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  • 1.
    Aaboud, M.
    et al.
    Univ Adelaide, Dept Phys, Adelaide, Australia..
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Univ Chicago, Enrico Fermi Inst, Chicago, IL USA..
    Fluctuations of anisotropic flow in Pb plus Pb collisions at root s(NN)=5.02 TeV with the ATLAS detector2020In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 1, article id 51Article in journal (Refereed)
    Abstract [en]

    Multi-particle azimuthal cumulants are measured as a function of centrality and transverse momentum using 470 mu b(-1) of Pb+Pb collisions at root s(NN) = 5.02TeV with the ATLAS detector at the LHC. These cumulants provide information on the event-by-event fluctuations of harmonic flow coefficients v(n) and correlated fluctuations between two harmonics v(n) and v(m). For the first time, a non-zero four-particle cumulant is observed for dipolar flow, v(1). The four-particle cumulants for elliptic flow, v(2), and triangular flow, v(3), exhibit a strong centrality dependence and change sign in ultra-central collisions. This sign change is consistent with significant non-Gaussian fluctuations in v(2) and v(3). The four-particle cumulant for quadrangular flow, v(4), is found to change sign in mid-central collisions. Correlations between two harmonics are studied with three- and four-particle mixed-harmonic cumulants, which indicate an anti-correlation between v(2) and v(3), and a positive correlation between v(2) and v(4). These correlations decrease in strength towards central collisions and either approach zero or change sign in ultra-central collisions. To investigate the possible flow fluctuations arising from intrinsic centrality or volume fluctuations, the results are compared between two different event classes used for centrality definitions. In peripheral and mid-central collisions where the cumulant signals are large, only small differences are observed. In ultra-central collisions, the differences are much larger and transverse momentum dependent. These results provide new information to disentangle flow fluctuations from the initial and final states, as well as new insights on the influence of centrality fluctuations.

  • 2.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    Measurement of Azimuthal Anisotropy of Muons from Charm and Bottom Hadrons in pp Collisions at root s=13 TeV with the ATLAS Detector2020In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, no 8, article id 082301Article in journal (Refereed)
    Abstract [en]

    The elliptic flow of muons from the decay of charm and bottom hadrons is measured in pp collisions at root s = 13 TeV using a data sample with an integrated luminosity of 150 pb(-1) recorded by the ATLAS detector at the LHC. The muons from heavy-flavor decay are separated from light-hadron decay muons using momentum imbalance between the tracking and muon spectrometers. The heavy-flavor decay muons are further separated into those from charm decay and those from bottom decay using the distance-of-closest-approach to the collision vertex. The measurement is performed for muons in the transverse momentum range 4-7 GeV and pseudorapidity range vertical bar eta vertical bar < 2.4. A significant nonzero elliptic anisotropy coefficient nu(2) is observed for muons from charm decays, while the nu(2) value for muons from bottom decays is consistent with zero within uncertainties.

  • 3.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Phys Dept, Stockholm, Sweden..
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Phys Dept, Stockholm, Sweden..
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Phys Dept, Stockholm, Sweden..
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Phys Dept, Stockholm, Sweden..
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Phys Dept, Stockholm, Sweden..
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    Search for electroweak production of charginos and sleptons decaying into final states with two leptons and missing transverse momentum in root s=13 TeV pp collisions using the ATLAS detector2020In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 80, no 2, article id 123Article in journal (Refereed)
    Abstract [en]

    A search for the electroweak production of charginos and sleptons decaying into final states with two electrons or muons is presented. The analysis is based on 139 fb(-1) of proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider at v s = 13 TeV. Three R-parity-conserving scenarios where the lightest neutralino is the lightest supersymmetric particle are considered: the production of chargino pairs with decays via eitherW bosons or sleptons, and the direct production of slepton pairs. The analysis is optimised for the first of these scenarios, but the results are also interpreted in the others. No significant deviations from the Standard Model expectations are observed and limits at 95% confidence level are set on the masses of relevant supersymmetric particles in each of the scenarios. For a massless lightest neutralino, masses up to 420 GeV are excluded for the production of the lightest-chargino pairs assuming W-boson-mediated decays and up to 1 TeV for slepton-mediated decays, whereas for slepton-pair production masses up to 700 GeV are excluded assuming three generations of mass-degenerate sleptons.

