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A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. Earth is surrounded by a magnetosphere, as are the magnetized planets Mercury, Jupiter, Saturn, Uranus and Neptune. Jupiter's moon Ganymede is magnetized, but too weakly to trap solar wind plasma. Mars has patchy surface magnetization. The term "magnetosphere" has also been used to describe regions dominated by the magnetic fields of celestial objects, e.g. pulsar magnetospheres. Image File history File links Portal. ... Astronomical objects are significant physical entities, associations or structures which current science has confirmed to exist in space. ... For the indie-pop band, see The Magnetic Fields. ... This article is about Earth as a planet. ... This article is about the planet. ... For other uses, see Jupiter (disambiguation). ... This article is about the planet. ... For other uses, see Uranus (disambiguation). ... For other uses, see Neptune (disambiguation). ... This article is about the natural satellite of Jupiter. ... Adjectives: Martian Atmosphere Surface pressure: 0. ...

Artistic rendition of Magnetosphere.

Image File history File links Download high resolution version (1200x656, 391 KB)Artists rendition of Earths magnetosphere. ... Image File history File links Download high resolution version (1200x656, 391 KB)Artists rendition of Earths magnetosphere. ...

History of magnetospheric physics

Main article: Magnetosphere history

The Earth's magnetosphere was discovered in 1958 by Explorer 1 during the research performed for the International Geophysical Year. Before this, scientists knew that electric currents flowed in space, because solar eruptions sometimes led to "magnetic storm" disturbances. No one knew, however, where those currents flowed and why, or that the solar wind existed. In August and September of 1958, Project Argus was performed to test a theory about the formation of radiation belts that may have tactical use in war. Chronology 1600     William Gilbert in London suggests the Earth is a giant magnet[1]. 1741     Hiorter and Anders Celsius note that the polar aurora is accompanied by a disturbance of the magnetic needle. ... Explorer-I, officially known as Satellite 1958 Alpha, was the first United States Earth satellite and was sent aloft as part of the United States program for the International Geophysical Year 1957-1958. ... The International Geophysical Year or IGY was an international scientific effort that lasted from July 1, 1957, to December 31, 1958. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... Operation Argus was a series of nuclear weapons tests and missile tests secretly conducted during August and September of 1958, in the South Atlantic (see: South Atlantic Anomaly), by the Defense Nuclear Agency, in conjunction with the Explorer IV mission. ...

In 1959 Thomas Gold proposed the name magnetosphere, when he wrote: This article is about Thomas Gold, an Austrian astrophysicist. ...

"The region above the ionosphere in which the magnetic field of the earth has a dominant control over the motions of gas and fast charged particles is known to extend out to a distance of the order of 10 earth radii; it may appropriately be called the magnetosphere." Journal of Geophysical Results' LXIV. 1219/1

Schematic of Earth's magnetosphere. The solar wind flows from left to right.

The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ...

Earth's magnetosphere

Main article: Earth's magnetic field

The magnetosphere of Earth is a region in space whose shape is determined by the extent of Earth's internal magnetic field, the solar wind plasma, and the interplanetary magnetic field (IMF). In the magnetosphere, a mix of free ions and electrons from both the solar wind and the Earth's ionosphere is confined by magnetic and electric forces that are much stronger than gravity and collisions. In spite of its name, the magnetosphere is distinctly non-spherical. On the side facing the Sun, the distance to its boundary (which varies with solar wind intensity) is about 70,000 km (10-12 Earth radii or R_E, where 1 R_E=6371 km; unless otherwise noted, all distances here are from the Earth's center). The boundary of the magnetosphere ("magnetopause") is roughly bullet shaped, about 15 R_E abreast of Earth and on the night side (in the "magnetotail" or "geotail") approaching a cylinder with a radius 20-25 R_E. The tail region stretches well past 200 R_E, and the way it ends is not well-known. The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... The Interplanetary Magnetic Field (IMF) is the term for the Sun’s magnetic field among the planets of the Solar System. ... ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... A magnetopause flows along the boundary between a magnetic field, (see: magnetosphere) and surrounding plasma. ...

