Earth's magnetic field

geomagnetismgeomagneticgeomagnetic fieldterrestrial magnetismmagnetic fieldEarthmagnetic field of the Earthgeomagneticsmagneticmagnetic poles
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun.wikipedia
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Magnetic field

magnetic fieldsmagneticmagnetic flux density
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun.
The Earth produces its own magnetic field, which shields the Earth's ozone layer from the solar wind and is important in navigation using a compass.

Dynamo theory

dynamogeodynamogeodynamo effect
The magnetic field is generated by electric currents due to the motion of convection currents of molten iron in the Earth's outer core: these convection currents are caused by heat escaping from the core, a natural process called a geodynamo.
A dynamo is thought to be the source of the Earth's magnetic field and the magnetic fields of Mercury and the Jovian planets.

Paleomagnetism

paleomagneticpalaeomagnetismpalaeomagnetic
These reversals of the geomagnetic poles leave a record in rocks that are of value to paleomagnetists in calculating geomagnetic fields in the past.
Paleomagnetism (or palaeomagnetism in the United Kingdom) is the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials.

South Magnetic Pole

Magnetic South PolesouthMagnetic south
However, at irregular intervals averaging several hundred thousand years, the Earth's field reverses and the North and South Magnetic Poles respectively, abruptly switch places.
The South Magnetic Pole is the wandering point on Earth's Southern Hemisphere where the geomagnetic field lines are directed vertically upwards.

Geomagnetic reversal

geomagnetic reversalsreversalsgeomagnetic polarity time scale
However, at irregular intervals averaging several hundred thousand years, the Earth's field reverses and the North and South Magnetic Poles respectively, abruptly switch places. The polarity of the Earth's magnetic field is recorded in igneous rocks, and reversals of the field are thus detectable as "stripes" centered on mid-ocean ridges where the sea floor is spreading, while the stability of the geomagnetic poles between reversals has allowed paleomagnetists to track the past motion of continents.
A geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged (not to be confused with geographic north and geographic south).

Compass

magnetic compassDigital compassmariner's compass
While the North and South magnetic poles are usually located near the geographic poles, they slowly and continuously move over geological time scales, but sufficiently slowly for ordinary compasses to remain useful for navigation.
It functions as a pointer to "magnetic north", the local magnetic meridian, because the magnetized needle at its heart aligns itself with the horizontal component of the Earth's magnetic field.

Magnetic anomaly

magnetic anomaliesmagneticmagnetic pulses
The field also magnetizes the crust, and magnetic anomalies can be used to search for deposits of metal ores.
In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks.

Magnetoreception

magnetoceptionmagnetic senseavian compass
Using magnetoreception various other organisms, ranging from some types of bacteria to pigeons, use the Earth's magnetic field for orientation and navigation.
For the purpose of navigation, magnetoreception deals with the detection of the Earth's magnetic field.

Magnetic declination

magnetic variationvariationdeclination
Although the magnetic declination does shift with time, this wandering is slow enough that a simple compass remains useful for navigation.
Magnetic declination, or magnetic variation, is the angle on the horizontal plane between magnetic north (the direction the north end of a magnetized compass needle points, corresponding to the direction of the Earth's magnetic field lines) and true north (the direction along a meridian towards the geographic North Pole).

Magnetostratigraphy

chronmagnetostratigraphicmagnetostratigraphically
Reversals also provide the basis for magnetostratigraphy, a way of dating rocks and sediments.
The samples are analyzed to determine their characteristic remanent magnetization (ChRM), that is, the polarity of Earth's magnetic field at the time a stratum was deposited.

North Magnetic Pole

magnetic northMagnetic North PoleNorth
It is straight down at the North Magnetic Pole and rotates upwards as the latitude decreases until it is horizontal (0°) at the magnetic equator.
The North Magnetic Pole is the wandering point on the surface of Earth's Northern Hemisphere at which the planet's magnetic field points vertically downwards (in other words, if a magnetic compass needle is allowed to rotate about a horizontal axis, it will point straight down).

