

Articles
by
Susan K. Earles 
Total Records (
2 ) for
Susan K. Earles 





Scott L. Meredith
,
Susan K. Earles
and
Niescja E. Turner


Problem statement: Develop a new formula which describes the horizontal electric field induced by a lightning return stroke in contact with an imperfect conductive surface. Approach: A new method for describing the horizontal electric field induced by a lightning return stroke will be presented. The method presented here had utilized an approach which purposely downplayed the physics of how image theory was employed in the presence of an imperfect conductive surface. It did so by adopting a technique which had focused on the geometry that existed between the lightning channel and surface ground. In doing so, new expressions for surface currents had been derived. This study presented the derivation of these currents along with the horizontal electric field which transpired as a result of their usage. Results: The equation derived had elicited the concept that the channel’s image varies with surface conductivity. Conclusion: A method for deriving the horizontal electric field induced by a lightning return stroke had been presented. As the results had shown, once the surface conductivity began to decrease, the horizontal electric field played an increasingly more significant role. 




Scott L. Meredith
,
Susan K. Earles
,
Ivica N. Kostanic
and
Niescja E. Turner


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 closedform 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 closedform. 





