why earth have a magnetic field? how?
608387
The Earth's center contains a lot of molten iron; due to Earth's rotation, it rotates too, thus generating a magnetic field. It's bit more complicated, but in a nut that's the explanation.
263619
Before we can understand auroras, we need a few facts about the space around our Earth. There are many things in this space that we can't see.\n\nOne thing is the air we breathe, our atmosphere. It is really a mixture of several gases, mostly nitrogen and oxygen, with traces of hydrogen, helium and various compounds.\n \n\n\nA Field of Earth\nAnother thing we can't see is a magnetic field that surrounds the Earth. If you've ever played with a bar magnet and iron filings you've seen the curved patterns the filings form in the magnetic field. The next picture shows how the magnetic field around the earth's core is like the field of a bar magnet.\n\nThe Earth's "magnet" is deep in the core. Since we can't see the magnetic field, we draw lines to represent it. The field lines go into and out of the Earth around the Earth's magnetic poles. Where the lines are closest together the field is strongest. Where they are furthest apart it is weakest. Can you tell where the magnetic field is the strongest? Where is it weakest?   \n\n\nCharged Particles\nA third invisible thing in the space around the Earth is a plasma, made of lots of charged particles. There are always electrons and positive ions in the surrounding magnetic field. Charged particles in a magnetic field move in a special way: they are guided by the field. The particles travel along magnetic field lines as if they were wires, circling around the lines in a long spiral as they go. Charged particles are the "ammunition" of an aurora.\n \n\nSolar Powered Display\nThe short answer to how the aurora happens is that energetic electrically charged particles (mostly electrons) accelerate along the magnetic field lines into the upper atmosphere, where they collide with gas atoms, causing the atoms to give off light. But why does that happen? To find the answer, we must look further away, to the Sun. The spectacular, "great" auroras in "What do they look like?" are powered by what is called the solar wind.\n\nThe Sun also has an atmosphere and a magnetic field that extend into space. The Sun's atmosphere is made of hydrogen, which is itself made of subatomic particles: protons and electrons. These particles are constantly boiling off the Sun and streaming outward at very high speeds.  Together, the Sun's magnetic field and particles are called the "solar wind."\n\n This wind is always pushing on the Earth's magnetic field, changing its shape.  You change the shape of a soap bubble in a similar way when you blow on its surface. We call this compressed field around the earth the magnetosphere. The Earth's field is compressed on the day side, where the solar wind flows over it. It is also stretched into a long tail like the wake of a ship, which is called the magnetotail, and points away from the Sun.  \n\nSqueezing the Earth's magnetic field takes energy, just the way it takes energy to compress a balloon with air in it. The whole process is still not fully understood, but energy from the solar wind is constantly building up in the magnetosphere, and this energy is what powers auroras.\n\n\nThe Big Push\nSo we have the Earth's magnetosphere, with the solar wind squeezing the magnetosphere and charged particles everywhere in the field. Solar particles are always entering the tail of the magnetosphere from the solar wind and moving toward the Sun. Now and then, when conditions are right, the build-up of pressure from the solar wind creates an electric voltage between the magnetotail and the poles, like the voltage between the two terminals of a battery. It can reach about 10,000 volts! \n\nThe voltage pushes electrons (which are very light) toward the magnetic poles, accelerating them to high speeds, much like the electrons in a TV picture tube that accelerate to hit the screen. They zoom along the field lines towards the ground to the north and south, until huge numbers of electrons
991018
No! Earth has a power gravity core not a magnetic gravity core, the magnetic and Iron core is the weight density on spacetime providing gravity as some people including me theorise and include that to our major theories.
523133
Earth's magnetic field, among other things.
229163
In physics, a magnetic field is an entity produced by moving electric charges (electric currents) that exerts a force on other moving charges. (The quantum-mechanical spin of a particle produces magnetic fields and is acted on by them as though it were a current; this accounts for the fields produced by "permanent" ferromagnets.) A magnetic field is a vector field: it associates with every point in space a (pseudo-)vector that may vary in time. The direction of the field is the equilibrium direction of a compass needle placed in the field.
486058
No.The magnetosphere is the result of Earth`s magnetic field. It depends directly on the magnetic field. But is not expanding or getting smaller, at least not at a large scale. There are variations, but little ones. The magnetic field is created by Earth`s spinning melted iron core. If the angular speed of the core decreases or increases, then the magnetic field and the magnetosphere will do the same thing. For now, thank`s God, is constant.
131285
If you mean a magnetic field produced by a magnet,it has been used as a therapy. To date there is no proof that it Works.WE are living already in a weak magnetic field; that of the earth.
