Energetic particles and magnetohydrodynamic activity in the Swarthmore Spheromak Experiment

Results from the Swarthmore Spheromak Experiment (SSX) [M. R. Brown, Phys. Plasmas 6, 1717 (1999)] indicate that formation and partial merging of two spheromak plasmas can be described well by a magnetohydrodynamic (MHD) pict ure in which there is substantial evolution towards force free states withi n each vessel, while reconnection activity, also described reasonably well by MHD, occurs in the region of interaction. MHD simulations [V. S. Lukin , Phys. Plasmas 8, 1600 (2001)] support and provide further detail to this i nterpretation. In the present study, test particle equations are integrated using MHD data from SSX simulations to further understand the energetic pa rticle fluxes that are observed experimentally. The test particle simulatio n is run with dimensionless parameters similar to the experiment, and parti cles are permitted to escape when they encounter the simulated SSX boundari es. MHD activity related to reconnection is responsible for accelerating ch arged particles. The process includes two phases-a strong but short duratio n direct acceleration in the quasi-steady reconnection electric field, and a weaker longer lived stochastic component associated with turbulence. (C) 2001 American Institute of Physics.