Würzburg 2018 – scientific programme
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EP: Fachverband Extraterrestrische Physik
EP 4: Sun and Heliosphere II - Dynamics (MHD, Particles)
EP 4.3: Talk
Wednesday, March 21, 2018, 11:30–11:45, BSZ - Pabel HS
Decay Index Profile and Coronal Mass Ejection Speed — •Bernhard Kliem1, Tibor Török2, Georgios Chintzoglou3, and Jie Zhang4 — 1Institute of Physics and Astronomy, University of Potsdam, Germany — 2Predictive Science Inc., San Diego, CA, USA — 3LMSAL, Palo Alto, CA, USA — 4George Mason University, 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−1) during 2000–2006, originating within 30∘ 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. They also help identifying source regions which are likely to produce slow CMEs only, thus improving the correlation for the remaining CME sample. Very fast, moderate-velocity, and even confined eruptions are found and the conditions for their occurrence quantified.