Letters of Intent received in 2015

LoI 2017-263
Cosmic Rays and the interstellar medium

Topics

1. Sources of Galactic cosmic rays: theory
2. Sources of Galactic cosmic rays: multi-wave length observations
3. Cosmic-ray propagation in the interstellar medium: theory
4. Cosmic-ray propagation in the interstellar medium: observations
5. Ionization induced by low-energy cosmic rays: from diffuse interstellar medium to pre-stellar cores.
6. Dynamical effects of Cosmic Rays in the interstellar medium
7. The heliospheric shock: the latest results from in-situ measurements
8. Cosmic-Ray composition, Cosmic Ray leptons and anti-matter: the very last results from AMS-02

Rationale

Cosmic rays (CRs) are energetic particles mostly composed of nuclei, which have been discovered more than one century ago by Viktor Hess. The sources of Galactic CRs and the way these particles propagate in the interstellar medium are still subject to active research.

In the recent years the origin of CRs has been probed in particular by high-energy gamma-ray in-flight or ground-based experiments (Fermi, HESS, MAGIC, Veritas, Cangaroo) preparing the era of gamma-ray astronomy foresee with the advent of the Cerenkov Telescope Array (CTA). The results show that young supernova remnants appear to be sites of relativistic particle acceleration even if the nature of these particles (hadrons or leptons) is still debated. Yet other important questions are connected to the role of cosmic rays over the acceleration process itself. The magnetic field generation at the supernova remnant shock front probed by X-ray and radio facilities involves the strong non-linear nature of the acceleration process and invokes the development of refined plasma kinetic physics techniques.

In parallel, direct CR experiments detection (Pamela, AMS-02, Kascade, Auger) have accumulated an important amount of information about the energy, the composition and the angular CR spectra from GeV to up to EeV energy domains. Now, some particular features in the CR such as the Helium hardening are strongly debated and may appear important clues to understand the nature of the accelerators or the regime of propagation in the interstellar medium.

The role cosmic rays may have in the local or global interstellar medium dynamics has appeared as an emerging issue in the molecular cloud collapse process and hence in the stellar formation cycle especially with the measurements of the ionization fraction induced by MeV-GeV CRs in diffuse and dark clouds. It is now discussed about the possibility to have in-situ CR acceleration that could bring additional ionization in the star formation cores.

In connection to the above issue, the cosmic-ray spectrum at energies below which the solar modulation becomes important is currently under investigation by in-situ measurements thanks to the 70s launched satellites Voyager I and II. It is important to discuss about the true low-energy galactic cosmic ray spectrum end and if the above experiments are indeed measuring it.

Finally, the recent AMS-02 measurements of the cosmic-ray lepton component have opened issues connecting astrophysics and particle physics challenging the very nature of dark matter.

The CR research field hence appears to be at the center of different domains from astrophysics and space science physics to particle physics. Within the field of astrophysics CR research is now at the cross road of high-energy astrophysics and interstellar medium studies.

The symposium will be divided in 8 topics covering most of the physics associated with the interplay between cosmic rays science and different field of modern astrophysics. Let us specify them: cosmic rays and high-energy astrophysics (topics 1-2), cosmic rays and the interstellar medium (topics 3-6), interplay of cosmic rays and our solar system (topic 7), direct measurements and the origin of cosmic rays (topics 8).