Editing Great Red Spot (section)

==Mechanical dynamics==
[[File:790106-0203 Voyager 58M to 31M reduced.gif|thumb|upright=1.25|Time-lapse sequence from the approach of ''Voyager 1'' to Jupiter in 1979, showing the motion of atmospheric bands, and the circulation of the Great Red Spot. The momentary black spots are shadows cast by [[Moons of Jupiter|Jupiter's moons]].]]
Jupiter's Great Red Spot rotates counterclockwise, with a period of about 4.5 Earth days,<ref>{{cite journal |last1=Rogers |first1=John |title=The accelerating circulation of Jupiter's Great Red Spot |journal=Journal of the British Astronomical Association |date=2008 |volume=118 |issue=1 |pages=14–20 |bibcode=2008JBAA..118...14R |url=https://ui.adsabs.harvard.edu/abs/2008JBAA..118...14R/abstract |access-date=2022-08-28}}</ref> or 11 Jovian days, as of 2008. Measuring {{convert|16350|km|mi|abbr=on}} in width as of 3 April 2017, the Great Red Spot is 1.3 times the diameter of Earth.<ref name="junospots">{{Cite news|url=http://www.nasa.gov/feature/jpl/nasa-s-juno-spacecraft-spots-jupiter-s-great-red-spot|title=NASA's Juno Spacecraft Spots Jupiter's Great Red Spot|last=Perez|first=Martin|date=2017-07-12|work=NASA|access-date=2017-07-16|language=en|archive-date=2017-07-15|archive-url=https://web.archive.org/web/20170715181311/https://www.nasa.gov/feature/jpl/nasa-s-juno-spacecraft-spots-jupiter-s-great-red-spot/|url-status=dead}}</ref> The cloud-tops of this storm are about {{convert|8|km|mi|0|abbr=on}} above the surrounding cloud-tops.<ref>{{cite book |url=https://books.google.com/books?id=KuBYXLt4K9MC&pg=PA5 |title=The Voyager Mission: Jupiter, the Giant of the Solar System |date=1979 |publisher=NASA |page=5}}</ref> The storm has continued for centuries because there is no planetary surface (only a mantle of [[hydrogen]]) to cause friction; circulating atmospheric eddies persist because there is nothing to oppose their angular momentum.<ref>{{cite web |date=November 24, 2004 |title=Jupiter's Atmosphere and Great Red Spot |url=http://www.astrophysicsspectator.com/topics/planets/JupiterGreatRedSpot.html |publisher=www.astrophysicsspectator.com}}</ref>

[[Infrared]] data has long indicated that the Great Red Spot is colder (and thus higher in altitude) than most of the other clouds on the planet.{{sfnp|Rogers|1995|p=191}} The upper atmosphere above the storm, however, has substantially higher temperatures than the rest of the planet.{{cn|date=March 2025}} [[Acoustic wave|Acoustic waves]] rising from the turbulence of the storm below have been proposed as an explanation for the heating of this region.<ref name="Heating of Jupiter's upper atmosphere">{{cite journal |last1=O'Donoghue |first1=J. |last2=Moore |first2=L. |last3=Stallard |first3=T. S. |last4=Melin |first4=H. |title=Heating of Jupiter's upper atmosphere above the Great Red Spot |journal=Nature |date=27 July 2016 |volume=536 |issue=7615 |pages=190–192 |doi=10.1038/nature18940|pmid=27462811 |bibcode=2016Natur.536..190O |hdl=2381/38554 |s2cid=4462322 |url=https://figshare.com/articles/journal_contribution/10122821 |hdl-access=free }}</ref> The acoustic waves travel vertically up to a height of {{cvt|800|km}} above the storm where they break in the upper atmosphere, converting wave energy into heat. This creates a region of upper atmosphere that is {{convert|1600|K}}—several hundred kelvins warmer than the rest of the planet at this altitude.<ref name="Heating of Jupiter's upper atmosphere" /> The effect is described as like "crashing [...] ocean waves on a beach".<ref>{{cite web |date=27 July 2016 |title=Jupiter's Great Red Spot Likely a Massive Heat Source |url=https://www.nasa.gov/feature/jupiter-s-great-red-spot-likely-a-massive-heat-source |access-date=23 December 2018 |website=[[NASA]] |archive-date=12 June 2019 |archive-url=https://web.archive.org/web/20190612134857/https://www.nasa.gov/feature/jupiter-s-great-red-spot-likely-a-massive-heat-source/ |url-status=dead }}</ref>

