Vortex
Overview
 
A vortex is a spinning
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...

, often turbulent
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...

,
flow of fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....

. Any spiral
Spiral
In mathematics, a spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.-Spiral or helix:...

 motion with closed streamlines
Streamlines, streaklines and pathlines
Fluid flow is characterized by a velocity vector field in three-dimensional space, within the framework of continuum mechanics. Streamlines, streaklines and pathlines are field lines resulting from this vector field description of the flow...

 is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex. The speed and rate of rotation
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...

 of the fluid in a free (irrotational) vortex are greatest at the center, and decrease progressively with distance from the center, whereas the speed of a forced (rotational) vortex is zero at the center and increases proportional to the distance from the center.
Encyclopedia
A vortex is a spinning
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...

, often turbulent
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...

,
flow of fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....

. Any spiral
Spiral
In mathematics, a spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.-Spiral or helix:...

 motion with closed streamlines
Streamlines, streaklines and pathlines
Fluid flow is characterized by a velocity vector field in three-dimensional space, within the framework of continuum mechanics. Streamlines, streaklines and pathlines are field lines resulting from this vector field description of the flow...

 is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex. The speed and rate of rotation
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...

 of the fluid in a free (irrotational) vortex are greatest at the center, and decrease progressively with distance from the center, whereas the speed of a forced (rotational) vortex is zero at the center and increases proportional to the distance from the center. Both types of vortices exhibit a pressure minimum at the center, though the pressure minimum in a free vortex is much lower.

Properties

Vortices display some special properties:
  • The fluid pressure in a vortex is lowest in the center and rises progressively with distance from the center. This is in accordance with Bernoulli's Principle
    Bernoulli's principle
    In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy...

    . The core of a vortex in air is sometimes visible because of a plume of water vapor caused by condensation
    Condensation
    Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....

     in the low pressure of the core. The spout of a tornado
    Tornado
    A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...

     is a classic and frightening example of the visible core of a vortex. A dust devil
    Dust devil
    A dust devil is a strong, well-formed, and relatively long-lived whirlwind, ranging from small to large . The primary vertical motion is upward...

     is also the core of a vortex, made visible by the dust drawn upwards by the turbulent flow of air from ground level into the low pressure core.
  • The core of every vortex can be considered to contain a vortex line, and every particle in the vortex can be considered to be circulating around the vortex line. Vortex lines can start and end at the boundary of the fluid or form closed loops. They cannot start or end in the fluid. (See Helmholtz's theorems
    Helmholtz's theorems
    In fluid mechanics, Helmholtz's theorems, named after Hermann von Helmholtz, describe the three-dimensional motion of fluid in the vicinity of vortex filaments...

    .) Vortices readily deflect and attach themselves to a solid surface. For example, a vortex usually forms ahead of the propeller disk
    Propeller
    A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...

     or jet engine
    Jet engine
    A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...

     of a slow-moving airplane
    Fixed-wing aircraft
    A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

    . One end of the vortex line is attached to the propeller disk or jet engine, but when the airplane is taxiing the other end of the vortex line readily attaches itself to the ground rather than end in midair. The vortex can suck water and small stones into the core and then into the propeller disk or jet engine.
  • Two or more vortices that are approximately parallel and circulating in the same direction will merge to form a single vortex. The circulation of the merged vortex will equal the sum of the circulations of the constituent vortices. For example, a sheet of small vortices flows from the trailing edge of the wing or propeller of an airplane when the wing is developing lift
    Lift (force)
    A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...

     or the propeller is developing thrust
    Thrust
    Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....

