Rotating twisted filaments buoyancy: Comparison between the convective region of the sun and the edge of a tokamak plasma

F. Alladio, A. Mancuso, P. Micozzi

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Abstract

The filament state of a magnetic field is the usual way for plasmas to avoid magnetic inhibition of convective overturning. However, it requires dynamo conversion of kinetic into magnetic energy and is therefore often associated with a plasma velocity shear layer. In the sun, isolated current carrying magnetic filaments (twisted flux tubes) are produced by the solar dynamo from a continuous strong toroidal field, sitting just below the radiative-convective transition, on the Sun rotation shear layer (tachocline, rTach ∼ 2 R⊙/3 in terms of the solar radius, R⊙). The twisted flux tubes, become buoyant; some of them fall back into the tachocline adding up to the continuous toroidal field; some emerge from the photosphere kinked and twisted, reconnect and produce flares. In the mode of high magnetic confinement (H-mode), when a magnetic separatrix bounds the axisymmetric tokamak discharge and a sheared plasma rotation is present, magnetic filaments with concentrated internal currents (edge localized modes) are produced near the velocity shear layer (pressure pedestal, at rPed ≥ 0.94a Sep in terms of the minor radius of the plasma boundary, a Sep): again a dynamo conversion of kinetic into magnetic energy is required in order to filament the current density at the pedestal. The current carrying filaments break the unperturbed axisymmetric tokamak equilibrium, producing ergodicity in the edge plasma. The faster loss of energy from the ergodic plasma makes the rotating magnetic filaments outboards anti-buoyant: therefore they convect outboards from the pedestal. The anti-buoyancy and motion model for the tokamak case is compared with the buoyancy model for the Sun. © 2008 IOP Publishing Ltd.
Original languageEnglish
Article number124019
Pages (from-to)-
JournalPlasma Physics and Controlled Fusion
Volume50
Issue number12
DOIs
Publication statusPublished - 2008
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Nuclear Energy and Engineering

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