The visible surface of Jupiter is divided into several bands parallel to the equator. There are two types of bands: lightly colored "zones" and relatively dark "belts." The wider Equatorial Zone (EZ) extends between latitudes of approximately 7°S to 7°N. Above and below the EZ, the North and South Equatorial belts (NEB and SEB) extend to 18°N and 18°S, respectively. Farther from the equator lie the North and South Tropical zones (NtrZ and STrZ). The alternating pattern of belts and zones continues until the polar regions at approximately 50 degrees latitude, where their visible appearance becomes somewhat muted. The basic belt-zone structure probably extends well towards the poles, reaching at least to 80° North or South.
Zones, belts and jets
Atmosphere of Jupiter
Atmosphere of Jupiter | Zones, belts and jets
Lightly colored "zones" and relatively dark "belts." The dark bands are called "belts", while light ones are called "zones". The dark bands are called "belts", while light ones are called "zones". The dark bands are called "belts", and  the light ones are called "zones"
what are the alternating dark and light bands in jupiter’s atmosphere called
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The visible surface of Jupiter is divided into several bands parallel to the equator. There are two types of bands: lightly colored "zones" and relatively dark "belts." The wider Equatorial Zone (EZ) extends between latitudes of approximately 7°S to 7°N. Above and below the EZ, the North and South Equatorial belts (NEB and SEB) extend to 18°N and 18°S, respectively. Farther from the equator lie the North and South Tropical zones (NtrZ and STrZ). The alternating pattern of belts and zones continues until the polar regions at approximately 50 degrees latitude, where their visible appearance becomes somewhat muted. The basic belt-zone structure probably extends well towards the poles, reaching at least to 80° North or South.
Atmosphere of Jupiter | Zones, belts and jets
Each layer has characteristic temperature gradients. The lowest layer, the troposphere, has a complicated system of clouds and hazes, comprising layers of ammonia, ammonium hydrosulfide and water. The upper ammonia clouds visible at Jupiter's surface are organized in a dozen zonal bands parallel to the equator and are bounded by powerful zonal atmospheric flows (winds) known as "jets". The bands alternate in color: the dark bands are called "belts", while light ones are called "zones". Zones, which are colder than belts, correspond to upwellings, while belts mark descending gas. The zones' lighter color is believed to result from ammonia ice; what gives the belts their darker colors is uncertain.
Atmosphere of Jupiter | Introduction
The bands seen in the atmosphere of Jupiter are due to counter-circulating streams of material called zones and belts, encircling the planet parallel to its equator. The zones are the lighter bands, and are at higher altitudes in the atmosphere. They have an internal updraft and are high-pressure regions. The belts are the darker bands, are lower in the atmosphere, and have an internal downdraft. They are low-pressure regions. These structures are somewhat analogous to the high and low-pressure cells in Earth's atmosphere, but they have a very different structure—latitudinal bands that circle the entire planet, as opposed to small confined cells of pressure.
Giant planet | Atmospheres
The belts and zones that divide Jupiter's atmosphere each have their own names and unique characteristics. They begin below the North and South Polar Regions, which extend from the poles to roughly 40–48° N/S. These bluish-gray regions are usually featureless. The North North Temperate Region rarely shows more detail than the polar regions, due to limb darkening, foreshortening, and the general diffuseness of features. However, the North-North Temperate Belt (NNTB) is the northernmost distinct belt, though it occasionally disappears. Disturbances tend to be minor and short-lived. The North-North Temperate Zone (NNTZ) is perhaps more prominent, but also generally quiet. Other minor belts and zones in the region are occasionally observed.
Atmosphere of Jupiter | Specific bands
The Jovian bands are bounded by zonal atmospheric flows (winds), called "jets". The eastward (prograde) jets are found at the transition from zones to belts (going away from the equator), whereas westward (retrograde) jets mark the transition from belts to zones. Such flow velocity patterns mean that the zonal winds decrease in belts and increase in zones from the equator to the pole. Therefore, wind shear in belts is cyclonic, while in zones it is anticyclonic. The EZ is an exception to this rule, showing a strong eastward (prograde) jet and has a local minimum of the wind speed exactly at the equator.
Atmosphere of Jupiter | Zones, belts and jets
The difference in the appearance between zones and belts is caused by differences in the opacity of the clouds. Ammonia concentration is higher in zones, which leads to the appearance of denser clouds of ammonia ice at higher altitudes, which in turn leads to their lighter color. On the other hand, in belts clouds are thinner and are located at lower altitudes. The upper troposphere is colder in zones and warmer in belts. The exact nature of chemicals that make Jovian zones and bands so colorful is not known, but they may include complicated compounds of sulfur, phosphorus and carbon.
Atmosphere of Jupiter | Zones, belts and jets
The jet speeds are high on Jupiter, reaching more than 100 m/s. These speeds correspond to ammonia clouds located in the pressure range 0.7–1 bar. The prograde jets are generally more powerful than the retrograde jets. The vertical extent of jets is not known. They decay over two to three scale heights above the clouds, while below the cloud level, winds increase slightly and then remain constant down to at least 22 bar—the maximum operational depth reached by the Galileo Probe.
Atmosphere of Jupiter | Zones, belts and jets
The origins of the banded structure and jets are not well understood, though a "shallow model" and a "deep model" exist. The Jovian atmosphere shows a wide range of active phenomena, including band instabilities, vortices (cyclones and anticyclones), storms and lightning. The vortices reveal themselves as large red, white or brown spots (ovals). The largest two spots are the Great Red Spot (GRS) and Oval BA, which is also red. These two and most of the other large spots are anticyclonic. Smaller anticyclones tend to be white. Vortices are thought to be relatively shallow structures with depths not exceeding several hundred kilometers.
Atmosphere of Jupiter | Introduction
But analysis of "Cassini" imagery showed that individual storm cells of upwelling bright-white clouds, too small to see from Earth, pop up almost without exception in the dark belts. According to Anthony Del Genio of NASA's Goddard Institute for Space Studies, "the belts must be the areas of net-rising atmospheric motion on Jupiter, [so] the net motion in the zones has to be sinking." Other atmospheric observations included a swirling dark oval of high atmospheric haze, about the size of the Great Red Spot, near Jupiter's north pole. Infrared imagery revealed aspects of circulation near the poles, with bands of globe-encircling winds, with adjacent bands moving in opposite directions.
Cassini–Huygens | Jupiter flyby
Circulation in Jupiter's atmosphere is markedly different from that in the atmosphere of Earth. The interior of Jupiter is fluid and lacks any solid surface. Therefore, convection may occur throughout the planet's outer molecular envelope. As of 2008, a comprehensive theory of the dynamics of the Jovian atmosphere has not been developed. Any such theory needs to explain the following facts: the existence of narrow stable bands and jets that are symmetric relative to Jupiter's equator, the strong prograde jet observed at the equator, the difference between zones and belts, and the origin and persistence of large vortices such as the Great Red Spot.
