The collaborators here intend to develop and maintain a first-principles-based comprehensive numerical code, to be called the Comprehensive Corona and Heliosphere Model (CCHM). The CCHM will simulate the 3D time-dependent structure and dynamics of the slowly varying corona and the ambient solar wind, and it will be based on the Space Weather Modeling Framework, a flexible high-performance computational tool developed at the University of Michigan. Using the CCHM, the proposing team will expand available physics models, assist researchers in using new capabilities, validate individual models, and calculate prediction skill scores, in partnership with the Community Coordinated Modeling Center (CCMC), NOAA Space Environment Center (SEC), and the Solar-Heliospheric Community.
The main features of the CCHM model will be: (i) a 3D quantitative description of the large scale structure and properties of the corona and the heliosphere at any given instant in time; (ii) the incorporation of presently available and forthcoming line-of-sight photospheric magnetic field data, as well as vector magnetic field observations, as model input; (iii) the ability to initiate simple transients, as well as sophisticated magnetically-driven solar eruptions; (iv) predictions of time-dependent solar wind parameters and the energetic particle environment at a point or an object (Earth, Mars, spacecraft) in space; (v) sufficient modularity to incorporate routines containing new or more sophisticated physics; (vi) a user-friendly web portal to create, submit, monitor, and analyze model runs (including graphics) by the general research community; (vii) faster-than-real-time capability on reasonable computational resources, yielding the flexibility for quick-turn-around runs; (viii) the ability to run continuously in a 'pipeline mode' and to describe continuous topological changes of the solar magnetic field (as long as continuous data streams from Solar and Heliospheric Observatory/Michelson Doppler Imager (SoHO/MDI), Synoptic Optical Long-term Investigations of the Sun (SOLIS), and eventually Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) are available). The Principal Investigators intend to be active in evaluating and validating the CCHM throughout the lifetime of the project.
Space Weather is an important part of 21st century. Sudden emission of energetic ions reaching relativistic energies pose a threat to satellites and human activity in space around Earth. We believe that the largest, most dangerous solar energetic particle (SEP) events are produced by coronal mass ejections (CMEs). The high-speed CMEs drive a shock wave, which can accelerate charged particles to high energies. Though the basic principles of shock acceleration are known for decades, the precise mechanism of SEP events are still unclear since the CME and the shock wave form a complex and constantly evolving structure. SEP events exhibit great variability, some of the large CMEs prove to be ineffective accelerators, while others are efficient ones. The goal of the present project was to work out a mathematical scheme and numerical code which permits the description of complex, realistic structures. For this purpose, the equations governing the acceleration process have been cast in a new form, and the scheme traces field lines carried by fluid elements as they evolve around the moving and expanding CME. The constantly changing geometry is taken into account. The scheme employs the so-called focused transport equation, which retains the full pitch-angle distribution of energetic particles hence, by contrast with the diffusion approximation, remains valid for high anisotropic particle distribution as well as for low particle speed. Parallel with the numerical code, theoretical studies were conducted on the role of the topology of the magnetic field-line shock system. We find that these topological features can have profound effects on both large and small scales, and might account for the great variability of SEP events.
