Abstract:Context. The heating of the solar corona by small heating events requires an increasing number of such events at progressively smaller scales, with the bulk of the heating occurring at scales that are currently unresolved. Aims. The goal of this work is to study the smallest brightening events observed in the extreme-UV quiet Sun. Methods. We used commissioning data taken by the Extreme Ultraviolet Imager (EUI) on board the recently launched Solar Orbiter mission. On 30 May 2020, the EUI was situated at 0.556 … Show more
“…The Extreme-Ultraviolet Imager (EUI) on board Solar Orbiter has revealed complex coronal structures on extremely small size scales down to 400 km (Berghmans et al, 2021). It is of interest to see whether those small-scale features might be scaled-down versions to the BPs and possible faint jets that we find to be candidates for our 14 relatively large EISoutflow events in this study.…”
Section: Discussionmentioning
confidence: 79%
“…There are Extended author information available on the last page of the article many potential sources of the solar wind, and studies of frequent and small-scale phenomena show promise for feeding energy into the corona and solar wind. The first commissioning datasets from the Extreme-Ultraviolet Imager (EUVI) on board Solar Orbiter indicate brightenings at the smallest scales so far seen in the corona from a vantage point of around 0.55 AU (Berghmans et al, 2021). These brightenings were found to have a power-law distribution, with the smallest brightenings seen to have 2 pixels (with an area of 0.08 Mm 2 ).…”
Recent observations from Parker Solar Probe have revealed that the solar wind has a highly variable structure. How this complex behaviour is formed in the solar corona is not yet known, since it requires omnipresent fluctuations, which constantly emit material to feed the wind. In this article we analyse 14 upflow regions in the solar corona to find potential sources for plasma flow. The upflow regions are derived from spectroscopic data from the EUV Imaging Spectrometer (EIS) on board Hinode determining their Doppler velocity and defining regions which have blueshifts stronger than $-6~\mbox{km}\,\mbox{s}^{-1}$
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6
km
s
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1
. To identify the sources of these blueshift data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory (SDO), and the X-ray Telescope (XRT), on board Hinode, are used. The analysis reveals that only 5 out of 14 upflows are associated with frequent transients, like obvious jets or bright points. In contrast to that, seven events are associated with small-scale features, which show a large variety of dynamics. Some resemble small bright points, while others show an eruptive nature, all of which are faint and only live for a few minutes; we cannot rule out that several of these sources may be fainter and, hence, less obvious jets. Since the complex structure of the solar wind is known, this suggests that new sources have to be considered or better methods used to analyse the known sources. This work shows that small and frequent features, which were previously neglected, can cause strong upflows in the solar corona. These results emphasise the importance of the first observations from the Extreme-Ultraviolet Imager (EUI) on board Solar Orbiter, which revealed complex small-scale coronal structures.
“…The Extreme-Ultraviolet Imager (EUI) on board Solar Orbiter has revealed complex coronal structures on extremely small size scales down to 400 km (Berghmans et al, 2021). It is of interest to see whether those small-scale features might be scaled-down versions to the BPs and possible faint jets that we find to be candidates for our 14 relatively large EISoutflow events in this study.…”
Section: Discussionmentioning
confidence: 79%
“…There are Extended author information available on the last page of the article many potential sources of the solar wind, and studies of frequent and small-scale phenomena show promise for feeding energy into the corona and solar wind. The first commissioning datasets from the Extreme-Ultraviolet Imager (EUVI) on board Solar Orbiter indicate brightenings at the smallest scales so far seen in the corona from a vantage point of around 0.55 AU (Berghmans et al, 2021). These brightenings were found to have a power-law distribution, with the smallest brightenings seen to have 2 pixels (with an area of 0.08 Mm 2 ).…”
Recent observations from Parker Solar Probe have revealed that the solar wind has a highly variable structure. How this complex behaviour is formed in the solar corona is not yet known, since it requires omnipresent fluctuations, which constantly emit material to feed the wind. In this article we analyse 14 upflow regions in the solar corona to find potential sources for plasma flow. The upflow regions are derived from spectroscopic data from the EUV Imaging Spectrometer (EIS) on board Hinode determining their Doppler velocity and defining regions which have blueshifts stronger than $-6~\mbox{km}\,\mbox{s}^{-1}$
−
6
km
s
−
1
. To identify the sources of these blueshift data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory (SDO), and the X-ray Telescope (XRT), on board Hinode, are used. The analysis reveals that only 5 out of 14 upflows are associated with frequent transients, like obvious jets or bright points. In contrast to that, seven events are associated with small-scale features, which show a large variety of dynamics. Some resemble small bright points, while others show an eruptive nature, all of which are faint and only live for a few minutes; we cannot rule out that several of these sources may be fainter and, hence, less obvious jets. Since the complex structure of the solar wind is known, this suggests that new sources have to be considered or better methods used to analyse the known sources. This work shows that small and frequent features, which were previously neglected, can cause strong upflows in the solar corona. These results emphasise the importance of the first observations from the Extreme-Ultraviolet Imager (EUI) on board Solar Orbiter, which revealed complex small-scale coronal structures.
