On the Evolution of Coronal Mass Ejections in the Interplanetary Medium

Abstract

Two coronal mass ejections (CMEs) are presented which were tracked through the LASCO field of view (FOV ) within 30 R and later as interplanetary CMEs (ICMEs) through the SMEI FOV from 80 to 150 R . They were also associated with erupting filaments observed by EIT, providing information on trajectory of propagation. This allowed three-dimensional reconstructions of CME /ICME geometry, along with corrected (not sky plane projected) measurements of distance-time (DT) plots for each event to $0.5 AU. An investigation of morphology was conducted. The results suggest that fine structures of the CMEs are eroded by the solar wind, and curvature becomes more sharply convex outward, suggesting that ICME footpoints remain fixed to the Sun even at 0.5 AU. We also present two models describing the evolution of CMEs/ICMEs at large distances from the Sun (far from the launch mechanism and effects of gravity and solar pressure) and consider two drag models: aerodynamic drag and snowplow. There was little difference between these, and their DT profiles matched well with the SMEI data for event 1. Event 2 showed a net acceleration between the LASCO and SMEI FOVs and we could match the data for this event well by introducing a driving Lorentz force. ICME mass almost doubled as a result of swept-up solar wind material from the snowplow model. Finally, we compared the geometry and kinematics of the ICME with that produced by the HAFv2 model and found that the model reasonably matched the geometry, but overestimated the ICME speed. Subject headingg s: interplanetary medium -solar-terrestrial relations -solar windSun: coronal mass ejections (CMEs)

Measuring an Eruptive Prominence at Large Distances From the Sun. Ii. Approaching 1 Au

“…The cause of the increasing mass of the CME is generally accepted as solar wind material that is acreted ahead of the CME driver (its flux rope) as it expands through the heliosphere (e.g., Lugaz et al 2005;Tappin 2006;Howard et al 2007;DeForest et al 2013), as the CME measurements, including those made in the present study, typically include the so-called "sheath" component. This is evidenced by the substantial increase in the density of just the flank of the CME shown in Figure 2.…”

“…where R is in AU, cos cos cos a = L F, and Λ and Φ are the latitude and longitude of the feature relative to the observer (Howard et al 2007). Taking the angular range spanned by the prominence (S16E42-S25E57 relative to the Earth) provides upper and lower limits to the values of R fp ; this provides the uncertainties in the Fixed-ϕ distances in Figures 5(b), 6, and 7.…”

Dynamics of coronal mass ejections in the interplanetary medium

“…The acceleration in the interplanetary medium of CMEs is well-established (Gopalswamy et al 2000(Gopalswamy et al , 2001Manoharan et al 2001;Manoharan 2006;Howard 2007). This acceleration has been explained by an increase of the ICME mass (snowplough model Tappin 2006) or due to Lorentz force (Chen 1996;Howard 2007), although it is more common to attribute this acceleration to drag forces (Vršnak 2001;Cargill 2004).…”

“…This acceleration has been explained by an increase of the ICME mass (snowplough model Tappin 2006) or due to Lorentz force (Chen 1996;Howard 2007), although it is more common to attribute this acceleration to drag forces (Vršnak 2001;Cargill 2004). However, the exact form, the magnitude of the related coefficients and the dependence of this drag force with the CME or SW parameters are still unknown.…”

“…Although, the Lorentz force is the most important at low heights then the drag becomes predominant after ∼30 R (Vršnak et al 2006). Recently, to explain IPS and white light observations (SMEI), Howard (2007) has suggested that the drag force overcome the Lorentz force . ICME speed versus distance for the four models analyzed in this work.…”