The outer neutral gas envelope of Earth, or geocorona, consists mostly of the lightest atoms, hydrogen and helium, and continues beyond 4-5 R_E, with diminishing density. The hot plasma ions of the magnetosphere acquire electrons during collisions with these atoms and create an escaping "glow" of fast atoms that have been used to image the hot plasma clouds by the IMAGE mission. The upward extension of the ionosphere, known as the plasmasphere, also extends beyond 4-5 R_E with diminishing density, beyond which it becomes a flow of light ions called the polar wind that escapes out of the magnetosphere into the solar wind. Energy deposited in the ionosphere by auroras strongly heats the heavier atmospheric components such as oxygen and molecules of oxygen and nitrogen, which would not otherwise escape from Earth's gravity. Owing to this highly variable heating, however, a heavy atmospheric or ionospheric outflow of plasma flows during disturbed periods from the auroral zones into the magnetosphere, extending the region dominated by terrestrial material, known as the fourth or plasma geosphere, at times out to the magnetopause. The Geocorona refers to an extention of the outermost region of the Earths atmosphere. ... The plasmasphere is a layer of the Earths magnetosphere that is rich in plasma. ... The Aurora Borealis, or Northern Lights, shines above Bear Lake Aurora Borealis as seen over Canada at 11,000m (36,000 feet) Red and green Aurora in Fairbanks, Alaska Aurora Borealis redirects here. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... In the most general sense, the geosphere is the region of space that is dominated by geogenic matter (originating from and bound to the Earth). ... A magnetopause flows along the boundary between a magnetic field, (see: magnetosphere) and surrounding plasma. ...

What follows is a condensed overview of the Earth's magnetosphere only. To avoid an overlong presentation, this section gives a general introduction. The

1. motion of particles trapped in the magnetosphere (MOT),
2. physics of magnetic storms and plasma flows (MSPF), and
3. history of magnetospheric research (HIST)

will be covered separately. This is a nontechnical overview and more technical discussions are cited at the end.

General properties

Two factors determine the structure and behavior of the magnetosphere: (1) The internal field of the Earth, and (2) The solar wind.

1. The internal field of the Earth (its "main field") appears to be generated in the Earth's core by a dynamo process, associated with the circulation of liquid metal in the core, driven by internal heat sources. Its major part resembles the field of a bar magnet ("dipole field") inclined by about 10° to the rotation axis of Earth, but more complex parts ("higher harmonics") also exist, as first shown by Carl Friedrich Gauss. The dipole field has an intensity of about 30,000-60,000 nanoteslas (nT) at the Earth's surface, and its intensity diminishes like the inverse of the cube of the distance, i.e. at a distance of R Earth radii it only amounts to 1/R³ of the surface field in the same direction. Higher harmonics diminish faster, like higher powers of 1/R, making the dipole field the only important internal source in most of the magnetosphere.
2. The solar wind is a fast outflow of hot plasma from the sun in all directions. Above the sun's equator it typically attains 400 km/s; above the sun's poles, up to twice as much. The flow is powered by the million-degree temperature of the sun's corona, for which no generally accepted explanation exists as yet. Its composition resembles that of the Sun—about 95% of the ions are protons, about 4% helium nuclei, with 1% of heavier matter (C, N, O, Ne, Si, Mg... up to Fe) and enough electrons to keep charge neutrality. At Earth's orbit its typical density is 6 ions/cm³ (variable, as is the velocity), and it contains a variable interplanetary magnetic field (IMF) of (typically) 2–5 nT. The IMF is produced by stretched-out magnetic field lines originating on the Sun, a process described in the section on magnetic storms and plasma flows, referred to in what follows as simply MSPF.

