A quantitative study on evolution of solar active regions
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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
A Quantitative Study on Evolution of Solar Active Regions

Guo Juan & Zhang Hongqi

Huairou Solar Observing Station,

National Astronomical Observatories, CAS


Outline
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)


Quantitative study on evolution of magnetic field of ars
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)


1 total flux
(1) Total flux

  • Fa = |Fn|+|Fs|

  • Fa ~ describes the total flux of an AR


2 tilt
(2) Tilt

  • tilt = arctan (δy /δx )

  • tilt ~ one of the measurable characteristics of solar ARs that gives us information about subsurface physical processes


The definition of tilt in the 23 rd solar cycle
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


3 structural parameter
(3) Structural parameter

  • Hu = (Rs+Rn)/Rsn

  • Hu ~ describes the degree of isolation or mutual penetration of two polarities of an AR


A quantitative study on evolution of solar active regions

well separated bipolar:

Hu = (Rn+Rs)/Rns

= 0.6585

Rs

(Xn,Yn)

Rns

(Xs,Ys)

Rn


A quantitative study on evolution of solar active regions

highly packed bipolar:

Hu = (Rn+Rs)/Rns

= 2.0969

Rs

(Xs,Ys)

Rns

(Xn,Yn)

Rn


Structural parameter continued
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.







Summary
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


Structural parameter and solar major activities
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.



Relationship between magnetic structural parameter and cmes
Relationship between magnetic structural parameter and CMEs index

  • 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%


Summary1
Summary index

  • 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.