Onset of Fast Magnetic Reconnection in Laboratory and Space Plasmas

The onset of fast magnetic reconnection is widely studied in laboratory
experiments, in situ satellite measurements in the Earth’s magnetosphere, and solar
flares. These observations place strong constraints on theory, which must explain
not only a fast reconnection rate but also a sudden increase in the time-derivative of
the reconnection rate. We will show by means of theory and high-resolution
simulations that such dynamics can be accounted for in one unifying framework by
means of the Hall MHD model. The problem takes on additional complexity when it
is applied to large systems, which have been the subject of considerable interest
recently. Thin current sheets in systems of large size that exceed a critical value of
the Lundquist number are unstable to a super-Alfv énic tearing instability, referred to
as the plasmoid instability because it is a copious source of plasmoids (or magnetic
islands). As a result of this instability, the system is shown to realize a fast nonlinear
reconnection rate that is independent of the Lundquist number of the plasma.
Dr. Amitava Bhattacharjee is Paul Professor at the Space Science Center and
the Department of Physics at the University of New Hampshire. He received his
Ph.D. at Princeton University in theoretical plasma physics from the Department of
Astrophysical Sciences. He and his students and postdoctoral colleagues have
authored over 200 publications with broad applications to laboratory (including
fusion), space, and astrophysical plasmas. He is a Fellow of the American Physical
Society, and the American Association of Advancement of Science. He has recently
served as Chair of the Division of Plasma Physics of the American Physical Society,
and as Senior Editor of the Journal of Geophysical Research – Space Physics