A New Twist on Spheromaks
Spheromaks are self-organizing toroidal plasma configurations that
are superficially reminiscent of smoke rings. They are are potentially
promising routes to plasma-based nuclear fusion, and insight into their
formation will help in the design of future experiments - and possibly
even a clean, safe energy source. In addition, spheromak formation is
important for explaining the behavior of plasma in the solar corona,
as well as understanding the physics of jets that sprout from black
holes, galactic nuclei, and other astrophysical objects. A new experiment
sheds light on the phenomenon by capturing images of plasmas as spheromaks
form. The images above show that plasma currents that initially initially
flow in straight lines along a confining magnetic field (image I) become
twisted due to an effect known as the kink instability. The plasma currents
develop bends that twist into a helix (image II). The helix acts like
a coiled current element, or solenoid, which amplifies the original,
straight magnetic field. Above a certain threshold in the initial magnetic
field, detached plasma spheromaks are formed (image III).
