Scientists connect the dots between Galilean moon, auroral emissions on Jupiter
Juno spacecraft discovered clues about mysterious processes creating the
dance of the auroral footprints

Date:
April 5, 2022
Source:
Southwest Research Institute
Summary:
On November 8, 2020, NASA's Juno spacecraft flew through an intense
beam of electrons traveling from Ganymede, Jupiter's largest moon,
to its auroral footprint on the gas giant. Scientists used data
from Juno's payload to study the particle population traveling
along the magnetic field line connecting Ganymede to Jupiter while,
at the same time, remotely sensing the associated auroral emissions
to unveil the mysterious processes creating the shimmering lights.



FULL STORY ==========================================================================
On November 8, 2020, NASA's Juno spacecraft flew through an intense
beam of electrons traveling from Ganymede, Jupiter's largest moon,
to its auroral footprint on the gas giant. Southwest Research Institute scientists used data from Juno's payload to study the particle population traveling along the magnetic field line connecting Ganymede to Jupiter
while, at the same time, remotely sensing the associated auroral emissions
to unveil the mysterious processes creating the shimmering lights.


========================================================================== "Jupiter's most massive moons each create their own auroras on Jupiter's
north and south poles," said Dr. Vincent Hue, lead author of a paper
outlining the results of this research. "Each auroral footprint, as we
call them, is magnetically connected to their respective moon, kind of
like a magnetic leash connected to the moon glowing on Jupiter itself."
Like the Earth, Jupiter experiences auroral light around the polar regions
as particles from its massive magnetosphere interact with molecules in
the Jovian atmosphere. However, Jupiter's auroras are significantly
more intense than Earth's, and unlike Earth, Jupiter's largest moons
also create auroral spots.

The Juno mission, led by SwRI's Dr. Scott Bolton, is circling Jupiter in
a polar orbit and flew through the electron "thread" connecting Ganymede
with its associated auroral footprint.

"Prior to Juno, we knew that these emissions can be quite complex, ranging
from a single auroral spot to multiple spots, which sometimes trail
an auroral curtain that we called the footprint tail," said Dr. Jamey
Szalay, a co-author from Princeton University. "Juno, flying extremely
close to Jupiter, revealed these auroral spots to be even more complex
than previously thought." Ganymede is the only moon in our solar system
that has its own magnetic field.

Its mini-magnetosphere interacts with Jupiter's massive magnetosphere,
creating waves that accelerate electrons along the gas giant's magnetic
field lines, which can be directly measured by Juno.

Two SwRI-led instruments on Juno, the Jovian Auroral Distributions
Experiment (JADE) and the Ultraviolet Spectrometer (UVS) provided key
data for this study, which was also supported by Juno's magnetic field
sensor built at NASA's Goddard Space Flight Center.

"JADE measured the electrons traveling along the magnetic field lines,
while UVS imaged the related auroral footprint spot," said SwRI's
Dr. Thomas Greathouse, a co-author on this study.

In this way, Juno is both able to measure the electron "rain" and
immediately observe the UV light it creates when it crashes into
Jupiter. Previous Juno measurements showed that large magnetic
perturbations accompanied the electron beams causing the auroral
footprint. However, this time, Juno did not observe similar perturbations
with the electron beam.

"If our interpretation is correct, this a confirmation of a decade-old
theory that we put together to explain the morphology of the auroral footprints," said Dr. Bertrand Bonfond, a co-author of the study from
the Lie`ge University in Belgium. The theory suggests that electrons accelerated in both directions create the multi-spot dance of auroral footprints.

"The Jupiter-Ganymede relationship will be further explored by Juno's
extended mission, as well as the forthcoming JUICE mission from the
European Space Agency," Hue said. "SwRI is building the next generation of
UVS instrumentation for the mission." Video: https://youtu.be/xGUtx0IvYZI

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


========================================================================== Related Multimedia:
* Ganymede_Auroral_Footprint ========================================================================== Journal Reference:
1. V. Hue, J. R. Szalay, T. K. Greathouse, B. Bonfond, S. Kotsiaros,
C. K.

Louis, A. H. Sulaiman, G. Clark, F. Allegrini, G. R. Gladstone, C.

Paranicas, M. H. Versteeg, A. Mura, A. Moirano, D. J. Gershman,
S. J.

Bolton, J. E. P. Connerney, M. W. Davis, R. W. Ebert, J.‐C.

Ge'rard, R. S. Giles, D. C. Grodent, M. Imai, J. A. Kammer,
W. S. Kurth, L. Lamy, B. H. Mauk. A Comprehensive Set of Juno
In Situ and Remote Sensing Observations of the Ganymede Auroral
Footprint. Geophysical Research Letters, 2022; 49 (7) DOI:
10.1029/2021GL096994 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220405102820.htm

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