273548
The Earth has a magnetic field very much like that of a bar magnet, directed from the geographic South pole to geographic North pole. Charged particles streaming outward from the Sun arrive in the Earth's vicinity. Collisions in the Earth's vicinity slow them down and they subsequently get trapped in spiral paths around the planet's magnetic field lines. A point of note is that the field lines become more dense as they approach a pole. As the lines become more dense the charged particles' path becomes flatter and eventually turns back on itself. A particle spiraling along the field lines from the South pole to the North Pole turns around at the North Pole spiraling back and heading southward. These are in effect magnetic mirrors. Particles trapped in this way accumulate in regions called the Van Allen Belts. There exists two such belts: one containing protons at a height of about 3,000 km and the other containing electrons at about 15,000 km. \n\nOne of the consequences of the belts is the aurora borealis and aurora austrealis. This occurs whenever the charged particles enter the atmosphere and excite the atoms in the air creating the colors you see. These are noticeable near the poles where the magnetic field lines dip toward the Earth's surface, carrying the Van Allen belts with them.\n\n---\nTypically the aurora appears either as a diffuse glow or as "curtains" that approximately extend in the east-west direction. At some times, they form "quiet arcs," at others ("active aurora") they evolve and change constantly. Each curtain consists of many parallel rays, each lined up with the local direction of the magnetic field lines, suggesting that aurora is shaped by the Earth's magnetic field, Indeed, satellites show auroral electrons to be guided by magnetic field lines, spiraling around them while moving earthwards.\n\nThe curtains often show folds called "striations." When the field line guiding a bright auroral patch leads to a point directly above the observer, the aurora may appear as a "corona" of diverging rays, an effect of perspective.
329912
The magnetic field comes from the magnets that are in the generator. The magnets surround the wire coils. As the wire coils rotate, they pass by the magnets. A moving magnetic field (it's all relative, the magnetic field is still in this case) cause a current to be induced in the wire coils, thus producing electricity.\n\nI don't it has much to do with the earth's magnetic field.
1110951
hi dear friend\n         Absolutely the earth has magnetic energy naturally.because for example if we take an hydroelectric power plants the electricity is produced from the up to down fall of water on the turbines it is due to the magnetic property of the earth.Imagine if this hydro-electric power plant is built on the moon then how the water can flow think about it  there is no gravitational feild on moon.then water drops fall is very slow imagine how u can generate large amount of power.\n                                why iam saying this is upto my knowledge there is no other instruments to derive the large amount of free magnetic enery from the earth.if we want to find such kind of instruments we have to send lot of moneys.The only thing is by using friction due to magnetic propery of earth we can able to generate small amount of electrical energy\nfor example:\n             If u see in cycle dynamo it is kept in touch with the cycle tiers.Due to friction the cycle tiers is running and there will be little amount of current will be generated for lighting purpose.
129623
The dynamo theory (that the earth is maganetic) is actually due to the fact that the outer crust is molten iron.  This iron is moving around inside the earth at very high temperatures.  Physics tells us that moving metals will create  a magnetic field.  This is why we have the magnetic field around the earth.
615788
(m)\n\nIn basic electrodynamics, all magnetic fields are produced by currents of charge in motion, so ultimately within each planet there must be a rotating current of conducting, charged material. There is a reasonably good theory of solar and planetary magneto-dynamics worked out in the 1960's and 1970's by Eugene Parker that relates the rotation period and conductivity of the Sun and each planet to the geometry and strength of their magnetic fields. It even predicts that periodically, these magnetic fields should change their polarity. The Sun does this every 22 years ( twice the sunspot cycle); the Earth every 250,000 years or so. The periods can actually be computed just by knowing the conductivity and rotation period of the Sun and Earth. \n\nOne feature of planetary magnetic fields is that they are almost always NOT aligned with the rotation axis of the planet. This indicates that the core of a planet is subject to its own physics, and that the flows of conducting material deep inside do not slavishly follow the rotation axis of the planet. In fact, the magnetic field of Neptune is located 1/3 of the way to the surface from its center! \n\n \n\nThere is still a lot that astronomers do not understand about how planetary and stellar magnetic fields are generated, maintained, and undergo periodic changes, but empirically there is quite a bit we have learned about them in the last 50-100 years!
