Coronal Mass Ejection Mass, Energy, and Force Estimates Using STEREO

TL;DR

This study uses STEREO observations to accurately estimate the mass, energy, and forces involved in a specific coronal mass ejection, revealing the transition from magnetic forces to solar wind drag as the main driver.

Contribution

It provides the first detailed 3-D estimates of CME mass, energy, and forces, clarifying the evolution of CME dynamics with distance from the Sun.

Findings

CME asymptotically reaches a mass of 3.4±1.0×10^15 g.

Kinetic energy increases from 6.3±3.7×10^29 erg to 4.2±2.5×10^30 erg.

Magnetic forces dominate below 7 R_sun, solar wind drag dominates beyond.

Abstract

Understanding coronal mass ejection (CME) energetics and dynamics has been a long-standing problem, and although previous observational estimates have been made, such studies have been hindered by large uncertainties in CME mass. Here, the two vantage points of the Solar Terrestrial Relations Observatory (STEREO) COR1 and COR2 coronagraphs were used to accurately estimate the mass of the 2008 December 12 CME. Acceleration estimates derived from the position of the CME front in 3-D were combined with the mass estimates to calculate the magnitude of the kinetic energy and driving force at different stages of the CME evolution. The CME asymptotically approaches a mass of 3.4\pm1.0x10^15 g beyond ~10 R_sun. The kinetic energy shows an initial rise towards 6.3\pm3.7x10^29 erg at ~3 R_sun, beyond which it rises steadily to 4.2\pm2.5x10^30 erg at ~18 R_sun. The dynamics are described by an early phase of strong acceleration, dominated by a force of peak magnitude of 3.4\pm2.2x10^14N at ~3 R_sun, after which a force of 3.8\pm5.4x10^13 N takes affect between ~7-18 R_sun. These results are consistent with magnetic (Lorentz) forces acting at heliocentric distances of <7 R_sun, while solar wind drag forces dominate at larger distances (>7 R_sun).