Erosion of the dayside magnetosphere at Mercury in association with ion outflows and flux rope generation

摘要

In preparation for the arrival of the MESSENGER spacecraft at Mercury, and to further understanding of the Mariner 10 and ground-based observations, 3-D multifluid simulations are used to predict Mercury's magnetospheric response to forcing from the solar wind. The model, which includes both heavy (Na+) and light (He+) ionospheric ion populations, predicts that solar wind access to Mercury's surface is highly asymmetric and dependent on the strength and direction of the interplanetary magnetic field (IMF). In particular, during southward IMF much of the dayside magnetic field can be eroded, and enhanced plumes of sodium ions (with geometry similar to ground-based emission observations) outflow at high latitudes into the solar wind. Development of reconnection in association with flux ropes similar to those at Earth are seen but with a shorter time scale of development and a closer radial distance (3–5 RM).