)

    Hesse, Michael; Birn, Joachim; Zenitani, Seiji

    2011-01-01

    Using steady-state resistive MHD, magnetic reconnection is reinvestigated for conditions of high resistivity/low magnetic Reynolds number, when the thickness of the diffusion region is no longer small compared to its length. Implicit expressions for the reconnection rate and other reconnection parameters are derived based on the requirements of mass, momentum, and energy conservation. These expressions are solved via simple iterative procedures. Implications specifically for low Reynolds number/high resistivity are being discussed

  1. Toward an Interdisciplinary Understanding of Place: Lessons for Environmental Education

    Science.gov (United States)

    Ardoin, Nicole M.

    2006-01-01

    Sense of place is lauded as critical to developing an environmentally conscious and responsive citizenry. Calls for place-based education have often arisen from an emotional plea to reconnect to the land, become rooted, and conserve natural places. However, in reality, sense of place encompasses a multidimensional array that is not only…

  2. Continuous transition from fast magnetic reconnection to slow reconnection and change of the reconnection system structure

    CERN Document Server

    Nitta, S

    2007-01-01

    This paper analytically investigates a series of two-dimensional MHD reconnection solutions over a wide variation of magnetic Reynolds number ($R_{em}^*$). A new series of solutions explains a continuous transition from Petschek-like fast regime to a Sweet-Parker-like slow regime. The inflow region is obtained from a Grad-Shafranov analysis used by Nitta et al. 2002 and the outflow region from a shock-tube approximation used by Nitta 2004, 2006. A single X-point (Petschek-like) solution forms for a sufficiently small $R_{em}^*$. As $R_{em}^*$ gradually increases, the solutions shifts to an X-O-X solution with a magnetic island between two X-points. When $R_{em}^*$ increases further, the island collapses to a new elongated current sheet with Y-points at both ends (Sweet-Parker-like). These reconnection structures expand self-similarly as time proceeds. As $R_{em}^*$ increases, the reconnection rate and the reducible fraction of the initial magnetic energy of the system decrease as power-law functions of $R_{em...

  3. Definition of spontaneous reconnection

    International Nuclear Information System (INIS)

    The author discusses his view of driven versus spontaneous. There is a close link between ''spontaneous'' and ''instability.'' One of the prominent examples for instability is the thermal convection instability. Just to remind you, if you heat a fluid layer from below, it takes a certain Rayleigh number to make it unstable. Beyond the onset point you find qualitatively new features. That is called ''spontaneous,'' and this is a bit more than semantics. It's a new qualitative property that appears and it is spontaneous although we have an energy flux through the system. It's a misconception, to call this ''driven'' pointing at the energy flux through it. Of course, the convection would not exist without this energy flux. But what makes it ''spontaneous'' is that without any particular external signal, a new qualitative feature appears. And this is what is called an ''instability'' and ''spontaneous.'' From these considerations the author got a little reassured of what distinction should be made in the field of the magnetosphere. If we have a smooth energy transport into the magnetosphere and suddenly we have this qualitatively new feature (change of B-topology) coming up; then, using this terminology we don't have a choice other than calling this spontaneous or unstable, if you like. If we ''tell'' the system where it should make its neutral line and where it should make its plasmoids, then, it is driven. And this provides a very clear-cut observational distinction. The author emphasizes the difference he sees is a qualitative difference, not only a quantitative one

  4. 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 ...

  5. 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,...

  6. From Vortex Reconnections to Quantum Turbulence

    Science.gov (United States)

    Lipniacki, Tomasz

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

  7. From vortex reconnections to quantum turbulence

    International Nuclear Information System (INIS)

    An alternative approach to quantum turbulence is proposed in order to derive the evolution equation for vortex line-length density. Special attention is paid to reconnections of vortex lines. The summed line-length change ?S of two vortex lines resulting from the reconnection (in the presence of counterflow Vns) can be approximated in the form: ?S=-at1/2+bVns2t3/2, with a>0, b?0, at least until ?S?0. For steady-state turbulence, the average line-length change left angle ?S right angle between reconnections has to be zero. If, for a given value of the counterflow, the line density is smaller than the equilibrium one, the reconnections occur less frequently and left angle ?S right angle becomes positive and the line density grows until the equilibrium is restored. When the line-density is too large, the reconnections are more frequent, the lines shorten between reconnections and the line density gets smaller. The time derivative of the total line density is proportional to the reconnection frequency multiplied by the average line-length change due to a single reconnection. The evolution equation obtained in the proposed approach resembles the alternative Vinen equation. (orig.)

  8. 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.

  9. Theoretical analysis of driven magnetic reconnection experiments

    International Nuclear Information System (INIS)

    In this paper the authors develop a theoretical framework for the Magnetic Reconnection Experiment (MRX) in order to understand the basic physics of the experiment, including the effect of the external driving force, and the difference between co and counterhelicity cases of the experiment. In order to simplify the problem they reduce it to a 1-D resistive MHD model. Also, they define a special class of holonomic boundary conditions under which a unique sequence of global equilibria can be obtained, independent of the rate of reconnection. This enables them to break the whole problem into two parts: a global problem for the ideal region, and a local problem for the resistive reconnection layer. The authors carry out the calculations and obtain the global solution for the ideal region in one particular case of holonomic constraints, the so called 'constant force'' regime, for both the co and counterhelicity cases. After the sequence of equilibria in the ideal region is found, they tackle the problem of the rate of reconnection in the resistive reconnection region. This rate tells how fast they proceed through the sequence of global equilibria but does not affects the sequence itself. Assuming the Sweet-Parker model for the reconnection layer, they calculate the reconnection rate, and demonstrate the difference between the co and counterhelicity cases, as well as the role of the external forces. The authors find their results to be in reasonable agreement with the experiment. Magnetic reconnection is important both in laboratory experiments and in astrophysics

  10. The Onset of Magnetic Reconnection

    Science.gov (United States)

    Daldorff, Lars K. S.; Klimchuk, James A.; van der Holst, Bart

    2015-04-01

    A fundamental question concerning magnetic energy release on the Sun is why the release occurs only after substantial stresses have been built up in the field. If reconnection were to occur readily, the released energy would be insufficient to explain coronal heating, CMEs, flares, jets, spicules, etc. How can we explain this switch-on property? What is the physical nature of the onset conditions? One idea involves the "secondary instability" of current sheets, which switches on when the rotation of the magnetic field across a current sheet reaches a critical angle. Such conditions would occur at the boundaries of flux tubes that become tangled and twisted by turbulent photospheric convection, for example. Other ideas involve a critical thickness for the current sheet. We report here on the preliminary results of our investigation of reconnect onset. Unlike our earlier work on the secondary instability (Dahlburg, Klimchuk, and Antiochos 2005), we treat the coupled chromosphere-corona system. Using the BATS-R-US MHD code, we simulate a single current sheet in a sheared magnetic field that extends from the chromosphere into the corona. Driver motions are applied at the base of the model. The configuration and chromosphere are both idealized, but capture the essential physics of the problem. The advantage of this unique approach is that it resolves the current sheet to the greatest extent possible while maintaining a realistic solar atmosphere. It thus bridges the gap between "reconnection in a box" studies and studies of large-scale systems such as active regions. One question we will address is whether onset conditions are met first in the chromosphere or corona. We will report on the work done on the project.

  11. Simulated Navier-Stokes trefoil reconnection

    CERN Document Server

    Kerr, Robert M

    2015-01-01

    The evolution and self-reconnection of a perturbed trefoil vortex knot is simulated, then compared to recent experimental measurements (Scheeler et al. 2014a). Qualitative comparisons using three-dimensional vorticity isosurfaces and lines, then quantitative comparisons using the helicity. To have a single initial reconnection, as in the experiments, the trefoil is perturbed by 4 weak vortex rings. Initially there is a long period with deformations similar to the experiment during which the energy, continuum helicity and topological self-linking number are all preserved. In the next period, once reconnection has clearly begun, a Reynolds number independent fraction of the initial helicity is dissipated in a finite time. In contrast, the experimental analysis finds that the helicity inferred from the trajectories of hydrogen bubbles is preserved during reconnection. Since vortices reconnect gradually in a classical fluid, it is suggested that the essential difference is in the interpretation of the reconnectio...

  12. Particle acceleration at reconnecting separator current layers

    CERN Document Server

    Threlfall, J; Parnell, C E; Neukirch, T

    2015-01-01

    The aim of this work is to investigate and characterise particle behaviour in a 3D 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 particles are examined in detail for both analytical and numerical separator reconnection models. Differences in acceleration sites are recovered and discussed, together with the dependence of final particle energy ranges upon the dimensions of the models and the stage of the (time-dependent) MHD reconnection event. We discuss the implications of these results for observed magnetic separators in the solar corona.

  13. Experimental measurement of ion distribution function during magnetic reconnection

    Science.gov (United States)

    Swanson, C.; Yamada, M.; Ji, H.; Yoo, J.; Myers, C. E.; Jara-Almonte, J.; Bolgert, P.

    2013-10-01

    The Magnetic Reconnection Experiment (MRX) investigates the process of magnetic reconnection in a laboratory setting. Efficient heating of electrons and ions has been detected and documented during fast reconnection. In order to explore acceleration of charged particles beyond their thermal speeds, seen in space satellite measurements and numerical kinetic simulations, a five-electrode retarding-field energy analyzer was developed to measure the electron and ion distributions in MRX. All electrodes are referenced to the plasma-facing aperture by capacitors to accommodate the dynamically varying plasma potential. An in-line isolation amplifier was placed into the probe shaft to avoid possible picking up electric noise. All electrodes but the collector are electroformed grids of nickel, of which the aperture and rejecter grids have sub-Debye-length spacing. A first version of this probe is designed to measure ions entering the probe aperture perpendicular to local magnetic field. Initial data will be presented and compared with the numerical predictions by kinetic simulations. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the Center for Magnetic Self-Organization (CMSO).

  14. Can amorphization take place in nanoscale interconnects?

    International Nuclear Information System (INIS)

    The trend of miniaturization has highlighted the problems of heat dissipation and electromigration in nanoelectronic device interconnects, but not amorphization. While amorphization is known to be a high pressure and/or temperature phenomenon, we argue that defect density is the key factor, while temperature and pressure are only the means. For nanoscale interconnects carrying modest current density, large vacancy concentrations may be generated without the necessity of high temperature or pressure due to the large fraction of grain boundaries and triple points. To investigate this hypothesis, we performed in situ transmission electron microscope (TEM) experiments on 200 nm thick (80 nm average grain size) aluminum specimens. Electron diffraction patterns indicate partial amorphization at modest current density of about 105 A cm?2, which is too low to trigger electromigration. Since amorphization results in drastic decrease in mechanical ductility as well as electrical and thermal conductivity, further increase in current density to about 7 × 105 A cm?2 resulted in brittle fracture failure. Our molecular dynamics (MD) simulations predict the formation of amorphous regions in response to large mechanical stresses (due to nanoscale grain size) and excess vacancies at the cathode side of the thin films. The findings of this study suggest that amorphization can precede electromigration and thereby play a vital role in the reliability of micro/nanoelectronic devices. (paper)

  15. Physics of Reconnection and MMS Mission

    Science.gov (United States)

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

    2009-01-01

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

  16. Driven reconnection in the earth's magnetotail

    Science.gov (United States)

    Forbes, T. G.

    1991-01-01

    In the standard reconnection model, a low flow speed leads to steady reconnection at a distant-tail x-line, but a high flow speed leads to the formation of a near-earth x-line and the onset of an auroral substorm. This paper discusses recent work which suggests that a pile-up of magnetic flux in the earth's magnetotail will occur whenever reconnection is strongly driven by the solar wind and that the near-earth x-line might result from a flux pile-up at the distant-tail x-line.

  17. Spontaneous reconnection at a separator current layer: 1. Nature of the reconnection

    Science.gov (United States)

    Stevenson, J. E. H.; Parnell, C. E.

    2015-12-01

    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 fields 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-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 most of the separator away from its ends (the nulls) but in an asymmetric manner which changes both spatially and temporally over time. The second phase is much longer and involves slow impulsive bursty reconnection. Again, Ohmic heating dominates over viscous damping. Here the reconnection occurs in small localized bursts at random anywhere along the separator.

  18. 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; Wu, Dan; Meng, Lexuan

    2015-01-01

    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...

  19. Magnetic Reconnection in Extreme Astrophysical Environments

    CERN Document Server

    Uzdensky, Dmitri A

    2011-01-01

    Magnetic reconnection is a basic plasma process of dramatic rearrangement of magnetic topology, often leading to a violent release of magnetic energy. It is important in magnetic fusion and in space and solar physics --- areas that have so far provided the context for most of reconnection research. Importantly, these environments consist just of electrons and ions and the dissipated energy always stays with the plasma. In contrast, in this paper I introduce a new direction of research, motivated by several important problems in high-energy astrophysics --- reconnection in high energy density (HED) radiative plasmas, where radiation pressure and radiative cooling become dominant factors in the pressure and energy balance. I identify the key processes distinguishing HED reconnection: special-relativistic effects; radiative effects (radiative cooling, radiation pressure, and Compton resistivity); and, at the most extreme end, QED effects, including pair creation. I then discuss the main astrophysical application...

  20. Resistive Magnetohydrodynamic Simulations of Relativistic Magnetic Reconnection

    CERN Document Server

    Zenitani, Seiji; 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 (HLL) method is employed. Under a localized resistivity, the system exhibits a fast reconnection jet with an Alfv\\'{e}nic 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.

  1. Forcing continuous reconnection in hybrid simulations

    Energy Technology Data Exchange (ETDEWEB)

    Laitinen, T. V., E-mail: tiera.laitinen@fmi.fi; Janhunen, P. [Finnish Meteorological Institute, PL 503, FI-00101 Helsinki (Finland); Jarvinen, R. [Finnish Meteorological Institute, PL 503, FI-00101 Helsinki (Finland); Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, 3665 Discovery Drive, Boulder, Colorado 80303 (United States); Kallio, E. [School of Electrical Engineering, Aalto University, PL 13000, FI-00076 Aalto, Espoo (Finland); Finnish Meteorological Institute, PL 503, FI-00101 Helsinki (Finland)

    2014-07-15

    We have performed hybrid simulations of driven continuous reconnection with open boundary conditions. Reconnection is started by a collision of two subsonic plasma fronts with opposite magnetic fields, without any specified magnetic field configuration as initial condition. Due to continued forced plasma inflow, a current sheet co-located with a dense and hot plasma sheet develops. The translational symmetry of the current sheet is broken by applying a spatial gradient in the inflow speed. We compare runs with and without localized resistivity: reconnection is initiated in both cases, but localized resistivity stabilizes it and enhances its efficiency. The outflow speed reaches about half of Alfvén speed. We quantify the conversion of magnetic energy to kinetic energy of protons and to Joule heating and show that with localized resistivity, kinetic energy of protons is increased on average five-fold in the reconnection in our simulation case.

  2. Multi-Scale Modeling of Magnetospheric Reconnection.

    Science.gov (United States)

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

    2006-05-01

    One of the major challenges in modeling the magnetospheric magnetic reconnection is to quantify the interaction between large-scale global magnetospheric dynamics and microphysical processes in diffusion regions near reconnection sites. There is still considerable debate as to what degree microphysical processes on kinetic scales affect the global evolution and how important it is to substitute numerical dissipation and/or ad hoc anomalous resistivity by a physically motivated model of dissipation. Comparative studies of magnetic reconnection in small scale geometries demonstrated that MHD simulations that included non-ideal processes in terms of a resistive term ? J did not produce the fast reconnection rates observed in kinetic simulations. For a broad range of physical parameters 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. We utilize the global MHD code BATSRUS and incorporate nongyrotropic effects in diffusion regions in terms of corrections to the induction equation. 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 is updated during the simulations. To clarify the role of nongyrotropic effects in diffusion region on the global magnetospheric dynamic we perform simulations with steady southward IMF driving of the magnetosphere. Ideal MHD simulations with magnetic reconnection supported by numerical resistivity produce steady configuration with almost stationary near-earth neutral line (NENL). Simulations with non-gyrotropic corrections demonstrate dynamic quasi-periodic response to the steady driving condition. The loading/unloading cycle in non-gyrotropic MHD results has a non-stationary reconnection site in the magnetotail, with the retreating during the stretching phase and then a new NENL forming in the resulting thin plasma sheet. We expect that this model will lead to improved representations of space weather event in the magnetosphere.

  3. Redistribution of energetic ions during reconnection events in NSTX

    International Nuclear Information System (INIS)

    Experiments on the spherical torus NSTX show that reconnection events (sawtooth crashes, internal reconnection events et.) can result in strong, by a factor of two, drops of the neutron yield, which are an evidence of losses of energetic ions. In the present work, mechanisms of the energetic ion redistributions during sawtooth crashes are analyzed, and strong drops of the neutral emission in a particular NSTX experiment are explained. It is found that in NSTX shots with a low magnetic field the main mechanisms of the particle redistribution during the crash are the particle resonance with the 1/1 harmonic of the perturbation and the stochastization of the particle motion. The latter is considerably enhanced by the diamagnetic perturbation of the magnetic field strength. The conclusion is drawn that the loss is sensitive to the safety factor profile, the plasma pressure and the particle precession rate, which, in turn, depends on the particle energy and pitch angle, the plasma elongation etc. The NSTX shot 104505, where drops of the neutron yield by a factor of 2 were observed during reconnection events, was selected for detailed analysis. A semi-analytical model of the electromagnetic field evolution during a Kadomtsev-type reconnection, which takes into account the perturbation of the magnetic field strength, is suggested and incorporated into the code GYROXY, which calculates the particle motion without using the guiding-center approximation. It is found that the motion of a considerable fraction of 80-keV ions is stochastic during the reconnection, and this stochasticity can lead to a particle loss. The observed stochasticity results from the overlap of resonance islands, in particular, secondary islands near the separatrix of the 1/1 resonance and islands produced through a nonlinear mechanism. To calculate the post-crash distribution function of energetic ions and the loss of these ions, Monte-Carlo simulations of the particle motion in the evolving magnetic field are carried out. Using this distribution, the change of the neutron reactivity is calculated and compared with the experiment. (author)

  4. Non-thermal Acceleration from Reconnection Shocks

    OpenAIRE

    Blackman, Eric G.; Field, George B.

    1994-01-01

    Reconnection shocks in a magnetically dominated plasma must be compressive. Non-thermal ion acceleration can occur across built-in slow shocks, and across outflow fast shocks when the outflow is supermagnetosonic and the field is line-tied. Electron acceleration may be initiated by injection from the dissipation region. Reconnection and shock acceleration thus cooperate and non-thermal acceleration should be a characteristic feature.

  5. The Diffusion Region in Collisionless Magnetic Reconnection

    Science.gov (United States)

    Hesse, Michael; Neukirch, Thomas; Schindler, Karl; Kuznetsova, Masha; Zenitani, Seiji

    2011-01-01

    A review of present understanding of the dissipation region in magnetic reconnection is presented. The review focuses on results of the thermal inertia-based dissipation mechanism but alternative mechanisms are mentioned as well. For the former process, a combination of analytical theory and numerical modeling is presented. Furthermore, a new relation between the electric field expressions for anti-parallel and guide field reconnection is developed.

  6. 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.

  7. 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...

  8. Test particle acceleration in torsional fan reconnection

    Science.gov (United States)

    Hosseinpour, M.

    2014-12-01

    Magnetic reconnection is understood to be a potential mechanism for particle acceleration in astrophysical and space plasmas, especially in solar flares. Torsional fan reconnection is one of the proposed mechanisms for steady-state three-dimensional (3D) magnetic reconnection. By using the magnetic and electric fields for `torsional fan reconnection', the features of test particle acceleration with input parameters for the solar corona are investigated numerically. We show that torsional fan reconnection is potentially an efficient particle accelerator and a proton can gain up to tens of MeV of kinetic energy within only a few milliseconds. Although the final kinetic energy of the accelerated particle depends on the injection position but there exists only one scenario for the particle's trajectory with different initial positions in which the particle is accelerated on the fan plane. Moreover, adopting either spatially uniform or non-uniform localized plasma resistivity does not much influence the features of trajectory. These results are compared with those of torsional spine reconnection.

  9. 3D Hall MHD Reconnection Dynamics

    Science.gov (United States)

    Huba, J. D.; Rudakov, L.

    2002-05-01

    A 3D Hall MHD simulation code (VooDoo) has recently been developed at the Naval Research Laboratory. We present preliminary results of a fully 3D magnetic reconnection study using this code. The initial configuration of the plasma system is as follows. The ambient, reversed magnetic field is in the x-direction and is proportional to B0 tanh(y/Ly) where Ly is the scale length of the current sheet. Perturbation fields ? Bx and ? By are introduced to initiate the reconnection process. This initial configuration is similar to that used in the 2D GEM reconnection study. However, the perturbation fields are localized in the z-direction. We consider two cases: no guide field (Bz = 0) and a weak guide field (Bz = 0.1B0). We find that the reconnection process is not stationary in the z-direction but propagates in the B x ? n direction consistent with Hall drift physics. Hence, an asymmetric disruption of the current sheet ensues. The flow structure of the plasma in the vicinity of the X-point is complex. We find that the `neutral line' (i.e, along the z-direction) is not an ignorable coordinate and is not periodic in Hall MHD reconnection dynamics; two assumptions that are often made in reconnection studies. \\ Research supported by NASA and ONR

  10. Taking Design Games Seriously

    DEFF Research Database (Denmark)

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

    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......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...

  11. Magnetic reconnection in solar flares

    Science.gov (United States)

    Forbes, T. G.

    1991-01-01

    The magnetic energy stored in the corona is the only plausible source for the energy released during large solar flares. During the last 20 years most theoretical work has concentrated on models which store magnetic energy in the corona in the form of electrical currents, and a major goal of present day research is to understand how these currents are created, and then later dissipated during a flare. Another important goal is to find a flare model which can eject magnetic flux into interplanetary space. Although many flares do not eject magnetic flux, those which do are of special importance for solar-terrestrial relations since the ejected flux can have dramatic effects if it hits the Earth's magnetosphere. Three flare models which have been extensively investigated are the emerging-flux model, the sheared-arcade model, and the magnetic-flux-rope model. All of these models can store and release magnetic energy efficiently provided that rapid magnetic reconnection occurs. However, only the magnetic-flux-rope model appears to provide a plausible mechanism for ejecting magnetic flux into interplanetary space.

  12. Density Enhancements and Voids following Patchy Reconnection

    CERN Document Server

    Guidoni, S E

    2011-01-01

    We show, through a simple patchy reconnection model, that retracting reconnected flux tubes may present elongated regions relatively devoid of plasma, as well as long lasting, dense central hot regions. Reconnection is assumed to happen in a small patch across a Syrovatski\\'i (non-uniform) current sheet (CS) with skewed magnetic fields. The background magnetic pressure has its maximum at the center of the CS plane, and decreases toward the edges of the plane. The reconnection patch creates two V-shaped reconnected tubes that shorten as they retract in opposite directions, due to magnetic tension. One of them moves upward toward the top edge of the CS, and the other one moves downward toward the top of the underlying arcade. Rotational discontinuities (RDs) propagate along the legs of the tubes and generate parallel super-sonic flows that collide at the center of the tube. There, gas dynamics shocks that compress and heat the plasma are launched outwardly. The descending tube moves through the bottom part of t...

  13. Magnetic Reconnection in Different Environments: Similarities and Differences

    Science.gov (United States)

    Hesse, Michael; Aunai, Nicolas; Kuznetsova, Masha; Zenitani, Seiji; Birn, Joachim

    2014-01-01

    Depending on the specific situation, magnetic reconnection may involve symmetric or asymmetric inflow regions. Asymmetric reconnection applies, for example, to reconnection at the Earth's magnetopause, whereas reconnection in the nightside magnetotail tends to involve more symmetric geometries. A combination of review and new results pertaining to magnetic reconnection is being presented. The focus is on three aspects: A basic, MHD-based, analysis of the role magnetic reconnection plays in the transport of energy, followed by an analysis of a kinetic model of time dependent reconnection in a symmetric current sheet, similar to what is typically being encountered in the magnetotail of the Earth. The third element is a review of recent results pertaining to the orientation of the reconnection line in asymmetric geometries, which are typical for the magnetopause of the Earth, as well as likely to occur at other planets.

  14. Turbulent Reconnection Rates from Cluster Observations in the Magneto sheath

    Science.gov (United States)

    Wendel, Deirdre

    2011-01-01

    The role of turbulence in producing fast reconnection rates is an important unresolved question. Scant in situ analyses exist. We apply multiple spacecraft techniques to a case of nonlinear turbulent reconnection in the magnetosheath to test various theoretical results for turbulent reconnection rates. To date, in situ estimates of the contribution of turbulence to reconnection rates have been calculated from an effective electric field derived through linear wave theory. However, estimates of reconnection rates based on fully nonlinear turbulence theories and simulations exist that are amenable to multiple spacecraft analyses. Here we present the linear and nonlinear theories and apply some of the nonlinear rates to Cluster observations of reconnecting, turbulent current sheets in the magnetos heath. We compare the results to the net reconnection rate found from the inflow speed. Ultimately, we intend to test and compare linear and nonlinear estimates of the turbulent contribution to reconnection rates and to measure the relative contributions of turbulence and the Hall effect.

  15. Magnetic Reconnection with Radiative Cooling. I. Optically-Thin Regime

    OpenAIRE

    Uzdensky, Dmitri A.; McKinney, Jonathan C.

    2010-01-01

    Magnetic reconnection, a fundamental plasma process associated with a rapid dissipation of magnetic energy, is believed to power many disruptive phenomena in laboratory plasma devices, the Earth magnetosphere, and the solar corona. Traditional reconnection research, geared towards these rather tenuous environments, has justifiably ignored the effects of radiation on the reconnection process. However, in many reconnecting systems in high-energy astrophysics (e.g., accretion-d...

  16. The role of kinetic effects and parallel electric fields in collisionless reconnection

    Science.gov (United States)

    Egedal, J.; Daughton, W. S.; Le, A.

