X-CME: From In Situ Flux-Rope Reconstruction to CME Propagation Forecasting

TL;DR

X-CME is a new framework that combines in situ flux-rope reconstructions with physics-based propagation models to improve CME arrival time forecasts at Earth and Mars, reducing errors to a few hours.

Contribution

The paper introduces X-CME, a novel integrated approach linking magnetic reconstructions with a propagation model for better CME forecasting.

Findings

Successfully applied to two spacecraft-observed events.

Predicted CME arrival times with 2-4 hours error.

Accurately distinguished between central and glancing CME encounters.

Abstract

Accurate forecasts of Coronal Mass Ejection (CME) arrival times and impact geometry remain a major challenge for space-weather operations. Coronagraph-based techniques typically achieve mean absolute errors of order ten hours, while in situ measurements at L1 provide excellent magnetic-field information but only tens of minutes of warning. In this work we introduce X-CME, a framework that links in situ flux-rope reconstructions at intermediate heliocentric distances with a physics-based CME propagation model. The internal magnetic structure is obtained with an elliptical cylindrical, radial poloidal flux-rope model and embedded into a tapered torus CME geometry. The subsequent propagation is computed by solving a drag-based equation of motion in a Parker solar-wind background, including gravitational deceleration, self-similar expansion of the cross section, and an explicit calculation of the CME wetted area and swept area in the ecliptic plane. We apply X-CME to two events observed by the Parker Solar Probe and Solar Orbiter spacecraft, respectively, and propagate the reconstructed structures to Earth and Mars. For both cases, the model reproduces the observed in situ signatures at L1 and predicts the CME arrival time at Earth with errors of a few hours (typically about 2-4 hours), while correctly distinguishing between central encounters and glancing blows. These results demonstrate that combining intermediate-distance magnetic reconstructions with a geometrically consistent propagation scheme can substantially improve CME arrival-time forecasts and impact assessment in the inner heliosphere.