Simulation study of surfing acceleration in magnetized space plasmas

We present a numerical study of the surfing mechanism in which electrons are trapped in Bernstein–Greene–Kruskal (BGK) modes, and are accelerated across the magnetic field direction by the Lorentz force in magnetized space plasmas. The BGK modes are the product of an ion-beam Buneman instability that excites large-amplitude electrostatic upper-hybrid waves in the plasma. Our study, which is performed with particle-in-cell (PIC) and Vlasov codes, reveals the stability of the BGK mode as a function of the magnetic field strength and the ion beam speed. It is found that the surfing acceleration is more effective for a weaker magnetic field owing to the longer lifetime of the BGK modes. The importance of our investigation to electron acceleration in astrophysical environments has been emphasized.