Fredagskollokvium: Fibrillar Structures in the Solar Chromosphere
Shahin Jafarzadeh, Postdoc, ITA
We present observations of dynamic, slender bright fibrils seen in high-quality narrow-band Ca II H images from the SuFI instrument onboard the SUNRISE balloon-borne solar observatory. We show that these slender Ca II H fibrils (SCFs) map magnetic fields in the low solar chromosphere derived from magnetostatic extrapolation of the photospheric field obtained with SUNRISE/IMaX and SDO/HMI. Our analysis reveals the prevalence of magnetohydrodynamic (MHD) kink and sausage waves in the SCFs, propagating at high-frequencies (up to 30 mHz), with speeds on the order of 9-15 km/s. Characteristics of these waves differ from those found for other fibrillar structures, which, however, were observed mainly in the upper solar chromosphere (from observations with SST/CHROMIS). These MHD waves are found to be similar to those observed in the photospheric magnetic elements, but also penetrating into the lower solar chromosphere. The estimated energy flux (~ 15 kW/m^2) carried by the observed waves in the SCFs is marginally enough to heat the chromosphere (and perhaps the corona). We have further explored slender fibrillar structures through the entire solar chromosphere from coordinated observations of an active region with the Interface Region Imaging Spectrograph (IRIS) explorer and the Atacama Large Millimeter/submillimeter Array (ALMA). These have provided us with new insights into the nature of these thread-like structures.