675424
the earth has a molten metallic core that's spinning...creates an em field
451560
A magnet is an object that has a magnetic field. The word magnet comes from the Greek (magnētēs lithos), which means "magnesian stone". Magnesia was an area in Ancient Greece, in present-day Manisa, Turkey where deposits of magnetite have been discovered since antiquity.\n\nElectronic generation of magnetism\nElectrons play the primary role in generating a magnetic field. Within an atom, electrons can exist either individually or in pairs within any given orbital. When they are paired, the individuals in that pair always have opposite spin — one up, one down. The fact that the spins have opposite orientation means that the two cancel one another. If all electrons are paired, no net magnetic field will be generated.\n\nIn some atoms, there are electrons that are unpaired. All magnets have unpaired electrons, but not all atoms with unpaired electrons are ferromagnetic. In order for the material to become ferromagnetic, not only must there be unpaired electrons present, but those unpaired electrons must interact with one another over long ranges such that they are all oriented in the same way. The specific electron configuration of the atoms (as well as the distance between atoms) is what leads to this long range ordering. The electrons find that they can exist in a lower energy state if they all have the same orientation.\n\n\nNorth-south pole designation and the Earth's magnetic field\nA standard naming system for the poles of magnets is important. Historically, the terms north and south reflect awareness of the relationship between magnets and the earth's magnetic field. A freely suspended magnet will eventually orient itself north-to-south, because of its attraction to the north and south magnetic poles of the earth. The end of a magnet that points toward the Earth's geographic North Pole is labeled as the north pole of the magnet; correspondingly, the end that points south is the south pole of the magnet.\n\nThe Earth's current geographic north is thus actually its magnetic south. Confounding the situation further, magnetised rocks on the ocean floor show that the Earth's magnetic field has reversed itself in the past, so this system of naming is likely to be backward at some time in the future.\n\nFortunately, by using an electromagnet and the right hand rule, the orientation of the field of a magnet can be defined without reference to the Earth's geomagnetic field.\n\nTo avoid the confusion between geographic and magnetic north and south poles, the terms positive and negative are sometimes used for the poles of a magnet. The positive pole is that which seeks geographical north.\n\n\nCommon uses for magnets\nMagnetic recording media: Common VHS tapes contain a reel of magnetic tape. The information that makes up the video and sound is encoded on the magnetic coating on the tape. This is why magnets will destroy the information in these types of tapes. Common audio cassettes also rely on magnetic tape. Similarly, in computers, floppy disks and hard disks record data on a thin magnetic coating. \nCredit, debit, and ATM cards: All of these cards have a magnetic strip on one of their sides. This strip contains the necessary information to contact an individuals financial institution and connect with their account(s). \nCommon televisions and computer monitors: The vast majority of TV's and computer screens rely in part on an electromagnet to generate an image--see the article on cathode ray tubes for more information. Plasma screens and LCDs rely on different technology entirely. \nLoudspeakers and microphones: Loudspeakers actually rely on a combination of a permanent magnet and an electromagnet. A speaker is fundamentally a device to convert electric energy (the signal) into mechanical energy (the sound). The electromagnet carries the signal, which generates a changing magnetic field that pushes and pulls on the field generated by the permanent magnet. This pushing and pulling moves t
840444
The origin of the Earth's magnetic field is not completely understood, but is thought to be associated with electrical currents produced by the coupling of convective effects and rotation in the spinning liquid metallic outer core of iron and nickel. This mechanism is generally known as the dynamo effect. \n\nBecause of the rotating outer core,it produces an electric current, which in turn, produces a magnetic field that also interacts with the fluid motion to create a secondary magnetic field. Together, the two fields are stronger than the original and lie essentially along the axis of the Earth's rotation.
261004
Although the Moon does not appear to have a magnetosphere surrounding it, it *is* a magnetic object in space. Scientists think that the magnetism of the Moon's surface is leftover from a time when the Moon's magnetic field was actively created by a dynamo within the lunar core, and that this remnant magnetism may gradually erode away. \n\nTheories also suggest that the Moon's magnetism may come from collisions with other celestial bodies such as asteroids and comets, which might have imparted to the Moon some magnetic properties. \n\nSome regions of the Moon's surface are more magnetic than others. A strip of the lunar crust called the Rima Sirsalis seems to be very strongly magnetic. Measurements of the uneveness of the magnetism and depth of the lunar crust such as those being made by the Lunar Prospector mission can supply information about the magnetism of the surface, as well as the size and electrical conductivity of the lunar core. Ultimately these measurements will help scientists better understand the Moon's origins. For example, if the core contains more magnetic elements (such as iron) than the Earth, then the collision/ejection theory of lunar origin loses some support. \n\nScientists believe that certain lunar surface features, such as the albedo swirls, may have magnetic origins. The swirls resemble unstirred cream in a coffee cup. Researchers suspect that the contrasting light and dark regions might indicate the juxtaposition of irregular magnetic fields. Using data obtained both from its Magnetometer and Electron Reflectometer instruments, Lunar Prospector will map global locations, strengths and orientations of lunar crustal magnetic fields. With these experiments, scientists can learn if there is a relationship between such magnetic fields and the surface.
578157
3200 Degrees C.\n\n"The outer core, which is responsible for the Earth's magnetic field, contains about 29.3% of the Earth's mass and has an average density of 12200-9900kg/m3 and temperature of 3200 degrees C."\nhttp://www.cobweb.net/~bug2/rock7.htm