Physics Department Seminar University of Alaska Fairbanks

J O U R N A L    C L U B

Lightning, Thunder and Infrasound
John Olson
Physics Dept. / GI UAF

Benjamin Franklin first speculated that electrical forces might participate in the production of thunder during electrical storms. We have come full circle in the investigation of the infrasonic portion of thunder and its association with thundercloud electrostatics. In this talk I will review the phenomenology of the lightning stroke that produces the audible component of thunder. Theoretical models and experimental measurements agree that most of the acoustic energy associated with the lightning stroke lies at frequencies above 100 Hz. At frequencies below 10 Hz the situation becomes more complicated and sources of the infrasonic portion of the spectrum appear to be associated with the redistribution of the charge within the thundercloud. Finally, I will review recent observations of infrasound signals that have been found to be associated with Sprite events.

Friday, 30 November 2007
Globe Room, Elvey Building
3:45 PM