Work

Small-scale impulsive extreme-UV emission enhancements along network loops

Year: 2026

Type: article

Abstract: Context. Network loops are a common feature in the quiet Sun. The physical processes sustaining their energy budget are still discussed. Aims. We relied on a multi-instrumental (Solar Orbiter/EUI, Solar Orbiter/PHI, and IRIS) observation of a six-hour quiet-Sun region to measure the dynamics and the possible magnetic drivers of impulsive Extreme Ultraviolet (EUV) emission enhancements along network loops. Methods. We report the detection of small-scale impulsive EUV emission enhancements with EUI/HRIEUV in three network loops. We selected four EUV emission enhancements to measure their plane-of-sky velocities in HRIEUV, their Doppler velocities in the Si IV line (log T = 4.8) with IRIS, and their possible relation to small-scale flux emergence and fluctuation in one of the loop footpoints. Results. The plane-of-sky velocities of the four EUV emission enhancements have a component that seems to appear almost instantaneously along the loop (≥220 km s −1 ), and two of them had a co-temporal component with a plane-of-sky velocity of up to (77 ± 19) km s −1 , starting near one of the loop footpoints. In one case, we measured a co-temporal intensity increase in the Si IV line with IRIS that is associated with Doppler velocities down to −32 km s −1 and up to 18 km s −1 along the line of sight. Finally, we measured cases of small-scale (≈8 × 10 16 Mx) mixed-polarity field emergence and fluctuation near one of the loop footpoints. Conclusions. We conclude that the fast components on the plane-of-sky are consistent with a thermal transfer or supersonic plasma flows, while the slower component is consistent with plasma flows. A possible physical origin for these EUV emission enhancements would be magnetic reconnection driven by either a photospheric motion of the loop footpoints or by the reconnection of the loop with small-scale magnetic bipoles.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202558068