Contributions Contributions within Discipline:As described above, we have identified spontaneous magnetic reconnection events in VTF. We find that the onset of reconnection is Three-dimensional, which is in contrast to the assumptions applied in most numerical simulation schemes. A Physical Review Letter was recently accepted for publication, detailing a new onset model for reconnection. Also we have derived new equations of state for guide-field reconnection. These equation has been extended to the case without a guide magnetic fields and control the structure of the inner reconnection region (see publications by A. Le et al. and J. Ng et al.) Contributions to Other Disciplines: Our recent finding on spontaneous reconnection is acquiring significant interest from scientists working on reconnection in the Earth magnetosphere and the Sun's corona.

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Magnetic reconnection is an important process in magnetized plasmas ranging from the laboratory to astrophysical scales. It enables the release of magnetic energy believed to power solar flares and magnetospheric substorms. Reconnection also controls the evolution of the topology of the magnetic field, enabling deleterious instabilities, such as the sawtooth instability in fusion experiments, to transport plasma across the experiment's minor radius. Notably, simple estimates of the finite reconnection rate due to classical resistivity fail to explain the fast and explosive nature of reconnection observed in these systems. A major goal of reconnection research is to determine which mechanisms enable "fast" reconnection to occur.This thesis studied the fluctuations arising in the plasma during magnetic reconnection experiments on the Versatile Toroidal Facility (VTF), with a primary goal of testing whether "anomalous resistivity" due to micro-instabilities can speed the reconnection process. Fluctuations were studied using impedance-matched, high-bandwidth Langmuir probes. Strong, broadband fluctuations, with frequencies extending from near the lower-hybrid frequency [f LH = (f ce f ci ) 1/2 ] to the electron cyclotron frequency f ce were found to arise during the reconnection events. Based on frequency and wavelength measurements, lower-hybrid waves and Trivelpiece-Gould waves were identified. The lower-hybrid waves appear to be driven by strong perpendicular drifts or gradients which arise due to the reconnection events; an appealing possibility is strong temperature gradients. The Trivelpiece-Gould modes were found to result from kinetic, bump-on-tail instability of a runaway electron population energized by the reconnection events. Nonlinear, spiky turbulence was also observed, and attributed to the creation of "electron phase-space holes," a class of nonlinear solitary wave known to evolve from a strong beam-on-tail instability.Overall, these instabilities were found to be a consequence of reconnection, specifically the strong energization of electrons, leading to steep gradients in both coordinate-and velocity-space. However, it was not established that these modes had a strong feedback on the reconnection process: fluctuation power varied strongly between discharges and was observed to systematically trail the reconnection events. Finally, crude estimates (using quasi-linear theory) of the anomalous resistivity due to these modes did not appear large enough to substantially impact the reconnection process.