Data-Driven Simulations of the Lightning Return Stroke Channel Properties

Accurate estimates of the lightning channel plasma properties are crucial for quantifying the impacts of lightning in the atmosphere and on man-made structures. Gas dynamics models of the return stroke help provide a fundamental understanding of the transformation that occurs in an air parcel subject to the lightning current, yielding quantitative estimates of important channel properties, such as its radius, temperature, and energy deposition. However, until very recently, there was no dataset available in the literature that permitted proper validation of such simulation techniques. This knowledge gap was closed recently when high-speed optical spectra of triggered lightning were made available. In this article, we use measurements to drive and constrain simulations with a gas dynamic model. The model employs a number of parameterizations that allow us to rewrite the hydrodynamic problem as a set of ordinary differential equations. Comparisons with measured temperature and electron density yield errors of the order of tens of percent. The use of more accurate air-plasma transport coefficients helps improve the agreement with measurements. Additionally, we estimate key channel parameters that are not easily measured. The calculated channel radius, resistance, and deposited energy agree well with what has been previously reported in the literature.