Sub-Surface Meridional Flow, Vorticity and the Life Time of Solar Active Regions

1. Sub-Surface Meridional Flow, Vorticity and the Life Time of Solar Active Regions Maurya, R., A., & Ambastha, A. 2010, arXiv1003.5273 April 19, 2010 short talk in Solar Seminar Tetsu Anan

2. Abstract 1/15 • Global Oscillation Network Group (GONG) • 74 Active regions (ARs) in August 2001 – January 2007 (Solar Cycle 23) • Meridional velocity profiles along the depth (range of 0 – 14 Mm) • Life time of ARs • the complexity of flow structures beneath the surface of ARs • Hemispheric trend • Magnetic Index • Flaring activity important inference

3. Introduction 2/15 • It has become possible to study sub-surface structures and flows to the advent Helioseismology, which probe the solar interior using acoustic modes of oscillations. • Sunspots rotation rate with depth depends on the stage of evolution and ages • Sonspots are the location of the large flows near the surface • Active regions (ARs) have sub-surface horizontal flows (averaged 0-16Mm) combined with cyclonic vorticity • Activity related in solar surface flows. • Maximum unsigned zonal and meridional vorticities of ARs are correlated with the total X-ray flare intencity • Steep meridional velocity gradients are found in flaring ARs at depth range of 4-5 Mm, which decreased after flares. Kosovichev et al. 2000; Haber et al. 2002; Komm et al. 2004; Mason et al. 2006; Ambastha et al.2004; ,,,,,,,,,,,

4. in this letter, 3/15 • 74 Active regions (ARs) of varying levels of flare activity and magnetic complexity in August 2001 – January 2007 (Solar Cycle 23) • Meridional velocity profiles along the depth (range of 0 – 14 Mm) • Life time of ARs • the complexity of flow structures beneath the surface of ARs • Hemispheric trend • Magnetic and flaring activity

5. The data - sample ARs - 4/15 • ARs producing flares of X-ray class > M1.0 using GOES database • Carrington rotations 1980-2052 of Solar Cycle 23 during August 2001 – January 2007 • Heriocentric location ±40° to avoid projection effect • use archived information “Solar Monitar” • 74 ARs http://www.solarmonitor.org/ Carrington rotations is a system for comparing locations on the Sun over period of time. Period is 27.2753 days. The system start from Nov. 9, 1853.

6. The data 5/15 • Global Oscillation Network Group (GONG) • The project acquires Doppler velocity images from a network of six identical instruments distributed around the world. • 16°(solar latitude)×16°(solar longitude)×1664min • Three-dimensional Fourier transform => [kx,ky,ω] • We can derived the flow beneath the surface • Increasing (decreasing) frequency depend on wave’s propagation along (opposite) flow. • The modes of different wavelengths are trapped at different depths.

7. NOAA 10030 Northern hemisphere NOAA 10480 Southern hemisphere Results & Discussions 6/15 Granulation scale Meridional vel. Grad d’uy (3×10-6 s-1) 100 0 -50 50 -50 -100 100 0 50 0 2 Mesogranulation scale 4 6 solid line Meridional velocoty , directed toward the equator (uy) dash dotted line meridional velocity gradient (du’y≡duy/dz) Depth z (Mm) 8 10 12 14 100 0 -50 50 -50 -100 100 50 0 Meridional vel. uy (m s-1) • There exist three sheared layers in the interior of these two ARs. => This appears to be a general feature of flare productive and complex ARs of our sample

8. NOAA 10030 Northern hemisphere NOAA 10480 Southern hemisphere Results & Discussions 7/15 Granulation scale Meridional vel. Grad d’uy (3×10-6 s-1) 100 0 -50 50 -50 -100 100 0 50 0 2 Mesogranulation scale 4 6 solid line Meridional velocoty , directed toward the equator (uy) dash dotted line meridional velocity gradient (du’y≡duy/dz) Depth z (Mm) 8 10 12 14 14 100 0 -50 50 -50 -100 100 50 0 Meridional vel. uy (m s-1) • 「extrema (　)  convective scale sizes」 • ∵ instabilities that drive the convective cells

9. Results & Discussions 8/15 • 74 samples • 44 ARs displayed two extrema  complex & flare productive depth = 1.92±0.15Mm、4.69±0.30Mm • 30 ARs displayed a single extrema  dormant depth = 1.66±0.97Mm

10. d’uy (3×10-6 s-1) 2 Results & Discussions 0 -50 -100 100 50 0 2 1 d’ uy = 1.05 - 0.19z 4 0 6 Max. meridional vel. Grad d’uy (10-5 s-1) Depth z (Mm) 8 -1 10 d’ uy = -1.15 + 0.21z 12 -2 14 2 3 4 5 1 Depth z (Mm) 0 -50 -100 100 50 uy (m s-1) • Distribution of the d’uy with depth • 74 samples • hemispheric trend • northern hemisphere => 24 out of the 34 ARs have negative maximum gradients • southern hemisphere => 29 out of the 39 ARs have positive maximum gradients • why the maximum d’uy should have a linear reration with depth? Depth range 1.5 – 6 Mm 9/15

11. Results & Discussions 10/15 d’ uy = 0.01 + 0.48MI d’ uy = -0.22 – 0.31MI • Distribution of the d’uy with MI • MI = 96 minutes averaged magnetograms obtained from SOHO/MDI, the area of interest correspond to the 16°×16° used in the ring anarysis • 74 samples • The maximum d’uy of ARs increased with MI

12. NOAA 10030 Northern hemisphere NOAA 10226 Southern hemisphere Results & Discussions 11/15 Granulation scale Mesogranulation scale • ωz varies with depth both in sign and magnitude • 0 vorticity may be a signature of the flux rope being broken at these depthes. • The disconnection mechanisms (Schüssler & Rempel 2005)

13. Disconnection mechanism 12/15 • After dynamically active imergence phase, magnetic flux at the solar surface soon ceases to show strong signs of the subsurface dynamics of its parent magnetic structure • The emerging flux initially evolves according to its internal large-scale dynamics • Sunspot is a shallow object, which breaks apart into a large number of flux tubes not far below the surface ∵local herioseismology • This behavior is in striking contrast to what would be expected if the emerging flux would follow the evolution of its magnetic roots (105G initial field at the bottom of the convection zone) ∴Bipolar magnetic regions somehow become disconnected from their roots within a few days after emergence.

14. 13/15 Results & Discussions 0 2 4 6 Depth z (Mm) 8 10 12 14 0 -4 -2 2 4 ωz (10-7 s-1) • Variation of the remaining life time with the depth of deepest zero vorticity. • ARs having zero vorticity at deeper levels last longer. • Zero Vorticity may be a signature of the flux rope being broken • exclude super-active regions (SARs) ∵long life time > 30daysNOAA10030,NOAA 10044,NOAA 10069,NOAA 10486,NOAA 10488

15. Results & Discussions 14/15 4 0 -4 -2 2 ωz (10-7 s-1) • Flare productivity vs. extrema of ωz • the depth of first extrema is mildly correlated with the integrated X-ray flux. (Pearson correlation coefficient 20%) • no correlation is found between the second extremum of ωz and with the integrated X-ray flux.

16. 15/15 conclusions

17. THANKS

18. The data - GONG -

19. Convective scale (Rast 2003; Nordlund et al. 2009)