The partial expulsion of a magnetic flux rope

We demonstrate the partial expulsion of a three-dimensional magnetic flux rope, in which an upper, escaping rope is separated from a lower, surviving rope by cusped, reconnecting loop field lines. We use the three-dimensional magnetohydrodynamic model recently presented by Fan, extended to examine the erupting rope's end state. As in that work, the modeled flux rope in spherical coordinates erupts when enough twist has emerged to induce a loss of equilibrium. After multiple reconnections at current sheets that form during the eruption, the rope breaks in two, so that only a part of it escapes. We consider the details of how this separation occurs and discuss the observational significance of such a partially expelled flux rope for partially erupting filaments and re-forming X-ray sigmoids.