Quantum electromagnetic effects explain flaring jets throughout the universe

Relativistic flows of particles—bright jets—recur in the universe. For regions with weak magnetic fields, like the interstellar medium, physicists have used magnetic-hydrodynamic modelling to understand these jets macroscopic aspects, such as formation and propagation stability. However, for extreme plasma environments with strong magnetic fields—for example, neutron star magnetospheres—magnetic-hydrodynamics fails to describe the jets’ strong nonlinearity where kinetic effects are coupled. Recently, a team of physicists in China have studied quantum electromagnetic (QED) effects for these environments and demonstrated the photons’ role for relaying energy between plasma particles undergoing relativistic flow. They report their findings in Physics of Plasmas.

Lead author Weipeng Yao says physicists have believed QED happens in extreme environments but research was lacking. The group advanced a theory for QED dynamics whereby photons traverse perpendicular magnetic fields arising in plasmas and relay otherwise-blocked charged particles across extremely-strong magnetic fields. Because relativistic particles emit synchrotron radiation, a cascading pattern of particles interacting with photons interacting again with particles develops, cumulatively spawning the dramatic jets astronomically observed.

The researchers tested their theorizing in two particle-in-cell simulations having very strong magnetic fields: one without and the other with a QED module. The without-QED module simulation did not produce gamma synchrotron radiation or particle-pair creation, while the with-QED simulation, demonstrated synchrotron radiation, photon relaying and particle pair creation, and energy flows at relativistic particle flow levels.

“By self-consistently considering the QED effects, including gamma photon synchrotron radiation and the pair creation process,” coauthor and lead researcher Bin Qiao says, “we have showed, for the first time, the macroscopic transport dynamics of relativistic flows changes tremendously with the microscopic QED effects.” Qiao adds this paper points to a new research area – QED for extreme astrophysics.

Source: “Relay transport of relativistic flows in extreme magnetic fields of stars,” by W. P. Yao, B. Qiao, Z. Xu, H. Zhang, H. X. Chang, C. T. Zhou, S. P. Zhu, X. G. Wang, and X. T. He, Physics of Plasmas (2017). The article can be accessed at https://doi.org/10.1063/1.4996903 .