    2010-12-01

    Magnetic reconnection is a fundamental process in plasmas that converts magnetic energy into particle energy while changing the topology of the magnetic field lines. Aided by spacecraft observations in the Earth’s geotail one of the main accomplishments in reconnection research is the identification of the Hall effect. While fluid models provide important insight into the Hall physics of the ion diffusion region, spacecraft observations show that strong kinetic effects take part in forming the Hall current system. In-situ measurements of the electron distribution function reveal the presence of cold beams directed towards the X-line while energized electrons move away from the reconnection region. We present a new model that can account for these characteristics. The cornerstone of the model is a field aligned acceleration potential ? ? introduced in Ref. [1]. This potential becomes large when the upstream electron beta is small [2]. Electrons accelerated in this potential can reach energies much larger than their ambient temperature. The combination of the direct parallel acceleration by ? ? and pitch angle scattering in the exhaust region generates the characteristic signatures in the electron distribution function observed by spacecraft along the separatrix layers. Our studies are aided and supported by fully kinetic simulations of reconnecting current sheets[3]. [1] Egedal J, Daughton W, Drake J F, Katz N, Le A, "Formation of a localized acceleration potential during magnetic reconnection with a guide field.", (2009) Physics of Plasmas 16, 050701, [2] Le A, Egedal J, Daughton W, Drake J, Fox W, Katz N, "Magnitude of the Hall Fields during magnetic reconnection", (2010) Geophys. Res. Lett. 37, L03106 [3] W. Daughton et al., Phys. Plasmas 13, 072101 (2006)

  17. Role of compressibility on driven magnetic reconnection

    International Nuclear Information System (INIS)

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

  18. Driven reconnection and bursty bulk flows

    Directory of Open Access Journals (Sweden)

    B. P. Pandey

    Full Text Available The energetics of driven magnetic reconnections induced by the deformation of the magnetopause boundary due to the solar wind-magnetosphere interaction are studied. The bursty type reconnection ensues due to the forcing of the magnetopause boundary by the solar wind. For typical plasma parameters in the inner central plasma sheet (ICPS, the magnetic energy release during the reconnection is estimated and it is found that the available free energy is comparable to the observed kinetic energy of typical bursty bulk flows. It implies that the part of the free energy goes into the heating of the ICPS particles, whereas the rest goes into its acceleration. The accelerated particle manifests itself as bursty flows.

    Key words. Magnetospheric physics (magnetotail; storms and substorms

  19. 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

  20. Computer simulation of reconnection in planetary magnetospheres

    Energy Technology Data Exchange (ETDEWEB)

    Birn, J.

    1983-01-01

    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.

  1. Cosmic Ray Acceleration in Magnetic Reconnection Sites

    CERN Document Server

    Pino, Elisabete M de Gouveia Dal; Lazarian, Alex

    2014-01-01

    Cosmic Ray (CR) acceleration still challenges the researchers. Fast particles may be accelerated in astrophysical environments by a variety of processes. Acceleration in magnetic reconnection sites in particular, has lately attracted the attention of researchers not only for its potential importance in the solar system context, but also in other astrophysical environments, like compact stellar sources, AGNs and GRBs, and even in diffusive media like the ISM and the IGM, especially when the environment is magnetically dominated. In this talk we review this process and also present three-dimensional collisional MHD simulations with the injection of thousands of test particles showing from the evolution of their energy spectrum that they can be efficiently accelerated by reconnection through a first-order Fermi process within large scale magnetic current sheets (especially when local turbulence is present which makes reconnection fast and the acceleration layer thicker).

  2. Magnetic Reconnection in a Weakly Ionized Plasma

    CERN Document Server

    Leake, James E; Linton, Mark G

    2013-01-01

    Magnetic reconnection in partially ionized plasmas is a ubiquitous phenomenon spanning the range from laboratory to intergalactic scales, yet it remains poorly understood and relatively little studied. Here, we present results from a self-consistent multi-fluid simulation of magnetic reconnection in a weakly ionized reacting plasma with a particular focus on the parameter regime of the solar chromosphere. The numerical model includes collisional transport, interaction and reactions between the species, and optically thin radiative losses. This model improves upon our previous work in Leake et al. 2012 \\cite{Leake2012} by considering realistic chromospheric transport coefficients, and by solving a generalized Ohm's law that accounts for finite ion-inertia and electron-neutral drag. We find that during the two dimensional reconnection of a Harris current sheet with an initial width larger than the neutral-ion collisional coupling scale, the current sheet thins until its width becomes less than this coupling sca...

  3. Forced reconnection in the Hall limit

    Science.gov (United States)

    Huba, J. D.

    2006-12-01

    We present new numerical results of the dynamics of forced magnetic reconnection in the Hall limit using the NRL Hall MHD code VooDoo. The system is forced by imposing inflow boundary conditions on the plasma density and velocity, and the magnetic field. A magnetic field of opposite polarity is injected from opposite boundaries. The inflow velocity is spatially uniform but the density profile is spatially nonuniform which allows an X-line to develop and magnetic reconnection to proceed. We present simulation results for various inflow conditions in both 2D and 3D geometries. We apply our results to laboratory and space plasma processes. Research supported by ONR and NASA.

  4. Reconnection experiments with 3D magnetic nulls

    Science.gov (United States)

    Vrublevskis, A.; Egedal, J.; Le, A.; Montag, P.

    2011-10-01

    Three-dimensional effects have been crucial in explaining experiments at the Versatile Toroidal Facility (VTF) even in nominal axisymmetric plasmas with a non-vanishing toroidal field. In general, depending on the topological and geometric structure of the magnetic field, a rich collection of magnetic reconnection scenarios is possible in three dimensions. The new adjustable set of coils in VTF allows exploring reconnection in 2D and 3D geometries including configurations with magnetic null points. We present results of a numerical and experimental investigation of magnetic field topologies attainable in VTF. This work was supported by NSF CAREER Award 0844620.

  5. Magnetic Reconnection: Theoretical and Observational Perspectives: Preface

    Science.gov (United States)

    Lewis, W. S.; Antiochos, S. K,; Drake, J. F.

    2011-01-01

    Magnetic reconnection is a fundamental plasma-physical process by which energy stored in a magnetic field is converted, often explosively, into heat and the kinetic energy of the charged particles that constitute the plasma. It occurs in a variety of astrophysical settings, ranging from the solar corona to pulsar magnetospheres and winds, as well as in laboratory fusion experiments, where it is responsible for sawtooth crashes. First proposed by R.G. Giovanelli in the late I 940s as the mechanism responsible for solar flares, magnetic reconnection was invoked at the beginning of the space age to explain not just solar flares but also the transfer of energy, mass, and momentum from the solar wind to Earth's magnetosphere and the subsequent storage and release of the transferred energy in the magnetotai\\. During the half century or so that has followed the seminal theoretical works by J.W. Dungey, P.A. Sweet, E.N. Parker, and H.E. Petschek, in-situ measurements by Earth-orbiting satellites and remote-sensing observations of the solar corona have provided a growing body of evidence for the occurrence of reconnection at the Sun, in the solar wind, and in the near-Earth space environment. The last thirty years have also seen the development of laboratory reconnection experiments at a number of institutions. In parallel with the efforts of experimentalists in both space and laboratory plasma physics, theorists have investigated, analytically and with the help of increasingly powerful MHD, hybrid, and kinetic numerical simulations, the structure of the diffusion region, the factors controlling the rate, onset, and cessation of reconnection, and the detailed physics that enables the demagnetization of the ions and electrons and the topological reconfiguration of the magnetic field. Moreover, the scope of theoretical reconnection studies has been extended well beyond solar system and laboratory plasmas to include more exotic astrophysical plasma systems whose strong (10(exp 14)-10(exp 15) G) magnetic fields require that models of reconnection in these systems incorporate quantum electrodynamical, special relativistic, and radiative effects. The papers collected in this topical issue of Space Science Reviews cover different aspects of recent theoretical and observational work on magnetic reconnection in solar and space physics, astrophysics, and laboratory plasma physics. They derive from presentations given at a workshop on magnetic reconnection held in the Yosemite National Park, February 8-12,2010. The intent of the workshop was to stimulate, through a combination of tutorial talks, shorter focused talks, and extensive informal discussions, an interdisciplinary dialogue among members of the different research communities working on the problem of magnetic reconnection. One of the motivating considerations for holding the workshop was its relevance to NASA's Magnetospheric Multiscale (MMS) mission, scheduled for launch in 2014. The four identically instrumented MMS spacecraft are designed to study reconnect ion in Earth's magnetosphere and, specifically, to probe the electron diffusion region in order to determine the microphysical processes that enable the change in the topology of the magnetic field. Building on the achievements of the multi spacecraft Cluster and THEMIS missions, MMS will use the magnetosphere as an astrophysical plasma laboratory in which to test, through in-situ measurement of the plasma, energetic particles, and electric and magnetic fields, various models and theories that have emerged during the past twenty years, a period of extraordinarily productive theoretical and observational work.

  6. 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.

  7. Percussion Discussion: Using Drums To Reconnect Youth.

    Science.gov (United States)

    Wilbur, John; Harris, Tom

    1998-01-01

    Reports on a therapeutic program for juvenile offenders that uses drum playing and drum building to provide alternatives for youth activities. Drums play five important roles for youth: creating a sense of community, reconnecting with history and heritage, promoting healing, educating, and celebrating victories or rites of passage. Provides…

  8. Equations of State in Collisionless Magnetic Reconnection

    Science.gov (United States)

    Le, A.; Egedal, J.; Katz, N. K.; Vrublevskis, A.; Fox, W. R.

    2009-12-01

    Wind and Cluster spacecraft measurements of reconnecting current sheets in the Earth`s magnetosphere show strong electron temperature anisotropy. This anisotropy is accounted for in a solution of the Vlasov equation recently derived for general reconnection geometries with magnetized electrons in the limit of fast transit time [1]. A necessary ingredient is an ion-scale parallel electric field, which maintains quasi-neutrality by regulating the electron density, traps a large fraction of thermal electrons, and heats electrons in the parallel direction. Based on the expression for the electron phase space density, equations of state provide a fluid closure that relates the parallel and perpendicular pressures to the density and magnetic field strength [2]. The resulting fluid model agrees well with fully kinetic simulations of guide-field reconnection, where the parallel electron temperature becomes several times greater than the perpendicular temperature. In addition, the equations of state relate features of the electron diffusion region that develop during anti-parallel reconnection to the upstream electron beta. They impose strong constraints on the electron Hall currents and magnetic fields. The equations of state are suitable for implementation in two-fluid or hybrid codes. Such codes could retain important electron kinetic effects in numerical models of large-scale collisionless plasmas, which lie beyond current computational limits in kinetic simulation. [1] J. Egedal, W. Fox, N. Katz, et al., J. Geophys. Res. 113, A12207 (2008). [2] A. Le, J. Egedal, et al., Phys. Rev. Lett. 102, 085001 (2009).

  9. Color-reconnection in Z ? 3 jets

    International Nuclear Information System (INIS)

    The electric charge distribution of gluon jets with a rapidity gap is sensitive to possible effects of color reordering in the final quark-gluon cascade. High statistics data from the ALEPH experiment at LEP-1 are used to test the predictions of different color reconnection models. (author)

  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. Study of the effects of guide field on Hall reconnection

    International Nuclear Information System (INIS)

    The results from guide field studies on the Magnetic Reconnection Experiment (MRX) are compared with results from Hall magnetohydrodynamic (HMHD) reconnection simulation with guide field. The quadrupole field, a signature of two-fluid reconnection at zero guide field, is modified by the presence of a finite guide field in a manner consistent with HMHD simulation. The modified Hall current profile contains reduced electron flows in the reconnection plane, which quantitatively explains the observed reduction of the reconnection rate. The present results are consistent with the hypothesis that the local reconnection dynamics is dominated by Hall effects in the collisionless regime of the MRX plasmas. While very good agreement is seen between experiment and simulations, we note that an important global feature of the experiments, a compression of the guide field by the reconnecting plasma, is not represented in the simulations

  12. Place Branding

    DEFF Research Database (Denmark)

    Medway, Dominic; Swanson, Kathryn; Neirotti, Lisa Delpy; Pasquinelli, Cecilia; Zenker, Sebastian

    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....

  13. Children's Places

    DEFF Research Database (Denmark)

    2003-01-01

    Using a cross-cultural approach the book investigates children's places in different societies. "Children's Places" examines the ways in which children and adults, from their different vantage-points in society, negotiate proper places of children in both social and spatial terms. It looks at some of the recognised constructions of children, as well as examining contexts for them, from schools and kindergartens to inner cities and war-zones. The result gives insight into the notions of inclusion...

  14. 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.

  15. The Relation Between Reconnected Flux, the Parallel Electric Field, and the Reconnection Rate in a Three-Dimensional Kinetic Simulation of Magnetic Reconnection

    Science.gov (United States)

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

    2013-01-01

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

  16. Designed Places

    DEFF Research Database (Denmark)

    Stender, Marie

    stake, when we design the places we inhabit. In the process of design we engage with our material surroundings and seek to shape them according to our ideals. However, the market forces also play a key role in shaping these places, and these forces cannot be controlled. Rather, they are dealt with much...... 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 as...... authentic the friction that derives from the place’s history or topography. Yet, even such friction is designed. One housing complex is thus designed and branded as ‘a modern mountain village’, though situated on flat and greenfield land. Its shape grows from market forces, rather than from topography, and...

  17. 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 reconnection research. Furthermore, much progress was made in understanding the reconnection process itself

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

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, S.C.

    2000-01-28

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

  19. 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...... an example due to Denmark’s favourable drivers of making it a test market for proving the concept of a suitable business model and concept for the future global EV industry....

  20. A MAGNETIC RECONNECTION MECHANISM FOR THE GENERATION OF ANOMALOUS COSMIC RAYS

    International Nuclear Information System (INIS)

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

  1. 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

  2. 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.

  3. PARTIAL SLINGSHOT RECONNECTION BETWEEN TWO FILAMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yunchun; Hong, Junchao; Yang, Jiayan; Bi, Yi; Zheng, Ruisheng; Yang, Bo; Li, Haidong; Yang, Dan, E-mail: jyc@ynao.ac.cn [National Astronomical Observatory/Yunnan Astronomical Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China)

    2013-02-10

    We present a rare observation of an interaction between two filaments around AR 11358 and AR 11361 on 2011 December 3 that is strongly suggestive of the occurrence of slingshot reconnection. A small elbow-shaped active-region filament (F12) underwent a failed eruption that brought it into contact with a nearby larger, thicker filament (F34). Accompanied by the appearance of complicated internal structures below the erupting F12, its two legs separated away from each other and then connected into F34. This process led the filaments to change their connectivity to form two newly linked filaments, and one of them showed a clear inverse {gamma}-shape. However, the alteration in the filament connectivity was imperfect since F34 is discernible after the eruption. These observations can be interpreted as a partial slingshot reconnection between two filaments that had unequal axial magnetic flux.

  4. 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.

  5. Magnetic reconnection in the near Venusian magnetotail.

    Science.gov (United States)

    Zhang, T L; Lu, Q M; Baumjohann, W; Russell, C T; Fedorov, A; Barabash, S; Coates, A J; Du, A M; Cao, J B; Nakamura, R; Teh, W L; Wang, R S; Dou, X K; Wang, S; Glassmeier, K H; Auster, H U; Balikhin, M

    2012-05-01

    Observations with the Venus Express magnetometer and low-energy particle detector revealed magnetic field and plasma behavior in the near-Venus wake that is symptomatic of magnetic reconnection, a process that occurs in Earth's magnetotail but is not expected in the magnetotail of a nonmagnetized planet such as Venus. On 15 May 2006, the plasma flow in this region was toward the planet, and the magnetic field component transverse to the flow was reversed. Magnetic reconnection is a plasma process that changes the topology of the magnetic field and results in energy exchange between the magnetic field and the plasma. Thus, the energetics of the Venus magnetotail resembles that of the terrestrial tail, where energy is stored and later released from the magnetic field to the plasma. PMID:22491094

  6. Intermittent magnetic reconnection in TS-3 merging experiment

    International Nuclear Information System (INIS)

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

  7. Shocks and Thermal Conduction Fronts in Retracting Reconnected Flux Tubes

    CERN Document Server

    Guidoni, Silvina

    2010-01-01

    We present a model for plasma heating produced by time-dependent, spatially localized reconnection within a flare current sheet separating skewed magnetic fields. The reconnection creates flux tubes of new connectivity which subsequently retract at Alfv\\'enic speeds from the reconnection site. Heating occurs in gas-dynamic shocks which develop inside these tubes. Here we present generalized thin flux tube equations for the dynamics of reconnected flux tubes, including pressure-driven parallel dynamics as well as temperature dependent, anisotropic viscosity and thermal conductivity. The evolution of tubes embedded in a uniform, skewed magnetic field, following reconnection in a patch, is studied through numerical solutions of these equations, for solar coronal conditions. Even though viscosity and thermal conductivity are negligible in the quiet solar corona, the strong gas-dynamic shocks generated by compressing plasma inside reconnected flux tubes generate large velocity and temperature gradients along the t...

  8. Theory of magnetic reconnection in solar and astrophysical plasmas

    CERN Document Server

    Pontin, D I

    2012-01-01

    Magnetic reconnection is a fundamental process in a plasma that facilitates the release of energy stored in the magnetic field by permitting a change in the magnetic topology. In this article we present a review of the current state of understanding of magnetic reconnection. We discuss theoretical results regarding the formation of current sheets in complex 3D magnetic fields, and describe the fundamental differences between reconnection in two and three dimensions. We go on to outline recent developments in modelling of reconnection with kinetic theory, as well as in the MHD framework where a number of new 3D reconnection regimes have been identified. We discuss evidence from observations and simulations of solar system plasmas that support this theory, and summarise some prominent locations in which this new reconnection theory is relevant in astrophysical plasmas.

  9. Magnetic Reconnection with Radiative Cooling. I. Optically-Thin Regime

    CERN Document Server

    Uzdensky, Dmitri A

    2010-01-01

    Magnetic reconnection, a fundamental plasma process associated with a rapid dissipation of magnetic energy, is believed to power many disruptive phenomena in laboratory plasma devices, the Earth magnetosphere, and the solar corona. Traditional reconnection research, geared towards these rather tenuous environments, has justifiably ignored the effects of radiation on the reconnection process. However, in many reconnecting systems in high-energy astrophysics (e.g., accretion-disk coronae, relativistic jets, magnetar flares) and, potentially, in powerful laser plasma and z-pinch experiments, the energy density is so high that radiation, in particular radiative cooling, may start to play an important role. This observation motivates the development of a theory of high-energy-density radiative magnetic reconnection. As a first step towards this goal, we present in this paper a simple Sweet--Parker-like theory of non-relativistic resistive-MHD reconnection with strong radiative cooling. First, we show how, in the a...

  10. Fermi Acceleration in Magnetic Reconnection Sites

    Science.gov (United States)

    de Gouveia Dal Pino, E. M.; Kowal, G.; Lazarian, A.

    2014-09-01

    The mechanisms that accelerate cosmic relativistic particles are not fully understood yet. A variety of processes has been investigated and the acceleration in magnetic reconnection sites has lately gained increasing attention from researchers not only for its potential importance in the solar system, but also beyond it, in astrophysical environments like compact stellar sources, AGNs and GRBs, and even in diffusive magnetized media as the interstellar medium (ISM) and the intergalactic medium (IGM). In this talk we review this process and, supported by three-dimensional MHD simulations with the injection of thousands of test particles, we show that they can be efficiently accelerated by magnetic reconnection through a first-order Fermi process within large scale magnetic current sheets, even in a collisional fluid (contrary to what was previously believed), especially when local turbulence is present which makes reconnection fast, the acceleration layer thicker and the overall process naturally three-dimensional. Tests of particle acceleration in pure MHD turbulent environments (i.e., without the presence of large scale current sheets), on the other hand, indicate that the dominant acceleration process is a second-order Fermi.

  11. Self-Feeding Turbulent Magnetic Reconnection on Macroscopic Scales

    OpenAIRE

    Lapenta, Giovanni

    2008-01-01

    Within a MHD approach we find magnetic reconnection to progress in two entirely different ways. The first is well-known: the laminar Sweet-Parker process. But a second, completely different and chaotic reconnection process is possible. This regime has properties of immediate practical relevance: i) it is much faster, developing on scales of the order of the Alfv\\'en time, and ii) the areas of reconnection become distributed chaotically over a macroscopic region. The onset of...

  12. Dynamic Response of Magnetic Reconnection Due to Current Sheet Variability

    Science.gov (United States)

    George, D. E.; Jahn, J. M.; Burch, J. L.; Hesse, M.; Pollock, C. J.

    2014-12-01

    Magnetic reconnection is a process which regulates the interaction between regions of magnetized plasma. While many factors have an impact on the evolution of this process, there still remains a lack of understanding of the key behaviors involved in the triggering of fast reconnection. Despite an abundance of in-situ measurements, indicating the high degree of variability in the thickness, density and composition along the current sheet, no simulation studies exist which account for such current sheet variations. 2D and 3D simulations have a periodic boundary in the dimension along the current sheet and so tend to neglect these variations in the current sheet originating external to the modeled reconnection region. Here we focus on the effects on reconnection due to the variability in the thickness and density of the current sheet. Using 2.5D kinetic simulations of 2-species plasma, we isolate and explore the dynamic effects on reconnection associated with variations in the current sheet originating externally to the reconnection region. While periodic boundary conditions are still used, in the direction along the current sheet, a step-change perturbation in thickness or density of the current sheet is introduced once a stable reconnection rate is reached. The dynamic response of the overall system, after introducing the perturbation, is then evaluated, with a focus on the reconnection rate. When the reconnection rate is slowed significantly over time, loading of the inflow region occurs (a build-up of plasma and magnetic energy/pressure. This state is indicated by an asymptotic behavior in the reconnection rate over time. If a sudden variation in the current sheet is introduced under these conditions, a resultant triggering of fast reconnection may occur, which could lead to an episode of fast reconnection, saw-tooth-crash condition or even act as a trigger for sub-storms.

  13. Reconnection and merging of positive streamers in air

    OpenAIRE

    Nijdam, S; Geurts, CGC; Veldhuizen, EM (Eddie) van; Ebert, UM (Ute)

    2008-01-01

    Pictures show that streamer or sprite discharge channels emerging from the same electrode sometimes seem to reconnect or merge though their heads carry electric charge of the same polarity; one might therefore suspect that reconnections are an artifact of the two-dimensional projection in the pictures. Here we use stereo-photography to investigate the full three-dimensional structure of such events. We analyze reconnection, possibly an electrostatic effect in which a late th...

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

    International Nuclear Information System (INIS)

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

  15. 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.

  16. Taking Medication

    Medline Plus

    Full Text Available ... NETWORK AADE 7 System My Learning My Purchases Open Invoices ... help get you to the right place: Did you click to the link from an email or other source outside of the AADE site? Please try our ...

  17. Places Connected:

    DEFF Research Database (Denmark)

    Hansen, Annette Skovsted

    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......This paper argues that development assistance contributed to the globalization of the 20th century by financing truly global networks of people. By focusing on the networks financed by development assistance bound by the national histories of Denmark and Japan, I illustrate how the people who...... influence the dynamics of networks. The development workers, fellows, and international public servants financed by development assistance exemplify the function and quality of weak links, when an NGO employee from Bangladesh spend three months in Denmark and meet What is the impact of these temporary...

  18. 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 & ...

  19. High power heating of magnetic reconnection in merging tokamak experiments

    International Nuclear Information System (INIS)

    Significant ion/electron heating of magnetic reconnection up to 1.2?keV was documented in two spherical tokamak plasma merging experiment on MAST with the significantly large Reynolds number R?105. Measured 1D/2D contours of ion and electron temperatures reveal clearly energy-conversion mechanisms of magnetic reconnection: huge outflow heating of ions in the downstream and localized heating of electrons at the X-point. Ions are accelerated up to the order of poloidal Alfven speed in the reconnection outflow region and are thermalized by fast shock-like density pileups formed in the downstreams, in agreement with recent solar satellite observations and PIC simulation results. The magnetic reconnection efficiently converts the reconnecting (poloidal) magnetic energy mostly into ion thermal energy through the outflow, causing the reconnection heating energy proportional to square of the reconnecting (poloidal) magnetic field Brec2?????Bp2. The guide toroidal field Bt does not affect the bulk heating of ions and electrons, probably because the reconnection/outflow speeds are determined mostly by the external driven inflow by the help of another fast reconnection mechanism: intermittent sheet ejection. The localized electron heating at the X-point increases sharply with the guide toroidal field Bt, probably because the toroidal field increases electron confinement and acceleration length along the X-line. 2D measurements of magnetic field and temperatures in the TS-3 tokamak merging experiment also reveal the detailed reconnection heating mechanisms mentioned above. The high-power heating of tokamak merging is useful not only for laboratory study of reconnection but also for economical startup and heating of tokamak plasmas. The MAST/TS-3 tokamak merging with Bp?>?0.4?T will enables us to heat the plasma to the alpha heating regime: Ti?>?5?keV without using any additional heating facility

  20. High power heating of magnetic reconnection in merging tokamak experimentsa)

    Science.gov (United States)

    Ono, Y.; Tanabe, H.; Yamada, T.; Gi, K.; Watanabe, T.; , T., Ii; Gryaznevich, M.; Scannell, R.; Conway, N.; Crowley, B.; Michael, C.

