Bernie J. Vasquez
Astrophysics/ Solar-Terrestrial Physics
Joint Appointment Department of Physics
Ph.D., University of Maryland, College Park
Prior to joining UNH in June 1993, Dr. Vasquez completed his dissertation entitled ``Nonlinear Wave Evolution in a Dispersive Plasma: Application to Rotational Discontinuities" at the University of Maryland, College Park with Dr. K. Papadopoulos and Dr. P. Cargill. Dr. Vasquez's research interest are primarily in the area of solar wind, waves, discontinuities, ion kinetics, and numerical simulations.
Dr. Vasquez works extensively with hybrid numerical simulations in which ions are treated as particles and electrons as a quasi-charge neutralizing fluid. A typically simulation run in two space dimensions requires moving a million particles per time step and calculating electromagnetic field vectors on a grid which determine the collective forces which move particles. The great advantage of including the effects of particles is that it captures aspects of a collisionless plasma which are completely lacking in a pure fluid treatment. The solar wind is largely collisionless even near the Sun, and so the study waves and particles within this wind benefits when a hybrid treatment is employed.
Using hybrid simulations, initial states containing Alfven waves moving in different directions are studied to explain how wave nonlinearity and ion kinetics affect their evolution and appearance. In the solar wind, magnetic fluctuations show a number of properties related to Alfven waves. These tend to have nearly constant magnetic intensity, special field polarizations, a small density-field strength inverse correlation, and abrupt layers of field rotation, called rotational discontinuities. Simulations and analysis by Dr. Vasquez and Professor Hollweg have largely explained how these properties are attained. Current work focuses on how Alfven waves can interact to produce turbulent-like behavior and to drive wave power to small wavelengths where dissipation via ion heating can take place. This work is supported by a National Science Foundation (NSF) grant and a National Aeronautics and Space Administration (NASA) Sun-Earth Connection Theory Program grant.