Research Status and Plans on Magnetic Reconnection for CMSO

1. Research Status and Planson Magnetic Reconnection for CMSO Experimental progress: M. Yamada Theoretical progress: A. Bhattacharjee 10/17/2011

2. Response to the PAC report • Recommendations: • Engage planning activities of future research • Strengthen ties with space & astrophysical communities • Responses • Interaction with Fermi group • Cross-discipline analysis of reconnection layer profiles MRX-LANL MRX-UNH, MST-UNH-UW • Expanded research on flux rope problem • Start designing a next generation device • NASA S&T research started in relationship to MMS

3. Reconnection Particle Acceleration in Crab Nebula γ-Flares • AGILE and FERMI satellites recently discovered 1-day-long γ-ray flares (100 MeV – 1 GeV) in Crab Nebula. • Emission is believed to be synchrotron, but it is above the standard upper limit on synchrotron photon energy: • [Electric force fE=eE]= [Sync. Rad. Reaction frad=2/3 (reγB)2] • => Synch. photon energy: εmax= γ2maxħωc = 160×(E/B) MeV • Classical acceleration mechanisms: E<B  εmax< 160 MeV • => the flares challenge classical acceleration theories! AGILE/FERMI γ-flare X-rays (Chandra) • Uzdensky, Cerutti, Begelman (2011) model: • E < B can be violated in reconnection layers •  can have εmax>160 MeV there. • Emitting PeV particles: ρL ~ 3x1015cm ~ L ~ 1 light-day • motion is controlled only by large-scale fields. • Particles travel in rel. Speiser orbits, get focused deep into reconnection layer, towards layer midplane, forming a thin fan beam. • Deep in the layer, Bis small and synch. radiation reaction reduced. • Particles reach higher energies and emit photons with ε > 160 MeV!

4. Recent Progress in Experimental Reconnection Research • Local reconnection layer physics • Collaborative study of e-diffusion layer (MRX-LANL) • Impulsive reconnection (MST, MRX) • Study of flux ropes (MRX, LANL) • Ion heating study continues (MST, MRX) • Systematic study of guide field effects (MRX) • Global boundary effects on reconnection studied • Multiple reconnection processes (MST, MRX, RSX) • Line tying effects (RWM, MRX) • FRC reconnection restudied (LANL) • Plasma jog experiment performedin collaboration with MMS (NASA)

5. Energetic ion tail created during impulsive reconnection events in MST Neutral particle flux reveals ion distribution • Ion distribution well described by fion(E)= A e –E/kT + B E –γ • Power-law tail origin: Mechanism unknown • Energetic ions are well confined collisionless heating at reconnection events 6 4 2 0 TailSpectral Index, g ⬆ ion tail enhanced –1.5 –1.0 –0.5 0 0.5 1.0 1.5 ⬆ classicalslowing-down? Time (ms) (relative to reconnection event) Time (ms)(relative to reconnection event)

6. Nonlinear, resistive MHD simulations (DEBS) exhibit quasi-periodic magnetic relaxation events (sawteeth) much like in MST • Sawooth cycle robust only at high Lundquist number, S ~ 106 (MST value) • Since the fast “crash” is captured by single-fluid physics, suggests the limit cycle is controlled by nonlinear interaction of multiple tearing sites • “Neoclassical” resistivity (trapped electron effect) agrees better with experiment Tearing Mode Evolution “Neoclassical” “Spitzer”

7. How does impulsive reconnection occur in solar flare or space? Ohtani, et. al., 1992 ? Disruptions Flux Ropes Multiple X-line reconnection MST and MRX Observations

8. Current layer observed to disrupt over a fast timescale in MRX APS News Release 2011

9. A jog experiment on MRX (2011) In Collaboration with UNH, NASA(MMS), UC-Berkeley,

10. Minimum variance coordinate analysis is evaluated 109771Text Book Case 4 satellite probes traverse the diffusion region

