# CME dynamics using STEREO & LASCO observations: the relative importance of Lorentz forces and solar wind drag

## TL;DR

This study quantifies the relative effects of Lorentz forces and solar wind drag on CME propagation, revealing that Lorentz forces dominate early on but become negligible at different heights depending on CME speed.

## Contribution

It provides a detailed analysis of the height-dependent dominance of Lorentz forces versus drag in CME propagation using observational data.

## Key findings

- Lorentz forces peak between 1.65 and 2.45 Rsun for all CMEs.
- Fast CMEs experience negligible Lorentz forces by 3.5--4 Rsun.
- Slow CMEs retain significant Lorentz influence up to 12--50 Rsun.

## Abstract

We seek to quantify the relative contributions of Lorentz forces and aerodynamic drag on the propagation of solar coronal mass ejections (CMEs). We use Graduated Cylindrical Shell (GCS) model fits to a representative set of 38 CMEs observed with the SOHO and STEREO spacecraft. We find that the Lorentz forces generally peak between 1.65 and 2.45 Rsun for all CMEs. For fast CMEs, Lorentz forces become negligible in comparison to aerodynamic drag as early as 3.5--4 Rsun. For slow CMEs, however, they become negligible only by 12--50 Rsun. For these slow events, our results suggest that some of the magnetic flux might be expended in CME expansion or heating. In other words, not all of it contributes to directed propagation. Our results are expected to be important in building a physical model for understanding the Sun-Earth dynamics of CMEs.