Evolution snapshots of case lowtwist (from Fig. 4) and inftwist (from Fig. 5) at t = 16.2 and 8.4, respectively. The magnetic field structures are illustrated by colored 3D curves. The blue lines represent the undisturbed magnetic field, orange lines are relative to the CS, and green lines pass nearby the magnetic axis of MFRs. Vertical cuts give the current distributions; horizontal cuts on the bottom give the distributions of normal magnetic field. The thick black lines indicate neutral lines that separate the photosphere plane z = 0 into two areas with opposite normal magnetic fields.