Development of the 3-D MHD model of the solar corona-solar wind combining system

• Published in: Journal of Geophysical Research - Space Physics Vol. 114; no. A7; pp. A07109 - n/a
• Main Authors: Nakamizo, A., Tanaka, T., Kubo, Y., Kamei, S., Shimazu, H., Shinagawa, H.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Geophysical Union 01.07.2009; Blackwell Publishing Ltd
• Subjects: Computational Geophysics; Corona; Earth sciences; Earth, ocean, space; Exact sciences and technology; expansion factor; Forecasting; Interplanetary Physics; MHD simulation; Modeling; Solar Physics, Astrophysics, and Astronomy; solar wind; Solar wind sources; Space Weather; MHD simulation; expansion factor; space weather; solar wind; altitude; Solar corona; Magnetic flux; Plasma; Singularity; magnetic field; Weather forecast; topology; fine-grained materials; Wind velocity; global; digital simulation; low temperature; Source function; expansion; Sector structure; MHD model; Energy equation; Flux tube; Magnetic structure; interplanetary space; frame structure
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2008JA013844

In the framework of integrated numerical space weather prediction, we have developed a 3‐D MHD simulation model of the solar surface‐solar wind system. We report the construction method of the model and its first results. By implementing a grid system with angularly unstructured and increasing radial spacing, we realized a spherical grid that has no pole singularity and realized a fine grid size around the inner boundary and a wide‐range grid up to a size of 1 AU simultaneously. The magnetic field at the inner boundary is specified by the observational data. In order to obtain the supersonic solar wind speed, parameterized source functions are introduced into the momentum and energy equations. These source functions decay exponentially in altitude as widely used in previous studies. The absolute values of the source functions are controlled so as to reflect the topology of the coronal magnetic field. They are increased inside the magnetic flux tube with subradial expansion and reduced inside the magnetic flux tube with overradial expansion. This adjustment aims to reproduce the variation of the solar wind speed according to the coronal magnetic structure. The simulation simultaneously reproduces the plasma‐exit structure, the high‐ and low‐temperature regions, the open and closed magnetic field regions in the corona, the fast and slow solar wind, and the sector structure in interplanetary space. It is confirmed from the comparison with observations that the MHD model successfully reproduces many features of both the fine solar coronal structure and the global solar wind structure.