Atlantic Building, Room 2400 4:30 PM Monday, March 1, 2010

Coffee, Tea & Snacks 4:15-4:30 PM

Peter Yoon

University of Maryland, Institute for Physical Science and Technology

"Non-Extensive Entropy and Turbulent Quasi-Equilibrium for Space Plasmas"

Charged particles detected in space rarely obey the laws of thermodynamic equilibrium in that their distributions do not follow the classic theory of Maxwell, Boltzmann, and Gauss. Instead, their distributions feature enhanced energetic population called the superthermal tails. Recently, it is suggested that the space plasma does not obey the statistical theory of Boltzmann and Gibbs, which is based upon the extensive entropy. Instead, it is suggested that the space plasma obeys an alternative statistical theory based upon the non- extensive entropy. It will be shown, however, that the non-Maxwellian charged- particle distribution can be explained in terms of turbulent quasi-equilibrium. That is, the charged particles are not in true thermodynamic equilibrium, but rather, they coexist with turbulent electromagnetic fluctuations in quasi steady state, constantly exchanging energy and momentum between the particles and the waves, but maintaining an overall balance. Whether such a turbulent quasi- equilibrium state is the same as the equilibrium state dictated by the non- extensive entropy or not remains an open question, however.