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Analysis Methods for Magnetopause & Boundary Layer Studies

Analysis Methods for Magnetopause & Boundary Layer Studies. Hiroshi Hasegawa ISAS/JAXA In collaboration with B. U. Ö . Sonnerup & W.-L. Teh. Outline. Wavelet analysis (cascade in KH vortices) Reconstruction of 2D structures in a plasma fluid

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Analysis Methods for Magnetopause & Boundary Layer Studies

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  1. Analysis Methods for Magnetopause & Boundary Layer Studies Hiroshi Hasegawa ISAS/JAXA In collaboration with B. U. Ö. Sonnerup & W.-L. Teh

  2. Outline • Wavelet analysis (cascade in KH vortices) • Reconstruction of 2D structures in a plasma fluid 1. Grad-Shafranov (magneto-hydrostatic) reconstruction of magnetic field lines 2. Grad-Shafranov-like reconstruction of streamlines 3. MHD reconstruction (ideal & resistive) 4. Hall-MHD reconstruction

  3. Wavelet analysis can be used to revealto what extent the KH instability grows Roles of Kelvin-Helmholtz instability • Momentum and/or mass transport (Miura, 1984; Fujimoto & Terasawa, 1994) • Generation of ULF waves that may accelerate radiation belt electrons (e.g., Elkington, 2006) • Generation of vortical auroral forms via M-I coupling (e.g., Lui et al., 1989)

  4. (Inverse-) cascade Nakamura et al., 2004 Matsumoto & Hoshino, 2004 Miura, PoP, 1997

  5. Cluster event on 20 Nov 2001 (19 LT)(Hasegawa et al., 2004; Chaston et al., 2007; Foullon et al., 2008) C1 ion C1 electron density temperature velocity magnetic field

  6. Total-P perturbation in the vortex streamline Force balance • Dominant-mode period ~200 s: Wavelength ~6 Re. • Power also at ~400 s: Beginning of vortex pairing?

  7. Outline • Wavelet analysis (cascade in vortices) • Reconstruction of 2D structures in a plasma fluid 1. Grad-Shafranov (magneto-hydrostatic) reconstruction of magnetic field lines 2. Grad-Shafranov-like reconstruction of streamlines 3. MHD reconstruction (ideal & resistive) 4. Hall-MHD reconstruction

  8. Time series data to 2D image Flux Transfer Event 2D map of an FTE

  9. Reconstruction frame A 2D structure Reconstruction plane Y Integration as a spatial initial value problem Y VST_X X X VST(VHT) (in the x-z plane) Lx = VST_X* T (analyzed interval) X axis: SC trajectory in the x-y plane Z (invariant axis)

  10. × × 1. Grad-Shafranov (GS) reconstruction Assumptions: magneto-hydrostatic (time-independent) structures 2-D (no spatial gradient in z direction) Grad-Shafranov (GS) equation(e.g., Sturrock, 1994) B & p recovered (Hau & Sonnerup, 1999) Hasegawa et al., 2006

  11. 2. GS-like reconstruction of streamlines Assumptions: MHD, 2D, time-independent, & B along z axis GS-like equation for the stream function y V, n, & T recovered (Sonnerup et al., 2006) Hasegawa et al., 2007

  12. Vortex structurefrom GS-like reconstruction of streamlines C1 Dominant-mode wavelength ~6 Re C3 • Two vortices within one dominant-mode wavelength. Breakup of a parent MHD-scale vortex (cascade)?

  13. 3. MHD reconstruction (ideal) Assumptions: MHD, 2D, time-independent perp. to invariant axis isentropic flow All MHD parameters recovered, e.g., in the X-line rest frame (Sonnerup & Teh, 2008)

  14. MHD reconstruction of an FTE Seen by THEMIS-A on the MP surface wave sheath side Streamline LLBL side Field line Eriksson et al., 2009

  15. 4. Hall-MHD reconstruction (ideal) Assumptions: Hall-MHD, 2D, time-independent perp. to invariant axis isentropic flow All MHD parameters, E,& electron velocity recovered Sonnerup & Teh, 2009

  16. Benchmarking (Sonnerup & Teh, in press, 2009)

  17. What could be analyzed? • Behavior of coalescence/breakup (inverse-cascade/cascade) of KH vortices • Structural properties (shape, size/width/amplitude, & orientation) of FTEs, KH waves/vortices, magnetic islands in/around the vortices, reconnection jets, & ion diffusion regions. • Reconnection rate/electric field. Drawback… • The reality may rarely be 2D & d/dt~0.

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