Atmosphere of Jupiter | Dynamics
Analysis of "Cassini" imagery showed that the dark belts contain individual storm cells of upwelling bright-white clouds, too small to see from Earth. Anthony Del Genio of NASA's Goddard Institute for Space Studies said that "the belts must be the areas of net-rising atmospheric motion on Jupiter, [so] the net motion in the zones has to be sinking". Other atmospheric observations included a swirling dark oval of high atmospheric-haze, about the size of the Great Red Spot, near Jupiter's north pole. Infrared imagery revealed aspects of circulation near the poles, with bands of globe-encircling winds, and adjacent bands moving in opposite directions.
Exploration of Jupiter | "Cassini" (2000)
The North Temperate Region is part of a latitudinal region easily observable from Earth, and thus has a superb record of observation. It also features the strongest prograde jet stream on the planet—a westerly current that forms the southern boundary of the North Temperate Belt (NTB). The NTB fades roughly once a decade (this was the case during the "Voyager" encounters), making the North Temperate Zone (NTZ) apparently merge into the North Tropical Zone (NTropZ). Other times, the NTZ is divided by a narrow belt into northern and southern components.
Atmosphere of Jupiter | Specific bands
In the stratosphere, the temperatures rise to about 200 K at the transition into the thermosphere, at an altitude and pressure of around 320 km and 1 μbar. In the thermosphere, temperatures continue to rise, eventually reaching 1000 K at about 1000 km, where pressure is about 1 nbar.
Atmosphere of Jupiter | Vertical structure
In scientific literature, the 1 bar pressure level is usually chosen as a zero point for altitudes—a "surface" of Jupiter. As with Earth, the top atmospheric layer, the exosphere, does not have a well defined upper boundary. The density gradually decreases until it smoothly transitions into the interplanetary medium approximately 5,000 km above the "surface". The vertical temperature gradients in the Jovian atmosphere are similar to those of the atmosphere of Earth. The temperature of the troposphere decreases with height until it reaches a minimum at the tropopause, which is the boundary between the troposphere and stratosphere. On Jupiter, the tropopause is approximately 50 km above the visible clouds (or 1 bar level), where the pressure and temperature are about 0.1 bar and 110 K.
Atmosphere of Jupiter | Vertical structure
Jupiter is perpetually covered with clouds composed of ammonia crystals and possibly ammonium hydrosulfide. The clouds are located in the tropopause and are arranged into bands of different latitudes, known as tropical regions. These are sub-divided into lighter-hued "zones" and darker "belts". The interactions of these conflicting circulation patterns cause storms and turbulence. Wind speeds of 100 m/s (360 km/h) are common in zonal jets. The zones have been observed to vary in width, color and intensity from year to year, but they have remained sufficiently stable for scientists to give them identifying designations. The cloud layer is only about deep, and consists of at least two decks of clouds: a thick lower deck and a thin clearer region.
Jupiter | Cloud layers
A few flashes have been detected in polar regions, making Jupiter the second known planet after Earth to exhibit polar lightning. A Microwave Radiometer ("Juno") detected many more in 2018. Every 15–17 years Jupiter is marked by especially powerful storms. They appear at 23°N latitude, where the strongest eastward jet, that can reach 150 m/s, is located. The last time such an event was observed was in March–June 2007. Two storms appeared in the northern temperate belt 55° apart in longitude. They significantly disturbed the belt. The dark material that was shed by the storms mixed with clouds and changed the belt's color.
Atmosphere of Jupiter | Storms and lightning
The storms moved with a speed as high as 170 m/s, slightly faster than the jet itself, hinting at the existence of strong winds deep in the atmosphere.
Atmosphere of Jupiter | Storms and lightning
One of the most mysterious features in the atmosphere of Jupiter are hot spots. In them, the air is relatively free of clouds and heat can escape from the depths without much absorption. The spots look like bright spots in the infrared images obtained at the wavelength of about 5 μm. They are preferentially located in the belts, although there is a train of prominent hot spots at the northern edge of the Equatorial Zone. The "Galileo" Probe descended into one of those equatorial spots. Each equatorial spot is associated with a bright cloudy plume located to the west of it and reaching up to 10,000 km in size.
Atmosphere of Jupiter | Hot spots
The normal pattern of bands and zones is sometimes disrupted for periods of time. One particular class of disruption are long-lived darkenings of the South Tropical Zone, normally referred to as "South Tropical Disturbances" (STD). The longest lived STD in recorded history was followed from 1901 until 1939, having been first seen by Percy B. Molesworth on February 28, 1901. It took the form of darkening over part of the normally bright South Tropical zone. Several similar disturbances in the South Tropical Zone have been recorded since then.
Atmosphere of Jupiter | Disturbances
The atmosphere of Jupiter is classified into four layers, by increasing altitude: the troposphere, stratosphere, thermosphere and exosphere. Unlike the Earth's atmosphere, Jupiter's lacks a mesosphere. Jupiter does not have a solid surface, and the lowest atmospheric layer, the troposphere, smoothly transitions into the planet's fluid interior. This is a result of having temperatures and the pressures well above those of the critical points for hydrogen and helium, meaning that there is no sharp boundary between gas and liquid phases. Hydrogen becomes a supercritical fluid at a pressure of around 12 bar. Since the lower boundary of the atmosphere is ill-defined, the pressure level of 10 bars, at an altitude of about 90 km below 1 bar with a temperature of around 340 K, is commonly treated as the base of the troposphere.
Atmosphere of Jupiter | Vertical structure
Vortices have never been observed in the equatorial region of Jupiter (within 10° of latitude), where they are unstable. As on any rapidly rotating planet, Jupiter's anticyclones are high pressure centers, while cyclones are low pressure. The anticyclones in Jupiter's atmosphere are always confined within zones, where the wind speed increases in direction from the equator to the poles. They are usually bright and appear as white ovals. They can move in longitude, but stay at approximately the same latitude as they are unable to escape from the confining zone. The wind speeds at their periphery are about 100 m/s.
Atmosphere of Jupiter | Vortices
The deep model easily explains the strong prograde jet observed at the equator of Jupiter; the jets it produces are stable and do not obey the 2D stability criterion. However it has major difficulties; it produces a very small number of broad jets, and realistic simulations of 3D flows are not possible as of 2008, meaning that the simplified models used to justify deep circulation may fail to catch important aspects of the fluid dynamics within Jupiter. One model published in 2004 successfully reproduced the Jovian band-jet structure. It assumed that the molecular hydrogen mantle is thinner than in all other models; occupying only the outer 10% of Jupiter's radius.
Atmosphere of Jupiter | Deep models
In contrast to anticyclones, the Jovian cyclones tend to be small, dark and irregular structures. Some of the darker and more regular features are known as brown ovals (or badges). However the existence of a few long–lived large cyclones has been suggested. In addition to compact cyclones, Jupiter has several large irregular filamentary patches, which demonstrate cyclonic rotation. One of them is located to the west of the GRS (in its wake region) in the southern equatorial belt. These patches are called cyclonic regions (CR). The cyclones are always located in the belts and tend to merge when they encounter each other, much like anticyclones.
