Holography

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Holography HMI
D. Braun, C. Lindsey, A. Birch
(NWRA/CoRA) collaborators P. Cally, A. Donea,
H. Schunker (Monash U.), J. Werne, M.
Woodard (NWRA/CoRA)

• NorthWest Research Associates, Inc.
• Colorado Research Associates Division

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HMI Science goals for holography

• farside imaging
• space weather prediction
• AR evolution
• flows
• physics of solar convection
• magnetic flux transport and emergence
• active regions
• structure and evolution of ARs
• flares
• physics of flares
• flare as point-source for local helioseismology

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helioseismic holography
H- ingression
H egression
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acoustic power holography
(space-time domain)
egression,ingression
(z depth,r horizontal position, ? surface
amplitude, G Greens functions)
egression,ingression power
sensitive to sources, sinks at focus
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Seismic images of a solar flare

• X2.6 1996 July 7 (AR 7978)
• propagating waves (Kosovichev Zharkova 1998,
  Nature, 393, 317)
• acoustic power holography to image source (Donea,
  Braun Lindsey 1999, ApJ, 513, L146)
• only acoustic flare signature until

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2003 Oct 28, X17 flare (AR 486)
A. Donea (Monash U.) C. Lindsey (NWRA)
100 Mm
1100 UT
instantaneous egression power between 5-7 mHz
computed in subjacent vantage with focus at
surface.
1110 UT
1125 UT
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phase-correlation holography
(space-frequency domain)
egression, ingression
correlation
correlation phase
travel-time perturbation
sensitive to refractive perturbations at focus
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farside imaging
Braun Lindsey (2001, ApJ, 560, L189)
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AR 486
first appeared on farside
2003 Oct 16
2003 Oct 3
2003 Nov 12
2003 Oct 30
ARs 486,488 on farside
http//soi.stanford.edu/data/farside
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phase-sensitive holography of flows
N
W
E
S
egressions and ingressions in 4 quadrants
e.g. E-W correlation phase
velocity
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1999 April 20, focus 3 Mm
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supergranulation and moat flows
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holographic flow kernels (A. Birch)
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supergranular depth sensitivity
div vh pupil
v ? e-z/zo cos(?z/z1) zo 2.5 Mm. red crosses
no return flow (z1 ??). green circles z1 5 Mm
black diamonds z1 15 Mm.
(Braun, Birch, Lindsey 2004 SOHO/GONG
Proceedings)
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horizontal divergence (smeared to 7.5)
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vertical vorticity (smeared to 7.5)
vort vh (1/cosB) ?( cosB vB ) / ?L
(1/cosB)?vL / ?B
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vorticity and rotation rate near ARs
N hemisph. S hemisph.

• slight association of ARs with positive vertical
  vorticity
• sunspots tend to occur near the boundaries of
  regions of opposite zonal shear
• excess rotation rate in ARs

(Braun, Birch, Lindsey 2004 SOHO/GONG
Proceedings)
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time and longitude-averaged flows
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probing the tachocline
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the showerglass effect
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showerglass assessmentlocal control correlations

• quiet Sun
• control (expect C 1)
• magnetic region
• C- describes how surface fields shift phase and
  amplitude of local photospheric signature of
  incoming waves
• C describes influence of field on outgoing waves

? local acoustic amplitude
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Lindsey C. Braun, D.C. 2005 The Acoustic
Showerglass I. Seismic Diagnostics of
Photoshperic Magnetic Fields, ApJ (in press)
-The Acoustic Showerglass II. Imaging Active
Region Subphotospheres, ApJ (in press)
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application of showerglass correction
?c lt 250 m/s
7.0 Mm
uncorrected corrected
focus 4.2 Mm
8.4 Mm
5.6 Mm
9.7 Mm
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application of showerglass correction to
horizonal-flow signatures
focus depth 3 Mm 5 Mm
7 Mm
no correction
showerglass corrected
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Schunker, Braun, Cally, Lindsey 2005 Local
Helioseismology of Inclined Magnetic Fields and
the Showerglass Effect, ApJL submitted
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HMI tasks for holography

• farside imaging
• upgrades, software rewrites
• investigate high-? egression power maps for
  near-limb ARs
• flows
• f-mode holography for near surface
• forward and inverse modeling
• adaption of farside codes to deep interior
• active regions
• understand showerglass effects (surface phase and
  amplitude distortions) for correcting subsurface
  signatures
• flares
• diagnostics of seismic flare emission (why
  relatively rare?)
• artificial data for testing local helioseismology