An Advanced Model of Lightning M‐Component

Abstract

AbstractAn advanced nonlinear and nonuniform distributed circuit (RLCG) model of lightning M‐component has been developed. The model accounts for the variation of the series resistance R of M‐component channel due to its heating by the transient current and its subsequent cooling, longitudinal voltage drop along the channel due to the background continuing current, ohmic losses in the channel corona sheath (represented by shunt conductance G), and variation of series inductance L and shunt capacitance C of the channel with height above ground. The model was tested against the channel‐base current and corresponding close electric fields measured for seven M‐components in negative lightning triggered using the rocket‐and‐wire technique. Detailed sensitivity analysis was performed for one M‐component. The influences of height‐varying series inductance and shunt capacitance and the length of in‐cloud channel (representing the excitation source) on the computed current and field waveforms were found to be relatively insignificant, while the influences of ohmic losses in the channel corona sheath and voltage drop along the grounded channel were significant. The effects of background continuing current level and grounding resistance were significant for M‐field, but not for M‐current. Model‐predicted overall power and current profiles below the cloud base are consistent with the observed M‐component luminosity profiles and are drastically different from the observed downward leader/upward return stroke profiles. The characteristic feature of M‐components, the time shift between the current onset and close electric field peak (essentially absent for leader/return stroke sequences), was well reproduced by our model.