3
$\begingroup$

This is an excerpt from BBC Infrared Telescope, published 27th July 2016

Jupiter's Great Red Spot - a hurricane three times bigger than Earth - is blasting the planet's upper atmosphere with heat, astronomers have found. Using measurements from an infrared telescope in Hawaii, a UK and US team found evidence for temperatures as high as 1,500C - hundreds of degrees warmer than anywhere else on the planet.

They suggest the hotspot is created by thunderous soundwaves "breaking" in the thin upper reaches of the atmosphere.

It arguably solves what planetary scientists had dubbed an "energy crisis" for gas giants like Jupiter: temperatures in their upper atmospheres soar much higher than can be explained by solar energy - especially given their vast distances from the Sun.

enter image description here

The heat from the Great Red Spot is the white smudge lower down, on the center line.

The mechanism of heat transfer is (very) roughly illustrated by the drawing below.

enter image description here

My question is: could a similar acoustic energy transfer explain the fact that the solar chromosphere, transition region, and corona are much hotter than the surface of the Sun. The reason is not currently well understood, but evidence suggests that Alfvén waves may have enough energy to heat the corona.

From Wikipedia Solar Corona

Above the temperature minimum layer is a layer about 2,000 km thick, dominated by a spectrum of emission and absorption lines. The temperature of the chromosphere increases gradually with altitude, ranging up to around 20,000 K near the top. 

Improve this question
$\endgroup$
3
  • $\begingroup$ Is Jupiter a strongly magnetized ball of extremely well conducting plasma? Not really. $\endgroup$
    – CuriousOne
    Jul 28, 2016 at 0:56
  • $\begingroup$ @CuriousOne admittedly en.m.wikipedia.org/wiki/Helioseismology is not very encouraging re acoustic activity $\endgroup$
    – user108787
    Jul 28, 2016 at 1:28
  • $\begingroup$ The problem is not the sonic activity, but the magnetic field and its interaction with the plasma. I am not a strong believer in handwaving explanations for complex things. Sometimes what happens in systems is really tough to explain... I would say these are grand examples of that phenomenon. $\endgroup$
    – CuriousOne
    Jul 28, 2016 at 1:33

1 Answer 1

Reset to default
1
$\begingroup$

Acoustic heating of the solar corona is an old idea that was ruled out some time ago. The idea was that acoustic waves would be generated by convective motions, propogate outwards and then dissipate in shocks. There is plenty of mechanical energy available in the convection zone, but the difficuly is that the shock dissipation appears to be insufficient to raise the temperature of the corona to more than $10^6$ K and the dissipation would occur to soon at low heights to explain the extended corona. Acoustic waves would also not explain the strong correlation between magnetic phenomena and coronal radiative losses seen in the Sun and other stars.

Instead it is believed that heating is predominantly via the dissipation of magnetic energy that is propagated into the corona either through the stressing of magnetic loop footpoints by motions in the photosphere and subsequent reconnection events, or by the generation of magnetic (MHD) waves - magneto-acoustic or Alfven waves - that are a little more readily able to propagate into the thin coronal plasma.

There is a reasonable discussion of models of coronal heating at https://en.m.wikipedia.org/wiki/Corona#Coronal_heating_problem .

Improve this answer
$\endgroup$
1
  • $\begingroup$ Thank you very much Rob, it was the first thing that came to mind when I read about Jupiter. $\endgroup$
    – user108787
    Jul 28, 2016 at 8:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.