FIELD LINE RESONANCES IN DISCRETIZED MAGNETOSPHERIC MODELS - AN ARTIFACT STUDY

For more than two decades numerical models of the Earth's magnetospher e have been used successfully to study magnetospheric dynamic features such as the excitation of ULF pulsations and the mechanism of field l ine resonance. However, numerical formulations simplify important prop erties of the real system. For instance the Alfven continuum becomes d iscrete because of a finite grid size. This discretization can be a po ssible source of numerical artifacts. Therefore a careful interpretati on of any observed features is required. Examples of such artifacts ar e presented using results from a three dimensional dipole model of the magnetosphere, including an inhomogeneous distribution of the Alfven velocity.