UCLA: The Sun's Core Rotates Four Times Faster Than Its Surface

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UCLA: The Sun's Core Rotates Four Times Faster Than Its Surface

Postby bystander » Wed Aug 02, 2017 4:55 pm

The Sun's Core Rotates Four Times Faster Than Its Surface
University of California, Los Angeles | 2017 Aug 01

Surprising observation might reveal what the sun was like when it formed

The sun’s core rotates nearly four times faster than the sun’s surface, according to new findings by an international team of astronomers. Scientists had assumed the core was rotating like a merry-go-round at about the same speed as the surface. ...

The rotation of the solar core may give a clue to how the sun formed. After the sun formed, the solar wind likely slowed the rotation of the outer part of the sun, he said. The rotation might also impact sunspots, which also rotate, Ulrich said. Sunspots can be enormous; a single sunspot can even be larger than the Earth.

The researchers studied surface acoustic waves in the sun’s atmosphere, some of which penetrate to the sun’s core, where they interact with gravity waves that have a sloshing motion similar to how water would move in a half-filled tanker truck driving on a curvy mountain road. From those observations, they detected the sloshing motions of the solar core. By carefully measuring the acoustic waves, the researchers precisely determined the time it takes an acoustic wave to travel from the surface to the center of the sun and back again. That travel time turns out to be influenced a slight amount by the sloshing motion of the gravity waves ...

Asymptotic g modes: Evidence for a rapid rotation of the solar core - E. Fossat et al
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Re: UCLA: The Sun's Core Rotates Four Times Faster Than Its Surface

Postby MargaritaMc » Wed Aug 02, 2017 5:43 pm

http://m.esa.int/Our_Activities/Space_Science/Space_Science/Gravity_waves_detected_in_Sun_s_interior_reveal_rapidly_rotating_core
GRAVITY WAVES DETECTED IN SUN’S INTERIOR REVEAL RAPIDLY ROTATING CORE
[...]
Just as seismology reveals Earth’s interior structure by the way in which waves generated by earthquakes travel through it, solar physicists use ‘helioseismology’ to probe the solar interior by studying sound waves reverberating through it. On Earth, it is usually one event that is responsible for generating the seismic waves at a given time, but the Sun is continuously ‘ringing’ owing to the convective motions inside the giant gaseous body.

Higher frequency waves, known as pressure waves (or p-waves), are easily detected as surface oscillations owing to sound waves rumbling through the upper layers of the Sun. They pass very quickly through deeper layers and are therefore not sensitive to the Sun’s core rotation.

Conversely, lower frequency gravity waves (g-waves) that represent oscillations of the deep solar interior have no clear signature at the surface, and thus present a challenge to detect directly.

In contrast to p-waves, for which pressure is the restoring force, buoyancy (gravity) acts as the restoring force of the gravity waves.

“The solar oscillations studied so far are all sound waves, but there should also be gravity waves in the Sun, with up-and-down, as well as horizontal motions like waves in the sea,” says Eric Fossat, lead author of the paper describing the result, published in Astronomy & Astrophysics. “We’ve been searching for these elusive g-waves in our Sun for over 40 years, and although earlier attempts have hinted at detections, none were definitive. Finally, we have discovered how to unambiguously extract their signature.”

[...] “Although the result raises many new questions, making an unambiguous detection of gravity waves in the solar core was the key aim of GOLF. It is certainly the biggest result of SOHO in the last decade, and one of SOHO’s all-time top discoveries,” says Bernhard Fleck, ESA’s SOHO project scientist.

ESA’s upcoming solar mission, Solar Orbiter will also ‘look’ into the solar interior but its main focus is to provide detailed insights into the Sun’s polar regions, and solar activity. Meanwhile ESA’s future planet-hunting mission, Plato, will investigate seismic activity in stars in the exoplanet systems it discovers, adding to our knowledge of relevant processes in Sun-like stars.


I've not embedded an image showing the p- and q-waves because I've forgotten how to do it, but here is a link to the image.
http://m.esa.int/spaceinimages/Images/2 ... r_interior
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Re: UCLA: The Sun's Core Rotates Four Times Faster Than Its Surface

Postby neufer » Thu Aug 03, 2017 5:08 pm

https://en.wikipedia.org/wiki/Structure ... Earth#Core wrote:
<<In August 2005 a team of geophysicists announced in the journal Science that, according to their estimates, Earth's inner core rotates approximately 0.3 to 0.5 degrees per year faster relative to the rotation of the surface.>>
Art Neuendorffer

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Re: UCLA: The Sun's Core Rotates Four Times Faster Than Its Surface

Postby Case » Fri Aug 04, 2017 2:31 am

Click to play embedded YouTube video.
neufer wrote:<<In August 2005 a team of geophysicists announced in the journal Science that, according to their estimates, Earth's inner core rotates approximately 0.3 to 0.5 degrees per year faster relative to the rotation of the surface.>>

In 2010, Blue Sky Studios visualised a rapidly rotating inner core, instigated by a prehistoric squirrel named Scrat, and that in turn causing a large scale crack-up of sorts. :wink:


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