Atmosphere of Jupiter | Vortices
The deep model was first proposed by Busse in 1976. His model was based on another well-known feature of fluid mechanics, the Taylor–Proudman theorem. It holds that in any fast-rotating barotropic ideal liquid, the flows are organized in a series of cylinders parallel to the rotational axis. The conditions of the theorem are probably met in the fluid Jovian interior. Therefore, the planet's molecular hydrogen mantle may be divided into cylinders, each cylinder having a circulation independent of the others. Those latitudes where the cylinders' outer and inner boundaries intersect with the visible surface of the planet correspond to the jets; the cylinders themselves are observed as zones and belts.
Atmosphere of Jupiter | Deep models
Jupiter's atmosphere has multiple jet streams, caused by the convection cells that form the familiar banded color structure; on Jupiter, these convection cells are driven by internal heating. The factors that control the number of jet streams in a planetary atmosphere is an active area of research in dynamical meteorology. In models, as one increases the planetary radius, holding all other parameters fixed, the number of jet streams decreases.
Jet stream | Other planets
A typical vertical extent of Jovian storms is about 100 km; as they extend from a pressure level of about 5–7 bar, where the base of a hypothetical water cloud layer is located, to as high as 0.2–0.5 bar. Storms on Jupiter are always associated with lightning. The imaging of the night–side hemisphere of Jupiter by "Galileo" and "Cassini" spacecraft revealed regular light flashes in Jovian belts and near the locations of the westward jets, particularly at 51°N, 56°S and 14°S latitudes. On Jupiter lightning strikes are on average a few times more powerful than those on Earth. However, they are less frequent; the light power emitted from a given area is similar to that on Earth.
Atmosphere of Jupiter | Storms and lightning
The theories regarding the dynamics of the Jovian atmosphere can be broadly divided into two classes: shallow and deep. The former hold that the observed circulation is largely confined to a thin outer (weather) layer of the planet, which overlays the stable interior. The latter hypothesis postulates that the observed atmospheric flows are only a surface manifestation of deeply rooted circulation in the outer molecular envelope of Jupiter. As both theories have their own successes and failures, many planetary scientists think that the true theory will include elements of both models.
Atmosphere of Jupiter | Dynamics
Shallow models cannot explain how the observed atmospheric flows on Jupiter violate stability criteria. More elaborated multilayer versions of weather–layer models produce more stable circulation, but many problems persist. Meanwhile, the Galileo Probe found that the winds on Jupiter extend well below the water clouds at 5–7 bar and do not show any evidence of decay down to 22 bar pressure level, which implies that circulation in the Jovian atmosphere may in fact be deep.
Atmosphere of Jupiter | Shallow models
The first attempts to explain Jovian atmospheric dynamics date back to the 1960s. They were partly based on terrestrial meteorology, which had become well developed by that time. Those shallow models assumed that the jets on Jupiter are driven by small scale turbulence, which is in turn maintained by moist convection in the outer layer of the atmosphere (above the water clouds). The moist convection is a phenomenon related to the condensation and evaporation of water and is one of the major drivers of terrestrial weather. The production of the jets in this model is related to a well-known property of two dimensional turbulence—the so-called inverse cascade, in which small turbulent structures (vortices) merge to form larger ones.
Atmosphere of Jupiter | Shallow models
Jovian observer Elmer J. Reese labeled the dark sections AB, CD, and EF. The rifts expanded, shrinking the remaining segments of the STZ into the white ovals FA, BC, and DE. Ovals BC and DE merged in 1998, forming Oval BE. Then, in March 2000, BE and FA joined together, forming Oval BA. (see White ovals, below) Oval BA slowly began to turn red in August 2005. On February 24, 2006, Filipino amateur astronomer Christopher Go discovered the color change, noting that it had reached the same shade as the GRS. As a result, NASA writer Dr. Tony Phillips suggested it be called "Red Spot Jr." or "Red Jr."
Atmosphere of Jupiter | Oval BA
Physically, there is no clear boundary—the gas smoothly becomes hotter and denser as one descends. Rain-like droplets of helium and neon precipitate downward through the lower atmosphere, depleting the abundance of these elements in the upper atmosphere. Rainfalls of diamonds have been suggested to occur, as well as on Saturn and the ice giants Uranus and Neptune. The temperature and pressure inside Jupiter increase steadily inward, due to the Kelvin–Helmholtz mechanism. At the pressure level of 10 bars (1 MPa), the temperature is around . At the phase transition region where hydrogen—heated beyond its critical point—becomes metallic, it is calculated the temperature is and the pressure is 200 GPa.
Jupiter | Internal structure
In standard models of the Jovian interior, the mantle comprises the outer 20–30%. The driving of deep circulation is another problem. The deep flows can be caused both by shallow forces (moist convection, for instance) or by deep planet-wide convection that transports heat out of the Jovian interior. Which of these mechanisms is more important is not clear yet.
Atmosphere of Jupiter | Deep models
The ultimate result of the process described above is production of large scale elongated structures, which are parallel to the equator. The meridional extent of them appears to match the actual width of jets. Therefore, in shallow models vortices actually feed the jets and should disappear by merging into them. While these weather–layer models can successfully explain the existence of a dozen narrow jets, they have serious problems. A glaring failure of the model is the prograde (super-rotating) equatorial jet: with some rare exceptions shallow models produce a strong retrograde (subrotating) jet, contrary to observations. In addition, the jets tend to be unstable and can disappear over time.
Atmosphere of Jupiter | Shallow models
The feature was named Oval BA, and has been nicknamed Red Spot Junior. Observations of the Red Spot Jr. storm suggest Jupiter could be in a period of global climate change. This is hypothesized to be part of an approximately 70 year global climate cycle, characterized by the relatively rapid forming and subsequent slow erosion and merging of cyclonic and anticyclonic vortices in Jupiter's atmosphere. These vortices facilitate the heat exchange between poles and equator. If they have sufficiently eroded, heat exchange is strongly reduced and regional temperatures may shift by as much as 10 K, with the poles cooling down and the equator region heating up.
Extraterrestrial atmosphere | Jupiter
Early modern astronomers, using small telescopes, recorded the changing appearance of Jupiter's atmosphere. Their descriptive terms—belts and zones, brown spots and red spots, plumes, barges, festoons, and streamers—are still used. Other terms such as vorticity, vertical motion, cloud heights have entered in use later, in the 20th century. The first observations of the Jovian atmosphere at higher resolution than possible with Earth-based telescopes were taken by the "Pioneer" "10" and "11" spacecraft. The first truly detailed images of Jupiter's atmosphere were provided by the "Voyagers". The two spacecraft were able to image details at a resolution as low as 5 km in size in various spectra, and also able to create "approach movies" of the atmosphere in motion.
Atmosphere of Jupiter | Observational history
The clouds are composed of ammonia crystals and possibly ammonium hydrosulfide. The clouds are located in the tropopause and are arranged into bands of different latitudes, known as tropical regions. These are sub-divided into lighter-hued "zones" and darker "belts". The interactions of these conflicting circulation patterns cause storms and turbulence. The best-known feature of the cloud layer is the Great Red Spot, a persistent anticyclonic storm located 22° south of the equator that is larger than Earth. In 2000, an atmospheric feature formed in the southern hemisphere that is similar in appearance to the Great Red Spot, but smaller in size.
