The majority of visible matter in the Universe exists as plasma, a state of matter composed of free electrons and ions, influenced by electromagnetic fields. Unlike common states of matter, many astrophysical and space plasmas are weakly collisional or even collisionless. In such systems, particles rarely undergo collisions, preventing the establishment of local thermodynamic equilibrium (LTE). As a result, conventional concepts such as resistivity, which typically describe energy dissipation in collisional plasmas, cannot be used  to understand energy conversion in non-LTE environments. Hence, a key open question in space plasma physics is: how is energy converted and dissipated in collisionless non-LTE systems?

Degrees of freedom unavailable to collisional plasmas arise in non-LTE systems, and there is a growing appreciation that these play a crucial role in energy conversion and dissipation. Two complementary theoretical approaches to describe energy conversion in weakly collisional or collisionless plasmas have been developed, namely the velocity-space cascade approach and an approach associated with entropy. These two approaches must be fundamentally interrelated.

This workshop will bring together researchers with expertise in theory, numerical modeling, and spacecraft observations to advance our understanding of energy dissipation in non-equilibrium space plasmas. It will also contribute to the research activities of the International Space Science Institute (ISSI) International Team “Unveiling Energy Conversion and Dissipation in Non-Equilibrium Space Plasmas.” ISSI, based in Bern, Switzerland, is a scientifically independent institute that supports multi-disciplinary collaborations to tackle pressing questions in space and Earth sciences.

CONVENORS

Giulia Cozzani, LE STUDIUM Integration Fellow
FROM University of Helsinki - FI 
IN RESIDENCE AT Laboratory of Physics and Chemistry of Environment and Space (LPC2E) / CNRS, University of Orléans, CNES - FR 

Matthieu Kretzschmar
Laboratory of Physics and Chemistry of Environment and Space (LPC2E) / CNRS, University of Orléans, CNES - FR