  We investigate the effect of halo activity on the electrostatic field
measured at ground level. We use electrostatic arguments as well as
self-consistent simulations to show that, due to the screening charge in the
ionosphere, the distant electrostatic field created by the uncompensated charge
in a thundercloud decays exponentially rather than as the third power of the
distance. Furthermore, significative ionization around the lower edge of the
ionosphere slightly reduces the electrostatic field at ground level. We
conclude that halos do not extend the range of detectability of
lightning-induced electrostatic fields.
