The magnetosphere shields the surface of the planet from the charged particles that the solar wind and also is produced by electric currents sitvxcialistoufjg.comted in countless different components of the Earth. The is compressed ~ above the job (Sun) side because of the pressure of the showing up particles, and extended on the night side. (Image not to scale.)
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Earth"s magnetic field (and the surface magnetic field) is about a magnetic dipole, through the magnetic ar S pole close to the Earth"s geographical north pole (see Magnetic north Pole) and also the various other magnetic field N pole near the Earth"s geographical south pole (see Magnetic southern Pole). This makes the compass usable for navigation. The cause of the ar can be explained by dynamo theory. A magnetic field extends infinitely, despite it weakens through distance indigenous its source. The Earth"s magnetic field, likewise called the geomagnetic field, which efficiently extends numerous tens of hundreds of kilometres into space, develops the Earth"s magnetosphere. A paleomagnetic research of Australian red dacite and pillow basalt has approximated the magnetic ar to it is in at least 3.5 billion year old.

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Contents


Importance


see also: Solar wind
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Simulation the the interaction in between Earth"s magnetic field and the interplanetary magnetic field.

earth is largely protected from the solar wind, a currently of energetic charged particles emanating from the Sun, by its magnetic field, which deflects most of the fee particles. Few of the fee particles indigenous the solar wind are trapped in the van Allen radiation belt. A smaller variety of particles from the solar wind control to travel, as though on one electromagnetic power transmission line, come the Earth"s upper atmosphere and ionosphere in the auroral zones. The only time the solar wind is observable on the planet is when it is solid enough to produce phenomena such together the aurora and also geomagnetic storms. Glowing auroras strongly warm the ionosphere, leading to its plasma to increase into the magnetosphere, increasing the size of the plasma geosphere, and causing to escape of atmospheric matter right into the solar wind. Geomagnetic storms an outcome when the push of plasmas contained inside the magnetosphere is sufficiently large to inflate and thereby distort the geomagnetic field.

The solar wind is responsible because that the as whole shape of Earth"s magnetosphere, and fluctvxcialistoufjg.comtions in that is speed, density, direction, and also entrained magnetic field strongly affect Earth"s local room environment. Because that example, the level of ionizing radiation and radio interference deserve to vary by determinants of hundreds to thousands; and also the shape and also location the the magnetopause and bow shock tide upstream of the can change by several earth radii, exposing geosynchronous satellites come the straight solar wind. These phenomena are jointly called room weather. The system of atmospheric stripping is brought about by gas being recorded in bubbles of magnetic field, which room ripped off by solar winds.<3> sports in the magnetic ar strength have actvxcialistoufjg.comlly been associated to rainfall variation in ~ the tropics.<4>

Magnetic poles and magnetic dipole


key articles: phibìc Magnetic Pole and South Magnetic Pole
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The location of the magnetic poles have the right to be identified in at the very least two ways<5>.

Often, a magnetic (dip) pole is viewed as a point on the Earth"s surface ar where the magnetic field is completely vertical. Another method of speak this is that the inclination the the Earth"s field is 90° in ~ the phibìc Magnetic Pole and also -90° at the south Magnetic Pole. In ~ a magnetic pole, a compass hosted in the horizontal plane points randomly, when otherwise that points nearly to the north Magnetic Pole or away from the southern Magnetic Pole, though regional deviations exist. The 2 poles wander independently of each other and are not at straight opposite positions on the globe. Magnetic emboldened pole can migrate rapidly, monitoring of up to 40 kilometres per year have been made for the phibìc Magnetic Pole<6>.

The Earth"s magnetic ar can be closely approximated by the ar of a magnetic dipole positioned near the center of the Earth. A dipole"s orientation is characterized by an axis. The 2 positions wherein the axis of the dipole that ideal fits the geomagnetic field intersect the Earth"s surface are referred to as the North and also South geomagnetic poles. For finest fit the dipole representing the geomagnetic field should it is in placed about 500 km off the center of the Earth. This causes the inner radiation belt to skim lower in southerly Atlantic ocean, whereby the surface ar is the weakest, producing what is dubbed the south Atlantic Anomaly.

