In order to understand observable signatures from putative cosmic-ray (CR) sources in-source
acceleration of particles, their energy and time-dependent transport including interactions in an
evolving environment and their escape from source have to be considered, in addition to sourceto-
Earth propagation.
We present the code CR-ENTREES (Cosmic-Ray ENergy TRansport in timE-Evolving astrophysical
Settings) that evolves the coupled time- and energy-dependent kinetic equations for cosmicray
nucleons, pions, muons, electrons, positrons, photons and neutrinos in a one-zone setup of
(possibly) non-constant size, with user-defined particle and photon injection laws. All relevant
interactions, particle/photon escape and adiabatic losses are considered in a radiation-dominated,
magnetized astrophysical environment that is itself evolving in time. Particle and photon interactions
are pre-calculated using event generators assuring an accurate interactions and secondary
particle production description. We use the matrix multiplication method for fast radiation and
particle energy transport which allows also an efficient treatment of transport non-linearities due
to the produced particles/photons being fed back into the simulation chain.
Examples for the temporal evolution of the non-thermal emission from AGN jet-like systems with
focus on proton-initiated pair cascades inside an expanding versus straight jet emission region, are
further presented
