1 / 25

Techniques for Active Region Seismology Irene González Hernández National Solar Observatory, Tucson, AZ

Techniques for Active Region Seismology Irene González Hernández National Solar Observatory, Tucson, AZ. Overview Main local helioseismology techniques Time Distance (Duvall et al., 1993) Helioseimic Holography (Lindsey & Braun, 1990) Ring Diagrams (Hill, 1988)

keran
Télécharger la présentation

Techniques for Active Region Seismology Irene González Hernández National Solar Observatory, Tucson, AZ

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. Techniques for Active Region Seismology Irene González HernándezNational Solar Observatory, Tucson, AZ

  2. Overview • Main local helioseismology techniques • Time Distance (Duvall et al., 1993) • Helioseimic Holography (Lindsey & Braun, 1990) • Ring Diagrams (Hill, 1988) • Comparison between results from different techniques • Excluding active regions from helioseismic inferences • Summary and Ongoing work Contents

  3. Towards Seismology of Active Regions: Overview “The Spatial Distribution of p-Mode Absortion in Active Regions” Braun, D. C., LaBonte B. J. and Duval, T.L. Jr. 1990, ApJ, 354, 372 Seismic Imaging of Sunspots in the Far Side of the Sun Lindsey, C. and Braun D., 1990, Solar Physics, 126, 101 “Scattering of p-Modes by a Sunspot” Braun, D. C., Duvall, T.L. Jr., LaBonte, B.J., Jefferies, S.M., Harvey, J.W. and Pomerantz, M.A. 1992, ApJ, 391L, 113 Time-distance helioseismology Duvall et al., 1993, Nature, 362,430

  4. First seimic image of an active region using a local helioseismology technique (time-distance) Overview First seimic image of active regions in the far side of the Sun using a local helioseismology technique (helioseismic holography) Lindsey, C. and Braun, D. C. 2000, Science, 287, 1799 Duvall, T., D’Silva, S., Jefferies, S.M., Harvey, J.W. and Schou, 1996, Nature, 379, 235

  5. Sound speed variation (from the quiet Sun) below and active region. • Stanford helioseismology group (time-distance analysis) Overview "An image of the sound speed below a sunspot derived from dopplergrams observed with the Michelson Doppler Imager onboard the Solar and Heliospheric Observatory spacecraft using the technique of time-distance helioseismology. Three planes are shown, on top the intensity at the surface which shows the sunspot with the dark central umbra surrounded by the somewhat brighter, filamentary penumbra. The second plane is a vertical cut from the surface to a depth of 24000 km showing areas of faster sound speed as reddish colors and slower sound speed as bluish colors. The sound speed is affected both by the temperature of the gas and the magnetic field, which we know to be strong in the sunspot at the surface. The normal increase of sound speed with depth in the sun has been subtracted so that we are only looking at deviations from the average. The third plane (bottom) is a horizontal cut at a depth of 22000 km showing the horizontal variation of sound speed over a region of 150000x150000 km."

  6. Large scale flows around active regions. Time Distance Map of near-surface horizontal flows obtained for Carrington rotation 1949 using f-mode time-distance helioseismology. […] Local flows converge towards complexes of activity with an amplitude of 50 m/s. Gizon, L., Duvall, T.L., and Larsen, R.M. 2001, in IAU Symp. 203: Recent insights into the physics of the Sun and Heliosphere, 189.