  • 4.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    Z boson production in Pb plus Pb collisions at root S-NN=5.02 TeV measured by the ATLAS experiment2020In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 802, article id 135262Article in journal (Refereed)
    Abstract [en]

    The production yield of Z bosons is measured in the electron and muon decay channels in Pb+Pb collisions at /S-NN = 5.02 TeV with the ATLAS detector. Data from the 2015 LHC run corresponding to an integrated luminosity of 0.49 nb(-1) are used for the analysis. The Z boson yield, normalised by the total number of minimum-bias events and the mean nuclear thickness function, is measured as a function of dilepton rapidity and event centrality. The measurements in Pb+Pb collisions are compared with similar measurements made in proton-proton collisions at the same centre-of-mass energy. The nuclear modification factor is found to be consistent with unity for all centrality intervals. The results are compared with theoretical predictions obtained at next-to-leading order using nucleon and nuclear parton distribution functions. The normalised Z boson yields in Pb+Pb collisions lie 1-3a above the predictions. The nuclear modification factor measured as a function of rapidity agrees with unity and is consistent with a next-to-leading-order QCD calculation including the isospin effect.

  • 5.
    Aad, G.
    et al.
    Aix Marseille Univ, IN2P3, CNRS, CPPM, Marseille, France..
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Phys Dept, Stockholm, Sweden..
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Phys Dept, Stockholm, Sweden..
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Phys Dept, Stockholm, Sweden..
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Phys Dept, Stockholm, Sweden..
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector2020In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 101, no 3, article id 032009Article in journal (Refereed)
    Abstract [en]

    A search for the direct production of the supersymmetric partners of tau-leptons (staus) in final states with two hadronically decaying tau-leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of 139 fb(-1), recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected Standard Model background is observed. Limits are derived in scenarios of direct production of stau pairs with each stau decaying into the stable lightest neutralino and one tau-lepton in simplified models where the two stau mass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidence level for a massless lightest neutralino.

  • 6.
    Aad, G.
    et al.
    CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille, France.
    Leopold, Alexander
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lundberg, Olof
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Shaheen, Rabia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland.
    et al.,
    Search for top-philic heavy resonances in pp collisions at s=13 TeV with the ATLAS detector2024In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 84, no 2, article id 157Article in journal (Refereed)
    Abstract [en]

    A search for the associated production of a heavy resonance with a top-quark or a top-antitop-quark pair, and decaying into a tt¯ pair is presented. The search uses the data recorded by the ATLAS detector in pp collisions at s=13 TeV at the Large Hadron Collider during the years 2015–2018, corresponding to an integrated luminosity of 139 fb-1. Events containing exactly one electron or muon are selected. The two hadronically decaying top quarks from the resonance decay are reconstructed using jets clustered with a large radius parameter of R=1. The invariant mass spectrum of the two top quark candidates is used to search for a resonance signal in the range of 1.0 TeV to 3.2 TeV. The presence of a signal is examined using an approach with minimal model dependence followed by a model-dependent interpretation. No significant excess is observed over the background expectation. Upper limits on the production cross section times branching ratio at 95% confidence level are provided for a heavy Z′ boson based on a simplified model, for Z′ mass between 1.0 TeV and 3.0 TeV. The observed (expected) limits range from 21 (14) fb to 119 (86) fb depending on the choice of model parameters.

  • 7.
    Abdollahi, S.
    et al.
    Hiroshima Univ, Dept Phys Sci, Higashihiroshima, Hiroshima 7398526, Japan..
    Axelsson, Magnus
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Stockholm Univ, Dept Phys, AlbaNova, SE-10691 Stockholm, Sweden..
    Jóhannesson, Gudlaugur
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Univ Iceland, Sci Inst, IS-107 Reykjavik, Iceland.;Stockholm Univ, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden..
    Larsson, Stefan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. AlbaNova, Oskar Klein Ctr Cosmoparticle Phys, SE-10691 Stockholm, Sweden.;Dalarna Univ, Sch Educ Hlth & Social Studies, Nat Sci, SE-79188 Falun, Sweden..
    Zaharijas, G.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, I-34127 Trieste, Italy.;Univ Nova Gorica, Ctr Astrophys & Cosmol, Nova Gorica, Slovenia..
    et al.,
    Fermi Large Area Telescope Fourth Source Catalog2020In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 247, no 1, article id 33Article in journal (Refereed)
    Abstract [en]

    We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse gamma-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4 sigma significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.

  • 8.
    Adam, Christoph
    et al.
    Univ Santiago Compostela, Dept Fis Particulas, E-15782 Santiago De Compostela, Spain.;Inst Galego Fis Altas Enerxias IGFAE, E-15782 Santiago De Compostela, Spain..
    Halcrow, Chris
    KTH, School of Engineering Sciences (SCI), Physics.
    Oles, Katarzyna
    Jagiellonian Univ, Inst Theoret Phys, Lojasiewicza 11, Krakow, Poland..
    Romanczukiewicz, Tomasz
    Jagiellonian Univ, Inst Theoret Phys, Lojasiewicza 11, Krakow, Poland..
    Wereszczynski, Andrzej
    Jagiellonian Univ, Inst Theoret Phys, Lojasiewicza 11, Krakow, Poland..
    Moduli Space for Kink Collisions with Moving Center of Mass2023In: Symmetry, Integrability and Geometry: Methods and Applications, E-ISSN 1815-0659, Vol. 19, article id 054Article in journal (Refereed)
    Abstract [en]

    We apply the collective coordinate model framework to describe collisions of a kink and an antikink with nonzero total momentum, i.e., when the solitons possess different velocities. The minimal moduli space with only two coordinates (the mutual distance and the position of the center of mass) is of a wormhole type, whose throat shrinks to a point for symmetric kinks. In this case, a singularity is formed. For non-zero momentum, it prohibits solutions where the solitons pass through each other. We show that this unphysical feature can be cured by enlarging the dimension of the moduli space, e.g., by the inclusion of internal modes.

