Ensemble Modeling of CMEs Using the WSA–ENLIL+Cone Model

Abstract

Ensemble modeling of coronal mass ejections (CMEs) provides a probabilistic forecast of CME arrival time which includes an estimation of arrival time uncertainty from the spread and distribution of predictions and forecast confidence in the likelihood of CME arrival. The real-time ensemble modeling of CME propagation uses the Wang-Sheeley-Arge (WSA)-ENLIL+Cone model installed at the Community Coordinated Modeling Center (CCMC) and executed in real-time at the CCMC/Space Weather Research Center. The current implementation of this ensemble modeling method evaluates the sensitivity of WSA-ENLIL+Cone model simulations of CME propagation to initial CME parameters. We discuss the results of real-time ensemble simulations for a total of 35 CME events which occurred between January 2013 -July 2014. For the 17 events where the CME was predicted to arrive at Earth, the mean absolute arrival time prediction error was 12.3 hours, which is comparable to the errors reported in other studies. For predictions of CME arrival at Earth the correct rejection rate is 62%, the false-alarm rate is 38%, the correct alarm ratio is 77%, and false alarm ratio is 23%. The arrival time was within the range of the ensemble arrival predictions for 8 out of 17 events. The Brier Score for CME arrival predictions is 0.15 (where a score of 0 on a range of 0 to 1 is a perfect forecast), which indicates that on average, the predicted probability, or likelihood, of CME arrival is fairly accurate. The reliability of ensemble CME arrival predictions is heavily dependent on the initial distribution of CME input parameters (e.g. speed, direction, and width), particularly the median and spread. Preliminary analysis of the probabilistic forecasts suggests undervariability, indicating that these ensembles do not sample a wide enough spread in CME input parameters. Prediction errors can also arise from ambient model parameters, the accuracy of the solar wind background derived from coronal maps, or other model limitations. Finally, predictions of the K P geomagnetic index differ from observed values by less than one for 11 out of 17 of the ensembles and K P prediction errors computed from the mean predicted K P show a mean absolute error of 1.3.

Combining STEREO SECCHI COR2 and HI1 images for automatic CME front edge tracking

“…The chosen events propagate in the STEREO A COR2 and HI1 FOVs to the east of the Sun and were recorded in the period from January 1, 2008 to August 31, 2009. To obtain the reference propagation parameters, the COR2 set was manually inspected using a space weather analysis tool called StereoCAT (http://ccmc.gsfc.nasa.gov/ analysis/stereo/; Mays et al 2015). We used this tool only to obtain the reference PA and speed of each CME event in the COR2 set used for validation.…”

“…Extraction of the parameters from two vantage points (i.e., both spacecraft), however, makes reconstruction of a true CME propagation path in 3D space possible (Howard & Tappin 2008;Mierla et al 2008Mierla et al , 2010Boursier et al 2009;Colaninno & Vourlidas 2009;de Koning et al 2009; de Koning & Pizzo 2011). The reconstruction can be accomplished using a technique of geometric triangulation, such as that proposed by Liu et al (2010) and Mays et al (2015). Prior to using a geometric triangulation technique, one needs to determine the location of a CME front edge in each image in stacks from STEREO A and B.…”

“…For example, to analyze COR2 data, a Stereoscopic CME Analysis Tool (StereoCAT) (http:// ccmc.gsfc.nasa.gov/analysis/stereo/; Mays et al 2015) can be used. This tool requires a user to manually identify and trace a CME front edge in each image in a stack, and based on that, it automatically derives the parameters.…”

Possibilities and problems of Solar magnetic field observations for space weather forecast

“…По гелиошироте модель оперирует в диапазоне ±60°. Последней на момент написания обзора модификацией WSAEnlil является модель WSA-Enlil+Cone [Mays et al, 2015], которая дополнена возможностями предсказания условий взаимодействия с Землей КВМ, которые наблюдаются коронографами (в том числе с космических аппаратов STEREO) на расстояниях до 20 радиусов Солнца и геометрия распространения которых в межпланетном про-странстве аппроксимируется конусом. Пример работы комплекса программ WSA-Enlil+Cone пока-зан на рис.…”

“…Однако необходимо заметить, что, как бы ни бы-ли сложны и универсальны методы и модели про-гноза параметров космической погоды, 100%-й точ-ности прогнозов они обеспечить не в состоянии [Mays et al, 2015]. Одна из причин такого положе-ния заключается в достоверности самих исходных данных.…”