Transcript HMIHill.ppt

Some Thoughts on HMI Data
Products & Processing
F. Hill
Jan. 27, 2005
A personal view
Developed over last 2 days during
sessions, lunches, chats, etc.
 Synthesis of conversations with several
attendees.
 NSO/GONG has experience in several
areas of helioseismology but they will not
be evenly covered here.
 Will mainly focus on rings, but not
exclusively.
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Just about every helioseismic
processing step needs work!
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Magnetic effects on spectral
line characteristics
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Vary with ρ?
Recent work of de Forest
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Rings, peaks, ridges, etc.
V & I?
Leaks
Background & asymmetry
Inversions
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Large set of choices, all bad
Adaptive strategy?
Abandon altogether?
Interpolation
Fitting
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Remapping, projections,
tracking
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Shape changes
Phase changes
Travel times
Non-simultaneous λ sampling
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Which for rings? 1D, 2D, 3D,
RLS, OLA?
Better error estimates –
correlated
Depth-dependent trade-off
parameter
Display
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Q(x,y,z,t)
VRML
Where’s the new science?
HMI is first helioseismology + vector
magnetograph combination.
 Subsurface flows and magnetic field
geometry unexplored.
 GONG + SOLIS provide good test bed.
 Want continual synoptic flow maps and
vector B maps
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More new science
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HMI resolution will allow study of subsurface
flows closer to poles than before.
New highly-detailed flow maps will challenge
AFD & dynamo theory.
Ultimate goals of activity prediction and nowcasting.
Want on-demand custom tracking origin and
extent.
VSO integration will leverage SDO return.
An idea from the half-bakery
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Create the “Best” flow map by combining results
from different techniques (global, rings, TD,
holography).
Construct a “point spread function” proxy (PSFP)
for each analysis.
PSFP is function of x, y, z, t, Δx, Δy, Δz, Δt.
“Deconvolve” PSFP from data – it’s the same sun.
Blind deconvolution assumes no a-priori
knowledge.
Average results with some weights.
Develop using rings
Same analysis method, but different
horizontal resolution as function of depth.
 Use 3-D resolution kernels as first guess
to PSFP.
 Specter of mode beating may rise again
for small-area short-time span patches.
 Need resolution kernels as standard data
product.
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Another semi-pastry
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Return of full raw data enables 4-D power
spectra of solar atmosphere.
λ is a proxy for height in the atmosphere.
P(kx,ky,kz,ω) allows estimate of slowness
surface, useful for MHD mode studies.
Major challenges:
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Calibration from λ to z (RT)
Only 5 or 6 z points (limits accuracy)
Non-simultaneous sampling in λ (Fourier shift
theorem)
Needed data products
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Synoptic maps of subsurface flow
Quick-look available 24 hours after acquisition
 Updated daily
 sf (surface focusing) and ar (active region)
products are OK as specified
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Synoptic maps of B with identical
specifications
 Resolution kernels
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Tentative Co-I Plans
Systematic projection comparison for rings
 Attempt to combine rings with different
resolutions
 Extend study of magnetic field effects on
observables
 Improve fitting and inversions
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Rasmus’ goal