Loann Brahimi

Data Scientist and Quantitative Researcher/Developer. I have a PhD in Astrophysics and an experience in developing data driven systems on financial markets.

PhD Thesis: Cosmic Rays transport in the weakly ionized Interstellar Medium

University of Montpellier, Montpellier, France

Thesis report

Cosmic rays play a fundamental role in the dynamics of the galaxy. The way it is injected into the interstellar medium and the processes it can impact over is an active research branch of Astrophysics. Although supernova remnants are thought to be the main cosmic ray accelerators there is no actual model for their injection that can efficiently explain their spectral distribution as observed on Earth and that can be validated by observations at high energy. Moreover, the effects of cosmic rays on the turbulent dynamic of the weakly ionized interstellar medium and in particular the galactic star formation rate stay unknown.In this thesis I have developed an injection and transport model for cosmic rays in the energy range 1 GeV to 100 TeV. The particles escape from Ia type supernovae remnants and propagate in the weakly ionized interstellar medium. This process is studied using a new 1D transport code called : CR SPECTRA. Having escaped from the remnant, cosmic rays drive magnetic turbulence at scales corresponding to their gyration radius which contribute to confine the particles close to the accelerator. Molecular clouds in the environment of the source represent preferential targets to probe the cosmic ray content using gamma-ray telescopes.In a second work, I have modeled the interactions of cosmic rays with a weakly ionized, thermally bi-stable interstellar medium using the 3D MHD code RAMSES. Cosmic rays transport properties are intimately linked with those of magnetic turbulence. In particular, I showed that under certain conditions, cosmic rays can prevent dense structures formations and can potentially contribute to reduce the star formation rate in the galaxy.

Publications

  • 2019: Non-linear diffusion of cosmic rays escaping from supernova remnants - II. Hot ionized media. Nava L., Recchia S., Gabici S., Marcowith A., Brahimi L., Ptuskin V.
  • 2019: Shock-accelerated cosmic rays and streaming instability in the adaptive mesh refinement code Ramses. Dubois Y., Commerçon B., Marcowith A., Brahimi L.
  • 2020: Nonlinear diffusion of cosmic rays escaping from supernova remnants: Cold partially neutral atomic and molecular phases. Brahimi L., Marcowith A., Ptuskin V.
  • 2020: Changes in cosmic-ray transport properties connect the high-energy features in the electron and proton data. Fornieri O., Gaggero D., Guberman D., Brahimi L., Marcowith A.

Talks

  • 06/2018: Poster presentation - CRISM-Grenoble, France
  • 06/2018: Talk - MODE-Montpellier, France
  • 11/2018: Poster presentation - Astrosim2018-Lyon, France
  • 05/2019: Talk - CFROS2-Montpellier, France
  • 07/2019: Talk - ICRC2019-Madison, WI, USA
  • 11/2019: Talk - Cargese2019-Corsica

Summer Schools

  • 06/2017: Astrosim - 2 weeks. Lyon, France
  • 03/2018: Data Sciences for Experimental Physics - 1 week, Montpellier, France
  • 06/2018: School Of Statistics - 1 week, Toulon, France
  • 09/2018: Plasma Astrophysics - 2 weeks, Los Angeles, CA, USA
  • 05/2019: Ecole de physique des Houches - Plasma Astrophysics - 2 weeks, Les Houches, France
  • 06/2019: Astronomy observations at the Observatoire: Midi-Pyrénées - 10 days, Pic du Midi, France

Teaching

  • 64h of general physics given to first year students
  • 100h of experimental physics given to third year students
  • 2 months, master student internship management: Analytical & Numerical studies of the Cosmic Rays propagation in the Interstellar Medium

\(\rightarrow\) Education