On the Relationship Between Coronal Magnetic Decay Index and CME Speed

Abstract

Numerical simulations suggest that kink and torus instabilities are two potential contributors to the initiation and prorogation of eruptive events. A magnetic parameter named decay index (i.e., the coronal magnetic gradient of the overlying fields above the eruptive flux ropes) could play an important role in controlling kinematics of eruptions. Previous studies have identified a threshold range of the decay index that distinguishes between eruptive and confined configurations. Here we advance the study by investigating if there is a clear correlation between the decay index and CME speed. 38 CMEs associated with filament eruptions and/or two-ribbon flares are selected using the Halpha data from the Global Halpha Network. The filaments and flare ribbons observed in Halpha associated with the CMEs help to locate the magnetic polarity inversion line, along which the decay index is calculated based on the potential field extrapolation using MDI magnetograms as boundary conditions. The speeds of CMEs are obtained from the LASCO C2 CME catalog available online. We find that the mean decay index increases with CME speed for those CMEs with a speed below 1000 km/s, and stays flat around 2.2 for the CMEs with higher speeds. In addition, we present a case study of a partial filament eruption, in which the decay indexes show different values above the erupted/non-erupted part.

ApJ, accepted

References in corpus (6)

• Torus instability
• Ideal kink instability of a magnetic loop equilibrium
• Criteria for Flux Rope Eruption: Non Equilibrium versus Torus Instability
• Numerical simulations of fast and slow coronal mass ejections
• Observations and modeling of the early acceleration phase of erupting filaments involved in coronal mass ejections
• Motions of Hard X-ray Sources During an Asymmetric Eruption

Cited by in corpus (15)

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• Statistical Analysis of Torus and Kink Instabilities in Solar Eruptions
• Critical Height of the Torus Instability in Two-Ribbon Solar Flares
• Solar Magnetic Flux Ropes
• Unwinding motion of a twisted active-region filament
• Filament eruption on 2010 October 21 from three viewpoints
• Sympathetic Solar Filament Eruptions on 2015 March 15
• Kink instability evidenced by analyzing the leg rotation of a filament
• Investigating width distribution of slow and fast CMEs in solar cycles 23 and 24
• The Roles of Reconnected Flux and Overlying Fields in CME Speeds
• Critical decay index for eruptions of 'short' filaments
• Solar Eruption and Local Magnetic Parameters
• The Kinematical Behavior of Solar Eruptive Filaments Affected by the Poloidal Magnetic Field
• Investigation of a confined C-class flare in an arch filament system close to a regular sunspot
• Data-constrained Magnetohydrodynamic Simulation of a Long Duration Eruptive Flare