Stephen Donald Terry

Electromagnetic Fluctuations during Fast Reconnection in a Laboratory Plasma

Experimental evidence for a positive correlation is established between the magnitude of electromagnetic fluctuations up to the lower-hybrid frequency range and enhancement of reconnection rates in a well-controlled laboratory plasma. The fluctuations belong to the right-hand polarized whistler wave branch, propagating obliquely to the reconnecting magnetic field, with a phase velocity comparable to the relative drift velocity between electrons and ions. The measured short coherence lengths indicate their strongly nonlinear nature.

Measurements of Magnetic Fluctuations in Magnetic Reconnection Experiment

Magnetic reconnection plays an important role in determining the evolution of magnetic topology in laboratory and astrophysical plasmas. A central question concerns why the observed reconnection rates are much faster than predictions made by classical theories, such as the Sweet‐Parker model based on MHD with classical Spitzer resistivity. Often, the local resistivity is conjectured to be enhanced by micro‐instabilities to accelerate reconnection rates either in the context of the Sweet‐Parker model or by facilitating setup of the Pestchek model. Although it is commonly believed that there is plenty of free energy available at the reconnection region to destabilize some sort of micro‐instability, a clear identification of this instability and its exact role in reconnection has never been established experimentally. We report the first such experimental evidence of a clear and positive correlation between magnetic fluctuations in the lower‐hybrid frequency range and resistivity enhancement during fast reco...

Behavior of Impurity Ion Velocities during the Pulsed Poloidal Current Drive in the Madison Symmetric Torus Reversed-Field Pinch

We report on passive measurements of impurity ion velocities during the pulsed poloidal current drive (PPCD) in the Madison Symmetric Torus reversed-field pinch. During PPCD, the electron temperature increased and a sudden reduction of magnetic fluctuations was observed. For this change, we have studied whether plasma velocity is affected. Plasma rotation is observed to decrease during PPCD. From measurements of line intensities for several impurities at 10 poloidal chords, it is found that the impurity line emission shifts outward. The ion temperature of impurities is reasonably connected to that measured by charge exchange recombination spectroscopy from core to edge. [DOI: 10.1143/JJAP.42.L505]