title: Discovery of diffuse aurora on Mars.
abstract: Planetary auroras reveal the complex interplay between an atmosphere and the surrounding plasma environment. We report the discovery of low-altitude, diffuse auroras spanning much of Mars' northern hemisphere, coincident with a solar energetic particle outburst. The Imaging Ultraviolet Spectrograph, a remote sensing instrument on the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, detected auroral emission in virtually all nightside observations for ~5 days, spanning nearly all geographic longitudes. Emission extended down to ~60 kilometer (km) altitude (1 microbar), deeper than confirmed at any other planet. Solar energetic particles were observed up to 200 kilo--electron volts; these particles are capable of penetrating down to the 60 km altitude. Given minimal magnetic fields over most of the planet, Mars is likely to exhibit auroras more globally than Earth.
authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA. nick.schneider@lasp.colorado.edu.
authors.forename: N M
authors.initials: NM
authors.lastname: Schneider
authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
authors.forename: J I
authors.initials: JI
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authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
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authors.initials: SK
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authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
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authors.initials: A
authors.lastname: Stiepen
authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
authors.forename: A I F
authors.initials: AI
authors.lastname: Stewart
authors.affiliation: Space Sciences Lab, University of California, Berkeley, Berkeley, CA 94720, USA.
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authors.lastname: Larson
authors.affiliation: Space Sciences Lab, University of California, Berkeley, Berkeley, CA 94720, USA.
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authors.affiliation: Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS, Toulouse, France. University Paul Sabatier, IRAP, CNRS, Toulouse, France.
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authors.lastname: Mazelle
authors.affiliation: Space Sciences Lab, University of California, Berkeley, Berkeley, CA 94720, USA.
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authors.initials: CO
authors.lastname: Lee
authors.affiliation: Space Sciences Lab, University of California, Berkeley, Berkeley, CA 94720, USA.
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authors.initials: RJ
authors.lastname: Lillis
authors.affiliation: Computational Physics, Inc, Springfield, VA 22151, USA.
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authors.initials: JS
authors.lastname: Evans
authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
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authors.initials: D
authors.lastname: Brain
authors.affiliation: Space Science Division, Naval Research Laboratory, Washington, DC 20375, USA.
authors.forename: M H
authors.initials: MH
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authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
authors.forename: W E
authors.initials: WE
authors.lastname: McClintock
authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Chaffin
authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
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authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
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authors.initials: GM
authors.lastname: Holsclaw
authors.affiliation: Laboratoire Atmosphères, Milieux, Observations Spatiales, Institut Pierre Simon Laplace, Guyancourt, France.
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authors.initials: F
authors.lastname: Lefevre
authors.affiliation: Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: D Y
authors.initials: DY
authors.lastname: Lo
authors.affiliation: Center for Space Physics, Boston University, Boston, MA 02215, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Clarke
authors.affiliation: Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: F
authors.initials: F
authors.lastname: Montmessin
authors.affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Boulder, CO 80303, USA.
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authors.initials: BM
authors.lastname: Jakosky