The Magnetic Field Induced by a Lightning Strike's Indirect Effect Double Exponential Current Waveform

Problem statement: Develop a new formula which describes the magnetic field induced by a lightning strike’s indirect effect double exponential current waveform. Approach: A novel approach for developing a closed-form solution for the magnetic field from the indirect effect double exponential current waveform will be presented. In the literature, models typically employ the pulse waveform to derive the corresponding electromagnetic fields. However, given the Department of Defense (DoD) has incorporated the double exponential current waveform as part of their “Electromagnetic Environmental Effects Requirements For Systems”, we felt it important to develop a solution for the magnetic field which utilized this waveform. In order to facilitate the integration required for deriving the field, Taylor series expansion was used for all variable dependent exponential terms. In many publications, the dipole and monopole techniques have been used when solving for the magnetic field. However, for this study the dipole technique was deemed the preferred method for evaluating the field. A derivation of the magnetic field will be presented along with a graphical illustration of the field’s distribution over time. Results: The equation presented utilized Taylor series to augment the integration required to solve for the magnetic field. Conclusion: A new method for deriving the magnetic field induced by a lightning strike’s indirect effect double exponential has been presented. By approximating the variable dependent exponential terms, we were able to minimize the complexity of the mathematics required to solve for the magnetic field in closed-form.