Propagation of an Earth-directed coronal mass ejection in three dimensions

TL;DR

This study introduces a new 3D reconstruction technique for CMEs, revealing their deflected trajectories and the influence of solar wind drag, leading to accurate predictions of their arrival at Earth.

Contribution

We developed an elliptical tie-pointing method for full 3D CME reconstruction, improving understanding of CME propagation and enabling precise space weather forecasting.

Findings

CME trajectories are significantly deflected at high latitudes.

CME angular width increases with distance from the Sun.

Solar wind aerodynamic drag governs CME motion beyond 7 solar radii.

Abstract

Solar coronal mass ejections (CMEs) are the most significant drivers of adverse space weather at Earth, but the physics governing their propagation through the heliosphere is not well understood. While stereoscopic imaging of CMEs with the Solar Terrestrial Relations Observatory (STEREO) has provided some insight into their three-dimensional (3D) propagation, the mechanisms governing their evolution remain unclear due to difficulties in reconstructing their true 3D structure. Here we use a new elliptical tie-pointing technique to reconstruct a full CME front in 3D, enabling us to quantify its deflected trajectory from high latitudes along the ecliptic, and measure its increasing angular width and propagation from 2-46 solar radii (approximately 0.2 AU). Beyond 7 solar radii, we show that its motion is determined by an aerodynamic drag in the solar wind and, using our reconstruction as input for a 3D magnetohydrodynamic simulation, we determine an accurate arrival time at the Lagrangian L1 point near Earth.