Downward catastrophe of solar magnetic flux ropes: another cause of flares?

Abstract:

Study about the evolutions of coronal magnetic flux ropes has important significance in understanding solar energetic activities. In previous studies, it is suggested that there exists a catastrophe, during which the flux rope jumps upward from the equilibrium at a lower altitude to another equilibrium at higher altitude or running away. This 'upward' catastrophe is believed to be an efficient mechanism for the solar eruptive activities, such as flares and coronal mass ejections. In this work, we numerically study and discuss the possibility of the catastrophe of a flux rope in the reversed way, i.e., the flux rope jumps from a higher altitude to a lower altitude, which we call it 'downward' catastrophe. From the simulation in force free magnetic field under a partially open bipolar magnetic configuration, we found that such 'downward' catastrophe does exists. Although the flux rope moves oppositely during the two different catastrophes, the magnetic energies are always released. This indicates that the flaring phenomenon might be also triggered by the 'downward' catastrophe, during which no coronal mass ejections will accompany.