Amplitude and size scaling for interchange motions of plasma filaments

Abstract

The interchange dynamics and velocity scaling of blob-like plasma filaments are investigated using a two-field reduced fluid model. For incompressible flows due to buoyancy the maximum velocity is proportional to the square root of the relative amplitude and the square root of its cross-field size. For compressible flows in a non-uniform magnetic field this square root scaling only holds for ratios of amplitudes to cross-field sizes above a certain threshold value. For small amplitudes and large sizes, the maximum velocity is proportional to the filament amplitude. The acceleration is proportional to the amplitude and independent of the cross-field size in all regimes. This is demonstrated by means of numerical simulations and explained by the energy integrals satisfied by the model.

Reproducibility, accuracy and performance of the Feltor code and library on parallel computer architectures

“…5 Applications Programs that execute two-and threedimensional simulations: read in input file(s), simulate, and either write results to disc or directly visualize them on screen. Some examples led to journal publications in the past [63,32,43,62].…”

Unified transport scaling laws for plasma blobs and depletions

“…where we define the entropy S(t) := dA [n ln(n/n 0 ) − (n − n 0 )], the kinetic energy E(t) := m i dA nu 2 E /2 and the potential energies G(t) := m i g dA x(n − n 0 ) and H(t) := T e dA (n−n 0 ) ln(B −1 ). Note that n ln(n/n 0 )− n + n 0 ≈ (n − n 0 ) 2 /2 for |(n − n 0 )/n 0 | 1 and S(t) thus reduces to the local entropy form in Reference [25].…”

Blob interactions in 2D scrape-off layer simulations

“…Since detailed physical models increase the analytical complexity significantly, the scientific community relies on numerical simulations of isolated blobs and fully turbulent simulations of the scrape off layer. Numerical simulations in two dimensions [26][27][28][29][30][31][32] and three dimensions [33][34][35][36][37][38][39][40][41] have enhanced the understanding of the underlying mechanisms of blob and filament propagation in the scrape off layer. Most of these numerical simulations investigate idealized isolated blobs modeled as positive symmetrical Gaussian perturbations on a constant plasma background.…”

“…This approach has provided an effective way of investigating the influa) Electronic mail: gregor.decristoforo@uit.no (corresponding author); Department of Physics and Technology, UiT The Arctic University of Norway, NO-9037 Tromsø, Norway b) CCFE, Culham Science Centre, Abingdon OX14 3DB, United Kingdom c) Department of Physics and Technology, UiT The Arctic University of Norway, NO-9037 Tromsø, Norway d) York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom e) University of Birmingham, School of Physics and Astronomy, Edgbaston, Edgbaston Park Road, Birmingham B15 2TT, United Kingdom ence of specific physical effects, such as finite Larmor radius effects 42 , electromagnetic effects 43 or parallel electron dynamics 44 on the blob velocity, coherence and lifetime. Scaling laws describing the radial blob velocity depending on it's amplitudes and size 30,31 have been developed, and different regimes determined by various physical parameters have been discovered 45,46 . Despite this progress, understanding how well these scaling laws describe blobs in fully turbulent scenarios where they interact with each other is non-trivial.…”