  • 9.
    af Klinteberg, Ludvig
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    Sorgentone, Chiara
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    Tornberg, Anna-Karin
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    Quadrature error estimates for layer potentials evaluated near curved surfaces in three dimensions2022In: Computers and Mathematics with Applications, ISSN 0898-1221, E-ISSN 1873-7668, Vol. 111, p. 1-19Article in journal (Refereed)
    Abstract [en]

    The quadrature error associated with a regular quadrature rule for evaluation of a layer potential increases rapidly when the evaluation point approaches the surface and the integral becomes nearly singular. Error estimates are needed to determine when the accuracy is insufficient and a more costly special quadrature method should be utilized.& nbsp;The final result of this paper are such quadrature error estimates for the composite Gauss-Legendre rule and the global trapezoidal rule, when applied to evaluate layer potentials defined over smooth curved surfaces in R-3. The estimates have no unknown coefficients and can be efficiently evaluated given the discretization of the surface, invoking a local one-dimensional root-finding procedure. They are derived starting with integrals over curves, using complex analysis involving contour integrals, residue calculus and branch cuts. By complexifying the parameter plane, the theory can be used to derive estimates also for curves in R3. These results are then used in the derivation of the estimates for integrals over surfaces. In this procedure, we also obtain error estimates for layer potentials evaluated over curves in R2. Such estimates combined with a local root-finding procedure for their evaluation were earlier derived for the composite Gauss-Legendre rule for layer potentials written in complex form [4]. This is here extended to provide quadrature error estimates for both complex and real formulations of layer potentials, both for the Gauss-Legendre and the trapezoidal rule.& nbsp;Numerical examples are given to illustrate the performance of the quadrature error estimates. The estimates for integration over curves are in many cases remarkably precise, and the estimates for curved surfaces in R-3 are also sufficiently precise, with sufficiently low computational cost, to be practically useful.

  • 10.
    Aguilar, Xavier
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for High Performance Computing, PDC.
    Markidis, Stefano
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Computational Science and Technology (CST).
    A Deep Learning-Based Particle-in-Cell Method for Plasma Simulations2021In: 2021 IEEE International Conference On Cluster Computing (CLUSTER 2021), Institute of Electrical and Electronics Engineers (IEEE) , 2021, p. 692-697Conference paper (Refereed)
    Abstract [en]

    We design and develop a new Particle-in-Cell (PIC) method for plasma simulations using Deep-Learning (DL) to calculate the electric field from the electron phase space. We train a Multilayer Perceptron (MLP) and a Convolutional Neural Network (CNN) to solve the two-stream instability test. We verify that the DL-based MLP PIC method produces the correct results using the two-stream instability: the DL-based PIC provides the expected growth rate of the two-stream instability. The DL-based PIC does not conserve the total energy and momentum. However, the DL-based PIC method is stable against the cold-beam instability, affecting traditional PIC methods. This work shows that integrating DL technologies into traditional computational methods is a viable approach for developing next-generation PIC algorithms.

  • 11.
    Aho-Mantila, L.
    et al.
    VTT Tech Res Ctr Finland, POB 1000, FI-02044 Espoo, Finland.;VTT Tech Res Ctr Finland, FIN-02044 Espoo, Finland..
    Bergsåker, Henric
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Assessment of SOLPS5.0 divertor solutions with drifts and currents against L-mode experiments in ASDEX Upgrade and JET2017In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 59, no 3, article id 035003Article in journal (Refereed)
    Abstract [en]

    The divertor solutions obtained with the plasma edge modelling tool SOLPS5.0 are discussed. The code results are benchmarked against carefully analysed L-mode discharges at various density levels with and without impurity seeding in the full-metal tokamaks ASDEX Upgrade and JET. The role of the cross-field drifts and currents in the solutions is analysed in detail, and the improvements achieved by fully activating the drift and current terms in view of matching the experimental signals are addressed. The persisting discrepancies are also discussed.

