CORONAL MASS EJECTION MASS, ENERGY, AND FORCE ESTIMATES USING STEREO

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 three dimensions 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 {+-} 1.0 Multiplication-Sign 10{sup 15} g beyond {approx}10 R{sub Sun }. The kinetic energy shows an initial rise toward 6.3 {+-} 3.7 Multiplication-Sign 10{sup 29} erg at {approx}3 R{sub Sun }, beyond which it rises steadily to 4.2 {+-} 2.5 Multiplication-Sign 10{sup 30} erg at {approx}18 R{sub Sun }. The dynamics are described by an early phase of strong acceleration, dominated by a force of peak magnitude of 3.4 {+-} 2.2 Multiplication-Sign 10{sup 14} N at {approx}3 R{sub Sun }, after which a force of 3.8 {+-} 5.4 Multiplication-Sign 10{sup 13} N takes effect between {approx}7 and 18 R{sub Sun }. These results are consistent with magnetic (Lorentz) forces acting at heliocentric distances of {approx}<7 R{sub Sun }, while solar wind drag forces dominate at larger distances ({approx}>7 R{sub Sun }).