Calendar

Floris Takens Seminar

The seminar of our group Dynamical Systems and Mathematical Physics is named after our founding father Floris Takens (1940-2010) whose research has been very influential on our work. This is also reflected in the spirit of our group seminar.

The painting of Floris Takens on the right is by Jacqueline Kasemier (Usquert, 2005).

Schedule

You can find the seminar schedule here. You can register to the google calendar with all mathematics seminars here.

Johann Bernoulli lectures

Johann Bernoulli lezing 33

Maandag 2 april 2024, 19:30 uur, Aula Academiegebouw

Ute Ebert (CWI and TU Eindhoven) The unseen structures of lightning

Abstract: Lightning is mostly known as lightning bolts and thunder between cloud and ground, but 90% of all large electric discharges in thunderclouds don’t produce such strikes to ground. Rather there is extensive discharge activity within and around thunderclouds. Fast (movie) cameras on ground, on air planes and from space, chemical and radio measurements, and detectors for high energy radiation have established:

• Intracloud electric discharges can extend over hundreds of kilometers horizontally.
• A zoo of “transient luminous events” can occur between cloud tops and the ionosphere.
• Active thunderstorms can emit high energy radiation like gamma-rays and electron-positron pairs, and they even can trigger nuclear reactions in air molecules.
• The discharges produce nitrogen-oxides and ozone which are the greenhouse gases.

I will briefly introduce these phenomena, and then explain the basic physical mechanisms across multiple scales. Starting from the collisions of electrons with molecules in an electric field, I will explain in particular the mechanism of electric field enhancement at the tips of growing discharge channels. These tips are soliton-like structures very far from thermal equilibrium, and the sources of the chemical and high energy emissions. And they are a unique point where observations with the radio telescope LOFAR in Exloo (Drenthe), laboratory experiments at TU Eindhoven and models of the CWI group in Amsterdam meet quantitatively! I will explain puzzles, paradoxes and the state of the art of our understanding.

The archive of Johann Bernoulli lectures could be found here.