The pulsar magnetosphere: new findings from PIC simulations

The pulsar magnetosphere is populated by an electron-positron pair plasma. The emission is produced by charged particles that are accelerated as they flow in the star's magnetosphere. Recently, much work has been done simulating the global pulsar magnetosphere, especially with particle-in-cell (PIC) codes. The main findings are the roles that certain mechanisms can play in establishing the magnetospheric structure and in the emission processes. In our group, we studied different magnetosphere configurations with different particle supply. When we inject particles only from the star surface, we find that electrons and positrons counterstream only along part of the separatrix inside the light cylinder and usually particles leave the magnetosphere and do not return to the star. Moreover we find the mechanisms that sustain the current closure and that they occur primarily through low energy particles crossing field lines near the light cylinder. The first result has implications for all the processes that are favored by counter streaming flows, as photon-photon pair production and the two stream instability. The second shows the composition of the currents that sustain a near-force-free magnetosphere, providing answers to some puzzling questions. These processes can have observational signatures that would distinguish this magnetosphere configuration from others with further modeling efforts. This kind of work qualitatively shows to be a great instrument to tackle many of the unsolved problems of the pulsar phenomenology.

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