Final Scientific Report: Experimental Investigation of Reconnection in a Line-tied Plasma

Technical Report · Tue Oct 25 00:00:00 EDT 2016

DOI:https://doi.org/10.2172/1329924· OSTI ID:1329924

Forest, Cary ^[1]

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1. Univ. of Wisconsin, Madison, WI (United States)

This grant used funding from the NSF/DoE Partnership on Plasma Science to investigate magnetic reconnection phenomena in a line-tied pinch experiment. The experiment was upgraded from a previous device intended to study fusion plasma-related instabilities to a new configuration capable of studying a number of new, previously unstudied configurations. A high spatial and time resolution array of magnetic probes was constructed to measure time evolving structures present as instability and turbulence developed. The most important new equilibrium made possible by this grant was a Zero-Net-Current equilibrium that models the footpoint twisting of solar flux tubes that occurs prior to solar eruptions (flares and coronal mass ejections). This new equilibrium was successfully created in the lab, and it exhibited a host of instabilities. In particular, at low current when the equilibrium was not overly stressed, a saturated internal kink mode oscillation was observed. At high current, 2 D magnetic turbulence developed which we attribute to the lack of a equilibrium brought about by a subcritical transition to turbulence. A second set of experiments involved the turbulent interactions of a collection of flux tubes all being twisted independently, a problem known as the Parker Problem. Current profiles consisting of 2, 3 and 4 guns were used to impose a fine scale drive, and resulted in a new experimental platform in which the injection scale of the magnetic turbulence could be controlled. First experiments in this configuration support the conclusion that an inverse cascade of magnetic energy occurred which self-organized the plasma into a nearly axisymmetric current distribution.

• Research Organization: Univ. of Wisconsin, Madison, WI (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• DOE Contract Number: SC0008708
• OSTI ID: 1329924
• Report Number(s): DOE-UW-8708-1; TRN: US1700419
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
79 ASTRONOMY AND ASTROPHYSICS
ELECTRIC CURRENTS
EQUILIBRIUM
PLASMA
PINCH EFFECT
TURBULENCE
CONFIGURATION
PLASMA INSTABILITY
AXIAL SYMMETRY
MAGNETIC PROBES
SOLAR FLUX
TUBES
MAGNETIC RECONNECTION
OSCILLATION MODES
DISTRIBUTION
SOLAR FLARES
ERUPTION
PLASMA GUNS
MASS
SOLAR CORONA
Solar Flares
MHD
Plasma Physics