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3D hybrid simulations of magnetotail dynamics. 3D hybrid simulations of magnetotail dynamics.
A.Greco
In this work we simulations-of-magnetotail-dynamics/' class='doin' >present a stationary three-dimensional hybrid code with ions resimulations-of-magnetotail-dynamics/' class='doin' >presented by particles and electrons by a
massless fluid. We use this code to study how electrons influence the magnetotail dynamics in the formation of a double
peak in the cross-tail current density, which is observed very often by CLUSTER crossing of the neutral sheet. We try to
compare the simulation results with the more recent observations.
The magnetotail current sheet is modelled as a magnetic field reversal with a normal magnetic field component B_n. A cross
tail electric field E_y is included. An ion test particle simulation is performed in these fields assuming an anisotropic plasma
source at the magnetospheric lobes, and ion distribution function moments, as density, current, and temperature are obtained.
Plasma is assumed quasi-neutral and we use the electron momentum equation (with m_e=0 and without collisions) and the
continuity equation to derive the electron current density.
One of the most interesting results we find is that the the main electron contribution to the total cross-tail current density
derives from the finite Larmor term of electron gradient pressure; further, this electron term is responsible for the formation
of a double peak in the total current density even in those case where the ion current density does not display any bifurcated
structure.
Once we obtain the total current, as the sum of ion and electron contributions, the correction (due to the presence of
electrons) to the assigned initial magnetic field is computed from the Ampere's law.
We also obtain a new electric field parallel to B due to the pressure gradient and this field could be responsible for many
particle acceleration processes.