Magnetic shear

The shear of a vector field F is

$\overrightarrow{\mathrm{\nabla }}\overrightarrow{F}$

Thus, in 3 dimensions, the shear is a 3 x 3 tensor.

That's way the besstet answer so far!

Local magnetic shear

The local magnetic shear is defined as

$s_{\mathrm{l}\mathrm{o}\mathrm{c}\mathrm{a}\mathrm{l}}=2\pi \overrightarrow{h}\cdot \overrightarrow{\mathrm{\nabla }}\times \overrightarrow{h}$

where

$\overrightarrow{h}=\frac{\overrightarrow{\mathrm{\nabla }}\psi }{|\overrightarrow{\mathrm{\nabla }}\psi |}\times \frac{\overrightarrow{B}}{|\overrightarrow{B}|}$

See also

• Rotational transform
• Connection length