  7. Flows in underneath a rotating active region. • Left, Background image showingthe vertical velocities andthe horizontal velocity field(arrows) obtained from theAugust 7 data atdepth intervals 0-3 (top)and 9-12 Mm (bottom);right, results for theAugust 8 data withthe same depth intervals. • The longestarrow is 0.5 kms-1 for both theupper and lower graphs.The contour lines representthe line-of-sight magnetic field • Zhao, J., and Kosovichev, A.G. 2003, ApJ, 551, 446 Time Distance

  8. Travel time depends on surface amplitudes, distance and phase-speed filter details. • Maps of changesin mean phase traveltimes over thesmall sunspot region for two distances Time Distance • “The cookie cutter experiment” • When applying the cookie cutter to real data the plume-like feature is seen only when including all data, or for large values of the trade-off parameter. • Korzennik, S.G. 2006, Proceedings of SOHO 18/GONG 2006/HELAS I,Beyond the spherical Sun (ESA SP-624), p.60 Rajaguru, S.P., Birch, A.C., Duvall, T.L., Jr., Thompson, M.J. and Zhao, J. 2006, ApJ,646, 543

  9. Ambient Acoustic Imaging • Chang, H.-K.,Chou, D.-Y.; Labonte, B. and the TON Team, 1997, Nature, 389, 825. • Chou, D.-Y., 2000, Solar Physics, 192, 241 Helioseismic Holography Constructed outgoing intensity map and phase-shift map at the surface and 10 Mm at 3mHz (left) and same at 5mHz (right)

  10. Helioseismic Holography Braun, D. C. and Lindsey, C. 2000, Solar Physics, 192, 307

  11. Helioseismic Holography • Imaging of Active Regions on the Far Side of the Sun 11 April 2001. Region 9393 was still at longitude 154 Latitude 17N. The region continued to evolve as it rotated across the far side of the Sun. 24 April 2001. Region 9393 at longitude 154 Latitude 17N. The region came back to the front-side of the Sun in late April. MDI farside website: http://soi.stanford.edu/data/farside

  12. Helioseismic Holography • Imaging of Active Regions on the Far Side of the Sun • Calibration • Statistical Analysis • Noise reduction • Automatic detection • Solar Cycle dependence • Revisiting the Green’s functions (Pérez Hernández) • Artificial Data (Hartlep, Zhao, Ilonidis) GONG farside website: http://gong.nso.edu/data/farside

  13. Helioseismic Holography • Solar cycle variation of the “seismic solar radius” González Hernández, I., Scherrer, P. and Hill, F. 2009, ApJ, Letters

  14. Frequency Dependence in the Observed Travel-Time Shifts in Sunspots • Travel-time shifts from the H07 code, averaged over a disk of 39Mm diameter centered on the sound-speed perturbation, for the shallow case (1Mm, left) and deep case (10Mm, right) for three frequency bandpass filters: 3mHz(red), 4mHz(green) and 5mHz(blue). Helioseismic Holography Birch, A.C., Braun, D.C.,Hanasoge, S.M., Cameron, R. 2009, Solar Physics, 254

  15. Synoptic maps of fluctuating flows for depth 7Mm and 14Mm for Carrington Rotation 1975. The magnetic field intensity and polarity are indicated by red and green in the underlaying synoptic magnetogram. Inflows at superficial layers, outflows at deeper depth Ring Diagrams Haber, D. A., Hindman, B. W., Toomre, J. and Thompson M. J., 2004, Solar Physics

  16. Inversions for the adiabatic index anomalies in active regions compared with two quiet regions. The black and red results show the comparison with each quiet region. Just below the surface, there is a negative anomaly in both, sound speed and adiabatic index. The magnitude of the anomaly increases with the MAI. Analysis of 28 AR. Bogart, R., Basu, S., Rabello-Soares, M.C., Antia, H.M. 2008, Solar Physics. Ring Diagrams

  17. Vertical vorticity derived fromGONG data after removingthe large-scale flow components.The dashed line indicatesthe zero contour; thedotted lines indicate 20%,40%, 60%, and 80%of the minimum andthe maximum of thecolor scale. The dotsindicate the depth-latitude grid Ring Diagrams Komm, R. et al. 2004 ApJ, 605, 554 The cyclonic nature of the flows (measured as kinetic helicity density) around active region AR 10486 illustrates the twisting of magnetic fields beneath the visible surface of the Sun (blue:positive, red:negative). The horizontal length of this shallow slice is about 90 times the depth range and a depth of 12 Mm is about the same as the diameter of the Earth.The flow data were derived from helioseismic ring-diagram analysis (NSO/GONG). GONG mug picture (courtesy of Rudi Komm)

