An MHD simulation of the inner heliosphere during Carrington rotations 2060 and 2068: Comparison with MESSENGER and ACE spacecraft observations

We present results from a new magnetohydrodynamic (MHD) model of the inner heliosphere. The model is adapted from the well-established Lyon–Fedder–Mobarry (LFM) MHD simulation code, which until recently mostly applied to studies of the terrestrial magnetosphere. We perform quasi steady-state simulations of two Carrington rotations: 2060 and 2068. During both of these periods, the heliosphere remained quiet and undisturbed by transient phenomena, making them well-suited for simulation studies of Corotating Interaction Regions (CIRs). The MHD model of the solar wind is driven at the inner boundary by the Wang–Sheeley–Arge (WSA) model of the corona augmented with empirical relations to infer the solar wind velocity, density, and temperature. Here we report on a validation exercise whereby LFM-helio simulation results are compared with in situ data from the Advanced Composition Explorer (ACE) and MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft. We find that the model successfully reproduces the large-scale configuration of the inner heliosphere, namely timing and duration of high-speed streams and heliospheric current sheet crossings, as reflected in ACE and MESSENGER observations. Discrepancies between in situ measurements and simulations, such as 1–2 day errors in the time of arrival of a CIR or the strength of the simulated magnetic field at the spacecraft, are attributed to the uncertainty in the specification of the coronal conditions, rather than a poor performance of the solar wind model. More comparisons between different inner heliosphere models driven with identical coronal conditions are suggested as a way to explore their comparative strengths and weaknesses.

► Lyon–Fedder–Mobarry (LFM) heliospheric 3D MHD model.
► LFM-helio simulations of Carrington rotations 2060 and 2068.
► Comparison of LFM-helio results and observations from ACE and MESSENGER spacecraft.
► The LFM-helio results agree well with the observations for CR 2060 and CR 2068.
► Discussion of the sensitivity of the LFM-helio to parameters at its inner boundary