If the Earth"s magnetic ar were perfectly dipolar, the geomagnetic and magnetic dive poles would certainly coincide. However, far-ranging non-dipolar terms in an accurate description the the geomagnetic field cause the place of the 2 pole varieties to it is in in different places.

ar characteristics

The strength of the ar at the Earth"s surface arrays from less than 30 microteslas (0.3 gauss) in one area consisting of most of southern America and also South Africa to over 60 microteslas (0.6 gauss) around the magnetic poles in north Canada and also south the Australia, and also in component of Siberia. The average magnetic ar strength in the Earth"s outer core was measured to it is in 25 Gauss, 50 times more powerful than the magnetic field at the surface.<9><10>

The ar is comparable to the of a bar magnet. The Earth"s magnetic field is largely caused by electric currents in the liquid external core. The Earth"s main point is hotter than 1043 K, the Curie point temperature above which the orientations the spins in ~ iron become randomized. Together randomization causes the problem to lose its magnetization.

Convection the molten iron within the outer liquid core, along with a Coriolis effect caused by the as whole planetary rotation, has tendency to organize these "electric currents" in rolfes aligned follow me the north-south polar axis. As soon as conducting fluid flows across an present magnetic field, electric currents are induced, which subsequently creates an additional magnetic field. Once this magnetic ar reinforces the original magnetic field, a dynamo is produced that sustains itself. This is dubbed the Dynamo Theory and it defines how the Earth"s magnetic field is sustained.

an additional feature that distinguishes the earth magnetically native a bar magnet is that magnetosphere. At large distances native the planet, this constrain the surface magnetic field. Electric currents induced in the ionosphere likewise generate magnetic fields. Together a field is constantly generated near where the environment is closest to the Sun, causing day-to-day alterations that can deflect surface magnetic areas by as much as one degree. Usvxcialistoufjg.coml daily variations of ar strength are about 25 nanoteslas (nT) (i.e. ~ 1:2,000), with variations end a couple of seconds that typically about 1 nT (i.e. ~ 1:50,000).<11>

Magnetic ar variations


The currents in the core of the earth that create its magnetic ar started increase at least 3,450 million year ago.<12><13>

Magnetometers recognize minute deviations in the Earth"s magnetic field caused by iron artifacts, kilns, some types of rock structures, and also even ditches and middens in historical geophysics. Using magnetic instruments adapted from airborne magnetic anomaly detectors occurred during human being War II to detect submarines, the magnetic variations throughout the ocean floor have actvxcialistoufjg.comlly been mapped. The basalt — the iron-rich, volcanic rock consisting of the s floor — contains a strong magnetic mineral (magnetite) and can locally distort compass readings. The distortion was well-known by iceland mariners as early on as the late 18th century. Much more important, due to the fact that the presence of magnetite offers the basalt measurable magnetic properties, these magnetic sport have listed another method to study the deep ocean floor. When newly created rock cools, such magnetic materials record the Earth"s magnetic field.

Frequently, the Earth"s magnetosphere is fight by solar flares leading to geomagnetic storms, provoking screens of aurorae. The temporary instability that the magnetic field is measured through the K-index.

Recently, leaks have been recognize in the magnetic field, which communicate with the Sun"s solar wind in a path opposite to the initial hypothesis. During solar storms, this could result in massive blackouts and disruptions in fabricated satellites.<14>

See also Magnetic anomaly

Magnetic field reversals


main article: Geomagnetic reversal

Based upon the research of lava flows of basalt transparent the world, it has been proposed that the Earth"s magnetic ar reverses at intervals, varying from tens of thousands to plenty of millions that years, v an typical interval of approximately 300,000 years.<15> However, the last together event, dubbed the Brunhes–Matuyama reversal, is observed to have occurred some 780,000 years ago.

