Modeling observations of solar coronal mass ejections with heliospheric imagers verified with the Heliophysics System Observatory

Abstract

We present an advance toward accurately predicting the arrivals of coronal mass ejections (CMEs) at the terrestrial planets, including Earth. For the first time, we are able to assess a CME prediction model using data over two thirds of a solar cycle of observations with the Heliophysics System Observatory. We validate modeling results of 1337 CMEs observed with the Solar Terrestrial Relations Observatory (STEREO) heliospheric imagers (HI) (science data) from 8 years of observations by five in situ observing spacecraft. We use the self‐similar expansion model for CME fronts assuming 60° longitudinal width, constant speed, and constant propagation direction. With these assumptions we find that 23%–35% of all CMEs that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for one correct prediction, two to three false alarms would have been issued. In addition, we find that the prediction accuracy does not degrade with the HI longitudinal separation from Earth. Predicted arrival times are on average within 2.6 ± 16.6 h difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. We also discuss various factors that may improve the accuracy of space weather forecasting using wide‐angle heliospheric imager observations. These results form a first‐order approximated baseline of the prediction accuracy that is possible with HI and other methods used for data by an operational space weather mission at the Sun‐Earth L5 point.

Forecasting the Arrival Time of Coronal Mass Ejections: Analysis of the CCMC CME Scoreboard

“…Additionally, Heliospheric Imagers (HI), which allow the tracking of CMEs along the entire Sun‐Earth line (e.g., Davis et al, ). Möstl et al (), using HI images from STEREO A and a self‐similar expansion (SSEF) method, showed that for a set of 76 Earth impacting CMEs, the mean error in accuracy was 3 ± 16 hr. For a smaller data set, Wood et al () estimated the uncertainties in the arrival time of 28 well‐observed ICMEs (identified in the Wind in situ measurements and remote solar observations), concluding that the SD in arrival time was 11.7 hr, reducing to 6.3 hr by the time the ICME had reached 0.3 AU.…”

Coronal Magnetic Structure of Earthbound CMEs and In Situ Comparison

“…For those events that were not in LINKCAT, we tracked the ICME backward in time to the Sun assuming constant speed and radial propagation and used HI imagery to follow the CME in the heliosphere. At this stage, we utilized the HELCATS ARRival CATalogue (Möstl et al, ) that lists predicted arrivals of CMEs at various spacecraft and planets using the previously described STEREO/HI SSEF fitting technique.…”

“…One of the ICME catalogues used to compile LINKCAT, in particular for CMEs detected toward Earth, is the Wind ICME catalogue (https://wind.nasa.gov/ ICMEindex.php; Nieves-Chinchilla et al, 2018). For a validation of use of the aforementioned HI-based SSEF technique to predict CME arrivals, see Möstl et al (2017).…”

Observations of the Proton Aurora on Mars With SPICAM on Board Mars Express

“…In order to check for CMEs, we searched the SOHO LASCO CME catalogue for events happening 4 to 7 days before the date of the aurora (the time window was selected in order to account for CME travel times to Mars considering typical CME velocities) and directed toward the location of Mars. For the events after 2007, we also checked the HELCATS ARRCAT catalogue (Möstl et al, 2017), which contains predicted arrivals of Figure 1. Lyman-α intensity profile plotted versus the tangent point altitude for an auroral (blue, Orbit 1426/1 egress) and a nonauroral case (black, Orbit 1414/2 egress).…”