A model is introduced to describe negative first return strokes in lig
htning ground hashes. The basic assumptions made are similar to those
used previously to describe the subsequent return strokes. The model p
redictions are in general agreement with experimental observation. The
model predicts the relationships between (a) peak current and the pea
k electric radiation held and (b) the peak derivatives of current and
electric radiation held. These relationships can be used in the remote
sensing of first return stroke current parameters through the measure
d radiation fields.