Observations of a pulse-driven cool polar jet by SDO/AIA

Abstract

We observe a solar jet at north polar coronal hole (NPCH) using SDO AIA 304 Å image data on 3 August 2010. The jet rises obliquely above the solar limb and then retraces its propagation path to fall back. We numerically model this solar jet by implementing a realistic (VAL-C) model of solar temperature.We solve two-dimensional ideal magnetohydrodynamic equations numerically to simulate the solar jet. We consider a localized velocity pulse that is essentially parallel to the background magnetic field lines and is initially launched at the top of the solar photosphere. The pulse steepens into a shock at higher altitudes, which triggers plasma perturbations that exhibit the observed features of the jet. The typical direction of the pulse also clearly exhibits the leading front of the moving jet. Our numerical simulations reveal that a large amplitude initial velocity pulse launched at the top of the solar photosphere in general produces the observed properties of the jet, e.g., upward and backward average velocities, height, width, life-time, and ballistic nature.The close match between the jet observations and numerical simulations provides a first strong evidence that this jet is formed by a single velocity pulse. The strong velocity pulse is most likely generated by the low-atmospheric reconnection in the polar region, which triggers the jet. The downflowing material of the jet most likely is absorbed in the next upcoming velocity pulses from the lower solar atmosphere, and because of that we only see a single jet moving upward in the solar atmosphere.