(Full title: Scientists have spotted unexpected X- and C-
shaped structures in the atmosphere. They are struggling
to explain them)
(Lots of illustration/graphics in the article)
Each day, radio signals from key communications and
navigation satellites travel freely through a layer of
Earth’s atmosphere known as the ionosphere.
Floating 50 to 400 miles (80 to 643 kilometers) above our
heads, directly beneath the lowest reaches of space where
some communications satellites orbit, this zone in the
upper atmosphere is also home to many unsolved puzzles —
including an alphabet-shaped one that has the potential
to thwart all that those radio signals do to keep life on
our planet running smoothly.
Astronomers have known for some time that X-shaped
crestlike formations can appear in the ionosphere’s
plasma — a sea of charged particles — after solar storms.
Volcanic events and extreme weather on Earth can also
cause the phenomenon. Huge eruptions, such as the Hunga
Tonga-Hunga Ha’apai eruption in January 2022, loft
particles into Earth’s atmosphere that even reach space.
Thunderstorms and hurricanes can create pressure waves
that find their way to the ionosphere.
Meanwhile, at night during these active periods, when the
sun’s radiation isn’t as strong, is also when low-density
bubbles appear in the ionosphere.
Satellite data hasn’t always been able to capture the
full picture of what’s occurring in the ionosphere, but
NASA’s GOLD mission has a bird’s-eye view of the
atmospheric layer over the Western Hemisphere from space,
revealing how different factors cause disturbances in the
ionosphere.
Now, astronomers looking at data collected by the GOLD
mission have found similar features shaped like Xs and
never-before-seen Cs that surprisingly seem to have
appeared during “quiet times” when there were no
atmospheric disturbances, according to new research. The
findings are upending what’s known about how the unusual
structures might form and their potential impacts.
The mission’s data is helping scientists to see “how
complex Earth’s atmosphere is” while showing that it’s
more variable than expected, even when there isn’t an
obvious cause behind the alphabet-shaped disturbances in
the ionosphere, said Jeffrey Klenzing, a research
scientist who studies the ionosphere at NASA’s Goddard
Space Flight Center in Greenbelt, Maryland.
“I would suspect that it’s always been happening,” he
said. “And really the issue has basically been that we
haven’t had enough data to really see that it is
happening.”
Gaining a better understanding of the letter-shaped
phenomena may help scientists unlock the dynamics between
the ionosphere and weather — and how the interplay may
pose risks to people and systems on Earth.
X-shaped crests
The ionosphere is not always a perfectly smooth layer of
gas, and it’s constantly changing. It becomes electrified
when sunlight hits it. Solar radiation knocks electrons
off atoms and molecules to create plasma that allows
radio communications to travel over long distances.
But as the sun fades away at night, the ionosphere thins
out and the once-charged particles settle down and become
neutral particles, according to NASA. This is when
bubbles can form in the ionosphere.
Earth’s magnetic field lines also carry charged particles
free-floating in the atmosphere to two dense bands north
and south of the equator that are known as crests.
Given their various densities, crests and bubbles
resembling different shapes within the ionosphere can
cause interference with communication and GPS signals.
The GOLD, or Global-scale Observations of the Limb and
Disk, mission has been monitoring the ionosphere since it
launched in January 2018. The satellite zips around Earth
at the same rate that our planet rotates, enabling the
spacecraft to remain in a constant hover over the Western
Hemisphere.
GOLD spotted the clearest signs of the X- and C-shaped
features in 2019, 2020 and 2021 — and in unexpected
places. The evidence is causing researchers to question
the potential effects of the Xs and Cs on communication
signals in the future.
“NASA’s GOLD mission is the first one to observe the
alphabetical shapes unambiguously,” said Fazlul Laskar,
lead author of an April study about the X shapes
published in the Journal of Geophysical Research: Space
Physics.
“These shapes reveal that the ionosphere can be very
dynamic at times displaying unexpected structures,” added
Laskar, a research scientist at the University of
Colorado’s Laboratory for Atmospheric and Space Physics.
“Also, it demonstrates that the lower atmospheric weather
could have enormous impact on the ionosphere.”
GOLD observing multiple instances of the Xs forming
“during geomagnetic quiet conditions” — instead of during
atmospheric disturbances such as solar storms or
terrestrial weather, when they were previously seen — now
tells scientists some other mechanism must be responsible
for forming the shapes, Laskar said. Computer models
point to changes in the lower atmosphere pulling plasma
downward as a possible explanation, according to the
study.
“The (appearance of the) X is odd because it implies that
there are far more localized driving factors,” Klenzing
said. He was not involved in the April study. “This is
expected during the extreme events, but seeing it during
‘quiet time’ suggests that the lower atmosphere activity
is significantly driving the ionospheric structure.”
Never-before-seen C bubbles
Separately, GOLD also observed C-shaped plasma bubbles
that may be influenced by other factors.
