Global Sensitivity Analysis and Uncertainty Quantification for Background Solar Wind Using the Alfvén Wave Solar Atmosphere Model. Issue 1 (17th January 2023)

• Record Type: Journal Article
• Authors: Jivani, Aniket; Sachdeva, Nishtha; Huang, Zhenguang; Chen, Yang; van der Holst, Bart; Manchester, Ward; Iong, Daniel; Chen, Hongfan; Zou, Shasha; Huan, Xun; Toth, Gabor
• Is Part Of: Space weather. Volume 21:Issue 1(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-17
• Subjects: uncertainty quantification -- global sensitivity analysis -- space weather -- solar wind; Space environment -- Periodicals; 551.509992
• DOI: 10.1029/2022SW003262
• Languages: English
• ISSNs: 1542-7390

Abstract

Abstract: Modeling the impact of space weather events such as coronal mass ejections (CMEs) is crucial to protecting critical infrastructure. The Space Weather Modeling Framework is a state‐of‐the‐art framework that offers full Sun‐to‐Earth simulations by computing the background solar wind, CME propagation, and magnetospheric impact. However, reliable long‐term predictions of CME events require uncertainty quantification (UQ) and data assimilation. We take the first steps by performing global sensitivity analysis (GSA) and UQ for background solar wind simulations produced by the Alfvén Wave Solar atmosphere Model (AWSoM) for two Carrington rotations: CR2152 (solar maximum) and CR2208 (solar minimum). We conduct GSA by computing Sobol' indices that quantify contributions from model parameter uncertainty to the variance of solar wind speed and density at 1 au, both crucial quantities for CME propagation and strength. Sobol' indices also allow us to rank and retain only the most important parameters, which aids in the construction of smaller ensembles for the reduced‐dimension parameter space. We present an efficient procedure for computing the Sobol' indices using polynomial chaos expansion surrogates and space‐filling designs. The PCEs further enable inexpensive forward UQ. Overall, we identify three important model parameters: the multiplicative factor applied to the magnetogram, Poynting flux per magnetic field strength constant used at the inner boundary, and the coefficient of the perpendicular correlation length in the turbulent cascade model in AWSoM. Plain Language Summary: Space weather events such as those driven by coronal mass ejections (CMEs) can result in severe geomagnetic storms that impact critical infrastructure. Accurate long‐term forecasts are therefore needed together with uncertainty quantification. In this work, we calculate uncertainty and perform sensitivity analysis for the background solar wind that has a major impact on the accuracy of the overall CME simulation. Since these models have many parameters that carry uncertainty, sensitivity analysis allows us to identify the most important ones. Key Points: We perform global sensitivity analysis for background solar wind simulations of the Alfvén Wave Solar atmosphere Model We identify and retain only the most important uncertain parameters from the sensitivity analysis results We carry out the analysis for examples of both solar maximum and solar minimum conditions