Ruhr-Universität Bochum
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SFB 591


SFB 591
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SFB 591 » Projekte » A6


The role of heating and cooling in structure formation of plasmas in the interstellar medium and the laboratory

Project manager

Prof. Dr. Ralf-Jürgen Dettmar
Astronomisches Institut
Ruhr-Universität Bochum

Dr. Mikhail Z Tokar
Institut für Plasmaphysik
Forschungszentrum Jülich

Prof. Dr. Reinhard Schlickeiser
Institut für Theoretische Physik IV
Weltraum- und Astrophysik
Ruhr-Universität Bochum

Mitarbeiter »


Heating and cooling processes determine the relevant parameters such as ionization degrees and recombination rates in many astrophysical and laboratory plasmas. There are important observational evidences in both fields that models can only be improved by a deeper understanding of the basic concepts.

Heating and cooling processes can contribute both in astrophysical and laboratory plasmas to radiation instabilities and thus to structure formation which is of common interest.

In the past ten years the Diffuse Ionized Gas ("DIG") was identified in many galaxies as an important, fully ionized component of the interstellar medium with an average temperature of 10^4 K. The emission lines which are produced in this plasma cannot be explained from photoionization by young, hot stars only. Therefore an additional heating source is searched for which could explain e.g. the slow rise of the temperature of the gas with increasing distance to the galactic midplane. Different possible mechanisms were proposed, among them plasma-specific processes such as magnetic reconnection, photoelectric heating by the galactic dust component or dissipation of MHD-waves.

This project combines both astrophysical observations to diagnose the heating of galactic halos and different theoretical works about heating processes and instabilities. Furthermore specific experiments are planned to study similar processes in the laboratory which e.g. lead to the formation of MARFEs.

For a better understanding of the additional heating processes in the diffuse ISM an improved description of the boundary conditions is necessary: Which astrophysical parameters determine the occurrence of the heating (e.g. radiation field, magnetic field)? This requires detailed mapping of the brightest diagnostic emission lines in the Milky Way as well as in other selected galaxies which are close by. These lines are all forbidden emission lines of various elements, most prominent of oxygen. In order to gain more information about the physical conditions in this plasma the data from more emission lines are needed. These could then be used to constrain the temperature gradient, ionization structure, and excitation conditions more accurately. In particular a new possibility is offered here in the near infrared wavelength range by new telescopes and detector technologies.

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