    . In less than one wing chord
    Chord (aircraft)
    In aeronautics, chord refers to the imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil...

     downstream of the trailing edge of the wing these small vortices merge to form a single vortex. If viewed from the tail of the airplane, looking forward in the direction of flight, there is one wingtip vortex
    Wingtip vortices
    Wingtip vortices are tubes of circulating air that are left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing. The cores of vortices spin at very high speed and are regions of very low pressure...

     trailing from the left-hand wing and circulating clockwise, and another wingtip vortex trailing from the right-hand wing and circulating anti-clockwise. The result is a region of downwash behind the wing, between the pair of wingtip vortices
    Wingtip vortices
    Wingtip vortices are tubes of circulating air that are left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing. The cores of vortices spin at very high speed and are regions of very low pressure...

    . These two wingtip vortices
    Wingtip vortices
    Wingtip vortices are tubes of circulating air that are left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing. The cores of vortices spin at very high speed and are regions of very low pressure...

     do not merge because they are circulating in opposite directions.
  • Vortices contain a lot of energy in the circular motion of the fluid. In an ideal fluid this energy can never be dissipated and the vortex would persist forever. However, real fluids exhibit viscosity
    Viscosity
    Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

     and this dissipates energy very slowly from the core of the vortex. (See Rankine vortex
    Rankine vortex
    The Rankine vortex model is an attempt to describe the velocity profile through vortices in real, viscous, fluids. It is named after its creator, William John Macquorn Rankine....

    ). It is only through dissipation of a vortex due to viscosity that a vortex line can end in the fluid, rather than at the boundary of the fluid. For example, the wingtip vortices
    Wingtip vortices
    Wingtip vortices are tubes of circulating air that are left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing. The cores of vortices spin at very high speed and are regions of very low pressure...

     from an airplane dissipate slowly and linger in the atmosphere long after the airplane has passed. This is a hazard to other aircraft and is known as wake turbulence
    Wake turbulence
    Wake turbulence is turbulence that forms behind an aircraft as it passes through the air. This turbulence includes various components, the most important of which are wing vorticies and jetwash. Jetwash refers simply to the rapidly moving gases expelled from a jet engine; it is extremely turbulent,...

    .

Dynamics

A vortex can be any circular or rotary flow. Perhaps unexpectedly, not all vortices possess
vorticity. Vorticity is a mathematical concept used in fluid dynamics
Fluid dynamics
In physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...

. It can be related to the amount of "circulation" or "rotation" in a fluid. In fluid dynamics, vorticity is the circulation per unit area at a point in the flow field. It is a vector quantity, whose direction is (roughly speaking) along the axis of the swirl. The vorticity of a free vortex is zero everywhere except at the center, whereas the vorticity of a forced vortex is non-zero. Vorticity is an approximately conserved quantity, meaning that it is not readily created or destroyed in a flow. Therefore, flows that start with minimal vorticity, such as water in a basin, create vortices with minimal vorticity, such as the characteristic swirling and approximately free vortex structure when it drains. By contrast, fluids that initially have vorticity, such as water in a rotating bowl, form vortices with vorticity, exhibited by the much less pronounced low pressure region at the center of this flow. Also in fluid dynamics, the movement of a fluid can be said to be vortical
Vortical
In fluid dynamics, vortical means pertaining to a vortex or to vortices. The movement of a fluid can be said to be vortical if the fluid moves around in a circle, or in a helix, or if it tends to spin around some axis....

if the fluid moves around in a circle, or in a helix, or if it tends to spin around some axis. Such motion can also be called solenoidal. In the atmospheric sciences, vorticity is a property that characterizes large-scale rotation of air masses. Since the atmospheric circulation is nearly horizontal, the (3 dimensional) vorticity is nearly vertical, and it is common to use the vertical component as a scalar vorticity. Mathematically, vorticity is defined as the curl of the fluid velocity :

Two types of vortex

In fluid mechanics, a distinction is often made between two limiting vortex cases. One is called the free (irrotational) vortex, and the other is the forced (rotational) vortex. These are considered below, using the following example:
Types of vortex illustrated by the movement of two autumn leaves
Reference position in a counter-clockwise vortex. In an irrotational vortex, the leaves preserve their original orientation while moving counter-clockwise. In a rotational vortex, the leaves rotate with the counter-clockwise flow.


