Volume 516, June-July 2010
|Number of page(s)||9|
|Published online||24 June 2010|
Investigating the driving mechanisms of coronal mass ejections
Astrophysics Research Group, School of Physics, Trinity College Dublin, Dublin 2, Ireland
Accepted: 2 April 2010
Aims. The objective of this study was to examine the kinematics of coronal mass ejections (CMEs) using EUV and coronagraph images, and to make a quantitative comparison with a number of theoretical models. One particular aim was to investigate the acceleration profile of CMEs in the low corona.
Methods. We selected two CME events for this study, which occurred on 2006 December 17 (CME06) and 2007 December 31 (CME07). CME06 was observed using the EIT and LASCO instruments on-board SOHO, while CME07 was observed using the SECCHI imaging suite on STEREO. The first step of the analysis was to track the motion of each CME front and derive its velocity and acceleration. We then compared the observational kinematics, along with the information of the associated X-ray emissions from GOES and RHESSI, with the kinematics proposed by three CME models (catastrophe, breakout and toroidal instability).
Results. We found that CME06 lasted over eight hours while CME07 released its energy in less than three hours. After the eruption, both CMEs were briefly slowed down before being accelerated again. The peak accelerations during the re-acceleration phase coincided with the peak soft X-ray emissions for both CMEs. Their values were ~60 m s-2 for CME06 and ~600 m s-2 for CME07. CME07 reached a maximum speed of over 1000 km s-1 before being slowed down to propagate away at a constant, final speed of ~700 km s-1. CME06 did not reach a constant speed but was moving at a small acceleration by the end of the observation. Our comparison with the theories suggested that CME06 can be best described by a hybrid of the catastrophe model and breakout model while the characteristics of CME07 were most consistent with the breakout model. Based on the catastrophe model, we deduced that the reconnection rate in the current sheet for CME06 was intermediate, the onset of its eruption occurred at a height of ~200 Mm, and the Alfvén speed and the magnetic field strength at this height were approximately 130–250 km s-1 and 7 Gauss, respectively.
Key words: Sun: coronal mass ejections (CMEs) / Sun: flares / magnetic fields / Sun: corona / Sun: atmosphere
© ESO, 2010
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.