The quasi-electrostatic heating model (Pasko et al.(1997)) postulates electric fields which are a result of the sudden reconfiguration of thunderstorm charge due to the removal of charge by a lightning discharge. A large positive cloud to ground flash removes positive charge from the upper charge center (e.g. 300 C removed from 10 km altitude) which produces a large change in the electric field (greater than 100 V/m at 70 km altitude). The field persists for approximately the local relaxation time (milliseconds at 85 km altitude, but seconds at 45 km altitude). The strength of the field is determined by charge moment (Q x L) of the lightning flash. In order to test the model, experimental determination of charge moment from ELF/VLF (10 Hz - 30 kHz) measurements has been developed (Cummer et al.(1998)). Similar to the quasi-electrostatic model is the EMP induced breakdown model which includes the addition of an upward propagating EMP associated with a large lightning stroke that can produce breakdown at altitudes above 60 km (Taranenko et al.(1993b),Fernsler and Rowland(1996),Inan et al.(1996a),Taranenko et al.(1993a),Milikh et al.(1995),Rowland et al.(1995),Rowland et al.(1996)).
The runaway electron model postulates a high energy seed electron (possibly a cosmic ray secondary) accelerated by the electric field above a thunderstorm (Taranenko and Roussel-Dupré(1996),Lehtinen et al.(1996),Roussel-Dupré et al.(1998)). If the seed electron has enough kinetic energy, a collision between the seed electron and a low energy (ambient) electron can result in two relativistic electrons. This process is predicted to produce a beam of avalanching runaway electrons. Optical emissions produced from this mechanism would have a much higher characteristic energy than the quasi-electrostatic heating model predicts.