Free (irrotational) vortex

When fluid is drawn down a plug-hole, one can observe the phenomenon of a free vortex or line vortex. The tangential velocity v varies inversely as the distance r from the center of rotation, so the angular momentum rv is uniform everywhere throughout the flow; the vorticity is zero everywhere (except for a singularity at the center-line) and the circulation about a contour containing r = 0 has the same value everywhere. The free surface
Free surface
In physics, a free surface is the surface of a fluid that is subject to constant perpendicular normal stress and zero parallel shear stress,such as the boundary between two homogenous fluids,for example liquid water and the air in the Earth's atmosphere...

 (if present) dips sharply (as r −2
Inverse-square law
In physics, an inverse-square law is any physical law stating that a specified physical quantity or strength is inversely proportional to the square of the distance from the source of that physical quantity....

 ) as the center line is approached.

The tangential velocity is given by:

where Γ is the circulation and r is the radial distance from the center of the vortex.

In non-technical terms, the fluid near the center of the vortex circulates faster than the fluid far from the center. The speed along the circular path of flow decreases as you move out from the center. At the same time the inner streamlines have a shorter distance to travel to complete a ring. If you were running a race on a circular track would you rather be on the inside or outside, assuming the goal was to complete a circle? Imagine a leaf floating in a free vortex. The leaf's tip points to the center and the blade straddles multiple streamlines. The outer flow is slow in terms of angle traversed and it exerts a backwards tug on the base of the leaf while the faster inner flow pulls the tip forwards. The drag force opposes rotation of the leaf as it moves around the circle.

Forced (rotational) vortex

In a forced vortex the fluid rotates as a solid body (there is no shear). The motion can be realized by placing a dish of fluid on a turntable rotating at ω radian/s; the fluid has vorticity of 2ω everywhere, and the free surface (if present) is a paraboloid.

The tangential velocity is given by:

where ω is the angular velocity
Angular velocity
In physics, the angular velocity is a vector quantity which specifies the angular speed of an object and the axis about which the object is rotating. The SI unit of angular velocity is radians per second, although it may be measured in other units such as degrees per second, revolutions per...

 and r is the radial distance from the center of the vortex.

Vortices in magnets

Different classes of vortex waves also exist in magnets. There are exact solutions to classical nonlinear magnetic equations e.g. Landau-Lifshitz equation, continuum Heisenberg model
Heisenberg model
The Heisenberg model can refer to two models in statistical mechanics:*Heisenberg model , a classical nearest neighbour spin model*Heisenberg model , a model where the spins are treated quantum mechanically using Pauli matrices....

, Ishimori equation
Ishimori equation
The Ishimori equation is a partial differential equation proposed by the Japanese mathematician . Its interest is as the first example of a nonlinear spin-one field model in the plane that is integrable .-Equation:The IE has the form...

, nonlinear Schrödinger equation
Nonlinear Schrödinger equation
In theoretical physics, the nonlinear Schrödinger equation is a nonlinear version of Schrödinger's equation. It is a classical field equation with applications to optics and water waves. Unlike the Schrödinger equation, it never describes the time evolution of a quantum state...

 and so on.

Observations

A vortex can be seen in the spiraling motion of air or liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...

 around a center of rotation
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...

. The circular current of water of conflicting tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

s often form vortex shapes. Turbulent flow
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...

 makes many vortices. A good example of a vortex is the atmospheric
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

 phenomenon of a whirlwind or a tornado
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...

 or dust devil
Dust devil
A dust devil is a strong, well-formed, and relatively long-lived whirlwind, ranging from small to large . The primary vertical motion is upward...

. This whirling air mass mostly takes the form of a helix
Helix
A helix is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helixes are coil springs and the handrails of spiral staircases. A "filled-in" helix – for...

