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Magnetic shear: Difference between revisions
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High values of magnetic shear provide stability, since the radial extension of helically resonant modes is reduced. | High values of magnetic shear provide stability, since the radial extension of helically resonant modes is reduced. | ||
Negative shear also provides stability, possibly because convective cells, generated by curvature-driven instabilities, are sheared apart as the field lines twist around the torus. | Negative shear also provides stability, possibly because convective cells, generated by curvature-driven instabilities, are sheared apart as the field lines twist around the torus. | ||
<ref> | <ref>T.M. Antonsen, Jr., et al, ''Physical mechanism of enhanced stability from negative shear in tokamaks: Implications for edge transport and the L-H transition'', [[doi:10.1063/1.871928|Phys. Plasmas '''3''', 2221 (1996)]]</ref> | ||
== Local magnetic shear == | == Local magnetic shear == | ||
The local magnetic shear is defined as | The local magnetic shear is defined as | ||
<ref> | <ref>M. Nadeem et al, ''Local magnetic shear and drift waves in stellarators'', [[doi:10.1063/1.1396842|Phys. Plasmas '''8''' (2001) 4375]]</ref> | ||
:<math>s_{\rm local} = 2 \pi \vec{h} \cdot \vec{\nabla} \times \vec{h}</math> | :<math>s_{\rm local} = 2 \pi \vec{h} \cdot \vec{\nabla} \times \vec{h}</math> | ||