NASA SDO Unravels Writhing, Internal Motion of the Sun

NASA's Solar Dynamics Observatory has learned a little bit more about the sun. Using the Helioseismic and Magnetic Imager (HMI) instrument, scientists have discovered what internal, writhing motions drive our nearest star.

It's important to understand what processes cause our sun to act the way it does. This star is a major source of space weather as it slings coronal mass ejections and solar particles toward Earth. More specifically, learning about the internal system of the sun could improve predictions of the intensity of the next solar cycle.

Scientists have been using the SDO for years, examining a fantastic display of explosions and fountains on the solar surface. Yet all of these processes are driven by the internal, complex and ever-changing magnetic current beneath the sun's surface. Known as the dynamo, this magnetic system flips approximately every 11 years--the peak of the solar cycle.

"For decades people have known that the solar cycle depends on the poleward flow or material, changing the magnetic fields one cycle to the next," said Philip Scherrer, one of the researchers, in a news release. "We mapped out what we believed to be the flow pattern in the 1990s, but the results didn't quite make sense."

The researchers examined two years-worth of data from HMI, which observed the sun continuously with 16 times more detail than the best previous helioseismology instruments. The scientists then compared the helioseismology results measured at four different heights within the sun's surface. Surprisingly, the results weren't consistent with what the normal convention would expect.

So what did the researchers find? It turns out that instead of a simple cycle of flow moving toward the poles near the sun's surface and back to the equator, the material inside the sun shows a double layer of circulations; the two cycle on top of each other.

"This has important consequences for modeling the solar dynamo," said Junwei Zhao, one of the researchers, in a news release. "We hope our results on the sun's interior flow will provide a new opportunity to study the generation of solar magnetism and solar cycles."

The findings could allow researchers to better understand the 11-year solar cycle. In addition, it could allow scientists to predict exactly when solar activity will increase in the future.

The findings are published in the Astrophysical Journal Letters.