Using a 2.5-dimensional ideal MHD model in Cartesian coordinates, weinvestigate the equilibrium properties of coronal magnetic flux ropes in backgroundmagnetic fields that are completely closed. The background fields are produced by adipole, a quadrupole, and an octapole, respectively, located below the photosphereat the same depth. A magnetic flux rope is then launched from below the photo-sphere, and its magnetic properties, i.e., the annular magnetic flux φp and the axialmagnetic flux φz, are controlled by a single emergence parameter. The whole sys-tem eventually evolves into equilibrium, and the resultant flux rope is characterizedby three geometrical parameters: the height of the rope axis, the half-width of therope, and the length of the vertical current sheet below the rope. It is found thatthe geometrical parameters increase monotonically and continuously with increasingφ p and φz: no catastrophe occurs. Moreover, there exists a steep segment in theprofiles of the geometrical parameters versus either φp or φz, and the faster thebackground field decays with height, the larger both the gradient and the growthamplitude within the steep segment will be.
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