From Earth, the Sun appears comfortingly constant, always just about the same brightness in our blue skies during the day. Up close, however, it’s a lot more tumultuous, dotted with sunspots and roiling with solar flares.
Solar activity varies in fairly predictable 11 year cycles, meaning there are more sunspots and flares at certain intervals. But, there’s also fluctuation between cycles—some periods are more intense, and others, like the three decade Maunder minimum in the late 1600s, are almost entirely devoid of sunspots. Astronomers have been trying to pin down the exact physics behind these phenomena for years, although they have a clue as to the culprit: the Sun’s magnetic field.
New research, published in the journal Monthly Notices of the Royal Astronomical Society last year and recently presented at a symposium of the International Astronomical Union, simulates how the stars’ spin can lead to very different kinds of solar cycles. They explain that spin affects a star’s magnetic field, which is born from hot plasma flowing inside the star’s core, creating the differences seen in nearby stars other than our sun. It turns out that the so-called “grand minima” that our sun experiences—like the long-ago Maunder minimum—may not be uniform across all stars.
Observations from the past 50 years all point to one trend: that more active stars tend to rotate faster. The new simulations provide a physical explanation for this trend and “confirm the suspected link between a faster rotation and more active stellar cycle,” according to Ryan French, an astronomer at the National Solar Observatory not affiliated with the publication.
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