First integrals for a charged particle moving on a plane under the action of a magnetic field orthogonal to this plane

We characterize the polynomial (respectively analytical) first integrals of degree one in the variables u and v of the differential systems of the form x′=u, y′=v, u′=B(x,y)v and v′=-B(x,y)u where B=B(x,y) is a polynomial (respectively analytic function) in the variables x and y. This differential system models a non-relativistic charge moving on a plane under the action of a magnetic field orthogonal to this plane. © 2012 Elsevier Ltd. All rights reserved.