Coronae also influence the time behaviour of the electric field at the ground.
The field at the ground often changes very rapidly after a lightning flash. The rate of change decreases as the field approaches the value it had prior to the flash. This behaviour is similar to that of the field farther aloft in the interior of the cloud. Our numerical simulations of the shapes of recovery curves indicate that the corona current density is more accurately described by a cubic function than by a quadratic function of the electric field strength at the ground. Despite strong influences of coronae, three properties of the field at the ground accurately reflect what happens above the space charge layer.