Solar Corona: Observations with space- and ground-based Coronagraphs for the Diagnostics of the Coronal Plasma Parameters

The outer atmosphere of the Sun or solar corona is an extremely complex and dynamic environment, featuring strong magnetic fields and high temperature plasma flowing at hundreds of kilometers per second. The most peculiar aspect of the solar corona lies in its temperature, which is several orders of magnitude higher (millions of degrees K) than the one at the solar surface (6000 K). In order to address the coronal heating problem, which is still puzzling the researchers’ community to the present day, it is crucial to study the magnetic field topology and the plasma physical parameters to investigate the heating mechanisms at play. However, in addition to the high temperatures, the sheer scale of the system poses strong limitations to in situ measurements, making remote sensing a complementary option. Nevertheless, isolating the faint brightness of the solar corona from the millions of times brighter solar disk is a challenging task. Therefore, this type of observation requires a specifically designed telescope, the coronagraph. This thesis focuses on polarimetric observations from different coronagraphs, summarized in Table 1. In the first part is reported the characterization of the sky brightness level at Dome C, Antarctica, which was selected as a possible site for ground-based observations by using the AntarctiCor telescope. Next, the instrument characterization of the Coronal Magnetograph (CorMag) is described. CorMag is a coronagraph designed for stratospheric balloon flights that was also used for observations of the solar corona during the total solar eclipse of 2024 from Torréon, Mexico. The data acquired during this eclipse campaign were analyzed with the goal of studying the magnetic field topology. Lastly, a numerical code was developed for the diagnostics of the coronal electron temperature. The code was used to generate the synthetic images expected to be acquired by the CODEX instrument. On November 2024, CODEX was installed on the International Space Station, and its images will be analyzed to derive the coronal electron temperature. CODEX will work in synergy with the Metis coronagraph on board the Solar Orbiter and providing the coronal electron density.