Forecasting High-Speed Solar Wind Streams from Solar Images

TL;DR

This paper presents a simple polynomial regression model using solar EUV images and past solar wind data to forecast high-speed solar wind streams at Earth with reasonable accuracy, outperforming complex models.

Contribution

The study introduces a straightforward machine learning approach with distribution transformation that improves solar wind speed predictions over existing deep learning and simulation methods.

Findings

Achieved RMSE of 68.1 km/s for solar wind speed prediction.

Demonstrated model applicability to solar cycle 25 with RMSE of 80.3 km/s.

Identified that simple physical features dominate solar wind variation.

Abstract

The solar wind, a stream of charged particles originating from the Sun and transcending interplanetary space, poses risks to technology and astronauts. In this work, we develop a prediction model to forecast the solar wind speed at the Earth. We focuse on high-speed streams (HSSs) and their solar source regions, coronal holes. As input, we use the coronal hole area, extracted from solar extreme ultraviolet (EUV) images and mapped on a fixed grid, as well as the solar wind speed 27 days before. We use a polynomial regression model and a distribution transformation to predict the solar wind speed with a lead time of four days. Our forecast achieves a root mean square error (RMSE) of 68.1 km/s for the solar wind speed prediction and an RMSE of 76.8 km/s for the HSS peak velocity prediction for 2010 to 2019. We also demonstrate the applicability of our model to the current solar cycle 25 in an operational setting, resulting in an RMSE of 80.3 km/s and an HSS peak velocity RMSE of 92.2 km/s. The study shows that a small number of physical features explains most of the solar wind variation, and that focusing on these features with simple machine learning algorithms even outperforms current approaches based on deep neural networks and MHD simulations. In addition, we explain why the typically used loss function, the mean squared error, systematically underestimates the HSS peak velocities, aggravates operational space weather forecasts, and how a distribution transformation can resolve this issue.