1. National Undergraduate Fellowship Program in Plasma Physics and Fusion Engineering Plasma Astrophysics Michael Brown Swarthmore College June 2007 Outline Brief plasma review (B-fields and MHD) Two important paradigms Astrophysical objects (solar flares to galactic jets) Astrophysical processes (dynamos, reconnection and pulsars)

2. Astrophysical Plasma Review Magnetic fields… related to electric fields by Lorentz transformation Q: why are there large scale B-fields but no large scale E-fields in the universe? A:...there are lots of electric monopoles around to short out electric fields B-fields are associated with currents but do currents cause B- fields are vice-versa? exert forces on currents Force=JxB contain energy

3. Astrophysical Plasma Review Newton II: Maxwell’s eqs: equations of MHD Ohm’s Law: induction eq. (curl of Ohm):

4. Astrophysical Plasma Review ramifications of MHD

5. Astrophysical Plasma Review Frozen-in Flux high conductivity: Coulomb collisionality drops with T (so  ~ T -3/2 ) universe is an excellent conductor of electricity almost everywhere frozen-in flux: assume perfectly conducting magnetofluid no electric field in a perfect conductor if field lines move with respect to fluid then an electric field is induced therefore fields move with the fluid!

6. Poynting Vector

7. Simple 2D Reconnection Theory (Sweet/Parker)

8. Reconnection Rate where R m is based on the Alfven velocity in the bulk magnetofluid and on the largest scale of the system L. M alf is a dimensionless measure of the reconnection rate or the rate at which magnetic field lines are annihilated or the direct electric field. More sophisticated models [Petschek, 1964 and Vasyliunas, 1975] predict a faster reconnection rateand a smaller ration of u out /u in. It appears, however that a bound exists: