Reconnection-Driven Coronal-Hole Jets with Gravity and Solar Wind

TL;DR

This study extends previous models of coronal-hole jets by including gravity and solar wind effects in spherical geometry, revealing how jets are initiated and propagate, aligning well with observational data and explaining solar wind features.

Contribution

It introduces a more realistic simulation of coronal-hole jets incorporating gravity and solar wind, demonstrating jet initiation via kink instability and propagation as Alfvén waves.

Findings

Jets are initiated by kink-like instability triggering reconnection.

Jet propagation involves traveling Alfvén wave fronts and plasma acceleration.

Scaling relationships link source region properties to jet characteristics.

Abstract

Coronal-hole jets occur ubiquitously in solar coronal holes, at EUV and X-ray bright points associated with intrusions of minority magnetic polarity. The embedded-bipole model for these jets posits that they are driven by explosive, fast reconnection between the stressed closed field of the embedded bipole and the open field of the surrounding coronal hole. Previous numerical studies in Cartesian geometry, assuming uniform ambient magnetic field and plasma while neglecting gravity and solar wind, demonstrated that the model is robust and can produce jet-like events in simple configurations. We have extended these investigations by including spherical geometry, gravity, and solar wind in a nonuniform, coronal hole-like ambient atmosphere. Our simulations confirm that the jet is initiated by the onset of a kink-like instability of the internal closed field, which induces a burst of reconnection between the closed and external open field, launching a helical jet. Our new results demonstrate that the jet propagation is sustained through the outer corona, in the form of a traveling nonlinear Alfven wave front trailed by slower-moving plasma density enhancements that are compressed and accelerated by the wave. This finding agrees well with observations of white-light coronal-hole jets, and can explain microstreams and torsional Alfven waves detected in situ in the solar wind. We also use our numerical results to deduce scaling relationships between properties of the coronal source region and the characteristics of the resulting jet, which can be tested against observations.