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H. Isobe, 2004/11/1, Taiyo zasshikai

“Transport of solar wind into Earth’s magnetosphere thorough rolled-up Kelvin-Helmholtz vortices” H. Hasegawa et al. 2004, Nature, 430, 755 “Helioseismic observation of the structure and dynamics of a rotating sunspot beneath the solar surface” J. Zhao & A. G. Kosovichev 2003, ApJ, 591, 446

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H. Isobe, 2004/11/1, Taiyo zasshikai

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  1. “Transport of solar wind into Earth’s magnetosphere thorough rolled-up Kelvin-Helmholtz vortices” H. Hasegawa et al. 2004, Nature, 430, 755 “Helioseismic observation of the structure and dynamics of a rotating sunspot beneath the solar surface” J. Zhao & A. G. Kosovichev 2003, ApJ, 591, 446 “Helioseimic observations of magnetohydrodynamics of the solar interior” A. Kosovichev in Magnetohydrodynamics of Stellar Interior Cambridge, Sep 6-17, 2004 H. Isobe, 2004/11/1, Taiyo zasshikai

  2. “Transport of solar wind into Earth’s magnetosphere thorough rolled-up Kelvin-Helmholtz vortices”H. Hasegawa, M. Fujimoto, T.-D. Phan, A. Balogh, M. W. Dumlop, C. Hashimoto, R. TanDokoro 2004, Nature, 430, 755

  3. The mechanism by which the solar wind enters Earth’s magnetosphere is unknown. • Reconnection at the low latitude magnetopause? • However, the plasma content in the outer magnetosphere increases during notrhward solar-wind magnetic field conditions, when reconnection is less efficient. • Alternative mechanism is associated with nonlinear phase of the Kelvin-Helmholtz instability. • Here they show the evidence of K-H instability in the in-situ observation.

  4. Cluster mission Multipoint in situ measurement by four Cluster spacecraft forming a tetrahedron. => Detection of the nonlinear stage of Kelvin-Helmholtz vortices.

  5. Ion energy spectrum Ion Tempera-ture by C1 Plasma density Position of the sattelites 20:42 20:26 magnetopause solar wind • C1 is inner than C3 and C4 • Red bar in the 3rd row indicate instances when C1 observed heigher density. C2? C1 C4 C3

  6. V B Synthesized B vector from 3D MHD simulation. Consistent with K-H origin vortices.

  7. Mixing of wind/magnetosphere plasma Black: satellite in the solar wind. Red: satellite in the magnetosphere. The double peaks of the red curve indicate the mixing of the solar-wind plasma (<2 keV) and the magnetospheric plasma (>5keV).

  8. Conclution • Evidence of nonlinear development of the Kelvin-Helmholtz instability by in situ observation of four Cluster satellites. • Also found is the mixing of solar wind and magnetospheric plasma in the K-H regiion. • Support the idea that the transport of the solar wind plasma into the magnetosphere is associated with nonlinear K-H. • Microscopic process for the plasma transportation is not clear. No signature of local reconnection.

  9. Helioseismic observation of the structure and dynamics of a rotating sunspot beneath the solar surfaceJ. Zhao & A. G. Kosovichev 2003, ApJ, 591, 446 • Time-dependent (local) helioseismology (data:MDI) • Evidence of sub-photospheric twist of rotating sunspots • Vortex motion

  10. NOAA 9114, 2000 Aug. 4-12 (SOHO/MDI) • The main sunspot rotates rapidly (200° in 3 days). • The rotation is clearly visible because of the protruding feature A. • Solid line: trace of smaller sunspot (indicated by red arrow). • The small sunspot moves arond the main spot and finally merges.

  11. Sound speed variation at the depth of 6Mm. • Sound speed variation δc/c relative to the quiet sun. Red is positive and blue is negative, raiges from -0.02 - 0.08. • Contour: line-of-sight magnetic field (600 - 1600 G) UT16:20, Aug. 7 UT12:39 Aug. 8 Protruding structure similar to A is also visible at z=6Mm, but forms an angle of 〜45°. Signature of subphotoshpheric twist?

  12. Flow field at z=0-3 (top) and 9-12 (bottom) Mm • Color: vertical velocity. • Red=0.5 km/s (downward), • Blue= -0.1〜0.2 km/s (upward) • Arrows: horizontal velocity. Largest arrow is 0.5 km/s. • In upper layer (0-3Mm), converging flows with downdraft. Mainly counterclockwise vortex. • In deeper layer (9-12 Mm), upward divergent flows. Clockwise vortex. Aug. 7 Aug. 8

  13. Kinetic helicity α≡v・(∇×v)/|v|2 • The vertical component of kinetic helicity, as a possible origin of magnetic twist, is calculated. • αz=-1〜-6×10-8 m-1 , which is the same order of magnetude as the typical current helicity (Pevtsov et al. 1995)

  14. Error estimate Monte Carlo simulation to estimate the error. Error is larger in vertical velocity near z=4-6Mm. Effect of umbra has been tested. Qualitatively OK. horizontal vertical

  15. Conclusion • More than 4Mm below the sunspot, the sound speed is larger than that in the quiet sun (Kosovchev et al. 2000, Sol. Phys.) • Distribution of the sound speed variation at z=6Mm shows similar shape of the sunspot at z=0. If the shape of sound speed variation reflect the local structure of flux tube, it is a signature of sub-photospheric twist. • Vortex motion below the spot.Kinetic helicity is the same order of magnitude as typical value of magnetic helicity.

  16. Helioseimic observations of magnetohydrodynamics of the solar interiorA. Kosovichev in Magnetohydrodynamics of Stellar Interior Cambridge, Sep 6-17, 2004 The viewgraphs (PPT, PDF etc.) of the conference can be downloaded at: http://www.newton.cam.ac.uk/programmes/MSI/ws.html

  17. Isaac Newton Institute for mathematical science • The proof of the Fermat’s last theorem was done here in 1993.

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