Models and Coupling

The CISM comprehensive model will be built from existing state-of-the-art codes. The core codes we will be using are:

The MAS (Magnetohydrodynamics outside A Sphere), which solves the time-dependent, resistive MHD equations in spherical coordinates, models the large-scale behavior of the solar corona and inner heliosphere In its present implementation as a component of the coupled CISM models, MAS is used to model the region of space from the solar surface to 20-50 solar radii. There are two versions of MAS, a mature (~14 years) serial version optimized for vector processors, and a parallel version utilizing MPI (~2 years). The MPI version is operational for many problems but porting of features from the serial code is still ongoing. MAS MPI is used in state-of-the-art calculations such as CME eruptions from active regions. It allows non-uniform meshes in all three dimensions, facilitating the study of localized features in the context of the global corona. Eventually, MAS MPI will replace MAS serial.

**References:**

Linker, J. A., Mikic, Z., Lionello, R., Riley, P., Amari, T., Odstrcil, D., Physics of Plasmas, Vol. 10, No. 5, p.1971, 2003

Lionello, R., Linker, J. A., Mikic, Z., Astrophysical Journal, Vol. 546, Issue 1, p. 542-551. Jan 2001

Mikic, Z., Linker, J. A., Schnack, D. D., Lionello, R., Tarditi, A., Physics of Plasmas, Vol. 6, Issue 5, 1999

Riley, P., Linker, J. A., Mikic, Z., Odstrcil, D., Zurbuchen, T. H., Lario, D., Lepping, R. P., Journal of Geophysical Research, Vol.108, Issue A7, p. SSH 2-1, CiteID 1272, DOI 10.1029/2002JA009760, 2003

The ENLIL (Sumerian god of wind) code is a numerical model for simulations of the ambient corotating solar wind as well as transient disturbances throughout the inner and mid heliosphere. The model is based on ideal magnetohydrodynamic (MHD) equations with the ratio of specific heats, ?, usually chosen to be 1.5. Two additional continuity equations may be used for tracing the injected material and the interplanetary magnetic field polarity. The inner heliospheric boundary is at the super-critical flow region (usually 18-30 R$), thereby simplifying the numerical solution. The inner boundary conditions are prescribed values of all MHD variables as functions of time and all structures rotate along the inner boundary with an azimuthal velocity corresponding to the solar rotation. After an ambient state has been reached, transient disturbances can be specified as time dependent values on the inner boundary. These transient boundary values can be specified from: (1) analytic formulae); (2) empirical models; (3) results from numerical coronal models); or (4) derived from observations in certain applications (e.g., radial spacecraft alignment or geospace applications).

**References:**

Odstrcil, D., Modeling 3-D solar wind structure, Adv. Space Res., 32(4)}, 497-506, 2003.

Odstrcil, D., P. Riley, and X. P. Zhao, Numerical simulation of the 12 May 1997 interplanetary CME event, J. Geophys. Res., 109, doi:10.1029/2003JA010135, 2004.

Odstrcil, D., V. J. Pizzo, and C. N. Arge, Propagation of the 12 May 1997 interplanetary CME in evolving solar wind structures, J. Geophys. Res., 110, doi:10.1029/2004JA010745, 2005.

The LFM Code is an integrated simulation model for the global magnetosphere-ionosphere system. The heart of the model is a time-dependent, ideal MHD calculation of the state of the magnetosphere. This magnetospheric model is tightly coupled to a realistic model for the polar ionospheres and is driven by solar wind plasma and magnetic field data upwind of the calculation domain. While lacking important physical processes in both the magnetosphere and ionosphere, the model is the simplest, self-consistent first principles model possible. With current computational capabilities, it is also the only type of model capable of providing reasonable quantitative accuracy in simulating the magnetosphere-ionosphere system.

**References:**

Fedder, J.A., S.P. Slinker, J.G. Lyon, and R.D. Elphinstone, Global numerical simulation of the growth phase and the expansion onset for substorm observed by Viking, J. Geophys. Res.,100 , 19,083, 1995.

Lyon, J.G., J.A. Fedder, and C.M. Mobarry, The Lyon-Fedder-Mobarry (LFM) Global MHD Magnetospheric Simulation Code, J. Atm. And Solar-Terrestrial Phys., 66, Issue 15-16, 1333-1350, 2004.

The TING model is a first-principles physical model of the thermosphere-ionosphere system. It solves self-consistently the thermospheric neutral momentum, energy, and continuity equations, and the ionospheric ion transportation, and plasma energy equations to obtain 3 dimensional distributions of neutral densities, temperatures, wind velocities and electron and ion densities and temperatures at each time step. It requires inputs (electric field and particle precipitation) at high latitudes to simulate the impact of the magnetosphere on the energetics and dynamics of the upper atmosphere. The current version of the TING model is based on the NCAR-TIGCM, with the additional capability of increased resolution in specified regions (a nested grid is included in the model).

**References:**

Wang, W., T. L. Killeen, A. G. Burns, and R. G. Roble, A high-resolution, three-dimensional, time dependent, nested grid model of the coupled thermosphere-ionosphere, J. Atmos. Solar-Terr. Phys., 61, 385-397, 1999.

Wang, W., M. Wiltberger, A. G. Burns, S. C. Solomon, T. L. Killeen, N. Maruyama, and J. G. Lyon, Initial results from the coupled magnetosphere ionosphere thermosphere model: thermosphere-ionosphere responses, Journal of Atmospheric and Solar-Terrestrial Physics, 66, 1425-1441, 2004

The Rice Convection Model (RCM) is an established physical model of the inner and middle magnetosphere that includes the coupling to the ionosphere. It uses a many-fluid formalism to describe adiabatically drifting isotropic particle distributions in a self-consistently computed electric field and specified magnetic field. The RCM represents the particles in terms of multiple fluids. Its equations and numerical methods have been specifically designed for accurate treatment of the inner magnetosphere, including the flow of electric currents along magnetic field lines to and from the conducting ionosphere. The RCM computes these currents and the associated electric fields self-consistently. It assumes perfectly conducting field lines and employs a pre-computed time-dependent magnetic field with associated induction electric fields.

**References:**

Toffoletto, F. R., S. Sazykin, R. W. Spiro and R. A. Wolf, Modeling the Inner Magnetosphere using the Rice Convection Model (review), Space Science Reviews, WISER special issue, 108, 175-196, 2003.

Wolf, R. A., R. W. Spiro, and F. J. Rich, Extension of the Rice Convection Model into the high-latitude ionosphere, J. Atm. Terrest. Phys., 53, 817-829, 1991.