Plasma Physics Seminar ( Phys 769)

Dr. H. Karimabadi, UCSD / SciberNet, Inc. A new Asynchronous Plasma Simulation Technique - The Only Hope for Understanding Multi-scale Problems Like Reconnection? Our recent work brings to question several generally accepted concepts on collisionless reconnection and casts doubt on the current approaches to the problem. We have used a combination of linear Vlasov, full particle, hybrid, Hall-less hybrid, and Hall MHD to tackle the various aspects of reconnection in the magnetosphere. During this talk, we present results from these studies and contrast them to previous investigations. Topic areas covered include (i) reconnection onset and "saturation" in the presence of a guide field, (ii) origin of fast reconnection in a kinetic plasma, (iii) physics of quadrupole generation, (iv) stability of Sweet-Parker regime of reconnection, and (v) competition between various current sheet instabilities such as Weibel, lower hybrid and tearing mode. We present a new model for reconnection onset. We demonstrate that the complete understanding of the reconnection process cannot be achieved through existing simulation techniques within a foreseeable future. Accordingly, we present a new simulation technique that breaks the "curse" of Courant condition and eliminates computation in regions where there is no significant activity. In a 1D test, we found more than a factor of 100 speed up compared to standard techniques. The extension of this technique to various plasma modes such as MHD, Hall MHD, Full Particle, Hybrid, and Vlasov codes will be discussed.