Magnetic field-line curvature
= Magnetic field-line curvature
{title2=$\boldsymbol\kappa=\mathbf b\cdot\nabla\mathbf b$}
The curvature <vector> of a <magnetic field line> parametrized by arc length. For circular lines, it points towards their center and has magnitude $1/R$. The curvature contribution to <magnetic tension> is $B^2\boldsymbol\kappa/(4\pi)$ in <Gaussian units>.