Research on Plasma Astrophysics
Princeton has a long tradition of excellence in the field of plasma astrophysics, dating back to Lyman Spitzer's pioneering work on the physical properties of interstellar gas. This tradition continues with active research in plasma astrophysics involving collaborations throughout the Princeton area -- including the Department of Astrophysical Sciences, the Princeton University Program in Plasma Physics (which is also part of the Department of Astrophysical Sciences), the Princeton Plasma Physics Laboratory (PPPL), and the Institute for Advanced Study -- as well as with the Max Planck Institutes for Plasma Physics in Garching and Greifswald. Key research topics include magnetic reconnection (Stephen Jardin, Hantao Ji, Russell Kulsrud, Stewart Prager, Anatoly Spitkovsky, Masaaki Yamada), angular momentum transport in accretion disks (Princeton Magnetorotational Instability [MRI] Experiment, Jeremy Goodman, Greg Hammett, Hantao Ji, Matthew Kunz, Stewart Prager, James Stone), collisionless shocks (Jeremy Goodman, Anatoly Spitkovsky), solar-wind plasma physics (Amitava Bhattacharjee, Matthew Kunz), and the physics of high-energy-density plasmas (Ron Davidson, Nat Fisch). Magnetic reconnection (Magnetic Reconnection Experiment; MRX) is a key subject to identify physical mechanisms responsible for rapid changes in magnetic field topologies and associated release of magnetic energy commonly observed in magnetospheric storms, solar corona, accretion disks, and compact objects, as well as laboratory plasma experiments.
Rapid accretion rates are commonly observed in many kinds of accretion disks and are necessarily accompanied by rapid transport of angular momentum. Often turbulence is evoked for this purpose. The detailed mechanisms to generate the needed turbulence is an active topic of investigation at Princeton. Detailed mechanisms for forming a shock and converting flow energy into particle thermal energy are of interest in order to interpret the observed emissions from supernova explosions and their remnants. These shocks are often collisionless, in the sense that the collisional mean free path is much larger than shock thickness. Extreme pressures and temperatures, ordinarily associated with astrophysical phenomena, are now being produced terrestrially through extreme compression of plasma to achieve thermonuclear fusion. The recently completed National Ignition Facility (NIF) at Lawrence Livermore Laboratory is an example where very high power lasers produce this compression. Theoretical investigations at Princeton are examining processes that enable these conditions or that result from subjecting matter to these extreme conditions.