WSA-Enlil-at-SWPC

WSA-Enlil is a large-scale, physics-based numerical model of the inner heliosphere used by NOAA's Space Weather Prediction Center (SWPC) to provide 1-4 day advance forecasts of solar wind structures and Earth-directed coronal mass ejections (CMEs) that can cause geomagnetic storms. The model combines two sub-models:

1. Wang-Sheeley-Arge (WSA): a semi-empirical near-Sun model that uses photospheric magnetic field observations (primarily from the GONG network) to generate global solar wind solutions in the solar corona.
2. Enlil: a 3-D magnetohydrodynamic (MHD) numerical model that simulates the propagation of solar wind and CMEs through the inner heliosphere.

• The accuracy of model outputs heavily depends on the quality of input magnetic maps and the characterization of CMEs.
• The WSA-Enlil model represents CMEs as cone-shaped structures, which may not fully capture the complex, asymmetric nature of real CMEs.
• The prediction horizon is limited by the spatial domain of the model and the inherent variability of the solar wind.
• CME parameters are approximations derived from coronagraph observations and may not reflect the full complexity of CME structures.
• Therefore, when interpreting model predictions, it is important to consider these input uncertainties and simplifications inherent in the modeling approach.

Photospheric magnetic field synoptic maps from the GONG network, combined over one solar rotation, providing input for WSA. CME parameters derived from coronagraph imagery, including timing, location, direction, and speed, characterize CMEs injected into the modeled solar wind.

Hourly and higher cadence predictions of solar wind plasma parameters (density, velocity, temperature) and magnetic field at multiple locations including Earth (L1) and spacecraft positions such as STEREO A. Outputs include 3-D solar wind structures, CME propagation, and time series of predicted solar wind conditions for forecast intervals typically around 3 to 5 days.

SWPC WSA-Enlil Version 1.0

• Date: December 13, 2011
• Deployment: Initial implementation on NCEP’s Central Computing System
• Components:
• WSA v2.2 (driven by GONG mrbqs synoptic maps)
• Enlil v2.6

• Date: May 28, 2019
• Deployment: NCEP’s Weather and Climate Operational Supercomputing System (WCOSS)
• Model Updates:
• Enlil v2.6 → v2.9e
• Ambient retuning: amb=a3b2 → amb=a8b1

• Date: December 9, 2019
• Deployment: WCOSS
• Model Updates:
• Planetary ephemerides extended through end of 2030

• Date: April 4, 2023
• Deployment: WCOSS2
• Model Updates:
• WSA v2.2 → WSA v5.4
• Implemented zeropoint-corrected GONG mrzqs synoptic maps
• Implemented run-on-demand capability for CME runs, retiring bi-hourly executions
• Adopted single (00Z) daily ambient run
• Changed data acquisition point from Earth to L1, replacing evo.earth.nc with evo.l1.nc