From a University College, London Press Release – Solar winds triggered by magnetic fields
Solar wind generated by the sun is probably driven by a process involving powerful magnetic fields, according to a new study led by UCL researchers based on the latest observations from the Hinode satellite.
Scientists have long speculated on the source of solar winds. The Extreme Ultraviolet Imaging Spectrometer (EIS), on board the Japanese-UK-US Hinode satellite, is now generating unprecedented observations enabling scientists to provide a new perspective on the 50-year old question of how solar wind is driven. The collaborative study, published in this month’s issue of Astrophysical Journal, suggests that a process called slipping reconnection may drive these winds.
Deb Baker, lead author from UCL Mullard Space Science Laboratory, says: “Solar wind is an outflow of million-degree gas and magnetic field that engulfs the Earth and other planets. It fills the entire solar system and links with the magnetic fields of the Earth and other planets. Changes in the Sun’s million-mile-per-hour wind can induce disturbances within near-Earth space and our upper atmosphere and yet we still don’t know what drives these outflows.”
“However, our latest study suggests that it is the release of energy stored in solar magnetic fields which provides the additional driver for the solar wind. This magnetic energy release is most efficient in the brightest regions of activity on the Sun’s surface, called active regions or sunspot groups, which are strong concentrations of magnetic field. We believe that this fundamental process happens everywhere on the Sun on virtually all scales.”
Images taken in February 2007 from the EIS instrument showed that hot plasma outflows are due to a process called slipping reconnection. At the edges of active regions where this process can occur, a slow, continuous restructuring of the magnetic field leads to the release of energy and acceleration of particles in the Sun’s hot outer atmosphere, known as the corona. Slipping reconnection is the first theory to explain how observed outflows from the Sun can be located over areas of a single magnetic sign, something previously considered improbable.
Computer models of the Sun’s magnetic field were used to identify regions where slipping reconnection could occur. The locations proposed by the computer model were compared with measurements of the speed of the gas coming from the solar corona. The comparison showed the gas was moving outward at up to 100,000 mph, 1,000 times the wind speed in a hurricane, over the possible slipping reconnection regions.
The study was carried out by the UCL Mullard Space Science Laboratory, Observatoire de Paris, Konkoly Observatory in Hungary and Instituto de Astronomía y Física del Espacio in Argentina. Deborah Baker is funded by a Science and Technology Funding Council (STFC) studentship.
Hinode is a Japanese mission developed and launched by the Institute of Space and Astronautical Science (ISIS) and Japanese Aerospace Exploration Agency (JAXA), with the National Astronomical Observatory of Japan (NAOJ) as domestic partner and NASA and STFC (UK) as international partners. It is operated by these agencies in co-operation with the European Space Agency (ESA) and Norwegian Space Centre (NSC).
Data that served as the basis for the magnetic modelling was provided by the Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) consortium. SOHO is a project of international cooperation between ESA and NASA.
See the Research paper in The Astrophysical Journal
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This is all old news…
I’m sure Leif has something to say.
an outflow of million-degree gas and magnetic field… OK
the Sun’s million-mile-per-hour wind… ?
Moderator, disregard 18:19:51,
Thanks
Everything that happens on our little planet depends on the energy that comes from that big yellow sphere that shows up in the sky every morning. We should try to understand as much as possible about it.
the_Butcher (17:40:39) :
This is all old news…
I’m sure Leif has something to say.
Indeed. The study reaffirms the generally accepted idea that magnetic reconnection is responsible for releasing the energy stored in the magnetic field [we are now down to discussing the details of that universal process]. As a result of magnetic reconnection, strong electric currents are generated. Dissipation of these currents [think light bulb or electric stove] heats the corona and drives the wind. One can even put a number on the process: one Weber of magnetic flux provides 600 kW of power to drive the solar wind, e.g. http://www.iop.org/EJ/abstract/1538-4357/686/1/L33
It is interesting that this might explain the observed ‘floor’ in the heliospheric magnetic field. If there is a solar wind at all, it must flow with a speed greater than ~250 km/sec [otherwise it could not escape the Sun’s gravity]. So, since there is a minimum speed, there must also be a minimum flux necessary to provide at least that speed.
