Relativistic Electron Forecast Model

1. Skill scores of REFM from 1997-1999 versus the mean (prediction efficiency), persistence, and recurrence. A score of 1.0 indicates perfect predictions with respect to the reference forecast. 1-3 day forecast using ACE solar wind data only • A forecast model has been developed to predict the daily fluence of relativistic (> 2 MeV) electrons in the magnetosphere at geostationary orbit based on measured or predicted solar wind speed. The model is derived from a linear prediction filter technique described by Baker et al., JGR, 1990. Our model is being run twice each day in two forecast modes. The first uses ACE Real Time Solar Wind data to create predictions with one, two, and three days of lead time. The second mode takes advantage of predicted solar wind values calculated from the Wang-Sheeley technique to extend the predicted electron fluence up to eight days in advance. The model outputs are currently available only through an internal SEC website, but are being validated for release to the public. In this presentation, we will describe the modeling technique and the results of the validation. It is found that while the solar wind speed correlates strongly with relativistic electron fluence, other processes also contribute importantly to the magnetospheric flux levels. To help account for these additional processes, our model adjusts the output of the linear prediction filter with a correction factor based on previously observed values. This improves the predictions considerably, and can also be used to quantify and investigate the effects of processes other than solar wind speed that control the electron flux levels. Abstract 30  Coefficient (i)  solar wind (i) 2-5 day forecast using Wang Sheeley output i = 1 • A linear prediction filter using solar wind speed as input generates a good “first forecast” of relativistic electrons, but additional physical processes are at work • Until these processes are identified, REFM utilizes a simple correction factor to improve performance • Using the correction factor, REFM provides forecasts that beat the mean, persistence, and recurrence • REFM’s raw linear filter predictions can be used as a research tool to help identify the additional physical processes that effect relativistic electron fluence • REFM is undergoing evaluation for release to the public via an SEC web page The solar wind directly drives the electron fluence much of the time, and a forecast based on the linear prediction filter often works well. But as seen in the first example, the linear prediction alone cannot account for sudden changes in the magnetosphere’s response. To improve the forecast’s performance statistics, we have included a correction factor. As shown, this allows the 1 Day forecast to quickly recover from sudden changes in the magnetosphere. raw forecast = forecast = raw forecast  correction factor Relativistic Electron Forecast Model Chris Smithtro and Terry Onsager NOAA Space Environment Center Example of an REFM Web Page Performance Statistics Main Points Demonstration of the Flux Correction Factor How REFM Works Summary Sudden change in electron fluence. Forecast does not respond. • Coefficients are created from historical data by solving a set of linear equations to minimize the prediction filter’s error (Levinson, J of Mathematics and Physics, 1947) • A summation over the filter interval (30 days) of average daily solar wind speed times the corresponding coefficient gives the raw forecast • In the normal mode, measured solar wind values from the ACE spacecraft are used to create a 1-3 day forecast • In the Wang Sheeley mode, predicted solar wind speed values supplement the measured ones to extend the forecast to 2-8 days • To account for additional physical processes, a correction factor is introduced. The factor is calculated by taking an average of the ratios of previous raw forecasts to the observed electron fluences. This permits the model to respond to physical changes in the magnetosphere and greatly improves the prediction efficiency 1 Day Forecast Without Correction With correction included, forecast responds quickly 1 Day Forecast With Correction