Time-Distance Helioseismology at Multiple Heights in the Solar Atmosphere

Presented at the Institute for Astronomy as part of the 2nd year research talks in Spring 2015

Transcript

1. Time-Distance Helioseismology at Multiple Heights in the Solar Atmosphere Samuel Grunblatt
2. why should you care?
3. Highest SNR astrophysical lab for wave physics Wave propagation in a complicated environment: high T, high P, gravity and magnetic fields
4. Future space mission: SAFARI Velli et al. (2011)
5. Other missions: Seismology of Jupiter Gaulme et al. (2011)
6. Outline Part I: Background Relevant physics History of seismology Part II: Observations Motivation Instrument setup Pipeline development Part III: Methods & Results Atmospheric travel times Disk-annulus travel times Part IV: Discussion and Summary
7. Convection drives acoustic wave creation Duvall et al. (1997)
8. History of Helioseismology Plaskett (1916): observed fluctuations in solar surface Doppler velocity Hart (1954): fluctuation of solar origin Leighton (1962): periodic, 3 mHz oscillations, convective motions on supergranule scale Claverie (1979): modal structure of oscillations integrated over solar disk: global oscillation.
9. Global Helioseismology
10. Local Helioseismology Jensen et al. (2001)
11. Time-Distance Helioseismology Duvall et al. (1997) Zhao (2004)
12. Advantage of multiple, simultaneous measurements
13. Outline Part I: Background Relevant physics History of seismology Part II: Observations Motivation Instrument setup Pipeline development Part III: Methods & Results Atmospheric travel times Disk-annulus travel times Part IV: Discussion and Summary
14. Why is this important? Jefferies et al. (2006)
15. Observations 512x512 pixel images Pixel scale: 5’’/pixel 10s cadence 17 hour data string Wavelengths of interest: K - 769.9 nm Na I D2 - 589.0 nm
16. Instrument Tomczyk et al. (1995)
17. Magneto-Optical Filter Tomczyk et al. (1995)
18. Doppler velocity determination Christensen-Dalsgaard (2001)
19. Doppler images Created pipeline to align, reduce, and analyze 2014 images Potassium Doppler image
20. Outline Part I: Background Relevant physics History of seismology Part II: Observations Motivation Instrument setup Pipeline development Part III: Methods & Results Atmospheric travel times Disk-annulus travel times Part IV: Discussion and Summary
21. Methods 2 types of travel time measurements: Atmospheric and subsurface (disk-annulus)
22. Atmospheric signal analysis Identify 2x2 pixel region (map) Sodium Potassium
23. Atmospheric signal analysis Cross-correlate sodium, potassium signals Filter for frequencies of interest (3 or 7 mHz: either side of νac) Na/K Cross-correlation signal
24. Fit model to data y(t) = A2 ! p 8⇡ exp " !2(t Tg)2 8 # cos[!(t Tp)] Gabor wavelet equation: A: amplitude ω: 2πν, ν=freq. δω: 2πδν Tg: group time of wave Tp: phase time of wave Least squares fit to data:
25. Atmospheric mapping 3 mHz: little atmospheric propagation, except in mag. regions 7 mHz: atmospheric propagation suppressed by β = 1 surface causing mode conversion, reflection (magnetogram for reference)
26. Results: Atmospheric mapping Finsterle et al. (2004)
27. Disk-annulus mapping Important Variables: Disk-annulus thickness, radius
28. Disk-Annulus maps Resultant signal is polluted by surface gravity waves Some spatial similarities apparent: signals have similar structure, but must be further refined
29. Discussion Zhao (2004)
30. Application to future projects **Potential dispersion relation as a func. of field inclination angle Use 2014 data: higher resolution Incorporate MDI, Ca and He data for better correction SAFARI, giant planet seis.
31. Summary Successfully measured atmospheric TTs at necessary precision Need more sophisticated filter to get subsurface TTs Implication for understanding active regions, HMI, SAFARI