Simulating astrophysical kinetics in space and in the laboratory

Plasma jets that are interwoven with magnetic fields lace across the expanse of the universe. As these jets evolve, magnetohydrodynamic instabilities, like kink instabilities, develop and convert the plasma’s magnetic energy into energetic particles and radiation. Most current magnetohydrodynamic models are not able to capture these phenomena because they omit important kinetic physics.

“Plasma jets are really important in astrophysics since they are associated with some of the most powerful and intriguing cosmic particle accelerators,” said Paulo Alves, an author on the study. “Understanding the plasma physics that governs [the] instabilities [inside the jets] is essential to precisely understand how the dissipated magnetic energy is channeled and partitioned into heat, radiation and energetic particles.”

Alves et al. have developed a three-dimensional fully kinetic simulation of the kink instability to study the physics of the resulting particle acceleration.

The team found that nonlinear movements in the kink instability produced a coherent electrical field along the axis of the jet. Following fast curvature drifts across the magnetic field lines, the ions are accelerated so that up to 10 percent of the energy in the magnetic field was converted into nonthermal ionic energy. The team found that conditions for this acceleration mechanism are likely to be produced in laser-driven, high-energy-density plasma experiments.

According to Frederico Fiuza, principal investigator of the project, the particle spectra and acceleration efficiency predicted by these simulations can guide the interpretation of space and astronomical observations in future studies.

Source: “Nonthermal ion acceleration by the kink instability in nonrelativistic jets,” by E. P. Alves, J. Zrake and F. Fiuza, Physics of Plasmas (2019). The article can be accessed at https://doi.org/10.1063/1.5098478 .