Physical reasons (MSPF) make it difficult for solar wind plasma with its embedded IMF to mix with terrestrial plasma whose magnetic field has a different source. The two plasmas end up separated by a boundary, the magnetopause, and the Earth's plasma is confined to a cavity inside the flowing solar wind, the magnetosphere. The isolation is not complete, thanks to secondary processes such as magnetic reconnection (MSPF)—otherwise it would be hard for the solar wind to transmit much energy to the magnetosphere—but it still determines the overall configuration. The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ... Earth cutaway from core to exosphere. ... The Dynamo theory proposes a mechanism by which a celestial body such as the Earth generates a magnetic field. ... Johann Carl Friedrich Gauss (pronounced ,  ; in German usually Gauß, Latin: ) (30 April 1777 – 23 February 1855) was a German mathematician and scientist who contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, electrostatics, astronomy, and optics. ... SI unit. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... This article is about the astronomical term. ... For other uses, see Carbon (disambiguation). ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... This article is about the chemical element and its most stable form, or dioxygen. ... For other uses, see Neon (disambiguation). ... Not to be confused with Silicone. ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... General Name, symbol, number iron, Fe, 26 Chemical series transition metals Group, period, block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... The Interplanetary Magnetic Field (IMF) is the term for the Sun’s magnetic field among the planets of the Solar System. ... Magnetic reconnection is the process whereby magnetic field lines from different magnetic domains are spliced to one another, changing the overall topology of a magnetic field. ...

An additional feature is a collision-free bow shock which forms in the solar wind ahead of Earth, typically at 13.5 R_E on the sunward side. It forms because the solar velocity of the wind exceeds (typically 2–3 times) that of Alfvén waves, a family of characteristic waves with which disturbances propagate in a magnetized fluid. In the region behind the shock ("magnetosheath") the velocity drops briefly to the Alfvén velocity (and the temperature rises, absorbing lost kinetic energy), but the velocity soon rises back as plasma is dragged forward by the surrounding solar wind flow. In a planetary magnetosphere, the bow shock is the boundary at which the solar wind abruptly drops as a result of its approach to the magnetopause. ... A cluster of double layers forming in an Alfvén wave, about a sixth of the distance from the left. ...

To understand the magnetosphere, one needs to visualize its magnetic field lines, that everywhere point in the direction of the magnetic field—e.g., diverging out near the magnetic north pole (or geographic southpole), and converging again around the magnetic south pole (or the geographic northpole), where they enter the Earth. They are discussed in MSPF, but for now they can be visualized like wires which tie the magnetosphere together—wires that also guide the motions of trapped particles, which slide along them like beads (though other motions may also occur). For the indie-pop band, see The Magnetic Fields. ... Charged particle drifts in a homegenous magnetic field. ...

Radiation belts

When the first scientific satellites were launched in the first half of 1958--Explorers 1 and 3 by the US, Sputnik 3 by the Soviet Union--they observed an intense (and unexpected) radiation belt around Earth, held by its magnetic field. "My God, Space is Radioactive!" exclaimed one of Van Allen's colleagues, when the meaning of those observations was realized. That was the "inner radiation belt" of protons with energies in the range 10-100 MeV (megaelectronvolts), attributed later to "albedo neutron decay," a secondary effect of the interaction of cosmic radiation with the upper atmosphere. It is centered on field lines crossing the equator about 1.5 R_E from the Earth's center. Mission Description Explorer-III was nearly identical to Explorer I in design and mission. ... Sputnik 3 (Russian: , Satellite 3) was a Soviet satellite launched on May 15, 1958 from Baikonur cosmodrome by a modified R-7/SS-6 ICBM. It was a research satellite to explore the upper atmosphere and the near space. ... Van Allen radiation belts The Van Allen Radiation Belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earths magnetic field. ... James Van Allen at National Air & Space Museum (NASM), 1981, Photo courtesy of NASM. Explorer I model and Pioneer H probe in background James Alfred Van Allen (September 7, 1914 – August 9, 2006) was an American space scientist at the University of Iowa. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ...

