KIS Astrophysical Colloquium 2018

The colloquium usually takes place on Thursdays at 11:30 if not stated otherwise.

Upcoming Talks:
February 21, 2019 Joten Okamoto, NAOJ Tokyo: The strongest magnetic fields in sunspots and their statistical properties
Sunspots are concentrations of magnetic fields on the solar surface. Then, where is the strongest field in each sunspot ? It is generally located in an umbra, but sometimes stronger fields are found outside umbrae, such as a penumbra and a light bridge. The formation mechanism of such strong fields outside umbrae is still puzzling. Now we have numerous high-quality datasets taken with the Hinode/Spectro-Polarimeter over 10 years, which motivate us to address this question via a statistical analysis of strongest fields in sunspots. Hence, we complied a ranking list of active regions by their largest field strengths and investigated conditions for appearance or formation of strong magnetic fields. In this seminar, we will introduce a sunspot with a field strength of 6250 G as a case study, and then discuss the key features to produce strong fields in a statistical sample.
May 09, 2019 Kolloquium zu Ehren von Wolfgang Schmidt
May 16, 2019 Yvonne Elsworth, University of Birmingham:
June 6, 2019 Petri Käpylä, Max-Planck-Instituf für Sonnensystemforschung, Göttingen:
Past Talks:
January 31, 2019 Antonio Ferriz Mas, University of Vigo, Spain: Magnetic Helicity: From knot theory to solar pyhsics
The linking number or "Verschlingungszahl" is an integer invariant that describes the linking of two closed curves in 3-D space. It was introduced by Gauss in the form of a double line integral and it is one of the oldest topological results. In the first part of the talk I will show, using Differential Geometry, that the linking number and Gauss' double line integral are at the heart of the definition of helicity, a key concept in Topological Fluid Mechanics with wide applications in solar magnetism. In the second part of the talk I will address the question under which circumstances the kinematic (hydrodynamic) and the magnetic (MHD) helicities are conserved quantities; helicity conservation is determined by the physics of the problem and is no longer a purely mathematical question.