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Topic: Magnetic field

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In the News (Mon 19 Feb 18)

  Geomagnetism: The Magnetic Field of the Earth
The geomagnetic field model is also vital to various kinds of magnetic surveys, such as those used in mineral exploration and the mapping of hazardous earthquake faults.
The magnetic field's strength and direction and their rates of change are predicted every 5 years for a 5-year period.
The influence of this distortion of the geomagnetic field is quite small near Earth's surface (except during solar eruptions associated with sunspots) and becomes larger with increasing distance from Earth.
www.nationalatlas.gov /articles/geology/a_geomag.html   (677 words)

  Magnetic field detectors, compasses, viewers, powdered iron filings
agnetic field viewers and compasses are useful accessories for detecting the presence of magnetic fields and for illustrating their 3 dimensional structure.
A magnaprobe consists of a gimbal mounted magnet that is free to rotate in 3D.
Magnetic compasses are the simplest of accessories for use with magnets.
www.indigo.com /magnets/compasses-field-viewers.html   (301 words)

  NOVA | Magnetic Storm | TV Program Description | PBS
The most visible signs of Earth's magnetic field are auroras, which are caused by charged particles from space interacting with the atmosphere as they flow into the north and south magnetic poles.
At the present rate, Earth's magnetic field could be gone within a few centuries, exposing the planet to the relentless blast of charged particles from space with unpredictable consequences for the atmosphere and life.
Other possibilities: the field could stop weakening and begin to strengthen, or it could weaken to the point that it suddenly flips polarity—that is, compasses begin to point to the South Magnetic Pole.
www.pbs.org /wgbh/nova/magnetic/about.html   (639 words)

  Magnetic field - Wikipedia, the free encyclopedia
The "north" and "south" poles of a magnet or a magnetic dipole are labelled similarly to north and south poles of a compass needle.
It is a response of a medium to the presence of a magnetic field.
The SI unit of magnetic flux density is the tesla.
en.wikipedia.org /wiki/Magnetic_field   (3160 words)

 Encyclopedia :: encyclopedia : Magnetic field   (Site not responding. Last check: )
(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.
Technically, the magnetic field isn't a vector according to the formal definition, it is a pseudovector: it gains an extra sign flip under improper rotations of the coordinate system.
Magnetic field lines point from north to south of a magnet, and hence the natural magnetic field lines run from south to north along the Earth's surface.
www.hallencyclopedia.com /Magnetic_field   (1675 words)

 Earth's magnetic field - Wikipedia, the free encyclopedia
Earth's magnetic field (and the surface magnetic field) is approximately a magnetic dipole, with one pole near the north pole and the other near the geographic south pole.
The magnetic field of a bar magnet, or any other type of permanent magnet, is created by the coordinated spins of electrons and nuclei within iron atoms.
Using a magnetic detector (a variant of a compass), scientists have measured the historical direction of the Earth's magnetic field, by studying sequences of relatively iron-rich lava flows.
en.wikipedia.org /wiki/Earth's_magnetic_field   (1512 words)

 Learn more about Magnetic field in the online encyclopedia.   (Site not responding. Last check: )
Given the symbol B, the magnetic field points in the same direction as would a compass – away from the north pole of a magnet, and towards the north pole of the Earth.
Historically, B was called the magnetic flux density or the magnetic induction, and H (= B / &mu) was called the magnetic field, and this terminology is still often used to distinguish the two in the context of magnetic materials (non-trivial μ).
Magnetic fields are produced by charges in motion, and moving charges are deflected by magnetic fields.
www.onlineencyclopedia.org /m/ma/magnetic_field.html   (564 words)

 Geomagnetism - Earth's magnetic field
The magnetic field is often visualized in terms of magnetic field lines, or lines of force, that leave one end of the magnet, called the north pole, arc through space, and re-enter the magnet at the other end, the south pole.
Mathematically, the Earth's magnetic field is normally described by a spherical harmonic expansion, a series of special spherical functions of latitude/longitude and their associated coefficients.
Charts of the magnetic declination and total intensity, the two most widely used magnetic field elements, are shown in the accompanying figures.
gsc.nrcan.gc.ca /geomag/field/index_e.php   (357 words)

