Light curve of the solar-like pulsating star KIC 6448798 observed by Kepler from Q0 to Q14 (top left panel). From top right to bottom right panel, we show the photometric magnetic activity index, S_ph,k, calculated using sub-series of size k × P_rot with k = 1,3,5,10, and 30. The black dashed line represents the general magnetic index, S_ph, the red dot-dashed line corresponds to the mean magnetic index, S_ph,k.