1. Marc Swisdak The Second Workshop on Thin Current Sheets April 20, 2004
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 J. Drake U. of Maryland M. Shay J. McIlhargey B. Rogers
A. Zeiler
U. of Maryland
UMBC
Dartmouth College
MPP-Garching

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

4. p3d Details Also: Relativistic PIC code 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