Energy balance of sunspots and their geometrical topology

Sunspots are large magnetic field concentrations that appear darker than their surroundings as their magnetic fields inhibit the convection of the solar outer layers.

These structures appear associated with active regions (large magnetic bipolar structures) that ultimately drive the solar magnetic cycle.

In this eleven year cycle, the number of active regions and sunspots in the solar surface varies from almost complete absence to epochs in which they cover a significant part of the solar surface.Sunspots have been intensively studied during the last decades, with special emphasis in the photosphere.

However, there are still important open questions regarding their nature, the most significant one related to the energy transport mechanism that allows these structures to remain stable during tenths of days.

In addition, there is a plethora of small scale and highly dynamic features (umbral dots, light bridges, penumbral filaments) that might play an important role in the energy balance but whose characterization, from an observational point of view, still challenge current state-of-the-art instrumentation and inference models.In this project I will take advantage of the unique opportunity the solar physics community faces thanks to the beginning of the Solar Orbiter scientific operations.

I will:make use of full-spectropolarimetric and, for the first time, stereoscopic observations in order to challenge, from an observational point of view and in a quantitative way, the most advanced theoretical models,develop a new inversion code that can infer the 3D geometry of a sunspot with no degeneracy on the magnetic field azimuth, with no additional assumptions from magnetohydrodynamics theory, and with the ability to impose physical constraints into the inference process (such as divergence free magnetic field vector).The analysis of the 3D thermodynamic and magnetic topology of the sunspot will allow us 1- to infer the magnetic field topology unambiguously and its impact on the structure of the sunspots, 2- to evaluate the impact of umbral dots, light bridges and penumbral filaments on the energy balance of sunspots, 3- and, for the first time, address current theoretical model predictions from an observational point of view with physical inferences that do not rely on the exact same theory to be checked against.