Chemistry - Magnetic helicity

this page is about helicity in magnetic fields. For fluid mechanical helicity, see helicity

In electromagnetism, magnetic helicity is the extent to which a magnetic field "wraps around itself". If magnetic field lines follow the strands of a twisted rope, this configuration would have nonzero magnetic helicity; left handed ropes would have negative values and right handed ropes would have positive values.

Formally,

$H=\int {\mathbf A}\cdot{\mathbf B}\,d^3{\mathbf r}$

where

${\mathbf B}$ is the magnetic field strength

${\mathbf B}=\nabla\times{\mathbf A}$ Where $\mathbf A$ is the vector potential of ${\mathbf B}$

Magnetic helicity is a conserved quantity. It is conserved in electromagnetic fields, even when magnetic reconnection dissipates energy. The concept is useful when considering solar dynamics.

Categories: Physical quantity | Magnetism