# 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 | |

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May 16, 2019 | Yvonne Elsworth, University of Birmingham: | |

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June 6, 2019 | Petri Käpylä, Max-Planck-Instituf für Sonnensystemforschung, Göttingen: | |

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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. |