Helicity on the Sun: What is it good for anyway?

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Helicity has done extremely well from 1999-present(much better than my 401K!)

Kusano et al (2002) had studied helicity and energy flow into photosphere in AR8100, Nov. 2-5, 1997

- Helicity injection due to vertical flows, 6 x 1026 Wb2, comparable with helicity injection due to horizontal flows

- Energy injected into corona due to helicity injection, 2 x 1025 J – larger than emitted by all flares during same period

Absolute value of the magnetic helicity induced by photospheric horizontal motions accumulated during the flaring time interval vs. the corresponding GOES X-ray flux integrated over the flaring time.

Moon et al, 2008, NOAA 8100- Impulsive helicity injections episodes coinciding with C, M-class flares.- Both positive and negative helicity in

injected by shear motions.- The flare X-ray flux integrated over the X-ray emission time strongly correlates with the magnetic helicity injected during the flaring interval.

Park et al 2008; 7 active regions- All major flares were preceded by a significant helicity accumulation, (1.8-16) x 1042 Mx2 over 0.5 to a few days.- average helicity change rate in the first phase shows strong correlation with the time-integrated soft X-ray flux

Park et al 2010; 378 ARs- (91 large ARs), difference in the magnetic

helicity injection rate between flaring ARs and nonflaring ARs by a factor of 2

- GOES C-flare-productive probability as a function of helicity injection displays a sharp boundary between flare-productive ARs and flare-quiet ones.

Komm & Hill, 2009, 1009 ARs

Reiner, et al. 2010- NHGV (Normalized Helicity Gradient

Variance) is effective at separating flaring and non-flaring active regions and even separates among C-, M-, and X-class flare producing regions.

- It also provides advance notice of flare occurrence, as it increases 2–3 days before the flare occurs.

You might not need helicity for a flare, but it helps.