Small-scale EUV features as the drivers of coronal upflows in the quiet Sun

SCHWANITZ, C.; HARRA, L.; MANDRINI, C. H.; STERLING, A. C.; RAOUAFI, N. E.; BERGHMANS, D.; AUCHÈRE, F.; BARCZYNSKI, K.; AZNAR CUADRADO, R.; BUCHLIN, É.; KRAAIKAMP, E.; LONG, D. M.; PARENTI, S.; PETER, H.; RODRIGUEZ, L.; SCHÜHLE, U.; SMITH, P.; TERIACA, L.; VERBEEK, C.; ZHUKOV, A.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2023

0004-6361

Context. Coronal upflows in the quiet Sun are seen in a wide range of features, including jets and filament eruptions. The in situmeasurements from Parker Solar Probe within ≈ 0.2 au have demonstrated that the solar wind is highly structured, showing abrupt andnear-ubiquitous magnetic field reversals (i.e., switchbacks) on different timescales. The source of these structures has been associatedwith supergranular structures on the solar disc. This raises the question of whether there are additional small coronal features thatcontribute energy to the corona and produce plasma that potentially feeds into the solar wind.Aims. During the Solar Orbiter first science perihelion, high-resolution images of the solar corona were recorded using the ExtremeUltraviolet High Resolution Imager (HRIEUV) from the Extreme Ultraviolet Imager (EUI). The Hinode spacecraft was also observingat the same location providing coronal spectroscopic measurements. Combining the two datasets allows us to determine the cause ofthe weak upflows observed in the quiet Sun and the associated activity.Methods. We used a multi-spacecraft approach to characterise regions of upflows. The upflows were identified in the Fe xii emissionline by the Hinode EUV Imaging Spectrometer (EIS). We then used imaging data from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory (SDO/AIA) and the High Resolution Imagers (HRI) from EUI on board the Solar Orbiter toidentify coronal features and magnetic field data from the SDO Helioseismic and Magnetic Imager (HMI). Interface Region ImagingSpectrograph (IRIS) observations were also used to understand the photospheric and chromospheric driving mechanisms.Results. We have identified two regions of coronal upflows in the quiet Sun, with respective sizes and lifetimes of (20 Mm2, 20 min)and (180 Mm2, several hours), which are contrasting dynamic events. Both examples show weak flux cancellation, indicating thatthe source of the upflows and enhancements is related to the magnetic field changes. The first event, a larger upflow region, showsvelocities of up to -8.6 km s−1 at the footpoint of a complex loop structure. We observe several distinct extreme ultraviolet (EUV)features including frequent loop brightenings and plasma blobs travelling along closed coronal loops. The second upflow region hasvelocities of up to -7.2 km s−1. Within it, a complex EUV feature that lasts for about 20 minutes can be seen. This main featurehas several substructures. During its appearance, a clear mini-filament eruption takes place at its location, before the EUV featuredisappears.Conclusions. Two features, with contrasting properties, show upflows with comparable magnitudes. The first event, a complex loopstructure, shares several similarities with active region upflows. The second one, a complex small-scale feature that could not havebeen well resolved with previous instruments, triggered a cascade of events, including a mini-filament that lead to a measurableupflow. This is remarkable for an EUV feature that many instruments can barely resolve. The complexity of the two events, includingsmall loop brightenings and travelling plasma blobs for the first and EUV small-scale loops and mini-filament for the second onewould not have been identifiable as the sources of upflow without an instrument with the spatial resolution of HRIEUV at this distanceto the Sun. These results reinforce the importance of the smallest-scale features in the Sun and their potential relevance for and impacton the solar corona and the solar wind.ARTICULO EN PRENSA