, column
Column
A column or pillar in architecture and structural engineering is a vertical structural element that transmits, through compression, the weight of the structure above to other structural elements below. For the purpose of wind or earthquake engineering, columns may be designed to resist lateral forces...

, or spiral
Spiral
In mathematics, a spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.-Spiral or helix:...

. Tornadoes develop from severe thunderstorms, usually spawned from squall line
Squall line
A squall line is a line of severe thunderstorms that can form along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. It contains heavy precipitation, hail, frequent lightning, strong straight-line winds, and possibly tornadoes and waterspouts....

s and supercell thunderstorms, though they sometimes happen as a result of a hurricane.

In atmospheric physics, a mesovortex
Mesocyclone
A mesocyclone is a vortex of air, approximately 2 to 10 miles in diameter , within a convective storm....

is on the scale of a few miles (smaller than a hurricane but larger than a tornado). [2] On a much smaller scale, a vortex is usually formed as water goes down a drain, as in a sink
Sink
A sink is a bowl-shaped plumbing fixture used for washing hands, for dishwashing or other purposes. Sinks generally have taps that supply hot and cold water and may include a spray feature to be used for faster rinsing...

 or a toilet
Toilet
A toilet is a sanitation fixture used primarily for the disposal of human excrement, often found in a small room referred to as a toilet/bathroom/lavatory...

. This occurs in water as the revolving mass forms a whirlpool
Whirlpool
A whirlpool is a swirling body of water usually produced by ocean tides. The vast majority of whirlpools are not very powerful. More powerful ones are more properly termed maelstroms. Vortex is the proper term for any whirlpool that has a downdraft...

. This whirlpool is caused by water flowing out of a small opening in the bottom of a basin
Sink
A sink is a bowl-shaped plumbing fixture used for washing hands, for dishwashing or other purposes. Sinks generally have taps that supply hot and cold water and may include a spray feature to be used for faster rinsing...

 or reservoir. This swirling flow structure within a region of fluid flow opens downward from the water surface.

Instances

  • In the hydrodynamic interpretation of the behaviour of electromagnetic field
    Electromagnetic field
    An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...

    s, the acceleration of electric fluid in a particular direction creates a positive vortex of magnetic fluid. This in turn creates around itself a corresponding negative vortex of electric fluid.
  • Smoke ring
    Smoke ring
    A smoke ring is a visible vortex ring formed by sudden release of smoke. It can be created by blowing smoke from the mouth, quickly lighting a cigarette lighter and putting it out or holding a burning incense stick or a cigarette vertically, pushing it with the burning side up and suddenly pulling...

     : A ring of smoke that persists for a surprisingly long time, illustrating the slow rate at which viscosity dissipates the energy of a vortex.
  • Lift-induced drag
    Lift-induced drag
    In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is a drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or a lifting body redirecting air to cause lift and also in cars...

     of a wing
    Wing
    A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...

     on an aircraft
    Aircraft
    An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

    .
  • The primary cause of drag
    Drag (physics)
    In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

     in the sail
    Sail
    A sail is any type of surface intended to move a vessel, vehicle or rotor by being placed in a wind—in essence a propulsion wing. Sails are used in sailing.-History of sails:...

     of a sloop
    Sloop
    A sloop is a sail boat with a fore-and-aft rig and a single mast farther forward than the mast of a cutter....

    .
  • Whirlpool
    Whirlpool
    A whirlpool is a swirling body of water usually produced by ocean tides. The vast majority of whirlpools are not very powerful. More powerful ones are more properly termed maelstroms. Vortex is the proper term for any whirlpool that has a downdraft...

    : a swirling body of water produced by ocean tides or by a hole underneath the vortex where the water would drain out, such as a bathtub. A large, powerful whirlpool is known as a maelstrom
    Maelstrom
    A maelstrom is a very powerful whirlpool; a large, swirling body of water. A free vortex, it has considerable downdraft. The power of tidal whirlpools tends to be exaggerated by laymen. There are virtually no stories of large ships ever being sucked into a maelstrom, although smaller craft are in...