Later a population of trapped ions and electrons was observed on field lines crossing the equator at 2.5–8 R_E. The high-energy part of that population (about 1 MeV) became known as the "outer radiation belt", but its bulk is at lower energies (peak about 65 keV) and is identified as the ring current plasma. A ring current is an electric current carried by charged particles trapped in a planets magnetosphere. ...

The trapping of charged particles in a magnetic field can be quite stable. This is particularly true in the inner belt, because the build-up of trapped protons from albedo neutrons is quite slow, requiring years to reach observed intensities. In July 1962, the United States tested an H-bomb high over the south pacific at around 400 Km in the upper atmosphere, in this region, creating an artificial belt of high-energy electrons, and some of them were still around 4–5 years later (such tests are now banned by treaty). The debris fireball stretching along Earths magnetic field [1] with air-glow aurora as seen at 3 minutes from a KC-135 surveillance aircraft The flash created by the explosion as seen through heavy cloud cover from Honolulu 1,300 km away Another view of Starfish Prime through thin...

The outer belt and ring current are less persistent, because charge-exchange collisions with atoms of the geocorona (see above) tends to remove their particles. That suggests the existence of an effective source mechanism, continually supplying this region with fresh plasma. It turns out that the magnetic barrier can be broken down by electric forces, as discussed in MSPF. If plasma is pushed hard enough, it generates electric fields which allow it to move in response to the push, often (not always) deforming the magnetic field in the process. In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ...

Magnetic tails

A view from the IMAGE satellite showing Earth's plasmasphere using its Extreme Ultraviolet (EUV) imager instrument.

A magnetic tail is formed by solar winds blowing electrified gases, plasma, trapped in a planet's magnetosphere away from the sun. The magnetic tail can extend great distances away from its originating planet. Earth's magnetic tail extends beyond the orbit of the Moon, while Jupiter's magnetic tail is believed to extend beyond the orbit of Saturn. The plasma in the tail is revolving, reaching the end of the tail and then folding back in on itself and returning to the planet it originated from. Image File history File links Earthmagnetictail. ... Image File history File links Earthmagnetictail. ... For other uses, see Plasma. ...

There are also gaps in the magnetic tail, called troughs, where no stream of material exists. These troughs change in size and location, and can reconnect at later points in the tail. The night-side magnetic tail can sometimes whip violently back, throwing large amounts of superheated plasma and highly charged particles at the originating planet. A crest is the point on a wave with the greatest positive value or upward displacement in a cycle. ...

Electric currents in space

Most people first encounter magnetism as a strange property of permanent magnets made of iron, or of a small range of ferromagnetic materials. Further experience may broaden this to also include electromagnets, but they too require a ferromagnetic core. In space, however, magnetic fields owe their existence solely to electric currents, with no role for ferromagnetism. Magnetism due to electric currents alone was first noted by Oersted and Ampère in 1820, and is a fundamental property of "Maxwell's Equations" (1864), the mathematical formulation of electromagnetism due to James Clerk Maxwell. Ferromagnetism in contrast is a somewhat unusual feature, associated among other things with the quantum theory of the electron, which grants it (apart from its electric charge) a "spin," and with it also the properties of a small magnetic dipole. Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... Hans Christian Ørsted Hans Christian Ørsted (August 14, 1777 in Rudkøbing – March 9, 1851 in Copenhagen) was a Danish physicist and chemist, influenced by the thinking of Immanuel Kant. ... André-Marie Ampère (January 20, 1775 – June 10, 1836), was a French physicist who is generally credited as one of the main discoverers of electromagnetism. ... For thermodynamic relations, see Maxwell relations. ... James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ...

Magnetic fields from currents that circulate in the magnetospheric plasma extend the Earth's magnetism much further in space than would be predicted from the Earth's internal field alone. Such currents also determine the field's structure far from Earth, creating the regions described in the introduction above.

Similarly, in everyday applications, electric currents always require a "voltage" to drive them, a sort of electric pressure difference (a pressure known as "electric potential"), similar to the pressure difference that drives water along a pipe. Ohm's law is observed to hold fairly well in metallic conductors used by electric technology (e.g. wires) and it predicts a current proportional to voltage. Double the voltage and the current doubles, remove it and no current can flow. Josephson junction array chip developed by NIST as a standard volt. ... This article is about the law related to electricity. ...

