1 / 29

A Test of the Ring-Diagram Fitting Formula

A Test of the Ring-Diagram Fitting Formula. A. Kosovichev. Verification, testing and investigation of systematic effects are crucial for the HMI success. Two approaches: Comparison with other local helioseismology methods Ring diagram analysis Acoustic holography/imaging

rumor
Download Presentation

A Test of the Ring-Diagram Fitting Formula

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. A Test of the Ring-Diagram Fitting Formula A. Kosovichev

  2. Verification, testing and investigation of systematic effects are crucial for the HMI success • Two approaches: • Comparison with other local helioseismology methods • Ring diagram analysis • Acoustic holography/imaging • Using numerical simulation data • Wave propagation linearized MHD codes • Local sunspot regions (K.Parchevsky) • Full-Sun sphere (T.Hartlep) • Non-linear radiative MHD codes • MSU code (R.Stein) • NASA/Ames code (A.Wray)

  3. Example: sound-speed structure below sunspots Travel-time inversions Born kernels Ray-path kernels Couvidat et al (2006)

  4. The controversies in data analysis procedures can be resolved by using numerical simulation data Example: phase-speed filtering is used for travel-time measurements at short travel distances to separate first- and second-bounce signals and improve S/N.

  5. Testing of acoustic holography technique with phase-speed filtering revealed travel-time artifacts at short distances (Birch et al 2009) Problematic positive shifts D=1 Mm (shallow) D=10 Mm (deep)

  6. Zhao et al (2009) repeated this test by using the standard time-distance technique with and without the phase-speed filtering and did not find such artifacts. They found a reasonably good agreement with the ray-theory predictions. Blind tests are being done for more complicated models.

  7. Comparison with ring-diagram inversions Basu et al (2004) Bogart et al (2008)

  8. Comparison of ring-diagram and time-distance inversions by Gizon et al (2009) using the same ring-diagram code but a different time-distance code

  9. Ring-diagram fitting formula (CT)(Basu, Antia, and Bogart, 2004)

  10. Test • Specify a sound-speed sunspot model. • Assume that this perturbation is spherically symmetric. • Calculate the frequency shifts by using the variational principle, and perturbed frequencies. • Fit to the frequencies of the standard solar model and the model with a sunspot-type perturbations • Calculate the frequency difference and run the structure inversion code (OLA), assuming 0.1% measurement error. • Compare inversions with the initial sunspot model.

  11. Frequency variations

  12. Sunspot model (T.Hartlep)

  13. CT ring fit True values

  14. Summary • Verification and testing of the local helioseismology techniques using numerical simulation data is critical for development of the HMI data analysis pipeline. • It is important to develop of methods and standards for intercomparison of the various local techniques. • The CT ring-diagram fitting formula used by Basu et al (2004), Bogart et al (2008) and Gizon et al. (2009) may lead to large systematic errors.

More Related