  • 12. Aiba, N
    et al.
    Giroud, C
    Honda, M
    Delabie, E
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Saarelma, S
    Hillesheim, J
    Pamela, S
    Wiesen, S
    Maggi, C
    Urano, H
    Drewelow, P
    Leyland, M
    Moulton, D
    Menmuir, S
    Diamagnetic MHD Equations for Plasmas with Fast Flow and its Application to ELM Analysis in JT-60U and JET-ILW2016In: 26th IAEA Fusion Energy Conference, 17-22 October 2016, 2016Conference paper (Refereed)
  • 13. Aiba, N.
    et al.
    Giroud, C.
    Honda, M.
    Delabie, E.
    Saarelma, S.
    Frassinetti, L
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Lupelli, I.
    Casson, F. J.
    Pamela, S.
    Urano, H.
    Maggi, C. F.
    Numerical analysis of ELM stability with rotation and ion diamagnetic drift effects in JET2017In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 12, article id 126001Article in journal (Refereed)
    Abstract [en]

    Stability to the type-I edge localized mode (ELM) in JET plasmas was investigated numerically by analyzing the stability to a peeling-ballooning mode with the effects of plasma rotation and ion diamagnetic drift. The numerical analysis was performed by solving the extended Frieman-Rotenberg equation with the MINERVA-DI code. To take into account these effects in the stability analysis self-consistently, the procedure of JET equilibrium reconstruction was updated to include the profiles of ion temperature and toroidal rotation, which are determined based on the measurement data in experiments. With the new procedure and MINERVA-DI, it was identified that the stability analysis including the rotation effect can explain the ELM trigger condition in JET with ITER like wall (JET-ILW), though the stability in JET with carbon wall (JET-C) is hardly affected by rotation. The key difference is that the rotation shear in JET-ILW plasmas analyzed in this study is larger than that in JET-C ones, the shear which enhances the dynamic pressure destabilizing a peeling-ballooning mode. In addition, the increase of the toroidal mode number of the unstable MHD mode determining the ELM trigger condition is also important when the plasma density is high in JET-ILW. Though such modes with high toroidal mode number are strongly stabilized by the ion diamagnetic drift effect, it was found that plasma rotation can sometimes overcome this stabilizing effect and destabilizes the peeling-ballooning modes in JET-ILW.

  • 14. Aiba, N
    et al.
    Giroud, C
    Honda, M
    Delabie, E
    Saarelma, S
    Lupelli, I
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Maggi, C
    Impact of rotation and ion diamagnetic drift on ELM stability in JET-ILW2016In: 33rd Annual meeting of Japan society of plasma science and nuclear fusion research JSPF, Nov 2016. Japan, 2016Conference paper (Other academic)
  • 15. Aiba, N.
    et al.
    Pamela, S.
    Honda, M.
    Urano, H.
    Giroud, C.
    Delabie, E.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Lupelli, I.
    Hayashi, N.
    Huijsmans, G.
    Analysis of ELM stability with extended MHD models in JET, JT-60U and future JT-60SA tokamak plasmas2018In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 60, no 1, article id 014032Article in journal (Refereed)
    Abstract [en]

    The stability with respect to a peeling-ballooning mode (PBM) was investigated numerically with extended MHD simulation codes in JET, JT-60U and future JT-60SA plasmas. The MINERVA-DI code was used to analyze the linear stability, including the effects of rotation and ion diamagnetic drift (omega(*i)), in JET-ILW and JT-60SA plasmas, and the JOREK code was used to simulate nonlinear dynamics with rotation, viscosity and resistivity in JT-60U plasmas. It was validated quantitatively that the ELM trigger condition in JET-ILW plasmas can be reasonably explained by taking into account both the rotation and omega(*i) effects in the numerical analysis. When deuterium poloidal rotation is evaluated based on neoclassical theory, an increase in the effective charge of plasma destabilizes the PBM because of an acceleration of rotation and a decrease in omega(*i). The difference in the amount of ELM energy loss in JT-60U plasmas rotating in opposite directions was reproduced qualitatively with JOREK. By comparing the ELM affected areas with linear eigenfunctions, it was confirmed that the difference in the linear stability property, due not to the rotation direction but to the plasma density profile, is thought to be responsible for changing the ELM energy loss just after the ELM crash. A predictive study to determine the pedestal profiles in JT-60SA was performed by updating the EPED1 model to include the rotation and w*i effects in the PBM stability analysis. It was shown that the plasma rotation predicted with the neoclassical toroidal viscosity degrades the pedestal performance by about 10% by destabilizing the PBM, but the pressure pedestal height will be high enough to achieve the target parameters required for the ITER-like shape inductive scenario in JT-60SA.

  • 16. Aijaz, Asim
    et al.
    Sarakinos, Kostas
    Lundin, Daniel
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Helmersson, Ulf
    A strategy for increased carbon ionization in magnetron sputtering discharges2012In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 23, p. 1-4Article in journal (Refereed)
    Abstract [en]

    A strategy that facilitates a substantial increase of carbon ionization in magnetron sputtering discharges is presented in this work. The strategy is based on increasing the electron temperature in a high power impulse magnetron sputtering discharge by using Ne as the sputtering gas. This allows for the generation of an energetic C+ ion population and a substantial increase in the C+ ion flux as compared to a conventional Ar-HiPIMS process. A direct consequence of the ionization enhancement is demonstrated by an increase in the mass density of the grown films up to 2.8 g/cm(3); the density values achieved are substantially higher than those obtained from conventional magnetron sputtering methods.

