Evolutionary Characteristics of Magnetic Helicity Injection through Active Regions

Hyewon Jeong, Jongchul Chae

Seoul National University

Purpose

How much helicity is supplied through active regions?

Does the helicity injection in an active region occurs intensively during a specific period or steadily through all of its lifetime?

Magnetic Helicity Magnetic helicity Sum of linking numbers over all pairs of closed field line

s in a given volume

xB dAH 3

v Pr xdPBAAH 3)()(

Relative magnetic helicityRelative magnetic helicity Magnetic helicity relative to the Magnetic helicity relative to the

helicity of potential field with the helicity of potential field with the same magnetic flux at the photosame magnetic flux at the photospheric boundaryspheric boundary

Method (Chae’s method)

Helicity transfer equation

s nPt dS)BA(u

dt

dΗ2

Apparent horizontal velocity of field line footpoint :

( LCT method) Normal component of photospheric magn

etic field : (line-of-sight magnetogram data) Vector potential for : (Fourier Transform method)

tu

nB

PAnB

Data and application

line-of-sight magnetogram data (SoHO/MDI)

96min cadence

calculation for about 5 days away from the limb

6 active regions

AR 10696

1st rotation

2nd rotation

AR 10696

AR 10365

1st rotation

2nd rotation

AR 10365

Summary

Active Regions(latitude, degree)

Helicity during the early phase[Mx2/5day]

Final Total flux [Mx]

Differential rotation

contribution [Mx2/5day]

AR 10696 (+8.16) -21.0x1042 3.49x1022 -0.48x1042

AR 10365 (-7.34) 8.40x1042 3.61x1022 0.48x1042

AR 8100 (-20.39) -13.5x1042 3.83x1022 1.3x1042

AR 10656 (-13.68) -43.5x1042 6.20x1022 2.6x1042

AR 7978 (-9.93) -2.45x1042 2.09x1022 0.22x1042

AR 10381 (-18.66) -1.75x1042 1.41x1022 0.075x1042

Conclusion

Magnetic helicity is supplied intensively during the growth of active regions or during flux emergence.

The range of the amount of helicity injected :

]/5dayMx101075.1 24242 [ 43.5 ~ The maximum helicity injection rate measured :

/h]Mx[ 107 241