Laboratory modeling in laser-induced plasma to estimate the pressure in bolide wake

Abstract

Aims. We study Fe and FeO emission in laser-induced plasma under reduced pressure to develop an approach for finding the conditions under which the laboratory plasma state matches the state of bolide wake plasma. Methods. To acquire spectra of laser-induced plasma, we ablated a target of Fe3O4 in a vacuum chamber using a Q-switched laser. The Boltzmann plot method and Stark broadening of the emission lines were used to estimate the plasma temperature and electron number density. The intensity ratios of two Fe I lines (544.61 nm and 558.69 nm) to the intensity of FeO orange band at 587.1 nm were calculated to compare the conditions in laser-induced plasma and bolide wake plasma. Results. Several combinations of pressure (75–150 Torr) and delay (12–15 μs) lead to the highest degree of similarity between laser-induced plasma and the Beneov bolide spectra at an altitude of 39 km. Importantly, the plasma parameters and pressure are consistent at these points. A detailed comparison of the spectra shows that the best-match conditions are 100 Torr and 15 μs. This pressure is ≈25 times higher than the ambient pressure at this altitude. Conclusions. We assume that the pressure in the bolide wake is higher than the ambient pressure by a factor of 20–30. This can be considered to be the upper bound estimate of the pressure in the bolide wake, and the developed approach would be beneficial to support the modeling of a meteoroid entry.