February 15, 2006
American Center for Physics
College Park, MD
Magnetic fields play a fundamental role in the dynamics of a variety of plasma systems, ranging from laboratory fusion experiments to the solar corona and astrophysical accretion discs. Observations indicate that the dissipation or release of magnetic energy typically occurs in explosive events, examples being solar and stellar flares, substorms in the Earth's magnetosphere, and disruptions in laboratory fusion experiments. The energy release occurs through a process called magnetic reconnection, in which regions of oppositely directed magnetic field self-annihilate, converting magnetic free energy into energetic beams, high velocity flows and thermal energy. The challenge has been to understand the explosive nature of these events. The magnetic field topology close to the region where the magnetic field reverses plays a major role in controlling the rate of energy conversion and that changes in topology can only occur in a narrow boundary layer around the region of reversal of the magnetic field. Thus, the release of magnetic energy in a macroscopically global system is controlled by the dynamics of a boundary layer at very small scales. There has recently been great progress in understanding the structure of this reconnection boundary layer and in particular the role of dispersive waves in facilitating the fast release of magnetic energy. The talk will review key observational data and emphasize basic physical principles to introduce the topic to the non-specialist.
Dr. Drake is a Professor in the Department of Physics and the Institute for Physical Science and Technology at the University of Maryland, College Park. He received his PhD from UCLA in 1975 and has been at the University of Maryland since 1978. Dr. Drake's research focus is on the theory of high temperature plasma. He is considered one the world's authorities on magnetic reconnection. He is the former Chair of the Division of Plasma Physics of the APS and is presently the DPP Councillor and a member of the APS Executive Board. He is an Associate of the National Academies, the winner of the Humboldt Senior Scientist Research Award and a former DPP Distinguished Lecturer