Topic 1: MHD Modeling of Edge Localized Modes in Tokamaks

Edge localized modes (ELMs) are quasi-periodic bursts in high confinement tokamaks that lead to energy and particle losses from the edge region, which can be potentially damaging to the divertor and first walls of the next step fusion devices. Since early 1990s, ELMs have been routinely observed in major tokamak experiments worldwide, and over the last decade, several promising ELM suppression schemes have been discovered as well as designed for ITER. In the meantime, MHD theory and simulations have been particularly successful in interpreting certain features of ELM experiment observations. However, the physics understanding of the onset process and the suppression mechanism of ELMs remains far from being complete. In this talk, I am going to review our recent and ongoing work on MHD modeling of ELMs in those aspects, and propose new directions for future exploration.

 

Topic 2: Onset of Aurora Substorms: Trigger and Catalyst

Aurora substorm is a quasi-cyclic pattern of aurora display over the entire polar upper atmospheric region. It has been widely believed that the onsets of aurora substorms originate from the plasma processes in Earth's magnetotail. However, the exact mechanism for the trigger of an aurora substorm onset has not been well understood. Two major candidates for the trigger mechanism, magnetic reconnection in the middle magnetotail and ballooning instability of the near-Earth plasma sheet, are examined in light of recent progresses in observations and theory analyses. A new scenario is discussed, in which an axial tail instability can be facilitated by the ballooning instability in the near-Earth magnetotail and lead to the subsequent magnetic reconnection and substorm onset. Multi-point in-situ observations and emerging laboratory space plasma experiments, continue to provide unprecedented opportunities in testing and advancing our understandings of the substorm process and associated basic plasma physics.

Dr. Zhu is currently an associate scientist working at the University of Wisconsin-Madison. He received his B.S. in physics from Fudan University, his M.S. in plasma physics under Prof. Shih-Tung Tsai in the Institute of Physics, Chinese Academy of Sciences, and his Ph.D. in plasma physics under Prof. Wendell Horton from the University of Texas at Austin. After working with Prof. Bhattacharjee in both Iowa and New Hampshire, he has joined the group of Profs. Hegna and Sovinec in Wisconsin. His recent research focuses on the edge stability physics in fusion and the substorm problem in space, through the approach of theoretical and computational plasma physics.