Finding the Lyon-Fedder-Mobarry magnetopause: A statistical perspective

摘要

The determination of the location and global structure of the magnetopause is not a well-defined problem, either in satellite data or in magnetohydrodynamic (MHD) models. Assessing the accuracy of MHD models by comparing single-point crossings of the magnetopause cannot provide a complete picture of the accuracy of the model. We evaluate the accuracy of magnetopause location in the Lyon-Fedder-Mobarry (LFM) MHD model by examining LFM behavior on a statistical, rather than single event basis. Empirical magnetopause models seek to fit a functional form to large data sets of magnetopause crossings parameterized by controlling factors such as solar wind ram pressure and interplanetary magnetic field orientation. By comparing the LFM magnetopause with the empirical magnetopause models in their region of greatest accuracy, we determine the overall accuracy of the LFM magnetopause position in the dayside equatorial plane. We find the LFM magnetopause to be earthward of the empirical models by, on average, 0.5 to 1.0 R E at noon and 1.0 to 2.0 R E at dusk. This observed discrepancy is shown to be, at least in part, due to the insufficient ring current in the LFM.