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PhD Thesis: The dynamic chromosphere: Results and techniques with an observational approach
  Thesis defense

Friday 07 September 2018
from 13:00 to 16:00
at FA32
Speaker : Carolina Robustini (Institute for Solar Physics, Department of Astronomy, Stockholm University)
Abstract : The chromosphere is a critical interface between the relatively cold photosphere and the hot corona. Its landscape is rich in very dynamic phenomena such as jets, spicules, and surges, which are thought to play an important role in the heating of the Sun’s upper atmosphere. However, these events are often driven by mechanisms that are not entirely understood owing to the complex physical conditions governing the chromosphere. In the average chromosphere, the magnetic pressure often dominates over the gas pressure. Thus the structure and dynamics of this layer are mainly regulated by the magnetic field configuration. This thesis is based on three projects that investigate some chromospheric dynamic phenomena and their relation with the magnetic field. In these projects, we follow an experimental approach, by analysing high-resolution ground-based observations with spectropolarimetry as well as satellite co-observations. The first project focuses on exotic fan-shaped jets that are sometimes observed above sunspot light bridges. We investigate the thermal properties and the dynamics of these jets, and suggest magnetic reconnection as the mechanism producing these events. In the second project, we study a δ-sunspot penumbra that harbours fan-shaped jets. By using inversion techniques, we retrieve the 3D structure of the magnetic field and temperature, which reveal that the magnetic reconnection driving the fan-shaped jets occurs in the lower chromosphere. In the third project, we investigate the role of the magnetic field in a unipolar supergranular network cell having a radial arrangement of the fibrils. For this chromospheric structure, we suggest a model of the magnetic topology based on multiwavelength observations and inversion techniques.

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