Extraterrestrial atmosphere | Jupiter
The internal heat may be important for the dynamics of the Jovian atmosphere. While Jupiter has a small obliquity of about 3°, and its poles receive much less solar radiation than its equator, the tropospheric temperatures do not change appreciably from the equator to poles. One explanation is that Jupiter's convective interior acts like a thermostat, releasing more heat near the poles than in the equatorial region. This leads to a uniform temperature in the troposphere. While heat is transported from the equator to the poles mainly via the atmosphere on Earth, on Jupiter deep convection equilibrates heat. The convection in the Jovian interior is thought to be driven mainly by the internal heat.
Atmosphere of Jupiter | Internal heat
The atmosphere of Jupiter is the largest planetary atmosphere in the Solar System. It is mostly made of molecular hydrogen and helium in roughly solar proportions; other chemical compounds are present only in small amounts and include methane, ammonia, hydrogen sulfide, and water. Although water is thought to reside deep in the atmosphere, its directly measured concentration is very low. The nitrogen, sulfur, and noble gas abundances in Jupiter's atmosphere exceed solar values by a factor of about three. The atmosphere of Jupiter lacks a clear lower boundary and gradually transitions into the liquid interior of the planet. From lowest to highest, the atmospheric layers are the troposphere, stratosphere, thermosphere and exosphere.
Atmosphere of Jupiter | Introduction
Although no images from within Jupiter's atmosphere have ever been taken, artistic representations typically assume that the planet's sky is blue, though dimmer than Earth's, because the sunlight there is on average 27 times fainter, at least in the upper reaches of the atmosphere. The planet's narrow rings might be faintly visible from latitudes above the equator. Further down into the atmosphere, the Sun would be obscured by clouds and haze of various colors, most commonly blue, brown, and red. Although theories abound on the cause of the colors, there is currently no unambiguous answer. From Jupiter, the Sun appears to cover only 5 arcminutes, less than a quarter of its size as seen from Earth.
Extraterrestrial sky | Jupiter
The storms on Jupiter are similar to thunderstorms on Earth. They reveal themselves via bright clumpy clouds about 1000 km in size, which appear from time to time in the belts' cyclonic regions, especially within the strong westward (retrograde) jets. In contrast to vortices, storms are short-lived phenomena; the strongest of them may exist for several months, while the average lifetime is only 3–4 days. They are believed to be due mainly to moist convection within Jupiter's troposphere. Storms are actually tall convective columns (plumes), which bring the wet air from the depths to the upper part of the troposphere, where it condenses in clouds.
Atmosphere of Jupiter | Storms and lightning
The plasma in the sheet co-rotates with the planet causing deformation of the dipole magnetic field into that of magnetodisk. Electrons within the plasma sheet generate a strong radio signature that produces bursts in the range of 0.6–30 MHz which are detectable from Earth with consumer-grade shortwave radio receivers. At about 75 Jupiter radii from the planet, the interaction of the magnetosphere with the solar wind generates a bow shock. Surrounding Jupiter's magnetosphere is a magnetopause, located at the inner edge of a magnetosheath—a region between it and the bow shock. The solar wind interacts with these regions, elongating the magnetosphere on Jupiter's lee side and extending it outward until it nearly reaches the orbit of Saturn.
Jupiter | Magnetosphere
The Galileo Probe, which suffered an antenna problem, saw less of Jupiter's atmosphere but at a better average resolution and a wider spectral bandwidth. Today, astronomers have access to a continuous record of Jupiter's atmospheric activity thanks to telescopes such as Hubble Space Telescope. These show that the atmosphere is occasionally wracked by massive disturbances, but that, overall, it is remarkably stable. The vertical motion of Jupiter's atmosphere was largely determined by the identification of trace gases by ground-based telescopes. Spectroscopic studies after the collision of Comet Shoemaker–Levy 9 gave a glimpse of the Jupiter's composition beneath the cloud tops.
Atmosphere of Jupiter | Observational history
"Cassini" made its closest approach to Jupiter on December 30, 2000, and made many scientific measurements. About 26,000 images of Jupiter, its faint rings, and its moons were taken during the six-month flyby. It produced the most detailed global color portrait of the planet yet (see image at right), in which the smallest visible features are approximately across. A major finding of the flyby, announced on March 6, 2003, was of Jupiter's atmospheric circulation. Dark "belts" alternate with light "zones" in the atmosphere, and scientists had long considered the zones, with their pale clouds, to be areas of upwelling air, partly because many clouds on Earth form where air is rising.
Cassini–Huygens | Jupiter flyby
As it does so, Jupiter appears to undergo retrograde motion with respect to the background stars. That is, for a period Jupiter seems to move backward in the night sky, performing a looping motion. Because the orbit of Jupiter is outside that of Earth, the phase angle of Jupiter as viewed from Earth never exceeds 11.5°: Jupiter always appears nearly fully illuminated when viewed through Earth-based telescopes. It was only during spacecraft missions to Jupiter that crescent views of the planet were obtained. A small telescope will usually show Jupiter's four Galilean moons and the prominent cloud belts across Jupiter's atmosphere.
Jupiter | Observation
According to a study by scientists at the University of California, Berkeley, between 1996 and 2006 the spot lost 15 percent of its diameter along its major axis. Xylar Asay-Davis, who was on the team that conducted the study, noted that the spot is not disappearing because "velocity is a more robust measurement because the clouds associated with the Red Spot are also strongly influenced by numerous other phenomena in the surrounding atmosphere."
Atmosphere of Jupiter | Great Red Spot
It can detect them at between 30 keV and 1 GeV, whereas JADE, another instrument on the spacecraft, is designed to observe below 30 keV. One of the concepts being studied is that energy from Jupiter's rotation is being converted into its atmosphere and magnetosphere. It is radiation hardened to collect "in situ" data on the planet's auroral magnetic field lines, the equatorial magnetosphere, and the polar ionosphere It was built by the Johns Hopkins University Applied Physics Laboratory (APL). One of the goals is to understand the aurora, and how particles are accelerated to such high speeds. One of the mysteries of Jupiter is that X-rays are emitted from the poles, but do not seem to come from the auroral ring.
JEDI | Introduction
The finite size of the planet means that the cascade can not produce structures larger than some characteristic scale, which for Jupiter is called the Rhines scale. Its existence is connected to production of Rossby waves. This process works as follows: when the largest turbulent structures reach a certain size, the energy begins to flow into Rossby waves instead of larger structures, and the inverse cascade stops. Since on the spherical rapidly rotating planet the dispersion relation of the Rossby waves is anisotropic, the Rhines scale in the direction parallel to the equator is larger than in the direction orthogonal to it.
Atmosphere of Jupiter | Shallow models
Jupiter's upper atmosphere is composed of about 75% hydrogen and 24% helium by mass, with the remaining 1% consisting of other elements. The interior contains denser materials such that the distribution is roughly 71% hydrogen, 24% helium and 5% other elements by mass. The atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. The outermost layer of the atmosphere contains crystals of frozen ammonia, possibly underlaid by a thin layer of water. Jupiter is covered with a cloud layer about 50 km deep.
