Das Magnetfeld der ruhigen Sonne und neu auftretender magnetischer Fluss - Dynamik, Energiehaushalt und Auswirkungen auf höhere atmosphärische Schichten
Zusammenfassung der Projektergebnisse
The project studied the appearance of new magnetic field concentrations in the Sun and the propagation of waves in the magnetized plasma of the solar atmosphere. Both these aspects are related to fundamental phenomena in solar physics, such as the heating of the upper solar atmosphere and the evolution of magnetic structures. Coordinated observing campaigns were planned to gather the data for the project, and regular meetings were scheduled to ensure a smooth and effective collaborations. The adversities encountered during the project included typical difficulties of ground-based observations (instrument availability, technical failures, and seeing conditions) and the onset of the COVID-19 pandemic. However, adequate datasets were gathered, which were complemented with archived observations and data from space-borne observatories and led to a series of high-quality studies. These addressed the main questions of the project and contributed to further advance and expand the scientific output of the involved partners. The evolution of two emerging regions, a sizeable one in an active region and an ephemeral one in the quiet Sun, was studied in detail. The former showcased the potential of high-resolution spectroscopy in Hα to detect plasma with different physical properties and showed how the interaction of two flux systems led to the onset of a surge, with coexisting plasma upflows and downflows. The latter study comprised one of the most detailed studies of its kind, monitoring phenomena across the entire solar atmosphere and involving solar plasma from 1000 to 1 000 000 K. The emergence of small-scale magnetic flux can lead to highly variable and eruptive activity. Other aspects of the importance of small-scale phenomena were elucidated in a study of a miniature filament and its eruption. It was seen through high-spectral, highspatial, and high-temporal resolution observations that these phenomena exhibit stark similarities with their large counterparts, shaping the dynamics of the quiet Sun at the smallest observable scales. The partners also addressed wave propagation. The contribution of the flux carried by waves to chromospheric energy losses was examined in quiet Sun and a weak plage regions, combining 1D modelling and observations. It was found that 90% of the acoustic energy is deposited up to 1400 km. This is sufficient to heat the chromosphere in the quiet Sun but not in active regions. The properties of magnetoacoustic wave fronts in sunspots were investigated using time-series of spectral imaging observations. The variation of the acoustic cut-off frequency in a sunspot was determined, and it was concluded that it presents variability which is often ignored by current analytical estimations. Then the shape of the wavefronts was explained in terms of the twist in the magnetic fields, which was determined via spectropolarimetric inversions. Equally important to the produced results is the legacy of the project. Motivated by the abundance of high-resolution spectral observations from the VTT, new ways to utilized them were sought. An Hα classification scheme based on t-SNE was proposed, which showed that it is possible to cluster spectra from regions with different physical properties. Further work is underway, including synthetic spectra from simulated photosphere and other chromospheric lines for feature detection. In additionally, in order to derive consistent magnetic field information from the high-spectral resolution observations of the VTT, a Stokes-I inversion scheme was put forward. Including most lines in the spectral region of CrI led to an adequate determination of the magnetic field strength and inclination in a pore. Finally, two new instruments were put together for the acquisition of high-quality solar observations. A six camera imaging systems was installed at the GREGOR telescope , which is routinely used since early 2022, providing fast, high-resolution imaging in G-band, blue continuum, Ca II H, TiO, and Hα. A system with four large-format CMOS cameras was installed for fast spectral scans at the VTT, allowing simultaneous observations in four spectral regions. Sciene verification wil be completed in 2023 so that FaMuLUS will become a facility instrument at VTT in 2024. The new instruments, HiFI+ and FaMuLUS, have dedicated data reduction pipelines, which were developed within the scope of this DFG project. Data of HiFI+ becomes publicly available after a one year embargo period. The FaMuLUS data will become public immediately after observations and data reduction.
Projektbezogene Publikationen (Auswahl)
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Height variation of the cutoff frequency in a sunspot umbra. Astronomy & Astrophysics, 617, A39.
Felipe, T.; Kuckein, C. & Thaler, I.
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Spiral-shaped wavefronts in a sunspot umbra. Astronomy & Astrophysics, 621, A43.
Felipe, T.; Kuckein, C.; Khomenko, E. & Thaler, I.
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A persistent quiet-Sun small-scale tornado. Astronomy & Astrophysics, 643, A166.
Tziotziou, K.; Tsiropoula, G. & Kontogiannis, I.
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Emergence of small-scale magnetic flux in the quiet Sun. Astronomy & Astrophysics, 633, A67.
Kontogiannis, I.; Tsiropoula, G.; Tziotziou, K.; Gontikakis, C.; Kuckein, C.; Verma, M. & Denker, C.
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High-resolution spectroscopy of a surge in an emerging flux region. Astronomy & Astrophysics, 639, A19.
Verma, M.; Denker, C.; Diercke, A.; Kuckein, C.; Balthasar, H.; Dineva, E.; Kontogiannis, I.; Pal, P. S. & Sobotka, M.
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High-resolution Spectroscopy of an Erupting Minifilament and Its Impact on the Nearby Chromosphere. The Astrophysical Journal, 898(2), 144.
Kontogiannis, I.; Dineva, E.; Diercke, A.; Verma, M.; Kuckein, C.; Balthasar, H. & Denker, C.
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Observational study of chromospheric heating by acoustic waves. Astronomy & Astrophysics, 642, A52.
Abbasvand, V.; Sobotka, M.; Švanda, M.; Heinzel, P.; García-Rivas, M.; Denker, C.; Balthasar, H.; Verma, M.; Kontogiannis, I.; Koza, J.; Korda, D. & Kuckein, C.
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Classification of High-resolution Solar Hα Spectra Using t-distributed Stochastic Neighbor Embedding. The Astrophysical Journal, 907(1), 54.
Verma, Meetu; Matijevič, Gal; Denker, Carsten; Diercke, Andrea; Dineva, Ekaterina; Balthasar, Horst; Kamlah, Robert; Kontogiannis, Ioannis; Kuckein, Christoph & Pal, Partha S.
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Multiple Stokes I inversions for inferring magnetic fields in the spectral range around Cr I 5782 Å. Astronomy & Astrophysics, 653, A165.
Kuckein, C.; Balthasar, H.; Quintero, Noda C.; Diercke, A.; Trelles, Arjona J. C.; Ruiz, Cobo B.; Felipe, T.; Denker, C.; Verma, M.; Kontogiannis, I. & Sobotka, M.