11. Minimum/Maximum Variance Analysis • Coordinate system • x : normal direction (R, in MRX) • y : out-of plane direction (T, in MRX) • z : along the reconnecting magnetic field (Z, in MRX) • Fundamental assumption – 1D model of the layer In reality, due to 2D and 3D internal structures and temporal changes, the normal component varies. • MVAB does not generate a reliable normal vector in the MRX jogging experiment. • MVAB is good for determining the maximum varying magnetic field (Bz). • Agrees with Mozer and Retino 2007 JGR

12. Ion flow vector diagram obtained by plasma jog Mach Probe data

13. Ion and Electron Flow Profiles in 2-Scale Diffusion Layer Measured by MRX plasma jog experiment Verification of two-scale diffusion layer Space potential profile measured & compared with Wygant (2005)

14. Systematic Study of Guide Field Effects on Reconnection on MRXSteady-state guide field is applied to reconnection layer GF = -35 Gauss GF = 0 GF = +35 Gauss In Collaboration with UNH

15. Subtracting the paramagnetic field, the remaining quadrupole components are of comparable magnitude. Right half-plane average (black) Remaining QF Component (Black – Red) / 2 Left half-plane average (red)

16. Normalized Reconnection Rate Decreases with Guide Field => MST MST <= Analysis underway: including guide field pile-up, reduction of Hall effects, or modification of reconnection layer geometry. The results will be collaborated with MST experiments

17. Reconnection in weakly ionized plasmas on MRX • In collaboration with E. Zweibel and L. Malyshkin: Ion-neutral drag can influence reconnection rate. (PoP, Nov. 2011) • Transition to Hall reconnection predicted to occur when where is the effective ion mass • Study effect on qualitative features such as the out-of-plane quadrupole field (below). (left) QF in typical MRX conditions: ~50% ionized (right) QF in ~1% ionized plasma. Plasma current is similar in both cases.

18. Coronal Loop Model Interaction of current channels on RWM

19. MRX Magnetic Flux Rope Experiments Magnetic Axis Equilibrium Reconstruction • These flux ropes are magnetized partial-toroidal arc discharges formed between two copper electrodes • Magnetic probes and a fast camera are used to analyze the evolution of the flux rope discharges Shot 108312 Shot 108307

20. Flux Rope Boundary Conditions & Stability • MRX flux ropes are unstable to the ideal external kink mode • Ryutov et al. predicts that the kink stability threshold can change with changing boundary conditions (fixed vs. free) Fixed BC Free BC 3.5 cm Anode 7.5 cm Anode • Above, magnetics data from discharges with different boundary conditions are compared to the linear eigenmodes predicted by Ryutov (modulus in gray) • Quantitative stability analysis is ongoing • RSX Fixed BC Fixed BC 3.5 cm Cathode 3.5 cm Cathode

21. New access to astrophysical reconnection small resistivity large size Ji & Daughton (2011)

22. Conceptual Engineering Design Also Underway

23. Summary  Progress has been made in plasma jog experiments • Minimum Variance Analysis does not work well on MRX jogging experiment • Maximum Variance Analysis does work well • Ion flow vector plots measured at the neutral sheet • Electric potential profiles measured. • Local and global aspects of impulsive reconnection experimentally studied MRX and MST • Key physics yet to be determined for mechanisms of particle acceleration and heating • Systematic guide field reconnection research restarted • Hall fields survive even with a large guide field • Reconnection rate decreases rapidly with B_g/B_rec • Reconnection in partially ionized plasmas: Theory and experiments

24. Midcourse plansfor magnetic reconnection research • Near term focuses Effects of guide field (Hall effects, reconnection rate) Global reconnection and boundary conditions (including line tying) Particle acceleration and heating • Find principles for global reconnection phenomena 3-D effects (Global instability) Impulsive reconnection • Preparation for a new-generation reconnection experimental facility Flux rope reconnection Particle acceleration and heating