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Role of trapped electrons in pic-code simulations of reconnection

Role of trapped electrons in pic-code simulations of reconnection. J Egedal, MIT, PSFC, Cambridge, MA Thanks to W Daughton & J F Drake.  Generalized Ohms law:. Fluid description. Navier Stoke’s equations for the electron fluid.

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Role of trapped electrons in pic-code simulations of reconnection

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  1. Role of trapped electrons in pic-code simulations of reconnection J Egedal, MIT, PSFC, Cambridge, MA Thanks to W Daughton & J F Drake

  2.  Generalized Ohms law: Fluid description Navier Stoke’s equations for the electron fluid

  3. Why is J|| limited to this small region? Works, but no equation for j||! Pic-code simulation(by Prof. W Daughton)

  4. Trapped electron in simulation by Prof. W Daughton

  5. Wind spacecraft observations in distant magnetotail, 60RE M. Øieroset et al. Nature 412, (2001) M. Øieroset et al. PRL 89, (2002) • Measurements within the ion • diffusion region reveal: • Strong anisotropy in fe.

  6. + + + + + Wind data  Thermal electrons trapped • Applying f(x0,v0) = f(|v1|) to an X-line geometry consistent with the Wind measurements • A potential, needed for trapping at low energies Theory Wind ~ -700V ~ -1000V ~ -300V J. Egedal et al., (2005) Phys. Rev. Lett. 94,025006

  7. Jy en0vth,e 9 9 9 z/di z/di z/di 0 0 0 0 0 0 0 26 26 26 x/di x/di x/di Ey Why is Jy limited to this small region? Numerical simulation (by Prof. J. Drake) Mass ratio: 225, Te=Ti=0.25, Bg=0.5B0 xz (Exz= -xz) 1.5 (=6Te) -1.0 0.8 0 -0.8

  8. Jy xz (Exz= -xz) en0vth,e 9 9 9 9 9 1.5 (=6Te) || (E||= -||) 1.5 (=6Te) z/di z/di z/di z/di z/di 0 0 0 0 0 0 0 26 -1.0 0 0 0 0 26 26 26 26 x/di x/di x/di x/di x/di Ey || (E||= -||) 0.8 1.5 (=6Te) 0 0 0 -0.8 Escape Energy = 6 Te Numerical simulation (by Prof. J. Drake) Mass ratio: 225, Te=Ti=0.25, Bg=0.5B0

  9. 9 1.5 z/di 0 0 26 x/di 0 Trajectories of thermal electrons Representative electron orbits || (E||= -||) J|| is carried by shifting electron orbits. The shift is controlled by the ions, required for quasi neutrality.

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