A MODEL FOR SOLAR POLAR JETS

TLDR

Solar coronal jets are driven by magnetic reconnection at null‑point fan‑separatrix topologies, but explaining their brief, energetic bursts rather than continuous activity seen in polar plumes remains a challenge. The study proposes a model for polar coronal jets that attributes their brief, energetic bursts to the suppression of reconnection in axisymmetric null‑point topologies. The model imposes a twisting motion that preserves axisymmetry, allowing magnetic stress to accumulate until an ideal instability breaks symmetry and triggers explosive reconnection, producing high‑speed jets via nonlinear Alfvén waves in 3‑D MHD simulations. 3‑D MHD simulations confirm that the proposed mechanism generates massive, high‑speed jets powered by nonlinear Alfvén waves.

Abstract

We propose a model for the jetting activity that is commonly observed in the Sun's corona, especially in the open-field regions of polar coronal holes. Magnetic reconnection is the process driving the jets and a relevant magnetic configuration is the well known null-point and fan-separatrix topology. The primary challenge in explaining the observations is that reconnection must occur in a short-duration energetic burst, rather than quasi-continuously as is implied by the observations of long-lived structures in coronal holes, such as polar plumes. The key idea underlying our model for jets is that reconnection is forbidden for an axisymmetrical null-point topology. Consequently, by imposing a twisting motion that maintains the axisymmetry, magnetic stress can be built up to high levels until an ideal instability breaks the symmetry and leads to an explosive release of energy via reconnection. Using three-dimensional magnetohydrodynamic simulations, we demonstrate that this mechanism does produce massive, high-speed jets driven by nonlinear Alfvén waves. We discuss the implications of our results for observations of the solar corona.