Sun Experiences Seasonal Changes Just Like Earth

It turns out that the sun undergoes a type of seasonal variability with its activity waxing and waning over the course of nearly two years. The findings reveal a bit more about the 11-year cycle of the sun.

"What we're looking at here is a massive driver of solar storms," said Scott McIntosh, lead author of the new study, in a news release. "By better understanding how these activity bands form in the sun and cause seasonal instabilities, there's the potential to greatly improve forecasts of space weather events."

The overlapping bands are fueled by the rotation of the sun's deep interior. As the bands move within the sun's northern and southern hemispheres, activity rises to a peak over a period of about 11 months and then begins to wane.

"Much like Earth's jet stream, whose warps and waves have had severe impact on our regional weather patterns in the past couple of winters, the bands on the sun have very slow-moving waves that can expand and warp it too," said Robert Leamon, one of the researchers. "Sometimes this results in magnetic fields leaking from one band to the other. In other cases, the warp drags magnetic fields from deep in the solar interior, near the tachocline, and pushes them toward the surface."

The findings are published in the journal Nature Communications.

These quasi-annual variations can be likened to regions on Earth that have two seasons, such as a rainy season and a dry season. These variations are driven by changes in the bands of strong magnetic fields in each solar hemisphere, and these bands shape the 11-year cycle.

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