Solar magnetic resonance directly observed for the first time

Posted: August 26, 2015 by oldbrew in Solar physics
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A simulation of a cross-section of a thread of solar material, called a filament, hovering in the sun's atmosphere [image credit: NAOJ/Patrick Antolin]

A simulation of a cross-section of a thread of solar material, called a filament, hovering in the sun’s atmosphere
[image credit: NAOJ/Patrick Antolin]


Researchers find this works in ‘the same way that a perfectly-timed repeated push on a swing can make it go higher’, as Phys.org reports:

Modern telescopes and satellites have helped us measure the blazing hot temperatures of the sun from afar. Mostly the temperatures follow a clear pattern: The sun produces energy by fusing hydrogen in its core, so the layers surrounding the core generally get cooler as you move outwards—with one exception.

Two NASA missions have just made a significant step towards understanding why the corona—the outermost, wispy layer of the sun’s atmosphere —is hundreds of times hotter than the lower photosphere, which is the sun’s visible surface [aka the coronal heating problem]


In a pair of papers in The Astrophysical Journal, published on August 10, 2015, researchers—led by Joten Okamoto of Nagoya University in Japan and Patrick Antolin of the National Astronomical Observatory of Japan—observed a long-hypothesized mechanism for coronal heating, in which magnetic waves are converted into heat energy. Past papers have suggested that magnetic waves in the sun—Alfvénic waves – have enough energy to heat up the corona. The question has been how that energy is converted to heat.

“For over 30 years scientists hypothesized a mechanism for how these waves heat the plasma,” said Antolin. “An essential part of this process is called resonant absorption—and we have now directly observed resonant absorption for the first time.”

Resonant absorption is a complicated wave process in which repeated waves add energy to the solar material, a charged gas known as plasma, the same way that a perfectly-timed repeated push on a swing can make it go higher. Resonant absorption has signatures that can be seen in material moving side to side and front to back.

Full Phys.org report here: IRIS and Hinode: A Stellar research team.

Comments
  1. oldbrew says:

    Some technical stuff on resonance absorption here:
    http://www.britannica.com/science/resonance-absorption
    [click on ‘Electromagnetic radiation: Resonance absorption and recoil’]

    RESONANCE ABSORPTION AND RECOIL
    ‘During the mid-1800s the German physicist Gustav Robert Kirchhoff observed that atoms and molecules emit and absorb electromagnetic radiation at characteristic frequencies and that the emission and absorption frequencies are the same for a given substance. Such resonance absorption should, strictly speaking, not occur’ …[etc]

  2. oldbrew says:

    Related: from another phys.org report today – Dying star suffers ‘irregular heartbeats’

    ‘Astronomers are still trying to settle on an explanation for these never-before-seen outbursts. Given the similarity between the first two stars to show this behaviour, they suspect it might have to do with how the pulsation waves interact with themselves, perhaps via a resonance.’ [bold added]
    http://phys.org/news/2015-08-dying-star-irregular-heartbeats.html

    Is that a penny we can hear dropping?

  3. E.M.Smith says:

    So can magnetic resonance heat the Earth too? We hear all about solar wind and magnetic flux, what does it do when it gets here, resonately speaking?…

  4. E.M.Smith says:

    Er, can you fix that to fLux…
    [done]

  5. oldbrew says:

    Something to note re the ‘coronal heating problem’ is:
    ‘The chromosphere, the next layer of the sun’s atmosphere is a bit cooler — about 7,800 degrees F (4,320 degrees C).’
    then…
    ‘Temperatures rise dramatically in the corona, which can also only be seen during an eclipse as plasma streams outward like points on a crown. The corona can get about 3.5 million degrees F (2 million degrees C). As the corona cools, losing heat and radiation, matter is blown off as the solar wind.’

    Source: ‘How Hot is the Sun?’
    http://www.space.com/17137-how-hot-is-the-sun.html

    That’s a phenomenal increase in heat due – in part at least – to resonant absorption.
    Up to 460 times the starting temperature.

  6. oldbrew says:

    EM Smith says: ‘So can magnetic resonance heat the Earth too? We hear all about solar wind and magnetic flux, what does it do when it gets here, resonately speaking?’

    Coronal mass ejections are powerful things…’caused by release of magnetic energy at the Sun’.
    http://en.wikipedia.org/wiki/Solar_wind#Coronal_mass_ejection

  7. Oldbrew Kirchhoff’s law applies to “black bodies”. For a grey surface it has to be qualified, quote from Chemical Engineering Hand Book “in surroundings at its own temperature”. Eg a water surface can absorb visible light radiation from the sun but does not emit light (it does not have sufficient temperature) Also think of a near black piece of wrought iron. At 25C it appears near black because it does not reflect of emit light. Heat it to about 700C it will show some redness, heat to around 1000C it will appear orange to yellow and at around 1400C it will start to appear white ie emitting light.
    Now an off topic question. I have found this comment
    http://newmars.com/forums/viewtopic.php?id=7103
    This mentions the velocity of sound in an atmosphere and the lapse rate.
    Maybe you could put up a post so some of the experts, particularly other engineers could comment. Maybe it could lead to new understanding. Energy waves and sound waves in an atmosphere have similarities.

  8. tchannon says:

    That’s a very interesting snippet.

    I suppose I ought to have an interest after so many years in audio and in aerodynamics / hydrodynamics. Not something where I’ve paid much attention although there are some fun uses, a lot is about time delay, whole raft of effects.

    Wave limits are more extensive than just in a gas

  9. oldbrew says:

    cementafriend says: August 27, 2015 at 3:40 am

    Those comments seem more in the realm of the other thread:
    ‘Irradiance and surface pressure only match of rocky planet surface temperature’

    Speed of sound: ‘It is proportional to the square root of the absolute temperature, but is independent of pressure or density for a given ideal gas.’ – Wikipedia

    No mystery there?

  10. tchannon says:

    Helioseismology

    http://soi.stanford.edu/results/sspeed.html (1997 archive)

    And then looking similar to the article drawing here
    http://solarscience.msfc.nasa.gov/Helioseismology.shtml