    2015-05-01

    Significant ion/electron heating of magnetic reconnection up to 1.2 keV was documented in two spherical tokamak plasma merging experiment on MAST with the significantly large Reynolds number R˜105. Measured 1D/2D contours of ion and electron temperatures reveal clearly energy-conversion mechanisms of magnetic reconnection: huge outflow heating of ions in the downstream and localized heating of electrons at the X-point. Ions are accelerated up to the order of poloidal Alfven speed in the reconnection outflow region and are thermalized by fast shock-like density pileups formed in the downstreams, in agreement with recent solar satellite observations and PIC simulation results. The magnetic reconnection efficiently converts the reconnecting (poloidal) magnetic energy mostly into ion thermal energy through the outflow, causing the reconnection heating energy proportional to square of the reconnecting (poloidal) magnetic field Brec2 ˜ Bp2. The guide toroidal field Bt does not affect the bulk heating of ions and electrons, probably because the reconnection/outflow speeds are determined mostly by the external driven inflow by the help of another fast reconnection mechanism: intermittent sheet ejection. The localized electron heating at the X-point increases sharply with the guide toroidal field Bt, probably because the toroidal field increases electron confinement and acceleration length along the X-line. 2D measurements of magnetic field and temperatures in the TS-3 tokamak merging experiment also reveal the detailed reconnection heating mechanisms mentioned above. The high-power heating of tokamak merging is useful not only for laboratory study of reconnection but also for economical startup and heating of tokamak plasmas. The MAST/TS-3 tokamak merging with Bp > 0.4 T will enables us to heat the plasma to the alpha heating regime: Ti > 5 keV without using any additional heating facility.

  1. Taking Medication

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    Full Text Available ... App Tip Sheets and Handouts AADE7 Self-Care Behaviors Healthy Eating Being Active Monitoring Taking Medication Problem ... Membership MY AADE NETWORK AADE 7 System My Learning My Purchases Open Invoices Home / error-404 404 ...

  2. Taking Medication

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    Full Text Available ... Tip Sheets and Handouts AADE7 Self-Care Behaviors Healthy Eating Being Active Monitoring Taking Medication Problem Solving Reducing Risks Healthy Coping Education & Career Webinars Upcoming Webinars Recorded Webinars ...

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    Full Text Available ... Reviewed Diabetes Prevention Program About DPP DPP Newsletters Lifestyle Coach Training DPP at Annual Meeting National Diabetes ... Tip Sheets and Handouts AADE7 Self-Care Behaviors Healthy Eating Being Active Monitoring Taking Medication Problem Solving ...

  4. Taking Medication

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    Full Text Available ... Handouts AADE7 Self-Care Behaviors Healthy Eating Being Active Monitoring Taking Medication Problem Solving Reducing Risks Healthy ... IL 60606 800.338.3633 Contact Us Privacy Policy | Terms of Use | Social Media Policy | Contact AADE | ...

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    Full Text Available ... Tracker App Tip Sheets and Handouts AADE7 Self-Care Behaviors Healthy Eating Being Active Monitoring Taking Medication ... Legislative Action Center Federal Legislation State Legislation Affordable Care Act Information Advocacy Tools and Resources Cart Search ...

  6. Taking Medication

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    Full Text Available ... Tracker App Tip Sheets and Handouts AADE7 Self-Care Behaviors Healthy Eating Being Active Monitoring Taking Medication ... Legislative Action Center Federal Legislation State Legislation Affordable Care Act Information Advocacy Tools and Resources Affordable Care ...

  7. 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 ...

  8. Places disponibles*/Places available **

    CERN Multimedia

    2003-01-01

    Des places sont disponibles dans les cours suivants : Places are available in the following course : Java 2 Enterprise Edition - Part 2 : Enterprise JavaBeans : 20 - 22.1.03 (3 days) Introduction to PVSS : 27.1.03 (Afternoon) free course but registration necessary Basic PVSS : 28 - 30.1.03 (3 days) MAGNE-03 - Magnétisme pour l'électrotechnique : 28 - 30.1.03 (3 jours) MAGNE-03 - Magnetism for Technical Electronics : 11 - 13.2.03 (3 days) AutoCAD 2002 - niveau 1 : 24, 25.2 et 3, 4.3.03 (4 jours) AutoCAD 2002 - niveau 2 : 10 & 11.3.03 (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) * 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. Si vous désirez ...

  9. 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...

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

    Energy Technology Data Exchange (ETDEWEB)

    Wendel, D. E.; Olson, D. K.; Hesse, M.; Kuznetsova, M.; Adrian, M. L. [NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Aunai, N. [Institute for Research in Astrophysics and Planetology, University Paul Sabatier, Toulouse (France); Karimabadi, H. [SciberQuest, Inc., Del Mar, California 92014 (United States); Department of Computer and Electrical Engineering, University of California, San Diego, La Jolla, California 92093 (United States); Daughton, W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2013-12-15

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

  11. Place Branding

    DEFF Research Database (Denmark)

    Medway, Dominic; Swanson, Kathryn; Neirotti, Lisa Delpy; Pasquinelli, Cecilia; Zenker, Sebastian

    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-style debate with two opposing teams of two persons – one team supporting and one team opposing the motion. The opening speaker of each team had 10 minutes to put their case across, and the closing speaker ha...

  12. 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.

  13. Ion Temperature Anisotropy across Reconnection Exhaust Jets

    Science.gov (United States)

    Hietala, H.; Drake, J. F.; Phan, T. D.; Eastwood, J. P.; McFadden, J. P.

    2014-12-01

    Magnetic reconnection redistributes energy by releasing magnetic energy into plasma kinetic energy - high speed bulk flows, heating, and particle acceleration. In the magnetotail, most of the released energy appears to go into ion heating. However, previous observations and simulations show that this heating is anisotropic with the plasma temperature parallel to the magnetic field generally increasing more than the perpendicular temperature. Simulations and theory indicate that this temperature anisotropy can balance part of the magnetic tension force that accelerates the jet, and may even exceed it leading to firehose instability.Here we report the results of a new study of ion temperature anisotropy in reconnection exhausts generated by anti-parallel reconnection. We have examined ARTEMIS dual-spacecraft observations of long-duration magnetotail exhausts at lunar distances in conjunction with Particle-In-Cell simulations. In particular, we have studied spatial variations in the ion temperature anisotropy across the outflows far away (>100 ion inertial lengths) from the X-line. A consistent pattern is found in both the spacecraft data and the simulations: whilst the total temperature profile across the exhaust is flat, near the exhaust boundaries the parallel temperature dominates. A consequence of this is that firehose threshold is greatly exceeded in a significant fraction of the exhaust. In contrast, the perpendicular temperature dominates at the neutral plane (|BX| < 0.1 B0), indicating that, despite the turbulence and the large distance to the X-line, particles undergo Speiser-like motion (rather than isotropization by scattering). We also analyse the characteristics of the particle distributions leading to these anisotropies at different distances from the mid-plane.

  14. A 10-stage reconnection demonstration launcher

    International Nuclear Information System (INIS)

    This paper reports on a small-scale, 10-stage cylindrical reconnection launcher that has been designed, fabricated, and tested. Ten-gram projectiles are accelerated from rest to 317 m/s through the 0.44 m launcher assembly with a projectile kinetic energy to capacitor stored energy efficiency of 9%. Comparison of test results and computer code predictions are presented. Results of these studies have substantiated launcher scaling at small size and have provided a useful test bed for launcher components and diagnostics

  15. Lepton Acceleration by Relativistic Collisionless Magnetic Reconnection

    OpenAIRE

    Larrabee, D. A.; R. V. E. Lovelace(Department of Astronomy, Cornell University, Ithaca, NY); Romanova, M. M.

    2002-01-01

    We have calculated self-consistent equilibria of a collisionless relativistic electron-positron gas in the vicinity of a magnetic $X-$point. For the considered conditions, pertinent to extra-galactic jets, we find that leptons are accelerated up to Lorentz factors $\\Gamma_0 = \\kappa e B_0L {\\cal E}^2 /mc^2 \\gg 1$, where $B_0$ is the typical magnetic field strength, ${\\cal E}\\equiv E_0/B_0$, with $E_0$ the reconnection electric field, $L$ is the length scale of the magnetic field, and $\\kappa ...

  16. 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...

  17. 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...

  18. 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...

  19. 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) 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...

  20. Places available**

    CERN Document Server

    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...

  1. 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...

  2. 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) 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...

  3. Places available**

    CERN Document Server

    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...

  4. 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...

  5. 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...

  6. 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...

  7. 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 (...

  8. 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...

  9. 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 & ...

  10. 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...

  11. Family jigsaws : how intergenerational relationships between grandparents, parents, and children impact on the learning that takes place between the generations, and how this contributes to the child's learning experiences at home and at school.

    OpenAIRE

    Ruby, Mahera

    2015-01-01

    This study investigated the intergenerational relationships between grandparents, parents and children from Bangladeshi British families in East London, and the impact these relationships had on the learning that took place between the generations. The study also investigated how this contributed to the child's learning experiences at home and at school. I collected data within an ethnographic framework using participant observation, interviews, questionnaires and video recordings. Through an...

  12. Enhanced magnetic reconnection in the presence of pressure gradients

    Energy Technology Data Exchange (ETDEWEB)

    Pueschel, M. J.; Terry, P. W. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Told, D.; Jenko, F. [Max-Planck-Institut für Plasmaphysik, D-85748 Garching (Germany); Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States)

    2015-06-15

    Magnetic reconnection in the presence of background pressure gradients is studied, with special attention to parallel (compressional) magnetic fluctuations. A process is reported that reconnects fields through coupling of drift-wave-type instabilities with current sheets. Its time scale is set not by the reconnecting field but by inhomogeneities of the background density or temperature. The observed features can be attributed to a pressure-gradient-driven linear instability which interacts with the reconnecting system but is fundamentally different from microtearing. In particular, this mode relies on parallel magnetic fluctuations and the associated drift. For turbulent reconnection, similar or even stronger enhancements are reported. In the solar corona, this yields a critical pressure gradient scale length of about 200?km below which this new process becomes dominant over the tearing instability.

  13. 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...

  14. 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...

  15. 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.

  16. Enhanced magnetic reconnection in the presence of pressure gradients

    International Nuclear Information System (INIS)

    Magnetic reconnection in the presence of background pressure gradients is studied, with special attention to parallel (compressional) magnetic fluctuations. A process is reported that reconnects fields through coupling of drift-wave-type instabilities with current sheets. Its time scale is set not by the reconnecting field but by inhomogeneities of the background density or temperature. The observed features can be attributed to a pressure-gradient-driven linear instability which interacts with the reconnecting system but is fundamentally different from microtearing. In particular, this mode relies on parallel magnetic fluctuations and the associated drift. For turbulent reconnection, similar or even stronger enhancements are reported. In the solar corona, this yields a critical pressure gradient scale length of about 200?km below which this new process becomes dominant over the tearing instability

  17. 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.

  18. Fluid vs. kinetic magnetic reconnection with strong guide-fields

    CERN Document Server

    Stanier, A; Chacon, L; Daughton, W

    2015-01-01

    The fast rates of magnetic reconnection found in both nature and experiments are important to understand theoretically. Recently, it was demonstrated that two-fluid magnetic reconnection remains fast in the strong guide field regime, regardless of the presence of fast-dispersive waves. This conclusion is in agreement with recent results from kinetic simulations, and is in contradiction to the findings in an earlier two-fluid study, where it was suggested that fast-dispersive waves are necessary for fast reconnection. In this paper, we give a more detailed derivation of the analytic model presented in a recent letter, and present additional simulation results to support the conclusions that the magnetic reconnection rate in this regime is independent of both collisional dissipation and system-size. In particular, we present a detailed comparison between fluid and kinetic simulations, finding good agreement in both the reconnection rate and overall length of the current layer. Finally, we revisit the earlier tw...

  19. Interests, limitations and role of external radiotherapy when taking into care the brain metastatic disease; Interets, limites et place de la radiotherapie externe dans la prise en charge de la maladie metastatique cerebrale

    Energy Technology Data Exchange (ETDEWEB)

    Fabre, J. [Centre Henri-Becquerel, 76 - Rouen (France)

    2010-10-15

    As the prognostic is very severe in case of brain metastases, pan-encephalic irradiation remains the reference treatment which enables a quick, non invasive and efficient taking into care of symptoms with a low morbidity. Surgical exeresis and focused radiotherapy techniques have more specific applications, and enable, in association with pan-encephalic irradiation, increased local control and survival rates in case of a unique metastasis. The author outlines the different risks to be limited. Short communication

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

    Science.gov (United States)

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

    2015-10-01

    Magnetic reconnection is a fundamental process throughout the solar system, significantly shaping and modulating the magnetospheres of the magnetized planets. Within planetary magnetotails reconnection can be responsible for energizing particles and potentially changing the total flux and mass contained within the magnetosphere. The Kronian magnetosphere is thought to be a middle ground between the rotationally dominated Jovian magnetosphere and the solar wind driven terrestrial magnetosphere. However, previous studies have not been able to find a statistical reconnection x-line, as has been possible at both Jupiter and Earth. Additionally the standard picture of magnetotail reconnection at Saturn, developed by Cowley et al. [2004], suggests a potential asymmetry between the dawn and dusk flanks, caused by different reconnection processes dominating. This work centers on the development of an algorithm designed to find reconnection related events in spacecraft magnetometer data, aiming to reduce the bias that manual searches could inherently introduce, thereby ensuring the validity of any statistical analysis. The algorithm primarily identifies the reconnection related events from deflections in the north-south component of the magnetic field, allowing an almost uninterrupted in-situ search (when the spacecraft is situated within the magnetotail). The new catalogue of candidate reconnection events, produced by the algorithm, enables a more complete statistical view of reconnection in the Kronian magnetotail. Well-studied data encompassing the deep magnetotail and dawn flank (particularly from orbits in 2006) were used to train the algorithm and develop reasonable criteria. The algorithm was then applied to data encompassing the dusk flank (including orbits from 2009, for which plasma data have been examined by Thomsen et al. [2014]). This combination enables a robust, and global, comparison of reconnection rates, signatures and properties in the Kronian magnetotail.

  1. Taking Medication

    Medline Plus

    Full Text Available ... 404 Error Whoops! That page doesn't seem to exist. The page you are trying to view may have been removed, changed, or is ... t worry, w e’ll help get you to the right place: Did you click to the ...

  2. Taking Medication

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    Full Text Available ... My Purchases Open Invoices Home / error-404 404 Error Whoops! That page doesn't seem to exist. The page you are trying to view may have been removed, changed, or is temporarily unavailable, but don’t worry, w e’ll help get you to the right place: Did you click to the link from an ...

  3. Taking Medication

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    Full Text Available ... Patient Resources How a Diabetes Educator Can Help You Maria Ibarra Tony Essex Pat Conroy Been Referred. What's Next? Find a Diabetes Educator Diabetes Goal Tracker App Tip Sheets and Handouts AADE7 Self-Care Behaviors Healthy Eating Being Active Monitoring Taking Medication Problem Solving ...

  4. Double Take

    Science.gov (United States)

    Educational Leadership, 2011

    2011-01-01

    This paper begins by discussing the results of two studies recently conducted in Australia. According to the two studies, taking a gap year between high school and college may help students complete a degree once they return to school. The gap year can involve such activities as travel, service learning, or work. Then, the paper presents links to…

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  20. 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 ?0 = 2?h/e of magnetic flux and have finite radius ?m. 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.

  1. Fluctuation dynamo based on magnetic reconnections

    CERN Document Server

    Baggaley, Andrew W; Shukurov, Anvar; Subramanian, Kandaswamy

    2009-01-01

    We develop a new model of the fluctuation dynamo in which the magnetic field is confined to thin flux ropes advected by a multi-scale flow which models turbulence. Magnetic dissipation occurs only via reconnections of flux ropes. The model is particularly suitable for rarefied plasma, such as the Solar corona or galactic halos. We investigate the kinetic energy release into heat, mediated by dynamo action, both in our model and by solving the induction equation with the same flow. We find that the flux rope dynamo is more than an order of magnitude more efficient at converting mechanical energy into heat. The probability density of the magnetic energy released during reconnections has a power-law form with the slope -3, consistent with the Solar corona heating by nanoflares. We also present a nonlinear extension of the model. This shows that a plausible saturation mechanism of the fluctuation dynamo is the suppression of turbulent magnetic diffusivity, due to suppression of random stretching at the location o...

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    CERN Document Server

    2003-01-01

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  3. Comment on Lockwood and Davis, "On the longitudinal extent of magnetopause reconnection pulses"

    Directory of Open Access Journals (Sweden)

    W. J. Heikkila

    Full Text Available Lockwood and Davis (1996 present a concise description of magnetopause reconnection pulses, with the claimed support of three types of observations: (1 flux transfer events (FTE, (2 poleward-moving auroral forms on the dayside, and (3 steps in cusp ion dispersion characteristics. However, there are a number of errors and misconceptions in the paper that make their conclusions untenable. They do not properly take account of the fact that the relevant processes operate in the presence of a plasma. They fail to notice that the source of energy (a dynamo with E · J<0 must be close to the region of dissipation (the electrical load with E · J>0 in transient phenomena, since energy (or information cannot travel faster than the group velocity of waves in the medium (here the Alfvén velocity VA. In short, Lockwood and Davis use the wrong contour in their attempt to evaluate the electromotive force (emf. This criticism goes beyond their article: a dynamo is not included in the usual definition of reconnection, only the reconnection load. Without an explicit source of energy in the assumed model, the idea of magnetic reconnection is improperly posed. Recent research has carried out a superposed epoch analysis of conditions near the dayside magnetopause and has found the dynamo and the load, both within the magnetopause current sheet. Since the magnetopause current is from dawn to dusk, the sign of E · J reflects the sign of the electric field. The electric field reverses, within the magnetopause; this can be discovered by an application of Lenz's law using the concept of erosion of the magnetopause. The net result is plasma transfer across the magnetopause to feed the low latitude boundary layer, at least partly on closed field lines, and viscous interaction as the mechanism by which solar wind plasma couples to the magnetosphere.

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    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...

  6. 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...

  7. 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...

  8. PLACES AVAILABLE

    CERN Multimedia

    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...

  9. 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...

  10. PLACES AVAILABLE

    CERN Document Server

    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...

  11. 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...

  12. 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.

  13. PLACES AVAILABLE

    CERN Document Server

    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...

  14. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: LabVIEW Basics 2: 13 & 14.5.02 (2 days) 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) The CERN Engineering Data Management System for Advanced users:  30.5.02  (1 day) LabVIEW Basics 1:  3 - 5.6.02  (3 days) AutoCAD 2002 - condensé : 4 - 6.6.02 (3 jours) LabVIEW DAQ (E):  6 & 7.6.02  (2 days) AutoCAD 2002 - Level 1:  10 - 12 and 24 - 26.6.02  (6 days) If you wish to participate in one of these courses, please discuss with your supervisor and apply electronically directly from the c...

  15. PLACES AVAILABLE

    CERN Multimedia

    Monique Duval

    2002-01-01

    Places are available in the following courses: 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) The CERN Engineering Data Management System for Advanced users:  30.5.02  (1 day) LabVIEW Basics 1:  3 - 5.6.02  (3 days) AutoCAD 2002 - condensé : 4 - 6.6.02 (3 jours) LabVIEW DAQ (E):  6 & 7.6.02  (2 days) AutoCAD 2002 - Level 1:  10 - ...

  16. 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...

  17. 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...

  18. 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...

  19. PLACES AVAILABLE

    CERN Multimedia

    TECHNICAL TRAINING; Tel. 74460

    2001-01-01

    Places are available in the following courses: MS-Project 1er niveau : 20 - 23.2.01 (4 matins) Architecture d'automatisme : 20 - 21.2.01 (2 jours) Introduction à PowerPoint : 26.2.01 (1 journée) Programmation TSX Premium 1 (Schneider) : 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) 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 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: 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 ...

  1. 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...

  2. PLACES AVAILABLE

    CERN Document Server

    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...

  3. PLACES AVAILABLE

    CERN Document Server

    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...

  4. PLACES AVAILABLE

    CERN Document Server

    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 ...

  5. Places available**

    CERN Document Server

    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...

  6. 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)...

  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: 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...

  9. PLACES AVAILABLE

    CERN Document Server

    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....

  10. PLACES AVAILABLE

    CERN Document Server

    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):...

  11. 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...

  12. 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...

  13. 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 ...

  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) : 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...

  15. 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....

  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 : 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 ...

  18. 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...

  19. 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...

  20. 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...

  1. PLACES AVAILABLE

    CERN Multimedia

    Technical training; Tel. 74924

    2001-01-01

    Places are available in the following courses: PROFIBUS : 25 - 26.9.01 (2 jours) PROFIBUS : 27 - 28.9.01 (2 days) Automates et réseaux de terrain : 3 - 4.10.2001 (2 jours) PCAD Schémas - débutants : 4 - 5.10.01 (2 jours) PCAD PCB - débutants : 8 - 10.10.01 (3 jours) Programmation TSX Premium 1 : 15 - 19.10.01 (5 jours) 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) Autocad Migration support courses: a detailed calendar will be published shortly for this series of sessions which will start on 15.10.2001. Registration is already open AutoCAD : Mise à jour AutoCAD r-14 vers 2002 (2 jours) AutoCAD Mechanical PowerPack 6 basé sur AutoCAD 2002 (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)...

  2. 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...

  3. 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...

  4. 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...

  5. 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 ...

  6. 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...

  7. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: 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) Habilitation électrique : électriciens network : 27 - 29.11.2001 (3 jours) Object-Oriented Analysis and Design :  27 - 30.11.2001  (4 days) Introduction to the CERN Engineering Data Management System :  30.11.2001 (1 day) Electromagnetic Compatibility (EMC): Introduction (bilingual) :  3.12.01 (half-day) Introduction to the CERN Engineering Data Management System : 07.12.2001 (1 day) LabVIEW - Basics 1 :  10 - 12.12.01 (3 days) LabVIEW - Basics 2 :  13 - 14.12.01 (2 days) 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) FileMaker P...

  8. 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...

  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 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)....

  11. 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-...

  12. 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)...

  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

    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) ...

  15. 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:&...

  16. 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...

  17. Places available**

    CERN Multimedia

    2003-01-01

    Places are available in the following courses : 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) 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) EXCEL 2000 - niveau 2 : 24 & 25.6.03 (2 jours) Siemens SIMATIC Training : Introduction to STEP7 : 3 & 4.6.03 (2 jours/2 days) STEP7 Programming : 16 - 20.6.03 (5 jours/5 days) Simatic Net Network : 26 & 27.6.03 (2 jours/2 days) These courses will be given in French or English following the requests. Programmation automate Schneider : Programmation automate Schneider TSX Premium - 1er niveau : 10 - 13.6.03 (4 jours) - audience : toute personne qui veux maitriser la msie en uvre et la programmation d'un automate TSX Premium - objectifs : maitriser la mise en uvre et la programmation d'un autom...

  18. 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...

  19. 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 Mechanical 6 PowerPack (E): 5, 6, 12, 13, 26, 27.6.03 (6 days) 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) Introduction to PVSS: 16.6.03 (half-day, pm) Basic PVSS: 17 - 19.6.03 (3 days) Réalisation de PCB rapides dans le flot Cadence: 17.6.03 (matin) LabView DSC (language to be defined): 19 & 20.6.03 PVSS - JCOP Framework Tutorial: 20.6.03 (1 day) 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 (2 days) These courses will be given...

  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) 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...

  1. 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 -...

  2. 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 ...

  3. 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 (...

  4. 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...

  5. 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) UNIX pour non-programmeurs : 5 - 7.11.01 (3 jours) Nouveautés d'EXCEL : 5.11.01 (1/2 journée) Introduction a 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) 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 - 30.11.01 (5 jours) Autocad Migration support courses: a detail...

  6. PLACES AVAILABLE

    CERN Multimedia

    Technical Training; Tel. 74924

    2001-01-01

    Places are available in the following courses: 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) C++ for Particle Physicists : 8 - 12.10.01 (6 lectures) 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) 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) 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) Introd...

  7. 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...

  8. Studies of Magnetic Reconnection in Colliding Laser-Produced Plasmas

    Science.gov (United States)

    Rosenberg, Michael

    2013-10-01

    Novel images of magnetic fields and measurements of electron and ion temperatures have been obtained in the magnetic reconnection region of high- ?, laser-produced plasmas. Experiments using laser-irradiated foils produce expanding, hemispherical plasma plumes carrying MG Biermann-battery magnetic fields, which can be driven to interact and reconnect. Thomson-scattering measurements of electron and ion temperatures in the interaction region of two colliding, magnetized plasmas show no thermal enhancement due to reconnection, as expected for ? ~ 8 plasmas. Two different proton radiography techniques used to image the magnetic field structures show deformation, pileup, and annihilation of magnetic flux. High-resolution images reveal unambiguously reconnection-induced jets emerging from the interaction region and show instabilities in the expanding plasma plumes and supersonic, hydrodynamic jets due to the plasma collision. Quantitative magnetic flux data show that reconnection in experiments with asymmetry in the scale size, density, temperature, and plasma flow across the reconnection region occurs less efficiently than in similar, symmetric experiments. This result is attributed to disruption of the Hall mechanism mediating collisionless reconnection. The collision of plasmas carrying parallel magnetic fields has also been probed, illustrating the deformation of magnetic field structures in high-energy-density plasmas in the absence of reconnection. These experiments are particularly relevant to high- ? reconnection environments, such as the magnetopause. Novel images of magnetic fields and measurements of electron and ion temperatures have been obtained in the magnetic reconnection region of high- ?, laser-produced plasmas. Experiments using laser-irradiated foils produce expanding, hemispherical plasma plumes carrying MG Biermann-battery magnetic fields, which can be driven to interact and reconnect. Thomson-scattering measurements of electron and ion temperatures in the interaction region of two colliding, magnetized plasmas show no thermal enhancement due to reconnection, as expected for ? ~ 8 plasmas. Two different proton radiography techniques used to image the magnetic field structures show deformation, pileup, and annihilation of magnetic flux. High-resolution images reveal unambiguously reconnection-induced jets emerging from the interaction region and show instabilities in the expanding plasma plumes and supersonic, hydrodynamic jets due to the plasma collision. Quantitative magnetic flux data show that reconnection in experiments with asymmetry in the scale size, density, temperature, and plasma flow across the reconnection region occurs less efficiently than in similar, symmetric experiments. This result is attributed to disruption of the Hall mechanism mediating collisionless reconnection. The collision of plasmas carrying parallel magnetic fields has also been probed, illustrating the deformation of magnetic field structures in high-energy-density plasmas in the absence of reconnection. These experiments are particularly relevant to high- ? reconnection environments, such as the magnetopause. This work was performed in collaboration with C. Li, F. Séguin, A. Zylstra, H. Rinderknecht, H. Sio, J. Frenje, and R. Petrasso (MIT), I. Igumenshchev, V. Glebov, C. Stoeckl, and D. Froula (LLE), J. Ross and R. Town (LLNL), W. Fox (UNH), and A. Nikroo (GA), and was supported in part by the NLUF, FSC/UR, U.S. DOE, LLNL, and LLE.

