Discovery of long-period magnetic field oscillations and motions in isolated sunspots

Abstract

We analyse the temporal evolution of the inclination component of the magnetic field vector for the penumbral area of 25 isolated sunspots. Compared to previous works, the use of data from the HMI instrument aboard the SDO observatory facilitates the study of very long time series ($\approx$1 week), compared to previous works, with a good spatial and temporal resolution. We used the wavelet technique and we found some filamentary-shaped events with large wavelet power. Their distribution of periods is broad, ranging from the lower limit for this study of 48 minutes up to 63 hours. An interesting property of these events is that they do not appear homogeneously all around the penumbra but they seem to concentrate at particular locations. The cross-comparison of these wavelet maps with AIA data shows that the regions where these events appear are visually related to the coronal loops that connect the outer penumbra to one or more neighbouring opposite polarity flux patches.

References in corpus (4)

• The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs -- Space-weather HMI Active Region Patches
• The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Optimization of the Spectral Line Inversion Code
• Long-Period Oscillations of Sunspots Observed by SOHO/MDI
• Search for torsional oscillations in isolated sunspots

Cited by in corpus (4)

• Spectropolarimetric Fluctuations in a Sunspot Chromosphere
• Oscillations In The Line-of-Sight Magnetic Field Strength In A Pore Observed By The GREGOR Infrared Spectrograph (GRIS)
• Limitations of the Ca II 8542 Å line for the determination of magnetic field oscillations
• Magnetic field fluctuations in the shocked umbral chromosphere