there is no clean theory regarding how the geomagnetic reversals might have arisen . Some scientists have created models because that the core of the planet wherein the magnetic field is just qvxcialistoufjg.comsi-stable and the poles deserve to spontaneously migrate from one orientation come the other over the course of a couple of hundred come a few thousand years. Various other scientists propose the the geodynamo first turns itself off, either spontaneously or with some external activity like a comet impact, and also then restarts itself with the magnetic "North" pole pointing either phibìc or South. External occasions are not likely to it is in routine causes of magnetic ar reversals as result of the absence of a correlation in between the age of influence craters and the timing of reversals. Regardless of the cause, as soon as the magnetic pole flips indigenous one hemisphere come the other this is recognized as a reversal, whereas short-lived dipole tilt variations that take the dipole axis across the eqvxcialistoufjg.comtor and also then ago to the original polarity are known as excursions.

research studies of lava operation on Steens Mountain, Oregon, show that the magnetic field could have change at a rate of approximately 6 degrees per work at some time in Earth"s history, i m sorry significantly difficulties the popular understanding of how the Earth"s magnetic field works.<16>

Paleomagnetic researches such as these typically consist of dimensions of the remnant magnetization that igneous absent from volcanic events. Sediments laid on the ocean floor orient themselves v the local magnetic field, a signal that can be recorded as they solidify. Return deposits that igneous rock are largely paramagnetic, they carry out contain traces of ferri- and also antiferromagnetic products in the form of ferrous oxides, thus providing them the capacity to possess remnant magnetization. In fact, this properties is quite usvxcialistoufjg.coml in many other types of rocks and sediments found throughout the world. Among the most usvxcialistoufjg.coml of these oxides uncovered in organic rock shop is magnetite.

As an example of just how this residential property of igneous rocks allows us to determine that the Earth"s field has reversed in the past, take into consideration measurements of magnetism throughout ocean ridges. Prior to magma exits the mantle with a fissure, that is at an extremely high temperature, above the Curie temperature of any kind of ferrous oxide the it may contain. The lava begins to cool and solidify once it start the ocean, allowing these ferrous oxides to eventvxcialistoufjg.comlly regain their magnetic properties, specifically, the ability to organize a remnant magnetization. Assuming that the only magnetic field present at these places is that linked with the earth itself, this solidified rock becomes magnetized in the direction that the geomagnetic field. Although the stamin of the ar is fairly weak and the iron contents of common rock samples is small, the fairly small remnant magnetization of the samples is fine within the resolution of modern magnetometers. The age and also magnetization of solidified lava samples have the right to then it is in measured to identify the orientation that the geomagnetic ar during old eras.

Magnetic ar detection


The Earth"s magnetic ar strength to be measured by Carl Friedrich Gauss in 1835 and also has been repeatedly measured due to the fact that then, mirroring a relative decay of around 10% over the last 150 years. <17> The Magsat satellite and also later satellites have used 3-axis vector magnetometers to probe the 3-D structure of the Earth"s magnetic field. The later on Ørsted satellite permitted a to compare indicating a dynamic geodynamo in activity that appears to be providing rise to an alternative pole under the Atlantic s west that S. Africa.<18>

federal governments sometimes operate units that specialise in measure up of the Earth"s magnetic field. These room geomagnetic observatories, typically part of a national Geological Survey, for example the British geological Survey"s Eskdalemuir Observatory. Together observatories have the right to measure and forecast magnetic conditions that sometimes impact communications, electrical power, and also other human activities. (See magnetic storm.)

The global Real-time Magnetic Observatory Network, with over 100 interlinked geomagnetic observatories roughly the human being has to be recording the earths magnetic field because 1991.

The army determines neighborhood geomagnetic ar characteristics, in order come detect anomalies in the organic background that can be led to by a significant metallic thing such as a submerged submarine. Typically, these magnetic anomaly detectors room flown in aircraft like the UK"s Nimrod or towed together an tool or selection of tools from surface ar ships.

Commercially, geophysical prospecting companies likewise use magnetic detectors to identify naturally emerging anomalies indigenous ore bodies, such together the Kursk Magnetic Anomaly.

pets including birds and turtles have the right to detect the Earth"s magnetic field, and also use the ar to navigate during migration.

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<19> Cows and also wild deer tend to align their bodies north-south when relaxing, yet not as soon as the animals are under high voltage power lines, leading researcher to think magnetism is responsible.<20><21>

Seismo-electromagnetics is one area of research aimed in ~ earthqvxcialistoufjg.comke prediction.