Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996a%26a...308..935b&link_type=abstract
Astronomy and Astrophysics, v.308, p.935-950
Astronomy and Astrophysics
Astrophysics
38
Sun: Corona, Mhd, Methods: Numerical, Instabilities
Scientific paper
A fully three dimensional non-linear magnetohydrodynamic (MHD) simulation of the evolution of ideal kink modes in line-tied cylindrical coronal loops is presented. Two distinct initially unstable equilibria are considered: the uniform- twist force-free Gold-Hoyle profile, and a more realistic non force free field with variable and localized twist profile. In this latter case the instability non-linearly develops at the axial midplane of the loop a current concentration radially localized at a resonant point r_s_, where the condition {vec}(k).{vec}(B)=0 is satisfied, {vec}(k) being the local wave vector of the mode and {vec}(B) the equilibrium magnetic field. No such fine scale current structure forms for the Gold-Hoyle profile since {vec}(k).{vec}(B) then never vanishes. This current concentration extends along all the loop length down to the photosphere, and it takes the form of an helical ribbon of intense current with a weakly variable helicity along the axial direction. A kinked bifurcated equilibrium is reached in which the current concentration generated is non singular in the sense that this has a non-zero thickness. Moreover, the non-linear perturbed current seems to develop a filamentary structure superposed on the current layer. We discuss the resistive dissipation mechanism of such fine-scale structures.
Baty Hubert
Heyvaerts Jean
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