This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
This research aims to model the basic process by which magnetic reconnection releases energy in a magnetically dominated plasma. Since it was first proposed to explain sudden rapid energy conversion in solar flares, most investigations of magnetic reconnection in the abstract have focused on the local electric fields it requires. The results have been self-consistent local models of plasma flows and electric fields arising through small-scale phenomena such as collisions between, or dynamical separation of, electrons and ions. A small-scale electric field of this kind can produce topological changes to magnetic field lines from which the term "reconnection" derives, but cannot directly affect the magnetic energy since that is distributed throughout the large-scale magnetized volume. The research herein proposed will address the challenge, largely unaddressed to date, of how topological changes on small scales release magnetic energy stored on large scales. The proposed research will, through two complementary lines of theoretical investigation, model the dynamical response of the entire system to the sudden, localized topological change after assuming the change to have occurred. It is through this large-scale response that the magnetic field will actually achieve its lower energy state. Energy conservation demands that the dynamics somehow convert magnetic energy into other forms such as heat or bulk motion. The proposed research will develop novel time-dependent models, both analytic and numerical, from which it will be possible to answer the following questions. _ What fraction of the energy released by reconnection becomes kinetic energy versus heat? _ Are Alfven waves initiated by the reconnection, and if so how much energy do they contain? _ How do large-scale dynamics react back on the small scales? Magnetic reconnection occurs in a wide variety of magnetized plasmas including the Earth's magnetosphere (as a substorm), the solar corona (as a flare), laboratory reactor experiments (as a sawtooth crash) and astrophysical accretion disks (as a jet). Due to their disparate parameters, different small-scale processes are probably responsible for the localized electric field in these different plasmas. Nevertheless, their large-scale response to small-scale topological change will probably all be very similar, since they are all described by the same physics at these scales. All work will be conducted by Physics graduate students as part of their doctoral thesis research.
This proposal was submitted to the NSF-DoE Partnership in Plasma Science and Engineering joint solicitation 08-589. This award is being funded jointly by the Divisions of Physics and Astronomical Sciences of the Mathematical and Physical Sciences Directorate.