[[File:Jupiter, Earth size comparison.jpg|left|thumb|upright=1.2|Size of the Earth compared to the Great Red Spot]]
Careful tracking of atmospheric features revealed the Great Red Spot's counterclockwise circulation as far back as 1966, observations dramatically confirmed by the first time-lapse movies from the ''Voyager'' fly-bys.{{sfnp|Rogers|1995|pp=194–196}} The spot is confined by a modest eastward [[jet stream]] to its south and a very strong westward one to its north.{{sfnp|Beebe|1997|p=35}} Though winds around the edge of the spot peak at about {{convert|432|km/h|mph|abbr=on}}, currents inside it seem stagnant, with little inflow or outflow.{{sfnp|Rogers|1995|p=195}} The rotation of the spot has slowed with time, perhaps as a direct result of its steady reduction in size.<ref>{{cite web |last=Rogers |first=John |url=http://www.britastro.org/jupiter/2006report09.htm |title=Interim reports on STB (Oval BA passing GRS), STropB, GRS (internal rotation measured), EZ(S. Eq. Disturbance; dramatic darkening; NEB interactions), & NNTB |publisher=[[British Astronomical Association]] |access-date=2007-06-15 }}</ref>

The Great Red Spot's [[latitude]] has been stable for the duration of good observational records, typically varying by about a degree. Its [[longitude]], however, is subject to constant variation, including a 90-day longitudinal oscillation with an amplitude of ~1°.<ref>{{cite journal|author1=Reese, Elmer J.|author2=Solberg, H. Gordon|year=1966|title=Recent measures of the latitude and longitude of Jupiter's red spot|journal=Icarus|volume=5|issue=1–6|pages=266–273|bibcode=1966Icar....5..266R|doi=10.1016/0019-1035(66)90036-4|hdl-access=free|hdl=2060/19650022425}}<!--|access-date=2007-06-20 --></ref>{{sfnp|Rogers|1995|pp=192–193}}<ref>{{Cite journal |last1=Trigo-Rodriguez |first1=J.M |last2=Sánchez-Lavega |first2=A |last3=Gómez |first3=J.M |last4=Lecacheux |first4=J |last5=Colas |first5=F |last6=Miyazaki |first6=I |date=2000 |title=The 90-day oscillations of Jupiter's Great Red Spot revisited |url=https://linkinghub.elsevier.com/retrieve/pii/S0032063300000027 |journal=Planetary and Space Science |language=en |volume=48 |issue=4 |pages=331–339 |doi=10.1016/S0032-0633(00)00002-7|bibcode=2000P&SS...48..331T |s2cid=120883365 }}</ref> Because Jupiter's gaseous body does not rotate uniformly at all latitudes, astronomers have defined three different systems for defining longitude. System II is used for latitudes of more than 10 degrees and was originally based on the average rotational period of the Great Red Spot ({{nowrap|9 h 55 min 42 s}}).<ref>{{cite journal |last=Stone |first=Peter H. |title=On Jupiter's Rate of Rotation |journal=Journal of the Atmospheric Sciences |year=1974 |volume=31 |issue=5 |pages=1471–1472 |url=http://ams.allenpress.com/archive/1520-0469/31/5/pdf/i1520-0469-31-5-1471.pdf |access-date=2007-06-20 |doi=10.1175/1520-0469(1974)031<1471:OJROR>2.0.CO;2 |bibcode=1974JAtS...31.1471S}}</ref>{{sfnp|Rogers|1995|pp=48, 193}} Despite this, however, the spot has "lapped" the planet in System II at least 10 times since the early 19th century.{{cn|date=March 2025}} Its drift rate has changed dramatically over the years and has been linked to the brightness of the [[South Equatorial Belt]] and the presence or absence of a South Tropical Disturbance.{{sfnp|Rogers|1995|p=193}}