Μάθημα : Ενημέρωση φοιτητών κατεύθυνσης Αστροφυσικής

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.