Cosmic rays and their propagation in the Galaxy
Cosmic rays (CRs) offer us the only direct probe of the interstellar and intergalactic medium.
The energy spectra of the different CR species inform us about propagation processes and acceleration of relativistic particles.
Moreover their composition and abundancies tell us about CR source properties.
Cosmic rays are the most energetic particles swirling in the Milky Way at nearly the speed of light. They carry information on the Galactic environment during their journey from their source to the Earth. Yet, their origin and propagation are still escaping our understanding. At Stanford University she is working on a propagation code, called GALPROP, for modeling the path of cosmic rays from their potential sources throughout the Galaxy to the Earth, thus unveiling properties of cosmic rays and of the Galactic environment. Because cosmic rays are charged particles, their trajectory is bent by the Galactic magnetic fields. Thus, their direction does not point back to their sources. By solving numerical equations GALPROP brings together the most updated theoretical models and the most recent observations. The principle is that we model the directly measured particles back to their potential sources in their journey throughout the Galaxy. We first take the direct measurements of cosmic rays. For example she is interpreting the precise CR direct measurements from AMS02, Pamela, and Voyager, the first human-built instrument that is outside the Solar System. Then she traces them back to their potential emitting sources by modeling their radiation on their path with the interstellar medium and Galactic magnetic fields using the most recent available observations at all wavelengths from radio, microwave, X rays to gamma rays. By comparing models with observations she can gain information on cosmic rays.