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Solar structure as seen by high-degree modes

Solar structure as seen by high-degree modes. M. Cristina Rabello Soares UFMG, Brazil and collaborators. Local Helioseismology Nearby Active Region. In collaboration with Rick Bogart & Phil Scherrer (Stanford University). Rabello-Soares , Bogart & Scherrer (2013 ):

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Solar structure as seen by high-degree modes

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  1. Solar structure as seen by high-degree modes M. Cristina RabelloSoares UFMG, Brazil and collaborators

  2. Local Helioseismology Nearby Active Region In collaboration with Rick Bogart & Phil Scherrer (Stanford University)

  3. Rabello-Soares, Bogart & Scherrer (2013): • Comparison of a quiet tile with a nearby active region (5oto 8o away) with a quiet tile with no nearby active region at the same disk position (same latitude and Stunyhurst longitude) • using HMI 5o patches from June 2010 to January 2012. • The HMI ring-digram analysis pipeline uses two fitting methods: rdfitc (Basu & Antia 1999) and rdfitf (Haber et al. 2000, which is also used by GONG pipeline). Looking at the magnetic field from a distance… The elephant in the room

  4. Flow variation Ux and Uy: zonal and meridional flows  U⁄⁄andUperpin relation to the direction of the nearby AR location

  5. Flow variation in the direction of the nearby active region Control set in black: + fitsc * fitsf

  6. Quiet region in the vicinity of AR (50 to 80 away) fitsf(in red) fitsc(in black) inflow outflow • Best trade-off parameter: • = 0.0050 • Small errors  error of the mean of fitted flows. • Negative flow means flow away from the nearby AR and • Positive towards the nearby AR.

  7. Quiet region in the vicinity of AR (50 to 80 away) fitsf(in red) fitsc(in black) inflow outflow • Surface cooling within the plage results in a downdraft which draws fluid in at the surface(Hindman, Haber & Toomre, 2009):Figure 11. Schematic diagram (side view)

  8. QnearbyAR- Q * fitsf fitsc Fsurf (x 103) * n = 1 * n = 2 * n = 3 • Quiet: MAI < 5 G • Active Region (AR): MAI > 100 G AR - Q In (AR-Q), only a few error bars for fitsc are shown. Fsurf (x 103)

  9. Conclusions • We observe an outflow from about 3 Mm until 6 Mm deep in quiet regions which are 50 to 80 from an active region and some indication of an inflow 0-2 Mm deep. • There is a surface term when comparing a quiet region with a nearby active region and a quiet tile (with no nearby AR). • The two fitting methods give different slopes for Fsurf which is mainly a function of frequency. • This surface term is similar, but present some differences with the surface term for AR – Q.

  10. Global modesSpherical Harmonic Decomposition

  11. Solar Cycle Variations

  12. Frequency shift as a function of solar activity (20 < l < 900) Figure 1 of Rabello-Soares (2011) • Medium-l: MDI Structure Program – Schou (1999) and Larson & Schou (2009) • High-l: MDI Dynamics Program – Rabello-Soares, Korzennik & Schou (2008) • Solar-radio 10.7-cm daily flux (NGDC/NOAA)

  13. Global helioseismology: variation between solar max and minimum Fig. 9 of Rabello-Soares (2012) Two-layer structure Baldner, Bogart & Basu (2012): analysed 264 regions (from 1996 to 2008) and applied Principal Component Analysis. Baldner, Bogart & Basu(2012)

  14. Comparison with solar model

  15. Data used: n > 0 • MDI Dynamics 2001 • Two different peak-fitting algorithms were used to fit the power spectra and obtain the mode frequencies: • Medium-l modes: known as the MDI peak-fitting method, is described in detail by Schou (1992) and improved in Larson & Schou (2008, 2009). • High-l modes: At high degrees, the spatial leaks lie closer in frequency, resulting in the overlap of the target mode with the spatial leaks that merge individual peaks into ridges, making it more difficult to estimate unbiased mode frequencies (also at large frequencies): Korzennik et al. (2013).

  16. The spatial leaks merge individual peaks into ridges Medium l Medium l, but high frequency High l Figure 1 of Rabello-Soares, Korzennik & Schou (2001)

  17. Instrumental effects affect the amplitude of the leaks Observed power spectra Simulated power spectra where the leakage matrix was calculated without and with a plate scale error of -0.1% Figure 7 of Rabello-Soares, Korzennik & Schou (2001)

  18. MDI (2001) - model S To suppress the uncertainties in the surface layers in helioseismic models, a "surface term" developed by Brodsky & Vorontsov (1993) using a higher-order asymptotic theory suitable for high-degree mode frequencies is used:

  19. L = 8 Fsurf(observed) – Fsurf(fitted) x 103 n (mHz) n = Fsurf(observed) – Fsurf(fitted) x 103 l / n(mHz-1)

  20. observed error frequency (mHz) n (mHz)  Medium-l fitting High-l fitting observed error frequency (mHz) degree

  21. Errors for l>200 are divided by sqrt(10), to taken into account that we are fitting every 10th l. MOLA Technique

  22. Averaging Kernels 0.960 0.980 0.985 m = 5e-7, b = 10

  23. Figure 15 of Basu et al. (2009)

  24. Error correlation functionHowe & Thompson (1996) Figure 1 of Rabello-Soares, Basu & Christensen-Dalsgaard (1999): Error correlation at r1 = 0.5 Rsunfor sound speed based on a medium-l mode set.

  25. Conclusions • The sound speed inversion using Korzennik et al (2013) high-degree (l = 100-1000) mode frequencies agrees with (old) MDI medium-l results (from Basu et al. 2009). • Good averaging kernels until 0.985 R . • More work needs to be done: oscillation in the results are likely due to error correlation  invert for every l.

  26. Thank you.

  27. *Fsurf (AR - Q) . Fsurf(QnearbyAR- Q) x 15 Comparison Only fitsc Fsurf (x 103) * n = 1 * n = 2 * n = 3

  28. NSO 2013 Variation of the mode parameters with solar cycle • It is well known that amplitudes decrease while mode widths increase in the presence of magnetic fields (for example, Rajaguru, Basu, and Antia, 2001). • Rabello-Soares, Bogart, and Basu (2008) have reported that the relation between the change in width and mode amplitude was very nearly linear. Figure 4 of Rabello-Soares, Bogart & Basu (2008)

  29. NSO 2013 Relative amplitude variation between: Quiet region with a nearby AR and with no nearby AR. Active and quiet regions Fig.3 of Rabello-Soares, Bogart & Scherrer (2013): colors are n=0, n=1, n=2, n=3, n=4 in the direction of the nearby AR perpendicular to it • For frequencies larger than ≈4.2 mHz, the modes are amplified (acoustic halo) if there is an active region nearby with very little dependence on their propagation direction.

  30. fistc ic=0 ic=1 (transparent: black)

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