(Left) The location of STEREO A, B, Mercury, Venus and Earth are shown in an ecliptic plane type projection with field of view from the white light HI1 instruments on STEREO A and B indicated. STEREO A and B orbit the sun at 1 AU like Earth while the HUXt model calculates arrival time of CMEs at Earth. The HUXt model solution along Earth’s latitudinal plane is imbedded in this image for the ’best estimate’ run of a CME at 2012-09-01 08:46 UT. The orange line marks the boundary of the CME region as seen from STEREO A, as does a purple line from STEREO B. The shaded red and pink regions mark the HI1 fields-of-view for STEREO A and B. (Right) View of a CME (background-subtracted) image taken by HI1 on STEREO A at approximately same time as Left panel. The solid-red line marks the SSW consensus profile of the CME front, while the dashed lines mark the uncertainty in this profile. The dashed-green lines mark a 4-degree position angle band around the solar equatorial plane. Credit: Barnard et al., 2020, Figure 1 (left and center panels of original figure)
Source: AGU Advances

The Solar Stormwatch (SSW) project coordinates citizen scientists in tracking coronal mass ejection (CME) events observed in white light from the STEREO A and B spacecraft at different heliographic longitudes orbiting at 1 AU. The HI1 instruments, identical on both spacecraft, are white-light imagers that observe sunlight that has been Thomson scattered by solar wind electrons. Barnard et al. [2020] employ the HUXt numerical model, which uses these STEREO white light images as input, treats the solar wind as a 1-D incompressible fluid and solves for arrival time of the CME perturbation of the solar wind at Earth. Ensemble modeling of different determinations of the inner boundary condition improves the forecast arrival time of CME disturbances of the solar wind at Earth, an important driver of space weather. Radiation threats to spacecraft and astronauts, as well as ground induced currents which can shut down power grids, are examples of space weather effects produced by strong CMEs, wherein advanced warning of arrival time may allow mitigation.

Citation: Barnard, L., Owens, M., Scott, C., & de Koning, C. [2020]. Ensemble CME Modelling Constrained by Heliospheric Imager Observations. AGU Advances, 1, e2020AV000214. https://doi.org/10.1029/2020AV000214

—Mary Hudson, Editor, AGU Advances