2025-04-07 - 2025-04-11
Juan Manuel Borrero, Gregory Fleishman, Petri Käpylä, Ivan Milic, Rolf Schlichenmaier,
KIS (Institute for Solar Physics), Freiburg
With the Sun being a star, solar physics is often bundled up with stellar physics. While the physics involved is similar, the spatial, temporal, and spectral resolution used to study the Sun is still something that stellar physics will not reach in decades to come. Today, we are routinely observing spatial scales of 30-50 km on the solar surface, studying explosive events and wave phenomena happening on scales of seconds, measuring polarimetric signals weaker than 0.1% and reaching spectral resolution of a few hundreds of thousands, allowing us to probe the shapes of spectral lines and their polarization signals in detail and thus understand the depth variation of physical parameters in the solar atmosphere. Because of this, the Sun has always been a reference object and a testbed for theories and models in stellar structure, evolution, stellar atmosphere theory, and radiative transfer. Furthermore, the Sun gives a direct insight into a complicated interaction between the plasma, magnetic fields, and radiation, thus serving as a natural laboratory for plasma physics. Finally, the Sun shapes the heliosphere and the space weather, making it an extremely important object to study because it directly affects our technological society.
In this block course, lasting one week and consisting of lectures and hands-on exercises we will provide an introduction to some of the main concepts relevant in solar physics. The course will start with a general, historical introduction and description of the main observational facilities and techniques used to observe the Sun. We will then continue with the solar interior and describe the fundamentals of solar dynamo and deep convection. This field of research connects solar and stellar physics and deals with one of the most fundamental questions: how do solar (and stellar) activity cycles work? Afterward, we will tackle the physics of the lower solar atmosphere (photosphere and chromosphere) by focusing on the interaction between matter and radiation. This will allow us to introduce sophisticated methods for interpreting solar spectropolarimetric observations. In turn, this will enable us to understand how we reconstruct the structure of various solar features (sunspots, plage, filaments, prominences) from the observations. Finally, we will turn to the solar corona, the extended outer atmosphere that hosts a plethora of eruptive phenomena and various non-thermal and high-energy processes.
Schedule by day
Day 1: introduction and overview of the Sun; solar observations by Rolf Schlichenmaier
Day 2: physics of the solar interior (convection and dynamo) by Petri Käpylä
Day 3: physics of the solar photosphere (LTE polarized radiative transfer) by Juan Borrero
Day 4: physics of the solar chromosphere (Non-LTE radiative transfer) by Ivan Milic
Day 5: physics of the solar corona (high energy processes, flares, particle acceleration) by Gregory Fleishman