Not so in the magnetosphere (and in many plasmas) where currents (with one important exception) need no voltage to drive them. Any electric current is the transport of electric charge, but in many cases, such transport is already implied by the structure of the field and the plasma. For instance, electrons and positive ions trapped in the dipole-like field near the Earth tend to circulate around the magnetic axis of the dipole (the line connecting the magnetic poles), without gaining or losing energy (see MOT, also "Guiding center motion"). Viewed from above the magnetic north pole (geographic south), ions circulate clockwise, electrons counterclockwise, producing a net circulating clockwise current, known (from its shape) as the ring current. No voltage is needed--the current arises naturally from the motion of the ions and electrons in the magnetic field, as described in the MSPF. Charged particle drifts in a homegenous magnetic field. ... A ring current is an electric current carried by charged particles trapped in a planets magnetosphere. ...

Any such current will modify the magnetic field. The ring current, for instance, strengthens the field on its outside, helping expand the size of the magnetosphere. At the same time, it weakens the magnetic field in its interior. In a magnetic storm, plasma is added to the ring current, making it temporarily stronger, and the field at Earth is observed to weaken by up to 1-2%.

The deformation of the magnetic field, and the flow of electric currents in it, are intimately linked, making it often hard to label one as cause and the other as effect. Frequently (as in the magnetopause and the magnetotail) it is intuitively more useful to regard the distribution and flow of plasma as the primary effect, producing the observed magnetic structure, with the associated electric currents just one feature of those structures, more of a consistency requirement of the magnetic structure.

As noted, one exception (at least) exists, a case where voltages do drive currents. That happens with Birkeland currents, which flow from distant space into the near-polar ionosphere, continue at least some distance in the ionosphere, and then return to space. (Part of the current then detours and leaves Earth again along field lines on the morning side, flows across midnight as part of the ring current, then comes back to the ionosphere along field lines on the evening side and rejoins the pattern.) The full circuit of those currents, under various conditions, is still under debate. The aurora on Jupiter, powered by Jovian Birkeland currents [Ref. ...

Because the ionosphere is an ohmic conductor of sorts, such flow will heat it up. It will also give rise to secondary Hall currents, and accelerate magnetospheric particles--electrons in the arcs of the polar aurora, and singly-ionized oxygen ions (O+) which contribute to the ring current. Aurora borealis Aurora borealis The aurora is a glow observed in the night sky, usually in the polar zone. ...

Classification of magnetic fields

Schematic view of the different current systems which shape the Earth's magnetosphere

Regardless of whether they are viewed as sources or consequences of the magnetospheric field structure, electric currents flow in closed circuits. That makes them useful for classifying different parts of the magnetic field of the magnetosphere, each associated with a distinct type of circuit. In this way the field of the magnetosphere is often resolved into 5 distinct parts, as follows. Image File history File links Download high resolution version (984x765, 81 KB) Summary Schematic of the currents in the Earths magnetosphere, from The art of mapping the Earths magnetosphere by David P. Stern Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version... Image File history File links Download high resolution version (984x765, 81 KB) Summary Schematic of the currents in the Earths magnetosphere, from The art of mapping the Earths magnetosphere by David P. Stern Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version...

1. The internal field of the Earth ("main field") arising from electric currents in the core. It is dipole-like, modified by higher harmonic contributions.
2. The ring current field , carried by plasma trapped in the dipole-like field around Earth, typically at distances 3–8 R_E (less during large storms). Its current flows (approximately) around the magnetic equator, mainly clockwise when viewed from north. (A small counterclockwise ring current flows at the inner edge of the ring, caused by the fall-off in plasma density as Earth is approached).
3. The field confining the Earth's plasma and magnetic field inside the magnetospheric cavity. The currents responsible for it flow on the magnetopause, the interface between the magnetosphere and the solar wind, described in the introduction. Their flow, again, may be viewed as arising from the geometry of the magnetic field (rather than from any driving voltage), a consequence of "Ampére's law" (embodied in Maxwell's equations) which in this case requires an electric current to flow along any interface between magnetic fields of different directions and/or intensities.
   
