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Workshops > The ionization fraction of the interstellar medium

This workshop is postponed later in 2020 or in 2021. The organizing committee will present the workshop goals during a presentation.

The ionization fraction of the interstellar medium

Workshop proposed by Emeric Bron (emeric.bron@obspm.fr, LERMA), Ioan Schneider (ioan.schneider@univ-lehavre.fr, LOMC), and Dahbia Talbi (dahbia@umontpellier.fr, LUPM)


The fraction of ionization of interstellar gas controls several key processes governing the evolution of interstellar matter, from its impact on gas dynamics as it controls the coupling of the gas to the magnetic field, to the development of a rich chemistry through fast ion-neutral reactions. This makes the ionization fraction a key parameter in our understanding of both the star formation process and the development of chemical complexity.

However, the ionization fraction is not directly observable and indirect estimation methods relying on astrophysical models are necessary. A detailed knowledge of all the processes controlling both the ionization balance on the gas, and its impact on observable tracers is thus key.

In this workshop, we aim at gathering observers, modelers and chemical-physicists and discuss how recent advances in observational capabilities, model development, and experimental and theoretical studies of the key microphysical processes can shed a new light on our knowledge of the ionization fraction in the interstellar medium. We will try to answer the following questions:

  • How well can we measure the ionization fraction across all phases of interstellar clouds, form diffuse envelopes to dense cores? What are the reliability and the limitations of the observable tracers used to estimate the ionization fraction?

  • How well do the models explain the observed ionization fractions? What indirect impacts of the ionization fraction (on the dynamics, the chemistry,...) predicted by the models can be observationally tested?

  • What are the key microphysical processes governing the ionization balance and its impact on the interstellar medium ? Which ones are well characterized, experimentally or theoretically, and which ones need yet to be investigated?

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