Strong winds power electric fields in the upper atmosphere

Date:
November 29, 2021
Source:
NASA/Goddard Space Flight Center
Summary:
Using observations from NASA's ICON mission, scientists presented
the first direct measurements of Earth's long-theorized dynamo on
the edge of space: a wind-driven electrical generator that spans
the globe 60-plus miles above our heads. The dynamo churns in the
ionosphere, the electrically charged boundary between Earth and
space. It's powered by tidal winds in the upper atmosphere that
are faster than most hurricanes and rise from the lower atmosphere,
creating an electrical environment that can affect satellites and
technology on Earth.



FULL STORY ==========================================================================
What happens on Earth doesn't stay on Earth.


========================================================================== Using observations from NASA's ICON mission, scientists presented
the first direct measurements of Earth's long-theorized dynamo on the
edge of space: a wind-driven electrical generator that spans the globe
60-plus miles above our heads. The dynamo churns in the ionosphere, the electrically charged boundary between Earth and space. It's powered by
tidal winds in the upper atmosphere that are faster than most hurricanes
and rise from the lower atmosphere, creating an electrical environment
that can affect satellites and technology on Earth.

"Half of the motion of the plasma can be attributed to the winds that we observe right there on that same magnetic field line," Immel said. "That
tells you it's an important observation to make if you want to predict
what plasma is doing." ICON's first year of observations coincided with
solar minimum, the quiet phase of the Sun's 11-year activity cycle. During
this time, the Sun's behavior was a low, constant hum. "We know the
Sun's not doing much, but we saw a lot of variability from below, and
then remarkable changes in the ionosphere," Immel said. That told the researchers they could rule out the Sun as the main influence.

As the Sun ramps up to its active phase, scientists will be able to
study more complex changes and interactions between space and Earth's atmosphere.

Immel said he is excited to have this confirmation of long-held ionosphere theories. "We found half of what causes the ionosphere to behave as it
does right there in the data," he said. "This is what we wanted to know." Still, Maute said, "This leaves room to explore what else is contributing
to the ionosphere's behavior."


========================================================================== Tides ripple up through the sky, building in strength and growing before gusting through the ionosphere. The electric dynamo whirs in response.

The scientists analyzed the first year of ICON data, and found
high-altitude winds strongly influence the ionosphere. "We traced the
pattern of how the ionosphere moves, and there was a clear wave-like structure," Harding said.

Changes in the wind, he explained, directly corresponded to the dance
of plasma 370 miles above Earth's surface.

The farther the atmosphere stretches away from the surface, the thinner it becomes and the less turbulence there is to disrupt these motions. That
means small tides generated near the surface can grow much larger when
they reach the upper atmosphere. "Changes in the winds up there are
mostly controlled by what happens below," Harding said.

ICON's new wind measurements help scientists understand these tidal
patterns that span the globe and their effects.

In most generators, these components are bound tightly so they stay
put and act predictably. But the ionosphere is free to move however it
likes. "The current generates its own magnetic field, which fights Earth's magnetic field as it's passing through," Immel said. "So you end up with a
wire trying to get away from you. It's a messy generator." Following the
whims of the ionosphere is key to predicting space weather's potential
impacts. Depending on which way the wind blows, plasma in the ionosphere
shoots out into space or plummets toward Earth. This behavior results from
the tug-of-war between the ionosphere and Earth's electromagnetic fields.



==========================================================================
The dynamo, which lies at the lower end of the ionosphere, has remained
a mystery for so long because it's difficult to observe. Too high for scientific balloons and too low for satellites, it has eluded many of
the tools researchers have to study near-Earth space. ICON is uniquely
equipped to investigate this part of the ionosphere from above by taking advantage of the upper atmosphere's natural glow to detect the motion
of plasma.

ICON simultaneously observes powerful winds and migrating plasma. "This
was the first time we could tell how much the wind contributes to the ionosphere's behavior, without any assumptions," said Astrid Maute,
another study co-author and ICON scientist at the National Center for Atmospheric Research in Boulder, Colorado.

Only in the past decade or so, Immel said, have scientists realized
just how much those rising winds vary. "The upper atmosphere wasn't
expected to change rapidly," he said. "But it does, day to day. We're
finding this is all due to changes driven up from the lower atmosphere."
Wind power Familiar are the winds that skim the surface of Earth, from
gentle breezes to bracing gusts that blow one way and then the other.

High-altitude winds are a different beast. From 60 to 95 miles above the ground, in the lower thermosphere, winds can blast in the same direction
at the same speed -- around 250 mph -- for a few hours at a time before suddenly reversing direction. (By comparison, winds in the strongest
Category 5 hurricanes tear at 157 mph or more.) These dramatic shifts
are the result of waves of air, called tides, born at Earth's surface
when the lower atmosphere heats up during the day then cools down at
night. They surge through the sky daily, carrying changes from below.

The new work, published today in Nature Geoscience, improves our
understanding of the ionosphere, which helps scientists better predict
space weather and protect our technology from its effects.

Launched in 2019, ICON, short for Ionospheric Connection Explorer, is
a mission to untangle how Earth's weather interacts with the weather in
space. Radio and GPS signals zip through the ionosphere, which is home
to auroras and the International Space Station. Empty pockets or dense
swells of electrically charged particles can disrupt these signals.

Scientists who study the atmosphere and space weather have long included Earth's dynamo in their models because they knew it had important
effects. But with little information, they had to make some assumptions
about how it works.

Data from ICON is the first concrete observation of winds fueling the
dynamo, eventually influencing space weather, to feed into those models.

"ICON's first year in space has shown predicting these winds is key to improving our ability to predict what happens in the ionosphere," said
Thomas Immel, ICON principal investigator at University of California, Berkeley, and lead author of the new study.

Earth's sky-high generator The ionosphere is like a sloshing sea of electrically charged particles, created by the Sun and intermixed
with the neutral upper atmosphere. Sandwiched between Earth and space,
the ionosphere responds to changes from both the Sun above and Earth
below. How much influence comes from each side is what researchers are interested in figuring out. Studying a year of ICON data, the researchers
found much of the change they observed originated in the lower atmosphere.

Generators work by repeatedly moving an electricity-carrying conductor --
like a copper wire -- through a magnetic field. Filled with electrically charged gases called plasma, the ionosphere acts like a wire, or rather,
a tangled mess of wires: Electricity flows right through. Like the dynamo
in Earth's core, the dynamo in the atmosphere produces electromagnetic
fields from motion.

Strong winds in the thermosphere, a layer of the upper atmosphere
known for its high temperatures, push current-carrying plasma in the
ionosphere across invisible magnetic field lines that arc around Earth
like an onion. The wind tends to push on chunky, positively charged
particles more than small, negatively charged electrons. "You get
pluses moving differently than minuses," said co-author Brian Harding,
a physicist at University of California, Berkeley. "That's an electric current." Video about strong winds that power electrical field in
Earth's upper atmosphere: https://www.youtube.com/watch?v=pt9RCMZmMkc ========================================================================== Story Source: Materials provided by
NASA/Goddard_Space_Flight_Center. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Thomas J. Immel, Brian J. Harding, Roderick A. Heelis, Astrid Maute,
Jeffrey M. Forbes, Scott L. England, Stephen B. Mende, Christoph R.

Englert, Russell A. Stoneback, Kenneth Marr, John M. Harlander,
Jonathan J. Makela. Regulation of ionospheric plasma velocities
by thermospheric winds. Nature Geoscience, 2021; DOI:
10.1038/s41561-021-00848-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211129172751.htm

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