Ultra-wideband (>1 GHz) electromagnetic measurements of lab-based discharges and comparisons with lightning

Abstract:

The broadband radiofrequency (RF) signals emitted by lightning leaders and streamers can be measured and characterized to provide estimates of lightning’s physical parameters, e.g., current- and charge-moment change, power emitted, even the physical extent of the breakdown by using networks of radio sensors [Rison et al., Nat. Commun., 7, 10721, 2016; Tilles et al., Nat. Commun., 10, 1648, 2019; Liu et al., J. Geophys. Res. Atmos., 124, 2019]. However, it is extremely difficult to obtain coordinated RF measurements of lightning with in-situ measurements such as electric current through the lightning channel, and in the case of in-cloud lightning such coordinated observations are impossible. However, coordinated observations are readily achievable in the lab. Here we present ultra-wideband (>1 GHz) RF observations of high-voltage (>20 kV), high-current (10 to 200 kA) experiments performed at Sandia National Lab. The experiments involve current sources of known geometries, e.g., current through a straight wire, as well as air breakdown, with current rise times on the order of 1 to 100 microseconds. By comparing the measured RF signals with similarly wideband measurements of electric potential and current as a function of time, we fully characterize the energy in the discharging system and test the accuracy of the RF-based estimates. The results inform similar RF-based estimates of the current and charge involved in lightning.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.