Kinematics of CMEs and related shocks from LASCO data: Comparative analysis

Abstract

We estimated the positions and velocities of the 10 fast limb CMEs with sources within the 30-degree from the limb and 10 fast halo CMEs with sources within the 30-degree from the solar disk center (central CMEs) using the LASCO-C2 and C3 images. The considered velocities, on which the results are based, include projection effects. We compared kinematic characteristics of the CME body with CME-related shocks whose linear projection velocities greater than 1500 km/s. For all the considered events: (1) the distance between the CME body and the related shock ΔR=(Rsh−Rb) increases with time; (2) the shock velocity Vsh is greater than the CME body velocity Vb; (3) the CME body acceleration modulus |ab| and the related shock acceleration modulus |ash| differ. Herewith, in some cases, |ash|>|ab|, and in other cases, on the contrary, |ash|<|ab|; (4) the difference in the velocities ΔV=(Vsh−Vb) grows with time for limb CMEs and decreases for central CMEs; (5) the variations of velocity-time profiles for the CME and shock are established to be equal: the velocities of both coronal structures either increase or decrease simultaneously. The following averaged values characterize the differences in the kinematics of the CME and shock: 〈ΔR〉 = 1.7 R⊙ (R⊙ is the solar radius), 〈ΔV〉 = 250 km/s, 〈Vsh/Vb〉 = 1.2, 〈ab〉 = 65 m/s2, 〈ash〉 = 70 m/s2.