# The Naked Scientists Forum

### Author Topic: Where does the Sun's magnetic field come from?  (Read 1911 times)

#### Spacetectonics

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##### Where does the Sun's magnetic field come from?
« on: 17/05/2013 09:37:44 »
Hi,

Just looking for a user friendly definition of what causes sun magnetic field please,I have searched and the results doesn't looks like consistence! ???

http://www.ucl.ac.uk/news/news-articles/1210/01102012-Loopholes-discovered-in-Suns-magnetic-belt

http://sunearthday.nasa.gov/2008/TTT/60_magfield.php

Thanks

#### yor_on

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##### Re: Where does the Sun's magnetic field come from?
« Reply #1 on: 18/05/2013 15:35:26 »
This one confuses me :)
http://solarphysics.livingreviews.org/Articles/lrsp-2005-7/articlese7.htm
I'm not discussing the treatment of the mathematics, but they build on magnetic null points.
Have we experimental proof for that, or is it theory?

Seems it is plasma physics, meaning very high temperatures needed for it.
http://www-solar.mcs.st-andrews.ac.uk/~eric/PAPERS/pontinfan.pdf

#### Pmb

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• Physicist
##### Re: Where does the Sun's magnetic field come from?
« Reply #2 on: 18/05/2013 23:59:14 »
Quote from: Spacetectonics
Hi,
Howdy! :)

Quote from: Spacetectonics
Just looking for a user friendly definition of what causes sun magnetic field please, ..
The magnetic field of the sun is generated by charges in motion, namely positively charged ions. Try looking at this one How does the Sun's magnetic field work?
at http://ibex.swri.edu/students/How_does_the_Sun.shtml
Quote
How does the Sun's magnetic field work?
The sun has a large and complex magnetic fieldA field of force that is generated by electric currents. The Sun's average large-scale magnetic field, like that of the Earth, exhibits a north and a south pole linked by lines of magnetic force..

Magnetic fields are created by things that are magnetic (like iron magnets) or by moving charged particles. A magnetic field is the description of the force a magnetic object exerts in the space surrounding the magnetic object. A force is a push or pull. To learn more about forces and magnetic fields, please visit The University of Colorado Physics 2000 website.

When charged particles move around really fast they create magnetic fields. The Sun is made of positively charged ionsAn atom that has become electrically charged by the gain or loss of one or more electrons. and negatively charged electronsA negatively charged elementary particle that normally resides outside (but is bound to) the nucleus of an atom. in a state of matter called plasmaPlasma consists of a gas heated to sufficiently high temperatures that the atoms ionize. The properties of the gas are controlled by electromagnetic forces among constituent ions and electrons, which results in a different type of behavior. Plasma is often considered the fourth state of matter (besides solid, liquid, and gas). Most of the matter in the Universe is in the plasma state.. Since the Sun is made of charged particles, magnetic fields are created by the movement of the particles.

The Sun's charged particles move in three ways due to the Sun's high temperatures and the movement of its axis, which influence each other to make the Sun's magnetic field complex:

The Sun's high temperatures cause the positively charged ions and negatively charged electrons that make up its plasma to move around a lot. The moving plasma creates many complicated magnetic fields that twist and turn.
The extremely hot plasma that blows off the Sun as the solar windA stream of charged particles, mostly protons and electrons, that escapes into the Sun's outer atmosphere at high speeds and streams out into the solar system. also causes a magnetic field.
The plasma in the Sun also rotates around the Sun's axis. The plasma near the poles rotates slower than the plasma at the equator causing twisting and stretching of magnetic fields, too.

#### yor_on

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##### Re: Where does the Sun's magnetic field come from?
« Reply #3 on: 19/05/2013 13:50:33 »
Well, yes, that's how I thought too, then, on the other hand I didn't expect magnetism to 'take out' magnetism, if I'm reading it right, creating null points? It's like if we have a field with empty spots in..

"In this study, the researchers found evidence that the magnetic web around the equator can consist of null points. Null points are interesting features and even though they are effectively empty regions, magnetic fields can pass through them. As the magnetic fields pass through they experience a change that turns them from being closed structures to open structures. During this process, gases can then be transported high enough to escape along these open magnetic structures that act as chimneys sending the gases of the solar atmosphere into the solar system."

Tried to find one single experimental proof made on Earth for it but couldn't?  Could be the extreme temperatures naturally, but still, that one was a surprise for me.

#### yor_on

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##### Re: Where does the Sun's magnetic field come from?
« Reply #4 on: 19/05/2013 13:58:44 »
==

Reading that again, it makes no sense at all btw.
Maybe this will make it clearer.

" Coronal activity such as ﬂares, eruptions and general heating is often attributed to the manner in which the coronal ﬁeld responds to photospheric motions. A very powerful tool to understand where the energy could be deposited is to study the magnetic topology of the active region, since it deﬁnes where magnetic reconnection is expected to occur (see the reviews of De´moulin, 2005; Longcope, 2005). The majority of the pioneer investigations considered a simpliﬁed two-dimensional geometry in which magnetic reconnection occurred at an isolated X-point or magnetic null point (Sweet, 1958). Field lines passing at the X-point deﬁned two separatrices.

Baum and Bratenahl (1980) revisited this idea and proposed a 3D quadrupolar conﬁguration, where two separatrix surfaces intercept along a single ﬁeld line called the separator (which joins two magnetic null points). Magnetic reconnection does not occur only at the null points but rather along the separator in the corona. Many papers have appeared based on this 3D approach to explain ﬂares (De´moulin et al., 1993; Mandrini et al., 1995), see De´moulin (2005) for a review. The locations of ﬂare ribbons are understood when the separatrices are found in magnetic conﬁgurations modeled with sub-photospheric sources."

Not saying it will this time either though :)  But? How and why do we get null points, at what temperatures can you expect them, and can we see it on Earth too, if so?
=

For magnetic reconnection this one makes sense http://www.answers.com/topic/magnetic-reconnection But I can't see any 'breaks' in it? Are there??

"According to simple resistive magnetohydrodynamics (MHD) theory, reconnection happens because the plasma's electrical resistivity near the boundary layer opposes the currents necessary to sustain the change in the magnetic field. The need for such a current can be seen from one of Maxwell's equations.

The resistivity of the current layer allows magnetic flux from either side to diffuse through the current layer, cancelling out flux from the other side of the boundary. When this happens, the plasma is pulled out by magnetic tension along the direction of the magnetic field lines. The resulting drop in pressure pulls more plasma and magnetic flux into the central region, yielding a self-sustaining process."

Not magnetic null points at all then?
It's a tricky one to understand.
« Last Edit: 19/05/2013 14:12:02 by yor_on »

#### The Naked Scientists Forum

##### Re: Where does the Sun's magnetic field come from?
« Reply #4 on: 19/05/2013 13:58:44 »