Validating Solar Wind Prediction Using the Current Sheet Source Surface Model

Abstract

We have carried out a comparative study of the predicted solar wind based on the flux tube expansion factor computed using the current sheet source surface (CSSS) model and the potential field source surface (PFSS) model, with the aim of determining whether the CSSS model represents the solar wind sources better than the PFSS model. For this, we obtained the root mean square errors (RMSEs) and the correlation coefficients between the observed solar wind speed and that predicted by the models, the ratio of RMSEs between the two models, and a skill score. On average, the CSSS predictions are more accurate than the PFSS predictions by a factor of 1.6, taking RMSE as the metric of accuracy. The RMSEs increased as the solar cycle progressed toward maximum, indicating the difficulty in modeling the corona as the global field becomes more complex. We also compared the WSA/ENLIL predictions for a few Carrington rotations; the Wang-Sheeley-Arge (WSA) model makes use of the PFSS extrapolations to model the wind source. We found that the average value of RMSE ratio between the CSSS and the WSA/ENLIL predictions was about 1.9, implying that the CSSS predictions are nearly twice better than the WSA/ENLIL predictions, despite the simplicity of the CSSS model compared to ENLIL. We conclude, based on the present analysis, that the CSSS model is a valid proxy for solar wind measurements and that it improves upon existing commonly used methods of wind prediction or proxy analysis.

Observations of the 2019 April 4 Solar Energetic Particle Event at the Parker Solar Probe

“…At this time, Earth was located near 60 • , so the AR was about 38 • over the east limb from Earth, nearly 3 days away from making an appearance in near-Earth-based magnetic imagers that could produce photospheric synoptic maps. Thus, tracing the field back to the photosphere using these maps with models such as the Current Sheet Source Surface (CSSS) model (Zhao & Hoeksema 1995;Poduval & Zhao 2014) is prone to larger-than-usual uncertainties, but attempts are in progress. Online synoptic maps from the Global Oscillation Network Group (GONG; https://gong2.nso.edu/archive/patch.pl) of the magnetic connectivity between the ecliptic and photosphere using the Potential Field Source Surface (PFSS; Wang & Sheeley (1992)) model show conflicting results between Carrington rotations 2215 (2019 March 12 to April 8) and 2216 (April 8 to May 5).…”

Validation for solar wind prediction at Earth: Comparison of coronal and heliospheric models installed at the CCMC

“…The difference is possibly because NSO‐IPS‐Tomography uses the daily updated magnetograms and CSSS model, while NSO‐WSA‐Enlil uses the CR synoptic maps and PFSS model. The main difference between the CSSS and PFSS models is that the former includes the effects of horizontal and sheet currents existing in the real corona [e.g., Poduval and Zhao , , and references therein]. From the comparison, we can only conclude there is no superior one between the two models and the performance depends on CR.…”

Origins of the Ambient Solar Wind: Implications for Space Weather

“…Many of these methods, along with their alphabet soup of acronyms, have been reviewed comprehensively by Sun (2012). One noteworthy technique is the so-called current-sheet sourcesurface (CSSS) model, which adds some complexity by inserting another spherical surface between the Sun and the source surface (Zhao and Hoeksema 1995), but also may provide improvement to solar wind stream prediction (Poduval and Zhao 2014).…”