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Summary-2 (?)

Summary-2 (?). Takashi Sakurai National Astronomical Observatory of Japan. Two Summaries: Two Basic Problems in Solar MHD. Parker’s Hypothesis  coronal heating (nanoflare theory) Aly&Sturrock’s Hypothesis  CME. Parker Problem and Parker’s Hypothesis. hypothesis uniform initial field

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Summary-2 (?)

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  1. Summary-2 (?) Takashi Sakurai National Astronomical Observatory of Japan

  2. Two Summaries:Two Basic Problems in Solar MHD • Parker’s Hypothesis  coronal heating (nanoflare theory) • Aly&Sturrock’s Hypothesis CME

  3. Parker Problem and Parker’s Hypothesis • hypothesis • uniform initial field • regular boundary motion (but not preserving winding pattern) • creates discontinuity • leads to dissipation (by reconnection)

  4. Parker: ApJ 174, 499, 1972

  5. Parker: ApJ 264, 635, 1983

  6. Parker: Solar Phys. 121, 271, 1989

  7. Ideal MHD

  8. Parker: ApJ 407, 342, 1993 discontinuous field regular motion

  9. magnetic null and singular mapping dipping field lines and singular mapping

  10. Mikic, Schnack, and van Hoven: ApJ 338, 1148, 1989

  11. Discontinuity is not created. See alsoGalsgaard and Nordlund, JGR 1996Craig and Sneid, Solar Phys., in press

  12. real life (with finite resistivity) • uniform field, regular boundary motion • nulls created by diffusion • singular mapping of field lines • shear layer is created • dissipation by reconnection

  13. Dennis: Solar Phys. 100, 465, 1985

  14. Shimizu, PASJ 47, 251-263, 1995

  15. N(E) limited by micro physics small scale eventsslope< −2 ?new physics “flare” populationslope ~ −1.5 limited by finite size of the sun E 1026 erg 1032 erg

  16. Aschwanden: Solar Phys. 190, 223, 1999 Arbitrarily small flare loops cannot exist.

  17. What is “new physics?” • purely coronal events? no conduction loss • new regime of reconnection? • new component of magnetic field? • new component of driving motion? • ???? • forget this and go to waves?

  18. Aly&Sturrock’s Hypothesis • closed field lines (loops)+footpoint motion • energy increases and asymptotically approaches an upper limit • the upper limit is attained by the open field • the energy of the closed field can never exceed the open field energy • hence eruption to the open field is impossible

  19. Exceptions • two interacting flux tubes (Choe and Cheng 2002) • configuration with a detached flux tube (a filament) (Li and Hu 2003)

  20. Choe and Cheng: ApJ, 574, L179, 2002

  21. I wonder if the existence of a field-free volume separating the two flux tubes is essential. Can more general conditions be formulated to obtain E>Eopen?

  22. Li and Hu: Chinese J. Astron. Astrophys. 3, 555, 2003 Field with floating flux rope has energy exceeding the open field energy. In this case the excess is 1.5% of open field, 2.4% of closed dipole field energy.

  23. Y.Q.Hu: ApJ 607, 1032, 2004 octapole field central arcade opens, asymptotically approaching partially open field

  24. Y.Z.Zhang et al.: ApJ 626, 1096, 2005 With floating flux rope, the open field energy is exceeded

  25. Three Major Problems in Solar Physics • flares and CMEs • Solar-B launch in activity minimum,,, • high resolution, trigger mechanism • heating of the atmosphere (and solar-wind acceleration) • waves or superposition of small explosions? • the main target of Solar-B • carefully-designed observing plans (not trivial) • magnetic field generation (dynamo) • important hints (diffusion, surface dynamo,,,)

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