Magnetic dip

magnetic inclinationmagnetic equatordip angle
) or magnetic dip.
Magnetic dip, dip angle, or magnetic inclination is the angle made with the horizontal by the Earth's magnetic field lines.

Mid-ocean ridge

spreading centermid-oceanic ridgespreading ridge
The polarity of the Earth's magnetic field is recorded in igneous rocks, and reversals of the field are thus detectable as "stripes" centered on mid-ocean ridges where the sea floor is spreading, while the stability of the geomagnetic poles between reversals has allowed paleomagnetists to track the past motion of continents.
The orientations of the field preserved in the oceanic crust comprise a record of directions of the Earth's magnetic field with time.

Dip circle

dip needledipping-needledip instrument
Inclination can be measured with a dip circle.
Dip circles (also dip needles) are used to measure the angle between the horizon and the Earth's magnetic field (the dip angle).

Ionosphere

ionosphericD layerionospheric physics
The magnetosphere is the region above the ionosphere that is defined by the extent of the Earth's magnetic field in space.
There are disturbances such as solar flares and the associated release of charged particles into the solar wind which reaches the Earth and interacts with its geomagnetic field.

Van Allen radiation belt

Van Allen beltsradiation beltVan Allen belt
There are also two concentric tire-shaped regions, called the Van Allen radiation belts, with high-energy ions (energies from 0.1 to 10 million electron volts (MeV)).
A Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet's magnetic field.

South Atlantic Anomaly

portionSAASouth Atlantic Geomagnetic Anomaly
A minimum intensity occurs in the South Atlantic Anomaly over South America while there are maxima over northern Canada, Siberia, and the coast of Antarctica south of Australia.
The SAA is the near-Earth region where the Earth's magnetic field is weakest relative to an idealized Earth-centered dipole field.

Geomagnetic storm

geomagnetic stormsmagnetic stormsolar storms
Periods of particularly intense activity, called geomagnetic storms, can occur when a coronal mass ejection erupts above the Sun and sends a shock wave through the Solar System.
A geomagnetic storm (commonly referred to as a solar storm) is a temporary disturbance of the Earth's magnetosphere caused by a solar wind shock wave and/or cloud of magnetic field that interacts with the Earth's magnetic field.

Gauss (unit)

gaussGkG
The magnitude of the Earth's magnetic field at its surface ranges from 25 to 65 microteslas (0.25 to 0.65 gauss).

Ionospheric dynamo region

ionospheric winds
Shorter time scales mostly arise from currents in the ionosphere (ionospheric dynamo region) and magnetosphere, and some changes can be traced to geomagnetic storms or daily variations in currents.
Atmospheric tidal winds due to differential solar heating or due to gravitational lunar forcing move the ionospheric plasma against the geomagnetic field lines thus generating electric fields and currents just like a dynamo coil moving against magnetic field lines.

Outer space

spaceinterstellar spaceintergalactic medium
It extends several tens of thousands of kilometers into space, protecting the Earth from the charged particles of the solar wind and cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects the Earth from harmful ultraviolet radiation.
Geospace is populated by electrically charged particles at very low densities, the motions of which are controlled by the Earth's magnetic field.

K-index

Kp indexA-indexK
The short-term instability of the magnetic field is measured with the K-index.
The K-index quantifies disturbances in the horizontal component of earth's magnetic field with an integer in the range 0–9 with 1 being calm and 5 or more indicating a geomagnetic storm.

Geomagnetic excursion

excursionpolarity excursionsreversal of the Earth's magnetic field
The records typically include long periods of small change with occasional large changes reflecting geomagnetic excursions and reversals.
A geomagnetic excursion, like a geomagnetic reversal, is a significant change in the Earth's magnetic field.

Solar wind

solar windslosessolar
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. It extends several tens of thousands of kilometers into space, protecting the Earth from the charged particles of the solar wind and cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects the Earth from harmful ultraviolet radiation.
Earth itself is largely protected from the solar wind by its magnetic field, which deflects most of the charged particles; however some of the charged particles are trapped in the Van Allen radiation belt.

Tesla (unit)

teslaTteslas
The magnitude of the Earth's magnetic field at its surface ranges from 25 to 65 microteslas (0.25 to 0.65 gauss).