[P-EM18] [EE] Origin of Earth-affecting Coronal Mass Ejections

[PEM18-08] Magnetic Source Region Characteristics Influencing the Coronal Velocity of Solar Eruptions

*Bernhard Kliem¹, Georgios Chintzoglou², Tibor Torok³, Jie Zhang⁴, Cooper Downs³ (1.Institute of Physics and Astronomy, University of Potsdam, Germany, 2.LMSAL, Palo Alto, USA, 3.Predictive Science Inc., San Diego, CA, USA, 4.Department of Physics and Astronomy, George Mason University, Fairfax, VA, USA)

The velocity of coronal mass ejections (CMEs) is one of the primary parameters determining their potential geoeffectiveness. A great majority of very fast CMEs receive their main acceleration already in the corona. We study the magnetic source region structure for a complete sample of 15 very fast CMEs (v > 1500 km/s) during 2000--2006, originating within 30 deg from central meridian. We find a correlation between CME speed and the decay index profile of the coronal field estimated by a PFSS extrapolation. The correlation is considerably weaker for a comparison sample in which slower CMEs are included. We also study how the decay index profile is related to the structure of the photospheric field distribution. This is complemented by a parametric simulation study of flux-rope eruptions using the analytic Titov-Demoulin active-region model for simple bipolar and quadrupolar source regions. The simulations provide simple relationships between the photospheric field distribution and the coronal decay index profile. Very fast, moderate-velocity, and even confined eruptions are found and the conditions for their occurrence quantified.
We acknowledge support by NSF and NASA's LWS program.