Is the Earth Electrically Charged?

[ealbers]

Thank you for dealing with my silly question...

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

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

If the Earth did acquire 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]

Thank you for dealing with my silly question...

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

Eric

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

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

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

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?record_id=898&page=195

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

Respectfully submitted,
Steve

 

[Dotini]

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

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.

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/2012/07/120717183418.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]

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

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]

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?

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

 

[Dotini]

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

Nice find.
I sussed out this: http://www.uta.edu/faculty/yijiun/paper/2002JA009247.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]

...once you end up with free electrons then no charge build-up.

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]

... once you end up with free electrons then no charge build-up.

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]

"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."

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]

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.

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]

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.

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).

 

[twofish-quant]

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.

If you just put two metals next to each other you won't get current. In order for you to get current you have to connect them with some sort of substance that allows ions to move in the other direction. This only works because the substance that moves charge through the fluid does so through bound electrons that move a lot less slowly then free electrons.

 

[zonde]

If you just put two metals next to each other you won't get current. In order for you to get current you have to connect them with some sort of substance that allows ions to move in the other direction. This only works because the substance that moves charge through the fluid does so through bound electrons that move a lot less slowly then free electrons.

Let's compare two cases:
1) two different disconnected metals in electrolyte
2) two different connected metals in electrolyte

Ions in electrolyte move lot less slowly then electrons in metal. So that means that electron distribution in metals is stable compared to slowly moving ions (two dynamical processes are decoupled). As we observe that these two cases are different (stable) electron distribution should be different in two cases.

 

[Dotini]

Is Earth charged? Maybe, but what is the Earth? Does the Earth stop at the surface? We know from previous posts that the Earth's surface is negatively charged. Does the Earth include the troposphere, the ionosphere, the Van Allen belts, the magnetosphere? Is it smarter to think of the Earth as part of a dynamic system involving the sun and the interplanetary medium?

The following post will help us to think about these questions.

The lightning we are all familiar with is generated in clouds by charge separation and electric fields. http://www.sciencedaily.com/releases/2009/06/090601140934.htm

Electrons are accelerated from Earth into the Van Allen belts:

When particularly intense lightning discharges in thunderstorms coincide with high-energy particles coming in from space (cosmic rays), nature provides the right conditions to form a giant particle accelerator above the thunderclouds.

The cosmic rays strip off electrons from air molecules and these electrons are accelerated upwards by the electric field of the lightning discharge. The free electrons and the lightning electric field then make up a natural particle accelerator.

The accelerated electrons then develop into a narrow particle beam which can propagate from the lowest level of the atmosphere (the troposphere), through the middle atmosphere and into near-Earth space, where the energetic electrons are trapped in the Earth's radiation belt and can eventually cause problems for orbiting satellites. These are energetic events and for the blink of an eye, the power of the electron beam can be as large as the power of a small nuclear power plant. http://www.sciencedaily.com/releases/2010/04/100413202850.htm

Highly energetic electrons in the outer Van Allen belt are lost into the interplanetary medium during solar storms:

During powerful solar events such as coronal mass ejections, parts of the magnetized outer layers of sun's atmosphere crash onto Earth's magnetic field, triggering geomagnetic storms capable of damaging the electronics of orbiting spacecraft . These cosmic squalls have a peculiar effect on Earth's outer radiation belt, a doughnut-shaped region of space filled with electrons so energetic that they move at nearly the speed of light.

"During the onset of a geomagnetic storm, nearly all the electrons trapped within the radiation belt vanish, only to come back with a vengeance a few hours later," said Vassilis Angelopoulos, a UCLA professor of Earth and space sciences and IGPP researcher.

The missing electrons surprised scientists when the trend was first measured in the 1960s by instruments onboard the earliest spacecraft sent into orbit, said study co-author Yuri Shprits, a research geophysicist with the IGPP and the departments of Earth and space sciences, and atmospheric and oceanic sciences.

"It's a puzzling effect," he said. "Oceans on Earth do not suddenly lose most of their water, yet radiation belts filled with electrons can be rapidly depopulated."

Even stranger, the electrons go missing during the peak of a geomagnetic storm, a time when one might expect the radiation belt to be filled with energetic particles because of the extreme bombardment by the solar wind.

Where do the electrons go? This question has remained unresolved since the early 1960s. Some believed the electrons were lost to Earth's atmosphere, while others hypothesized that the electrons were not permanently lost at all but merely temporarily drained of energy so that they appeared absent.

"Our study in 2006 suggested that electrons may be, in fact, lost to the interplanetary medium and decelerated by moving outwards," Shprits said. "However, until recently, there was no definitive proof for this theory."

To resolve the mystery, Turner and his team used data from three networks of orbiting spacecraft positioned at different distances from Earth to catch the escaping electrons in the act. The data show that while a small amount of the missing energetic electrons did fall into the atmosphere, the vast majority were pushed away from the planet, stripped away from the radiation belt by the onslaught of solar wind particles during the heightened solar activity that generated the magnetic storm itself. http://www.sciencedaily.com/releases/2012/01/120129150958.htm


The outer Van Allen belt swells and shrinks by a factor of 100 according to the way it fits into the larger system of its interaction with the solar wind and CMEs, and with Earth http://www.sciencedaily.com/releases/2012/01/120131143745.htm

In reality, where do the extra energy and particles come from? Where do they disappear to, and what sends them on their way? How do these changes affect the rest of Earth's magnetic environment, the magnetosphere? We will find out with the RBSP mission. http://www.sciencedaily.com/releases/2012/07/120717183418.htm



Respectfully submitted,
Steve