Investigation of the Forces that Govern the Three-Dimensional Propagation and Expansion of Coronal Mass Ejections from Sun to Earth

TL;DR

This study analyzes nine CMEs from Sun to Earth using remote sensing and in situ data, comparing models and observations to understand propagation forces and improve prediction accuracy.

Contribution

It is the largest multi-viewpoint study of Earth-impacting CMEs, applying models to compare remote sensing and in situ data for better understanding of CME dynamics.

Findings

Flux rope model best matches observations

Significant errors remain in predicted arrival times and impact velocities

Limited agreement between remote sensing and in situ size and orientation estimates

Abstract

In this study, we analyze nine CMEs from the Sun to Earth as observed in both the remote sensing and in situ data sets. To date, this is the largest study of Earth impacting CMEs using the multi-view point remote sensing and in situ data. However, the remote sensing and in situ data of the same CME cannot be directly compared. Thus, we use several models to parameterize the two data sets. With the model results, we are able to compare the arrival time, Earth impact speed, internal magnetic field, size and orientation as derived from the remote sensing and in situ methods. From the derived kinematics, we compare the predicted arrival times and impact velocities with the in situ data. We find that even with nearly continuous observations and the best available model of the CME structure, there is still a significant error in the predicted values. We estimate the various forces acting on the CME as predicted by three theoretical models of CME propagation and expansion and compare these results with the observational results. We find that the flux rope model of Chen (1989) provides the best agreement with the observations. With the flux rope model, we are able to predict the internal magnetic field of the CME near Earth from the remote sensing data to an order of magnitude. Finally, we compare the size and orientation of the CMEs as predicted from the remote sensing and in situ data. We find very little agreement between the values derived from the two data sets.