Helioseismology. Bill Chaplin, School of Physics & Astronomy University of Birmingham, UK

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1 Helioseismology Bill Chaplin, School of Physics & Astronomy University of Birmingham, UK STFC Advanced Summer School, 2014 Sep 1 University of Dundee

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6 Seismology as a probe of the solar cycle Bill Chaplin, School of Physics & Astronomy University of Birmingham, UK STFC Advanced Summer School, 2014 Sep 1 University of Dundee

7 Four solar cycles with BiSON Chaplin & Basu, Space Science Reviews, 2014, in the press

8 Acoustic signatures of the solar cycle: where it all started SMM/ACRIM data Woodard & Noyes 1985, Nature; 1988, IAU123

9 Clear correlations with surface measures of activity Elsworth et al. 1990, Nature, 345, 322

10 Frequency dependence at low degree Elsworth et al. 1994, ApJ, 434, 801

11 Frequency and degree dependence of shifts Libbrecht & Woodard 1990, Nature, 345, 779

12 Sound waves generated at top of Convection Zone... Convection Zone Radiative Interior Acoustic source Photosphere

13 The Resonant Sun The Sun resonates like a musical instrument...

14 Standing acoustic wave patterns... Internal acoustic ray paths Surface displacement: spherical harmonics red waves give blue waves give

15 Project onto spherical harmonics l: number of nodal lines m: number of azimuthal nodal lines

16 GONG data Internal Solar Rotation

17 The Tachocline ( speed slope ) Located just beneath base of convection zone Key for dynamo action! Courtesy P. H. Scherrer, SOI Stanford

18 Resonance in simple 1-D pipes

19 Changes in Mode Properties... Magnetic fields can act as agents of change: Directly, by action of Lorentz force Indirectly by changing stratification

20 The Solar Activity Cycle

21 Effects of near-surface activity on modes Depends on spherical harmonic of mode (l, m) (1,0) (1,1) (2,0) (2,1) (2,2) (3,0)

22 Global Frequency Shifts in GONG data: as Function of Solar Latitude Spatial dependence correlates strongly with active regions Dependence of shifts on mode degree, l, and mode frequency, suggests near-surface effect Courtesy R. Howe

23 Latitude Variations in Global Mode Damping and Energy Mode Damping Inference on changes to convection, which excites and damps modes Energy (forcing/damping) Komm, Howe & Hill, 2002

24 Tachocline oscillations GONG and MDI data Above tachocline Beneath tachocline Howe et al. 2011, JPCS

25 Torsional oscillations of the whole convection zone Difference in successive 72-d rotation inversions of MDI data Migrating bands of flow penetrate interior! Courtesy S. Vorontsov and collaborators

26 Slow start to cycle 24 Near-surface flows: GONG, MDI, HMI Howe et al. (2013)

27 Dynamics: comparing solar minima MDI & GONG data: cycle 24 cycle 23 Antia & Basu (2010)

28 Sounding stellar activity cycles: Sun BiSON Sun-as-a-star data scaled 10.7-cm radio flux

29 Quasi-biennial variation After removal of 11-yr cycle signature Broomhall et al., 2012, ApJ, 420, 1405

30 Cycles 22, 23 and rise of 24 BiSON Sun-as-a-star data High-frequency modes Intermediate-frequency modes Low-frequency modes scaled 10.7-cm radio flux scaled ISN

31 Trajectories of acoustic waves in interior Upper turning point Lower turning point Courtesy J. Christensen-Dalsgaard

32 Trajectories of acoustic waves in interior Waves launched at steeper angle to radial direction penetrate more deeply!

33 Trajectories of acoustic waves in interior These more-deeply penetrating waves have longer horizontal wavelengths: bigger skip distance goes with longer h [smaller k h ]

34 Trajectories of acoustic waves in interior Longer h [smaller k h ] = lower degree, l So the lower the degree, the more deeply penetrating the mode; and the larger the associated mode inertia

35 Frequency dependence of shifts Mode inertia and mode mass E nl M 1 V ξ 2 dv M nl / M 1 2 M nl v 2 nl 1 2 E nl M v 2 nl

36 Frequency dependence of shifts Chaplin et al. 2001, MNRAS, 324, 910

37 Frequency dependence of shifts E( nl ) : inertia an l=0 mode would have at frequency nl Q nl E nl / E( nl ) Chaplin et al. 2001, MNRAS, 324, 910

38 Frequency dependence of shifts UTP for radial modes (model S )

39 Frequency dependence of shifts nl ( ( nl E nl ) nl nl )

40 Frequency dependence of shifts 1 nl [ E nl / E (3000)] 1 Chaplin et al. 2001, MNRAS, 324, 910

41 Frequency dependence of shifts What do we expect for? Change confined close to surface (but in the interior): = 0 Change confined to photosphere (within one pressure scale height): = 3

42 Frequency dependence of shifts 0 2 Chaplin et al. 2001, MNRAS, 324, 910

43 Cycles 22, 23 and rise of 24 BiSON Sun-as-a-star data High-frequency modes Intermediate-frequency modes Low-frequency modes scaled 10.7-cm radio flux scaled ISN

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45 CoRoT reveals a short activity cycle in HD49933 García et al., 2010, Science, 329, 1032

46 Kepler Asteroseismic Science Consortium (KASC)

47 KASC asteroseismic survey Seismology of 500+ solar-type stars M Chaplin et al., 2011, Science, 332, 213; 2014, ApJS

48 main sequence Sequence of 1M stars main sequence sub giant Increasing radius sub giant red giant Chaplin & Miglio ARAA, 2013, 51, 353

49 Convection zone depth From acoustic glitches Kepler example: solar-type dwarf Signal present in particular combinations of frequencies Mazumdar et al., 2014, ApJ

50 Surface rotation periods Kepler lightcurves of solar-type stars

51 Asteroseismic inference on distribution of near-surface activity (1,0) (1,1) (2,0) (2,1) (2,2) (3,0)

52 Inference: surface distribution of activity sizes and phases of frequency shifts depend on (l, m) Sun-as-a-star data max=40 ± 10 degrees Chaplin et al. 2007, MNRAS, 377, 17 Chaplin (2011), Proceedings Tenerife Winter School

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