Ubiquitous Small-scale Extreme-ultraviolet Upflow-like Events above Network Regions Observed by the Solar Orbiter/Extreme Ultraviolet Imager

Abstract

Universal small-scale solar activity in the quiet region is suggested to be a potential source of solar wind and the upper solar atmosphere. Here, with the high-resolution 174 Å imaging observations from the Solar Orbiter/Extreme Ultraviolet Imager, we investigate 59 EUV upflow-like events observed in the quiet Sun. Their average apparent (plane-of-sky) velocity, lifetime, and propagation distance are measured as 62 km s ^−1 , 68.6 s, and 3.94 Mm, respectively. These upflow-like events exhibit dynamic characteristics but lack base brightening, featuring a hot front and subsequent cold plasma ejection. A total of 39% of the EUV upflow-like events exhibit recurrent characteristics. Unprecedented high-resolution 174 Å observations reveal that some EUV upflow-like events exhibit blob-like fine structures and multistrand evolutionary features, and some upflow-like events can cause localized haze-like plasma heating ahead of their spire region during the ejection process. A subset of the EUV upflow-like events covered by the Solar Dynamics Observatory reveals that they appear at the chromospheric networks. Through emission measure analysis, we found that these upflow-like events eject hot plasma of transient region or coronal temperature (an average of ~10 ^5.5 K). We suggest that EUV upflow-like events may be EUV counterparts of chromospheric spicules and/or transition region network jets and play a role in heating the localized corona above the network regions.

Keywords

• Quiet Sun
• Solar ultraviolet emission
• Solar corona
• Solar spicules