Physical differences between the initial phase of the formation of two types of coronal mass ejections

Abstract

Physical differences in the formation of “gradual” and “impulsive” coronal mass ejections (CMEs) at heights of h < 0.2 R _⊙ just before and during the initial phase of their motion are studied using AIA/SDO ultraviolet data (h is the altitude above the solar surface and R _⊙ is the solar radius). The basic structure of a gradual CME is a magnetic rope located in the corona. During an hour or more preceding the initial phase, the magnetic rope demonstrates an increase in brightness and transverse size, first of the low, inner elements of the rope and then of elements in its outer envelope most distant from the Sun. The rope remains motionless during this time. The initial phase of a gradual CME begins from the motion of the magnetic rope’s outer envelope, which further becomes the basis for the CME frontal structure. At this stage, the inner low elements of the rope remain almost motionless. The initial phase of an impulsive CME begins with the appearance near the photosphere of a cavity moving away from the Sun; the dynamics of this cavity probably correspond to a magnetic tube filled with cool plasma rising from beneath the photosphere. This magnetic tube collides with and drags arch structures, which initially block the tube’s motion. These arch structures contribute to the CME formation, although the magnetic tube itself forms the basis of the CME.