  • 17. Aikio, A T
    et al.
    Blomberg, Lars
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Yamauchi, M
    On the origin of the high-altitude electric field fluctuations in the auroral zone1996In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 101, no A12, p. 27157-27170Article in journal (Refereed)
    Abstract [en]

    Intense fluctuations in the electric field at high altitudes in the auroral zone are frequently measured by the Viking satellite. We have made an analysis of the origin of electric and magnetic fluctuations in the frequency range of 0.1 - 1 Hz by assuming four different sources for the signals: (I) spatial structures, (2) spatial structures with a parallel potential drop below the satellite, (3) traveling; shear Alfven waves, and (4) interfering shear Alfven waves. We will shaw that these different sources of the signals may produce similar amplitude ratios and phase differences between the perpendicular electric and magnetic fields. Since the different sources have different frequency dependencies, this can be used as an additional test if the signals are broadband. In other cases, additional information is needed, for example, satellite particle measurements or ground; magnetic measurements. The ideas presented in the theory were tested for one Viking eveningside pass over Scandinavia, where ground-based magnetometer and EISCAT radar measurements were available. The magnetic conditions were active during this pass and several interfering shear Alfven waves were found. Also, a spatial structure with a parallel potential drop below the satellite was identified. The magnitude of the 10-km-wide potential drop was at least 2 kV and the upward field-aligned current 26 mu A m(-2) (value mapped to the ionospheric level). The held-aligned conductance was estimated as 1.3 - 2.2x10(-8) S m(-2).

  • 18. Airila, M. I.
    et al.
    Aho-Mantila, L.
    Brezinsek, S.
    Coad, J. P.
    Kirschner, A.
    Likonen, J.
    Matveev, D.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Strachan, J. D.
    Widdowson, A.
    Wiesen, S.
    ERO modelling of local deposition of injected C-13 tracer at the outer divertor of JET2009In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T138, p. 014021-Article in journal (Refereed)
    Abstract [en]

    The 2004 tracer experiment of JET with the injection of (CH4)-C-13 into H-mode plasma at the outer divertor has been modelled with the Monte Carlo impurity transport code ERO. EDGE2D solutions for inter-ELM and ELM-peak phases were used as plasma backgrounds. Local two-dimensional (2D) deposition patterns at the vertical outer divertor target plate were obtained for comparison with post-mortem surface analyses. ERO also provides emission profiles for comparison with radially resolved spectroscopic measurements. Modelling indicates that enhanced re-erosion of deposited carbon layers is essential in explaining the amount of local deposition. Assuming negligible effective sticking of hydrocarbons, the measured local deposition of 20-34% is reproduced if re-erosion of deposits is enhanced by a factor of 2.5-7 compared to graphite erosion. If deposits are treated like the substrate, the modelled deposition is 55%. Deposition measurements at the shadowed area around injectors can be well explained by assuming negligible re-erosion but similar sticking behaviour there as on plasma-wetted surfaces.

  • 19. Airila, M. I.
    et al.
    Jarvinen, A.
    Groth, M.
    Belo, P.
    Wiesen, S.
    Brezinsek, S.
    Lawson, K.
    Borodin, D.
    Kirschner, A.
    Coad, J. P.
    Heinola, K.
    Likonen, J.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Widdowson, A.
    Preliminary Monte Carlo simulation of beryllium migration during JET ITER-like wall divertor operation2015In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, p. 800-804Article in journal (Refereed)
    Abstract [en]

    Migration of beryllium into the divertor and deposition on tungsten in the final phase of the first ITER-like-wall campaign of JET are modelled with the 3D Monte Carlo impurity transport code ERO. The simulation covers the inner wall and the inner divertor. To generate the plasma background for Monte Carlo tracing of impurity particles, we use the EDGE2D/EIRENE code set. At the relevant regions of the wall, the estimated plasma conditions vary around T-e approximate to 5eV and n(e) 2 x 10(17) m(-3) (far-scrape-off layer; more than 10 cm away from the LCFS). We calculate impurity distributions in the plasma using the main chamber source as a free parameter in modelling and attempt to reproduce inter-ELM spectroscopic BeII line (527 nm) profiles at the divertor. The present model reproduces the level of emission close to the inner wall, but further work is needed to match also the measured emission peak values and ultimately link the modelled poloidal net deposition profiles of beryllium to post mortem data.

