A numerical simulation of the formation and propagation of CMEs in nested closed magnetic structures †*

Some qualitative results of numerical simulation of a special type of coronal mass ejections are presented where the field direction of the central closed magnetic structure in the front half of the CME is opposite to that of the solar global dipolar magnetic field. As shown by the results of computation, between the closed magnetic field in the core of the CME and the oppositely directed solar dipolar magnetic field there exists a transitional magnetic structure. As the CME propagates outward, this transitional structure gradually increases in size. This may be used to interpret why a certain type of bipolar magnetic clouds have been observed by spacecraft in which the direction of the magnetic field in the front half of the cloud is opposite to that of the solar dipolar global magnetic field. The present simulation is based on a background coronal streamer that contains nested closed magnetic structures and that the CME is triggered at an appropriate position.