Oscillations of Ellipsoidal Solar Active Regions

Four active regions (AR) of the sun are studied. Observational data were obtained from directly visible (line of sight) sharp_cea_720s SDO/HMI magnetograms. The data for each AR were processed by a least squares method in an ellipse. Using a sequence of images after processing the data in all the AR, oscillations of the major and minor axes of the ellipse, as well as of the angles of inclination of the major axes to the equator, were detected as functions of time. These oscillations are analyzed by a fast Fourier transform method which reveals several periods with confidence levels exceeding 95%. It is found that the major axes oscillate with periods of 6-8 h and the minor axes, with periods of 6-8 h and 4-5 h. The angles of inclination of the major axes to the equator of three of the AR oscillate with a period of approximately 4 h.