The advent of multi-messenger and transient astronomy is giving new insights into the most powerful particle accelerators of the Universe. Despite the recent breakthroughs in observation and modeling of transient phenomena, long-lasting mysteries still obscure the high-energy Universe, as the origins of ultra-high energy cosmic-rays (UHECR) and high-energy neutrinos are still unknown.

Deciding between the various candidate sources requires a precise modeling of the propagation, acceleration and interactions of cosmic-rays. Pulsar magnetospheres are good laboratories to study precisely particle acceleration. Using particle in cell simulations, we show that accelerated ions can escape from these environments. This could lead to various observational signatures, as for instance a diffuse gamma-ray emission in the galactic center region.