Understanding Electric Field Oscillations in Narrow Bipolar Events

New Mexico Institute Of Mining And Technology, Socorro NM

Investigators

Abstract

The lightning research community has made significant strides in determining the steps that occur during a lightning flash. However, the processes that lead to the exact moment of initiation of a lightning stroke are still under investigation. This research will bring together the lightning and signal processing communities to apply advanced techniques to interpret the copious amount of lightning data that has been collected over years of observations. The researchers aim to improve the understanding of lightning initiation, which is important for public safety. The next generation of research scientists will also be trained in cross-disciplinary research. The broader context of the studies is lightning initiation, and in particular, understanding the transition process between fast streamer breakdown and the initiation of a stepped leader. It is not known how fast positive breakdown, which does not lead to a conductive channel, transitions into a stepped leader or otherwise facilitates leader development. Understanding the physical processes that occur immediately after the initial fast positive breakdown process is important. The specific focus of this project is on Narrow Bipolar Events (NBEs), which are waveforms that are associated with the strongest source of radio frequency radiation from lightning. Oscillations in the electric field during NBE events occur during between the initial breakdown event and the later development of a stepped leader, making the NBE an important aspect of the still unknown exact process of lightning initiation. This research project will use terabytes of interferometer data, a lightning model, and advanced signal processing techniques to study three main hypotheses: 1) The oscillations are caused by a standing electromagnetic wave along the path of breakdown in the NBE; 2) The oscillations are caused by plasma waves along the breakdown path; and 3) The oscillations are caused by ion acoustic plasma waves propagating downward along the breakdown path in response to ongoing negative breakdown at the top of the channel. This project is jointly funded by the Physical and Dynamic Meteorology Program and the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.