ALBERT

Description: Unravelling the magnetic processes that build up the free energy for large-scale solar eruptions and trigger that energy's release in the eruption is a continuing challenge in solar physics. Such large-scale eruptions are comparatively infrequent, with the moderate level ones (say, GOES M-class events) occurring perhaps once every few days on average during active-activity times. In contrast, solar coronal jets, which are long (~50,000 km), narrow (〈~10,000 km), transient (~10---20 min) plasma spires with bright bases and that are seen in soft X-rays and EUV, occur much more frequently, likely several hundred times per day independent of large-scale solar activity level. Recent studies indicate that coronal jets are small-scale versions of large-scale eruptions, often produced by eruption of a small-scale "miniflament," that results in a "miniflare" analogous to a larger typical solar flare, and that sometimes produces a CME analogue (a "narrow CME" or "white-light jet"). Under the assumption that jets are small-scale eruptions, their higher occurrence frequency and faster build-up evolution reveals perhaps fundamental aspects of all eruptions that are not as easy to discern in the more-complex magnetic environment and the slower build up to the larger eruptions. For example, several studies show that jets occur at magnetic-flux-cancelation locations, suggesting that this is a key energy build-up and release process for eruptions of all sizes. This work was supported by NASA's Heliophysics Guest Investigator (HGI), Heliophysics Supporting Research (HSR), and Heliophysics System Observatory Connect (HSOC) Programs, and by the NASA/MSFC Hinode Project.

Description: Solar coronal jets of all sizes are magnetically channeled eruptions that occur in all types of solar environments (e.g. active regions, quiet-Sun regions and coronal holes). They are often observed in the solar corona in EUV and coronal X-ray images. Recent studies show that coronal jets are driven by the eruption of small-scale filaments (minifilaments). Once the eruption is underway external and internal reconnection evidently makes the jet spire and the bright emission in the jet base. By examining pre-jet evolutionary changes in line-of-sight SDO/HMI magnetograms while examining concurrent E(UV) images (from SDO/AIA, Solar Orbiter/EUI, and IRIS) of coronal and transition-region emission, we find clear evidence that flux cancelation is the main process that builds pre-jet minifilaments, and is also the main process that triggers the eruptions. In addition to typical coronal jets, we find that small-scale jets (jetlets/network jets) are rooted at the edges of magnetic network lanes, and often come from the sites of flux cancelation. We also compare some of the small-scale observed jets with analogous jets in a Bifrost MHD simulation of a quiet Sun region. Simulations clearly show that jets often come from sites of flux cancelation. From our observations we infer that magnetic reconnection driven flux cancelation is the fundamental process for the buildup and triggering of all sizes of jets.