p3d: Magnetic Reconnection via an Electromagnetic PIC Code

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p3d Magnetic Reconnection via an Electromagnetic
PIC Code

• Marc Swisdak
• IREAP, University of Maryland
• NERSC User Group Meeting
• Argonne National Laboratory
• May 29, 2003

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One of Many Codes

• J. Drake, M. Shay Magnetic Reconnection
• Hall MHD
• B. Dorland Collisionless magnetized turbulence
• Gyrokinetic
• B. Kleva Tokamak edge turbulence
• Braginskii fluid

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Magnetic Reconnection A process whereby magnetic
energy, B2, is converted into thermal and
kinetic energy, kBT and ?v2.
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Cartoon Reconnection
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Magnetic Reconnection is Ubiquitous
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Q Why PIC? A Its closer to the real physics.

• The major alternative, MHD, is a fluid
  approximation. It only agrees with real-life
  reconnection after some unnatural tweaking.
• Small spatial and short temporal scales,
  turbulence and wave-particle interactions in
  particular, are completely missed.

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Equations
Maxwell
Newton-Lorentz
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Algorithms

• Gridded electromagnetic fields advanced by
  trapezoidal leapfrog, the (possibly relativistic)
  particles with a Boris algorithm.
• Discretization errors accumulate to form a
  secular violation of Poissons equation
• This can be solved via FFTs, but they make BCs
  more difficult and have some parallelization
  issues. The multigrid treats the different
  scales on different grids, each with an
  appropriate timestep.

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Scaling

• ? 50 slower at 1024 than at 16 processors
• Efficiency About 20 of maximum at 1 processor,
  ? 8 for 1024 processors

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3-D Magnetic Reconnection

• Recent work Drake et al. Formation of
  Electron Holes and Particle Energization in
  Magnetic Reconnection, Science, 299, 873, 2003.
• Followup run 15 hours on 64 nodes (1024
  processors)

Jz
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Turbulence at the X-line

• Electron holes and associated wave-particle
  interactions can have a significant effect on the
  progression of reconnection.

Ez
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Future Challenges

• Comparisons with data
• Particle heating
• Observations of turbulence
• Larger domains
• Connect with fluid codes
• What can be said about the global aspects of
  reconnection?
• Managing output
• Movies
• Initialization/restart files

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