 Earth's Magnetic Field (Magnetosphere)   (Site not responding. Last check: )
All magnetic objects produce invisible lines of force that extend between the poles of the object.
Magnetic field lines radiate between Earth's north and south magnetic poles just as they do between the poles of a bar magnet.
Earth's magnetic field lines are not as symmetrical as those of the bar magnet.
liftoff.msfc.nasa.gov /academy/space/mag_field.html   (188 words)

 Magnetic field
Magnetic fields are produced by electric currents, which can be macroscopic currents in wires, or microscopic currents associated with electrons in atomic orbits.
The magnetic field B is defined in terms of force on moving charge in the Lorentz force law.
Magnetic field sources are essentially dipolar in nature, having a north and south magnetic pole.
hyperphysics.phy-astr.gsu.edu /hbase/magnetic/magfie.html   (252 words)

 Magnetic fields interference solved with electro magnetic shielding
The magnetic field results from a source of magnetic flux, which might be the Earth, a motor, transformer or electric power line, or even a bar magnet.
The ratio of B, magnetic flux, in Gauss, to H, magnetic field, in Oersted, is defined as permeability, "µ;" (pronounced "mew").
You may notice that the magnetic fields are sometimes described in technical literature as fields and sometimes as magnetic flux.
www.magnetic-shield.com /faq/interference.html   (582 words)

 The Earth's Magnetic Field
The dynamo theory is that slow, internal convection currents or planetary rotation generates the magnetic field, and that this mechanism has operated for the assumed 4.6 billion years.
As sediment accumulates or as molten rock cools, the earth's magnetic field is believed to have aligned the magnetic domains within the material as it hardened, locking in a record of the orientation of the geomagnetic field at the time.
Other evidence for a change is that the residual magnetic fields in rock formed on the ocean floor where the great tectonic plates are pulling apart show a number of different orientations.
creationevidence.org /scientific_evid/magnetic_fld/magnetic_fld.html   (1478 words)

 The Earth's Magnetic Field
It is well known that the axis of the magnetic field is tipped with respect to the rotation axis of the Earth.
Thus, true north (defined by the direction to the north rotational pole) does not coincide with magnetic north (defined by the direction to the north magnetic pole) and compass directions must be corrected by fixed amounts at given points on the surface of the Earth to yield true directions.
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.
csep10.phys.utk.edu /astr161/lect/earth/magnetic.html   (585 words)

 The Magnetic Sun   (Site not responding. Last check: )
We are all familiar with magnetic fields, from the magnets on your refrigerator door to the Earth itself.
The pattern of the Earth's magnetic field is roughly like one that would result from a short, powerful magnet near the Earth's center.
The magnetic field pushes on the iron filings, forcing them to line up in patterns which curve around the magnet until they point in the same direction as the magnetic field.
solar.physics.montana.edu /YPOP/Spotlight/Magnetic/what.html   (320 words)

 Earth's Inconstant Magnetic Field
Earth's magnetic field comes from this ocean of iron, which is an electrically conducting fluid in constant motion.
On the left is a normal dipolar magnetic field, typical of the long years between polarity reversals.
Magnetic Field of the Earth (hyperphysics) an explanation of the dynamo effect
science.nasa.gov /headlines/y2003/29dec_magneticfield.htm   (1175 words)

 Magnetic Field Lines
Magnetic field lines similarly describe the structure of magnetic fields in three dimensions.They are defined as follows.
Field lines converge where the magnetic force is strong, and spread out where it is weak.
Indeed, the role of field lines in a plasma resembles that of grain in wood: just as the grain is the "easy" direction along which wood splits most readily, so the direction of field lines is the one along which particles, electric currents, heat and certain types of waves prefer to flow.
www-istp.gsfc.nasa.gov /Education/wfldline.html   (355 words)

 Magnetic Force Field   (Site not responding. Last check: )
At every point in space surrounding a magnet, a moving charge, or a wire carrying current there is a force field called the magnetic field; denoted by the symbol B.
It is the field associated with this additional force that we call the magnetic field.
Note that the direction of the force due to the magnetic field is perpendicular to the direction on the magnetic field while the direction of the electric force and the electric field are in the same direction for a positive charge.
www.ac.wwu.edu /~vawter/PhysicsNet/Topics/MagneticField/MField.html   (158 words)

