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Ilya Silin

Anomalous resistivity due to lower-hybrid drift waves. Results of Vlasov-code simulations and Cluster observations. Ilya Silin. Department of Physics University of Alberta isilin@phys.ualberta.ca.

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Ilya Silin

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  1. Anomalous resistivity due to lower-hybrid drift waves. Results of Vlasov-code simulations and Cluster observations. Ilya Silin Department of Physics University of Alberta isilin@phys.ualberta.ca

  2. Cluster results are courtesy of A. Vaivads and Yu. KhotyaintsevIRFU,Uppsala, SwedenK.-H. Glaßmeier TU Braunschweigand E. PanovMPI für Sonnensystemforschung

  3. Outline • Thin current sheets and reconnection • Instabilities of current sheets • General perturbation theory • Vlasov-code simulations • Cluster measurements at magnetopause • Sheared magnetopause models

  4. Thin current sheets: dynamical regions Magnetopause Solar corona Magnetotail Current sheets - regions of plasma accumulation in magnetic “traps”.

  5. Magnetic reconnection C. T. Russell, Adv. Sp. Res., 2002 E. Priest, A&A, 2001

  6. Thin current sheets: separation of regions of oppositely directed magnetic field Biot-Savart law: or

  7. Instabilities of thin current sheets P. Yoon et al., Phys. Plasmas, 2002

  8. General perturbation theory Vlasov equation Wave-like perturbations Perturbations of density and current

  9. General perturbation theory After ensemble averaging Collision term integrated over velocities Effective anomalous collision frequency

  10. Anomalous collision rates Normalized to LH frequency Quasi-linear estimate (Davidson and Gladd, Phys. Fluids, 1975) Anomalous resistivity

  11. Vlasov-code simulations • initial equilibrium - Harris current sheet (Harris, Nuovo Cim., 1962) • normalization • distribution function moments

  12. Vlasov-code simulations • equations for potentials • Coulomb gauge • equations for electromagnetic fields • Vlasov equation

  13. Vlasov-code simulations

  14. Simulation results: lower-hybrid drift (LHD) waves LHD waves grow at the edges of the current sheet and gradually penetrate towards the central plane.

  15. Simulation results: kink and sausage modes The interaction of LHD waves from the edges can trigger either global kink or sausage eigen-mode.

  16. Simulation results: effective collision rates ions electrons 2D simulations with mi/me=100 electrostatic part electromagnetic part

  17. Simulation results: effective collision rates 3D simulations with mi/me=16 Our Vlasov-simulations: Bale et al., GRL (2002):

  18. Cluster magnetopause encounter March 30th 2002, 13:11:46 Z Z X Y

  19. Cluster measurements at magnetopause tangential magnetic fields normal magnetic field electric fields LHD electric fields plasma density

  20. Cluster: νeff due to e/s fluctuations tangential magnetic fields average momentum electric fields density fluctuations electric field fluctuations product of density and electric field fluctuations

  21. Cluster: νeff due to e/m fluctuations magnetic field fluctuations current fluctuations product of current and magnetic field fluctuations

  22. Observations of the magnetopause magnetic field component hodographs in local magnetopause frame: BL and BM – tangential components, BN – normal component (from Cluster s/c1 06.16.02, 00:54-00:58 and 01.15.03 00:30-01:30, courtesy of K.-H. Glaßmeier and E. Panov)

  23. Magnetopause current sheet model magnetic field hodograph ion drift velocity hodograph

  24. LHD waves at the sheared magnetopause

  25. Conclusions • The effective collision frequency calculated from results of numerical simulations and Cluster measurements is of the order of νeff ~ ΩLH • Anomalous collisions become significant only when LHD waves reach a non-linear phase • Contributions to νeff from e/s and e/m fluctuations are comparable • The dissipation due to microscopic kinetic effects becomes significant for large-scale processes, e.g., reconnection at Earth magnetopause • However, for more realistic magnetopause configuration, the situation is still not quite clear

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