Laplace equation
Linear partial homogeneous differential equation of second order and elliptical type. Used for the estimation of scalar potential fields (i.e. free of sources), such as the geomagnetic field at the Earths surface (or between surface and ionosphere). The Laplace equation can be solved in spherical coordinates by the expansion of the potential into spherical harmonics.



La Tène
A continental European Iron-age culture beginning around 450 BC and ending with the Roman conquest. Named after a Swiss lake site.