Extraterrestrial atmosphere | Jupiter
The resulting large temperature differential destabilizes the atmosphere and thereby leads to the creation of new vortices.
Extraterrestrial atmosphere | Jupiter
The reconnection processes may correspond to the global reconfiguration events also observed by the Galileo spacecraft, which occurred regularly every 2–3 days. The reconfiguration events usually included rapid and chaotic variation of the magnetic field strength and direction, as well as abrupt changes in the motion of the plasma, which often stopped co-rotating and began flowing outward. They were mainly observed in the dawn sector of the night magnetosphere. The plasma flowing down the tail along the open field lines is called the planetary wind.
Magnetosphere of Jupiter | Interchange instability and reconnection
The atmosphere of Jupiter is home to hundreds of vortices—circular rotating structures that, as in the Earth's atmosphere, can be divided into two classes: cyclones and anticyclones. Cyclones rotate in the direction similar to the rotation of the planet (counterclockwise in the northern hemisphere and clockwise in the southern); anticyclones rotate in the reverse direction. However, unlike in the terrestrial atmosphere, anticyclones predominate over cyclones on Jupiter—more than 90% of vortices larger than 2000 km in diameter are anticyclones. The lifetime of Jovian vortices varies from several days to hundreds of years, depending on their size. For instance, the average lifetime of an anticyclone between 1000 and 6000 km in diameter is 1–3 years.
Atmosphere of Jupiter | Vortices
Hot spots generally have round shapes, although they do not resemble vortexes. The origin of hot spots is not clear. They can be either downdrafts, where the descending air is adiabatically heated and dried or, alternatively, they can be a manifestation of planetary scale waves. The latter hypotheses explains the periodical pattern of the equatorial spots.
Atmosphere of Jupiter | Hot spots
These colorful compounds, known as chromophores, mix with the warmer, lower deck of clouds. The zones are formed when rising convection cells form crystallizing ammonia that masks out these lower clouds from view.
Jupiter | Cloud layers
Different anticyclones located in one zone tend to merge when they approach each other. However Jupiter has two anticyclones that are somewhat different from all others. They are the Great Red Spot (GRS) and the Oval BA; the latter formed only in 2000. In contrast to white ovals, these structures are red, arguably due to dredging up of red material from the planet's depths. On Jupiter the anticyclones usually form through merges of smaller structures including convective storms (see below), although large ovals can result from the instability of jets. The latter was observed in 1938–1940, when a few white ovals appeared as a result of instability of the southern temperate zone; they later merged to form Oval BA.
Atmosphere of Jupiter | Vortices
In 2000, the "Cassini" probe, "en route" to Saturn, flew by Jupiter and provided some of the highest-resolution images ever taken of the planet. It made its closest approach on December 30, 2000, and made many scientific measurements. About 26,000 images of Jupiter were taken during the months-long flyby. It produced the most detailed global color portrait of Jupiter yet, in which the smallest visible features are approximately across. A major finding of the flyby, announced on March 5, 2003, was of Jupiter's atmospheric circulation. Dark belts alternate with light zones in the atmosphere, and the zones, with their pale clouds, had previously been considered by scientists to be areas of upwelling air, partly because on Earth clouds tend to be formed by rising air.
Exploration of Jupiter | "Cassini" (2000)
As has been known since 1966, Jupiter radiates much more heat than it receives from the Sun. It is estimated that the ratio of the thermal power emitted by the planet to the thermal power absorbed from the Sun is . The internal heat flux from Jupiter is , whereas the total emitted power is . The latter value is approximately equal to one billionth of the total power radiated by the Sun. This excess heat is mainly the primordial heat from the early phases of Jupiter's formation, but may result in part from the precipitation of helium into the core.
Atmosphere of Jupiter | Internal heat
The white ovals that were to become Oval BA formed in 1939. They covered almost 90 degrees of longitude shortly after their formation, but contracted rapidly during their first decade; their length stabilized at 10 degrees or less after 1965. Although they originated as segments of the STZ, they evolved to become completely embedded in the South Temperate Belt, suggesting that they moved north, "digging" a niche into the STB. Indeed, much like the GRS, their circulations were confined by two opposing jet streams on their northern and southern boundaries, with an eastward jet to their north and a retrograde westward one to the south.
Atmosphere of Jupiter | White ovals
The composition of Jupiter's atmosphere is similar to that of the planet as a whole. Jupiter's atmosphere is the most comprehensively understood of those of all the gas giants because it was observed directly by the "Galileo" atmospheric probe when it entered the Jovian atmosphere on December 7, 1995. Other sources of information about Jupiter's atmospheric composition include the Infrared Space Observatory (ISO), the "Galileo" and "Cassini" orbiters, and Earth-based observations. The two main constituents of the Jovian atmosphere are molecular hydrogen () and helium. The helium abundance is relative to molecular hydrogen by number of molecules, and its mass fraction is , which is slightly lower than the Solar System's primordial value.
Atmosphere of Jupiter | Chemical composition
The probe entered Jupiter's atmosphere at 22:04 UTC. Before the atmospheric entry, the probe discovered a new radiation belt above Jupiter's cloud tops. The atmosphere through which it subsequently descended was found to be much denser and hotter than expected. Jupiter was also found to have only half the amount of helium expected and the data did not support the three-layered cloud structure theory. Only one significant cloud layer was measured by the probe, but with many indications of smaller areas of increased particle densities along all of the trajectory. The probe detected less lightning, less water, but more winds than expected.
Galileo Probe | Results and end
Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, though helium comprises only about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of an oblate spheroid (it has a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope.
Jupiter | Introduction
Oval BA is a red storm in Jupiter's southern hemisphere similar in form to, though smaller than, the Great Red Spot (it is often affectionately referred to as "Red Spot Jr.", "Red Jr." or "The Little Red Spot"). A feature in the South Temperate Belt, Oval BA was first seen in 2000 after the collision of three small white storms, and has intensified since then. The formation of the three white oval storms that later merged into Oval BA can be traced to 1939, when the South Temperate Zone was torn by dark features that effectively split the zone into three long sections.
Atmosphere of Jupiter | Oval BA
Oscillation of electrons trapped in the magnetosphere of Jupiter produce strong radio signals, particularly bright in the decimeter band. The magnetosphere of Jupiter is responsible for intense episodes of radio emission from the planet's polar regions. Volcanic activity on Jupiter's moon Io injects gas into Jupiter's magnetosphere, producing a torus of particles about the planet. As Io moves through this torus, the interaction generates Alfvén waves that carry ionized matter into the polar regions of Jupiter. As a result, radio waves are generated through a cyclotron maser mechanism, and the energy is transmitted out along a cone-shaped surface. When Earth intersects this cone, the radio emissions from Jupiter can exceed the solar radio output.
Astronomical radio source | Jupiter
Jupiter's upper atmosphere is about 88–92% hydrogen and 8–12% helium by percent volume of gas molecules. A helium atom has about four times as much mass as a hydrogen atom, so the composition changes when described as the proportion of mass contributed by different atoms. Thus, Jupiter's atmosphere is approximately 75% hydrogen and 24% helium by mass, with the remaining one percent of the mass consisting of other elements. The atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. The outermost layer of the atmosphere contains crystals of frozen ammonia.