  9. Observational Evidence for the Causes and Consequences of Chromospheric Reconnection

    Science.gov (United States)

    Yan, Limei; He, Jiansen; Xia, Lidong; Jiao, Fangran

    2015-05-01

    The chromospheric anemone jets with an inverse “Y” shape are ubiquitous, as revealed by the Solar Optical Telescope observations. These jets are considered to be consequences of chromospheric magnetic reconnections. Although these jets have been studied intensively, the dynamics and their driving causes remain unclear observationally. In this work, we report a case of a chromospheric jet showing complete observational evidence for the cause and consequence of chromospheric intermittent reconnection. The intermittent eruption of this jet shows two distinct quasi-periods, 50-60 s and 600-700 s. The short-period eruptions may be related to the plasmoid-induced reconnection, and the long-period ones may be interpreted as sequences of cycles of energy storage and release during magnetic reconnections. The observations also reveal Alfvénic waves with a mean period around 88 s and a maximum transverse displacement around 0.?26. The jet is hosted by a loop moving smoothly with a horizontal speed of ˜0.4 km s-1. Our results provide observational evidence supporting the magnetic reconnection model of the formation of the chromospheric jets with related products, in which the loop advection drives intermittent magnetic reconnections, and the reconnection outflows carrying plasmoids collide further with the ambient field lines and finally excite waves and jets.

  10. 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.

  11. Total magnetic reconnection during a tokamak major disruption

    International Nuclear Information System (INIS)

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

  12. Inner Plasma Structure of the Low-Latitude Reconnection Layer

    Science.gov (United States)

    Zhang, Q.-H.; Dunlop, M. W.; Lockwood, M.; Lavraud, B.; Bogdanova, Y. V.; Hasegawa, H.; Yang, H. -G.; Liu, R. -Y.; Hu, H. -Q.; Zhang, B. -C.; Pu, Z. -Y.; Yang, Z. -W.; Wang, J.; Taylor, M. G. G. T.; Berchem, J.; Constantinescu, D.; Volwerk, M.; Frey, H.; Fazakerley, A. N.; Shen, C.; Shi, J. -K.; Sibeck, D.; Escoubet, P.; Wild, J. A.

    2012-01-01

    We report a clear transition through a reconnection layer at the low-latitude magnetopause which shows a complete traversal across all reconnected field lines during northwestward interplanetary magnetic field (IMF) conditions. The associated plasma populations confirm details of the electron and ion mixing and the time history and acceleration through the current layer. This case has low magnetic shear with a strong guide field and the reconnection layer contains a single density depletion layer on the magnetosheath side which we suggest results from nearly field-aligned magnetosheath flows. Within the reconnection boundary layer, there are two plasma boundaries, close to the inferred separatrices on the magnetosphere and magnetosheath sides (Ssp and Ssh) and two boundaries associated with the Alfvén waves (or Rotational Discontinuities, RDsp and RDsh). The data are consistent with these being launched from the reconnection site and the plasma distributions are well ordered and suggestive of the time elapsed since reconnection of the field lines observed. In each sub-layer between the boundaries the plasma distribution is different and is centered around the current sheet, responsible for magnetosheath acceleration. We show evidence for a velocity dispersion effect in the electron anisotropy that is consistent with the time elapsed since reconnection. In addition, new evidence is presented for the occurrence of partial reflection of magnetosheath electrons at the magnetopause current layer.

  13. Location of the reconnection line at the magnetopause during southward IMF conditions

    Science.gov (United States)

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

    2007-02-01

    Magnetic reconnection transfers energy from magnetic fields to particles in space, but the conditions under which reconnection is initiated are not well understood. Indirect evidence confirms the existence of reconnection where merging fields are anti-parallel, but also confirms the existence of another type of reconnection, called component reconnection. This ambiguity has resulted in considerable debate over which of these types of reconnection dominates. Here we report on a method using 3D plasma observations from the TIMAS instrument on Polar as it passes through the northern cusp to calculate the distance to the reconnection line, and subsequently trace this distance to the magnetopause. Results from 130 events reveal that in general, magnetic reconnection occurs along an extended line across the dayside magnetopause, consistent with the component reconnection scenario. These results indicate that reconnection in other regions of space (e.g., solar flares, Earth's magnetotail) should not be limited to anti-parallel magnetic field geometries.

  14. Experimental Investigation of the Trigger Problem in Magnetic Reconnection

    Science.gov (United States)

    Egedal, Jan

    2012-07-01

    Magnetic reconnection releases magnetic energy not only in steady-state, but also in time-dependent and often explosive events requiring a transition from slow reconnection to fast. The question of what causes this transition is known as the ``trigger problem'' and is not well understood. We address the trigger problem using the Versatile Toroidal Facility (VTF) at MIT. We observe spontaneous reconnection events [1] with exponentially growing reconnection rates, and we characterize the 3D dynamics of these events using multiple internal probes. The observed reconnection is asymmetric: it begins at one toroidal location and propagates around in both directions. The spontaneous onset is facilitated by an interaction between the x-line current channel and a global mode in the electrostatic potential. It is this mode which breaks axisymmetry and enables a localized decrease in x-line current. We model the onset using an empirical Ohm's law and current continuity, which is maintained by ion polarization currents associated with the mode. The model reproduces the exponential growth of the reconnection electric field, and the model growth rate agrees well with the experimentally measured growth rate. The onset location is likely determined by small asymmetries in the in-vessel coils. To further investigate this conjecture new coils have been installed, which allow for controlled changes in toroidal asymmetry. The observations are suggestive of solar flare dynamics and are relevant to tokamak research [3]. [1] Egedal, J. et al. Laboratory Observations of Spontaneous Magnetic Reconnection. Phys. Rev. Lett. 98, 015003 (2007). [2] Katz, N. et al. Laboratory Observation of Localized Onset of Magnetic Reconnection. Phys. Rev. Lett. 104, 255004 (2010). [3] Park, H.K. et al. Self-organized Te redistribution during driven reconnection processes in high-temperature plasmas. Phys. Plasmas 13, 055907 (2006).

  15. 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…

  16. 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.

  17. Reconnection of Unstable/Stable Manifolds of the Harper Map

    CERN Document Server

    Ajisaka, S

    2006-01-01

    The Harper map is one of the simplest chaotic systems exhibiting reconnection of invariant manifolds. The method of asymptotics beyond all orders (ABAO) is used to construct unstable/stable manifolds of the Harper map. By enlarging the neighborhood of a singularity, the perturbative solution of the unstable manifold is expressed as a Borel summable asymptotic expansion in a sector including $t=-\\infty$ and is analytically continued to the other sectors, where the solution acquires new terms describing heteroclinic tangles. When the parameter changes to the reconnection threshold, the unstable/stable manifolds are shown to acquire new oscillatory portion corresponding to the heteroclinic tangle after the reconnection.

  18. A New Electric Field in Asymmetric Magnetic Reconnection

    CERN Document Server

    Malakit, Kittipat; Cassak, Paul A; Ruffolo, David

    2013-01-01

    We present a theory and numerical evidence for the existence of a previously unexplored in-plane electric field in collisionless asymmetric magnetic reconnection. This electric field, dubbed the "Larmor electric field," is associated with finite Larmor radius effects and is distinct from the known Hall electric field. Potentially, it could be an important indicator for the upcoming Magnetospheric Multiscale (MMS) mission to locate reconnection sites as we expect it to appear on the magnetospheric side, pointing Earthward, at the dayside magnetopause reconnection site.

  19. 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.

  20. Three-dimensional magnetic reconnection regimes: A review

    CERN Document Server

    Pontin, D I

    2011-01-01

    The magnetic field in many astrophysical plasmas -- such as the Solar corona and Earth's magnetosphere -- has been shown to have a highly complex, three-dimensional structure. Recent advances in theory and computational simulations have shown that reconnection in these fields also has a three-dimensional nature, in contrast to the widely used two-dimensional (or 2.5-dimensional) models. Here we discuss the underlying theory of three-dimensional magnetic reconnection. We also review a selection of new models that illustrate the current state of the art, as well as highlighting the complexity of energy release processes mediated by reconnection in complicated three-dimensional magnetic fields.

  1. FLARE (Facility for Laboratory Reconnection Experiments): A Major Next-Step for Laboratory Studies of Magnetic Reconnection

    Science.gov (United States)

    Ji, Hantao; Bhattacharjee, A.; Prager, S.; Daughton, W.; Bale, Stuart D.; Carter, T.; Crocker, N.; Drake, J.; Egedal, J.; Sarff, J.; Fox, W.; Jara-Almonte, J.; Myers, C.; Ren, Y.; Yamada, M.; Yoo, J.

    2015-04-01

    A new intermediate-scale plasma experiment, called the Facility for Laboratory Reconnection Experiments or FLARE (flare.pppl.gov), is under construction at Princeton as a joint project by five universities and two national labs to study magnetic reconnection in regimes directly relevant to heliophysical and astrophysical plasmas. The currently existing small-scale experiments have been focusing on the single X-line reconnection process in plasmas either with small effective sizes or at low Lundquist numbers, both of which are typically very large in natural plasmas. These new regimes involve multiple X-lines as guided by a reconnection "phase diagram", in which different coupling mechanisms from the global system scale to the local dissipation scale are classified into different reconnection phases [H. Ji & W. Daughton, Phys. Plasmas 18, 111207 (2011)]. The design of the FLARE device is based on the existing Magnetic Reconnection Experiment (MRX) (mrx.pppl.gov) and is to provide experimental access to the new phases involving multiple X-lines at large effective sizes and high Lundquist numbers, directly relevant to magnetospheric, solar wind, and solar coronal plasmas. After a brief summary of recent laboratory results on the topic of magnetic reconnection, the motivating major physics questions, the construction status, and the planned collaborative research especially with heliophysics communities will be discussed.

  2. 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.

  3. Resistive instabilities and field line reconnection

    International Nuclear Information System (INIS)

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

  4. Resistive instabilities and field line reconnection

    Energy Technology Data Exchange (ETDEWEB)

    White, R.B.

    1980-05-01

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

  5. Plasma Astrophysics, part II Reconnection and Flares

    CERN Document Server

    Somov, Boris V

    2007-01-01

    This well-illustrated monograph is devoted to classic fundamentals, current practice, and perspectives of modern plasma astrophysics. The first part is unique in covering all the basic principles and practical tools required for understanding and working in plasma astrophysics. The second part presents the physics of magnetic reconnection and flares of electromagnetic origin in space plasmas within the solar system; single and double stars, relativistic objects, accretion disks, and their coronae are also covered. This book is designed mainly for professional researchers in astrophysics. However, it will also be interesting and useful to graduate students in space sciences, geophysics, as well as advanced students in applied physics and mathematics seeking a unified view of plasma physics and fluid mechanics.

  6. TWISTING, RECONNECTING MAGNETOSPHERES AND MAGNETAR SPINDOWN

    International Nuclear Information System (INIS)

    We present the first simulations of evolving, strongly twisted magnetar magnetospheres. Slow shearing of the magnetar crust is seen to lead to a series of magnetospheric expansion and reconnection events, corresponding to X-ray flares and bursts. The axisymmetric simulations include rotation of the neutron star and the magnetic wind through the light cylinder. We study how the increasing twist affects the spindown rate of the star, finding that a dramatic increase in spindown occurs. Particularly spectacular are explosive events caused by the sudden opening of large amounts of overtwisted magnetic flux, which may be associated with the observed giant flares. These events are accompanied by a short period of ultrastrong spindown, resulting in an abrupt increase in spin period, such as was observed in the giant flare of SGR 1900+14.

  7. 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

  8. The formation and stability of Petschek reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Baty, H., E-mail: hubert.baty@unistra.fr [Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l' Université, F-67000 Strasbourg (France); Forbes, T. G., E-mail: terry.forbes@unh.edu [Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824 (United States); Priest, E. R., E-mail: eric@mcs.st-and.ac.uk [Institute of Mathematics, University of St. Andrews, Fife KY169SS, Scotland (United Kingdom)

    2014-11-15

    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.

  9. Integrating Kinetic Effects into Global Models for Reconnection

    Science.gov (United States)

    Antiochos, S. K.

    2012-01-01

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

  10. Phase diagrams of forced magnetic reconnection in Taylor's model

    Science.gov (United States)

    Comisso, L.; Grasso, D.; Waelbroeck, F. L.

    2015-10-01

    > , depending on the parameters that characterize the external drive, which have not been considered until now. These features are crucial to understanding the onset and evolution of magnetic reconnection in diverse physical systems.

  11. Direct Measurements of Reconnection Rate Attenuation by Plasmasphere Plumes

    Science.gov (United States)

    Sanchez, E. R.; Takahashi, K.

    2013-12-01

    It is widely hypothesized that mass loading of the magnetosphere (the process whereby the average mass density of the magnetosphere increases from its nominal value) significantly impacts solar wind-magnetosphere coupling and circulation within the magnetosphere. One important way in which mass loading can affect the magnetosphere occurs when enhanced convection after a lull in geomagnetic activity brings super-dense plasma from the plasmasphere (the so-called plasmsphere plume) into the dayside reconnection site. We measured the magnetic flux across the dayside polar cap boundary (a proxy of the dayside magnetic field reconnection rate) and tracked the sunward migration of the plasma plume for three storms that occurred after long intervals of quiet conditions. Significant intermittent reduction in the dayside reconnection potential (approximately 66% in the most pronounced case) was observed in the hours following the onset of negative IMF Bz condition, in agreement with the hypothesis that super-dense magnetospheric plasma convected into the dayside magnetopause inhibits reconnection.

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

    Science.gov (United States)

    Cargill, Peter

    2013-06-01

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

  13. The role of guide field in relativistic pair plasma reconnection

    CERN Document Server

    Zenitani, S

    2007-01-01

    We study the role of guide field in relativistic magnetic reconnection in a Harris current sheet of pair ($e^{\\pm}$) plasmas, using linear theories and particle-in-cell (PIC) simulations. Two-dimensional PIC simulations exhibit the guide field dependence to the linear instabilities; the tearing or reconnection modes are relatively insensitive, while the relativistic drift-kink instability (RDKI), the fastest mode in a relativistic current sheet, is stabilized by the guide field. Particle acceleration in the nonlinear stage is also investigated. A three-dimensional PIC simulation demonstrates that the current sheet is unstable to the RDKI, although small reconnection occurs in the deformed current sheet. Another three-dimensional PIC simulation with a guide field demonstrates a completely different scenario. Secondary magnetic reconnection is triggered by nonlinear coupling of oblique instabilities, which we call the relativistic drift-sausage tearing instability. Therefore, particle acceleration by relativist...

  14. Accelerated jets of energetic protons generated by torsional fan reconnection

    Science.gov (United States)

    Hosseinpour, M.

    2015-08-01

    Magnetic reconnection is a potential mechanism for charged particle acceleration in astrophysical and space plasmas, especially in solar flares, which are rich sources of highly energetic particles. "Torsional fan reconnection" is one type of model for steady-state 3D null point reconnection. In this study, we investigate proton acceleration with input parameters for the solar corona in the presence of the magnetic and electric fields associated with torsional fan reconnection. By randomly injecting a population of 10,000 protons as test particles in the vicinity of a null point, we show that two symmetric jets of accelerated protons with relativistic energies are generated along the spine axis above and below the fan plane. These jets comprise almost all of the population with average kinetic energy on the order of a few . Also, the details of the energy spectra are discussed.

  15. Energy of Alfven waves generated during magnetic reconnection

    CERN Document Server

    Wang, L C; Ma, Z W; Zhang, X; Lee, L C

    2015-01-01

    A new method for the determination of the Alfven wave energy generated during magnetic reconnection is introduced and used to analyze the results from two-dimensional MHD simulations. It is found that the regions with strong Alfven wave perturbations almost coincide with that where both magnetic-field lines and flow-stream lines are bent, suggesting that this method is reliable for identifying Alfven waves. The magnetic energy during magnetic reconnection is mainly transformed into the thermal energy. The conversion rate to Alfven wave energy from the magnetic energy is strongly correlated to the magnetic reconnection rate. The maximum conversion rate at the time with the peak reconnection rate is found to be only about 4% for the cases with the plasma beta=0.01,0.1, and 1.0.

  16. Time Scales for Energy Release in Hall Magnetic Reconnection

    Science.gov (United States)

    Huba, J. D.; Rudakov, L. I.

    2004-05-01

    We present a study of the time scales for energy release in 2D Hall magnetic reconnection. We use the NRL Hall MHD code VooDoo for this study. We consider a 2D reversed field current layer with a magnetic perturbation that initiates the reconnection process. We use boundary conditions that allow inflow and outflow (i.e., not periodic) and let the system reach a steady state. We find that the system goes through three stages: a relatively long current layer thinning process, a fast reconnection phase, and a final steady state phase. We define the time scale for energy release as the fast reconnection period: from onset to steady state. Preliminary results indicate that the time for energy release scales as the initial thickness of the current layer. We apply these results to the magnetotail and magnetopause. Research supported by NASA and ONR.

  17. 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.

  18. 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...

  19. Magnetic Reconnection and Intermittent Turbulence in the Solar Wind

    CERN Document Server

    Osman, K T; Gosling, J T; Greco, A; Servidio, S; Hnat, B; Chapman, S C; Phan, T D

    2014-01-01

    A statistical relationship between magnetic reconnection, current sheets and intermittent turbulence in the solar wind is reported for the first time using in-situ measurements from the Wind spacecraft at 1 AU. We identify intermittency as non-Gaussian fluctuations in increments of the magnetic field vector, $\\mathbf{B}$, that are spatially and temporally non-uniform. The reconnection events and current sheets are found to be concentrated in intervals of intermittent turbulence, identified using the partial variance of increments method: within the most non-Gaussian 1% of fluctuations in $\\mathbf{B}$, we find 87%-92% of reconnection exhausts and $\\sim$9% of current sheets. Also, the likelihood that an identified current sheet will also correspond to a reconnection exhaust increases dramatically as the least intermittent fluctuations are removed from the dataset. Hence, the turbulent solar wind contains a hierarchy of intermittent magnetic field structures that are increasingly linked to current sheets, which ...

  20. 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

  1. 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 district for better educational opportunities; and (7) Teachers were not familiar with the term "culturally responsive teaching," but there was evidence that several aspects of it were present in the seventh-grade science classroom environment. Critical Race Theory (CRT) was the framework for analysis and interpretation of this research study. The findings support the following tenets of CRT: (a) racism is normal, (b) interest-convergence or colorblindness, (c) contextual-historical analysis, (d) storytelling or counterstorytelling, and (e) social transformation. These findings indicate that racial inequalities remain an issue in the underachievement of African Americans and may be the solution to improving science learning of African Americans. The outcome of this study contributes to the limited research on utilizing culturally responsive teaching along with best teaching strategies to improve academic achievement of African American students, and CRT exposes the issues that contribute to the Black-White achievement gap in science widening.

  2. High power heating of magnetic reconnection in merging tokamak experiments

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Y.; Tanabe, H.; Gi, K.; Watanabe, T.; Ii, T. [University of Tokyo, Tokyo 113-8656 (Japan); Yamada, T. [Kyusyu University, Fukuoka 819-0395 (Japan); Gryaznevich, M.; Scannell, R.; Conway, N. [CCFE, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Crowley, B. [General Atomics Court, California 92186-5608 (United States); Michael, C. [Australian National University, Canberra 0200 (Australia)

    2015-05-15

    Significant ion/electron heating of magnetic reconnection up to 1.2?keV was documented in two spherical tokamak plasma merging experiment on MAST with the significantly large Reynolds number R?10{sup 5}. Measured 1D/2D contours of ion and electron temperatures reveal clearly energy-conversion mechanisms of magnetic reconnection: huge outflow heating of ions in the downstream and localized heating of electrons at the X-point. Ions are accelerated up to the order of poloidal Alfven speed in the reconnection outflow region and are thermalized by fast shock-like density pileups formed in the downstreams, in agreement with recent solar satellite observations and PIC simulation results. The magnetic reconnection efficiently converts the reconnecting (poloidal) magnetic energy mostly into ion thermal energy through the outflow, causing the reconnection heating energy proportional to square of the reconnecting (poloidal) magnetic field B{sub rec}{sup 2}?????B{sub p}{sup 2}. The guide toroidal field B{sub t} does not affect the bulk heating of ions and electrons, probably because the reconnection/outflow speeds are determined mostly by the external driven inflow by the help of another fast reconnection mechanism: intermittent sheet ejection. The localized electron heating at the X-point increases sharply with the guide toroidal field B{sub t}, probably because the toroidal field increases electron confinement and acceleration length along the X-line. 2D measurements of magnetic field and temperatures in the TS-3 tokamak merging experiment also reveal the detailed reconnection heating mechanisms mentioned above. The high-power heating of tokamak merging is useful not only for laboratory study of reconnection but also for economical startup and heating of tokamak plasmas. The MAST/TS-3 tokamak merging with B{sub p}?>?0.4?T will enables us to heat the plasma to the alpha heating regime: T{sub i}?>?5?keV without using any additional heating facility.

  3. Should You Take Dietary Supplements?

    Science.gov (United States)

    ... for joint pain) and herbal supplements such as echinacea (immune health) and flaxseed oil (digestion). Many supplements ... first place, the dose and possible interactions with medicine you’re already taking.” For vitamins and minerals, ...

  4. Evolution of electron current sheets in collisionless magnetic reconnection

    Science.gov (United States)

    Jain, Neeraj; Sharma, A. Surjalal

    2015-10-01

    An electron current sheet embedded in an ion scale current sheet is an inherent feature of collisionless magnetic reconnection. Such thin electron current sheets are unstable to tearing mode and produce secondary magnetic islands modulating the reconnection rate. In this work, 2-D evolution of tearing mode at multiple reconnection sites in an electron current sheet is studied using electron-magnetohydrodynamic (EMHD) model. It is shown that growth of the perturbations can make reconnection impulsive by suddenly enhancing the reconnection rate and also forms new structures in the presence of multiple reconnection sites, one of which is dominant and others are secondary. The rise of the reconnection rate to a peak value and the time to reach the peak value due to tearing instability are similar to those observed in particle-in-cell simulations for similar thicknesses of the electron current sheet. The peak reconnection rate scales as 0.05 / ? 1.15 , where ? is half thickness of the current sheet. Interactions of electron outflows from the dominant and secondary sites form a double vortex sheet inside the magnetic island between the two sites. Electron Kelvin-Helmholtz instability in the double vortex sheet produces secondary vortices and consequently turbulence inside the magnetic island. Interaction of outflow from the dominant site and inflows to the adjacent secondary sites launches whistler waves which propagate from the secondary sites into the upstream region at Storey angle with the background magnetic field. Due to the wave propagation, the out-of-plane magnetic field has a nested structure of quadrupoles of opposite polarities. A numerical linear eigen value analysis of the EMHD tearing mode, valid for current sheet half-thicknesses ranging from ? d e (weak electron inertia), is presented.

  5. Universal Reconnection of Non-Abelian Cosmic Strings

    OpenAIRE

    Eto, Minoru; Hashimoto, Koji; Marmorini, Giacomo; Nitta, Muneto(Department of Physics, and Research and Education Center for Natural Sciences, Keio University, Hiyoshi 4-1-1, Yokohama, Kanagawa 223-8521, Japan); Ohashi, Keisuke; Vinci, Walter(London Centre for Nanotechnology and Computer Science, University College London, 17-19 Gordon Street, London, WC1H 0AH, United Kingdom)

    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.

  6. Reconnection Studies Under Different Types of Turbulence Driving

    OpenAIRE

    Kowal, G; Lazarian, A.; Vishniac, E. T.; K. Otmianowska-Mazur

    2012-01-01

    We study a model of fast magnetic reconnection in the presence of weak turbulence proposed by Lazarian and Vishniac (1999) using three-dimensional direct numerical simulations. The model has been already successfully tested in Kowal et al. (2009) confirming the dependencies of the reconnection speed Vrec on the turbulence injection power Pinj and the injection scale linj

  7. 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...

  8. Taking Leave?

    CERN Multimedia

    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...

  9. 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 (??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 (??di)

  10. An Analytic Study of the Perpendicularly Propagating Electromagnetic Drift Instabilities in the Magnetic Reconnection Experiment

    International Nuclear Information System (INIS)

    A local linear theory is proposed for a perpendicularly propagating drift instability driven by relative drifts between electrons and ions. The theory takes into account local cross-field current, pressure gradients and modest collisions as in the Magnetic Reconnection Experiment (MRX) (10). The unstable waves have very small group velocities in the direction of the pressure gradient, but have a large phase velocity near the relative drift velocity between electrons and ions in the direction of cross-field current. By taking into account the electron-ion collisions and applying the theory in the Harris sheet, we establish that this instability could be excited near the center of the Harris sheet and have enough efoldings to grow to large amplitude before it propagates out of the unstable region. Comparing with the other magnetic reconnection related instabilities (LHDI, MTSI et.) studied previously, we believe the instability we find is a favorable candidate to produce anomalous resistivity because of its unique wave characteristics, such as electromagnetic component, large phase velocity, and small group velocity in the cross current layer direction

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

    Science.gov (United States)

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

    2011-01-01

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

  12. MHD Analysis of Magnetic Reconnection in MRX

    Science.gov (United States)

    Ji, H.; Yamada, M.; Hsu, S. C.; Carter, T. A.