I don’t know plasma. Is reconnection like (or similar to) a pinch?
fred (19:05:12) :
I don’t know plasma. Is reconnection like (or similar to) a pinch?
No, when two plasma regions with oppositely directed magnetic fields are brought or pressed together by movements of the plasma, the magnetic field at the boundary between the two polarities can change a lot. A changing magnetic field generates an electric current [used in almost all power stations and in an old-fashioned bicycle lamp dynamo]. A current passed through a medium heats the material. Hot stuff expands, and, voila, you have an expanding solar atmosphere that we call the ‘solar wind’. Even if the two regions do not have oppositely directed fields, but just fields of different strengths, you can still induce currents [this is the ‘slipping’ reconnection mentioned in the article].
Are solar flares just an extreme version of this reconnection?
Carbone (19:31:31) :
Are solar flares just an extreme version of this reconnection?
Yes, and solar flares come in all sizes. The smallest one are not extreme at all, probably can’t even be seen above the background noise. Here is more on weak flares: http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/RHESSI_microflares_-_Flare_Cartoons_and_Reality
and here we ask” ‘where are the flares?’
http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Where_are_the_flares
Leif Svalgaard (19:18:43) : “… and in an old-fashioned bicycle lamp dynamo…
Now you’re talking my language and my time, Leif!
Using this as a starting point I may even be able to catch up and understand a little of what at present I can only read here on WUWT with wonder, awe and amazement…
Would the Suns velocity traveling around the galaxy have any effect on ‘solar wind’ ?
David Alan (20:10:27) :
Would the Suns velocity traveling around the galaxy have any effect on ’solar wind’ ?
Not as such. The Sun is embedded in the ‘local cloud’ of interstellar medium and sees only that, even though the cloud [and the Sun] may be in orbit around the Galactic center. When you are bicycling and have a headwind, you don’t really feel that the Earth is rotating, orbiting the Sun, orbiting the Galaxy, expanding space, etc. The speed relative to the local cloud is 30 km/sec, but the solar wind blows at 400 km/sec, so in the inner solar system, the solar wind basically excludes the interstellar medium. At the outer boundary of the heliosphere there will be some deformation due the the ‘collision’ between the two media. This process is largely unknown, although Voyagers and IBEX have given us glimpses.
Solar wind is caused by electromagnetic forces, and so is visible light. How closely related (if at all) are the solar wind and light?
Does the material out of which the Sun formed having an iron content from previous stellar fusion (of 1st gen stars) have anything to do with it’s field? i.e. – if the Sun was formed solely from Hydrogen and Helium of the young universe, would it still have a magnetic field?
@ur momisugly rbateman
‘When a star has fused all of its hydrogen into helium, it begins fusing the helium into lithium, and so on up the periodic table. If a star is massive enough, it will produce elements all the way up to iron.’
source: http://www.ssg.sr.unh.edu/ism/history.html
Not sure if that answers your question.
Bob Shapiro (22:10:41) :
Solar wind is caused by electromagnetic forces, and so is visible light. How closely related (if at all) are the solar wind and light?
No, the solar wind is formed because the solar corona is HOT. And has nothing to do with electromagnetism or visible light. No more than your chicken fried steak is formed by electromagnetic forces.
rbateman (22:15:52) :
Does the material out of which the Sun formed having an iron content from previous stellar fusion (of 1st gen stars) have anything to do with it’s field? i.e. – if the Sun was formed solely from Hydrogen and Helium of the young universe, would it still have a magnetic field?
The ‘metals’ [even though only 1% of the sun] are important by supplying easy-to-pry-loose electrons and so are important for the internal structure of the Sun that depends on the opacity supplied by electrons. A first generation star would probably still have a magnetic field, and activity cycles, but this is still a research area and the opinions are a bit divided how large these fields would be. Something called the Biermann battery effect [google it] could help generate the magnetic field as a seed for the dynamo process. Once you got a magnetic field, from then on it is very hard to get rid off, and dynamo processes will keep regenerating and amplifying the field.
Bob Shapiro (22:10:41) :
Solar wind is caused by electromagnetic forces, and so is visible light. How closely related (if at all) are the solar wind and light?
No, the solar wind is formed because the solar corona is HOT. And has nothing to do with electromagnetism or visible light. No more than your chicken fried steak is formed by electromagnetic forces.
