An empirical model of the solar wind flow around Mars

Abstract

An empirical model that describes the proton velocity around Mars has been developed. The analytical axially symmetric model is based on Automatic Space Plasma Experiment with a Rotating Analyzer three‐dimensional (3‐D) proton velocity observations on the Phobos 2 spacecraft near Mars in early 1989. The model includes a bow shock, a magnetopause, and an impenetrable obstacle a few hundred kilometers above the surface of Mars. The flow model can be used to model both an open and a closed magnetosphere. The model velocity values are found to describe rather well the 3‐D proton velocity observations in the Martian magnetosheath and magnetosphere both on the dayside and on the nightside. Characteristics of the velocity field are studied on the basis of an ideal MHD model, assuming that the magnetic field is frozen into the proton flow and that there are no proton sources or sinks. Under these assumptions the velocity field can be used to calculate the proton density and the magnetic field. When the proton density and the magnetic field are compared with the observations, quite good qualitative agreement between the model and the data is found. Our model shows that a relative simple flow model can predict several observed plasma and field features near Mars.