Search for the Relationship between the Velocity of a Coronal Mass Ejection and the Decay Rate of the Magnetic Field in the Region of Mass Emission Generation

Abstract

In this paper, we search for the relationship between the Vlin linear projection velocity and the Vss velocity in the 3D space of coronal mass ejections (CMEs) recorded by LASCO coronagraphs with an “n” decay rate of the transverse component of the Bt magnetic field above the polarity inversion line (PIL) of the photospheric magnetic field in the active region (AR) in which the CME appeared. The Bt decay rate at an altitude h measured from the photosphere was calculated with the formula n(h) = –(h/Bt)(dBt/dh). Three-dimensional calculations of the magnetic field were performed in the potential approximation. The positive trend of the dependences 〈n〉(Vlin) and 〈n〉(Vss), however, does not have sufficient statistical significance: on average, the larger is 〈n〉, the higher are the determined Vlin and Vss CME velocities. Here, 〈n〉 includes the averaging of n over both the altitude and along the extended section of the PIL identified within each studied AR. The relationship between the quality of 〈n〉(Vlin) and 〈n〉(Vss) is shown to depend on the PIL section in the AR within which n is averaged. Based on the example of a fast CME on March 7, 2012, and a slow CME on October 22, 2013, it is shown that the difference in 〈n〉 for CMEs with different velocities is greater if the averaging of n along the PIL is performed within the CME initiation region, not along the entire extended PIL section in the AR.