| Abstract: | We report on the experimental observation of the airflow motion induced by an 800 nm, 1 k Hz femtosecond filament in a cloud chamber filled with air and helium. It is found that vortex pairs with opposite rotation directions always form both below and above the filaments. We do not observe that the vortices clearly formed above the filament in air just because of the formation of smaller particles with weaker Mie scattering.Simulations of the airflow motion in helium are conducted by using the laser filament as a heat source, and the simulated pattern of vortices and airflow velocity agree well with the experimental results. |
