Numerical simulation of ion dynamics in the magnetotail magnetic turbulence: on collisionless conductivity

The ion dynamics in the distant Earth's magnetotail is studied in the case that a cross tail electric field and reconnection parity magnetic turbulenc e are present in the neutral sheet. A test particle simulation is performed for the ions, and moments of the ion distribution function are obtained as a function of the magnetic fluctuation level, delta B/B-0, and of the valu e of the cross tail electric field, E-y. It is found that magnetic turbulen ce can split the current carrying region into a double current sheet, in ag reement with inferences from observations in the distant magnetotail. The p roblem of ion conductivity is addressed by varying the value of the cross t ail electric field from zero to the observed one: we find that Ohm's law is not enforced, and that a non local, system dependent conductivity is neces sary to describe the ion response to the electric field. Also, it appears t hat the relation between current and electric field may be nonlinear.