Space scientists reveal secret behind Jupiter's `energy crisis'

Date:
August 4, 2021
Source:
University of Leicester
Summary:
New research has revealed the solution to Jupiter's 'energy crisis',
which has puzzled astronomers for decades.



FULL STORY ==========================================================================
New research published in Nature has revealed the solution to Jupiter's
'energy crisis', which has puzzled astronomers for decades.


========================================================================== Space scientists at the University of Leicester worked with colleagues
from the Japanese Space Agency (JAXA), Boston University, NASA's
Goddard Space Flight Center and the National Institute of Information
and Communications Technology (NICT) to reveal the mechanism behind
Jupiter's atmospheric heating.

Now, using data from the Keck Observatory in Hawai'i, astronomers
have created the most-detailed yet global map of the gas giant's upper atmosphere, confirming for the first time that Jupiter's powerful aurorae
are responsible for delivering planet-wide heating.

Dr James O'Donoghue is a researcher at JAXA and completed his PhD at
Leicester, and is lead author for the research paper. He said: "We
first began trying to create a global heat map of Jupiter's uppermost atmosphere at the University of Leicester. The signal was not bright
enough to reveal anything outside of Jupiter's polar regions at the time,
but with the lessons learned from that work we managed to secure time on
one of the largest, most competitive telescopes on Earth some years later.

"Using the Keck telescope we produced temperature maps of extraordinary
detail.

We found that temperatures start very high within the aurora, as expected
from previous work, but now we could observe that Jupiter's aurora,
despite taking up less than 10% of the area of the planet, appear to be
heating the whole thing.



========================================================================== "This research started in Leicester and carried on at Boston University
and NASA before ending at JAXA in Japan. Collaborators from each
continent working together made this study successful, combined with
data from NASA's Juno spacecraft in orbit around Jupiter and JAXA's
Hisaki spacecraft, an observatory in space." Dr Tom Stallard and
Dr Henrik Melin are both part of the School of Physics and Astronomy
at the University of Leicester. Dr Stallard added: "There has been a
very long-standing puzzle in the thin atmosphere at the top of every
Giant Planet within our solar system. With every Jupiter space mission,
along with ground-based observations, over the past 50 years, we have consistently measured the equatorial temperatures as being much too hot.

"This 'energy crisis' has been a long standing issue -- do the models
fail to properly model how heat flows from the aurora, or is there some
other unknown heat source near the equator? "This paper describes how
we have mapped this region in unprecedented detail and have shown that,
at Jupiter, the equatorial heating is directly associated with auroral heating." Aurorae occur when charged particles are caught in a planet's magnetic field.

These spiral along the field lines towards the planet's magnetic poles, striking atoms and molecules in the atmosphere to release light and
energy.



==========================================================================
On Earth, this leads to the characteristic light show that forms the
Aurora Borealis and Australis. At Jupiter, the material spewing from
its volcanic moon, Io, leads to the most powerful aurora in the Solar
System and enormous heating in the polar regions of the planet.

Although the Jovian aurorae have long been a prime candidate for heating
the planet's atmosphere, observations have previously been unable to
confirm or deny this until now.

Previous maps of the upper atmospheric temperature were formed using
images consisting of only several pixels. This is not enough resolution
to see how the temperature might be changed across the planet, providing
few clues as to the origin of the extra heat.

Researchers created five maps of the atmospheric temperature at different spatial resolutions, with the highest resolution map showing an average temperature measurement for squares two degrees longitude 'high' by two
degrees latitude 'wide'.

The team scoured more than 10,000 individual data points, only mapping
points with an uncertainty of less than five per cent.

Models of the atmospheres of gas giants suggest that they work like a
giant refrigerator, with heat energy drawn from the equator towards the
pole, and deposited in the lower atmosphere in these pole regions.

These new findings suggest that fast-changing aurorae may drive waves
of energy against this poleward flow, allowing heat to reach the equator.

Observations also showed a region of localised heating in the sub-auroral region that could be interpreted as a limited wave of heat propagating equatorward, which could be interpreted as evidence of the process
driving heat transfer.

Planetary research at the University of Leicester spans the breadth of
Jovian system, from the planet's magnetosphere and atmosphere, out to
its diverse collection of satellites.

Leicester researchers are members of the Juno mission made up of a global
team astronomers observing the giant planet, and are leading Jupiter observations from the forthcoming James Webb Space Telescope. Leicester
also plays a leading role in science and instrumentation on the European
Space Agency (ESA)'s Jupiter Icy Moons Explorer (JUICE), due for launch
in 2022.

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


========================================================================== Journal Reference:
1. J. O'Donoghue, L. Moore, T. Bhakyapaibul, H. Melin, T. Stallard,
J. E. P.

Connerney, C. Tao. Global upper-atmospheric heating on Jupiter
by the polar aurorae. Nature, 2021; 596 (7870): 54 DOI:
10.1038/s41586-021- 03706-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210804123339.htm

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