Quoted from: https://ccmc.gsfc.nasa.gov/models/modelinfo.php?model=SWMF%20AWSoM%20R

Model Description
SWMF AWSoM_R (Alfven Wave Solar Atmosphere model), has been installed at the CCMC, with the following options available to the users:

• AWSoM_R (steady state ambient) version using full rotation magnetograms is available for CCMC Runs on Request users.
• AWSoM_R (time dependent) Real Time run repository
• AWSoM_R (time dependent) + CME + EEGGL(Eruptive Event Generator, Gibson and Low) with the options to choose Full Rotation Synoptic maps or QuickReduce Synoptic maps will be available for CCMC Runs on Request users soon.

To view descriptions of EEGGL and GL (Gibson and Low) Flux Rope CME model see the following links:

• Eruptive Event Generator (Gibson and Low) - EEGGL
• Gibson-Low flux rope CME model

SWMF AWSoM_R model description

The Alfven-Wave driven sOlar wind Model (AWSoM) is part of the Space Weather Modeling Framework (SWMF). The SWMF has been developed by the Center for Space Environment Modeling (CSEM) team led by Tamas Gombosi at the University of Michigan (Toth et al. 2012). AWSOM uses the solar corona (SC) and inner heliosphere (IH) components of the SWMF. Both the SC and IH models are based on the BATS-R-US MHD code, which is a 3-dimensional block-adaptive code.

The AWSOM model can produce a solution of the ambient corona for a Carrington Rotation selected by the user. The computational domain starts from the top of the chromosphere, and includes the transition region, corona, and the inner heliosphere. This model solves the magnetohydrodynamic (MHD) equations with separate ion and electron temperatures and two equations for the Alfven wave turbulent energy densities propagating along and counter the magnetic field lines. The Alfvenic Poynting flux is assumed to be emanating from the chromosphere. The interaction of the wave field with the MHD plasma serves to both accelerate and heat the plasma. This model includes Spitzer electron heat conduction and radiative cooling (calculated using a CHIANTI table) in the lower corona. Coronal heating is achieved through observationally motivated turbulent Alfven wave dissipation. This mechanism uses a dissipation length, Lperp, which depends on the magnetic field magnitude. It is assumed that some of the wave energy propagating away from the Sun is reflected backwards due to inhomogeneities. The detailed reflection process is now directly simulated. Before 2014, Jan 30, a reflection coefficient, Cref, was used as an input parameter (see restrictions below). Heating due to the interaction of outward propagating and reflected waves is dominant in the coronal holes. In closed magnetic field line regions, counter propagating wave dissipation is dominant. By the date of the document, the most complete description of the model is provided in Sokolov et al (2013). The detailed description of the wave reflection is provided in Van Der Holst et al (2014).

The inner boundary conditions for the magnetic field are taken from a synoptic magnetogram (GONG/MDI). The temperature and density at the top of the chromosphere are set to be uniform at 50,000 [K] and 2x10¹¹ [cm-3], respectively. The radial velocity is set to zero. The outer boundary conditions are superfast outflow.

The initial conditions for the solar wind plasma are based on a Parker solution. The initial magnetic field is based on the Potential Field Source Surface Model obtained from the synoptic magnetogram.

The coronal code iterates for (60,000) steps until the solution has settled into a steady state. (The number of steps may change as we study the number of iterations that the solar coronal component needs to converge). Some cases may not reach equilibrium - the user should check the convergence plots provided with the output to confirm convergence to an equilibrium, and provide feedback to model developers. Then the heliospheric component evolves a solution consistent with the coronal model for 5,000 iterations.

Automatic refinement is performed several times to increase the grid resolution within the current sheet. If the model is used with CME, an extra refinement is performed for the active region from which the CME originates.

Computational Grid
The coronal component uses a non-uniform spherical grid extending from the chrompshere to 24 solar radii in the radial direction. The grid is stretched in the radial direction so that the transition region is resolved, with a minimal cell size of 0.001 solar radii in the radial direction. The total number of grid cells is ~2-3 million. The heliospheric component uses a Cartesian grid that extends from 20 solar radii to (TBD) solar radii. There is some overlap of the SC and IH grids at their interface to support the coupling of the solar corona and inner heliosphere components. Both grids employ adaptive mesh refinement to increase the resolution near the heliospheric current sheet.

Model Input
GONG synoptic maps (magnetograms) and CME parameters derived from EEGGL tool

Model Output
Outputs include the MHD plasma parameters (atomic mass unit density N, pressure P, velocity V_x, V_y, V_z, magnetic field B_x, B_y, B_z, electric currents, J_x, J_y, J_z, Alfven wave energy densities I01, I02 and dissipation rates GammaLperp, GammaCref. Description of derived variables can be found here.

The above quantities are available in full 3D, in 2D slices, as well as along satellite orbits.

COMING SOON: The model can produce synthetic images of the Sun's atmosphere, including EUV, X-ray and white-light images.

For a detailed description of these components in the SWMF and the 3D codes used:

• I. Sokolov et al., Magnetohydrodynamic Waves and Coronal Heating: Unifying Empirical and MHD Turbulence Models, Astrophysical Journal, 764, 23 (2013)
• G. Toth et al, Journal of Computational Physics, Volume 231, 870 (2012)
• G. Toth, B. van der Holst & Z. Huang, Obtaining Potential Field Solution with Spherical Harmonics and Finite Differences, Astrophysical Journal, 732, 102, (2011)

References and relevant publications

• R. Oran, B. van der Holst, E. Landi, M. Jin, I. V. Sokolov, and T. I. Gombosi, A Global Wave-Driven Magnetohydrodynamic Solar Model with a Unified Treatment of Open and Closed Magnetic Field Topologies, Astrophysical Journal, Vol. 778, Page 176, 2013, http://dx.doi.org/10.1088/0004-637X/778/2/176
• B. van der Holst, I. V. Sokolov, X. Meng, M. Jin, W. B. Manchester, IV, G. Toth, and T. I. Gombosi, Alfven Wave Solar Model AWSoM: Coronal Heating,?Astrophysical Journal, Vol. 782, Page 81, 2014, http://dx.doi.org/10.1088/0004-637X/782/2/81
• I. V. Sokolov, B. van der Holst, W. B. Manchester, D. Ozturk, J. Szente, A. Taktakishvili, G. Toth, M. Jin, and T. I. Gombosi, Threaded-Field-Lines Model for the Low Solar Corona Powered by Alfven Wave Turbulence, 2016, 2016arXiv160904379S

Relevant links

• Solar Wind Model in the SWMF (presentation by I. Sokolov)

   

• Public SWMF AWSoM_R Real Time Repository

   

• EEGGL (Eruptive Event Generator - Gibson and Low) | Basic instructions on EEGGL use

   

• Detailed EEGGL instructions (PDF)

   

• Stereo CAT

   

• SWMF AWSOM (previous. version of SWMF Solar model, also available at the CCMC)

CCMC Contact(s)
Aleksandre Taktakishvili
301-286-4521

Developer Contact(s)
Igor Sokolov