📰 Winds in Jupiter’s atmosphere


The winds that blow at the level of Jupiter’s cloud layer are measured by the movement of the clouds. The most intense can reach speeds of 150 m / s. The mission Juice and his camera Janus will measure the winds in the cloud layer with an accuracy of about 1 m / s during the 67 passes near Jupiter to study the atmospheric circulation (Atmospheric circulation is the planetary-scale movement of …). These observations will be used to validate climate models.

The polar auroras on Jupiter photographed by the Hubble Space Telescope from NASA (The National Aeronautics and Space Administration (“National Administration of …) in 2016.
© NASA, ESA and J. Nichols (University of Leicester)

Above the clouds is the stratosphere (The stratosphere is the second layer of the earth’s atmosphere, which lies above the …) of Jupiter. What regime wind (Wind is the movement of an atmosphere, a mass of gas on the surface …) we meet? Answering this question is not easy due to the absence of visible tracers, such as clouds, to measure winds. Until recently, only measurements of the temperature (Temperature is a physical quantity measured using a thermometer and …) depend on latitude (Latitude is an angular value, an expression of the north-south positioning of a point on Earth …) he was born inaltitude (Altitude is the vertical elevation of a place or object relative to a level …) could be used to deduce east-west winds by applying the thermal wind relationship.

However, this technique has several limitations, including in particular the impossibility of deducing the winds at the equator. However, knowledge of the temperature and wind fields is essential to understand the traffic (Road traffic (Anglicism: road traffic) is the movement of motor vehicles …) atmospheric and the climate (Climate is the statistical distribution of atmospheric conditions in a …) in the stratosphere. Furthermore, the equatorial region is one of the most interesting regions of the stratosphere because the temperature fluctuates around (Autour is the name that gives the avian nomenclature in French (update) …) a value of mean (The mean is a statistical measure that characterizes the elements of a set of …)both depending on the time (Time is a concept developed by humans to learn the …) and elevation. This swing (A swing is a periodic movement or fluctuation. Swings are a …) it has a period of about four years and is called the “nearly four-year swing” (QQO). Such equatorial oscillations are observed in other planets including Saturn and the Land (Earth is the third planet in the Solar System in order of distance …). The QQO suggests that winds swing between easterly winds and easterly winds.west (West is a cardinal point, opposite to east. This is the direction towards …) with this same period of about four years.

Observatories such as ALMA (Atacama large millimeter / submillimeter array) now allow measuring Jupiter’s stratospheric winds at any latitude across theobservation (Observation is the action of a careful following of phenomena, without the will to see them …) molecular emissions at very high spatial and spectral resolutions. The velocities are deduced from the Doppler shifts induced by the winds on the spectral lines. However, ALMA measurements are rare (only one since its commissioning in 2011) and therefore insufficient to study the QQO and build the large surveys needed to understand the Jovian climate. the Instrument for submillimeter waves from Juice will produce stratospheric wind maps during each of its 67 orbits.

Finally, Jupiter is the planet (A planet is a celestial body orbiting the Sun or another star in …) where the most intense auroras of the Solar system (The solar system is a planetary system consisting of a star, the …). These auroras are produced several hundred kilometres (The meter (symbol m, from the Greek metron, measure) is the basic unit of the length of the System …) above the clouds, inionosphere (The ionosphere is a region of the atmosphere located between the mesosphere and the …). It is in these places that the strongest winds of theThe atmosphere of Jupiter (The atmosphere of Jupiter is the most important of the atmospheres of the planets …) have been detected. They are found on the main ovals of the aurora (i.e. their edges) and blow at about 2 km / s. ALMA detected similar winds in Jupiter’s stratosphere, with speeds of 400 m / s. One of the goals of Juice it will be unclear whether these winds and the ionospheric winds have a common origin.

Thibault Cavalie, researcher (A researcher (female researcher) refers to a person whose job is to do research …) CNRS (The National Center for Scientific Research, better known by the acronym CNRS, is the largest …) in the laboratory ofastrophysics (Astrophysics (from the Greek astro = star and physiqui = physics) is a branch …) of Bordeaux (LAB) / OASU.

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