Charge on the sun

twofish-quant

This is a cool problem set question. If you work out the numbers, then it turns out that at anything larger than atomic scales, things are electrically neutral. There's an equlibrium length and an equlibrium time

http://farside.ph.utexas.edu/teachin...res/node7.html (Debye length)

http://farside.ph.utexas.edu/teachin...res/node6.html (plasma frequency)

Both are at the atomic scale.

Dotini

Perhaps there is a controversy as to the existence of electric fields in astrophysical objects?
I am easily able to find numerous references to ongoing research in seminars, current and planned NASA missions to study electric fields on the sun and in Earth's magnetosphere.
http://sprg.ssl.berkeley.edu/seminars_091311.html
http://solar.physics.montana.edu/qiu...on/apj_acc.pdf
http://www.nasa.gov/mission_pages/rb...tmosphere.html
http://mms.gsfc.nasa.gov/mission_details.html
http://naca.larc.nasa.gov/search.jsp...9%2B4294768863
http://ntrs.nasa.gov/search.jsp?R=20120007487

Even to a retiree/hobbyist like me, it seems to be the most basic science that if you want to accelerate a charged particle, the easiest and most obvious way to do it is with an electric field. If there is doubt or debate as to electric fields in space, it would be appreciated if both sides of the argument could be (politely) discussed here at PF, the most respected physics discussion board in the internet.

Respectfully submitted,
Steve

tasp77

Hope I remember this correctly,

Asimov calculated in one of his excellent science essays around a pound (love those English measures) of electrons somehow removed from earth and added to the sun would drastically alter the earth's orbit from around it.

I think as alluded to earlier in the thread, Asimov was just emphasizing the strength of the charge of the electron compared to the strength of gravity.

Despite the suns energy and turbulence, it would have to be electrically neutral or as noted, we would measure significant effects.

twofish-quant

No controversy, just someone in physics forums (me) misremembering stuff and explaining things badly.

What I was misremembering was that in the MHD approximation, charge cancellation causes the electric field in the rest frame of the fluid as zero,

http://math.nyu.edu/mfdd/strauss/fem7pl/node2.html

However in another frame of reference, that results in an electric field. Also, the MHD approximation will tend to generate magnetic fields that are large enough so that the approximation will break down.

This is different from asking if the sun is charged.

The thing about electric and magnetic fields is that they are interchangeable. Relativity says that whether something is magnetic or electric depends on the frame of the observer. The MHD approximation says that you have zero electric field in the frame of the fluid, but since the fluid is moving that gives you electric fields in another frame.

vociferous

That is interesting because my first instinct is that the sun might reach a positively charged equilibrium state due to the mass difference of electrons and protons.

However, it seems that the mass difference is accounted for in the electrons having a greater rms speed instead. This seems odd to me because I would assume the escape velocity from the corona is the same for all particles, so I think there is something I am missing, as I know only a little about the inner-dynamics of a plasma in a gravitational field.

twofish-quant

EM is *much* stronger than gravity, so even if gravity tells electrons that they can escape, EM keeps them from doing so. Electrons have a much higher rms than protons because they are lighter, but EM is strong enough to prevent charge separation.

Brett32324

I believe those particles are one of the keys to anti-gravity technologies and reversing the force of gravity in general...

Drakkith

This is not possible if our current understanding of nature is accurate, and discussions of anti-gravity are not allowed on PF per the rules.