  • 20.
    Alaniz, Monica
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Belyayev, Serhiy
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Bergman, David
    Casselbrant, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Honeth, Mark
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Huang, Jiangwei
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Ivchenko, Nickolay
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Laukkanen, Mikko
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Michelsen, Jacob
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Pronenko, Vira
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Paulson, Malin
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Schlick, Georg
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Valle, Mario
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    The SQUID sounding rocket experiment2011In: Proceedings of the 20th ESA Symposium on European Rocket and Balloon Programmes and Related Research, European Space Agency, 2011, p. 159-166Conference paper (Refereed)
    Abstract [en]

    The objective of the SQUID project is to develop and in flight verify a miniature version of a wire boom deployment mechanism to be used for electric field measurements in the ionosphere. In February 2011 a small ejectable payload, built by a team of students from The Royal Institute of Technology (KTH), was launched from Esrange on-board the REXUS-10 sounding rocket. The payload separated from the rocket, deployed and retracted the wire booms, landed with a parachute and was subsequently recovered. Here the design of the experiment and post fight analysis are presented.

  • 21. Albornoz, N. L. Gonzalez
    et al.
    Schmidt-May, Angnis
    von Strauss, Mikael
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Dark matter scenarios with multiple spin-2 fields2018In: Journal of Cosmology and Astroparticle Physics, E-ISSN 1475-7516, no 1, article id 014Article in journal (Refereed)
    Abstract [en]

    We study ghost-free multimetric theories for (N + 1) tensor fields with a coupling to matter and maximal global symmetry group S-N x (Z(2))(N). Their mass spectra contain a massless mode, the graviton, and N massive spin-2 modes. One of the massive modes is distinct by being the heaviest, the remaining (N - 1) massive modes are simply identical copies of each other. All relevant physics can therefore be understood from the case N = 2. Focussing on this case, we compute the full perturbative action up to cubic order and derive several features that hold to all orders in perturbation theory. The lighter massive mode does not couple to matter and neither of the massive modes decay into massless gravitons. We propose the lighter massive particle as a candidate for dark matter and investigate its phenomenology in the parameter region where the matter coupling is dominated by the massless graviton. The relic density of massive spin-2 can originate from a freeze-in mechanism or from gravitational particle production, giving rise to two different dark matter scenarios. The allowed parameter regions are very different from those in scenarios with only one massive spin-2 field and more accessible to experiments.

  • 22. Alfier, A.
    et al.
    Pasqualotto, R.
    Spizzo, G.
    Canton, A.
    Fassina, A.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Electron temperature profiles in RFX-mod2008In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 50, no 3, p. 035013-Article in journal (Refereed)
    Abstract [en]

    Electron temperature profiles have been measured by the main Thomson scattering ( TS) diagnostic on the RFX-mod reversed field pinch experiment in Padova, Italy. The increased accuracy and spatial and temporal resolution permits one to measure in detail the improvements in T-e profiles, obtained with the active saddle coil system, which allows one to obtain core temperature 30% higher and scaling stronger with plasma current, steeper gradients in the core (+30%) and at the edge (+60%). 1D power balance calculations show that the active control of MHD modes largely reduces the values of electron heat diffusivity along the whole plasma radius, with similar to 50% reduction at the edge and similar to 30% in the core. The resulting electron energy confinement time is doubled. Further improvements occur during quasi-single helicity (QSH) states: the new TS allows one to study in detail the hot island that develops in the core. A characterization of the island electron thermal profile is presented, in terms of width, temperature increase, gradients and asymmetry; the effect on density profile is also discussed. A 2D transport code has been applied to calculate the heat diffusivity inside the magnetic island corresponding to the QSH state, also considering the correlation between temperature increase and pressure gradient with the chaos level around the island. Finally, electron energy confinement time during QSH states is compared with that in MH states.

  • 23.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Annihilation Model of the QSOs1979Report (Other academic)
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  • 24.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Comment on H. Arp "The Persistent Problem of Spiral Galaxies"1987Report (Other academic)
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  • 25.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Cosmogony as an Extrapolation of Magnetospheric Research1984Report (Other academic)
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  • 26.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Cosmology in the Plasma Universe1987Report (Other academic)
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  • 27.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Cosmology in the plasma universe - an introductory exposition1990In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 18, no 1, p. 5-10Article in journal (Refereed)
    Abstract [en]

    Acceptance of the plasma universe model is now leading to drastically new views of the structure of the universe. The basic aspects of cosmological importance are: (a) the same basic laws of plasma physics hold everywhere; (b) mapping of electric fields and currents is necessary to understand cosmic plasma; (c) space is filled with a network of currents leading to the cellular and filamentary structure of matter; and (d) double layers, critical velocity, and pinch effects are of decisive importance in how cosmic evolves. A review is presented of a number of the outstanding questions of cosmology in the plasma universe.

