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Magnetic island: Difference between revisions
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In the context of magnetic confinement fusion, the basic magnetic field configuration consists of toroidally nested [[Flux surface|flux surfaces]], while each flux surface is characterised by a certain value of the [[Magnetic shear|magnetic shear]]. Magnetic islands can appear at flux surfaces with a rational value of the safety factor ''q = m/n''. | In the context of magnetic confinement fusion, the basic magnetic field configuration consists of toroidally nested [[Flux surface|flux surfaces]], while each flux surface is characterised by a certain value of the [[Magnetic shear|magnetic shear]]. Magnetic islands can appear at flux surfaces with a rational value of the safety factor ''q = m/n''. | ||
<ref>[http://dx.doi.org/10.1051/anphys:2004001 J.H. Misguich, J.-D. Reuss, D. Constantinescu, G. Steinbrecher, M. Vlad, F. Spineanu, B. Weyssow, R. Balescu, ''Noble internal transport barriers and radial subdiffusion of toroidal magnetic lines'', Ann. Phys. Fr. ''28'' (2003) 1]</ref> | <ref>[http://dx.doi.org/10.1051/anphys:2004001 J.H. Misguich, J.-D. Reuss, D. Constantinescu, G. Steinbrecher, M. Vlad, F. Spineanu, B. Weyssow, R. Balescu, ''Noble internal transport barriers and radial subdiffusion of toroidal magnetic lines'', Ann. Phys. Fr. ''28'' (2003) 1]</ref> | ||
== Birth == | |||
The rupture of the original topology of toroidally nested flux surfaces needed to produce the island requires the reconnection of magnetic field lines, which can only occur with finite resistivity. | The rupture of the original topology of toroidally nested flux surfaces needed to produce the island requires the reconnection of magnetic field lines, which can only occur with finite resistivity. | ||
== Transport effects == | |||
It is generally assumed that the temperature is rapidly equilibrated along the magnetic field lines inside the island, so that radial transport is effectively short-circuited across the islands, decreasing the effective size of the main plasma. | |||
<ref>[http://dx.doi.org/10.1088/0029-5515/39/12/302 ITER Physics Expert Group on Confinement and Transport et al, ''Chapter 2: Plasma confinement and transport'', Nucl. Fusion '''39''' (1999) 2175-2249 ]</ref> | |||
However, is is possible to qualify this statement somewhat by taking into account the ratio between parallel and parpendicular transport within an island. | |||
<ref>[http://dx.doi.org/10.1088/0029-5515/33/8/I03 B.Ph. van Milligen, A.C.A.P. van Lammeren, N.J. Lopes Cardozo, F.C. Schüller, and M. Verreck, ''Gradients of electron temperature and density across m=2 islands in RTP'', Nucl. Fusion '''33''' (1993) 1119]</ref> | |||
== References == | == References == | ||
<references /> | <references /> | ||