using helioseismology to probe magnetic structures (some selected topics)

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using helioseismology to probe magnetic
structures(some selected topics)
Doug Braun NWRA / CoRA

• NorthWest Research Associates
• Colorado Research Associates Division

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Barry J. LaBonte
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local helioseismology

• Hankel analysis
• ring diagrams
• time-distance
• helioseismic holography
• direct modeling

Gizon Birch Local Helioseismology 2005
Living Reviews in Solar Physics
livingreviews.org
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selected topics

• far-side imaging of ARs
• emerging ARS
• flows on AR-scales
• seismic models of sunspots

whats not here

• excitation of waves by flares
• magnetic (e.g. tachocline) influences on global
  modes
• lots of other things

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I. far-side imaging
http//soi.stanford.edu/data/farside
2-skip 1,3-skip implementation with MDI K.
Osland and P. Scherrer
Lindsey Braun 2000, Science 287, 1799 Braun
Lindsey 2001, ApJ, 560, L189
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far-side imaging with GONG
http//gong.nso.edu/data/farside
see poster González Hernández, et al.
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II. (search for) subsurface emergence of magnetic
flux

• Braun, D. 1995, PASP Conf. Series (GONG 94), 96,
  250
• Chang, H.-K., et al. 1999, ApJ, 526, L53
• Kosovichev, A., et al. 2000, Sol Phys, 192, 159
• Jensen, et al. 2001, ApJ, 553, L193
• Kosovichev, A. Duvall, T. 2002, BAAS, 34, 791

• results range from null, irreproducible (my own),
  to interesting and worth a second look
• none probe very deep, in the range where
  prediction might be practical (?)
• even without predictive capability, this pursuit
  is scientifically important

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rising flux tube properties
thin flux tube calculations (Fan Gong 2000)

• two days before emergence
• depth z 60 Mm
• speed vr 150 m/s
• let diameter fz (f 1 !)
• travel-time perturbation

time
s

• rms of single corr. 10 s
• can get N100 correlations (maybe) error of
  mean 1s
• direct detection of vr (probably) unlikely, but?

va
vr (rise speed)
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(No Transcript)
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III. flows on AR scales (SEE H8)
ARs as divergent or convergent flows (e.g. Braun
et al. 2004)
depth variation shallow inflows and deeper
outflows (e.g. Haber et al. 2004)
vertical vortiticy, kinetic helicity, other
indices (e.g. Komm et al. 2005, SEE POSTER 22)
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AR flows with time AR9906

• flows not (simply) related to morphology changes
• complicated vorticity signatures

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sunspots as
absorbers
Braun, Duvall LaBonte 1987, ApJ, 319, L27
1988, ApJ, 335, 1015
refractors
Abdelatif, Lites Thomas 1987, ApJ,
311, 1015Abdelatif Thomas 1987, ApJ, 320, 884
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IV. seismic models of sunspots

• models (forward inverse) of sound-speed
  variations
• e.g. Fan, et al. 1995 Kosovichev 1996 Chen et
  al. 1998 Kosovichev, et al. 2000 Zhao
  Kosovichev 2003 Basu, et al. 2004 Couvidat et
  al. 2004, 2005 Hughes, et al. 2005
• models of flows
• e.g. Duvall, et al. 1996 Kosovichev 1996 Gizon
  et al. 2000 Zhao et al. 2001 Zhao Kosovichev
  2003
• models of (other) magnetic effects complex
  sound-speed, anisotropy, mode conversion,
  absorption, upper turning point depressions, etc.
• e.g. Chen, et al. 1997 Ryutova Scherrer 1998
  Cally, et al. 2004 Crouch, et al. 2005 Lindsey
  Braun 2005

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sunspot seismology issues

• keeping in mind that all models are useful and
  important
• models with similar assumptions (e.g only
  sound-speed perturbations) often differ
  substantially
• including realistic magnetic fields in stratified
  model is very difficult
• no current model is consistent with (i.e.
  predicts) all observations or known wave
  interactions in sunspots

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1 vs 2-skip puzzle Does t- t t2 ?
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t- incoming travel-time (center-annulus or
ingression-control) t2/2 (half the) double-skip
travel-time (annulus-annulus or
egression-ingression) t outgoing
travel-time (center-annulus or egression-control)

• Braun (1997)
• No (for D gt 150Mm )
• Zhao Kosovichev (2006)
• Yes (for D 24 73 Mm )
• Braun (2006)
• No (for D 35 110 Mm )

?
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absorption mode conversion?
slow modes Spruit Bogdan Cally Bogdan (1997)
Holography normalized egression power
Hankel analysis phase shifts absorption
Crouch, et al. (2005) SEE POSTER 17
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Schunker, Braun, Cally, Lindsey 2005 Local
Helioseismology of Inclined Magnetic Fields and
the Showerglass Effect, ApJ 621, L149
Goal look for evidence of the conversion of
vertically oscillating p-modes to elliptical
motion in inclined fields in sunspot
penumbrae. Observations MDI (SOHO) -
helioseismic IVM (Mees
Obs.) Stokes Method measure correlation
between ingression and direct velocity signal at
different projected l.o.s angles (qp) in plane of
magnetic field.
AR 9026
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evidence for elliptical motion (mode conversion)
phase
modulus

• varies with field strength/inclination
• observed throughout 3-5mHz frequency range
• measured in several spots
• observed in TD measurements (Zhao Kosovichev
  2006)
• not predicted for, or observed in, scalar
  quantities (e.g. intensity)

inner penumbra
middle penumbra
outer penumbra.
?p
projected line-of-sight angle (from vertical)
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challenges

• farside
• how can we calibrate it?
• how can we improve it?
• emerging ARs
• can we detect direct or indirect effects (e.g.
  horizontal flows)?
• can theories simulations tell us what to look
  for?
• flows
• how do we combine surface (Doppler,
  feature-tracking) and subsurface information?
• what spatial, temporal scales, products, indices
  are useful and help solve physical problems?
• sunspots
• how do we exploit all of the observations
  (1,2-skip, frequency variations, lines-of-sight
  angles, absorption, etc)
• how do we include explicit magnetic effects in
  forward (and inverse) models?
• how can MHD simulations help?

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further information
http//cora.nwra.com/dbraun
support
NASA (LWS and SRT programs) NSF (Stellar
Astronomy and Astrophysics program)