  • 28.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Cosmology: Myth or science1976In: La Recherche (Imprimé), ISSN 0029-5671, E-ISSN 1625-9955, Vol. 7, no 69, p. 610-616Article in journal (Refereed)
  • 29.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Double Layers and Circuits in Astrophysics1986Report (Other academic)
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  • 30.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Double radio sources and the new approach to cosmic plasma physics1977Report (Other academic)
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  • 31.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Double Radio Sources and the New Approach to Cosmic Plasma Physics1977Report (Other academic)
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  • 32.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Double-layers and circuits in astrophysics1986In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 14, no 6, p. 779-793Article in journal (Refereed)
    Abstract [en]

    As the rate of energy release in a double layer with voltage ΔV is P ≈ IΔV, a double layer must be treated as a part of a circuit which delivers the current I. As neither double layer nor circuit can be derived from magnetofluid models of a plasma, such models are useless for treating energy transfer by means of double layers. They must be replaced by particle models and circuit theory. A simple circuit is suggested which is applied to the energizing of auroral particles, to solar flares, and to intergalactic double radio sources. Application to the heliospheric current systems leads to the prediction of two double layers on the sun's axis which may give radiations detectable from Earth. Double layers in space should be classified as a new type of celestial object (one example is the double radio sources). It is tentatively suggested that X-ray and γ-ray bursts may be due to exploding double layers (although annihilation is an alternative energy source). A study of how a number of the most used textbooks in astrophysics treat important concepts such as double layers, critical velocity, pinch effects, and circuits is made. It is found that students using these textbooks remain essentially ignorant of even the existence of these concepts, despite the fact that some of them have been well known for half a century (e.g., double layers, Langmuir, 1929; pinch effect, Bennet, 1934).

  • 33.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Electric Current Model of Magnetosphere1979Report (Other academic)
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  • 34.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Electric currents in cosmic plasmas1977Report (Other academic)
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  • 35.
    Alfvén, Hannes
    University of California San Diego, Dept Applied Physics and Information Science, San Diego, CA 92093.
    Electric currents in cosmic plasmas1977In: Transactions - American Geophysical Union, ISSN 0002-8606, Vol. 58, no 6, p. 551-551Article in journal (Other academic)
  • 36.
    Alfvén, Hannes
    University of California San Diego, Dept Applied Physics and Information Science, San Diego, CA 92093.
    Electric currents in cosmic plasmas1977In: Reviews of geophysics, ISSN 8755-1209, E-ISSN 1944-9208, Vol. 15, no 3, p. 271-284Article in journal (Refereed)
    Abstract [en]

    Since the beginning of the century, physics has been dualistic in the sense that some phenomena are described by a field concept and others by a particle concept. This dualism is essential also in the physics of cosmic plasmas: some phenomena should be described by a magnetic field formalism, and others by an electric current formalism. During the first period of evolution of cosmic plasma physics the magnetic field aspect has dominated, and a fairly exhaustive description has been given of those phenomena, like the propagation of waves, which can be described in this way. We have now entered a second period, which is dominated by a systematic exploration of the particle (or current) aspect. A survey is given of a number of phenomena which can be understood only from the particle aspect. These include the formation of electric double layers, the origin of ‘explosive’ events like magnetic substorms and solar flares, and further, the transfer of energy from one region to another. A useful method of exploring many of these phenomena is to draw the electric circuit in which the current flows and to study its properties. A number of simple circuits are analyzed in this way.

  • 37.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Electric-current model of the magnetosphere1979In: ESA Journal, ISSN 0379-2285, Vol. 3, no 2, p. 91-99Article in journal (Refereed)
    Abstract [en]

    A translation of the traditional field description of the magnetosphere into a particle (electric current) description is offered. Focus is on the energy transfer from the solar wind. The solar wind flow through the magnetic field acts as an electric generator. Its power is transferred to the magnetosphere through four main circuits. These are the magnetopause circuit, the solar wind/auroral circuit, the tail circuit, and the front circuit. A fifth circuit, the substorm circuit, is also very often energized. When the tail circuit flares, the current is partly redirected over the auroral zone, flowing in what is called the 'substorm circuit'. 

  • 38.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Magnetospheric Research and the History of the Solar System1984Report (Other academic)
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  • 39.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Model of the plasma universe1986In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 14, no 6, p. 629-638Article in journal (Refereed)
    Abstract [en]

    This paper is a review of a number of publications during the last ten years about those changes in our views of the cosmic environment that are the result of advances in plasma physics. To a large extent, these originate from new observational material that space research has supplied. An attempt is made to construct a model of the "plasma universe" which is claimed to be an alternative to the traditional " visual universe" based mainly on observations in the visual octave. Besides the Hubble expansion there is also a "knowledge expansion," which means that knowledge originating from plasma experiments in the laboratory is spreading to the magnetospheres and, it is predicted, sooner or later will also penetrate astrophysics in general. As an example of the usefulness of this model, it is applied to cosmogony, and a review is given of new results from an analysis of the Saturnian rings. The recent reconstruction of certain cosmogonic events with an accuracy better than 1 percent is reviewed and developed.

