A new model of Mercury's magnetospheric magnetic field

Two new missions will arrive at Mercury within the next decade. Interest in this enigmatic planet has therefore been revived in the magnetospheric community, and new models of Mercury's magnetic field are demanded. In the past, there have been several attempts to model the magnetosphere of Mercury based on simply scaling models of the Earth's magnetosphere. Although these scaled models have enjoyed many successes, their global magnetic configurations are determined by measurements made at the Earth, not at Mercury. In this paper, we develop a new empirical model of the Hermean field which is constrained wherever possible by the Mariner 10 dataset. We also explore the response of the model to upstream solar wind conditions. Data-based empirical models are an invaluable tool in magnetospheric physics at the Earth, and will doubtless prove to be just as useful at Mercury. The model developed here is generally applicable, and can be used to fit a much larger spacecraft dataset when it becomes available.