Two-dimensional particle simulation of the boundary between a hot pair plasma and magnetized electrons and protons: out-of-plane magnetic field

Abstract

By means of a particle-in-cell (PIC) simulation, we study the interaction between a uniform magnetized ambient electron-proton plasma at rest and an unmagnetized pair plasma, which we inject at one simulation boundary with a mildly relativistic mean speed and temperature. The magnetic field points out of the simulation plane. The injected pair plasma expels the magnetic field and piles it up at its front. It traps ambient electrons and drags them across the protons. An electric field grows, which accelerates protons into the pair cloud's expansion direction. This electromagnetic pulse separates the pair cloud from the ambient plasma. Electrons and positrons, which drift in the pulse's nonuniform field, trigger an instability that disrupts the current sheet ahead of the pulse. The wave vector of the growing perturbation is orthogonal to the magnetic field direction and magnetic tension cannot stabilize it. The electromagnetic pulse becomes permeable for pair plasma, which forms new electromagnetic pulses ahead of the initial one. A transition layer develops with a thickness of a few proton skin depths, in which protons and positrons are accelerated by strong electromagnetic fields. Protons form dense clumps surrounded by a strong magnetic field. The thickness of the transition layer grows less rapidly than we would expect from the typical speeds of the pair plasma particles and the latter transfer momentum to protons; hence, the transition layer acts as a discontinuity, separating the pair plasma from the ambient plasma. Such a discontinuity is an important building block for astrophysical pair plasma jets.

Accepted for publication in Physics of Plasmas, 13 pages, 15 figures

References in corpus (7)

• Particle acceleration in relativistic collisionless shocks: Fermi process at last?
• On the structure of relativistic collisionless shocks in electron-ion plasmas
• Long Term Evolution of Magnetic Turbulence in Relativistic Collisionless Shocks: Electron-Positron Plasmas
• The Magnetic Rayleigh-Taylor Instability in Three Dimensions
• Relativistic magnetic reconnection in collisionless ion-electron plasmas explored with particle-in-cell simulations
• On the interaction of microquasar jets with stellar winds
• On the nature of the magnetic Rayleigh-Taylor instability in Astrophysical Plasma: The case of uniform magnetic field strength

Cited by in corpus (2)

• Relaxation of a Two Electron-Temperature Relativistic Hot Electron-Positron-Ion Plasma
• Three-dimensional structure and stability of discontinuities between unmagnetized pair plasma and magnetized electron-proton plasma