Impulsive Acceleration of Coronal Mass Ejections. Ii. Relation to Soft X-Ray Flares and Filament Eruptions

Abstract

Using high time cadence images from the STEREO EUVI, COR1 and COR2 instruments, we derived detailed kinematics of the main acceleration stage for a sample of 95 CMEs in comparison with associated flares and filament eruptions.We found that CMEs associated with flares reveal on average significantly higher peak accelerations and lower acceleration phase durations, initiation heights and heights, at which they reach their peak velocities and peak accelerations. This means that CMEs that are associated with flares are characterized by higher and more impulsive accelerations and originate from lower in the corona where the magnetic field is stronger. For CMEs that are associated with filament eruptions we found only for the CME peak acceleration significantly lower values than for events which were not associated with filament eruptions. The flare rise time was found to be positively correlated with the CME acceleration duration, and negatively correlated with the CME peak acceleration. For the majority of the events the CME acceleration starts before the flare onset (for 75% of the events) and the CME accleration ends after the SXR peak time (for 77% of the events).In ∼60% of the events, the time difference between the peak time of the flare SXR flux derivative and the peak time of the CME acceleration is smaller than ±5 min, which hints at a feedback relationship between the CME acceleration and the energy release in the associated flare due to magnetic reconnection.

On the Statistical Relationship Between CME Speed and Soft X-Ray Flux and Fluence of the Associated Flare

“…This relationship suggests a correlation between the terminal speed of the CME and parameters of the SXR burst, although exceptions from the general trend do exist (Maričić et al, 2007) and are expected to blur the correlation. The correlation coefficient between the logarithms of CME speed and of SXR peak flux derived in the present work, r = 0.48±0.12, is similar to values reported by others: r = 0.47 (Moon et al, 2002), r = 0.35 (Vršnak, Sudar, and Ruždjak, 2005), r = 0.50 (Yashiro and Gopalswamy, 2009), r = 0.32 ± 0.13 (Bein et al, 2012). A distinctly higher correlation, r = 0.93, was found by Moon et al (2003) in a carefully selected small sample of eight flare-CME events, where for four of them, located on the solar disk, the CME speed was corrected for projection effects.…”

“…Moon et al (2002), Yashiro and Gopalswamy (2009) and the present study were restricted to limb CMEs, where projection effects on the CME speed measurements are expected to be minimized. While the correlation coefficients in these limb event studies are higher, the increase is not significant when compared with the statistical uncertainties derived in the present study and Bein et al (2012). We note, however, that the coefficient of the logarithm of SXR peak flux F in the linear relationship log V CME = a log F + b is higher in our study of limb events (a = 0.20 ± 0.08) than in the unrestricted sample of Bein et al (2012) (a = 0.08 ± 0.03).…”

“…Observational studies confirm such a close relationship, when revealing that the acceleration phase of a CME is temporally associated with intense energy release during the rise of the associated SXR burst (Zhang et al, 2001(Zhang et al, , 2004Maričić et al, 2007). Relationships between the speed or kinetic energy of CMEs on the one hand and the importance of the SXR burst, most often the peak flux, on the other have also been revealed by many statistical studies (Moon et al, 2003;Burkepile et al, 2004;Vršnak, Sudar, and Ruždjak, 2005;Maričić et al, 2007;Yashiro and Gopalswamy, 2009;Bein et al, 2012). Occasional negative reports (Aggarwal et al, 2008) and the broad scatter in the statistical relationship show, however, that the quantitative relationship between CMEs and SXR bursts is not simple.…”

“…The statistical studies of Maričić et al (2007) and Bein et al (2012) demonstrated that the CME acceleration is usually pronounced between the start and peak of the SXR burst, with a maximum near the time of the steepest rise of the time profile. After the SXR peak the CME propagates at roughly constant speed in the corona.…”

Microwave radio emissions as a proxy for coronal mass ejection speed in arrival predictions of interplanetary coronal mass ejections at 1 AU

“…Nevertheless, since these are only three events, they do not affect the statistical relationships and their late emission was not taken into account in the following analysis where we consider that the CME acceleration is most pronounced during the rise phase of the SXR burst (e.g. Maričić et al 2007;Bein et al 2012). We use the fluence at 3 GHz (/ 3 GHz ), 9 GHz (/ 9 GHz ) and the maximum fluence (/ max ) when it could be identified.…”