Jupiter | Composition
The current flowing from the ionosphere to the plasma sheet is especially strong when the corresponding part of the plasma sheet rotates slower than the planet. As mentioned above, co-rotation breaks down in the region located between 20 and 40 "R" from Jupiter. This region corresponds to the magnetodisk, where the magnetic field is highly stretched. The strong direct current flowing into the magnetodisk originates in a very limited latitudinal range of about ° from the Jovian magnetic poles. These narrow circular regions correspond to Jupiter's main auroral ovals. (See below.) The return current flowing from the outer magnetosphere beyond 50 "R" enters the Jovian ionosphere near the poles, closing the electrical circuit.
Magnetosphere of Jupiter | Co-rotation and radial currents
The atmosphere is at a pressure of one bar at an altitude of 1.29 Jupiter radii above the planet's center. Where the pressure is 33±5 millibars, the atmosphere is clear (probably hydrogen) and its Rayleigh effect is detectable. At that pressure the temperature is 2200±260 K. Observations by the orbiting Microvariability and Oscillations of STars telescope initially limited the planet's albedo (or reflectivity) below 0.3, making it a surprisingly dark object. (The geometric albedo has since been measured to be 0.038 ± 0.045.) In comparison, Jupiter has a much higher albedo of 0.52. This would suggest that HD 209458 b's upper cloud deck is either made of less reflective material than is Jupiter's, or else has no clouds and Rayleigh-scatters incoming radiation like Earth's dark ocean.
HD 209458 b | Stratosphere and upper clouds
Jupiter's internal magnetic field prevents the solar wind, a stream of ionized particles emitted by the Sun, from interacting directly with its atmosphere, and instead diverts it away from the planet, effectively creating a cavity in the solar wind flow, called a magnetosphere, composed of a plasma different from that of the solar wind. The Jovian (i.e. pertaining to Jupiter) magnetosphere is so large that the Sun and its visible corona would fit inside it with room to spare. If one could see it from Earth, it would appear five times larger than the full moon in the sky despite being nearly 1700 times farther away.
Magnetosphere of Jupiter | Size and shape
The GRS rotates counter-clockwise, with a period of about six Earth days or 14 Jovian days. Its dimensions are 24,000–40,000 km east-to-west and 12,000–14,000 km north-to-south. The spot is large enough to contain two or three planets the size of Earth. At the start of 2004, the Great Red Spot had approximately half the longitudinal extent it had a century ago, when it was 40,000 km in diameter. At the present rate of reduction, it could potentially become circular by 2040, although this is unlikely because of the distortion effect of the neighboring jet streams. It is not known how long the spot will last, or whether the change is a result of normal fluctuations.
Atmosphere of Jupiter | Great Red Spot
Storms such as this are common within the turbulent atmospheres of giant planets. Jupiter also has white ovals and brown ovals, which are lesser unnamed storms. White ovals tend to consist of relatively cool clouds within the upper atmosphere. Brown ovals are warmer and located within the "normal cloud layer". Such storms can last as little as a few hours or stretch on for centuries.
Jupiter | Great Red Spot and other vortices
These electrons carry field aligned currents, which maintain the plasma's co-rotation in the magnetodisk. The potential drops develop because the sparse plasma outside the equatorial sheet can only carry a current of a limited strength without driving instabilities and producing potential drops. The precipitating electrons have energy in the range 10–100 keV and penetrate deep into the atmosphere of Jupiter, where they ionize and excite molecular hydrogen causing ultraviolet emission. The total energy input into the ionosphere is 10–100 TW. In addition, the currents flowing in the ionosphere heats it by the process known as Joule heating. This heating, which produces up to 300 TW of power, is responsible for the strong infrared radiation from the Jovian aurorae and partially for the heating of the thermosphere of Jupiter.
Magnetosphere of Jupiter | Aurorae
It is believed that the Jovian atmosphere could be a historical record for celestial objects that vaporize in its atmosphere, providing data about the composition of the Solar System. Since the atmosphere of Jupiter is the deepest among all the planets in the Solar System, it can help experts better understand flow dynamics, cloud microphysics and radiative transfer under conditions far different than those on Earth.
SMARA (spacecraft) | Sciences
Spots were found to correspond to the Galilean moons: Io, Europa, Ganymede and Callisto. They develop because the co-rotation of the plasma interacts with the moons and is slowed in their vicinity. The brightest spot belongs to Io, which is the main source of the plasma in the magnetosphere (see above). The Ionian auroral spot is thought to be related to Alfvén currents flowing from the Jovian to Ionian ionosphere. Europa's is similar but much dimmer, because it has a more tenuous atmosphere and is a weaker plasma source. Europa's atmosphere is produced by sublimation of water ice from its surfaces, rather than the volcanic activity which produces Io's atmosphere.
Magnetosphere of Jupiter | Aurorae
The reason for this low abundance is not entirely understood, but some of the helium may have condensed into the core of Jupiter. This condensation is likely to be in the form of helium rain: as hydrogen turns into the metallic state at depths of more than 10,000 km, helium separates from it forming droplets which, being denser than the metallic hydrogen, descend towards the core. This can also explain the severe depletion of neon (see Table), an element that easily dissolves in helium droplets and would be transported in them towards the core as well.
Atmosphere of Jupiter | Chemical composition
Another reason could be the presence in the atmosphere of light-absorbing chemicals such as vaporized sodium, potassium, or gaseous titanium oxide; however, Kipping and Spiegel excluded heavy oxides of titanium and vanadium from their models, as it seems unrealistic that condensed, heavy compounds be present in the upper atmosphere. They also note that in general, hot Jupiters are expected to be dark, because "absorption due to the broad wings of the sodium and potassium D lines is thought to dominate their visible spectra", and, apart from that of Kepler-7b (), albedo measurements for hot Jupiters have generally given only upper limits.
TrES-2b | Albedo
Jupiter's atmosphere is lined with hundreds of vortices most likely to be cyclones, or anticyclones, similar to those on Earth. Voyager and Cassini discovered that, unlike the terrestrial atmosphere, 90% of Jovian vortices are anticyclones, meaning they rotate in the opposite direction of the planet's rotation. Many cyclones have showed up and disappeared over the years with some even merging to form larger cyclones. When NASA's Juno Spacecraft arrived at Jupiter in 2016, it observed giant cyclones encircling the north and south poles of the planet. Nine large cyclones were spotted around the north pole and 6 around the south pole.
Extraterrestrial vortex | <a href="Jupiter">Jupiter</a>
As with Earth's magnetosphere, the boundary separating the denser and colder solar wind's plasma from the hotter and less dense one within Jupiter's magnetosphere is called the magnetopause. The distance from the magnetopause to the center of the planet is from 45 to 100 "R" (where "R"=71,492 km is the radius of Jupiter) at the subsolar point—the unfixed point on the surface at which the Sun would appear directly overhead to an observer. The position of the magnetopause depends on the pressure exerted by the solar wind, which in turn depends on solar activity. In front of the magnetopause (at a distance from 80 to 130 "R" from the planet's center) lies the bow shock, a wake-like disturbance in the solar wind caused by its collision with the magnetosphere.
