Kinematics of coronal mass ejections in the LASCO field of view
Anitha Ravishankar, G. Michałek, S. Yashiro
Abstract
In this paper we present a statistical study of the kinematics of 28894 coronal mass ejections (CMEs) recorded by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory spacecraft from 1996 until mid-2017. The initial acceleration phase is characterized by a rapid increase in CME velocity just after eruption in the inner corona. This phase is followed by a non-significant residual acceleration (deceleration) characterized by an almost constant speed of CMEs. We demonstrate that the initial acceleration is in the range 0.24–2616 m s −2 with median (average) value of 57 m s −2 (34 m s −2 ) and it takes place up to a distance of about 28 R SUN with median (average) value of 7.8 R SUN (6 R SUN ). Additionally, the initial acceleration is significant in the case of fast CMEs ( V > 900 km s −1 ), where the median (average) values are about 295 m s −2 (251 m s −2 ), respectively, and much weaker in the case of slow CMEs ( V < 250 km s −1 ), where the median (average) values are about 18 m s −2 (17 m s −2 ), respectively. We note that the significant driving force (Lorentz force) can operate up to a distance of 6 R SUN from the Sun during the first 2 hours of propagation. We found a significant anti-correlation between the initial acceleration magnitude and the acceleration duration, whereas the residual acceleration covers a range from −1224 to 0 m s −2 with a median (average) value of −34 m s −2 (−17 m s −2 ). One intriguing finding is that the residual acceleration is much smaller during the 24th cycle in comparison to the 23rd cycle of solar activity. Our study has also revealed that the considered parameters, initial acceleration (ACC INI ), residual acceleration (ACC RES ), maximum velocity ( V MAX ), and time at maximum velocity (Time MAX ) mostly follow solar cycles and the intensities of the individual cycle.