Widespread occurrence of high-velocity upflows in solar active regions

Abstract

Aims. We performed a systematic study of 12 active regions (ARs) with a broad range of areas, magnetic fluxes, and associated solar activity in order to determine whether there are upflows present at the AR boundaries and, if these upflows exist, whether there is a high-speed asymmetric blue wing component present in them. Methods. To identify the presence and locations of the AR upflows, we derive relative Doppler velocity maps by fitting a Gaussian function to Hinode/EIS Fe XII 192.394 Å line profiles. To determine whether there is a high-speed asymmetric component present in the AR upflows, we fit a double Gaussian function to the Fe XII 192.394 Å mean spectrum that is computed in a region of interest situated in the AR upflows. Results. Upflows are observed at both the eastern and western boundaries of all ARs in our sample, with average upflow velocities ranging between −5 and −26 km s−1. A blue wing asymmetry is present in every line profile. The intensity ratio between the minor high-speed asymmetric Gaussian component compared to the main component is relatively small for the majority of regions; however, in a minority of cases (8/30) the ratios are large and range between 20 and 56 %. Conclusions. These results suggest that upflows and the high-speed asymmetric blue wing component are a common feature of all ARs.

Inconspicuous Solar Polar Coronal X-Ray Jets as the Source of Conspicuous Hinode/EUV Imaging Spectrometer Doppler Outflows

“…Such observations could provide additional support that the Schwanitz et al (2021) features, at least the five examined here, are indeed small-scale versions of such bona fide coronal jets. It will also be of interest to see how the outflows here connect to other outflow events commonly observed with EIS and similar spectrometers (e.g., Harra et al 2008Harra et al , 2012Brooks & Warren 2011;Brooks et al 2020;Tian et al 2021;Yardley et al 2021). It is also of interest to investigate whether the EIS Doppler features referred to as dark jets by Young (2015) might be similar to the features we observe here.…”

Inconspicuous Solar Polar Coronal X-ray Jets as the Source of Conspicuous Hinode/EUV Imaging Spectrometer (EIS) Doppler Outflows

“…It will also be of interest to see how the outflows here connect to other outflow events commonly observed with EIS and similar spectrometers (e.g. Harra et al 2008;Brooks & Warren 2011;Harra et al 2012;Brooks et al 2020;Tian et al 2021;Yardley et al 2021). It is also of interest to investigate whether the EIS Doppler features referred to as dark jets by Young (2015) might be similar to the features we observe here.…”

Spectroscopic observation of a transition region network jet

“…Previous work has investigated the common appearance of asymmetrical emission lines formed in the corona and TR (see e.g., Peter 2001;Hara et al 2008;Tian et al 2011;Yardley et al 2021). As is the conclusion of this work, such line asymmetries are mostly attributed to the overlapping of background emission (primary component) and high-speed flows (secondary component).…”