Journal article
First Report of Electron Measurements During a Europa Footprint Tail Crossing by Juno
Geophysical research letters, Vol.47(18), e2020GL089732
09/28/2020
DOI: 10.1029/2020GL089732
Abstract
We report the first in situ observations of electron measurements at a Europa footprint tail (FPT) crossing in the auroral region. During its 12th science perijove pass, Juno crossed magnetic field lines connected to Europa's FPT. We find that electrons in the range ~0.4 to ~25 keV, with a characteristic energy of 3.6 ± 0.5 keV, precipitate into Jupiter's atmosphere to create the footprint aurora. The energy flux peaks at ~36 mW/m2, while the peak ultraviolet (UV) brightness is estimated at 37 kR. We estimate the peak electron density and temperature to be 17.3 cm−3 and 1.8 ± 0.1 keV, respectively. Using magnetic flux shell mapping, we estimate that the radial width of the interaction at Europa's orbit spans roughly 3.6 ± 1.0 Europa radii. In contrast to typical Io FPT crossings, the instrument background caused by penetrating energetic radiation (> ~5–10 MeV electrons) increased during the Europa FPT crossing.
Plain Language Summary
Jupiter's moons interact with Jupiter's space environment, or magnetosphere, and create auroral spots and tails in Jupiter's ionosphere. Io's aurora footprint on Jupiter is the strongest and most persistent of all moons, but Ganymede, Callisto, and Europa's auroral footprints are also routinely observed by remote platforms. NASA's Juno mission and its instrument suite occasionally fly through regions that are connected to the moon‐magnetosphere interactions. During these crossings, Juno samples the electrons and ions that create the aurora. This paper is the first report of electron measurements taken during a Juno crossing of Europa's tail. These measurements confirm previous results based on remote observations. Most importantly, they provide a sample of the conditions in the regions associated with Europa's footprint aurora in Jupiter's magnetosphere.
Key Points
This is the first report of in situ electron measurements of a Europa footprint tail crossing
Precipitating electron energies range from ~0.4 to ~25 keV with a characteristic energy of 3.6 keV, consistent with a low color ratio of the auroral emissions
The instrument background caused by > ~5–10 MeV penetrating electrons increased during the crossing, opposite to what is observed at Io
Details
- Title: Subtitle
- First Report of Electron Measurements During a Europa Footprint Tail Crossing by Juno
- Creators
- F. Allegrini - Southwest Research InstituteG. R. Gladstone - Southwest Research InstituteV. Hue - Southwest Research InstituteG. Clark - Johns Hopkins University Applied Physics LaboratoryJ. R. Szalay - Princeton UniversityW. S. Kurth - University of IowaF. Bagenal - Laboratory for Atmospheric and Space PhysicsS. Bolton - Southwest Research InstituteJ. E. P. Connerney - Goddard Space Flight CenterR. W. Ebert - Southwest Research InstituteT. K. Greathouse - Southwest Research InstituteG. B. Hospodarsky - University of IowaM. Imai - University of IowaP. Louarn - Institut de Recherche en Astrophysique et PlanétologieB. H. Mauk - Johns Hopkins University Applied Physics LaboratoryD. J. McComas - Princeton UniversityJ. Saur - University of CologneA. H. Sulaiman - University of IowaP. W. Valek - Southwest Research InstituteR. J. Wilson - Laboratory for Atmospheric and Space Physics
- Resource Type
- Journal article
- Publication Details
- Geophysical research letters, Vol.47(18), e2020GL089732
- DOI
- 10.1029/2020GL089732
- ISSN
- 0094-8276
- eISSN
- 1944-8007
- Number of pages
- 10
- Grant note
- NASA New Frontiers Program (NNM06AA75C; 699050X; 699041X) National Aeronautics and Space Administration (NASA) (New Frontiers Program)
- Language
- English
- Date published
- 09/28/2020
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984455363902771
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