Standing Shock Regulates Sparks in Explosive Flows*

Recent observations of explosive events in nature [1] and decompression experiments [2] indicate that explosive flows may alter electrical discharge processes, suppressing parts of the hierarchy of the discharge phenomena, such as leaders. In the experiments, a shock tube ejects a flow of gas and particles into an expansion chamber. We imaged an illuminated plume from a decompression of argon and a small amount of diamond particles and performed simulations. The discharges occur below the sharp boundary of a condensation cloud that agrees closely with a Mach disk shock in shape and height. This represents direct evidence that the spatial and temporal scale of the discharges transmit an impression of the shock tube flow, a connection that could enable novel instrumentation to diagnose currently inaccessible supersonic granular phenomena. [1] Behnke, S. A., et al. (2018). J. Geophys. Res. Atmos., 123(8). [2] Méndez-Harper, J. S. et al. (2018). Geophys. Res. Lett., 45(14).