Honors Theses

Date of Award


Document Type

Undergraduate Thesis



First Advisor

Thomas Marshall

Relational Format



Narrow bipolar pulses (NBPs) are a class of high-altitude, high-energy discharges that occur during some thunderstorms. The mechanism responsible for initiation of these discharges is not known, but a explanation called runaway breakdown has been proposed by Gurevich et al. 2004. In runaway breakdown, fast ‘seed’ electrons are continually accelerated by the ambient electric field causing the discharge. As the runaway electrons collide with atoms in the air, they create a cascade of other runaway electrons as well as slower free electrons. In accordance with this suggestion, we model a current that increases exponentially along its propagation channel (MTLEI). The electric fields resulting from the model were compared to measured electric field data from a single NBP collected at near and far field locations. We were unable to fit the measured data using the fast current propagation speeds appropriate for a runaway breakdown mechanism. Instead, by using currents that travel relatively slowly (6 X 10"^ m/s), the MTLEI model fit the data reasonably well. This result is compatible with a mechanism that uses runaway breakdown to produce charge carriers along with a moving electric field to drive the main NBP current.

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