Does the Earth carry a charge?

ealbers

Thank you for dealing with my silly question....

The Earth is hit by 'solar wind' from the star all the time....does it aquire a 'charge' relative to the star?

Do objects in orbit aquire a charge relative to the earth?

If the Earth did aquire a charge relative to its star, could it 'discharge' in a big 'lightning bolt' back to the star at some point??

Can the charge (if it exists) be somehow measured??

Thanks again for your patience with my questions
Eric

Vorde

The Earth is neutrally charged. Sometimes you get areas of positive and negative charge, but they always attract each other and equal out (lightning).

LadyStardust

Even the smallest charge would quickly draw an opposite charge from the environment around us - there's plenty of charged particles in the solar wind, for example. So the Earth is, for all intents and purposes, charged neutral.

Dotini

The Earth's magnetosphere largely insulates the planet from incoming charges from the sun.

Voltage difference is relative, requiring a reference point to measure. A bird on a high voltage wire is unaware of it, unless a wing touches a nearby wire of different voltage.

We can't even measure the voltage of Earth relative to the Moon. Insulating sheaths surround charged bodies, and spacecraft change charge as they move from one body to another.

There is no doubt that the Earth's surface is negatively charged with respect to the atmosphere. We are constantly being charged by lightning, and the charge is constantly being discharged back to the atmosphere, creating a balance.

Here is some information relevant to the questions.
http://books.nap.edu/openbook.php?record_id=898&page=6
http://books.nap.edu/openbook.php?re...d=898&page=195

In short, your questions are good ones, but not easily or briefly answered.

Respectfully submitted,
Steve

Dotini

Yes, but...
As it turns out, the sun's charged particles regularly connect directly with the Earth, bypassing the magnetosphere through shifting and elusive portals. http://www.youtube.com/watch?v=y3_vW5yrNek

Auroral activity, geomagnetic storms and upper atmospheric heating are associated with these flux transfer events which directly couple the magnetic field of the sun with that of Earth. A range of implications are undoubtedly inherent in this infant field of discovery and research, including questions of Earth's electrical charge found in the OP.

Respectfully submitted,
Steve

Dotini

NASA has questions about the physics of the Van Allen belts, so they are launching a new mission of study. Their success will help answer our question of Earth's charge.
http://www.sciencedaily.com/releases...0717183418.htm
"Scientists want to understand not only the origins of electrified particles -- possibly from the solar wind constantly streaming off the sun; possibly from an area of Earth's own outer atmosphere, the ionosphere -- but also what mechanisms gives the particles their extreme speed and energy.

"We know examples where a storm of incoming particles from the sun can cause the two belts to swell so much that they merge and appear to form a single belt," says Shri Kanekal, RBSP's deputy project scientist at Goddard. "Then there are other examples where a large storm from the sun didn't affect the belts at all, and even cases where the belts shrank. Since the effects can be so different, there is a joke within the community that 'If you've seen one storm . . . You've seen one storm.' We need to figure out what causes the differences."

There are two broad theories on how the particles get energy: from radial transport or in situ. In radial transport, particles move perpendicular to the magnetic fields within the belts from areas of low magnetic strength far from Earth to areas of high magnetic strength nearer Earth. The laws of physics dictate that particle energies correlate to the strength of the magnetic field, increasing as they move towards Earth. The in situ theory posits that electromagnetic waves buffet the particles -- much like regular pushes on a swing -- successively raising their speed (and energy).

As for how the particles leave the belts, scientists again agree on two broad possibilities: particles go up, or they go down. Perhaps they travel down magnetic field lines toward Earth, out of the belts into the ionosphere, where they stay part of Earth's magnetic system with the potential to return to the belts at some point. Or they are transported up and out, on a one-way trip to leave the magnetosphere forever and enter interplanetary space."


Respectfully submitted,
Steve

phinds

That's quite a thought. What kind of power do you think it might take to create an arc that would go through 93,000,000 miles of vacuum? What might this do to the earth?

Dotini

Discussion of Earth's charge can perhaps be enhanced by some discussion of sign convention and what we know about charge on the surface and in the atmosphere up to about 50 km, a level known as the electrosphere. I have abstracted the following general information from Martin Uman's book, The Lightning Discharge. I hope to continue the discussion with further posts based on this informative source.

