The curl of a vector field produces another vector field. Pictorially, the direction of rotation of the field produced by operation of the curl in an infinitesimal neighborhood of a point in 3D space defines the direction of at the point . A curl of positive magnitude spins in a counterclockwise direction around , in accordance with the "right-hand rule". The angular speed of the rotation equals 1/2 the magnitude of the curl at the point .