Analytical Expressions for Lightning Electromagnetic Fields With Arbitrary Channel-Base Current—Part I: Theory

The article provides analytical expressions for the electromagnetic fields generated by a lightning return stroke characterized channel-base current with arbitrary time waveform, in presence of either perfectly conducting or lossy ground, assuming transmission line model along channel. In this second case, time-domain expression Cooray-Rubinstein formula is presented. main idea that leads to derivation formulas consists dividing channel into intervals which distance between field source point and observation can be approximated linear function time, spatial coordinates both points. companion aticle, detailed comparison proposed classical (numerical) approach highlighting an excellent agreement at close far distances, considering all values practical interest ground conductivity. Moreover, method guarantees meaningful improvement computational performance.