Séminaire / Seminar GReCO |
| « Opening the door of the pulsar magnetosphere with the key of quantum electrodynamics: quantum synchrocurvature radiation and ??->e+e- pairs » |
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Guillaume Voisin |
| The pulsar magnetosphere is the siege of extreme conditions where electrodynamics reigns barely challenged by the gravity of the neutron star. This is explained by extreme magnetic fields, reaching up to a few 10^9 Teslas close to the surface. In a struggle to keep corotating with the star, the electron-positron pair plasma opens up 10^12 Volts potential gaps that accelerate leptons to energies only limited by radiation reaction, up to Lorentz factors of about 10^7. Radiation reaction is mostly the result of synchrocurvature radiation: particles spiral around curved magnetic field lines. We will see that the quantification of this radiation is possible and generalises quantum synchrotron to curved magnetic fields. More importantly, we will see how this quantization resolves the paradoxes inherent to the classical theory when applied to these extreme environments. In a second time, we will follow the gamma photons abundantly produced by synchrocuvature radiation in their short journey across the magnetosphere. There, they undergo large probabilities of producing new pairs either by interacting with the magnetic field, or with a background x-ray photon. We will see that the latter mechanism might be able to explain the sustained activity of even low-magnetic-field pulsars (only 10^4 Teslas), but that further theoretical developments are necessary. |
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jeudi 14 mars 2019 - 10:30 Amphithéâtre Henri Mineur Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |