Helioseismic%20Holography%20 - PowerPoint PPT Presentation

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Helioseismic%20Holography%20

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Helioseismic Holography & some experiments on 'field effects' in CR1988 ... 3 x 3 mosaic covering 120 x 120 each tile: 40 x40 (cropped from 60 x60 box) ... – PowerPoint PPT presentation

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Title: Helioseismic%20Holography%20


1
Helioseismic Holography some experiments on
field effects in CR1988
D. Braun
  • NorthWest Research Associates
  • Colorado Research Associates Division

2
daily flow map
  • 1 day 27.3 hr
  • Sun rotates 15
  • Postel projections
  • 3 x 3 mosaic covering 120 x 120
  • each tile 40x40 (cropped from 60x60 box)
  • flow-sensitive holography in 3D Fourier domain in
    each box

3
depth sensitivity
  • what Im showing here
  • is not an inversion
  • is derived from E-W and N-S holographic phase
    signatures
  • calibrated from different tracking rates
  • represent a kind of average from surface down to
    focus depth
  • inversions will be discussed in H8

4
typical daily map (flows averaged over 15 boxes)
5
field effects
  • systematic (and spurious) flows associated with
    fixed spatial position on the disk
  • may result from
  • foreshortening
  • image distortions
  • projection deficiencies
  • Carrington element errors
  • spatially varying frequencies across the disk
  • etc.

6
assessing field effects
  • make field-effect map from all days
  • average of all daily maps without rotational
    shifting in longitude
  • a longitudinal mean is subtracted (i.e. it is
    assumed this is real e.g. meridional, ARs,
    but??)
  • spatially smeared (Gaussian FWHM 7.5)
  • assess Postel distortion for single day
  • compare 3x3 (40 spaced) and 15x15 Postel (8
    spaced) tiling
  • difference is a proxy of likely Postel
    distortions
  • lazy way of avoiding spherical geometry coding

7
field-effect maps
8
B and L components
9
variations with depth and instrument (B
component only)
MDI
depth 3Mm
7 Mm
14 Mm
30 Mm
GONG
note corner edge features more pronounced in
northern hemisphere
10
3x3 and 15x15 tiling comparison(B component only)
depth 3 Mm
11
comparing Postel distortion field effect maps
12
after Postel distortions are subtracted, whats
left in the field effect map?
13
a possible explanation
14
can we believe things like this?
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