“…The high spatial and temporal resolutions allow us to investigate various types of small-scale transient activity. Previous investigations have identified numerous small brightenings termed campfires from these HRI EUV images (Berghmans et al 2021). Here we focus on small-scale collimated jet-like features, which we call coronal microjets.…”
Section: Resultsmentioning
confidence: 94%
“…We describe our observations in Section 2, present the analysis results in Section 3, discuss the results in Section 4 and summarize our findings in Section 5. The primary data 1 we used were taken by the two High Resolution Imagers (HRI) of EUI, the passbands of which are centered at 174 Å (HRI EUV : dominated by Fe x and Fe ix lines) and 1216 Å (HRI Lyα : dominated by the Lyα line of Hydrogen), respectively (Berghmans et al 2021). The HRI EUV passband has a peak response at the temperature of ∼1 MK (Chen et al 2021), and thus samples plasma in the corona.…”
We report the smallest coronal jets ever observed in the quiet Sun with recent highresolution observations from the High Resolution Telescopes (HRI EUV and HRI Lyα ) of the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter. In the HRI EUV (174 Å) images, these microjets usually appear as nearly collimated structures with brightenings at their footpoints. Their average lifetime, projected speed, width, and maximum length are 4.6 min, 62 km s −1 , 1.0 Mm, and 7.7 Mm, respectively. Inverted-Y shaped structures and moving blobs can be identified in some events. A subset of these events also reveal signatures in the HRI Lyα (H i Lyα at 1216 Å) images and the extreme ultraviolet images taken by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. Our differential emission measure analysis suggests a multi-thermal nature and an average density of ∼1.4×10 9 cm −3 for these microjets. Their thermal and kinetic energies were estimated to be ∼3.9×10 24 erg and ∼2.9×10 23 erg, respectively, which are of the same order of the released energy predicted by the nanoflare theory. Most events appear to be located at the edges of network lanes and magnetic flux concentrations, suggesting that these coronal microjets are likely generated by magnetic reconnection between small-scale magnetic loops and the adjacent network field.
“…1 . This represents a breakthrough for solar observation in the X-ray and EUV regions in China, and images obtained from the X-EUVI will play an important role in solar research and space weather forecasting 1 – 5 . Fig.…”
The solar X-ray and Extreme Ultraviolet Imager (X-EUVI), which was developed by CIOMP, is China’s first space-based solar X-ray and Extreme Ultraviolet (EUV) imager; it has been loaded onto the Fengyun-3E Satellite, which is supported by the China Meteorological Administration (CMA), for solar observation. It commenced working on July 11, 2021, and was used to obtain the first X-ray and EUV images in China. X-EUVI employs an innovation dual band design to monitor a much larger temperature range across the Sun, covering the 0.6–8.0 nm wavelength band of the X-ray region and the 19.5 nm band of the EUV region.
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