Thanks for the information, Leif.
Leif: Thanks for an explanation much clearer and relevant than the press release. Why can’t press releases be written in a language that the layman can understand, since it is laymen (and laywomen to be PC) and media numpties who read press releases? The explanation of “slipping reconnection” in the press release as “the release of energy stored in solar magnetic fields” barely scratches the surface.
David Alan (22:41:20) :
I am aware of the fusion process to iron, after which it takes (super)nova implosion to go any further up the periodic table. Your answer will no doubt help some readers who are not aware of how our Solar System (and Sun) got heavier elements into it.
Leif Svalgaard (23:09:20) :
It’s not often we bump into the frontieres of theory.
I like your explanation with the metal-supplied electrons.
I’ll check out the Biermann process.
There are still some unresolved questions relating to ‘magnetic reconnection’.
“This magnetic energy release is most efficient in the brightest regions of activity on the Sun’s surface, called active regions or sunspot groups, which are strong concentrations of magnetic field. We believe that this fundamental process happens everywhere on the Sun on virtually all scales.”
There is a contradiction here. If it is ‘reconnection’ current that heats up the solar corona than highest temperature should be in vicinity of such reconnection. However fact is that further we get away from
‘the Sun’s surface, called active regions or sunspot groups, which are strong concentrations of magnetic field.’
higher temperature it gets.
http://upload.wikimedia.org/wikipedia/commons/3/32/Sun_Atmosphere_Temperature_and_Density_SkyLab.jpg
I’m not a physicist, just curious… this made me think of magnetic mirrors and magnetic bottles (magnetic scissors)… The wiggling and vibrating of field lines would easily accelerate particles away from the sun.
We are talking about a plasma (the solar wind), that has magnetic and electric properties… doesn’t that mean that we have the equivalent of an electric circuit flowing out of the sun/solar system ? And if all these other stars are doing the same thing, doesnt that mean that we have a enormous amount of electric and magnetic energy flowing out from all the stars ? Where is it all going ?
I realise that as the solar wind expands from each star, it discipates and weakens to almost nothing – but multiply that “almost nothing” by 100billion stars, and you must still have enormous amounts of energy out there between the stars.
All of these currents WANT to go somewhere? Where ?
The solar system is a bit like a toy plasma ball. If you imagine the sun to be the centre of the plasma ball, and the solar wind is the pretty plasma arcs. The plasma arcs terminate on the glass of the plasma ball, and then go to ground/earth in the circuitry at the base of the plasma ball.
Where does all the electric/magnetic engergy from the stars go ?
It has to go somewhere ?
I`m not trying to imply plasma/electric universe stuff here – just asking the question ??
Leif – ‘the solar wind has nothing to do with electromagnetic forces’ –
I thought magnetic fields were implicated in the spatial distribution of the wind and also in the acceleration of protons and electrons even as the distance from the sun increased – wasn’t this the basis of the controversy with Hannes Alfven? Isn’t the solar wind one great electric current? How does it then interact with the ionospheric current sheet and the huge voltage difference between the top and bottom of the atmosphere – and does this have any implications for climate?
I ask this because I was struck by Svensmark’s experiments – when he cleared the gas chambers (looking for ionisation and nucleation) he used a voltage shock. When we get flares, is there a voltage shock? Could this affect charged particles and transparency of the atmosphere in relation to aerosols?
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Leif Svalgaard (23:09:20) :
rbateman (22:15:52) :
Does the material out of which the Sun formed having an iron content from previous stellar fusion (of 1st gen stars) have anything to do with it’s field? i.e. – if the Sun was formed solely from Hydrogen and Helium of the young universe, would it still have a magnetic field?
The ‘metals’ [even though only 1% of the sun] are important by supplying easy-to-pry-loose electrons and so are important for the internal structure of the Sun that depends on the opacity supplied by electrons. A first generation star would probably still have a magnetic field, and activity cycles, but this is still a research area and the opinions are a bit divided how large these fields would be.
*******
Leif, OT, but I’m intrigued by the thought of how a ~8+ solar-mass first generation star would evolve. Since there would be almost no opacity (and therefore little radiational heating) in the material around the fusing core, would the star “skip” all the usual stages of similar-mass, metal-rich stars, and very quickly go supernova or black-hole?