34th Solar Physics Division Meeting, June 2003
Session 23 Coronal Mass Ejections II
Oral, Thursday, June 19, 2003, 11:00am-12:00noon, Auditorium

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[23.05] Observing Kinematics of Coronal Mass Ejections

J. Zhang (George Mason University)

We present the observations on kinematics of a set of three coronal mass ejections (CMEs), which show impulsive, moderate and gradual acceleration, respectively. The three CMEs represent the wide spectrum distribution of CME kinematical characteristics. The CMEs are well observed from the solar surface up to 30 Rsun, including their initiation, acceleration and following propagation. CME observations were obtained by LASCO (Large Angle Spectrometric and Coronagraph) on SOHO spacecraft; the LASCO/C1 provided critical observation on acceleration of the CMEs. The first CME, which occurred on June 11, 1998, is a typical impulsive CME. Its impulsive or major acceleration phase lasted a certain period of about 30 minutes during which it speeded up to about 1000 km/s from its initial velocity of 50 km/s, and it traveled a distance of about 2.0 Rsun from 1.4 to 3.4 Rsun; in this phase, its average acceleration rate is about 500 m/s2. The second CME, which occurred on Oct. 25, 2000, showed moderate acceleration. Its major acceleration phase lasted a long period of almost 160 minutes, during which it speeded up to about 800 km/s and traveled a distance of about 5 Rsun from 2.0 to 7.0 Rsun; in this phase, its average acceleration is about 60 m/s2, which is almost one order of magnitude smaller than the first CME. The third CME, a typical gradual CME which occurred on Oct. 19, 1997, showed very weak but prolonged acceleration. There is no impulsive acceleration phase associated with this event. It gradually picked up its speed over a period of more than 24 hours and eventually reached a speed of 400 km/s at about 20 Rsun. Its average acceleration rate is about 6 m/s2, which is almost two order of magnitude smaller than that in the impulsive phase of the first CME. For the first 2 CMEs, which are associated with GOES soft X-ray flares, we have find that the phase of CME impulsive acceleration coincides with the phase of flux rising of the flare. We suggest that magnetic reconnection play a major role in accelerating CMEs impulsively, though CMEs themselves can be initiated by other mechanisms such as loss-equilibrium.


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