The Magnetic Origin of Solar Campfires: Observations by Solar Orbiter and SDO

Solar campfires are small-scale, short-lived coronal brightenings, recently observed in 174 Å images by Extreme Ultraviolet Imager (EUI) on board Solar Orbiter (SolO). Here we investigate the magnetic origin of 52 campfires, in quiet-Sun, using line-of-sight magnetograms from Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) together with extreme ultraviolet images from SolO /EUI and SDO/Atmospheric Imaging Assembly (AIA). We find that the campfires are rooted at the edges of photospheric magnetic network lanes; (ii) most of the campfires reside above neutral lines and 77% of them appear at sites of magnetic flux cancelation between the majority-polarity magnetic flux patch and a merging minority-polarity flux patch, with a flux cancelation rate of ~10¹⁸ Mx hr^-1; some of the smallest campfires come from the sites where magnetic flux elements were barely discernible in HMI; (iii) some of the campfires occur repeatedly from the same neutral line; (iv) in the large majority of instances (79%), campfires are preceded by a cool-plasma structure, analogous to minifilaments in coronal jets; and (v) although many campfires have “complex” structure, most campfires resemble small-scale jets, dots, or loops. Thus, “campfire” is a general term that includes different types of small-scale solar dynamic features. They contain sufficient magnetic energy (~10²⁶–10²⁷ erg) to heat the solar atmosphere locally to 0.5–2.5 MK. Their lifetimes range from about 1 minute to over 1 hour, with most of the campfires having a lifetime of <10 minutes. The average lengths and widths of the campfires are 5400 ± 2500 km and 1600 ± 640 km, respectively. Our observations suggest that (a) the presence of magnetic flux ropes may be ubiquitous in the solar atmosphere and not limited to coronal jets and larger-scale eruptions that make CMEs, and (b) magnetic flux cancelation, most likely driven by magnetic reconnection in the lower atmosphere, is the fundamental process for the formation and triggering of most campfires.