    1996-11-01

    One of the possible operation modes in MRX is the double annular plasma configuration, in which two annular plasmas are formed independently around two flux cores.(M. Yamada, et al.), this conference (1996). Once the annular plasmas are created, the poloidal field (PF) coil current can be increased or decreased. In the case of increasing PF coil current, the poloidal flux in each plasma is `` pushed" toward the X point (push mode). In the case of decreasing PF coil current, the poloidal flux in the common plasma is `` pulled" back toward the X point (pull mode). Pull mode reconnection has been intensively investigated in both the co-helicity case, where the third magnetic component (B_T) is large, and the counter-helicity case, where BT is essentially zero. The major findings are an O-shaped (Y-shaped) diffusion region has been identified in the co-helicity (counter-helicity) case; (2) the current sheet in the counter-helicity case is much narrower than in the co-helicity case; (3) each term of the induction equation and simple Ohm's law has been examined across the current sheet, and an enhancement of resistivity over its classical value by a factor of 5-20 has been measured. The cause of this resistivity enhancement will be discussed. Time evolution of the global magnetic helicity and magnetic energy during the merging process will be also presented.

  13. 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.

  14. BP-Mobil partnership. The common network takes place

    International Nuclear Information System (INIS)

    After the partnership between BP and Mobil was signed, the program of transformation of the petrol stations network started in November 1996 in the UK and concern 3300 stations in Europe and 800 stations in France. About 9100 stations will be transformed by the end of 1998. BP France is the operator for petroleum products (petrol, fuel, bitumens, LPG..) with a 70% share holding (30% for Mobil) while Mobil is the major shareholder (51%) for the lubricants and special products activities. The chemical, aviation nd maritime activities are not concerned. Thanks to the fusion of their down-file activities in Europe, the benefits of the partnership should reach 600 to 700 million of US Dollars each year. However the restructuring cost should reach 740 millions of US Dollars in two years, which doubles the initial estimation. Short paper. (J.S.)

  15. Group B streptococcal infection: when does vertical transmission take place?

    OpenAIRE

    Michie, C. A.; Blumberg, R

    1995-01-01

    Expression of CD45 isoforms was used to estimate when group B streptococci had infected a child born with low Apgar scores who subsequently died. The measure suggested that infection was present more than 24 hours before delivery, thus distinguishing perinatal infection as the primary event which preceded intrapartum asphyxia in this case.

  16. Assessment : A Continuous Process that Takes Place at the End?

    OpenAIRE

    Andersson, Anna

    2008-01-01

         The hypothesis for this essay is: ”Teachers use assessment methods that are mainly summative and as a consequence student involvement in the assessment process is low, with too little focus on the goals of the education.” The primary aim is to investigate whether or not this hypothesis is true. To answer this, students were asked their opinions about assessment. Also, teachers were asked questions about assessment, to see if there is a correlation between students' and teachers' thoughts...

  17. The ‘taking place’ of learning in computer games

    DEFF Research Database (Denmark)

    Larsen, Lasse Juel; Løfgreen, Lars Bo

    2008-01-01

    to learn in schools, communities, and workplaces – new ways to learn for a new Information Age” [1].  In line with this general approach to seeing computer games as a reservoir of learning strategies and potentials, this paper aims to examine how a specific computer game teach us how to play the game...

  18. Do nuclear reactions take place under chemical stimulation?

    Energy Technology Data Exchange (ETDEWEB)

    Bockris, J.O.; Lin, G.H. [Texas A& M Univ., College Station, TX (United States); Bush, R.T. [California State Polytechnic Inst., Pomona, CA (United States)

    1996-09-01

    Several examples of nuclear reactions occurring under the stimulation of chemical type energies are given. The production of tritium from deuterium in Pd has more than 100 published confirmations. Three models suggest circumstances such that barriers between nucleii may become transparent. 24 refs.

  19. When does integration of independently acquired temporal relationships take place?

    Science.gov (United States)

    Molet, Mikael; Miguez, Gonzalo; Cham, Henry X; Miller, Ralph R

    2012-10-01

    Prior research has found that when subjects independently acquire 2 associations with a common element (e.g., S1-S2 and S2-US), each with its own temporal relationship, they behave as if the 2 unique cues (i.e., S1 and US) have a known temporal relationship despite their never having been paired. This is interpreted as indicative of temporal integration of the memories acquired during Phase 1 and Phase 2 of training based on the element common to both experiences (i.e., S2). There are 2 times at which such integration of independent temporal relationships could plausibly occur: at the time of acquisition of the second relationship or at the time of testing. Three lick-suppression experiments with rats were performed to determine when integration occurs. This question of the moment of temporal integration was assessed by extinguishing the mediating element (S2) between learning of the second temporal relationship and testing of S1. Experiment 1 (using sensory preconditioning) and Experiment 2 (using second-order conditioning) found that this manipulation interfered with behavioral control by S1, suggesting that temporal integration occurred at the time of testing. Experiment 3 used spontaneous recovery, a hallmark phenomenon of extinction, to confirm that the S2-alone presentations in Experiments 1 and 2 attenuated integration as a result of extinction of S2. Implications for the temporal coding hypothesis (e.g., Savastano & Miller, 1998) are discussed. PMID:22905828

  20. Using Personalized Education to Take the Place of Standardized Education

    Science.gov (United States)

    Gao, Pengyu

    2014-01-01

    Economic model has been greatly shifted from labor demanding to innovation demanding, which requires education system has to produce creative people. This paper illustrates how traditional education model accrued and developed based on satisfying the old economic model for labor demanding but did not meet the new social requirement for innovation…

  1. 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…

  2. 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.

  3. Turbulent Magnetohydrodynamic Reconnection Mediated by the Plasmoid Instability

    CERN Document Server

    Huang, Yi-Min

    2015-01-01

    It has been established that the Sweet-Parker current layer in high Lundquist number reconnection is unstable to the super-Alfv\\'enic plasmoid instability. Past two-dimensional magnetohydrodynamic simulations have demonstrated that the plasmoid instability leads to a new regime where the Sweet-Parker current layer changes into a chain of plasmoids connected by secondary current sheets, and the averaged reconnection rate becomes nearly independent of the Lundquist number. In this work, three-dimensional simulation with a guide field shows that the additional degree of freedom allows plasmoid instabilities to grow at oblique angles, which interact and lead to self-generated turbulent reconnection. The averaged reconnection rate in the self-generated turbulent state is of the order of a hundredth of the characteristic Alfv\\'en speed, which is similar to the two-dimensional result but is an order of magnitude lower than the fastest reconnection rate reported in recent studies of externally driven three-dimensiona...

  4. 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...

  5. Reconnection Efficiency Determined from Statistical Properties of Magnetosheath Flux

    Science.gov (United States)

    Zhang, H.; Khurana, K. K.; Kivelson, M.; Fu, S.; Pu, Z.; Wan, W.; Liu, L.; Zhu, C.

    2014-12-01

    The magnetospheric magnetic reconnection rate, RMR, is used to describe how fast magnetic reconnection proceeds on the dayside magnetopause. In literature, one of the proxies used for determining the reconnection rate is the plasma velocity in the reconnection inflow region, VIN, or, to be more accurate, the convective electric field parallel to the X line in the inflow region, E = VINBIN. On the magnetopause of the Earth, RMR divided by the rate at which solar wind flux is incident on the cross section of the magnetosphere can represent the input efficiency of the interplanetary magnetic field (IMF) into the Earth's magnetosphere. RMR on the magnetopause, however, is modified by local conditions such as the magnetic fields and plasma densities on both sides of the magnetopause. Thus RMR may vary with position on the magnetopause and the integral of RMR over the whole magnetopause is required to estimate the global efficiency of the input of IMF flux into the magnetosphere. We will present a new approach to establishing reconnection efficiency by comparing solar wind flux to measured magnetosheath flux carried in the flow near the terminator. We have conducted statistics on data collected by Cluster in the Earth's magnetosheath from 2001-2013. The global input efficiency of IMF flux into the magnetosphere is estimated and its relationship to the solar wind and IMF conditions is investigated in this presentation.

  6. Observations of significant flux closure by dual lobe reconnection

    Directory of Open Access Journals (Sweden)

    S. M. Imber

    2007-07-01

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

  7. RECONNECTION-DRIVEN DYNAMICS OF CORONAL-HOLE BOUNDARIES

    International Nuclear Information System (INIS)

    We investigate the effect of magnetic reconnection on the boundary between open and closed magnetic field in the solar corona. The magnetic topology for our numerical study consists of a global dipole that gives rise to polar coronal holes and an equatorial streamer belt, and a smaller active-region bipole embedded inside the closed-field streamer belt. The initially potential magnetic field is energized by a rotational motion at the photosphere that slowly twists the embedded-bipole flux. Due to the applied stress, the bipole field expands outward and reconnects with the surrounding closed flux, eventually tunneling through the streamer boundary and encountering the open flux of the coronal hole. The resulting interchange reconnection between closed and open field releases the magnetic twist and free energy trapped inside the bipole onto open field lines, where they freely escape into the heliosphere along with the entrained closed-field plasma. Thereafter, the bipole field relaxes and reconnects back down into the interior of the streamer belt. Our simulation shows that the detailed properties of magnetic reconnection can be crucial to the coronal magnetic topology, which implies that both potential-field source-surface and quasi-steady magnetohydrodynamic models may often be an inadequate description of the corona and solar wind. We discuss the implications of our results for understanding the dynamics of the boundary between open and closed field on the Sun and the origins of the slow wind.

  8. Crossed flux tubes 3D magnetic reconnection experiment

    Science.gov (United States)

    Bellan, Paul

    2011-10-01

    The formation and dynamics of writhing, plasma-filled, twisted open magnetic flux tubes is being investigated using laboratory experiments. The behavior of these flux tubes is relevant to solar corona loops, astrophysical jets, spheromak formation, and open field lines in tokamaks and RFP's. MHD forces have been determined to drive fast axial plasma flows into the flux tube from the boundary it intercepts. These flows fill the flux tubes with plasma while simultaneously injecting linked frozen-in azimuthal flux; helicity injection is thus associated with mass injection. An upgraded experiment under construction will have two adjacent arched plasma-filled flux tubes cross over each other. It is anticipated that a localized 3D reconnection will occur at the cross-over. This reconnection should result in half-twists in the post re-connection topology and subsequent Alfven wave propagation to equilibrate the half-twists along the post-reconnection flux tubes. The electrical circuitry requires two initially independent floating capacitor bank power supplies that become series-connected as a result of reconnection. Supported by DOE, NSF and AFOSR.

  9. Spontaneous three-dimensional magnetic reconnection in merging toroidal plasma experiment

    International Nuclear Information System (INIS)

    We investigated a new phenomenon of three-dimensional (3D) magnetic reconnection in TS-4 torus plasma merging experiments by directly measuring the 3D structures of the current sheet. Removal of all toroidal asymmetry of the device reveals that a strong external drive of reconnection inflow increases the toroidal asymmetry of the current sheet only during the reconnection. This spontaneous 3D deformation of the current sheet increases the reconnection outflow as well as the reconnection electric field, probably because local compression of the current sheet to a thickness less than the ion gyroradius triggers its strong dissipation of the current sheet, responsible for the onset of 3D reconnection. These mechanisms indicate that the 3D reconnection is a newly observed spontaneous process of fast reconnection.

  10. EPISODIC X-RAY EMISSION ACCOMPANYING THE ACTIVATION OF AN ERUPTIVE PROMINENCE: EVIDENCE OF EPISODIC MAGNETIC RECONNECTION

    International Nuclear Information System (INIS)

    We present an X-ray imaging and spectroscopic study of a partially occulted (N16W93) C7.7 flare on 2003 April 24 observed by Reuven Ramaty High Energy Solar Spectroscopy Imager that accompanied a prominence eruption observed by Transition Region and Coronal Explorer. (1) The activation and rise of the prominence occurs during the preheating phase of the flare. The initial X-ray emission appears as a single coronal source at one leg of the prominence and it then splits into a double source. Such a source splitting happens three times, each coinciding with an increased X-ray flux and plasma temperature, suggestive of fast reconnection in a localized current sheet and an enhanced energy-release rate. In the late stage of this phase, the prominence displays a helical structure. These observations are consistent with the tether-cutting and/or kink-instability model for triggering solar eruptions. (2) The eruption of the prominence takes place during the flare impulsive phase. Since then, there appear signatures predicted by the classical model of two-ribbon flares occurring in a vertical current sheet trailing an eruption. These signatures include an extreme-ultraviolet (EUV) cusp and current-sheet-like feature (or ridge) above it. There is also X-ray emission along the EUV ridge both below and above the cusp, which in both regions appears closer to the cusp at higher energies in the thermal regime (?47 cm-3), and a harder nonthermal spectrum (electron power-law index ? = 5.4 ± 0.4 vs. 8 ± 1) than the upper sources.

  11. Bidirectional jet formation during driven magnetic reconnection in two-beam laser-plasma interactions

    International Nuclear Information System (INIS)

    Measurements of the bidirectional plasma jets that form at the surface of a solid target during a laser-generated driven magnetic reconnection are presented. Resistivity enhancement of at least 25x the classical Spitzer value is required when applying the Sweet-Parker model of reconnection to reconcile the experimentally observed reconnection time scale. Analytic calculations show that a fast reconnection model, which includes a priori the effects of microturbulent resistivity enhancement, better reproduces the experimental observations.

  12. Acceleration of Energetic Particles through Reconnection of Weakly Stochastic Magnetic Field

    OpenAIRE

    Lazarian, A.; Kowal, G.; Pino, E. de Gouveia Dal; Vishniac, E.

    2012-01-01

    Astrophysical media are turbulent and therefore reconnection should be treated in the presence of pre-existing turbulence. We consider the model of fast magnetic reconnection in Lazarian & Vishniac (1999) which predicts that the rate of reconnection is controlled by the intensity and the injection scale of turbulent motions. We provide new evidence of successful testing of the model and argue that the model presents a generic set up for astrophysical reconnection events. We study particle acc...

  13. Relativistic Electron Acceleration Associated with Magnetic Reconnection

    Science.gov (United States)

    Coroniti, F. V.; Pritchett, P. L.

    2008-12-01

    Recent in-situ observations from the Wind and Cluster spacecraft have provided detailed information regarding the energetic electron spectrum near reconnection X lines. The Wind [Oieroset et al., 2002] data showed power law spectra with the hardest spectrum and highest electron flux near the center of the diffusion region. The Cluster data found that the electron energy spectrum became harder in the downstream region [Imada et al., 2007] and found a direct correlation between the enhanced electron fluxes and density spikes and bipolar Bz signatures [Chen et al., 2008], suggesting a direct link to the presence of magnetic islands. The mechanisms for the production of relativistic electrons are investigated using 2D particle-in-cell simulations which are initiated with a 10-island configuration with and without an initial guide field. Significant energization occurs only when the number of islands is reduced to two or three with wavelength satisfying kx L energies at the X line by the inductive electric field. The second stage is associated with the final coalescence into one large island and produces a considerably larger number of relativistic electrons. With a guide field, this stage is dominated by the formation of elongated density cavities along one pair of separatrices and continued direct acceleration at the X line. Without the guide field, the direct X line acceleration becomes unimportant, and the acceleration is localized in the flux pile-up regions [Hoshino et al., 2001] and results from the curvature drift interacting with the localized inductive electric field. Thus the presence or absence of a guide field may explain the different in-situ observations. In either case, some 15-20% of the decrease in magnetic field energy is transferred to the electrons, with a few percent appearing in relativistic (> 150 keV) electrons.

  14. Helicity, Topology and Kelvin Waves in reconnecting quantum knots

    CERN Document Server

    di Leoni, P Clark; Brachet, M E

    2016-01-01

    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 and solar physics, in fluid dynamics, in atmospheric sciences, and in 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 vortex lines can be downright impossible to apply in complex and turbulent scenarios. We present a new definition of helicity which overcomes these problems. With it, we show that only certain reconnection events conserve helicity. In other cases helicity can change abruptly during reconnection. Furthermore, we show that these events can also excite Kelvin waves, which slowly deplete helicity as they interact nonlinearly, thus linking the theory of vortex knots with observations of quantum turbulence.

  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. Magnetic Reconnection by a Self-Retreating X-Line

    CERN Document Server

    Oka, M; Nakamura, T K M; Shinohara, I; Nishikawa, K -I

    2008-01-01

    Particle-in-cell (PIC) simulations of collisionless magnetic reconnection are performed to study asymmetric reconnection in which an outflow is blocked by a hard wall while leaving sufficiently large room for the outflow of the opposite direction. This condition leads to a slow, roughly constant motion of the diffusion region away from the wall, the so-called `X-line retreat'. The typical retreat speed is ~0.1 times the Alfven speed. At the diffusion region, ion flow pattern shows strong asymmetry and the ion stagnation point and the X-line are not collocated. A surprise, however, is that the reconnection rate remains the same unaffected by the retreat motion.

  17. Relativistic Magnetic Reconnection in Pair Plasmas and Its Astrophysical Applications

    Science.gov (United States)

    Kagan, D.; Sironi, L.; Cerutti, B.; Giannios, D.

    2015-10-01

    This review discusses the physics of magnetic reconnection—a process in which the magnetic field topology changes and magnetic energy is converted to kinetic energy—in pair plasmas in the relativistic regime. We focus on recent progress in the field driven by theory advances and the maturity of particle-in-cell codes. This work shows that fragmentation instabilities at the current sheet can play a critical role in setting the reconnection speed and affect the resulting particle acceleration, anisotropy, bulk flows, and radiation. Then, we discuss how this novel understanding of relativistic reconnection can be applied to high-energy astrophysical phenomena, with an emphasis on pulsars, pulsar wind nebulae, and active galactic nucleus jets.

  18. Relativistic magnetic reconnection in pair plasmas and its astrophysical applications

    CERN Document Server

    Kagan, Daniel; Cerutti, Benoit; Giannios, Dimitrios

    2014-01-01

    This review discusses the physics of magnetic reconnection, a process in which the magnetic field topology changes and magnetic energy is converted to kinetic energy, in pair plasmas in the relativistic regime. We focus on recent progress in the field driven by theory advances and the maturity of particle-in-cell codes. This work shows that fragmentation instabilities at the current sheet can play a critical role in setting the reconnection speed and affect the resulting particle acceleration, anisotropy, bulk flows, and radiation. Then, we discuss how this novel understanding of relativistic reconnection can be applied to high-energy astrophysical phenomena, with an emphasis on pulsars, pulsar wind nebulae, and active galactic nucleus jets.

  19. Collisionless magnetic reconnection associated with coalescence of flux bundles

    International Nuclear Information System (INIS)

    The basic process of collisionless reconnection is studied in terms of coalescence of magnetized flux bundles using an implicit particle simulation of two-dimensions. The toroidal electric field that directly relates to magnetic reconnection is generated solenoidally in a region much broader than the current sheet whose width is a few electron skin depths. The reconnected flux increases linearly in time, but it is insensitive to finite Larmor radii of the ions in this Sweet-Parker regime. The toroidal electric field is controlled by a balance of transit acceleration of finite-mass electrons and their removal by sub-Alfvenic E x B drift outflow. The simulation results supports the collisionless Ohm's law Et??eqJt with ?eq the inertia resistivity. (author)

  20. 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...

  1. Clock Angle Dependence of Magnetic Reconnection at Earth's Subsolar Magnetopause

    Science.gov (United States)

    Dorelli, J. C.; Raeder, J.

    2005-05-01

    We use global magnetohydrodynamics (MHD) simulations to investigate the clock angle dependence of magnetic reconnection at Earth's subsolar magnetopause. Under steady solar wind conditions, and when the plasma resistivity is constant, we find that reconnection occurs at the subsolar magnetopause via a flux pileup mechanism for both northward and southward interplanetary magnetic field (IMF) conditions. Magnetic energy accumulates upstream of a Sweet-Parker current sheet to accommodate the sub-Alfvénic magnetosheath flow, and the upstream plasma density decreases (forming a plasma depletion layer) in order to satisfy momentum conservation. We argue, therefore, that in the context of resistive MHD, plasma depletion upstream of the magnetopause is a signature of magnetic flux pileup reconnection which occurs at the subsolar magnetopause under both northward and southward IMF conditions. We discuss the implications of these results for the "component" vs. "antiparallel" merging debate as well as for the interpretation of spacecraft observations of the plasma depletion layer.

  2. Numerical simulation of reconnection in an emerging magnetic flux region

    Science.gov (United States)

    Forbes, T. G.; Priest, E. R.

    1984-01-01

    Numerical solutions in two dimensions are presented for the resistive MHD equations of an initial boundary value problem, simulating reconnection between an emerging magnetic flux region and an overlying coronal magnetic field. This numerical model displays four main phases, which are interpreted in terms of (1) a slowly evolving quasi-steady phase during which most of the magnetic flux emerges, with approximate equilibrium between magnetic and pressure forces; (2) an impulsive phase in which either the reconnection or continuing emergence of the first phase comes to disrupt the equilibrium, and extensive acceleration occurs as the high pressure region within the emerging region drives the fluid upwards and outwards; (3) a second quasi-steady phase; and (4) a potential-static phase in which continuing reconnection, ohmic dissipation, and fluid transport through boundaries depletes the system of all currents and flows.

  3. Turbulence, Reconnection and Cosmic Rays in Galaxy Clusters

    CERN Document Server

    Lazarian, A

    2011-01-01

    Recent years have been marked by substantial changes in our understanding of magnetic turbulence and magnetic reconnection, which, in its turn induced better understanding of cosmic ray diffusion and acceleration. Current models of magnetized turbulence are no more ad hoc constructions, but numerically tested theories. In this very short review we summarize topics presented in two talks given at the conference and provide a brief sketch of the vast and rapidly developing field. We discuss how turbulence decreases the efficient mean free path of the particles in the collisionless plasmas in galaxy clusters and claim that this makes MHD turbulence description applicable to a wider range of scales. We discuss the properties of MHD turbulence and its relation to magnetic reconnection. Finally, we overview how turbulence induces particle acceleration via second order Fermi process and affects first order Fermi acceleration in shocks and reconnection regions.

  4. 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.

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

    International Nuclear Information System (INIS)

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

  6. Turbulent Magnetohydrodynamic Reconnection Mediated by the Plasmoid Instability

    Science.gov (United States)

    Huang, Yi-Min; Bhattacharjee, A.

    2016-02-01

    It has been established that the Sweet–Parker current layer in high Lundquist number reconnection is unstable to the super-Alfvénic plasmoid instability. Past two-dimensional magnetohydrodynamic simulations have demonstrated that the plasmoid instability leads to a new regime where the Sweet–Parker current layer changes into a chain of plasmoids connected by secondary current sheets, and the averaged reconnection rate becomes nearly independent of the Lundquist number. In this work, a three-dimensional simulation with a guide field shows that the additional degree of freedom allows plasmoid instabilities to grow at oblique angles, which interact and lead to self-generated turbulent reconnection. The averaged reconnection rate in the self-generated turbulent state is of the order of a hundredth of the characteristic Alfvén speed, which is similar to the two-dimensional result but is an order of magnitude lower than the fastest reconnection rate reported in recent studies of externally driven three-dimensional turbulent reconnection. Kinematic and magnetic energy fluctuations both form elongated eddies along the direction of the local magnetic field, which is a signature of anisotropic magnetohydrodynamic turbulence. Both energy fluctuations satisfy power-law spectra in the inertial range, where the magnetic energy spectral index is in the range from ?2.3 to ?2.1, while the kinetic energy spectral index is slightly steeper, in the range from ?2.5 to ?2.3. The anisotropy of turbulence eddies is found to be nearly scale-independent, in contrast with the prediction of the Goldreich–Sridhar theory for anisotropic turbulence in a homogeneous plasma permeated by a uniform magnetic field.

  7. Color reconnection and flow-like patterns in pp collisions

    International Nuclear Information System (INIS)

    Data collected at the LHC are confronted with the possible existence of flow in pp collisions. Here we present a study inside the framework of PYTHIA 8, showing that it contains implicit flow-like effects coming from multiple hard subcollisions and color string formation between initial and final partons from independent hard scatterings: color reconnection. We present studies with strange hadron observables in pp collisions at 7 TeV. Studies have been done both for minimum bias and multiplicity intervals in events with and without color reconnection to isolate the flow-like effect

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

    International Nuclear Information System (INIS)

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

  9. Electron acceleration by magnetic reconnection during spherical tokamak merging experiment

    International Nuclear Information System (INIS)

    Electron acceleration in magnetic reconnection event has been experimentally investigated using the plasma merging technique in the University of Tokyo Spherical Tokamak (UTST) device. Intense emission of He II line (468.58nm) was observed only in the vicinity of the X-point by using a multi-channel spectroscopic measurement system. This localized emission indicates the generation of energetic electrons inside the current sheet region, possibly due to the electron acceleration by the strong toroidal electric field induced by magnetic reconnection in the presence of a guide field. (author)

  10. Reconnection voltage as a function of IMF clock angle

    Science.gov (United States)

    Fedder, J. A.; Mobarry, C. M.; Lyon, J. G.

    1991-01-01

    Magnetic reconnection between the IMF and the geomagnetic field is thought to play a major role in the transfer of solar wind momentum and energy to the magnetosphere. Both analytic modeling and analysis of geophysical data have shown that this coupling process should be a sensitive function of the clock angle of the IMF. Results are presented from a three-dimensional, MHD, global numerical simulation code for the reconnection voltage between the closed geomagnetic field and the IMF as a function of the IMF clock angle. These results are consistent with a sin(theta/2) functional behavior.

  11. A Design Study of a New Magnetic Reconnection Experiment, MITPX

    Science.gov (United States)

    Montag, P.; Egedal, J.; Porkolab, M.; Le, A.; Vrublevskis, A.; Ohia, O.

    2011-10-01

    A new model for effective heating of electrons during reconnection is now gaining support from spacecraft observations, theoretical considerations and kinetic simulations. The key ingredient in the model is the physics of trapped electrons whose dynamics causes the electron pressure tensor to be strongly anisotropic. The heating mechanism becomes highly efficient for geometries with low upstream electron pressure; conditions relevant to the magnetotail. We propose a new Magnetic Interaction Toroidal Plasma Experiment (MITPX) that will be optimized for the study of kinetic reconnection including the dynamics of trapped electrons and pressure anisotropy.

