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View Full Version : Someone knows Sunís electric capacity and Sunspot"s cha



czeslaw
2005-Jul-08, 10:10 AM
I canít find links about possible electrostatic capacity of the Sun and the net charge in Coulombs of its Sunspots according to their diameter.

czeslaw
2005-Jul-08, 06:00 PM
Nobody has seen links about Sun's electric capacity ?
Is it not measured still ?

Swift
2005-Jul-08, 06:03 PM
I can't speak for anyone else, but I don't know what you mean by the sun's "electric capacity". Are you suggesting the sun is a big capacitor that can hold a charge?

Laguna
2005-Jul-08, 06:17 PM
And where do you define the potential as zero?

czeslaw
2005-Jul-09, 08:00 AM
The clouds on the Earth are charged and we see flash of a lightning when it discharge. We do see flashes on the Sunís surface and there is ionized solar wind bent by Earthís magnetic field. The Sunís spots have strong magnetic field , doesnít mean they are charged ? Has a Sunís spot a potential electrostatic capacity ? Does it interact with an interstellar gaseous clouds ?
I can't find any links with numbers about it.

Fortis
2005-Jul-09, 04:12 PM
If you make the pretty gross assumption that the Sun is a conductive sphere of radius r_s, then its capacitance would be

C_s = 4.Pi.epsilon_0.r_s

Have a look at this page (http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capsph.html#c2).

czeslaw
2005-Jul-10, 11:52 AM
Thank you Fortis for this link.
According to this math , the capacity of the Sun is less then 1 Farad.
In this equation is epsylon "o" for vacuum. Do we need give there an additionally factor for Sun's stuff?
How many Coulombs of net charge could be in such a star like our Sun?
Charge = capacity x voltage

Karl
2005-Jul-10, 04:24 PM
If there were a net charge what would prevent the free ions/electrons in the interstellar medium from flowing to neutralize it? Or for that matter, why wouldn't there be a (short) imbalance in the net neutral solar wind that would neutralize it?

czeslaw
2005-Jul-10, 06:50 PM
A star is neutral usually, I think. There are Cosmic Rays (protons mainly) absorbed by the star. This radiation may cause a charge imbalance.

Karl
2005-Jul-10, 09:51 PM
Elecrons can also be cosmic rays.

Let's look at some numbers.

The solar wind is listed at a mass of 10 million tons per year.

http://csep10.phys.utk.edu/astr162/lect/sun/wind.html

That works out to about 287kg per second if my quick calculation was right.

One gram of hydrogen is one mole which when ionized is 96500 Coulombs.

That works out to about 3*10^11 amps each of electrons and protons.

Seems like plenty to neutralize a charge if there were one.

(Edit to correct units)

Laguna
2005-Jul-11, 07:10 AM
The capacity of a sphere is:

C = 4 * Pi * epsilon_r * epsilon_0 * r

Where epsilon_0 ist the dielectric constant with epsilon_0=8,854187817*10^-12 F/m, r is the Radius of the sphere
and epsilon_0 is a specific dimensionless constant that depends on the Material.
Assuming that the sun consists of hydrogen, epsilon_r would be 1,000252.

-> Capacity of the sun
C=0,15 F

czeslaw
2005-Jul-11, 09:04 AM
Thank you Karl, for very good link about Solar Wind.
There are Cosmic Rays coming from the Galaxy Space to our Solar System. http://hyperphysics.phy-astr.gsu.edu/hbase/astro/cosmic.html There are less then 1 % electrons and 99 % protons. This protons do charge our Sun , EarthÖ There are about 2500 protons/sm^2 coming to the Earth upper atmosphere. Every object could be charged till its electric capacity only.

Our Sun has magnetic field B =~ 50 Gs = 0,005 Tesla. The solar surface has average 5 Gs and Sunspots about 1000Gs. The planet Jupiter has B = 1000 Gs too. White Dwarf has 10^6 Gs, Neutron Star !0^12, Magnetar Star 10^15 Gs.

Magnetic field is caused by a circled charge. B=u(o)I/2piR . Magnetic field of 1000 Gs in Sunspots is caused by a current of about 10^13 A. There has to be a voltage pulling this 10^13 Coulombs/s. What causes this Sunspots voltage ?

There is a net charge trapped by the magnetic field , I think. The tension of the solar discharge is about E=10^8 Volts. Our Sun may be a condenser with 10^7 Coulombs net charge or even more ?

Karl
2005-Jul-11, 12:40 PM
Every object could be charged till its electric capacity only.


I would think it would charge to a voltage based on it's capacity, based on the equation you already gave, q=cv.



Our Sun may be a condenser with 10^7 Coulombs net charge or even more ?

Let's say this happened instantaneously, it would take 100 microseconds for the solar wind current to neutralize it.

czeslaw
2005-Jul-11, 02:31 PM
Our sun is instantaneously discharged, I think too.
It could be charged by Cosmic Rays with about 10^23 protons/s. It is about 10^4 Coulombs/s. When the charge reach its maximum capacity , it will be discharged by Solar Wind very quickly.
The rotating Sunspots might be just a pictures of this magnetic field discharge on the Sunís surface.