Abstract
Abstract. Spacecraft observations show that energetic ions are found in the Earth's magnetotail, with energies ranging from tens of keV to a few hundreds of keV. In this paper we carry out test particle simulations in which protons and other ion species are injected in the Vlasov magnetic field configurations obtained by Catapano et al. (2015). These configurations represent solutions of a generalized Harris model, which well describes the observed profiles in the magnetotail. In addition, three-dimensional time-dependent stochastic electromagnetic perturbations are included in the simulation box, so that the ion acceleration process is studied while varying the equilibrium magnetic field profile and the ion species. We find that proton energies of the order of 100 keV are reached with simulation parameters typical of the Earth's magnetotail. By changing the ion mass and charge, we can study the acceleration of heavy ions such as He+ + and O+, and it is found that energies of the order of 100–200 keV are reached in a few seconds for He+ + , and about 100 keV for O+.
Highlights
One of the unsolved problems of magnetospheric plasma physics concerns the generation mechanisms of energetic electrons and ions
This means that the electromagnetic perturbations create an efficient accelerator for protons in the magnetotail
In this paper we have investigated the dynamics and the acceleration of protons and heavier ions in a current sheet (CS) model that includes transient electromagnetic perturbations
Summary
One of the unsolved problems of magnetospheric plasma physics concerns the generation mechanisms of energetic electrons and ions. Perri et al (2009) and Greco et al (2010) considered the combined effect of a steady-state dawn–dusk electric field and of stochastic Fermi acceleration due to the presence of transient magnetic structures: by performing a two-dimensional (2-D) test particle simulation, they showed that proton energies of up to 80– 100 keV can be reached, in agreement with the above observations. Catapano et al (2015) generalized the well-known solution of the Harris current sheet to the case where several current carrying populations, i.e., multiple electron and ion populations, are present Those solutions allow for adjustment of the temperature profiles and the density profiles of the plasma sheet, in a wide range of configurations, with the magnetic field profile being obtained self-consistently.
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