CTQM Seminar Type:
- Related Seminar Series
Abstract, Event Details:
Plasma makes up 99.9% of the visible matter in the universe and is crucial to building a working fusion power plant, but many fundamental processes that occur in space and laboratory plasmas remain poorly understood. Interesting unsolved problems abound: Why is the outer layer of the sun (the solar corona) much hotter than the photosphere below, when from adiabatic considerations we would expect the reverse? How can we reduce losses to improve the performance of fusion plasmas? What determines the evolution of space weather that can damage our sensitive infrastructure? I will discuss fundamental plasma physics as the key to solving these and other problems, focusing on two examples: magnetic reconnection and non-linear physics of Alfvén waves.
Magnetic reconnection is an important energy release mechanism to consider in contexts such as eruptions on the sun and loss of plasma in experimental fusion devices. In both cases, a slow build up phase is followed by a quick release of magnetic energy, but this impulsive behavior is not fully understood. I will show results from a dedicated laboratory experiment at Princeton University in which 3-D physics is necessary to explain the observed impulsive events. The experiments have key features in common with space observations that will inform future comparative studies.
Alfvén waves are fundamental modes of a plasma with a magnetic field. The non-linear behavior of these waves may be key in contexts such as space weather and the scattering and loss of energetic particles in fusion devices. One important non-linear process with a long history of theoretical and simulation studies is a class of parametric instabilities in which a large amplitude Alfvén wave produces various daughter modes. I will show results from recent experiments at the Large Plasma Device at UCLA which represent the first observation of this type of instability in the laboratory.