4. The system of tail currents. The magnetotail consists of twin bundles of oppositely directed magnetic field (the "tail lobes"), directed earthwards in the northern half of the tail and away from Earth in the southern half. In between the two exists a layer ("plasma sheet") of denser plasma (0.3-0.5 ions/cm³ vs. 0.01-0.02 in the lobes), and because of the difference between the adjoining magnetic fields, by Ampére's law an electric current flows there too, directed from dawn to dusk. The flow closes (as it must) by following the tail magnetopause--part over the northern lobe, part over the southern one.
5. The Birkeland current field (and its branches in the ionosphere and ring current), a circuit is associated with the polar aurora. Unlike the 3 preceding current systems, it does require a constant input of energy, to provide the heating of its ionospheric path and the acceleration of auroral electrons and of positive ions. The energy probably comes from a dynamo process, meaning that part of the circuit threads a plasma moving relative to Earth, either in the solar wind and in "boundary layer" flows which it drives just inside the magnetopause, or by plasma moving earthward in the magnetotail, as observed during substorms (below).

Image File history File links Crosstail. ...

Magnetic substorms and storms

Earlier it was stated that "if plasma is pushed hard enough, it generates electric fields which allow it to move in response to the push, often (not always) deforming the magnetic field in the process." Two examples of such "pushing" are particularly important in the magnetosphere. The THEMIS mission is a NASA program to study in detail the physical processes involved in substorms. In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... THEMIS in orbit The THEMIS mission uses a constellation of five NASA satellites to study energy releases from Earths magnetosphere known as substorms, magnetic phenomena that intensify auroras near Earths poles. ... For other uses, see NASA (disambiguation). ...

The more common one occurs when the north-south component B_z of the interplanetary magnetic field (IMF) is appreciable and points southward. In this state field lines of the magnetosphere are relatively strongly linked to the IMF, allowing energy and plasma to enter it at relatively high rates. This swells up the magnetotail and makes it unstable. Ultimately the tail's structure changes abruptly and violently, a process known as a magnetic substorm.

Magnetic reconnection in the near-Earth magnetotail, producing a disconnected "plasmoid"

One possible scenario (the subject is still being debated) is as follows. As the magnetotail swells, it creates a wider obstacle to the solar wind flow, causing its widening portion to be squeezed more by the solar wind. In the end, this squeezing breaks apart field lines in the plasma sheet ("magnetic reconnection"), and the distant part of the sheet, no longer attached to the Earth, is swept away as an independent magnetic structure ("plasmoid"). The near-Earth part snaps back earthwards, energizing its particles and producing Birkeland currents and bright auroras. As observed in the 1970s by the ATS satellites at 6.6 R_E, when conditions are favorable that can happen up to several times a day. Image File history File links Download high resolution version (988x568, 91 KB)Schematic of the formation of a plasmoid in the Earths magnetotail, from A Brief History of Magnetospheric Physics during the Space Age by D.P. Stern File history Legend: (cur) = this is the current file, (del) = delete... Image File history File links Download high resolution version (988x568, 91 KB)Schematic of the formation of a plasmoid in the Earths magnetotail, from A Brief History of Magnetospheric Physics during the Space Age by D.P. Stern File history Legend: (cur) = this is the current file, (del) = delete... A plasmoid is a coherent structure of plasma and magnetic fields. ... Magnetic reconnection is the process whereby magnetic field lines from different magnetic domains are spliced to one another, changing the overall topology of a magnetic field. ... A plasmoid is a coherent structure of plasma and magnetic fields. ...

