Fredagskollokvium: Fibrillar Structures in the Solar Chromosphere
Shahin Jafarzadeh, Postdoc, ITA
I 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 have shown 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 both 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. 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/m2) carried by the observed waves in the SCFs is marginally enough to heat the chromosphere (and perhaps the corona). Characteristics of these waves differ from those reported for other fibrillar structures, which, however, were observed mainly in the upper solar chromosphere.
Furthermore, I present observations of fibrillar structures through the mid-to-high solar chromosphere from coordinated observations of an active region with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging Spectrograph (IRIS) explorer. This provides us with temperature distributions of the entire field of view at multiple chromospheric heights, and in particular, of the fibrillar structures. A detail comparison between fibrillar structures simultaneously observed at several millimetre and ultraviolet bands of, e.g., ALMA 1.3 mm as well as IRIS Mg II h & k, Si IV, C II, and O I has provided us with new insights into the nature of these thread-like structures.