• Anomalous transport due to large coherent structures in a magnetized toroidal plasma 

      Fredriksen, Åshild; Pécseli, Hans L; Trulsen, Jan Karsten (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-18)
      Anomalous transport due to large coherent structures, or coherent events, is studied experimentally in a magnetized toroidal discharge plasma. The present analysis emphasizes anomalous plasma losses as well as transport of electron thermal energy density across magnetic field lines. The experiment was carried out in the Blaamann device at the University of Tromsø. The diagnostics are based on data ...
    • The Impact of Turbulence on the Ionosphere and Magnetosphere 

      Guio, Patrick; Pécseli, Hans L (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-25)
      An important property associated with turbulence in plasmas and fluids is anomalous transport. Plasma, being a good conductor, can in addition be affected by turbulence causing an anomalous resistivity that can significantly exceed its classical counterpart. While turbulent transport may be adequately described in configuration space, some aspects of the anomalous resistivity are best accounted for ...
    • On the applicability of Taylor's hypothesis, including small sampling velocities 

      Pécseli, Hans L; Trulsen, Jan Karsten (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-03)
      Taylor's hypothesis, or the frozen turbulence approximation, can be used to estimate also the specific energy dissipation rate ϵ by comparing experimental results with the Kolmogorov–Obukhov expression. The hypothesis assumes that a frequency detected by an instrument moving with a constant large velocity <i><b>V</i></b> can be related to a wavenumber by <i><b>ω=kV</i></b>. It is, however, not obvious ...
    • Weakly nonlinear ion sound waves in gravitational systems 

      Guio, Patrick; Pécseli, Hans L (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-27)
      Ion sound waves are studied in a plasma subject to gravitational field giving rise to vertically inhomogeneous steady-state plasma conditions. Such systems are interesting by exhibiting a wave growth that is a result of energy flux conservation for pulses propagating in an inhomogeneous system. The increase of the amplitude of a pulse as it propagates along the density gradient in the direction of ...