AbstractThe earlier work on the oscillatory phenomena in sunspot structures have supported in validating the detection of long-period oscillations, which are generated by the photospheric umbral response to the five minute p-mode global oscillations. We report here on the events of 3- min umbral oscillations which are detected within a duration of one hour from a single-polarity sunspot of active region NOAA 12132. The umbral oscillations that appear first around umbral boundaries is speculated to be excited by the wavefronts at the umbral-penumbral boundaries due to sub-photospheric or photospheric granular buffetings. The appearance of the wavefronts in spiral structures suggests that the wave guides are twisted. In addition, the newly formed running penumbral waves (RPWs) appears to be connected with the preceding RPWs.
Source Depth of Three-minute Umbral Oscillations
