• Scientists solve 40-year mystery over Ju

    From ScienceDaily@1:317/3 to All on Fri Jul 9 21:30:38 2021
    Scientists solve 40-year mystery over Jupiter's X-ray aurora

    Date:
    July 9, 2021
    Source:
    University College London
    Summary:
    Researchers combined close-up observations of Jupiter's environment
    by NASA's satellite Juno, which is currently orbiting the
    planet, with simultaneous X-ray measurements from the European
    Space Agency's XMM- Newton observatory (which is in Earth's own
    orbit). The X-rays are part of Jupiter's aurora -- bursts of visible
    and invisible light that occur when charged particles interact
    with the planet's atmosphere. A similar phenomenon occurs on Earth,
    creating the northern lights, but Jupiter's is much more powerful,
    releasing hundreds of gigawatts of energy, enough to briefly power
    all of human civilization.



    FULL STORY ==========================================================================
    A research team co-led by UCL (University College London) has solved a
    decades- old mystery as to how Jupiter produces a spectacular burst of
    X-rays every few minutes.


    ==========================================================================
    The X-rays are part of Jupiter's aurora -- bursts of visible and
    invisible light that occur when charged particles interact with the
    planet's atmosphere.

    A similar phenomenon occurs on Earth, creating the northern lights,
    but Jupiter's is much more powerful, releasing hundreds of gigawatts of
    energy, enough to briefly power all of human civilisation*.

    In a new study, published in Science Advances, researchers combined
    close-up observations of Jupiter's environment by NASA's satellite
    Juno, which is currently orbiting the planet, with simultaneous X-ray measurements from the European Space Agency's XMM-Newton observatory
    (which is in Earth's own orbit).

    The research team, led by UCL and the Chinese Academy of Sciences,
    discovered that X-ray flares were triggered by periodic vibrations of
    Jupiter's magnetic field lines. These vibrations create waves of plasma (ionised gas) that send heavy ion particles "surfing" along magnetic
    field lines until they smash into the planet's atmosphere, releasing
    energy in the form of X-rays.

    Co-lead author Dr William Dunn (UCL Mullard Space Science Laboratory)
    said: "We have seen Jupiter producing X-ray aurora for four decades,
    but we didn't know how this happened. We only knew they were produced
    when ions crashed into the planet's atmosphere.

    "Now we know these ions are transported by plasma waves -- an explanation
    that has not been proposed before, even though a similar process produces Earth's own aurora. It could, therefore, be a universal phenomenon,
    present across many different environments in space." X-ray auroras occur
    at Jupiter's north and south poles, often with clockwork regularity --
    during this observation Jupiter was producing bursts of X-rays every
    27 minutes.



    ==========================================================================
    The charged ion particles that hit the atmosphere originate from volcanic
    gas pouring into space from giant volcanoes on Jupiter's moon, Io.

    This gas becomes ionised (its atoms are stripped free of electrons)
    due to collisions in Jupiter's immediate environment, forming a donut
    of plasma that encircles the planet.

    Co-lead author Dr Zhonghua Yao (Chinese Academy of Sciences, Beijing)
    said: "Now we have identified this fundamental process, there is a wealth
    of possibilities for where it could be studied next. Similar processes
    likely occur around Saturn, Uranus, Neptune and probably exoplanets as
    well, with different kinds of charged particles 'surfing' the waves."
    Co-author Professor Graziella Branduardi-Raymont (UCL Mullard Space
    Science Laboratory) said: "X-rays are typically produced by extremely
    powerful and violent phenomena such as black holes and neutron stars,
    so it seems strange that mere planets produce them too.

    "We can never visit black holes, as they are beyond space travel, but
    Jupiter is on our doorstep. With the arrival of the satellite Juno
    into Jupiter's orbit, astronomers now have a fantastic opportunity
    to study an environment that produces X-rays up close." For the new
    study, researchers analysed observations of Jupiter and its surrounding environment carried out continuously over a 26-hour period by the Juno
    and XMM-Newton satellites.



    ==========================================================================
    They found a clear correlation between waves in the plasma detected by
    Juno and X-ray auroral flares at Jupiter's north pole recorded by X-MM
    Newton. They then used computer modelling to confirm that the waves
    would drive the heavy particles towards Jupiter's atmosphere.

    Why the magnetic field lines vibrate periodically is unclear, but the
    vibration may result from interactions with the solar wind or from
    high-speed plasma flows within Jupiter's magnetosphere.

    Jupiter's magnetic field is extremely strong -- about 20,000 times as
    strong as Earth's -- and therefore its magnetosphere, the area controlled
    by this magnetic field, is extremely large. If it was visible in the
    night sky, it would cover a region several times the size of our moon.

    The work was supported by the Chinese Academy of Sciences, the National
    Natural Science Foundation of China, and the UK's Science and Technology Facilities Council (STFC), Royal Society, and Natural Environment Research Council, as well as ESA and NASA.

    * Jupiter's X-ray aurora alone releases about a gigawatt, equivalent to
    what one power station might produce over a period of days.

    ========================================================================== Story Source: Materials provided by University_College_London. Note:
    Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Zhonghua Yao, William R. Dunn, Emma E. Woodfield, George Clark,
    Barry H.

    Mauk, Robert W. Ebert, Denis Grodent, Bertrand Bonfond, Dongxiao
    Pan, I.

    Jonathan Rae, Binbin Ni, Ruilong Guo, Graziella Branduardi-Raymont,
    Affelia D. Wibisono, Pedro Rodriguez, Stavros Kotsiaros, Jan-Uwe
    Ness, Frederic Allegrini, William S. Kurth, G. Randall Gladstone,
    Ralph Kraft, Ali H. Sulaiman, Harry Manners, Ravindra T. Desai,
    Scott J. Bolton.

    Revealing the source of Jupiter's x-ray auroral flares. Science
    Advances, 2021; 7 (28): eabf0851 DOI: 10.1126/sciadv.abf0851 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2021/07/210709193609.htm

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