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posted by martyb on Tuesday February 07 2017, @12:46PM   Printer-friendly
from the and-the-Sun-bakes-us dept.

The Sun's surface mysteriously rotates more slowly than its interior. Now researchers have observed the phenomenon with high resolution and proposed an explanation for the behavior. Using a new technique that tracks waves moving through the outer layers of the Sun, the team confirmed the speed difference and attributed the slowdown to the Sun's outer, 70-km "skin." Their model proposes that photons radiated from this layer extract angular momentum, slowing down the rotation. According to the researchers, such a slowdown should occur in all stars and could have a greater effect on larger stars.

The rotation rate of the Sun's plasma varies with latitude—faster at the equator than at the poles—and with distance from the core. Solar researchers noticed the core-surface speed difference decades ago but do not yet have a widely-accepted explanation.

Editorial summary

PRL Article

This rotational anomaly has been implicated in solar flares... so nice to know the cause.


Original Submission

 
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  • (Score: 1, Informative) by Anonymous Coward on Tuesday February 07 2017, @09:53PM

    by Anonymous Coward on Tuesday February 07 2017, @09:53PM (#464316)

    There is a relativistic effect called the Poynting-Robertson force that causes dust rotating about a star to suffer a drag as the result of the light from the star. This paper argues that the observed differential rotation can be described as the effect of a torque on the outer layers of the photosphere, and they note that the form of the equation for the tangential component of the radiated photons is in the same form as the Poynting-Robertson force equation. They integrate the torque on the solar surface and come up with a magnitude that is consistent with what is observed.

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