Spectroscopic observation of a transition region network jet^⋆

Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
e-mail: gorman@mps.mpg.de

Received: 23 December 2021
Accepted: 15 February 2022

Abstract

Aims. Ubiquitous transition region (TR) network jets are considered to be substantial sources of mass and energy to the corona and solar wind. We conduct a case study of a network jet to better understand the nature of mass flows along its length and the energetics involved in its launch.

Methods. We present an observation of a jet with the Interface Region Imaging Spectrograph (IRIS), while also using data from the Solar Dynamics Observatory (SDO) to provide further context. The jet was located within a coronal hole close to the disk center.

Results. We find that a blueshifted secondary component of TR emission is associated with the jet and is persistent along its spire. This component exhibits upward speeds of approximately 20–70 km s⁻¹ and shows enhanced line broadening. However, plasma associated with the jet in the upper chromosphere shows downflows of 5–10 km s⁻¹. Finally, the jet emanates from a seemingly unipolar magnetic footpoint.

Conclusions. While a definitive magnetic driver is not discernible for this event, we infer that the energy driving the network jet is deposited at the top of the chromosphere, indicating that TR network jets are driven from the mid-atmospheric layers of the Sun. The energy flux associated with the line broadening indicates that the jet could be powered all the way into the solar wind.