1. Time Distance Study of Isolated Sunspots
S. Zharkov, C.J. Nicholas,
M.J. Thompson
Nice LHS Workshop, September, 2006

2. Nice LHS Workshop, September, 2006
supporting SDO mission in UK and worldwide
Sheffield algorithms: local helioseismology: travel time maps and inversion
code written in ANSI C, open source
current level of implementation:
travel-time estimation
inversion
testing
Nice LHS Workshop, September, 2006

3. Nice LHS Workshop, September, 2006
Data
Using EGSO Sunspot Solar Feature catalogue we identified a number of isolated sunspots that had no other sunspots within 10 heliographic degrees radius.
Locating the available MDI level-2 data we have selected 6 sunspots comprising Active Regions
Using EGSO SFC and solarmonitor.org we track each region for several rotations
Nice LHS Workshop, September, 2006

4. Nice LHS Workshop, September, 2006
Time-Distance
level2 MDI tracked derotated data (full disk resolution)
level 1.8 full disk data – tracked and derotated using Postel azimuthal projection and Snodgrass formula for derotation
pre-processing
Instrument MTF, low- & high-pass filtering, phase-speed filtering, f-mode filter
center to annulus geometry
travel times measured by Gabor wavelet fitting
Fresnel zone sensitivity kernels (Jensen & Pijpers, 2003)
12 skip-distance inverted to 14 depths using Multi-Channel Deconvolution (Jensent et al, 1998)
Nice LHS Workshop, September, 2006

5. Inversion: Multichannel deconvolution
Nice LHS Workshop, September, 2006

6. Nice LHS Workshop, September, 2006
Depth cuts NOAA8038
Nice LHS Workshop, September, 2006

7. Nice LHS Workshop, September, 2006

8. Nice LHS Workshop, September, 2006
0.36 Mm
Nice LHS Workshop, September, 2006

9. Nice LHS Workshop, September, 2006
6.4 Mm
Nice LHS Workshop, September, 2006

10. 0-crossing thru max flux point
Nice LHS Workshop, September, 2006

11. Nice LHS Workshop, September, 2006
AR statistics
Nice LHS Workshop, September, 2006

12. Nice LHS Workshop, September, 2006
next: more data?
Nice LHS Workshop, September, 2006

13. Questions & conclusions
real?
must include noise statistics to derive more accurate and reliable sound-speed profile
need more detailed kernels - looking forward to HELAS kernel facility (filter dependent)
cookie cutter test
Nice LHS Workshop, September, 2006

14. Nice LHS Workshop, September, 2006
thank you
Nice LHS Workshop, September, 2006