Investigations of small-scale magnetic features on the solar surface

Viac o knihe

Solar activity is governed by the magnetic field, which also affects solar irradiance and, consequently, Earth's climate. This thesis focuses on two types of the smallest known magnetic features. The first part examines umbral dots, bright features in a sunspot's dark umbra. The properties of these dots confirm recent magneto-hydrodynamical simulations, showing that they differ from their surroundings primarily in the lowest photospheric layers, where temperature is higher and magnetic field strength is lower. Additionally, umbral dots exhibit strong upflow velocities surrounded by weak downflows, supporting their interpretation as localized columns of overturning convection. The second part investigates bright points, small brightness enhancements in intergranular lanes of the quiet Sun, attributed to magnetic flux concentrations. Data from the balloon-borne solar telescope SUNRISE is utilized, marking the first determination of bright point contrasts in the ultraviolet spectral range. A comparison of observational data with simulations shows a close match, contingent upon accounting for limitations in spectral and spatial resolution. Notably, 98% of synthetic bright points are linked to a nearly vertical kilo-Gauss magnetic field.