Evaluating the Skill of Forecasts of the Near‐Earth Solar Wind Using a Space Weather Monitor at L5. Issue 7 (10th July 2018)

• Record Type: Journal Article
• Authors: Thomas, S. R.; Fazakerley, A.; Wicks, R. T.; Green, L.
• Is Part Of: Space weather. Volume 16:Issue 7(2018)
• Page Start: 814
• Page End: 828
• Publication Date: 2018-07-10
• Subjects: space weather -- solar wind -- forecasting -- solar physics -- Alfvén waves -- magnetic turbulence; Space environment -- Periodicals; 551.509992
• DOI: 10.1029/2018SW001821
• Languages: English
• ISSNs: 1542-7390

Abstract

Abstract: Forecasting space weather is an essential activity for increasing the resilience of modern technological infrastructure to hazards from the Sun. To provide an accurate forecast, space weather monitors positioned at L5 are proposed that carry in situ plasma detectors. Here we use data from the STEREO and ACE missions to investigate how well it is possible to predict the solar wind when there are two spacecraft located with the same longitudinal separation as from L5 to Earth. There are four intervals when this is the case: STEREO‐to‐STEREO both on the Earth's side and the far side of the Sun, STEREO‐B to ACE and ACE to STEREO‐A. We forecast the solar wind by mapping the observed solar wind at the first spacecraft to the second using a time delay calculated using the spacecraft's heliographic longitudinal separation and the difference in radial distance from the Sun, allowing for the solar wind speed. Using forecasting skill scores, we find that the predicted and observed solar wind data are, in general, in very good agreement with each of the four periods, including observed corotating interaction regions. However, there are some notable exceptions when corotating interaction regions have been missed by the forecast. The skill improves further for all time periods when removing coronal mass ejections, which cannot be predicted in this method. We suggest that an L5 monitor should be located at the same heliographic latitude as the Earth to optimize the forecasting ability of the monitor and to reduce the chance of missing important events. Plain Language Summary: A space weather monitor spacecraft has been proposed away from the Earth's viewing direction, which is likely to help improve the warning of solar events that could be heading towards Earth. In this study, we investigate whether such a spacecraft can improve our predictions of important physical values that are associated with the solar wind. To do this, we use times when two spacecraft have previously been in similar locations with respect to each other and map each value from one spacecraft to the other, making several important considerations relating to the spacecraft's motion and the movement of the plasma that they are embedded within. We have used "skill scores, " which are used to assess weather forecasts to quantify how well our forecast performs. We find that a spacecraft at this location predicts almost all important values better than relying on a spacecraft at L1. This means that a detector of these parameters is essential for when the mission is commissioned. Key Points: We quantify the ability to forecast solar wind parameters from one spacecraft to another, 60° apart in heliographic longitude We find good agreement in most parameters between the forecasted data from the first spacecraft to the observed data from the second Skill scores show that a solar wind forecast from L5 would perform better than using persistence from one solar rotation before