Speaker
Description
We present results of the first high cadence image sequence of the Extreme Ultraviolet Imager (EUI) taken on 2020 May 30, when Solar Orbiter was 31.5 degrees in solar longitude separated from Earth & SDO, and at 0.56AU from the Sun. At this distance, the two-pixel spatial resolution of EUI’s High Resolution EUV Telescope (HRIEUV) was 400 km. HRIEUV observed a quiet Sun region and detected small localised brightenings, nicknamed ’campfires’, with length scales between 400 km and 4000 km and durations between 10 sec and 200 sec. The smallest and weakest of these HRIEUV brightenings have not been previously observed. Simultaneous observations from the EUI High-resolution Lyman-α telescope (HRILYA) do not show localised brightening events, but the locations of the HRIEUV events clearly correspond to the chromospheric network. Comparisons with simultaneous AIA images shows that most events can also be identified in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA, although they appear weaker and blurred. Our differential emission measure (DEM) analysis indicated coronal temperatures. We determined the height for a few of these campfires to be between 1 and 5 Mm above the photosphere. We interpret these events as a new extension to the flare-microflare-nanoflare family. Given their low height, the EUI ‘campfires’ could stand as a new element of the fine structure of the transition region-low corona, that is, as apexes of small-scale loops that undergo internal heating all the way up to coronal temperatures.
