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The relationship between eruptive flares and coronal mass ejections (CMEs) is a topic of ongoing debate, especially regarding the possibility of a common initiation mechanism. We studied the kinematic and hydrodynamic properties of a well-observed event that occurred on 2007 December 31 using data from MESSENGER, RHESSI, and STEREO in order to gain new physical insight into the evolution of the flare and CME. The initiation mechanism was determined by comparing observations to the internal tether-cutting, breakout, and ideal magnetohydrodynamic (MHD) models. Evidence of pre-eruption reconnection immediately eliminated the ideal MHD model. The timing and location of the soft and hard X-ray sources led to the conclusion that the event was initiated by the internal tether-cutting mechanism. In addition, a thermal source was observed to move in a downward direction during the impulsive phase of the event, followed by upward motion during the decay phase, providing evidence for X- to Y-type magnetic reconnection.

The objective of this investigation was to first examine the kinematics of coronal mass ejections (CMEs) using EUV and coronagraph images, and then to make a comparison with theoretical models in the hope to identify the driving mechanisms of the CMEs. We have studied two CMEs which occurred on 2006 Dec. 17 (CME06) and 2007 Dec. 31 (CME07). The models studied in this work were catastrophe, breakout, and toroidal instability models. We found that after the eruption, the accelerations of both events exhibited a drop before increasing again. Our comparisons with the theories suggested that CME06 can be best described by a hybrid of the catastrophe and breakout models while CME07 is most consistent with the breakout model., 9 pages 7 figures

Propagating coronal mass ejections (CMEs) are often accompanied by burst signatures in radio spectrogram data. We present Nancay Radioheliograph observations of a moving source of broadband radio emission, commonly referred to as a type IV radio burst (type IVM), which occurred in association with a CME on the 14th of August 2010. The event was well observed at extreme ultraviolet (EUV) wavelengths by SDO/AIA and PROBA2/SWAP, and by the STEREO SECCHI and SOHO LASCO white light (WL) coronagraphs. The EUV and WL observations show the type IVM source to be cospatial with the CME core. The observed spectra is well fitted by a power law with a negative slope, which is consistent with optically thin gyrosynchrotron emission. The spectrum shows no turn over at the lowest Nancay frequencies. By comparing simulated gyrosynchrotron spectra with Nancay Radioheliograph observations, and performing a rigorous parameter search we are able to constrain several key parameters of the underlying plasma. Simulated spectra found to fit the data suggest a nonthermal electron distribution with a low energy cutoff of several tens to 100 keV, with a nonthermal electron density in the range 100-102 cm–3, in a magnetic field of a few Gauss. The nonthermal energy content of the source is found to contain 0.001%-0.1% of the sources thermal energy content. Furthermore, the energy loss timescale for this distribution equates to several hours, suggesting that the electrons could be accelerated during the CME initiation or early propagation phase and become trapped in the magnetic structure of the CME core without the need to be replenished.

We present observational results of a type II burst associated with a CME-CME interaction observed in the radio and white-light wavelength range. We applied radio direction-finding techniques to observations from the STEREO and Wind spacecraft, the results of which were interpreted using white-light coronagraphic measurements for context. The results of the multiple radio-direction finding techniques applied were found to be consistent both with each other and with those derived from the white-light observations of coronal mass ejections (CMEs). The results suggest that the Type II burst radio emission is causally related to the CMEs interaction.