  12. 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 transferred into the system. We conclude that Mercury's magnetosphere is a dynamic environment with constant plasma and magnetic flux circulation as a result of frequent and intense magnetic reconnection. These results are directly applicable to the understanding of geomagnetic storms at Earth, when coronal mass ejections produce solar wind parameters similar to those regularly experienced by Mercury.

  13. An Electromagnetic Drift Instability In the Lower Hybrid Frequency Range In Reconnection Region

    Science.gov (United States)

    Ji, H.; Kulsrud, R.; Fox, W.; Yamada, M.

    2004-12-01

    By using a local two-fluid theory, we investigate an electromagnetic instability in the lower hybrid frequency range driven by cross-field current or relative drifts between electrons and ions. The theory self-consistently takes into account local cross-field current and accompanying pressure gradients. It is found that the instability is caused by reactive coupling between backward propagating whistler (fast) waves and forward propagating sound (slow) waves when the relative drifts are large. The unstable waves have mixed polarization with significant electromagnetic components, propagating obliquely to the unperturbed magnetic field. A physical picture of the instability emerges as a result of further simplifications of the model. The primary feedback mechanism is based on reinforcement of initial electron density perturbations by induced Lorentz force due to both field line bending and (de)compression. The resultant waves are qualitatively consistent with the measured electromagnetic fluctuations in reconnecting current sheet in a laboratory plasma. Detailed wave characteristics are also similar to measurements at reconnection sites of the magnetosphere. This work is supported by DOE, NASA, and NSF.

  14. RECONNECTION OF QUASI-SINGULAR CURRENT SHEETS: THE ''IDEAL'' TEARING MODE

    International Nuclear Information System (INIS)

    A strong indication that fast reconnection regimes exist within resistive magnetohydrodynamics was given by the proof that the Sweet-Parker current sheet, maintained by a flow field with an appropriate inflow-outflow structure, could be unstable to a reconnecting instability which grows without bound as the Lundquist number, S, tends to infinity. The requirement of a minimum value for S in order for the plasmoid instability to kick in does little to resolve the paradoxical nature of the result. Here we argue against the realizability of Sweet-Parker current sheets in astrophysical plasmas with very large S by showing that an ''ideal'' tearing mode takes over before current sheets reach such a thickness. While the Sweet-Parker current sheet thickness scales as ?S –1/2, the tearing mode becomes effectively ideal when a current sheet collapses to a thickness of the order of ?S –1/3, up to 100 times thicker than S –1/2, when (as happens in many astrophysical environments) S is as large as 1012. Such a sheet, while still diffusing over a very long time, is unstable to a tearing mode with multiple x-points: here we detail the characteristics of the instability and discuss how it may help solve the flare trigger problem and effectively initiate the turbulent disruption of the sheet

  15. Strategic floodplain reconnection for the Lower Tisza River, Hungary: Opportunities for flood-height reduction and floodplain-wetland reconnection

    Science.gov (United States)

    Guida, Ross J.; Swanson, Taylor L.; Remo, Jonathan W. F.; Kiss, Timea

    2015-02-01

    During the late 19th Century, the Tisza River's vast floodplain-wetland system was largely disconnected by levees, facilitating "reclamation" for agriculture and resulting in an estimated loss of over 90% of historical wetlands. While levees have been successful in preventing catastrophic flooding for a century, Lower Tisza flood stage records have been set repeatedly during the last 15 years. The decrease in the Tisza's current floodway carrying capacity has reduced the flood-protection level of the Tisza's aging levee system. Recently in Hungary, "Room for the River" policies have gained more prominence. To explore the possibilities of a room for the river approach along the Lower Tisza, we assess eight potential floodplain-reconnection scenarios between Csongrád, Hungary and the Hungary-Serbia border. A novel framework using hydrodynamic and geospatial modeling was used to perform planning-level evaluations of the tradeoffs between floodplain-reconnection scenarios and enhancement of the existing levee system. The scenarios evaluated include levee removal and levee setbacks to strategically reconnect significant historical wetlands while reducing flood levels. Scenario costs and human population impacts are also assessed. Impacts of reconnecting the Lower Tisza floodplain are compared to heightening levees, the prevailing strategy over the previous century. From a purely construction-cost perspective, heightening Lower Tisza levees is potentially the most cost-effective and politically expedient solution (i.e., impacts the least number of people). However, levee-heightening does not solve the long-term problem of reduced flood conveyance, which has been attributed to aggradation and increased floodplain roughness, nor does it result in wetland reconnection or enhancement of other floodplain ecosystem services. The suite of reconnection options we evaluate provides engineers, planners, and decision makers a framework from which they can further evaluate potential flood-risk reduction options. At least three of the eight reconnection scenarios (setting the western levee back, 1500-m, and 2000-m setbacks) along the Lower Tisza demonstrate that floodplain-wetland reconnection is possible while achieving the objectives of minimizing impacts on human populations and reducing flood heights.

  16. Ion and Electron Heating Characteristics of Magnetic Reconnection in a Two Flux Loop Merging Experiment

    International Nuclear Information System (INIS)

    Characteristics of the high-power reconnection heating were measured for the first time directly by two-dimensional measurements of ion and electron temperatures. While electrons are heated mainly inside the current sheet by the Ohmic heating power, ions are heated mainly by fast shock or viscosity damping of the reconnection outflow in the two downstream areas. The magnetic reconnection converts the energy of reconnecting magnetic field Bp mostly to the ion thermal energy, indicating that the reconnection heating energy is proportional to Bp2.

  17. Assessing the validity of the maximum magnetic shear model to predict the dayside reconnection location

    Science.gov (United States)

    Trattner, Karlheinz

    2014-05-01

    Reconnection at the Earth's magnetopause is the mechanism by which magnetic fields in different regions change topology to create open magnetic field lines that allow energy and momentum to flow into the magnetosphere. One of the long standing questions about magnetic reconnection is the location of the reconnection line. There are two reconnection scenarios discussed in the literature: a) anti-parallel reconnection where shear angles between the magnetospheric field and the interplanetary magnetic field (IMF) are near 180°, and b) component reconnection where a tilted reconnection line which crosses the magnetopause in the sub-solar region at shear angles not near 180°. Early satellite observations were limited to the detection of accelerated ion beams in the magnetopause boundary layer to determine the general direction of the reconnection line location with respect to the satellite. An improved view of the reconnection location at the magnetopause was determined from ionospheric emissions observed by polar-orbiting imagers which revealed that both scenarios occur. The time-of-flight effect of precipitating ions in the cusp in connection with the low-velocity cutoff method pin-pointed reconnection locations and their dependency on IMF conditions. These results are summarized by the Maximum Magnetic Shear Model. This study will discuss recent investigations to test the validity of the predictions from the Maximum Magnetic Shear model. Several multi-spacecraft studies at the magnetopause showed an excellent agreement between the predicted and observed location of the reconnection line, especially under dominant IMF BY conditions.

  18. Energy transfer by magnetopause reconnection and the substorm parameter epsilon

    International Nuclear Information System (INIS)

    An expression for the magnetopause reconnection power based on the dawn-dusk component of the reconnection electric field, that reduces to the substorm parameter epsilon for the limit that involves equal geomagnetic (B sub(G)) and magnetosheath (B sub(M)) magnetic field amplitudes at the magnetopause, is contrasted with the expression based on the whole reconnection electric field vector obtained by Gonzalez. The correlation examples of this report show that this (more general) expression for the reconnection power seems to correlate with the empirical dissipation parameter U sub(T) from Akasofu, with slightly better correlation coefficients than those obtained from similar correlations between the parameter epsilon and U sub(T). Thus, these (better) correlations show up for the more familiar values of the ratio B sub(G) / B sub(M) > 1. Nevertheless, the (expected) relatively small difference that seems to exist between these correlation coefficients suggests that, for practical purposes, the parameter epsilon could be used as well (instead of the more general expression) in similar correlation studies due to its impler format. On the other hand, studies that refer mainly to the difference in the magnitudes of epsilon and of the more general expression are expected to give results with less negligible differences. (Author)

  19. Three-Dimensional Turbulent Reconnection Induced by the Plasmoid Instability

    Science.gov (United States)

    Huang, Yi-Min; Bhattacharjee, Amitava

    2014-10-01

    It has been established that the Sweet-Parker current layer in high Lundquist number (S) reconnection is unstable to the super-Alfvenic plasmoid instability. Past two-dimensional (2D) magnetohydrodynamic simulations have demonstrated that the plasmoid instability leads to a new regime where the Sweet-Parker current layer changes into a chain of plasmoids connected by secondary current sheets, and the averaged reconnection rate becomes nearly independent of S. In a three-dimensional (3D) configuration with a guide field, the additional degree of freedom allows plasmoid instabilities to grow at oblique angles [Baalrud et al., Phys. Plasmas 19, 022101 (2012)] and develop complex dynamics of flux ropes, which may be viewed as a self-generated turbulent state. In our 3D simulations, kinematic and magnetic energy fluctuations are observed to form cigar-shaped eddies elongated along the direction of local magnetic field, which is a signature of anisotropic MHD turbulence. Additionally, the energy fluctuation spectra are found to satisfy power laws in the inertial range. The characteristics of this self-generated turbulent reconnection are compared with corresponding 2D simulations of the same configuration, as well as turbulent reconnection driven by an external forcing.

  20. Magnetic reconnection in the solar atmosphere: from proposal to paradigm

    Science.gov (United States)

    Cargill, Peter; Parnell, Clare; Browning, Philippa; de Moortel, Ineke; Hood, Alan

    2010-06-01

    MEETING REPORT On 13 November 2009, the RAS hosted a discussion meeting to commemorate the formal retirement of Prof. Eric Priest. Here Peter Cargill, Clare Parnell, Philippa Browning, Ineke de Moortel and Alan Hood examine how magnetic reconnection has evolved over the past 50 years from an important but controversial proposal, to a general paradigm.

  1. 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.

  2. 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))

    1992-01-01

    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.

  3. Design of a Magnetic Reconnection Experiment in the Collisionless Regime

    Science.gov (United States)

    Egedal, Jan; Le, A.; Montag, P.; Ohia, O.; Vrublevskis, A.; Daughton, W.

    2012-10-01

    A new model for effective heating of electrons during reconnection is now gaining support from spacecraft observations, theoretical considerations and kinetic simulations [1]. The key ingredient in the model is the physics of trapped electrons whose dynamics causes the electron pressure tensor to be strongly anisotropic [2]. The heating mechanism becomes highly efficient for geometries with low upstream electron pressure, conditions relevant to the magnetotail. We propose a new experiment that will be optimized for the study of kinetic reconnection including the dynamics of trapped electrons and associated pressure anisotropy. This requires an experiment that accesses plasmas with much lower collisionality and lower plasma beta than are available in present reconnection experiments. The new experiment will be designed such that a large variety of magnetic configurations can be established and tailored for continuation of our ongoing study of spontaneous 3D reconnection [3]. The flexible design will also allow for configurations suitable for the study of merging magnetic islands, which may be a source of super thermal electrons in naturally occurring plasmas. [1ex] [1] J Egedal et al., Nature Physics, 8, 321 (2012).

  4. Evolution of field line helicity during magnetic reconnection

    International Nuclear Information System (INIS)

    We investigate the evolution of field line helicity for magnetic fields that connect two boundaries without null points, 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 connectivity 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 complex magnetic field, the evolution of field line helicity is dominated by a work-like term that is evaluated at the field line endpoints, namely, the scalar product of the generalized field line velocity and the vector potential. Furthermore, the flux integral of this term over certain areas is very small compared to the integral of the unsigned quantity, which indicates that changes of field line helicity happen in a well-organized pairwise manner. It follows that reconnection is very efficient at redistributing helicity in complex magnetic fields despite having little effect on the total helicity

  5. 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.

  6. Design of a Magnetic Reconnection Experiment in the Collisionless Regime

    Science.gov (United States)

    Egedal, J.; Le, A.; Daughton, W. S.

    2012-12-01

    A new model for effective heating of electrons during reconnection is now gaining support from spacecraft observations, theoretical considerations and kinetic simulations [1]. The key ingredient in the model is the physics of trapped electrons whose dynamics causes the electron pressure tensor to be strongly anisotropic [2]. The heating mechanism becomes highly efficient for geometries with low upstream electron pressure, conditions relevant to the magnetotail. We propose a new experiment that will be optimized for the study of kinetic reconnection including the dynamics of trapped electrons and associated pressure anisotropy. This requires an experiment that accesses plasmas with much lower collisionality and lower plasma beta than are available in present reconnection experiments. The new experiment will be designed such that a large variety of magnetic configurations can be established and tailored for continuation of our ongoing study of spontaneous 3D reconnection [3]. The flexible design will also allow for configurations suitable for the study of merging magnetic islands, which may be a source of super thermal electrons in naturally occurring plasmas. [1] Egedal J et al., Nature Physics, 8, 321 (2012). [2] Le A et al., Phys. Rev. Lett. 102, 085001 (2009). [3] Katz N et al., Phys. Rev. Lett. 104, 255004 (2010).;

  7. Study of Local Reconnection Physics in a Laboratory Plasma

    International Nuclear Information System (INIS)

    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

  8. 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.

  9. 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...

  10. 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...

  11. 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...

  12. 3-D, Impulsive Magnetic Reconnection in a Laboratory Plasma (Invited)

    Science.gov (United States)

    Dorfman, S. E.; Ji, H.; Yamada, M.; Yoo, J.; Myers, C. E.; Roytershteyn, V.; Daughton, W. S.; Jara-Almonte, J.

    2013-12-01

    Magnetic reconnection is a fundamental plasma process involving the efficient conversion of magnetic field energy to plasma kinetic energy through changing field line topology. In many space and astrophysical systems, including the solar surface and the Earth's magnetotail, reconnection is not only fast, but also impulsive; in other words, a slow buildup phase is followed by a comparatively quick release of magnetic energy. An important question in the literature is if these examples of impulsive reconnection can be described by a two-dimensional model with no variation in the out-of-plane direction or if impulsive reconnection is fundamentally three-dimensional. Events observed on the Magnetic Reconnection Experiment (MRX) are characterized by large local gradients in the third direction and cannot be explained by 2-D models [1]. Detailed measurements show that the ejection of flux rope structures from the current sheet plays a key role in these events. By contrast, even though electromagnetic fluctuations in the lower hybrid frequency range are also observed concurrently with the impulsive behavior, they are not the key physics responsible. Furthermore, an important discrepancy in the layer width and force balance between the collisionless regime of MRX and kinetic simulations [2-4] persists when the fluctuations are small or absent, implying that they are not the cause of the wider electron layers observed in the experiment [5]. These wider layers may instead be due to the formation of flux ropes with a wide range of sizes; consistent with this hypothesis, flux rope signatures are observed down to the smallest scales resolved by the diagnostics. Finally, a qualitative, 3-D, two-fluid model is proposed to explain the observed disruptions. Many of the features observed in MRX including current disruptions [6], flux ropes [7], and electromagnetic fluctuations [8] have analogues in space observations. Thus, further detailed comparisons may enhance our understanding of space and astrophysical plasmas where impulsive reconnection occurs. In particular, this work has relevance to the upcoming Magnetospheric Multiscale (MMS) Mission which aims to understand how electron scale structure may affect the global reconnection process. [1] S. Dorfman, et. al., Geophys. Res. Lett. 40, 233-238 (2013). [2] S. Dorfman, et. al., Phys. Plasmas 15, 102107 (2008). [3] H. Ji, et. al., Geophys. Res. Lett., 35, L13106 (2008). [4] V. Roytershteyn, et. al., Phys. Plasmas 17, 055706 (2010). [5] V. Roytershteyn, et. al., Phys. Plasmas 20, 061212 (2013). [6] S. Ohtani, et. al., J. Geophys. Res., 97(A12), 19311-19324 (1992). [7] J. P. Eastwood, et. al., J. Geophys. Res., 112, A06235 (2007). [8] J. S. Pickett, et. al., J. Geophys. Res., 106(A9), 19081-19099 (2001).

  13. Place Branding in Systems of Place

    DEFF Research Database (Denmark)

    Zenker, Sebastian; Andéhn, Mikael

    The pervasive managerial logic of branding has established a stable foothold in the context of place management. Yet the question of whether places, such as cities, regions and nations, can be effectively managed using marketing techniques remains elusive, as place brands and company brands have...... system 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...

  14. Place Branding in Systems of Place

    DEFF Research Database (Denmark)

    Zenker, Sebastian; Andéhn, Mikael

    The pervasive managerial logic of branding has established a stable foothold in the context of place management. Yet the question of whether places, such as cities, regions and nations, can be effectively managed using marketing techniques remains elusive, as place brands and company brands have...... – like a city, region or nation brand – is per definition attached to a system of geographical abstractions in quasi-cartographic form in which each city, region or nation is understood in relation and contrast to other geographical entities. For those who seek to alter perceptions about a place, this...

  15. 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.

    2015-01-01

    Microgrids can operate in both grid-connected and islanded modes. In order to seamlessly transfer from islanded to grid-connected modes, it is necessary to synchronize microgrid voltage, frequency and phase to the main grid. However, since the microgrid is often based on power electronics 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 structure. Real-time hardware-in-the-loop results show the feasibility of the proposed technique.

  16. Transience and Place: Exploring Tourists' Experiences of Place

    Directory of Open Access Journals (Sweden)

    Jens Kristian Steen Jacobsen

    1998-02-01

    Full Text Available This paper explores tourists' transient place experiences. The focus is on what is commonly called sightseeing, confined mainly to experiences of locations not previously visited. This type of travel experience, seeing actual places or objects for one's self and taking photographs, is regarded here as an important ritual in modernity. With reference to the concept of adventurer, the paper attempts to describe various aspects of novel travel experiences. For instance, ephemeral tourist sensations of place are compared to «love at first sight», a blissful experience of meeting with a place to which one feels strongly attracted. While transient encounters may also provide access to dreamlike place experiences, adventurous tourists are always in danger of being caught up in other roles, or of becoming embroiled in a new everyday life with accompanying routines. By way of conclusion, it is proposed that the restrictions on time inherent in today's holiday tours usually result in transient place experiences as the only alternative for those desiring to gain first-time impressions of several places or larger geographic areas.

  17. Putting Place Value in Its Place

    Science.gov (United States)

    Thompson, Ian

    2003-01-01

    In this article, the author explores the concept of "moving one place to the left." A recent investigation by Thompson and Bramald explored the relationship between young children's understanding of place value and their ability to add two-digit numbers. The study took the form of a series of one-to-one interviews with a sample of 144 children…

  18. Transient and intermittent magnetic reconnections in TS-3/UTST merging startup experiments

    International Nuclear Information System (INIS)

    The high-power reconnection heating has been developed in the TS-3 merging experiments, leading us to a new pulsed high-beta spherical tokamak (ST) formation. Two ST plasmas were produced inductively by two or four PF coils without using any central solenoid (CS) coil and were merged together for MW-GW reconnection heating. The magnetic reconnection transformed the magnetic energy of reconnecting magnetic field through the outflow kinetic energy finally to the ion thermal energy, increasing the plasma beta of ST up to 0.5. A new finding is that ejection of current sheet (or plasmoid) causes high-speed merging/ reconnection as well as high-power heating. In the high-q ST merging, the sheet resistivity was almost classical due to the sheet thickness much longer than ion gyroradius. Large inflow flux and low current-sheet dissipation resulted in flux pileup followed by rapid growth of the current sheet. When the flux pileup exceeded a critical limit, the sheet was ejected mechanically from the squeezed X-point area. The reconnection (outflow) speed was slow during the flux pileup and was fast during the ejection, indicating that intermittent reconnection similar to the solar flare increased the averaged reconnection speed. These transient effects enable us to have the fast reconnection as well as the high-power reconnection heating, even if the merging high-q tokamaks have low current-sheet resistivity. (author)

  19. 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 physical and emotional employers ( to do perfect job all the well being. time B. Avoiding pitfalls: by identifying 3. Long hours of stressful work knee jerks habits and negative attitudes

  20. How Does the Electron Dynamics Affect the Global Reconnection Rate

    Science.gov (United States)

    Hesse, Michael

    2012-01-01

    The question of whether the microscale controls the macroscale or vice-versa remains one of the most challenging problems in plasmas. A particular topic of interest within this context is collisionless magnetic reconnection, where both points of views are espoused by different groups of researchers. This presentation will focus on this topic. We will begin by analyzing the properties of electron diffusion region dynamics both for guide field and anti-parallel reconnection, and how they can be scaled to different inflow conditions. As a next step, we will study typical temporal variations of the microscopic dynamics with the objective of understanding the potential for secular changes to the macroscopic system. The research will be based on a combination of analytical theory and numerical modeling.

  1. 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.

  2. Fast magnetic reconnection due to anisotropic electron pressure

    International Nuclear Information System (INIS)

    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

  3. The dayside reconnection voltage applied to Saturn's magnetosphere

    Science.gov (United States)

    Masters, A.

    2015-04-01

    The ability of magnetic reconnection between interplanetary and planetary magnetic fields to drive a planetary magnetosphere can be quantified as the resulting voltage applied to the system. We present analytical model predictions of the dayside reconnection voltage at Saturn, a planet where solar wind driving has been the subject of debate. Model-predicted voltages are in reasonable agreement with adapted terrestrial coupling function estimates, as well as voltages inferred from auroral observations. The voltage is most sensitive to the interplanetary magnetic field (IMF). Combining the model with Cassini IMF observations suggests that the voltage is rarely high enough to compete with internal driving of Saturn's outer magnetosphere. The long-term average dayside (and nightside) voltage is ~40 kV. We point out that the distribution of IMF strength at Saturn is not bimodal, despite the compression-rarefaction structure of the local heliosphere when the Cassini observations were made.

  4. Ion temperature anisotropy across a magnetotail reconnection jet

    Science.gov (United States)

    Hietala, H.; Drake, J. F.; Phan, T. D.; Eastwood, J. P.; McFadden, J. P.

    2015-09-01

    A significant fraction of the energy released by magnetotail reconnection appears to go into ion heating, but this heating is generally anisotropic. We examine ARTEMIS dual-spacecraft observations of a long-duration magnetotail exhaust generated by antiparallel reconnection in conjunction with particle-in-cell simulations, showing spatial variations in the anisotropy across the outflow far (>100di) downstream of the X line. A consistent pattern is found in both the spacecraft data and the simulations: While the total temperature across the exhaust is rather constant, near the boundaries Ti,|| dominates. The plasma is well above the firehose threshold within patchy spatial regions at |BX|?[0.1,0.5]B0, suggesting that the drive for the instability is strong and the instability is too weak to relax the anisotropy. At the midplane (|BX|?0.1B0), Ti,?>Ti,|| and ions undergo Speiser-like motion despite the large distance from the X line.

  5. 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...

  6. Turbulence, Magnetic Reconnection in Turbulent Fluids and Energetic Particle Acceleration

    CERN Document Server

    Lazarian, A; Kowal, G; Yan, H; Beresnyak, A; Pino, E de Gouveia Dal

    2012-01-01

    Turbulence is ubiquitous in astrophysics. It radically changes many astrophysical phenomena, in particular, the propagation and acceleration of cosmic rays. We present the modern understanding of compressible magnetohydrodynamic (MHD) turbulence, in particular its decomposition into Alfv\\'en, slow and fast modes, discuss the density structure of turbulent subsonic and supersonic media, as well as other relevant regimes of astrophysical turbulence. All this information is essential for understanding the energetic particle acceleration that we discuss further in the review. For instance, we show how fast and slow modes accelerate energetic particles through the second order Fermi acceleration, while density fluctuations generate magnetic fields in pre-shock regions enabling the first order Fermi acceleration of high energy cosmic rays. Very importantly, however, the first order Fermi cosmic ray acceleration is also possible in sites of magnetic reconnection. In the presence of turbulence this reconnection gets ...

  7. Electron Temperature Fluctuations Associated with High Temperature Reconnecting Modes

    Science.gov (United States)

    Basu, B.; Coppi, B.; Montag, P.

    2014-10-01

    Experimental observations and theoretical considerations indicate that, in high temperature plasmas, the value of the perpendicular electron thermal conductivity is relatively large and its effects can compete with those of the parallel thermal conductivity in the theory of reconnecting modes. These effects are taken into account in the relevant expression for the electron thermal energy balance equation. Then the equations for high temperature reconnecting modes are derived and solved showing how limited the applicability of the linearized theory of drift tearing modes is to explain current experimental observations. Electrostatic modes that can be excited in the presence of resistivity gradients are also investigated. When the electron drift wave frequency becomes important, no radially localized unstable mode of this kind can be found with or without the combined effects of trapped electrons and weak collisionality. Sponsored in part by U.S. DOE.

  8. Application of Stereo Vision to the Reconnection Scaling Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Klarenbeek, Johnny [Los Alamos National Laboratory; Sears, Jason A. [Los Alamos National Laboratory; Gao, Kevin W. [Los Alamos National Laboratory; Intrator, Thomas P. [Los Alamos National Laboratory; Weber, Thomas [Los Alamos National Laboratory

    2012-08-14

    The measurement and simulation of the three-dimensional structure of magnetic reconnection in astrophysical and lab plasmas is a challenging problem. At Los Alamos National Laboratory we use the Reconnection Scaling Experiment (RSX) to model 3D magnetohydrodynamic (MHD) relaxation of plasma filled tubes. These magnetic flux tubes are called flux ropes. In RSX, the 3D structure of the flux ropes is explored with insertable probes. Stereo triangulation can be used to compute the 3D position of a probe from point correspondences in images from two calibrated cameras. While common applications of stereo triangulation include 3D scene reconstruction and robotics navigation, we will investigate the novel application of stereo triangulation in plasma physics to aid reconstruction of 3D data for RSX plasmas. Several challenges will be explored and addressed, such as minimizing 3D reconstruction errors in stereo camera systems and dealing with point correspondence problems.

  9. 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.

