  We consider a system of non-interacting charged particles moving in two
dimensions among fixed hard scatterers, and acted upon by a perpendicular
magnetic field. Recollisions between charged particles and scatterers are
unavoidable in this case. We derive from the Liouville equation for this system
a generalized Boltzmann equation with infinitely long memory, but which still
is analytically solvable. This kinetic equation has been earlier written down
from intuitive arguments.
