We investigate the total helicity change rate of active regions during the time period of three X-class and five M-class flares using MDI full-disk magnetograms which are sufficient to calculate the advection and the shuffling terms. Two out of three regions with X-class flares show a significant change in the helicity change rate, while none of the five active regions with an associated M-class flare shows this behavior. A closer investigation of the active regions associated with a helicity change reveals certain peculiarities that point to an artificial signal due to the magnetic reversal effect. This is supported by the fact that a simulation of the reversal effect reproduces the same shape of the helicity signal, although with an amplitude one magnitude lower. We investigate active regions with no flaring activity and determine the fluctuations of the helicity change rate due to instrumental effects to be 12 × 1040 Mx2 h-1.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science