This function names a pla
This function names a plasma instability which has a "slab" type caused by the coupling between ion acoustic waves and drift waves. This function also names a component of the drift velocity for a charged particle in an inhomogenous magnetic field. The fluid velocity dotted with this function of the fluid velocity gives the convective acceleration. Performing a gauge transformation of the vector potential is done by adding this function of the gauge function to the vector potential. Under certain conditions, a function F can be expressed as the sum of this function applied to some scalar, V, plus this function crossed with some vector, A, according to Helmholtz's theorem. Applying this operation to the velocity potential gives the fluid velocity, and minus this operation applied to the electric potential gives the electric field. For 10 points, name this operation from vector calculus which generalizes the derivative to multiple dimensions, and is symbolized del.