Radial Flow Pattern of a Slow CME

TL;DR

This paper introduces a new method to analyze the detailed radial mass transport within slow CMEs, providing more accurate estimates of their kinematics and energy, and challenging previous assumptions about net forces and mass pile-up.

Contribution

The paper presents a novel technique for analyzing CME kinematics that captures internal radial flow and refines energy estimates, improving upon traditional methods.

Findings

Radial flow speeds inside the CME are nearly constant between 2 and 15 R_S.

No evidence of net radial forces or mass pile-up within the analyzed range.

Traditional energy estimates may overstate the CME's kinetic and potential energy.

Abstract

Height-time plots of the leading edge of coronal mass ejections (CME) have often been used to study CME kinematics. We propose a new method to analyze the CME kinematics in more detail by determining the radial mass transport process throughout the entire CME. Thus our method is able to estimate not only the speed of the CME front but also the radial flow speed inside the CME. We have applied the method to a slow CME with an average leading edge speed about 480 km s$^{-1}$. In the Lagrangian frame, the speed of the individual CME mass elements stay almost constant within 2 and 15 R$_S$, the range over which we analyzed the CME. Hence we have no evidence of net radial forces acting on parts of the CME in this range nor of a pile-up of mass ahead of the CME. We find evidence that the leading edge trajectory obtained by tie-pointing may gradually lag behind the Lagrangian front-side trajectories derived from our analysis. Our results also allow a much more precise estimate of the CME energy. Compared with conventional estimates using the CME total mass and leading-edge motion, we find that the latter may overestimate the kinetic energy and the gravitational potential energy.