Large-scale stability of the magnetotail

The large-scale stability of the magnetotail is investigated on the basis of resistive MHD simulations. The initial configurations are varied to study the influence of various properties on the tail stability in the presence of a dissipation mechanism. The properties studied include the flaring of the tail in the y direction, the decrease of typical properties, such as lobe field strength or current density, with distance from the Earth, and a thickening of the tail plasma sheet from midnight toward the tail flanks. All of these might contribute to a stabilization. The flaring, if isolated from the other properties, however, has little effect on the unstable evolution. All of the configurations considered experienced reonnection when a dissipation mechanism was available. However, the effects in the more stable configurations were more localized and less dramatic. Such differences in the tail configuration might be responsible for the differences between pseudo-onsets and full substorms.