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The Structure of Thin Current Sheets Associated with Reconnection X-lines

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

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  1. The Structure of Thin Current Sheets Associated with Reconnection X-lines Marc Swisdak The Second Workshop on Thin Current Sheets April 20, 2004

  2. Collaborators U. of Maryland • J. Drake • M. Shay • J. McIlhargey • B. Rogers • A. Zeiler UMBC Dartmouth College MPP-Garching

  3. z y x Simulation: J Bguide Breconn Reconnecting field: x Inflow velocity: y Guide field/Current: z

  4. 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

  5. The Point Q: At what strength does the guide field become important? A: Bg  0.1 B0

  6. No Guide Field: Overview

  7. Development of Bifurcation

  8. Temperature

  9. Velocity Distributions @ x-line: Beams are due to Speiser figure-8 orbits @ bifurcation: Multiple peaks from two beams

  10. Balancing the Reconnection Electric Field Ideal MHD Pressure tensor Electron Inertia

  11. Balancing the Reconnection Electric Field

  12. Guide Field: Bg=1B0 • Current sheet not bifurcated • Electrons magnetized at the x-line • Canted separtrices • E|| interacting with Bg

  13. Temperature, Bg=1

  14. Balancing the Reconnection Electric Field

  15. Guide Field Criterion • What is the minimum Bg so that the e- excursions are less than de? Reconnection Rate:

  16. X-line Structure: Bg = 0, 0.2, 1

  17. Temperature, Bg=0.2

  18. Off-Diagonal Pressure Tensor, Pyz

  19. X-line Distribution Functions Why is this important? Development of x-line turbulence. Why does it happen? Bg means longer acceleration times.

  20. 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

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