The Section of Astrophysics, Astronomy and Mechanics of the Department of Physics of the National and Kapodistrian University of Athens offers a series of virtual Colloquia in Astrophysics that started in October 2020.
Organizer: Prof. Maria Petropoulou
Speaker: Dr. George Livadiotis (Princeton University, USA)
Speaker info: link
Title: Understanding thermodynamics in space plasmas
Abstract: Space largely consists of collisionless plasmas, where particle–particle collisions are rare. Consequently, thermalization—the pathway toward thermodynamic equilibrium—is often governed by wave–particle interactions. Collisional particle systems are described by classical thermodynamics, which is based on the absence of correlations among particle velocities that follow the Maxwell-Boltzmann (MB) distributions. In contrast, space plasmas are characterized by long range interactions that induce correlations among particles, and cannot be described by the classical thermal equilibrium; instead, they reside in stationary states described by kappa distributions—called generalized thermal equilibrium. This contrasts with the classical thermal equilibrium, which is a limiting version of thermal equilibrium described by MB distributions. The transport equation of kappa — the fundamental thermodynamic parameter that labels kappa distributions, is connected with the transfer of entropy.
During the presentation, we will demonstrate the transfer of entropy with two examples: (1) The interaction of the thermal solar wind ions with the highly ordered population of pickup ions — newly ionized neutrals captured by the solar wind’s magnetic field, has an effect of entropy transfer; this leads to the observed evolution of the kappa distributions through the heliosphere. (2) The solar radio bursts—sudden and intense emissions of radio waves from the Sun—can transfer entropy to solar energetic particles, thereby affecting their thermodynamic properties.
Finally, we discuss how heliospheric observations from the recently launched Interstellar Mapping and Acceleration Probe (IMAP) mission will allow for detailed characterization of space plasma particle thermodynamics in the heliosphere. In particular, IMAP will study charged and neutral particles using a suite of specialized instruments designed to capture and analyze particles from both the solar wind and the interstellar medium.
Speaker: Prof. Ersin Göğüş (Sabanci University, Turkey)
Speaker info: link
Title: The Strongest Magnets in the Milky Way and Beyond
Abstract: TBA
We are looking forward to your participation!
You can also follow us on Facebook at Astro UoA Colloquia.
Note: In person colloquia will take place at 4:00 PM (EET) at the Seminar room of the Section of Astrophysics at NKUA.
Connection information:
https://uoa.webex.com/uoa/j.php?MTID=m300a2a81022dd533d49b66e3459530f9
Wednesday, December 17, 2025 4:00 PM | 2 hours | (UTC+02:00) Athens, Bucharest
Meeting number: 2780 635 5361
Password: h9zJwQzJE64