Sot observing modes for local helioseismology and data analysis
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SOT observing modes for local helioseismology and data analysis. Takashi Sekii NAOJ. SOT and local helioseismology. SOT provides high-resolution Dopplergrams and thus a great opportunity to study subsurface structure and flow (and a lot more) Spatial resolution 0.2”

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Sot and local helioseismology
SOT and local helioseismology analysis

  • SOT provides high-resolution Dopplergrams and thusa great opportunity to study subsurface structure and flow (and a lot more)

SOT17, Tokyo


High resolution powerspectrum
High resolution powerspectrum analysis

  • MDI high-resolution power spectrum

    • No resonant p modes above ℓ≈2000

    • The f-mode frequency ∝ sqrt(ℓ)

SOT17, Tokyo


High resolution t d diagram
High resolution t-d diagram analysis

  • Sekii et al 2001: MDI(left) versus La Palma SVST G-band (right, Berger et al 1998)

SOT17, Tokyo


How do we use sot for local helioseismology 1 2
How do we use SOT for local helioseismology? (1/2) analysis

  • Which line(s)?

    • Fe I 5576 (non-magnetic, photosphere)

      • Mg I 5173 (magnetic, chromosphere)

      • One of magnetic iron lines

  • Field of view

    • the full unvignetted field: 240”x160”

  • 2x2 summing:OK except (perhaps) at high latitudes

SOT17, Tokyo


How do we use sot for local helioseismology 2 2
How do we use SOT for local helioseismology? (2/2) analysis

  • Cadence

    • 1 min is the “standard”

      • But there is no reason a higher cadence should hurt, except in terms of telemetry

      • A higher cadence may be favoured in particular for chromospheric wave study

SOT17, Tokyo


Data amount aspect
Data amount aspect analysis

  • A 12-hr run of single-line observation, 320”x160” FOV, 2x2 summing, 1-min cadance, JPEG compression

    →~9 Gbits

SOT17, Tokyo


Data analysis 1 3
Data analysis (1/3) analysis

  • Time-distance analysis

  • Calibrated & tracked Dopplergrams

    • wavefield characterization, excitation study、surface flow etc

  • Filtered Dopplergrams (phasespeed filter, averaging on segments etc)

  • Cross-covariance function

  • Travel-time measurement

  • Inversion for subsurface structure & flow

SOT17, Tokyo


Data analysis 2 3
Data Analysis (2/3) analysis

  • Inversion: Ray approximation kernels for p-mode waves + MCD inversion

    • How shall we incorporate f-mode data?

    • More sophisticated/realistic methods?

    • It is still a developing subject

SOT17, Tokyo


Data analysis 3 3
Data analysis (3/3) analysis

  • Most of the scientific targets are achieved by the standard t-d analysis and its by-products

  • We may add

    • “Simultaneous” observations with SP

    • Multi-line observation for chromospheric waves

  • Observation with a photospheric magnetic line (see the next slide)

SOT17, Tokyo


The first thing we would like to do
The first thing we would like to do analysis

  • A joint observation with MDI

  • SOT field in the middle of MDI field

  • QT & AR

    • Calibration (Doppler measurement, plate scale)

    • Combined data provides better depth coverage

    • Insight for t-d analyses in AR, using both magnetic and non-magnetic lines

SOT17, Tokyo


Time distance analysis in ars
Time-distance analysis in ARs analysis

  • Doppler measurement based on FGs

    • MDI algorithm optimized for QT

    • Does not affect SOT directly, since SOT can use a non-magnetic line

    • Does affect MDI-SOT joint observation

  • Oscillations in AR

    • Scattering, changes in thermal structure, suppressed excitation

    • Richard Wachter’s talk

SOT17, Tokyo


Summary
Summary analysis

  • High-resolution local-helioseismology by SOT

  • Time-distance inversion at the centre of the analysis

SOT17, Tokyo


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