Typically, plasma bubbles are long and straight because
they form along Earth’s magnetic field lines. But some of
the bubbles resemble curved shapes, which look like Cs or
reverse Cs, and scientists think they could be shaped by
Earth’s winds.
While C shapes may form if winds increase with altitude,
reverse Cs could form if winds decrease with altitude,
according to research models.
“It’s a little like a tree growing in a windy area,”
Klenzing said. “If the winds are typically to the east,
the tree starts to tilt and grow in that direction.”
But GOLD observed C-shaped and reverse C-shaped plasma
bubbles unusually close together, only about 400 miles
(644 kilometers) apart, or the about distance between
Baltimore and Boston, according to a November 2023 study
published in the Journal of Geophysical Research: Space
Physics.
“Within that close proximity, these two opposite-shaped
plasma bubbles had never been thought of, never been
imaged,” said Deepak Karan, research scientist at the
University of Colorado’s Laboratory for Atmospheric and
Space Physics. Karan works on the GOLD mission and is the
lead author of the C-shape study and coauthor of the X-
shape study.
Tornado-like activity, wind shear or a vortex could be
creating turbulence in the atmosphere that causes
changing wind patterns in such a small area, Karan said.
But they never expected to see such oppositely structured
bubbles so close together.
“The fact that we have very different shapes of bubbles
this close together tells us that the dynamics of the
atmosphere is more complex than we expected,” Klenzing
said.
So far, GOLD has only observed two instances of the close
pairings, but the C-shaped bubbles have the potential to
disrupt communications.
“It’s really important to find out why this is
happening,” Karan said. “If a vortex or a very strong
shear in the plasma has happened, this will completely
distort the plasma over that region. Signals will be lost
completely with a strong disturbance like this.”
Karan said these vortices, which can last for hours,
resemble tornadoes that occur in Earth’s lower
atmosphere, but the puzzle scientists can’t seem to solve
is how the structures form in the ionosphere during
“quiet time.”
“Unraveling the mystery of these plasma bubble formations
is not only a scientific curiosity but also of practical
importance for mitigating the adverse effects on
communication and navigation systems,” he said.
Attempts to understand how the bubbles form so close
together with current modeling tools has been
unsuccessful, Karan said. It is his hope that by
publishing the research and including all possible
formation mechanisms, the scientific community can come
together to solve the mystery.
A golden trove of data
The GOLD mission is well suited to capture unexpected
features in the ionosphere because of its orbit. While
previous satellite missions could only capture a small
piece of an event in one dimension, GOLD can take
multiple images of an event over the course of hours,
Laskar said. And he expects even more surprising features
to be revealed in GOLD’s data in the future.
“Due to such wide view and continuous measurements, GOLD
has allowed us to observe these mysteries within the
ionosphere,” Karan said.
He said there are many questions that remain unanswered
about this atmospheric layer, such as how changes in the
lower atmosphere and solar activity influence the motion
of charged particles in the ionosphere.
Given that solar storms could increase due to the sun
approaching the peak of its 11-year cycle, called solar
maximum, astronomers also want to have a better
understanding of how the ionosphere’s composition changes
during the events because sudden swells of charged
particles can increase drag on satellites and shorten
their lifespans, Karan said.
Electric currents also flow in the ionosphere, and an
increase in the electric current during solar storms can
damage transmission lines and ground transformers on
Earth, he said.
During the May 10 geomagnetic storm that hit Earth,
tractor company John Deere reported that some customers
reliant on GPS for precision farming experienced a
disruption.
“The biggest impact to the agriculture industry centered
on GPS guidance systems,” said Tim Marquis, a senior
product manager at John Deere, in a statement. “GPS
receivers work when a signal is received at regular
intervals, much like a beat from a metronome, from a
satellite in orbit. During solar storms, that signal hits
a ‘fog’ of charged particles and can be lost. And
machines can’t know precisely where they are thanks to
this interference.”
Pending results from studies of GOLD data during the May
10 geomagnetic storm could help astronomers in the
development of a space weather forecasting system, Laskar
said.
“One thing we need to have is a space weather forecasting
system that could tell us when we are going to have
problems with GPS signals and when satellite orbits may
need to be adjusted to avoid catastrophic collisions,” he
said.
Losing a GPS signal on Earth isn’t just annoying for
people trying to find a location they’ve never been to.
The navigation signals are widely used in shipping,
transportation, agriculture and construction, too.
When bubbles, crests or solar storms disrupt the plasma
distribution in the ionosphere, radio signals passing
through the atmospheric layer can be changed, lost or
fade away, Karan said.
“There could be life-threatening impacts due to the
sudden loss of GPS signals in aircraft, ships, and
automobiles which is even scary to imagine,” he said.
GOLD and future mission concepts could help scientists to
better understand the phenomena at work behind these
recently observed X and C features — and even perhaps
predict such changes before they occur in the ionosphere.
“One of the challenges for ionospheric researchers is to
eventually be able to predict its dynamics in advance,”
Laskar said, “so that we can be prepared for GPS signal
loss and interruptions to satellite communications.”
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