非表示:
キーワード:
-
要旨:
Coronal holes are areas on the Sun with open magnetic field lines. They are a source region of the solar wind, but how the wind emerges from coronal holes is not known. We observed a coronal hole using the Extreme Ultraviolet Imager on the Solar Orbiter spacecraft. We identified jets on scales of a few hundred kilometers, which last 20 to 100 seconds and reach speeds of ~100 kilometers per second. The jets are powered by magnetic reconnection and have kinetic energy in the picoflare range. They are intermittent but widespread within the observed coronal hole. We suggest that such picoflare jets could produce enough high-temperature plasma to sustain the solar wind and that the wind emerges from coronal holes as a highly intermittent outflow at small scales. Plasma is constantly streaming away from the Sun, forming the solar wind. A likely source of this plasma is coronal holes, regions of the Sun?s corona with magnetic field lines that open outward. Chitta et al. observed a coronal hole in the extreme ultraviolet using the Solar Orbiter spacecraft and identifed several types of small-scale jets within it (see the Perspective by Ugarte-Urra and Wang). Large numbers of jets occurred during the observation, but each one lasted only a few dozen seconds. The authors calculated that the jets provide enough energy and plasma to supply a large fraction of the solar wind, at least during quiet periods. ?Keith T. Smith Extreme ultraviolet images of the Sun show numerous small-scale jets that could supply plasma to the solar wind.