The voltage between the Earth and the electrosphere in regions of fair weather is about 300,000 V. To maintain this voltage the earth has about 10^6 C of negative charge on its surface, an equal positive charge being distributed throughout the atmosphere. In regions of fine weather, atmospheric currents of the order of 1000 A are continuously depleting this charge. The charge is apparently replaced by the actions of thunderstorms including lightning. The thunderstorm system acts as a type of battery to keep the fine weather system charged.
...........................

It has been found by measurement that the fine-weather electric field vector above the Earth is directed downward toward the Earth. That is, the Earth is negatively charged and the atmosphere above the Earth is positively charged. The magnitude of the fine-weather electric field intensity at the ground is of the order of 100 V/m. In most of the atmospheric-electrical literature the fine-weather electric field is termed a positive electric field. We therefore use the following historical sign convention: an electric field at the ground level is called positive if it is the same direction as the field due to positive charge above ground level, that is, if the vector field is directed downward toward Earth; an electric field at the ground is called negative if the vector field is directed upward away from the Earth. An electric field change at the ground is defined as positive if the change is attributable to an increase of positive charge (or decrease of negative charge) overhead, that is, an increase in the magnitude of the downward-directed field vector. A negative field change is associated with the increase of an upward-directed field vector. The signs of the fields just defined are opposite to those for more standard coordinate systems with either an origin at the center of the Earth and radial coordinate outward or an origin on the Earth's surface with z-coordinate upward.

Respectfully submitted,
Steve

twofish-quant

There's something similar that exists between Io and Jupiter. There is a constant electric arc between Io and Jupiter.

Dotini

Nice find.
I sussed out this: http://www.uta.edu/faculty/yijiun/pa...02JA009247.pdf
Nothing so dramatic as interplanetary sparks (!), but highly interesting nonetheless.

Respectfully,
Steve

twofish-quant

There's an issue here of net charge and charges. It's hard for an astrophysical object to have a net charge, but depending on the environment, you can get large local charges.

It's much easier for the earth to end up with local charges than the sun because the earth is cold. Once you heat something up, you end up with lots of ionized material. Ionized material means free electrons, and once you end up with free electrons then no charge build-up.

This happens at a local level. You get more static electricity on cold, dry days then hot, humid ones.

Dotini

I'm terribly sorry, but this statement has confused me, since it is in conflict with my very basic textbook.

"A neutral object can become charged by gaining or losing electrons. If an object loses electrons, it is left with more protons (positive charge) than electrons (negative charge). Thus, the object is positively charged overall. If, instead, an object gains electrons, it has more electrons than protons. Thus it has a negative overall charge."

Source: Electricity and Magnetism, Science Explorer Student Edition, Prentice Hall 2002

Respectfully submitted,
Steve

Vorde

What twofish-quant was saying is that once you have heated a material up to a significant amount (I am skeptical about this being the cause for higher static electricity on warmer days however), the electrons being to separate from the nucleus and become free electrons in the material. The amount of electrons and protons present are still the same, but they are no longer paired up in atoms.

When this happens it becomes much harder to build up a significant net charge.

zonde

I think this is wrong.
I think Electrochemistry says it happens. For particular example, Galvanic anode works because there is some charge build-up when you connect two different metals.

twofish-quant

But it means a difference whether those electrons are "free" or not. If those electrons are bound to atoms, then you can have a very large charge build up. If those electrons are free (i.e. in most metals where the electrons are not bound to the atom), then it's hard to keep a charge.

twofish-quant

But even in those cases, you need some material with less charge mobility for the charge to build up. If you just put two metals in say mercury it won't work. You need to put it into some medium without free electrons to build up a charge. In batteries the electrons in the solution aren't free but bound to ions which reduces their mobility.

zonde

No, why?
Not sure I understand your argument. You have piece of one metal and piece of different metal. You connect them and for some small time electricity flows between them until charge builds up and stops the current.

EDIT: Ok, obviously connected state and disconnected state should be different so disconnected state kind of implies insulator (material with less charge mobility).