4. Conclusions

• The traditional ground-based observations offer a good complement to the satellite data in studying the evolution of the sigmoid structure.



• The SF (sigmoid filament) forming period seems a lot more productive in solar flares and brightenings than other periods (* in Dick's list, 8 >B class flares in the first 4 days, while only one B.9 class afterwards). This may indicate that the frequent flaring is the result of continual adjustment of the magnetic configuration in the new-born active region.



• The flares spread along the filament route in a spiral-like structure centered at the major sunspot. This may indicate the twisted magnetic loop configuration. Some of the flares (eg. C5.7 flare on Aug17) show the association with the global context.



• The lifetime of the fully formed SF in this active region is about one day, during which time, the SF is active as indicated by rising and eruptions, but it is radiatively stable. Such may indicate that the magnetic configuration during this period reaches certain quasi-equilibrium status in favour of stable mass condensation in the SF structure.



• After the maturing period, the SF is weakened perhaps mainly due to the mass transport. In the late stage of SF, the integration occurs at the saddle point when new filament systems are formed. This may indicate emerging of new magnetic structure breaking the old system.

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