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A Quantitative Study on Evolution of Solar Active Regions

A Quantitative Study on Evolution of Solar Active Regions. Guo Juan & Zhang Hongqi Huairou Solar Observing Station, National Astronomical Observatories, CAS. Outline. Quantitative study on evolution of magnetic field in solar active regions (ARs)

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A Quantitative Study on Evolution of Solar Active Regions

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  1. A Quantitative Study on Evolution of Solar Active Regions Guo Juan & Zhang Hongqi Huairou Solar Observing Station, National Astronomical Observatories, CAS

  2. Outline • Quantitative study on evolution of magnetic field in solar active regions (ARs) • Relationship between magnetic structural parameter of some flare-associated (CME-associated) ARs and flares (CMEs)

  3. Quantitative study on evolution of magnetic field of ARs • Three parameters are used: (1) Total flux (Fa) (2) Tilt angle (Tilt) (3) Structural parameter (Hu) (be measured from line-of-sight magnetograms)

  4. (1) Total flux • Fa = |Fn|+|Fs| • Fa ~ describes the total flux of an AR

  5. (2) Tilt • tilt = arctan (δy /δx ) • tilt ~ one of the measurable characteristics of solar ARs that gives us information about subsurface physical processes

  6. The definition of tilt in the 23rd solar cycle in the north hemisphere in the south hemisphere 90 －90 180 0 180 0 －90 90

  7. (3) Structural parameter • Hu = (Rs+Rn)/Rsn • Hu ~ describes the degree of isolation or mutual penetration of two polarities of an AR

  8. well separated bipolar: Hu = (Rn+Rs)/Rns = 0.6585 Rs (Xn,Yn) Rns (Xs,Ys) Rn

  9. highly packed bipolar: Hu = (Rn+Rs)/Rns = 2.0969 Rs (Xs,Ys) Rns (Xn,Yn) Rn

  10. Structural Parameter (continued) • Hu < 1: well seperated bipolar • Hu > 1: highly packed bipolar • The higher the value of Hu is, the higher the degree of the two polarities packed together. • The good correlation between Hu and the configuration of magnetic field suggests that we can describe the magnetic configuration of an AR quantitatively by Hu.

  11. A summary of three ARs

  12. AR10488

  13. AR10484

  14. AR 9026

  15. Comparison of three ARs

  16. Summary • Quantitative analysis shows characteristics of the magnetic configurations and their evolutions of ARs. Three selected ARs show distinguished properties. • When ARs are of the same type with Mount Wilson Magnetic Classification, Hu gives different values: NOAA 10488 mHu=1.23 NOAA 10484 mHu=2.18 NOAA 9026 mHu=1.40

  17. Structural parameter and solar major activities • Magnetic gradient could be a viable proxy to predict where a major activity might occur (Falconer et al., 2003, JGR; Wang, H. M. et al., 2005, ApJ, submitted). • Structural parameter (Hu) is of the similar meaning with the magnetic gradient in some sense: the nearer the two polarities the higher the Hu, the near the two polarities the higher the magnetic gradient. • We believe that there must be close relationship between Hu and the occurrence of solar major activities.

  18. Relationship between magnetic structural parameter and flare index

  19. Relationship between magnetic structural parameter and CMEs • 54 CMEs originated from 26 ARs: Hu<1: 21 CMEs 38.9% Hu>1: 33CMEs 61.1% • 24 fastest CMEs( >1000 m/s)： Hu<1: 4CMEs 16.7% Hu>1: 20CMEs 83.3%

  20. Summary • There is close relationship between structural parameter and the occurrence of major activities. • Structural parameter may be a good proxy to predict whether an AR is likely to be major activities productive.

  21. Thanks a lot!

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