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The Structure of Thin Current Sheets Associated with Reconnection X-lines. Marc Swisdak The Second Workshop on Thin Current Sheets April 20, 2004. Collaborators. U. of Maryland. J. Drake M. Shay J. McIlhargey B. Rogers A. Zeiler. UMBC. Dartmouth College. MPP-Garching. z. y. x.
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The Structure of Thin Current Sheets Associated with Reconnection X-lines Marc Swisdak The Second Workshop on Thin Current Sheets April 20, 2004
Collaborators U. of Maryland • J. Drake • M. Shay • J. McIlhargey • B. Rogers • A. Zeiler UMBC Dartmouth College MPP-Garching
z y x Simulation: J Bguide Breconn Reconnecting field: x Inflow velocity: y Guide field/Current: z
p3d Details • Also: • Double Harris sheet • Periodic BCs • Relativistic PIC code • Boris algorithm for particles • Trapezoidal leapfrog for fields • Multigrid for Poisson’s equation • MPI parallelization • Biggest runs: • 512x256x256 • 2048 processors • ~109 particles • How we cheat: • me/mi large • c/cA small
The Point Q: At what strength does the guide field become important? A: Bg 0.1 B0
Velocity Distributions @ x-line: Beams are due to Speiser figure-8 orbits @ bifurcation: Multiple peaks from two beams
Balancing the Reconnection Electric Field Ideal MHD Pressure tensor Electron Inertia
Guide Field: Bg=1B0 • Current sheet not bifurcated • Electrons magnetized at the x-line • Canted separtrices • E|| interacting with Bg
Guide Field Criterion • What is the minimum Bg so that the e- excursions are less than de? Reconnection Rate:
X-line Distribution Functions Why is this important? Development of x-line turbulence. Why does it happen? Bg means longer acceleration times.
Conclusions • Bg ~ 0.1B0 is enough to influence the structure of x-lines. • Affects: Flow geometries, separatrices, particle orbits (temperatures), particle energization, development of turbulence (?) • Doesn’t affect: Reconnection rate, breaking of frozen-in condition • Implication: Anti-parallel reconnection is rare in real systems. Most reconnection is component reconnection