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scpg02

Scientists find elusive waves in sun's corona

Scientists find elusive waves in sun's corona

Discovery can help unlock secrets of corona's heat, solar storms


Quote:
BOULDER--Scientists for the first time have observed elusive oscillations in the Sun's corona, known as Alfvén waves, that transport energy outward from the surface of the Sun. The discovery is expected to give researchers more insight into the fundamental behavior of solar magnetic fields, eventually leading to a fuller understanding of how the Sun affects Earth and the solar system.

The research, led by Steve Tomczyk of the National Center for Atmospheric Research (NCAR), is being published this week in Science.

"Alfvén waves can provide us with a window into processes that are fundamental to the workings of the Sun and its impacts on Earth," says Tomczyk, a scientist with NCAR's High Altitude Observatory.


http://www.eurekalert.org/pub_releases/2007-08/ncfa-nns082707.php

Contact: David Hosansky
hosansky@ucar.edu
303-497-8611

Rachael Drummond
rachaeld@ucar.edu
303-497-8604

Steve Tomczyk
tomczyk@ucar.edu
303-497-1579

National Center for Atmospheric Research/University Corporation for Atmospheric Research
NileQueen

Thanks for the news Maggie. It has been a mystery why the corona is so much hotter than the surface of the sun. Maybe they will find out the reason for that too.
sneez

Which is funny quite interesting because thermodynamics says that heat can flow from hot to cold objects ONLY otherwise work must be done on the system to reverse the flow.
NileQueen

Perhaps like ice worms on glaciers, there are solar maggots or something doing some work Razz
scpg02

I heard somewhere that the corona is very loud. They were speculating that the sound is actually heating the corona.
sneez

There is evidence of sound waves propagating in the sun itself (bellow the photosphere) and sounds traveling outwards as well.

However there exists a relativelly dense plasma above the photosphere (the layer which is the black body approximated to 6000K). The so called corona.

If sound waves indeed heat this layer it does not explain why its trapped in the corona. And still the (thrmal) heat in that plasma (i suppose, im not plasma physicist) must go from hot to cold, hence it must heat the sun photosphere as well as the cold space. All articles I found on this totally ignore this fact that hot corona must heat the bellow photophsere. While its acknowladged as paradox, its not taken into account, as far as my knowledge goes, when accounting for how it evolved to be so.

Quote:

NASA facts (1998)
The corona is constantly changing becausethe magnetic fields that dominate the coronaare continuously displaced by convectivemotions in the outer layers of the Sun justbelow the photosphere. An apparent paradox,the corona is much hotter than the solar sur-face, at up to three million degrees Fahrenheit.Many scientists suspect that the Sun has amechanism for converting its magnetic energyto thermal (heat) energy in the corona, but thedetails are not understood well.


Im not sure why its called apparent paradox. I fully admit my ignorance of the details if somebody has some, but I do have quite well working knowledge of thermodynamics in close to ideal gas approximation (i.e. atmosphere)
Baywax

The sun has been heating ever up since the industrial revolution started and we just better do something about it..... I'm cereal.... super cereal.

Shocked
sneez

Thought: On Earth the thermosphere is much hotter than surface. According to thermodynamics the heat should flow from hot to cold, hence aparent! pradox?

Well, given the low pressure of at thermospheric altitudes its hard to really think of it as tempereature in the same sense as at the surface. One thing to note, without the sun, earth's thermosphere would not have these high kinetic energy species which we interpret as temperature for convenience. It is the solar UV, and X-rays + particles in solar wind that ionize and highly excite the thermospheric region.

Sun's corona is also very tenuous, however, there is no external source to excite (kinetically) the particles as we move farther away from sun's "surface", and we would, therefore, expect that "temperature" of corona should by lower. I think the same explanation does not apply for sun as applies for earth. On the other hand I think the statement I made and which is usually made concerning this issue is wrong as well. There is no violation of heat flow from sun surface to the corona, the corona is for practical purposes much cooler. What I mean is given in the explanation of earth's thermosphere temperature.

Does this sound consistent?

(hence, there must be process that excites sun's corona region to high kinetic energies).

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