Substorms generally do not substantially add to the ring current. That happens in magnetic storms, when following an eruption on the sun (a "coronal mass ejection" or a "solar flare"—details are still being debated, see MSPF) a fast-moving plasma cloud hits the Earth. If the IMF has a southward component, this not only pushes the magnetopause boundary closer to Earth (at times to about half its usual distance), but it also produces an injection of plasma from the tail, much more vigorous than the one associated with substorms.

The plasma population of the ring current may now grow substantially, and a notable part of the addition consists of O+ oxygen ions extracted from the ionosphere as a by-product of the polar aurora. In addition, the ring current is driven earthward (which energizes its particles further), temporarily modifying the field around the Earth and thus shifting the aurora (and its current system) closer to the equator. The magnetic disturbance may decay within 1–3 days as many ions are removed by charge exchange, but the higher energies of the ring current can persist much longer. Aurora borealis Polar aurorae are optical phenomena characterized by colorful displays of light in the night sky. ...

See also

The Interplanetary Magnetic Field (IMF) is the term for the Sun’s magnetic field among the planets of the Solar System. ... The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ... In the most general sense, the geosphere is the region of space that is dominated by geogenic matter (originating from and bound to the Earth). ... Relationship of the atmosphere and ionosphere The ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. ... The plasmasphere is a layer of the Earths magnetosphere that is rich in plasma. ... A magnetopause flows along the boundary between a magnetic field, (see: magnetosphere) and surrounding plasma. ... The heliosphere is a bubble in space produced by the solar wind. ... The heliopause is the boundary between the heliosphere and the interstellar medium outside the solar system. ... A Plasma lamp In physics and chemistry, a plasma is an ionized gas, and is usually considered to be a distinct phase of matter. ... A ring current is an electric current carried by charged particles trapped in a planets magnetosphere. ... Van Allen radiation belts The Van Allen Radiation Belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earths magnetic field. ... A solar flare observed by Hinode in the G-band. ... A Magnetic storm is also known as a geomagnetic storm. ... Aurora borealis Polar aurorae are optical phenomena characterized by colorful displays of light in the night sky. ... Aurora australis observed by Discovery, May 1991. ... // Magnetic Field Lines     The region where magnetic forces can be detected is commonly known as a magnetic field, and similarly the presence of electric forces identifies an electric field. ... // Electric Fields     Even though magnetic field lines severely constrain the motion of individual particles, it is quite possible for a body of plasma--ions and electrons together--to move through a magnetic field with some common bulk velocity v. ... Jupiter has a very large and powerful magnetosphere. ... A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is any method used to change the velocity of spacecraft and artificial satellites. ... A magnetic sail or magsail is a proposed method of spacecraft propulsion. ... A magnetosphere is the region around an astronomical object, in which phenomena are dominated by its magnetic field. ... For other uses, see Wind (disambiguation). ... The Polar Satellite is a satellite launched by NASA on February 24, 1996 aboard a Boeing Delta II rocket from Vandenberg Air Force Base in California, to observe the polar magnetosphere. ... Look up image in Wiktionary, the free dictionary. ... Cluster satellite FM2 The Cluster mission is an European Space Agency (ESA) unmanned space mission mission to study the Earths magnetosphere using four identical spacecraft flying in a tetrahedral formation. ... For other uses of the term double star, see double star (disambiguation). ... THEMIS in orbit The THEMIS mission uses a constellation of five NASA satellites to study energy releases from Earths magnetosphere known as substorms, magnetic phenomena that intensify auroras near Earths poles. ... In the most general sense, the geosphere is the region of space that is dominated by geogenic matter (originating from and bound to the Earth). ... The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ... Aurora borealis Polar aurorae are optical phenomena characterized by colorful displays of light in the night sky. ... Atmospheric circulation is the large-scale movement of air, and the means (together with the ocean circulation, which is smaller [1]) by which heat