Thesis

Formation and evolution of H-alpha filaments at chromospheric heights

• Call:

  IDPASC Portugal - PHD Programme 2019

• Academic Year:

  2019 / 2020

• Domain:

  Astrophysics

• Supervisor:

  Nuno Peixinho

• Co-Supervisor:

  Ricardo Gafeira

• Institution:

  Universidade de Coimbra

• Host Institution:

  Universidade de Coimbra

• Abstract:

  The solar atmosphere provides a unique laboratory for studying physical processes occurring throughout the universe but, due to there proximity, they are better observed in the sun. As a result of all these physical processes, several features can appear in the solar atmosphere at different heights which are observed at different spectral ranges. One of these features, observed in the H-alpha spectral line, are called solar filaments when observed in the disk or prominences when observed outside the limb. They are one the oldest structures observed in the sun but until today few is know about what triggers there formation and the physical processes that lead to that. A better understanding of these structures is also important due to there relation to the coronal mass ejection (CMEs) that can hit the earth and disturb the earth magnetic field with drastic consequences on Earth telecommunications, GPS, etc., and all technology dependent on these system. The goal of this PhD thesis is to study the dynamics of the solar atmosphere at small and large size-scale, mainly in the chromosphere, based on multi-spectral-line observations by means of radiative transfer inversion codes in order to establish there magnetic and thermodynamic context, in order to predict its formation and evolution. This project aims to study the temporal evolution of chromospheric structures that lead to the formation of the H-alpha filaments using multi-spectral-line observations in small and large spatial scales. There are multiple reasons for focusing on this topic. The most important are related to improve our yet little understanding of the formation of these structures, and to seek and understand their correlation with the solar atmospheric conditions, the triggers for coronal mass ejections (CMEs), and how to effectively predict these CMEs. Since all these processes have manifestations at large scales, it is imperative that low-resolution solar observations with a large field of view are used as a complement to high-resolution satellite data. Such observations are available from several sources like the Solar Space Telescope SDO, and ground-based instruments like the Spectroheliograph at the Observatory of Coimbra and Swedish Solar Telescope (SST) and new techniques are bringing new light to the usage of those datasets. Brand new inversion codes that allow computation of non-local thermodynamic equilibrium (NLTE) spectral lines are now available opening the door to new studies. Thus in this PhD project, datasets will be analysed using new solar atmospheric inversion codes that allow retrieving the atmospheric parameters a study their evolution, mainly in the chromosphere. The contributions to the spectral line formation depends significantly on the magnetic activity. Therefore, multiple-line studies with polarimetric information (Ca II K, H-alpha together with photospheric lines like Fe) are essential to constrain and derived physical parameters of the solar atmosphere in height, and finally, shed light on the true origin of these features. The scientific questions which shall be tackled address the dynamics of the solar atmosphere that leads to the appearance and therefore evolution of the H-alpha filaments.