Magnetosphere of Jupiter | Size and shape
This appears to be a result of the rapid rotation and underlying symmetry of the planet. There are no oceans or landmasses to cause local heating and the rotation speed is much higher than that of Earth. There are smaller structures as well: spots of different sizes and colors. On Jupiter, the most noticeable of these features is the Great Red Spot, which has been present for at least 300 years. These structures are huge storms. Some such spots are thunderheads as well.
Giant planet | Atmospheres
Other notable features of Jupiter are its cyclones near the northern and southern poles of the planet. These are called circumpolar cyclones (CPCs) and they have been observed by the Juno Spacecraft using JunoCam and JIRAM. The cyclones have only been observed for a relatively short time from perjoves 1-15 which is approximately 795 days or two years. The northern pole has eight cyclones moving around a central cyclone (NPC) while the southern pole only has five cyclones around a central cyclone (SPC), with a gap between the first and second cyclones. The cyclones look like the hurricanes on Earth with trailing spiral arms and a denser center, although there are differences between the centers depending on the individual cyclone.
Atmosphere of Jupiter | Circumpolar cyclones
Jupiter was expected to either consist of a dense core, a surrounding layer of liquid metallic hydrogen (with some helium) extending outward to about 78% of the radius of the planet, and an outer atmosphere consisting predominantly of molecular hydrogen, or perhaps to have no core at all, consisting instead of denser and denser fluid (predominantly molecular and metallic hydrogen) all the way to the center, depending on whether the planet accreted first as a solid body or collapsed directly from the gaseous protoplanetary disk. However, the "Juno" mission, which arrived in July 2016, found that Jupiter has a very diffuse core, mixed into the mantle.
Jupiter | Internal structure
They also confirmed that the Great Red Spot was anticyclonic. Comparison of images showed that the Red Spot had changed hue since the Pioneer missions, turning from orange to dark brown. A torus of ionized atoms was discovered along Io's orbital path, and volcanoes were found on the moon's surface, some in the process of erupting. As the spacecraft passed behind the planet, it observed flashes of lightning in the night side atmosphere. The next mission to encounter Jupiter was the "Ulysses" solar probe. It performed a flyby maneuver to attain a polar orbit around the Sun. During this pass, the spacecraft conducted studies on Jupiter's magnetosphere.
Jupiter | Flyby missions
The presence of diatomic sulfur (S) and carbon disulfide (CS) was recorded—the first detection of either in Jupiter, and only the second detection of S in any astronomical object— together with other molecules such as ammonia (NH) and hydrogen sulfide (HS), while oxygen-bearing molecules such as sulfur dioxide were not detected, to the surprise of astronomers.
Atmosphere of Jupiter | Observational history
The region between the bow shock and magnetopause is called the magnetosheath. At the opposite side of the planet, the solar wind stretches Jupiter's magnetic field lines into a long, trailing magnetotail, which sometimes extends well beyond the orbit of Saturn. The structure of Jupiter's magnetotail is similar to Earth's. It consists of two lobes (blue areas in the figure), with the magnetic field in the southern lobe pointing toward Jupiter, and that in the northern lobe pointing away from it. The lobes are separated by a thin layer of plasma called the tail current sheet (orange layer in the middle).
Magnetosphere of Jupiter | Size and shape
Jupiter's extensive magnetosphere envelops its ring system and the orbits of all four Galilean satellites. Orbiting near the magnetic equator, these bodies serve as sources and sinks of magnetospheric plasma, while energetic particles from the magnetosphere alter their surfaces. The particles sputter off material from the surfaces and create chemical changes via radiolysis. The plasma's co-rotation with the planet means that the plasma preferably interacts with the moons' trailing hemispheres, causing noticeable hemispheric asymmetries. Close to Jupiter, the planet's rings and small moons absorb high-energy particles (energy above 10 keV) from the radiation belts. This creates noticeable gaps in the belts' spatial distribution and affects the decimetric synchrotron radiation.
Magnetosphere of Jupiter | Interaction with rings and moons
Data from this mission revealed that hydrogen composes up to 90% of Jupiter's atmosphere. The recorded temperature was more than 300 °C (>570 °F) and the windspeed measured more than 644 km/h (>400 mph) before the probes vapourised.
Jupiter | "Galileo" mission
Jupiter's internal magnetic field is generated by electrical currents in the planet's outer core, which is composed of liquid metallic hydrogen. Volcanic eruptions on Jupiter's moon Io eject large amounts of sulfur dioxide gas into space, forming a large torus around the planet. Jupiter's magnetic field forces the torus to rotate with the same angular velocity and direction as the planet. The torus in turn loads the magnetic field with plasma, in the process stretching it into a pancake-like structure called a magnetodisk. In effect, Jupiter's magnetosphere is internally driven, shaped primarily by Io's plasma and its own rotation, rather than by the solar wind as at Earth's magnetosphere.
Magnetosphere of Jupiter | Introduction
Its instruments detected a fireball that reached a peak temperature of about 24,000 K, compared to the typical Jovian cloudtop temperature of about 130 K (−143 °C), with the plume from the fireball reaching a height of over 3,000 km. An atmospheric probe was released from the spacecraft in July 1995, entering the planet's atmosphere on December 7, 1995. After a high-g descent into the Jovian atmosphere, the probe discarded the remains of its heat shield, and it parachuted through 150 km of the atmosphere, collecting data for 57.6 minutes, before being crushed by the pressure and temperature to which it was subjected (about 22 times Earth normal, at a temperature of 153 °C).
Exploration of Jupiter | "Galileo" (1995–2003)
Because the inner moons of Jupiter are in synchronous rotation around Jupiter, the planet always appears in nearly the same spot in their skies (Jupiter would wiggle a bit because of the non-zero eccentricities). Observers on the sides of the Galilean satellites facing away from the planet would never see Jupiter, for instance. From the moons of Jupiter, solar eclipses caused by the Galilean satellites would be spectacular, because an observer would see the circular shadow of the eclipsing moon travel across Jupiter's face.
Extraterrestrial sky | The skies of Jupiter's moons
These ions either escape from the satellite's atmosphere or are produced from neutral atoms and molecules which have escaped from the satellite. They form the "Io plasma torus": a thick and relatively cool ring of plasma encircling Jupiter, located near Io's orbit. The plasma temperature within the torus is 10–100 eV (100,000–1,000,000 K), which is much lower than that of the particles in the radiation belts—10 keV (100 million K). The plasma in the torus is forced into co-rotation with Jupiter, meaning both share the same period of rotation. The Io torus fundamentally alters the dynamics of the Jovian magnetosphere.
Magnetosphere of Jupiter | Role of Io
Jupiter has the largest planetary atmosphere in the Solar System, spanning over in altitude. Because Jupiter has no surface, the base of its atmosphere is usually considered to be the point at which atmospheric pressure is equal to .
