• Jupiter's Auroras Present a Powerful Mystery

    From baalke@earthlink.net@21:1/5 to All on Thu Sep 7 23:53:27 2017
    https://www.jpl.nasa.gov/news/news.php?feature=6940

    Jupiter's Auroras Present a Powerful Mystery
    Jet Propulsion Laboratory
    September 6, 2017

    Scientists on NASA's Juno mission have observed massive amounts of energy swirling over Jupiter's polar regions that contribute to the giant planet's powerful auroras - only not in ways the researchers expected.

    Examining data collected by the ultraviolet spectrograph and energetic-particle detector instruments aboard the Jupiter-orbiting Juno spacecraft, a team
    led by Barry Mauk of the Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, observed signatures of powerful electric potentials,
    aligned with Jupiter's magnetic field, that accelerate electrons toward
    the Jovian atmosphere at energies up to 400,000 electron volts. This is
    10 to 30 times higher than the largest auroral potentials observed at
    Earth, where only several thousands of volts are typically needed to generate the most intense auroras -- known as discrete auroras -- the dazzling, twisting, snake-like northern and southern lights seen in places like
    Alaska and Canada, northern Europe, and many other northern and southern
    polar regions.

    Jupiter has the most powerful auroras in the solar system, so the team
    was not surprised that electric potentials play a role in their generation. What's puzzling the researchers, Mauk said, is that despite the magnitudes
    of these potentials at Jupiter, they are observed only sometimes and are
    not the source of the most intense auroras, as they are at Earth.

    "At Jupiter, the brightest auroras are caused by some kind of turbulent acceleration process that we do not understand very well," said Mauk,
    who leads the investigation team for the APL-built Jupiter Energetic Particle Detector Instrument (JEDI). "There are hints in our latest data indicating
    that as the power density of the auroral generation becomes stronger and stronger, the process becomes unstable and a new acceleration process
    takes over. But we'll have to keep looking at the data."

    Scientists consider Jupiter to be a physics lab of sorts for worlds beyond
    our solar system, saying the ability of Jupiter to accelerate charged
    particles to immense energies has implications for how more distant astrophysical
    systems accelerate particles. But what they learn about the forces driving Jupiter's auroras and shaping its space weather environment also has practical implications in our own planetary backyard.

    "The highest energies that we are observing within Jupiter's auroral regions are formidable. These energetic particles that create the auroras are
    part of the story in understanding Jupiter's radiation belts, which pose
    such a challenge to Juno and to upcoming spacecraft missions to Jupiter
    under development," said Mauk. "Engineering around the debilitating effects
    of radiation has always been a challenge to spacecraft engineers for missions at Earth and elsewhere in the solar system. What we learn here, and from spacecraft like NASA's Van Allen Probes and Magnetospheric Multiscale
    mission (MMS) that are exploring Earth's magnetosphere, will teach us
    a lot about space weather and protecting spacecraft and astronauts in
    harsh space environments. Comparing the processes at Jupiter and Earth
    is incredibly valuable in testing our ideas of how planetary physics works."

    Mauk and colleagues present their findings in the Sept. 7 issue of the
    journal Nature.

    NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest
    Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate. Lockheed Martin Space
    Systems, Denver, built the spacecraft.

    https://www.nasa.gov/juno

    https://www.missionjuno.swri.edu

    The public can follow the mission on Facebook and Twitter at:

    https://www.facebook.com/NASAJuno

    https://www.twitter.com/NASAJuno

    More information on Jupiter can be found at:

    https://www.nasa.gov/jupiter

    News Media Contact
    DC Agle
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-393-9011 / 818-354-6278
    agle@jpl.nasa.gov

    Michael Buckley
    Johns Hopkins University Applied Physics Laboratory
    443-778-7536
    Michael.Buckley@jhuapl.edu

    Dwayne Brown / Laurie Cantillo
    NASA Headquarters, Washington
    202-358-1726 / 202-358-1077
    dwayne.c.brown@nasa.gov / laura.l.cantillo@nasa.gov

    2017-236

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)