Mesospheric electric field transients due to tropospheric lightning discharges

A physical picture and quantitative two-dimensional electromagnetic modelin g of mesospheric electric field transients produced by cloud-to-ground (CG) lightning discharges with short duration currents (<0.5 ms) are presented. The range of applicability of existing quasi-electrostatic models of sprit es and the physical conditions under which relatively weak CG lightning dis charges (thundercloud charge moment changes less than 50Cx10 km) may initia te sprites are discussed in the context of recent experimental findings.