Pseudostreamer influence on flux rope evolution

Abstract

Context. A highly important aspect of solar activity is the coupling between eruptions and the surrounding coronal magnetic field topology, which determines the trajectory and morphology of the ejected plasma. Pseudostreamers (PSs) are coronal magnetic structures formed by arcs of twin loops capped by magnetic field lines from coronal holes of the same polarity that meet at a central spine. PSs contain a single magnetic null point in the spine, immediately above the closed field lines, which potentially influences the evolution of nearby flux ropes (FRs). Aims. Because of the impact of magnetic FR eruptions on space weather, we aim to improve current understanding of the deflection of coronal mass ejections (CMEs). To understand the net effect of PSs on FR eruptions, it is first necessary to study diverse and isolated-PS scenarios that are not influenced by other magnetic structures. Methods. We performed numerical simulations in which a FR structure is in the vicinity of a PS magnetic configuration. The combined magnetic field of the PS and the FR results in the formation of two magnetic null points. We evolve this scenario by numerically solving the magnetohydrodynamic equations in 2.5D. The simulations consider a fully ionised compressible ideal plasma in the presence of a gravitational field and a stratified atmosphere. Results. We find that the dynamic behaviour of the FR can be categorised into three different classes based on the FR trajectories and whether it is eruptive or confined. Our analysis indicates that the magnetic null points are decisive in the direction and intensity of the FR deflection and their hierarchy depends on the topological arrangement of the scenario. Moreover, the PS lobe acts as a magnetic cage enclosing the FR. We report that the total unsigned magnetic flux of the cage is a key parameter defining whether or not the FR is ejected.