  10. Comparative Analysis of Dayside Reconnection Models in Global Magnetosphere Simulations

    CERN Document Server

    Komar, C M; Cassak, P A

    2015-01-01

    We test and compare a number of existing models predicting the location of magnetic reconnection at Earth's dayside magnetopause for various solar wind conditions. We employ robust image processing techniques to determine the locations where each model predicts reconnection to occur. The predictions are then compared to the magnetic separators, the magnetic field lines separating different magnetic topologies. The predictions are tested in distinct high-resolution simulations with interplanetary magnetic field (IMF) clock angles ranging from 30 to 165 degrees in global magnetohydrodynamic simulations using the three-dimensional Block-Adaptive Tree Solarwind Roe-type Upwind Scheme (BATS-R-US) code with a uniform resistivity, although the described techniques can be generally applied to any self-consistent magnetosphere code. Additional simulations are carried out to test location model dependence on IMF strength and dipole tilt. We find that most of the models match large portions of the magnetic separators wh...

  11. 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 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 discrepanc...

  12. Extreme ultraviolet imaging of three-dimensional magnetic reconnection in a solar eruption

    Science.gov (United States)

    Sun, J. Q.; Cheng, X.; Ding, M. D.; Guo, Y.; Priest, E. R.; Parnell, C. E.; Edwards, S. J.; Zhang, J.; Chen, P. F.; Fang, C.

    2015-06-01

    Magnetic reconnection, a change of magnetic field connectivity, is a fundamental physical process in which magnetic energy is released explosively, and it is responsible for various eruptive phenomena in the universe. However, this process is difficult to observe directly. Here, the magnetic topology associated with a solar reconnection event is studied in three dimensions using the combined perspectives of two spacecraft. The sequence of extreme ultraviolet images clearly shows that two groups of oppositely directed and non-coplanar magnetic loops gradually approach each other, forming a separator or quasi-separator and then reconnecting. The plasma near the reconnection site is subsequently heated from ~1 to >=5 MK. Shortly afterwards, warm flare loops (~3 MK) appear underneath the hot plasma. Other observational signatures of reconnection, including plasma inflows and downflows, are unambiguously revealed and quantitatively measured. These observations provide direct evidence of magnetic reconnection in a three-dimensional configuration and reveal its origin.

  13. Statistical study of magnetic cloud erosion by magnetic reconnection

    Science.gov (United States)

    Ruffenach, A.; Lavraud, B.; Farrugia, C. J.; Démoulin, P.; Dasso, S.; Owens, M. J.; Sauvaud, J.-A.; Rouillard, A. P.; Lynnyk, A.; Foullon, C.; Savani, N. P.; Luhmann, J. G.; Galvin, A. B.

    2015-01-01

    recent studies suggest that magnetic reconnection is able to erode substantial amounts of the outer magnetic flux of interplanetary magnetic clouds (MCs) as they propagate in the heliosphere. We quantify and provide a broader context to this process, starting from 263 tabulated interplanetary coronal mass ejections, including MCs, observed over a time period covering 17 years and at a distance of 1 AU from the Sun with Wind (1995-2008) and the two STEREO (2009-2012) spacecraft. Based on several quality factors, including careful determination of the MC boundaries and main magnetic flux rope axes, an analysis of the azimuthal flux imbalance expected from erosion by magnetic reconnection was performed on a subset of 50 MCs. The results suggest that MCs may be eroded at the front or at rear and in similar proportions, with a significant average erosion of about 40% of the total azimuthal magnetic flux. We also searched for in situ signatures of magnetic reconnection causing erosion at the front and rear boundaries of these MCs. Nearly ~30% of the selected MC boundaries show reconnection signatures. Given that observations were acquired only at 1 AU and that MCs are large-scale structures, this finding is also consistent with the idea that erosion is a common process. Finally, we studied potential correlations between the amount of eroded azimuthal magnetic flux and various parameters such as local magnetic shear, Alfvén speed, and leading and trailing ambient solar wind speeds. However, no significant correlations were found, suggesting that the locally observed parameters at 1 AU are not likely to be representative of the conditions that prevailed during the erosion which occurred during propagation from the Sun to 1 AU. Future heliospheric missions, and in particular Solar Orbiter or Solar Probe Plus, will be fully geared to answer such questions.

  14. Reconnection studies under different types of turbulence driving

    Directory of Open Access Journals (Sweden)

    G. Kowal

    2012-04-01

    Full Text Available We study a model of fast magnetic reconnection in the presence of weak turbulence proposed by Lazarian and Vishniac (1999 using three-dimensional direct numerical simulations. The model has been already successfully tested in Kowal et al. (2009 confirming the dependencies of the reconnection speed Vrec on the turbulence injection power Pinj and the injection scale linj expressed by a constraint Vrec ~ Pinj1/2linj3/4and no observed dependency on Ohmic resistivity. In Kowal et al. (2009, in order to drive turbulence, we injected velocity fluctuations in Fourier space with frequencies concentrated around kinj = 1/linj, as described in Alvelius (1999. In this paper, we extend our previous studies by comparing fast magnetic reconnection under different mechanisms of turbulence injection by introducing a new way of turbulence driving. The new method injects velocity or magnetic eddies with a specified amplitude and scale in random locations directly in real space. We provide exact relations between the eddy parameters and turbulent power and injection scale. We performed simulations with new forcing in order to study turbulent power and injection scale dependencies. The results show no discrepancy between models with two different methods of turbulence driving exposing the same scalings in both cases. This is in agreement with the Lazarian and Vishniac (1999 predictions. In addition, we performed a series of models with varying viscosity ?. Although Lazarian and Vishniac (1999 do not provide any prediction for this dependence, we report a weak relation between the reconnection speed with viscosity, Vrec ~ ??1/4.

  15. 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.

  16. 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.

  17. Multiscale study of electron energization during unsteady reconnection events

    Science.gov (United States)

    Ashour-Abdalla, Maha; Lapenta, Giovanni; Walker, Raymond J.; El-Alaoui, Mostafa; Liang, Haoming

    2015-06-01

    Understanding particle acceleration in the magnetotail during substorms requires knowledge of changes in the global magnetospheric configuration and the local regions of intense fields and microinstabilities caused by processes associated with reconnection. We simulated a substorm on 15 February 2008 by coupling the University of California, Los Angeles global magnetohydrodynamic simulation code and a two-dimensional version of the iPIC3D implicit particle-in-cell code. The MHD code provides realistic initial and boundary conditions for the particle-in-cell (PIC) code, while the PIC code models the reconnection and evolution of the dipolarization front (DF) self-consistently with full kinetic physics. In the PIC simulation, after a few seconds, an active X point forms and DF-like structures form about every 2 s and propagate earthward. In the near-Earth tail, the earthward moving fronts combine to form thicker structures. The presence of the macroscopic-scale magnetic field, featuring a significant dipolar component nearer the Earth, affects the reconnection process, chocking the flow that cannot freely propagate earthward, causing the production of multiple repeating DFs. In the region away from the equator and equatorward of the separatrices, the DFs become associated with a series of spatial stripes that are visible in the electron temperature and the magnetic and electric fields and are also caused by the unsteady nature of the process of reconnection. The electrons are preferentially accelerated in the dipolarization region in the extension of the dipolarization field lines to high latitudes and reach energies of 100 keV or more. A streaming instability may be responsible for the parallel acceleration. This acceleration of the plasma associated with the DFs is greater than that occurring near the X point for this substorm.

  18. Colour annealing - a toy model of colour reconnections

    International Nuclear Information System (INIS)

    We present a simple toy model for colour reconnections at the nonperturbative level. The model resembles an annealing-type algorithm and is applicable to any collider and process type, though we argue for a possible enhancement of the effect in hadron-hadron collisions. We present a simple application and study of the consequences for semileptonic t(bar t) events at the Tevatron

  19. Application of PDSLin to the magnetic reconnection problem

    International Nuclear Information System (INIS)

    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. (paper)

  20. The Mechanisms of Electron Heating and Acceleration during Magnetic Reconnection

    CERN Document Server

    Dahlin, J T; Swisdak, M

    2014-01-01

    The heating of electrons in collisionless magnetic reconnection is explored in particle-in-cell (PIC) simulations with non-zero guide fields so that electrons remain magnetized. In this regime electric fields parallel to B accelerate particles directly while those perpendicular to B do so through gradient-B and curvature drifts. The curvature drift drives parallel heating through Fermi reflection while the gradient B drift changes the perpendicular energy through betatron acceleration. We present simulations in which we evaluate each of these mechanisms in space and time in order to quantify their role in electron heating. For a case with a small guide field (20 % of the magnitude of the reconnecting component) the curvature drift is the dominant source of electron heating. However, for a larger guide field (equal to the magnitude of the reconnecting component) electron acceleration by the curvature drift is comparable to that of the parallel electric field. In both cases the heating by the gradient B drift i...

  1. Collisionless reconnection in Jupiter's magnetotail

    Energy Technology Data Exchange (ETDEWEB)

    Zimbardo, G. (Univ. ' della Calabria (Italy))

    1991-04-01

    The authors present the first quantitative study of collisionless reconnection in Jupiter's magnetotail. Recently it has been shown that collisionless reconnection can occur in the Earth's magnetotail quasi-neutral sheet when the electrons are subject to chaotic pitch angle diffusion. This happens when the curvature parameter K{sub e} = B{sub z}/B{sub 0}(L{sub z}/{rho}{sub e0}){sup 1/2} decreases to {approximately} 1.6. For Jupiter's magnetotail, a self-consistent axisymmetric equilibrium model is used to compute the magnetic field and K{sub e}, and it is found that the condition for electron chaotization is satisfied in a region large enough to allow the growth of a tearing instability. The favorite site for reconnection is situated at about 60 R{sub j}, and the growth time is estimated to be about 370 s, i.e., much shorter than the plasma transit time through the chaotization region. The inductive e.m.f. along a 20 R{sub j} X line is estimated to be of order 100 kV - 1 MV, and should accelerate the ions dawnward and the electrons duskward.

  2. Observation of reconnection pulses by Cluster and Double Star

    Directory of Open Access Journals (Sweden)

    X. H. Deng

    2005-11-01

    Full Text Available During a reconnection event on 7 August 2004, Cluster and Double Star (TC-1 were near the neutral sheet and simultaneously detected the signatures of the reconnection pulses. AT 22:59 UT tailward flow followed by earthward flow was detected by Cluster at about 15 RE, while earthward plasma flow followed by tailward flow was observed by TC-1 at about 10 RE. During the flow reversal from tailward to earthward, the magnetic field Bz changed sign from mainly negative values to positive, and the X component of the magnetic curvature vector switched sign from the tailward direction to the earthward direction, which indicates that the reconnection site (X-line moved tailward past the Cluster constellation. By using multi-point analysis and observation of energetic electron and ion flux, we study the movement and structure of the current sheet and discuss the braking effect of the earthward flow bursts in the inner magnetosphere.

  3. 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.

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

    Science.gov (United States)

    Baty, Hubert; Nishikawa, Hiroaki

    2016-03-01

    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.

  5. Magnetic topology change induced by reconnection events in RFP plasmas

    Science.gov (United States)

    Momo, Barbara; Martines, Emilio; Innocente, Paolo; Lorenzini, Rita; Rea, Cristina; Zanca, Paolo; Zuin, Matteo

    2014-10-01

    Magnetic reconnection is a phenomena observed in various plasmas across the Universe, where a conversion of magnetic to kinetic energy of plasma particles is consequent to a change in the global magnetic topology. In laboratory plasmas magnetic reconnections are associated to relaxation processes, like sawtooth crashes in Tokamak dynamics and the so-called dynamo effect in Reversed Filed Pinches (RFPs). In this work we propose the study of magnetic crashes in RFP dynamics, where the recursive transition from a more ordered helical state to a chaotic one is associated with rapid magnetic reconnection events. More into details, we propose to analyse RFX-mod discharges reconstructing the magnetic topology in the whole plasma volume at fixed time snapshots. Times are chosen in a window around the crashes, and the magnetic topology is reconstructed by using the solutions of a Newcomb-type equation, solved consistently with experimental boundary conditions. New boundary conditions are given by internal magnetic measurements coming from the ISIS probe system, in order to detect high frequency dynamics. Poincaré plots are used as a tool for the visualization of magnetic topology changes.

  6. AN ANALYTICAL MODEL FOR RECONNECTION OUTFLOW JETS INCLUDING THERMAL CONDUCTION

    International Nuclear Information System (INIS)

    We develop a model that predicts the velocity, density, and temperature of coronal reconnection jets in the presence of thermal conduction. Our model is based on the quasi-one-dimensional treatment of reconnecting current sheets developed by B. Somov and V. S. Titov using the magnetohydrodynamics nozzle equations. We incorporate thermal conduction into the Somov-Titov framework using slow-shock jump conditions modified to include losses due the conduction of thermal energy along field lines mapping to the chromosphere. We find that thermal conduction has a significant effect on the fast-mode Mach number of the reconnection outflow, producing Mach numbers possibly as high as 7 for some solar-flare conditions. This value is three times greater than previously calculated. We conclude that these termination shocks are considerably more efficient at producing particle acceleration than previously thought since the efficiency of particle acceleration at shocks increases dramatically with Mach number. We compare this model with numerical simulations by T. Yokoyama and K. Shibata and find good agreement.

  7. Interchange reconnection between an active region and a coronal hole

    International Nuclear Information System (INIS)

    With data from the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory, we present a magnetic interaction between an isolated coronal hole (CH) and an emerging active region (AR). The AR emerged nearby the CH and interacted with it. Bright loops constantly formed between them, which led to a continuous retreat of the CH boundaries (CHBs). Meanwhile, two coronal dimmings respectively appeared at the negative polarity of the AR and the east boundary of the bright loops, and the AR was partly disturbed. Loop eruptions followed by a flare occurred in the AR. The interaction was also accompanied by many jets and an arc-shaped brightening that appeared to be observational signatures of magnetic reconnection at the CHBs. By comparing the observations with the derived coronal magnetic configuration, it is suggested that the interaction between the CH and the AR excellently agreed with the model of interchange reconnection. It appears that our observations provide obvious evidence for interchange reconnection

  8. ``Complex Reconnecting'' Modes and Critical Direction of their Propagation

    Science.gov (United States)

    Buratti, P.; Coppi, B.; Pucella, G.

    2014-10-01

    Experiments in weakly collisional plasma regimes (e.g. neutral beam heated plasmas in the H-regime), measuring the Doppler shift associated with the plasma local rotation, have shown that the direction of the propagation of the observed reconnected structures in the frame with Er = 0 is in the direction of the ion diamagnetic velocity. This is contrary to the direction of the phase velocity of the ``drift-tearing'' modes found originally in the Ref.. Consequently, the theory of ``Complex Reconnecting'' Modes has been developed that include the effects finite ion gyro radius, finite ion transverse viscosity, finite longitudinal electron pressure and magnetic diffusion coefficient. Thus modes are found with very low values of the growth rate, a phase velocity about equal the ion diamagnetic velocity that is consistent with recent experimental observations, and widths of the reconnection layer larger than the ion gyro radius. Another option involves assuming the presence of a plasma inductivity in the electron momentum conservation equation. Sponsored in part by the US Department of Energy.

  9. Electron Heating During Magnetic Reconnection: A Simulation Scaling Study

    CERN Document Server

    Shay, M A; Phan, T D; Drake, J F; Cassak, P A; Wu, P; Oieroset, M; Swisdak, M; Malakit, K

    2014-01-01

    Electron bulk heating during magnetic reconnection with symmetric inflow conditions is examined using kinetic particle-in-cell (PIC) simulations. The degree of electron heating is well correlated with the inflowing Alfv\\'en speed $c_{Ar}$ based on the reconnecting magnetic field through the relation $\\Delta T_e = 0.033 \\,m_i\\,c_{Ar}^2$, where $\\Delta T_{e}$ is the increase in electron temperature. For the range of simulations performed, the heating shows almost no correlation with inflow total temperature $T_{tot} = T_i + T_e$ or plasma $\\beta$. An out-of-plane (guide) magnetic field of similar magnitude to the reconnecting field does not affect the total heating, but it does quench perpendicular heating, with almost all heating being in the parallel direction. These results are qualitatively consistent with a recent statistical survey of electron heating in the dayside magnetopause, which also found that $\\Delta T_e$ was proportional to the inflowing Alfv\\'en speed. The net electron heating varies very littl...

  10. Intermittent bursts induced by double tearing mode reconnection

    International Nuclear Information System (INIS)

    Reversed magnetic shear (RMS) configuration is assumed to be the steady-state operation scenario for the future advanced tokamaks like International Thermonuclear Experimental Reactor. In this work, we numerically discover a phenomenon of violent intermittent bursts induced by self-organized double tearing mode (DTM) reconnection in the RMS configuration during the very long evolution, which may continuously lead to annular sawtooth crashes and thus badly impact the desired steady-state operation of the future advanced RMS tokamaks. The key process of the intermittent bursts in the off-axis region is similar to that of the typical sawtooth relaxation oscillation in the positive magnetic shear configuration. It is interestingly found that in the decay phase of the DTM reconnection, the zonal field significantly counteracts equilibrium field to make the magnetic shear between the two rational surfaces so weak that the residual self-generated vortices of the previous DTM burst are able to trigger a reverse DTM reconnection by curling the field lines

  11. Intermittent bursts induced by double tearing mode reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Lai; Wang, Zheng-Xiong, E-mail: zxwang@dlut.edu.cn [Key Laboratory of Materials Modification by Beams of the Ministry of Education, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

    2014-06-15

    Reversed magnetic shear (RMS) configuration is assumed to be the steady-state operation scenario for the future advanced tokamaks like International Thermonuclear Experimental Reactor. In this work, we numerically discover a phenomenon of violent intermittent bursts induced by self-organized double tearing mode (DTM) reconnection in the RMS configuration during the very long evolution, which may continuously lead to annular sawtooth crashes and thus badly impact the desired steady-state operation of the future advanced RMS tokamaks. The key process of the intermittent bursts in the off-axis region is similar to that of the typical sawtooth relaxation oscillation in the positive magnetic shear configuration. It is interestingly found that in the decay phase of the DTM reconnection, the zonal field significantly counteracts equilibrium field to make the magnetic shear between the two rational surfaces so weak that the residual self-generated vortices of the previous DTM burst are able to trigger a reverse DTM reconnection by curling the field lines.

  12. Particle Acceleration and Plasma Dynamics during Magnetic Reconnection in the Magnetically-dominated Regime

    OpenAIRE

    Guo, Fan; Liu, Yi-Hsin; Daughton, William; Hui LI

    2015-01-01

    Magnetic reconnection is thought to be the driver for many explosive phenomena in the universe. The energy release and particle acceleration during reconnection have been proposed as a mechanism for producing high-energy emissions and cosmic rays. We carry out two- and three-dimensional kinetic simulations to investigate relativistic magnetic reconnection and the associated particle acceleration. The simulations focus on electron-positron plasmas starting with a magnetically...

  13. Observational Signatures of Simulated Reconnection Events in the Solar Chromosphere and Transition Region

    OpenAIRE

    Heggland, L.; De Pontieu, B.; Hansteen, V.H.

    2009-01-01

    We present the results of numerical simulations of wave-induced magnetic reconnection in a model of the solar atmosphere. In the magnetic field geometry we study in this article, the waves, driven by a monochromatic piston and a driver taken from Hinode observations, induce periodic reconnection of the magnetic field, and this reconnection appears to help drive long-period chromospheric jets. By synthesizing observations for a variety of wavelengths that are sensitive to a wide range of tempe...

  14. Numerical Simulation of Superhalo Electrons Generated by Magnetic Reconnection in the Solar Wind Source Region

    OpenAIRE

    Yang, L. -P.; Wang, L. -H.; He, J. -S.; Tu, C.-Y.; Zhang, S. -H.; L. Zhang; Feng, X. -S.

    2014-01-01

    Superhalo electrons appear to be continuously present in the interplanetary medium, even at very quiet times, with a power-law spectrum at energies above $\\sim$2 keV. Here we numerically investigate the generation of superhalo electrons by magnetic reconnection in the solar wind source region, using the MHD and test particle simulations for both single X-line reconnection and multiple X-line reconnection. We find that the direct current electric field, produced in the magnet...

  15. The location and rate of dayside reconnection during an interval of southward interplanetary magnetic field

    OpenAIRE

    Pinnock, M.; Chisham, G.; Coleman, I J; Freeman, M. P.; M. Hairston; J. -P. Villain

    2003-01-01

    Using ionospheric data from the SuperDARN radar network and a DMSP satellite we obtain a comprehensive description of the spatial and temporal pattern of day-side reconnection. During a period of southward interplanetary magnetic field (IMF), the data are used to determine the location of the ionospheric projection of the dayside magnetopause reconnection X-line. From the flow of plasma across the projected X-line, we derive the reconnection rate across 7 h of longitude and estimate it ...

  16. Some comments on transient and steady-state reconnection at the dayside magnetopause

    OpenAIRE

    Rodger, Alan S.; Coleman, Iain J.; Pinnock, Mike

    2000-01-01

    Reconnection at the dayside magnetopause is the principal method by which energy is transferred from the solar wind into the magnetosphere-ionosphere system. There is still considerable uncertainty as to whether reconnection is transient or quasi-steady. Here we discuss some of the implications of assuming that reconnection occurring in regions where the magnetosheath flow is super-Alfvénic must be transient. We use a simple magnetospheric model to illustrate where on the magnetopause transie...

  17. Ion and electron heating characteristics of magnetic reconnection in tokamak plasma merging experiments

    International Nuclear Information System (INIS)

    Recently, the TS-3 and TS-4 tokamak merging experiments revealed significant plasma heating during magnetic reconnection. A key question is how and where ions and electrons are heated during magnetic reconnection. Two-dimensional measurements of ion and electron temperatures and plasma flow made clear that electrons are heated inside the current sheet mainly by the Ohmic heating and ions are heated in the downstream areas mainly by the reconnection outflows. The outflow kinetic energy is thermalized by the fast shock formation and viscous damping. The magnetic reconnection converts the reconnecting magnetic field energy mostly to the ion thermal energy in the outflow region whose size is much larger than the current sheet size for electron heating. The ion heating energy is proportional to the square of the reconnection magnetic field component Bp2. This scaling of reconnection heating indicates the significant ion heating effect of magnetic reconnection, which leads to a new high-field reconnection heating experiment for fusion plasmas. (paper)

  18. Colour reconnection and Bose-Einstein studies with WW decays in ALEPH

    Science.gov (United States)

    Jones, R. W. L.

    1999-03-01

    The production of WW pairs at LEP allows interference effect between the hadronic systems of the two W bosons to be studied, such as Bose-Einstein interference and possible signatures or 'colour reconnection' have been investigated. As yet, ALEPH sees no compelling evidence for colour reconnection nor for Bose-Einstein interference between the W systems. In related studies of the predictions of various Monte Carlo models for colour reconnection effects, it is noted that there is no large multiplicity shift due to colour reconnection in the Herwig model when appropritely re-tuned to correctly described the Z data.

  19. Colour reconnection and Bose-Einstein studies with WW decays in ALEPH

    Energy Technology Data Exchange (ETDEWEB)

    Jones, R.W.L

    1999-03-01

    The production of WW pairs at LEP allows interference effect between the hadronic systems of the two W bosons to be studied, such as Bose-Einstein interference and possible signatures for 'colour reconnection' have been investigated. As yet, ALEPH sees no compelling evidence for colour reconnection nor for Bose-Einstein interference between the W systems. In related studies of the predictions of various Monte Carlo models for colour reconnection effects, it is noted that there is no large multiplicity shift due to colour reconnection in the Herwig model when appropriately re-tuned to correctly describe the Z data.

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

    Science.gov (United States)

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

    2015-05-01

    The Magnetosphere Multiscale Mission (MMS) will provide the first opportunity to probe electron-scale physics during magnetic reconnection in Earth's magnetopause and magnetotail. This article will address only tail reconnection—as a non-steady-state process in which the first reconnected field lines advance away from the x-point in flux pile-up fronts directed Earthward and anti-Earthward. An up-to-date microscopic physical picture of electron and ion-scale collisionless tail reconnection processes is presented based on 2-D Particle-In-Cell (PIC) simulations initiated from a Harris current sheet and on Cluster and Themis measurements of tail reconnection. The successes and limitations of simulations when compared to measured reconnection are addressed in detail. The main focus is on particle and field diffusion region signatures in the tail reconnection geometry. The interpretation of these signatures is vital to enable spacecraft to identify physically significant reconnection events, to trigger meaningful data transfer from MMS to Earth and to construct a useful overall physical picture of tail reconnection. New simulation results and theoretical interpretations are presented for energy transport of particles and fields, for the size and shape of electron and ion diffusion regions, for processes occurring near the fronts and for the {j} × {B} (Hall) electric field.

  1. Remote estimation of reconnection parameters in the Earth's magnetotail: model and observations

    Science.gov (United States)

    Alexandrova, A.; Nakamura, R.; Semenov, V. S.; Kubyshkin, I. V.; Apatenkov, S.; Panov, E. V.; Korovinskiy, D.; Biernat, H.; Baumjohann, W.; Glassmeier, K.-H.; McFadden, J. P.

    2012-12-01

    We develop a method to estimate the reconnected magnetic flux and the location of the reconnection site using properties of magnetic field and plasma velocity disturbances in the regions surrounding the reconnection plasma flow. Our analysis is based on a 3-D non-steady reconnection model with a finite-sized X-line length. In this framework, we obtain a system of equations capturing the relationships between the disturbances of the magnetic field and plasma flow from one side and the reconnection characteristics from another side. These equations allow us to determine the reconnection characteristics from one-point remote observations of the reconnection fast flow, propagated in the magnetotail current sheet. We apply the model to magnetic field and plasma observations at (-43, -11.2, -6.9) RE GSM obtained by the THEMIS/ARTEMIS spacecraft, located in the tail lobe during a substorm event. We found that the reconnection region was located at ~ (-27, 3.5, 0) RE GSM. The X-line appeared to be close to the local time of the substorm current wedge identified from ground-based observations. We estimated the total magnetic flux, which was reconnected in the event as ~5 MWb. That corresponds to a small fraction of the total amount of magnetic flux transferred during a substorm.

  2. A comparison of analytical and numerical models for steadily driven magnetic reconnection

    Science.gov (United States)

    Forbes, T. G.; Priest, E. R.

