If you image the Sun in x rays or the extreme ultraviolet, you'll see its corona, a halo of million‐degree gas whose spectacular structures, known as active regions, are associated with photospheric sunspots. Between the active regions, and covering most of the solar surface when sunspots are absent, is the so‐called quiet corona, which glows less brightly and varies more modestly. An accurate explanation of exactly how the corona is heated has long eluded researchers, and, until now, they have found it relatively easier to make progress in the case of the active regions than the quiet Sun.

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