 NASA - Earth's Inconstant Magnetic Field
Our planet's magnetic field is in a constant state of change, say researchers who are beginning to understand how it behaves and why.
The dipole moment, a measure of the intensity of the magnetic field, is now 8 x 1022 amps x m2.
Magnetic Field of the Earth -- (Hyperphysics) an explanation of the dynamo effect
www.nasa.gov /vision/earth/lookingatearth/29dec_magneticfield.html   (1095 words)

 magnetic field - a definition from Whatis.com
A magnetic field is generated when electric charge carriers such as electrons move through space or within an electrical conductor.
The geometric shapes of the magnetic flux lines produced by moving charge carriers (electric current) are similar to the shapes of the flux lines in an electrostatic field.
Such a synergistic field is known as an electromagnetic field.
whatis.techtarget.com /definition/0,,sid9_gci213446,00.html   (326 words)

 EARTH CHANGES: Magnetic Field Reversal
That magnetic field reversals have occurred in the past is confirmed in the geological record.
South-pointing magnetic flux moves from sunspots, which are intense magnetic loops near the equator of the sun, along “meridional flows” to the north magnetic pole, and vice versa.
Whether the magnetic field is primarily molten-metal flow dynamics or electron current loops, or a combination of those and other factors, a magnetic pole reversal may be of significance to the search for clean energy generation and transportation.
www.pureenergysystems.com /news/2005/02/27/6900064_Magnet_Pole_Shift   (2320 words)

 Creation Science and the Earth's Magnetic Field
In practice, the magnetic field is measured constantly at a number of official magnetic observatories all over the world, as well as at universities, or by other scientific teams and expeditions, and now several spacecraft measure the field well above the Earth, and out into deep space.
It is very hard to imagine a field of magnetic rocks, or a coherent telluric current, either of which is as large as one half or one quarter of the Earth.
Consequences of the Decay of the Magnetic Field
www.talkorigins.org /faqs/magfields.html   (8044 words)

 SPACE.com -- Earth's Magnetic Field Weakens 10 Percent
SAN FRANCISCO (AP) -- The strength of the Earth's magnetic field has decreased 10 percent over the past 150 years, raising the remote possibility that it may collapse and later reverse, flipping the planet's poles for the first time in nearly a million years, scientists said Thursday.
Over the southern Atlantic Ocean, a continued weakening of the magnetic field has diminished the shielding effect it has locally in protecting the Earth from the natural radiation that bombards our planet from space, scientists said.
Among the satellites that have fallen prey to the harmful effects was a Danish satellite designed, ironically, to measure the Earth's magnetic field, Bloxham said.
www.space.com /scienceastronomy/earth_magnetic_031212.html   (396 words)

 Earth's magnetic field shapes the aurora
Earth's magnetic field is in turn compressed by the solar wind and distorted into a comet-shaped cavity known as the magnetosphere.
When the solar wind (plasma is very conductive) blows past the magnetosphere (Earth's magnetic field), it generates as much as a million megawatts of electricity.
Interactions between Earth's electric field, the solar wind, and Earth's magnetic field push and pull the high energy electrons striking Earth's upper atmosphere to create the undulating movements of the auroral curtain.
www.gi.alaska.edu /asahi/magfield01.htm   (431 words)

 News Release - Magnetic field accelerates pellets
In the background is the innermost sanctum of Sandia’s Z accelerator, where a rapidly expanding magnetic field drives pellets faster than any mechanism on earth.
The relatively gentle acceleration produced by the field is similar to that which might be experienced in a smoothly rising high-speed elevator, rather than from the shock imparted by a firearm.
The resultant expansion of the powerful magnetic field is used to propel small objects somewhat the way a surf boarder is propelled who catches one of a succession of enormous waves.
www.sandia.gov /media/NewsRel/NR2001/flyer.htm   (954 words)

 The Sun Does a Flip
Scientists call such a field a "dipole." The Sun's dipolar field is about as strong as a refrigerator magnet, or 50 gauss (a unit of magnetic intensity).
Hathaway noticed the latest polar reversal in a "magnetic butterfly diagram." Using data collected by astronomers at the U.S. National Solar Observatory on Kitt Peak, he plotted the Sun's average magnetic field, day by day, as a function of solar latitude and time from 1975 through the present.
The Sun's magnetic field envelops the entire solar system in a bubble that scientists call the "heliosphere." The heliosphere extends 50 to 100 astronomical units (AU) beyond the orbit of Pluto.
science.nasa.gov /headlines/y2001/ast15feb_1.htm   (1190 words)

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