    1987-01-01

    The effect of boundary conditions in both analytical and numerical solutions of steadily driven reconnection on the reconnection of antiparallel magnetic fields is considered, with special attention given to the mathematical problem of properly specifying boundary conditions for the MHD equation. A unified formulation developed by Priest and Forbes (1986) for steady state reconnection, which includes the Petschek solution and the Sonnerup (1970) solution as special cases, is used to reinterpret the previous numerical experiments of steadily driven reconnection. It is shown that many contradictory features of these experiments were caused by the use of boundary conditions which are different from those required by Petschek's (1964) theory.

  3. Comparison of analytical and numerical models for steadily driven magnetic reconnection

    International Nuclear Information System (INIS)

    The effect of boundary conditions in both analytical and numerical solutions of steadily driven reconnection on the reconnection of antiparallel magnetic fields is considered, with special attention given to the mathematical problem of properly specifying boundary conditions for the MHD equation. A unified formulation developed by Priest and Forbes (1986) for steady state reconnection, which includes the Petschek solution and the Sonnerup (1970) solution as special cases, is used to reinterpret the previous numerical experiments of steadily driven reconnection. It is shown that many contradictory features of these experiments were caused by the use of boundary conditions which are different from those required by Petschek's (1964) theory. 117 references

  4. Defining and identifying three-dimensional magnetic reconnection in resistive magnetohydrodynamic simulations of Earth's magnetosphere

    International Nuclear Information System (INIS)

    Magnetic reconnection is thought to be the primary mode by which the solar wind couples to the terrestrial magnetosphere, driving phenomena such as magnetic storms and aurorae. While the theory of two-dimensional reconnection is well developed and has been applied with great success to axisymmetric and toroidal systems such as laboratory plasma experiments and fusion devices, it is difficult to justify the application of two-dimensional theory to nontoroidal plasma systems such as Earth's magnetosphere. Unfortunately, the theory of three-dimensional magnetic reconnection is much less well developed, and even defining magnetic reconnection has turned out to be controversial. In this paper, recent progress in the use of magnetohydrodynamics (MHD) to address the physics of three-dimensional reconnection in Earth's magnetosphere is reviewed. The paper consists of two parts. In the first part, various definitions of three-dimensional reconnection are reviewed, with the goal of mapping these definitions to sets of physical phenomena that have been identified as 'reconnection' in various contexts. In the second part of the paper, MHD simulation results for the magnetosphere are presented, and two qualitatively distinct types of reconnection phenomena are identified: (1) Steady separator reconnection under generic northward interplanetary magnetic field (IMF) conditions, involving plasma flow across magnetic separatrices, and (2) time-dependent reconnection under generic southward IMF conditions, involving a locally detectable change in the magnetic field topology. It is concluded that magnetic reconnection phenomena at Earth's dayside magnetopause are adequately captured by two distinct definitions: The Vasyliunas definition [V. M. Vasyliunas, Rev. Geophys 13, 303 (1975)], which identifies magnetic reconnection with plasma flow across magnetic separatrices, and the Greene definition [J. Greene, Phys. Fluids B 5, 2355 (1993)], which identifies magnetic reconnection with a violation of magnetic flux conservation. Further generalizations of the definition of magnetic reconnection - e.g., the Schindler-Hesse [K. Schindler and M. Hesse, J. Geophys. Res. 93, 5547 (1988)] definition, which identifies reconnection with spatially localized violations of ideal MHD - are, while potentially useful in characterizing reconnection phenomena in the absence of magnetic nulls, separators, or separatrices, unnecessary in the magnetospheric context

  5. Electron heating during magnetic reconnection: A simulation scaling study

    International Nuclear Information System (INIS)

    Electron bulk heating during magnetic reconnection with symmetric inflow conditions is examined using kinetic particle-in-cell simulations. Inflowing plasma parameters are varied over a wide range of conditions, and the increase in electron temperature is measured in the exhaust well downstream of the x-line. The degree of electron heating is well correlated with the inflowing Alfvén speed cAr based on the reconnecting magnetic field through the relation ΔTe=0.033 mi cAr2, where ΔTe is the increase in electron temperature. For the range of simulations performed, the heating shows almost no correlation with inflow total temperature Ttot=Ti+Te or plasma β. An out-of-plane (guide) magnetic field of similar magnitude to the reconnecting field does not affect the total heating, but it does quench perpendicular heating, with almost all heating being in the parallel direction. These results are qualitatively consistent with a recent statistical survey of electron heating in the dayside magnetopause (Phan et al., Geophys. Res. Lett. 40, 4475, 2013), which also found that ΔTe was proportional to the inflowing Alfvén speed. The net electron heating varies very little with distance downstream of the x-line. The simulations show at most a very weak dependence of electron heating on the ion to electron mass ratio. In the antiparallel reconnection case, the largely parallel heating is eventually isotropized downstream due a scattering mechanism, such as stochastic particle motion or instabilities. The simulation size is large enough to be directly relevant to reconnection in the Earth's magnetosphere, and the present findings may prove to be universal in nature with applications to the solar wind, the solar corona, and other astrophysical plasmas. The study highlights key properties that must be satisfied by an electron heating mechanism: (1) preferential heating in the parallel direction; (2) heating proportional to mi cAr2; (3) at most a weak dependence on electron mass; and (4) an exhaust electron temperature that varies little with distance from the x-line

  6. 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...

  7. 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...

  8. 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. PMID:12344988

  9. Analysis of Magnetic Reconnection Sequence: from 2d to 3d

    Science.gov (United States)

    Qiu, Jiong; Longcope, D. W.

    2009-05-01

    Magnetic reconnection, which governs explosive energy release in solar flares, is 3-dimensional by nature. One major challenge in the field has always been to find a useful quantitative description of observations that can relate to theoretic models of magnetic reconnection. In this study, we analyze the temporal and spatial evolution of UV ribbons of an X2.0 flare observed on 2004 November 7 to infer 3D evolution of magnetic reconnection in the corona. First, our analysis reveals macroscopically two distinctive stages of magnetic reconnection (e.g. Moore et al. 2001), namely parallel elongation and perpendicular expansion of flare ribbons with respect to the polarity inversion line (PIL). Elongation of flare ribbons along the PIL during the first stage proceeds at apparent maximum speeds comparable with the Alfven speed in the active region chromosphere, and the apparent perpendicular expansion speed is a fraction of the local Alfven speed. The two stages are also marked by a clear division in reconnection rate and energy release rate. Furthermore, we employ a new method, the reconnection sequence analysis, to determine the connectivity and reconnection flux during the flare between a dozen magnetic sources defined from partitioning the photospheric magnetogram. The method can pick up pairs of magnetic cells that are reconnecting in a sequential manner. The observationally derived reconnection sequence and cell-wise reconnection fluxes are compared with computations by a topological model of magnetic reconnection, yielding reasonable agreement. Such analysis produces physical quantities directly comparable with topological models, thus is promising to provide observational constraints to justify subsequent calculation of helicity transfer and energy release from the model. This work is supported by NSF grants ATM-0603789 and ATM-0748428 to Montana State University.

  10. 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.

  11. Place in Transition

    DEFF Research Database (Denmark)

    Mikkelsen, Jacob Bjerre; Lange, Ida Sofie Gøtzsche

    decommissioned, in the context of the North Sea no less than 600 oil rig structures are to be decommissioned within the next 30 years (Schmidt 2004), creating potentially transformable 'drosscapes' (Berger 2006). These structures are weaved into an enclosed network, an 'Oil World', inaccessible and disconnected...... from the 'Everyday World'. Within mobilities studies, research has focused on different aspects and consequences of the post-oil society (see Dennis & Urry 2009, Urry 2013). This paper discusses the conception of place within the enclosed 'Oil World' with point of departure in relocation and...... '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...

  12. Science takes time :families take time!

    OpenAIRE

    Hultberg, Kirsti Baird

    2000-01-01

    Who has time to have a family ? Scientists are the «heroes» of our time. Science takes time - Families take time. Who gives time ? My case -study consists of interviews with scientific workers of both sexes. They are asked how they juggle the time required in the production of scientific knowledge and family life. My findings indicate that it is women, who give of their time.

  13. Take Charge. Take the Test. PSA (:30)

    Centers for Disease Control (CDC) Podcasts

    2012-03-07

    As part of the Take Charge. Take the Test. campaign, this 30 second PSA encourages African American women to get tested for HIV. Locations for a free HIV test can be found by visiting hivtest.org/takecharge or calling 1-800-CDC-INFO (1-800-232-4636).  Created: 3/7/2012 by National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention (NCHHSTP).   Date Released: 3/7/2012.

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

    International Nuclear Information System (INIS)

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

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

    CERN Document Server

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

    2004-01-01

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

  16. Estimation of the magnetotail reconnection parameters from a remote lobe observation by ARTEMIS spacecraft

    Science.gov (United States)

    Alexandrova, A.; Nakamura, R.; Semenov, V.; Apatenkov, S.; Korovinskiy, D.; Biernat, H.; Baumjohann, W.; Sergeev, V.; Kiehas, S.; Angelopoulos, V.

    2012-04-01

    A method that estimates the reconnection parameters, such as the location of reconnection region and the reconnected magnetic flux, from the field and the flow disturbances in the lobe is applied for a substorm event on 15 February 2010 at 08:40 UT. The method is based on the time-dependent reconnection model considering a reconnection line with a finite length along the current direction and assumes that the disturbances associated with the reconnection propagate parallel to the current sheet with a constant Alfvén velocity. Using ARTEMIS observations, which showed characteristic variations of the magnetic field detected on probe P2 located at X= -43 RE, Y=-11.2 Re, and Z= -6.9 RE in GSM coordinates, we estimate the reconnection region to be located at X=-26.9 RE, Y=3.5 RE, and Z=0 RE. This is consistent with the local time of the current wedge that was reconstructed for the event using low latitude magnetogram data. The reconnected magnetic flux is obtained to be 4.1 - 5.3 MWb.

  17. On the magnetic reconnection of resistive tearing mode with the dynamic flow effects

    Energy Technology Data Exchange (ETDEWEB)

    Ali, A.; Li, Jiquan, E-mail: lijq@energy.kyoto-u.ac.jp; Kishimoto, Y. [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2015-04-15

    Magnetic reconnection usually occurs in turbulent environments, which may not only provide anomalous resistivity to enhance reconnection rates but also significantly modify the reconnection process through direct nonlinear interaction with magnetic islands. This study presents numerical simulations investigating the effects of an imposed dynamic flow on magnetic reconnection, based on a two-dimensional reduced resistive MHD model. Results show that while the linear stability properties of the resistive tearing mode are moderately affected by the dynamic flow, nonlinear evolution is significantly modified by radial parity, amplitude, and frequency of the dynamic flow. After the slowly evolving nonlinear Rutherford stage, the reconnection process is found to progress in two phases by including the dynamic flow. A Sweet-Parker like current sheet is formed in the first phase. Afterwards, plasmoid instability is triggered in the second phase, where multiple plasmoids are continuously generated and ejected along the current sheet, leading to an impulsive bursty reconnection. The reconnection rate is considerably enhanced in the range of low resistivity as compared to without flow. We found that plasmoid instability onset and evolution are strongly influenced by the frequency and radial parity of the dynamic flows. The scaling of effective reconnection rates with the flow is found to be independent of resistivity.

  18. 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 ? = –(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 + ? {sub c}/(8?{sub diff})), where ? {sub c}/?{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 ?{sub diff}/? {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 speed) spectra observed by Fisk and Gloeckler and Mewaldt et al.

  19. Particle Acceleration via Reconnection Processes in the Supersonic Solar Wind

    Science.gov (United States)

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

    2014-12-01

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

  20. The Onset of Magnetic Reconnection in the Solar Atmosphere

    Science.gov (United States)

    Evans, R. M.; Klimchuk, J. A.; van der Holst, B.

    2014-12-01

    A fundamental question concerning magnetic energy release on the Sun is why the release occurs only after substantial stresses have been built up in the field. If reconnection were to occur readily, then the released energy would be much less than the energy required for coronal heating, CMEs, flares, jets, spicules, etc. How can we explain this switch-on property? What is the physical nature of the onset conditions? One idea involves the secondary instability of current sheets, which switches on when the rotation of the magnetic field across a current sheet reaches a critical angle. Such conditions would occur at the boundaries of flux tubes that become tangled and twisted by turbulent photospheric convection, for example. Other ideas focus on a critical thickness for the current sheet. We report here on the preliminary results of our investigation of reconnection onset. Unlike our earlier work on the secondary instability (Dahlburg, Klimchuk, and Antiochos 2005), here we treat the coupled chromosphere-corona system. Using the BATS-R-US MHD code (Toth et al. 2012), we simulate a single current sheet in a sheared magnetic field that extends from the chromosphere into the corona. Driver motions are applied at the base of the model. The configuration and chromosphere are both idealized, but capture the essential physics of the problem. The advantage of this unique approach is that it resolves the current sheet to the greatest extent possible while maintaining a realistic solar atmosphere. It thus bridges the gap between reconnection in a box studies and studies of large-scale systems such as active regions. One question we will address is whether onset conditions are met first in the chromosphere or corona.

  1. Reconnection studies in a low-compression theta pinch

    International Nuclear Information System (INIS)

    Compact Toroids (CT) are produced in the High Beta Q Machine (HBQM) with lifetimes that depend on the time the separatrix closes on axis. At low filling pressures when this closure occurs during the first 5 ?sec of the discharge, the excluded-flux radius is nearly constant for 30 to 40 ?sec. At higher pressures when reconnection occurs after approximately 10 ?sec the excluded flux decays exponentially in 25 to 35 ?sec. In the latter case an open field line configuration persists longer and end-loss is more important. The discharge can operate reproducibly in either regime

  2. Reconnection processes and scaling laws in reversed field pinch magnetohydrodynamics

    International Nuclear Information System (INIS)

    Reversed field pinch (RFP) sustainment is studied in the framework of three dimensional magnetohydrodynamic (MHD) numerical simulations. The scaling law for the magnetic fluctuation amplitude with Lundquist number S is ?B approx. S-0.22, which can be understood if the basic dynamic processes are governed by current sheet reconnection. Quasi-periodic oscillations are in fact found to be correlated with the presence of localized sheet currents, which for sufficiently large S make the major contribution to the average power dissipated by fluctuations. Special attention is paid to numerical convergence in the simulations. The results are compared with experimental observations. (author). 30 refs, 10 figs

  3. 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.

  4. Structures of reconnection layers based on the ideal magnetohydrodynamic equations

    International Nuclear Information System (INIS)

    A Riemann solver is used, and a set of numerical simulations are performed, to study the structures of reconnection layers in the approximation of the one-dimensional ideal MHD equations. Since the Riemann solver may solve general Riemann problems, the model used in this paper is more general than those in previous investigations on this problem. Under the conditions used in the previous investigations, the structures we obtained are the same. Our numerical simulations show quantitative agreement with those obtained through the Riemann solver. (author)

  5. A Place for Painting

    OpenAIRE

    Siqueland, Andreas

    2013-01-01

    For the past three years I have been a research fellow at The Academy of Fine Art through the Norwegian Artistic Research Programme. This text accompanies the exhibition "A Box and a Picture" and the book "A Picture and Box",which mark the end of my research project "A Place for Painting". In my work I have been interested in understanding how different geographical places influence the painting process and what this implies for the construction of place i...

  6. 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...

  7. Fundamental role of ion viscosity on fast magnetic reconnection in large-guide-field regimes

    International Nuclear Information System (INIS)

    Nonlinear analytical theory of magnetic reconnection with a large guide field is presented for the first time. We confirm that two distinct steady-state reconnection regimes are possible depending on the relative size of the diffusion region thickness ? versus the sound gyroradius ?s. The reconnection is slow (Sweet-Parker-like) for ? > or approx. ?s, and fast otherwise. However, unlike earlier work, we find that ion viscosity ? plays a fundamental role in the fast regime. In particular, for ?s we obtain ??Ha-1, with Ha?1/?(??) as the Hartmann number, and the reconnection rate Ez?Pr-1/2, with Pr=?/? as the Prandtl number and ? as the resistivity. If the perpendicular ion viscosity is employed for ?, the reconnection rate becomes independent of plasma ? and collision frequencies, and therefore potentially fast.

  8. Extreme Ultraviolet Imaging of Three-dimensional Magnetic Reconnection in a Solar Eruption

    CERN Document Server

    Sun, J Q; Ding, M D; Guo, Y; Priest, E R; Parnell, C E; Edwards, S J; Zhang, J; Chen, P F; Fang, C

    2015-01-01

    Magnetic reconnection, a change of magnetic field connectivity, is a fundamental physical process in which magnetic energy is released explosively. It is responsible for various eruptive phenomena in the universe. However, this process is difficult to observe directly. Here, the magnetic topology associated with a solar reconnection event is studied in three dimensions (3D) using the combined perspectives of two spacecraft. The sequence of extreme ultraviolet (EUV) images clearly shows that two groups of oppositely directed and non-coplanar magnetic loops gradually approach each other, forming a separator or quasi-separator and then reconnecting. The plasma near the reconnection site is subsequently heated from $\\sim$1 to $\\ge$5 MK. Shortly afterwards, warm flare loops ($\\sim$3 MK) appear underneath the hot plasma. Other observational signatures of reconnection, including plasma inflows and downflows, are unambiguously revealed and quantitatively measured. These observations provide direct evidence of magneti...

  9. Ionospheric convection observed by SuperDARN during ongoing lobe reconnection revealed by Cluster .

    Science.gov (United States)

    Marcucci, M. F.; Amata, E.; Ambrosino, D.; Coco, I.; Bavassano Cattaneo, M. B.; Retinò, A.

    Since Dungey's work in the early sixties, who suggested that the interplanetary magnetic field and the geomagnetic field could reconnect, a lot of debate has been going on regarding how the reconnection process exactly occurs at the Earth's magnetopause. In fact, many fundamental questions remain unanswered, in particular regarding the shape and the extension of the reconnection sites for variable IMF orientation. The polar ionospheric convection strongly depends on the orientation of the IMF; such dependence can be explained in the framework of the reconnection between interplanetary and geomagnetic fields. Here we use SuperDARN observations of the ionospheric convection in coordination with space observations provided by the Cluster spacecraft to infer large scale configuration and evolution of the reconnection at the magnetopause during an extended period of Northward IMF.

  10. 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...

  11. On the Relation Between Reconnected Flux and Parallel Electric Fields in the Solar Corona

    Science.gov (United States)

    Johnson, J.; Hesse, M.; Forbes, T.; Birn, J.

    2004-12-01

    The complicated magnetic topology in the solar corona often does not lend itself to the ready differentiation of topologically different regions. Instead, magnetic reconnection often happens in coronal fields that do not vanish, and for which no separator or separatrix is readily identifiable. For this, rather generic, situation, the question of how to relate observed magnetic flux changes to parallel electric fields remains unanswered. In order to shed light on this question, we apply to this problem the theory of General Magnetic Reconnection. We prove that a unique relation exists between the time evolution of the reconnected magnetic flux on one hand, and the integral along magnetic field lines of the parallel electric field on the other. Furthermore, we will use two explicit examples to illustrate how parallel electric fields are related to the formation of closed loops by the reconnection process, and how flux rope-like topologies result from reconnection if photospheric electric fields are negligible on flare time scales.

  12. Role of Z-pinches in magnetic reconnection in space plasmas

    CERN Document Server

    Olshevsky, Vyacheslav; Markidis, Stefano; Divin, Andrey

    2015-01-01

    A widely accepted scenario of magnetic reconnection in collisionless space plasmas is the breakage of magnetic field lines in X-points. In laboratory, reconnection is commonly studied in pinches, current channels embedded into twisted magnetic fields. No model of magnetic reconnection in space plasmas considers both null-points and pinches as peers. We have performed a particle-in-cell simulation of magnetic reconnection in a three-dimensional configuration where null-points are present initially, and Z-pinches are formed during the simulation along the lines of spiral null-points. The non-spiral null-points are more stable than spiral ones, and no substantial energy dissipation is associated with them. On the contrary, turbulent magnetic reconnection in the pinches causes the magnetic energy to decay at a rate of ~1.5% per ion gyro period. Dissipation in similar structures is a likely scenario in space plasmas with large fraction of spiral null-points.

  13. Gaussian-Moment Relaxation Closures for Verifiable Numerical Simulation of Fast Magnetic Reconnection in Plasma

    CERN Document Server

    Johnson, Evan Alexander

    2014-01-01

    The motivating question for this dissertation was to identify the minimal requirements for fluid models of plasma to allow converged simulations that agree well with converged kinetic simulations of fast magnetic reconnection. We show that truncation closure for the deviatoric pressure or for the heat flux results in singularities. Due to the strong pressure anisotropies that arise, we study magnetic reconnection with a Gaussian-moment two-fluid MHD with isotropization of the pressure tensor. For the GEM magnetic reconnection challenge problem, our deviatoric pressure tensor agrees well with published kinetic simulations at the time of peak reconnection, but sometime thereafter the numerical solution becomes unpredictable and develops near-singularities that crash the simulation unless positivity limiters are applied. To explain these difficulties, we show that steady reconnection requires heat flux. Specifically, for two-dimensional problems invariant under 180-degree rotation about the X-point, entropy prod...

  14. Coalescence of magnetic flux ropes in the ion diffusion region of magnetic reconnection

    Science.gov (United States)

    Wang, Rongsheng; Lu, Quanming; Nakamura, Rumi; Huang, Can; Du, Aimin; Guo, Fan; Teh, Waileong; Wu, Mingyu; Lu, San; Wang, Shui

    2016-03-01

    Magnetic reconnection is an important process in space and laboratory plasmas that effectively converts magnetic energy into plasma kinetic energy within a current sheet. Theoretical work suggested that reconnection occurs through the growth and overlap of magnetic flux ropes that deconstruct magnetic surfaces in the current sheet and enable the diffusion of the magnetic field lines between two sides of the sheet. This scenario was also proposed as a primary mechanism for accelerating energetic particles during reconnection, but experimental evidence has remained elusive. Here, we identify a total of 19 flux ropes during reconnection in the magnetotail. We found that the majority of the ropes are embedded in the Hall magnetic field region and 63% of them are coalescing. These observations show that the diffusion region is filled with flux ropes and that their interaction is intrinsic to the reconnection dynamics, leading to turbulence.

  15. Plans, Takes, and Mis-takes

    Directory of Open Access Journals (Sweden)

    Nathaniel Klemp

    2008-04-01

    Full Text Available This paper analyzes what may have been a mistake bypianist Thelonious Monk playing a jazz solo in 1958.Even in a Monk composition designed for patternedmayhem, a note can sound out of pattern. We reframethe question of whether the note was a mistake and askinstead about how Monk handles the problem. Amazingly,he replays the note into a new pattern that resituatesits jarring effect in retrospect. The mistake, orbetter, the mis-take, was “saved” by subsequent notes.Our analysis, supported by reflections from jazz musiciansand the philosopher John Dewey, encourages areformulation of plans, takes, and mis-takes as categoriesfor the interpretation of contingency, surprise, andrepair in all human activities. A final section suggeststhat mistakes are essential to the practical plying andplaying of knowledge into performances, particularlythose that highlight learning.

  16. Recent developments in collisionless reconnection theory: Applications to laboratory and space plasmas

    International Nuclear Information System (INIS)

    Recent developments in the theory and simulation of nonlinear collisionless reconnection hold the promise for providing solutions to some outstanding problems in laboratory and space plasma physics. Examples of such problems are sawtooth oscillations in tokamaks, magnetotail substorms, and impulsive solar flares. In each of these problems, a key issue is the identification of fast reconnection rates that are insensitive to the mechanism that breaks field lines (resistivity and/or electron inertia). The classical models of Sweet-Parker and Petschek sought to resolve this issue in the realm of resistive magnetohydrodynamics (MHD). However, the plasmas mentioned above are weakly collisional, and hence obey a generalized Ohm's law in which the Hall current and electron pressure gradient terms play a crucial role. Recent theoretical models and simulations on impulsive (or triggered) as well as quasisteady reconnection governed by a generalized Ohm's law are reviewed. In the impulsive reconnection problem, not only is the growth rate fast but the time derivative of the growth rate changes rapidly. In the steady-state reconnection problem, explicit analytical expressions are obtained for the geometric characteristics (that is, length and width) of the reconnection layer and the reconnection rate. Analytical results are tested by Hall MHD simulations. While some of the geometric features of the reconnection layer and the weak dependence of the reconnection rate on resistivity are reminiscent of Petschek's classical model, the underlying wave and particle dynamics mediating the reconnection dynamics in the presence of the Hall current and electron pressure gradient are qualitatively different. Quantitative comparisons are made between theory and observations from laboratory as well as space plasmas

  17. Where is 'place' in Aging in place?

    DEFF Research Database (Denmark)

    Blaakilde, Anne Leonora

    The aim of this article is to contribute a transnational perspective to the field of environmental gerontology and the concept of aging in place. Seniors from the northern hemisphere, among them Danish citizens, are increasingly adapting to transnational lives as they move to warmer climates. Thi...... in-home help. It is argued that we should consider public solutions to the problems faced by frail Danish citizens in transnational settings, enhancing their opportunities to live abroad.......The aim of this article is to contribute a transnational perspective to the field of environmental gerontology and the concept of aging in place. Seniors from the northern hemisphere, among them Danish citizens, are increasingly adapting to transnational lives as they move to warmer climates. This...... article builds on a qualitative study among Danish retirement migrants regarding their experiences with the need for care or support while living abroad. Denmark is a welfare state with a long history of public nursing homes and in-home care for frail elderly persons. This system of governance is...

  18. 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.

  19. 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...

  20. Understanding Place Value

    Science.gov (United States)

    Cooper, Linda L.; Tomayko, Ming C.

    2011-01-01

    Developing an understanding of place value and the base-ten number system is considered a fundamental goal of the early primary grades. For years, teachers have anecdotally reported that students struggle with place-value concepts. Among the common errors cited are misreading such numbers as 26 and 62 by seeing them as identical in meaning,…