Professor Umran S. Inan

Winter 1998-99

Date: Wednesday, March 3, 1999
Time: 4:15-5:30 PM; Refreshments at 4:00 PM
Location: GESB 124

Theoretical Models of Sprites

Dr. Victor Pasko
STAR Laboratory, Stanford University


Spectacular luminous optical emissions appearing in clear air above thunderstorms and known as sprites provide dramatic evidence of strong electrodynamic coupling between tropospheric lightning discharges and the mesosphere/lower ionosphere. In this talk we will provide a review of existing interaction and coupling mechanisms proposed for the explanation of experimentally observed features of sprites (i.e., their spatial structure, optical spectra and time dynamics). We will discuss the conventional as well as the relativistic runaway breakdown processes stimulated at mesospheric altitudes by large quasi-electroctatic field transients following intense positive cloud to ground lightning discharges, and the role of these two breakdown mechanisms in sprite production. We will also discuss the properties of sprites on a variety of spatial scales, including their fine spatial structure (~1 m), as well as their contribution to the large scale atmospheric electric circuit (scales ~100 km).