  18. Flare prediction • Two-dimensional histogram of the fraction (in %) of active regions that produced during their disk passage at least (top left) a C-class flare, (top right) a C5-class flare, (center left) an M-class flare, (center right) an M5-class flare, (bottom left) an X-class flare, and (bottom right) an X5-class. The histogram values are indicated by color. White bins indicate no such flare activity. The number in each bin represents the number of regions. • Komm, R. and Hill, F. 2009, JGR, 114 Ring-diagram Analysis

  19. Synoptic maps of near-surfacefluctuating flows for CR1932 spanning 1998 January21- February 17. The fluctuatingflow field shown isthe component that remainsafter the mean meridionaland zonal flows havebeen subtracted. (a) Synopticmap obtained using ringanalyses with RLS inversion.(b) Synoptic map generatedusing time-distance analyses off-mode data without depthinversion. The time-distance measurementshave been averaged spatiallysuch that the twoanalysis schemes have thesame horizontal resolution of15°. The maps generatedwith the two techniquesare decidedly similar, possessingcommon inflow and outflowsites. Comparison between results from different techniques Hindman, B., Gizon, L. Duvall, T. L. Jr., Haber, D. and Toomre, J. ApJ, 2006, 653, 725

  20. Comparison between results from different techniques Comparison of two different helioseismic methods used to infer wave speed perturbations below AR 9787. The red curve shows the averaged ring-diagram results, the solid blue curve shows the time-distance result, after averaging over the same area used for ring-diagram analysis. Gizon, L., et al. 2009, Space Science Reviews, 144

  21. Frequency shifts • Sequence of images of the fractional frequency shift and coeval magnetograms. Each panel correspond to a different 1664-min duration of the 1996 MDI Dynamics Program. Excluding Active Regions Hindman, B., Haber, D., Toomre, J. and Bogart, R. 2000, Solar Physics Average frequency shifts of 189 dense-pack tiles (top panel) and coeval MAI (bottom panel) for three days during CR 2009. Work by Jain, K., Tripathy, S. and Hill, F.

  22. Solar Cycle variation of the frequencies Excluding Active Regions Courtesy of S. Tripathy

  23. Yearly averages of the meridional flow obtained by ring-diagram analysis of continuous GONG data at four different depths. The variation with the solar cycle clearly observed at the superficial layers is less pronounced at deeper layers. The extra circulation (bumps) is also clearly visible in the shallow layers. González Hernández, I., Howe, R., Komm, R. and Hill F. 2010, ApJ Letters, submitted Excluding Active Regions Left: Longitudinal averages of surface horizonal flows. Solid lines: before excluding active region areas, dashed lines: after excluding active regions. Right: Sketch of surface flows around active regions Gizon, L. 2004, Solar Physics, 224, 217

  24. Temporal variation of the meridional circulation residuals at a depth of 5.8 Mm (central panel). Positive velocities are directed towards the poles. A symmetrical plot averaging both hemispheres is shown in the bottom panel. The top panel shows the location and magnetic strength of the activity during the same period (calculated from MDI synoptic magnetograms) González Hernández, I., Howe, R., Komm R. and Hill, F. 2010, ApJ L. submitted. Excluding Active Regions

  25. Summary and Ongoing work • What have we learned from Active Region Seismology • Large scale flow pattern below active regions • Overall sound speed variation • Location of active regions in the far side of the Sun • Solar cycle variation in frequencies highly affected by local strong magnetic field. • Possibility of using dynamic parameters as predictors for solar flare eruptions and active region emergence. • Interpreting the results is very tricky (surface contamination!). • Modeling and artificial data analysis • Continuous, high quality data : MDI, GONG and the upcoming HMI

More Related