2017AstBu..72..178B

Global magnetic fields of flare stars evolve very fast – at times of tens-hundreds of days. In our opinion,this is due to mutual addition of local magnetic fields generated by the differential rotation of these objects. With the example of two two flare stars, OT Ser and YZ CMi, we consider possible mechanisms of generation and YZ CMi, we consider possible mechanisms of generation and disspation of local and global magnetic fields and the mechanism of "magnetic deceleration" of these stars according to the scheme "differential rotation - generation of local magnetic fields -fluorescence of energy accumulated by local magnetic fields during flares." We also estimated the rotation energy and global magnetic field for OT Ser and YZ CMi. It is shown that even strong dissipation of the accumulated local magnetic energy in the lare on February 9, 2008 (UT 20:22:00) in YZ CMi has not had any impact on the global magnetic field.