Summary-2 (?)
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Summary-2 (?)Summary-2 (?)
Takashi SakuraiTakashi SakuraiNational Astronomical Observatory of JapanNational Astronomical Observatory of Japan
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Two Summaries:
Two Basic Problems in Solar MHD
Parker’s Hypothesis coronal heating (nanoflare theory)
Aly&Sturrock’s Hypothesis CME
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Parker Problem and Parker’s Hypothesis
hypothesisuniform initial fieldregular boundary motion (but not preserving
winding pattern) creates discontinuity leads to dissipation (by reconnection)
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Parker: ApJ 174, 499, 1972
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Parker: ApJ 264, 635, 1983
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Parker: Solar Phys. 121, 271, 1989
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Ideal MHDmagnetic field
boundary motion
create discontinuity?
uniform singular yes
discontinuity regular yes
with nulls regular yes
dipping field lines
regular yes
uniform regular no
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Parker: ApJ 407, 342, 1993
discontinuous field
regular motion
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magnetic null and singular mapping
dipping field lines and singular mapping
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Mikic, Schnack, and van Hoven: ApJ 338, 1148, 1989
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Discontinuity is not created.
See alsoGalsgaard and Nordlund, JGR 1996Craig and Sneid, Solar Phys., in press
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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
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Dennis: Solar Phys. 100, 465, 1985
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Shimizu, PASJ 47, 251-263, 1995
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“flare” populationslope ~ −1.5
small scale eventsslope< −2 ?
new physics
N(E)
E
limited by micro physics
1032 erg1026 erg
limited by finite size of the sun
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Aschwanden: Solar Phys. 190, 223, 1999
Arbitrarily small flare loops cannot exist.
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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?
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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
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Energy
Energy ofopen field
Energy ofpotentialfield
S hear
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Exceptions
two interacting flux tubes (Choe and Cheng 2002)
configuration with a detached flux tube (a filament) (Li and Hu 2003)
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Choe and Cheng: ApJ, 574, L179, 2002
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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?
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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.
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Y.Q.Hu: ApJ 607, 1032, 2004
octapole field
central arcade opens, asymptotically approaching partially open field
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Y.Z.Zhang et al.: ApJ 626, 1096, 2005
With floating flux rope, the open field energy is exceeded
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Energy
Energy ofopen field
Energy ofpotentialfield
Shear
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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-Bcarefully-designed observing plans (not trivial)
magnetic field generation (dynamo) important hints (diffusion, surface dynamo,,,)