is distributed on the surface of the Earth. ... For other uses, see jet stream (disambiguation). ... Relationship of the atmosphere and ionosphere The ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. ... The plasmasphere is a layer of the Earths magnetosphere that is rich in plasma. ... A magnetopause flows along the boundary between a magnetic field, (see: magnetosphere) and surrounding plasma. ... // Magnetic Field Lines     The region where magnetic forces can be detected is commonly known as a magnetic field, and similarly the presence of electric forces identifies an electric field. ... // Electric Fields     Even though magnetic field lines severely constrain the motion of individual particles, it is quite possible for a body of plasma--ions and electrons together--to move through a magnetic field with some common bulk velocity v. ... Schematic of Earths magnetosphere. ... A ring current is an electric current carried by charged particles trapped in a planets magnetosphere. ... Van Allen radiation belts The Van Allen Radiation Belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earths magnetic field. ... The aurora on Jupiter, powered by Jovian Birkeland currents [Ref. ... The magnetosheath refers to the region of space between the magnetopause and the bow shock of a planets magnetosphere. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... The Interplanetary Magnetic Field (IMF) is the term for the Sun’s magnetic field among the planets of the Solar System. ... The heliosphere is a bubble in space produced by the solar wind. ... The heliopause is the boundary between the heliosphere and the interstellar medium outside the solar system. ... A solar flare observed by Hinode in the G-band. ... A Magnetic storm is also known as a geomagnetic storm. ... A composite image showing two CMEs (at 2 oclock and 8 oclock), with the sun at center. ... Heliospheric current sheet The Heliospheric current sheet (HCS) is the surface within the Solar System where the polarity of the Suns magnetic field changes from north to south. ... Aurora australis observed by Discovery, May 1991. ... GEOTAIL is a satellite observing magnetosphere of Earth. ... For other uses, see Wind (disambiguation). ... The Polar Satellite is a satellite launched by NASA on February 24, 1996 aboard a Boeing Delta II rocket from Vandenberg Air Force Base in California, to observe the polar magnetosphere. ... Look up image in Wiktionary, the free dictionary. ... Cluster satellite FM2 The Cluster mission is an European Space Agency (ESA) unmanned space mission mission to study the Earths magnetosphere using four identical spacecraft flying in a tetrahedral formation. ... For other uses of the term double star, see double star (disambiguation). ... In Greek mythology, Hesiod mentions Themis among the six sons and six daughters—of whom Cronos was one—of Gaia and Ouranos, that is, of Earth with Sky. ... Jupiter has a very large and powerful magnetosphere. ... A planetary ring is a ring of dust and other small particles orbiting around a planet in a flat disc-shaped region. ... A schema of Jupiters ring system showing the four main components The rings of Jupiter are a system of planetary rings around the planet Jupiter. ... The full set of rings, photographed as Saturn eclipsed the sun from the vantage of the Cassini spacecraft on September 15, 2006 (brightness has been exaggerated in this image). ... This is a list of the named planetary rings of Uranus. ... Neptune has a faint planetary ring system consisting of several distinct rings, and the unusual ring arcs present in the outer Adams ring. ... Jupiters gas toruses generated by Io (green) and Europa (blue) A gas torus is a form of planetary ring composed of gas rather than ice and dust. ... Flux tubes are strong porportions of magnetic fields shaped like tubes, usually surrounding large cosmic bodies such as stars. ...

References

• Introduction to Geomagnetically Trapped Radiation by Martin Walt (1994)
• Storms from the Sun by M. Carlowicz and R. Lopez"(2002)"
• D. P. Stern, M. Peredo (2004-09-28). The Exploration of the Earth's Magnetosphere (English). NASA. Retrieved on 2006-08-22.

One might be looking for Stephen Martin Walt (Political Science). ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 271st day of the year (272nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 234th day of the year (235th in leap years) in the Gregorian calendar. ...

External links

• USGS Geomagnetism Program
• Aurora borealis
• Storms from the Sun - The Emerging Science of Space Weather
• Magnetosphere: Earth's Magnetic Shield Against the Solar Wind
• Physics of the Aurora
• "3D Earth Magnetic Field Charged-Particle Simulator" Tool dedicated to the 3d simulation of charged particles in the magnetosphere.. [VRML Plug-in Required]