  • 40.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Observations and hypotheses in cosmology1978Report (Other academic)
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  • 41.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    On the solar corona1941In: Arkiv för matematik, astronomi och fysik, ISSN 0365-4133, Vol. 27 A, no 25, p. 1-23Article in journal (Refereed)
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  • 42.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Origin of the solar system1976Report (Other academic)
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  • 43.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Paradigm Transition in Cosmic Plasma Physics1982Report (Other academic)
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  • 44.
    Alfvén, Hannes
    Dept Applied Physics and Information Science, University of California, San Diego, La Jolla, CA 92093, USA.
    Paradigm transition in cosmic plasma physics1983In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 10, no 6, p. 487-488Article in journal (Refereed)
    Abstract [en]

    During the 1970's in situ measurements in the magnetospheres, including the solar wind region ("solar magnetosphere") drastically changed our understanding of the properties of cosmic plasmas. Further, we have learned how to generalize results from plasma investigations in one region to other regions. This means that laboratory investigations of plasmas of the size of, say, 10 cm can be used to achieve better understanding of cosmic plasmas of magnetospheric dimensions; say, 1010 cm. By another step of 109 we can transfer laboratory and magnetospheric results to galactic plasmas of, say, 1019 cm. A third jump of 109 brings us up to the Hubble distance 1028 cm and hence to cosmological problems (see Figure 1).

  • 45.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Paradigm transition in cosmic plasma physics1982In: Physica scripta. T, ISSN 0281-1847, Vol. T2, p. 10-19Article in journal (Refereed)
    Abstract [en]

    In situ measurements in the magnetospheres together with general advancement in plasma physics are now necessitating introduction of a number of effects that have been recently discovered or earlier neglected. Examples are:

    Electric double layers (like in the lower magnetosphere);

    Thin current layer (like in the magnetopause) giving space a cellular structure;

    Current produced filaments (e.g., in prominences, solar corona and interstellar clouds).

    Further it is important to use the electric current (particle) description and to study the whole circuit in which the current flows.

    The pinch effect cannot be neglected as is now usually done.

    The critical velocity phenomenon is essential, for example for the band structure of solar system.

    Theory of dusty plasmas is important. 

    The result is a change in so many theories in cosmic plasma physics that it is appropriate to speak of an introduction of a new paradigm. This should be based on empirical knowledge from magnetospheric and laboratory investigations. Its application to astrophysics in general, including cosmology, will necessarily lead to a revision of, e.g., the present theories of the formation of stars, planets and satellites. It is doubtful whether the big bang cosmology will survive.

  • 46.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Plasma Universe1986Report (Other academic)
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  • 47.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Plasma universe1987In: Physica scripta. T, ISSN 0281-1847, Vol. T18, p. 20-28Article in journal (Refereed)
    Abstract [en]

    Traditionally the views on our cosmic environment have been based on observations in the visual octave of the electromagnetic spectrum, during the last half-century supplemented by infrared and radio observations.

    Space research has opened the full spectrum. Of special importance are the x-ray-γ-ray regions, in which a number of unexpected phenomena have been discovered. Radiations in these regions are likely to originate mainly from magnetised cosmic plasmas. Such a medium may also emit synchrotron radiation which is observable in the radio region.

    If we try to base a model of the universe on the plasma phenomena mentioned we find that the plasma universe is drastically different from the traditional visual universe.

    Information about the plasma universe can also be obtained by extrapolation of laboratory experiments and magnetospheric in situ measurements of plasmas. This approach is possible because it is likely that the basic properties of plasmas are the same everywhere.

    In order to test the usefulness of the plasma universe model we apply it to cosmogony. Such an approach seems to be rather successful. For example, the complicated structure of the Saturnian C ring can be accounted for. It is possible to reconstruct certain phenomena 4-5 billions years ago with an accuracy of better than 1%.

  • 48.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Rymdforskningen och vår världsbild1982Report (Other academic)
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  • 49.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Saturnian rings1976In: Astrophysics and Space Science, ISSN 0004-640X, E-ISSN 1572-946X, Vol. 43, no 1, p. 97-104Article in journal (Refereed)
    Abstract [en]

    The structure of the Saturnian rings is compared with the asteroidal belt and the relative importance of the resonance effects and the cosmogonic effects is evaluated. No visible correspondence to the Kirkwood gaps is expected theoretically, nor is there any observational evidence for such effects. The only possible resonance is the 1:1 resonance with Saturn's spin period.

    Cosmogonic ‘shadow’ effects are responsible for the main features of the ring structure, including Cassini's division, the limit between the B and C ring, and possibly also Guérin's division.

  • 50.
    Alfvén, Hannes
    KTH, Superseded Departments (pre-2005).
    Science and the future of Europe1978Report (Other academic)
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