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Aurora on Jupiter

12 July 2021

The media made a meal once again from a new piece of research from University College, London. The claim is that scientists have solved a 40 year mystery of Jupiter's X-ray auroral phenomena. The research is published in Science Advances – see https://advances.sciencemag.org/content/7/28/eabf0851 … see also https://phys.org/news/2021-07-scientists-year-mystery-jupiter-x-ray.html ….the nuts and bolts for it come direct from NASAs Juno Mission and NASAs Chandra X-ray Observatory. Jupiter, it seems, produces a spectacular burst of X-rays every four minutes. These are invisible to the naked eye, even with a telescope, It was not until 40 years ago there were telescopes capable of picking up X-rays. In other words, they were out there all the time but never picked up by astronomers until the technology allowed it. That solves one of the mysteries in the headlines. The bigger mystery is what causes the auroras on Jupiter, which are really quite intense. One reason seems to be that Jupiter has a very powerful magnetic shield. This, in turn, means that it creates a more powerful zone of ionisation below the magnetic shield.

Jupiter's X-ray bursts give way to auroral phenomena – bursts of visible and invisible light that occur when charged particles interact with the planet's atmosphere, in the ionosphere. A similar thing occurs on Earth – creating the northern and southern lights. Jupiter's version is much more powerful, releasing hundreds of gigawatts of energy. The research also made use of ESAs XMM Newton Observatory [which is on an earth orbit]. It involved University College London and the Chinese Academy of Sciences. They discovered X-ray flares were triggered by periodic vibrations of Jupiter's magnetic 'field lines' – an electro-magnetic current perhaps. These vibrations create waves of plasma [ionised gas] that cause ionised particles to go surfing – along the magnetic field lines. This releases energy in the form of X-rays. As lightning also releases X-rays they may be standing on the cusp of a big discovery.

The charged particles originate, it is believed, from 'volcanic gas' passing into space from giant volcanoes on Io, a moon of Jupiter. This gas becomes ionised, we are told, or stripped free of electrons. It goes on to form a doughnut of plasma encircling the planet. How much of this is guesswork is difficult to assess for the time being but on earth auroral phenomena are caused by the solar wind. It is assumed that the solar wind is not very powerful once it reaches as far out as Jupiter, and in any case, the magnetic shield is too powerful for the solar wind to breach – many orders of magnitude greater than earth's magnetic shield. Volcanism on Io is now seen as the culprit. An explanation was required in order to make publication worthwhile. However, it is hoped a closer look at planets further out in the solar system may clarify and provide substantiation for the explanation. This will take some time of course but Saturn looks promising – as well as Neptune and Uranus. An expert is quoted, not directly involved in the research, who claims X-rays are typically produced by extremely powerful and violent phenomena such as black holes and neutron stars. Are they? Is mainstream holding on to the apron of nanny – loathe to let it go.

Over at https://phys.org/news/2021-07-cosmic-x-ray-emitters-perspective.html … which is quite a clever piece of research – see https://www.nasa.gov/mission_pages/nustar/main/index.html … and www.nustar.caltech.edu/ … which concerns the X-rays beamed down from black holes and neutron stars. When such a beam points straight at a telescope it is very bright but if the telescope lens capture it at an angle, or side on, the beam is much dimmer. NASAs NuSTAR 'space observatory' holds true for even the most prominent X-ray emitters – black holes or otherwise.

Meanwhile, at www.sciencedaily.com/releases/2020/08/200805124058.htm … we have an oldie, from last year. Ammonia rich hail sheds light on Jupiter's weather. Ammonia is abundant near Jupiter's equatorial regions but depleted at other latitudes.

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