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Turbulence in the Earth's plasma sheet

Nonlinear Waves and Turbulence in Space Plasmas (NLW-6) Oct. 9 -13, 2006, International Plaza, Kyushu University, JAPAN. Turbulence in the Earth's plasma sheet. Z. Vörös (1), W. Baumjohann (1), R. Nakamura (1), M. Volwerk (1), A. Runov (1), T. Takada (1), Y. Asano (2),

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Turbulence in the Earth's plasma sheet

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  1. Nonlinear Waves and Turbulence in Space Plasmas (NLW-6) Oct. 9 -13, 2006, International Plaza, Kyushu University, JAPAN Turbulence in the Earth's plasma sheet Z. Vörös (1), W. Baumjohann (1), R. Nakamura (1), M. Volwerk (1), A. Runov (1), T. Takada (1),Y. Asano (2), E. Lucek (3) and H. Rème (4) (1)Space Research Institute, Graz, Austria, (2) Tokyo Institute of Technology, Japan, (3)Imperial College, London, UK, (4) CESR/CNSR, Toulouse, France. Acknowledgements: T. Nagai (Tokyo Institute of Technology, Japan), T. Mukai (Institute of Space and Astronautical Science, Japan).

  2. OUTLINE • What is the true spectral scaling index in the plasma sheet? • Individual vs. multiple flows; • Anisotropy, intermittency and boundary effects • in the turbulent plasma sheet. NLW-6 (2006), Kyushu University, JAPAN

  3. Spectral scaling Plasma sheet Solar wind (Hoshino et al. 1994; Bauer et al. 1995; Borovsky& Funsten, 1997, 2003; Vörös et al., 2003, 2004, 2005; Volwerk et al., 2003; Weygand et al., 2005) (Bavassano et al., 1982; Bruno and Carbone, 2005) 1~ 0.5  1.5 2 ~ 1.7  2.9 Inertial range:  ~ 1.7 NLW-6 (2006), Kyushu University, JAPAN

  4. Transient driving – a sliding window studyCLUSTER alfaest_01Aug27_out • P(f) ~ cf f - • (scale, time) = (2j, 2j t) • j =(1/nj)tnj dx2 (j,t) • ~ 2j cf • Logscale diagram: •  and cf are estimated from • yj  log2 j versus j =log22j NLW-6 (2006), Kyushu University, JAPAN

  5. Transient driving – a sliding window studyGEOTAIL NLW-6 (2006), Kyushu University, JAPAN

  6. Spectral scaling within individual flows Selection criteria: Bx < 15 nT; <V> > 250 km/s; Small-scale activity. B T_gp [nT] [s] ======== 5 13 10 7 15 4 Dissipation range Inertial range NLW-6 (2006), Kyushu University, JAPAN

  7. Large-scale average velocity vs. dissipation scale As a flow energy (~V2 ) increases, the dissipation time scale decreases (coupling)  more energy pumped towards small-scales.  The spectral break depends on both large scale energy input and proton gyroperiod V~80 km/s V~700 km/s <V> [km/s] Vörös et al., 2005 NLW-6 (2006), Kyushu University, JAPAN

  8. Multiple flow smearing C with O M M F P U L A L O R T W I I S S P O L N E Individual flows Multiple flows: (a) smear the break; (b) hide the inertial range scaling. Reconnection related? NLW-6 (2006), Kyushu University, JAPAN

  9. Local flows vs. multiple flows - kurtosis Local flow Non-flow interval Multiple flows reconnection related?

  10. Spatial structure of turbulence: multi-point Cluster Possible flow geometry 3700 km

  11. Skewness and Kurtosis 1 1 2 2 3 3 4 4

  12. Comparisons Kurtosis Passive scalar statistics in a fluid flow (Chatwin, Robinson, 1997) Skewness Passive scalar statistics near interplanetary shocks (Vörös et al., 2006) Passive scalar statistics in the Earth’s plasma sheet (this study) Evidence for nonlocal turbulence Interactions. Boundary flows …. Non-boundary flows ….

  13. Conclusions • Turbulence in the plasma sheet is transient; • Multiple flows or badly chosen intervals mask the true inertial range scaling index, which is  ~ 1.7; • The dissipation range is well visible from high-resolution magnetic data; • Boundary effects or spatial gradients induce anisotropy and intermittency in plasma sheet turbulence. References • Vörös et al., Ann. Geophys., 2003, 21, 1955; • Vörös et al., Phys.Plasmas, 2004, 11, 1333; • Vörös et al., J. Geophys. Res., 2004, 109, A11215; • Leubner & Vörös, Astrophys. J., 2005, 618, 547; • Leubner & Vörös,, Nonlin.Proc.Geophys., 2005, 12, 171; • Vörös et al., in. Multiscale Coupling of Sun-Earth Processes, (Ed. Lui, Kamide, Consolini), 2005, 29; • Vörös et al., Nonlin.Proc.Geophys., 2005, 12, 725; • Vörös et al., J. Geophys. Res., 2006, 111, A02102; • Vörös et al., Space Sci. Rev., 2006, 122, 301;

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