Jupiter | Atmosphere
The particles originate in the main ring; however, when they drift toward Jupiter, their orbits are modified by the strong 3:2 Lorentz resonance located at 1.71 "R", which increases their inclinations and eccentricities. Another 2:1 Lorentz resonance at 1.4 Rj defines the inner boundary of the halo ring. All Galilean moons have thin atmospheres with surface pressures in the range 0.01–1 nbar, which in turn support substantial ionospheres with electron densities in the range of 1,000–10,000 cm. The co-rotational flow of cold magnetospheric plasma is partially diverted around them by the currents induced in their ionospheres, creating wedge-shaped structures known as Alfvén wings.
Magnetosphere of Jupiter | Interaction with rings and moons
There may also be a thin layer of water clouds underlying the ammonia layer. Supporting the idea of water clouds are the flashes of lightning detected in the atmosphere of Jupiter. These electrical discharges can be up to a thousand times as powerful as lightning on Earth. The water clouds are assumed to generate thunderstorms in the same way as terrestrial thunderstorms, driven by the heat rising from the interior. The orange and brown coloration in the clouds of Jupiter are caused by upwelling compounds that change color when they are exposed to ultraviolet light from the Sun. The exact makeup remains uncertain, but the substances are thought to be phosphorus, sulfur or possibly hydrocarbons.
Jupiter | Cloud layers
The load of plasma from Io greatly expands the size of the Jovian magnetosphere, because the magnetodisk creates an additional internal pressure which balances the pressure of the solar wind. In the absence of Io the distance from the planet to the magnetopause at the subsolar point would be no more than 42 "R", whereas it is actually 75 "R" on average. The configuration of the magnetodisk's field is maintained by the azimuthal ring current (not an analog of Earth's ring current), which flows with rotation through the equatorial plasma sheet. The Lorentz force resulting from the interaction of this current with the planetary magnetic field creates a centripetal force, which keeps the co-rotating plasma from escaping the planet.
Magnetosphere of Jupiter | Magnetodisk
Current data shows that the SPC shows a positional variation between 1˚ and 2.5˚ in the latitude and stays between 200˚ to 250˚ longitude and has shown evidence of this recurring approximately every 320 days. The southern cyclones tend to behave similarly to the northern ones and maintain the pentagonal structure around the SPC, but there is some individual movement from some of the CPCs. The southern cyclones don't move around the south pole, but their rotation is more steady around the SPC, which is offset from the pole. Short term observation shows that the southern cyclones move approximately 1.5˚ per perijove, which is small compared to the wind speeds of the cyclones and the turbulent atmosphere of Jupiter.
Atmosphere of Jupiter | Circumpolar cyclones
The strongest part of decametric emission, which is related to Io and to the Io–Jupiter current system, is called Io-DAM. The majority of these emissions are thought to be produced by a mechanism called "cyclotron maser instability", which develops close to the auroral regions. Electrons moving parallel to the magnetic field precipitate into the atmosphere while those with a sufficient perpendicular velocity are reflected by the converging magnetic field. This results in an unstable velocity distribution. This velocity distribution spontaneously generates radio waves at the local electron cyclotron frequency. The electrons involved in the generation of radio waves are probably those carrying currents from the poles of the planet to the magnetodisk.
Magnetosphere of Jupiter | Jupiter at radio wavelengths
Jupiter's magnetic field is fourteen times as strong as that of Earth, ranging from 4.2 gauss (0.42 mT) at the equator to 10–14 gauss (1.0–1.4 mT) at the poles, making it the strongest in the Solar System (except for sunspots). This field is thought to be generated by eddy currents—swirling movements of conducting materials—within the liquid metallic hydrogen core. The volcanoes on the moon Io emit large amounts of sulfur dioxide forming a gas torus along the moon's orbit. The gas is ionized in the magnetosphere producing sulfur and oxygen ions. They, together with hydrogen ions originating from the atmosphere of Jupiter, form a plasma sheet in Jupiter's equatorial plane.
Jupiter | Magnetosphere
The main problem encountered in deciphering the dynamics of the Jovian magnetosphere is the transport of heavy cold plasma from the Io torus at 6 "R" to the outer magnetosphere at distances of more than 50 "R". The precise mechanism of this process is not known, but it is hypothesized to occur as a result of plasma diffusion due to interchange instability. The process is similar to the Rayleigh-Taylor instability in hydrodynamics. In the case of the Jovian magnetosphere, centrifugal force plays the role of gravity; the heavy liquid is the cold and dense Ionian (i.e. pertaining to Io) plasma, and the light liquid is the hot, much less dense plasma from the outer magnetosphere.
Magnetosphere of Jupiter | Interchange instability and reconnection
Jupiter's magnetosphere is a complex structure comprising a bow shock, magnetosheath, magnetopause, magnetotail, magnetodisk, and other components. The magnetic field around Jupiter emanates from a number of different sources, including fluid circulation at the planet's core (the internal field), electrical currents in the plasma surrounding Jupiter and the currents flowing at the boundary of the planet's magnetosphere. The magnetosphere is embedded within the plasma of the solar wind, which carries the interplanetary magnetic field.
Magnetosphere of Jupiter | Structure
Jupiter demonstrates bright, persistent aurorae around both poles. Unlike Earth's aurorae, which are transient and only occur at times of heightened solar activity, Jupiter's aurorae are permanent, though their intensity varies from day to day. They consist of three main components: the main ovals, which are bright, narrow (less than 1000 km in width) circular features located at approximately 16° from the magnetic poles; the satellites' auroral spots, which correspond to the footprints of the magnetic field lines connecting Jupiter's ionosphere with those of its largest moons, and transient polar emissions situated within the main ovals (elliptical field may prove to be a better description).
Magnetosphere of Jupiter | Aurorae
A current called the direct current flows along the magnetic field lines from the ionosphere to the equatorial plasma sheet. This current then flows radially away from the planet within the equatorial plasma sheet and finally returns to the planetary ionosphere from the outer reaches of the magnetosphere along the field lines connected to the poles. The currents that flow along the magnetic field lines are generally called field-aligned or Birkeland currents. The radial current interacts with the planetary magnetic field, and the resulting Lorentz force accelerates the magnetospheric plasma in the direction of planetary rotation. This is the main mechanism that maintains co-rotation of the plasma in Jupiter's magnetosphere.
Magnetosphere of Jupiter | Co-rotation and radial currents
Meanwhile, the energetic particles are largely unaffected by the Alfvén wings and have free access to the moons' surfaces (except Ganymede's).
Magnetosphere of Jupiter | Interaction with rings and moons
The intensity of Jovian radio emissions usually varies smoothly with time. However, there are short and powerful bursts (S bursts) of emission superimposed on the more gradual variations and which can outshine all other components. The total emitted power of the DAM component is about 100 GW, while the power of all other HOM/KOM components is about 10 GW. In comparison, the total power of Earth's radio emissions is about 0.1 GW. Jupiter's radio and particle emissions are strongly modulated by its rotation, which makes the planet somewhat similar to a pulsar. This periodical modulation is probably related to asymmetries in the Jovian magnetosphere, which are caused by the tilt of the magnetic moment with respect to the rotational axis as well as by high-latitude magnetic anomalies.
Magnetosphere of Jupiter | Jupiter at radio wavelengths