    . In popular imagination, but only rarely in reality, they can have the dangerous effect of destroying boats. Examples are Charybdis
    Charybdis
    Charybdis or Kharybdis was a sea monster, later rationalised as a whirlpool and considered a shipping hazard in the Strait of Messina.-The mythological background:...

     of classical mythology
    Mythology
    The term mythology can refer either to the study of myths, or to a body or collection of myths. As examples, comparative mythology is the study of connections between myths from different cultures, whereas Greek mythology is the body of myths from ancient Greece...

     in the Straits of Messina, Italy
    Italy
    Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

    ; the Naruto whirlpool
    Naruto whirlpool
    The are tidal whirlpools in the Naruto Strait, a channel between Naruto in Tokushima and Awaji Island in Hyōgo, Japan.The strait between Naruto and Awaji island has a width of about . The strait is one of the connections between the Pacific Ocean and the Inland Sea, a body of water separating...

    s of Nankaido
    Nankaido
    The , literally meaning "southern sea road," is a Japanese term denoting both an ancient division of the country and the main road running through it. The road connected provincial capitals in this region...

    , Japan
    Japan
    Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

    ; the Maelstrom
    Maelstrom
    A maelstrom is a very powerful whirlpool; a large, swirling body of water. A free vortex, it has considerable downdraft. The power of tidal whirlpools tends to be exaggerated by laymen. There are virtually no stories of large ships ever being sucked into a maelstrom, although smaller craft are in...

    , Lofoten
    Lofoten
    Lofoten is an archipelago and a traditional district in the county of Nordland, Norway. Though lying within the Arctic Circle, the archipelago experiences one of the world's largest elevated temperature anomalies relative to its high latitude.-Etymology:...

    , Norway
    Norway
    Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

    .
  • Tornado
    Tornado
    A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...

     : a violent windstorm characterized by a twisting, funnel-shaped cloud. A less violent version of a tornado, over water, is called a waterspout
    Waterspout
    A waterspout is an intense columnar vortex that occurs over a body of water and is connected to a cumuliform cloud. In the common form, it is a non-supercell tornado over water. While it is often weaker than most of its land counterparts, stronger versions spawned by mesocyclones do occur...

    .
  • Hurricane
    Tropical cyclone
    A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

     : a much larger, swirling body of clouds produced by evaporating warm ocean water and influenced by the Earth's rotation. Similar, but far greater, vortices are also seen on other planets, such as the permanent Great Red Spot on Jupiter
    Jupiter
    Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

     and the intermittent Great Dark Spot
    Great Dark Spot
    The Great Dark Spot is the name given to a series of dark spots on Neptune similar in appearance to Jupiter's Great Red Spot. The first one was observed in 1989 by NASA's Voyager 2 probe. Like Jupiter's spot, they are anticyclonic storms...

     on Neptune
    Neptune
    Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...

    .
  • Polar vortex
    Polar vortex
    A polar vortex is a persistent, large-scale cyclone located near one or both of a planet's geographical poles. On Earth, the polar vortices are located in the middle and upper troposphere and the stratosphere...

     : a persistent, large-scale cyclone centered near the Earth's poles, in the middle and upper troposphere and the stratosphere.
  • Sunspot
    Sunspot
    Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature....

     : dark region on the Sun's surface (photosphere) marked by a lower temperature than its surroundings, and intense magnetic activity.
  • The accretion disk of a black hole
    Black hole
    A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...

     or other massive gravitational source.
  • Spiral galaxy
    Spiral galaxy
    A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as...

     : a type of galaxy in the Hubble sequence
    Hubble sequence
    The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926. It is often known colloquially as the Hubble tuning-fork diagram because of the shape in which it is traditionally represented....

     that is characterized by a thin, rotating disk. Earth's galaxy, the Milky Way
    Milky Way
    The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

    , is of this type.

External links

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