We present results from fully kinetic particle-in-cell simulations of the transport of astrophysical relativistic jets in magnetized intergalactic medium. As opposed to magnetohydrodynamic simulations, the results show that a strong charge-separation electric field, induced by the different responses between jet electrons and ions to the magnetic fields, significantly enhances the energy exchange between different species of charged particles and electromagnetic fields, thus playing a key role in determining the collimation and shape of the jet spectral energy distribution (SED). It is found that when the magnetic field strength increases, the jet collimation also increases while the power-law slope of the jet SED decreases; this provides potential enlightenment on related astrophysical observations.

Knot structures exist ubiquitously in young stellar object (YSO) jets, which are a key tracer in astronomical observation to estimate the jet properties and eventually the YSO's parameters (age, size, mass and so on). Using 2D and 3D radiation magnetohydrodynamic simulations of the laser-produced plasma jets in external poloidal magnetic fields, we present a systematic analysis on the formation mechanism and characteristics of knot structures in collimated jets. The simulations demonstrate that the multi-knot pattern in jets can be formed by the oblique internal shocks in only single ejection. It is found that the distance L between different knots in jet is determined by the ratio of its thermal pressure to magnetic pressure β as L ∝ Dβ 1/2 , where D is the jet transverse diameter. There is a factor about 0.4-0.6 between the knot and jet velocities. And radiation cooling effect can alleviate the intensity of the external magnetic field required for collimating jets. These findings are scaled to the conditions of YSO jets, and can be applied to explore some characteristics of the astrophysical jets.

Nuclear reactions in the plasma environment can be substantially different from those in conventional laboratory non-plasma cases, which have attracted considerable attention in the fields of fusion and astrophysics. To self-consistently model the nuclear reaction process during plasma dynamic evolution, an extended nuclear reaction calculation module is developed and included in two-dimensional particle-in-cell simulations. Through the self-consistent simulations, we systematically show that, apart from the plasma screening, the kinetic Weibel instability (WI) occurring in plasmas also results in significant enhancement of nuclear reactions, where the self-generated magnetic fields play a key role. Specifically, the self-generated magnetic fields in WI deflect ion motions, decreasing the relative velocity, and convert plasma kinetic energy to thermal energy, increasing the ion temperature. The simulation results show that, for the t ( d , n ) α reaction with a sharp resonance peak in the cross section, the reaction product yield is enhanced four times due to the WI. For nuclear reactions that have more prominent resonance peaks in the cross section, like 12 C ( p , γ ) 13 N , it is expected that such enhancements can reach up to one or several orders of magnitude.

Rayleigh-Taylor instability (RTI) is a fundamental physical phenomenon in fluids and plasmas and plays a significant role in astrophysics, space physics, and engineering. Especially in inertial confinement fusion (ICF) research, numerous experimental and simulation results have identified RTI as one of the most significant barriers to achieving fusion. Understanding the origin and development of RTI will allow for formulating mitigation measures to curb the growth of instability, thereby improving the odds of ICF success. Although there have been many theoretical and experimental studies on RTI under high energy density, there are few experiments to systematically explore the influence of magnetic fields on the evolution of magnetized RTI. Here, a new experimental scheme is proposed based on the Shenguang-II laser facility which uses nanosecond laser beams to drive modulation targets of polystyrene (CH) and low-density foam layers. A shock wave is generated after the laser's CH modulation layer is ablated, propagates through CH to low-density foam, and causes Richtmyer-Meshkov instability when the shock wave accelerates the target. When the laser pulse ends, the shock wave evolves into a blast wave, causing the system to decelerate, resulting in RTI in the reference system of the interface. This paper uses the open-source radiation MHD simulation code (FLASH) to simulate the RTI generated by a laser-driven modulation target. The evolution of RTI without magnetic field, Biermann self-generated magnetic field, and different applied magnetic fields are systematically investigated and compared. The simulation results show that the Biermann self-generated magnetic field and the applied magnetic field in parallel flow direction do not change the interface dynamics in the evolution process of RTI. Nevertheless, the applied magnetic field in the vertical flow direction can stabilize RTI and the Kelvin-Helmholtz vortex at the tail of the RTI spike. Magnetic pressure plays a decisive role. The results provide a reference for the follow-up study of target physics related to ICF and deepen the understanding of the fluid mixing process.