This large, rotating pattern of plasma roiled the ionosphere — similar to its surface counterparts.
Plasma and the spiral auroral arms of a space
hurricane twirl high Earth's polar region in this artist’s concept. |
The morning of August 20, 2014 was a quiet one in
Earth’s ionosphere. The solar wind was calm and slack, and the orientation of
the Sun’s magnetic field was stable, not conducive to producing much space
weather.
But then, hundreds of miles above the North Pole, the
ionosphere suddenly whipped itself into a fury, spawning a massive space
hurricane some 600 miles (1,000 kilometers) wide — a cyclone of plasma swirling
above Earth for eight hours.
The phenomenon was captured in real-time by U.S.
military weather satellites. But it was only recently uncovered in archival
data by a team led by researchers at Shandong University in China.
“Until now, it was uncertain that space plasma
hurricanes even existed, so to prove this with such a striking observation is
incredible,” said co-author Mike Lockwood of the University of Reading in a
press release.
More than a metaphor
The moniker “space hurricane” isn’t just a catchy
nickname — the physics of how it formed are actually analogous to how “normal”
hurricanes gather and focus energy in the lower atmosphere. Like their
atmospheric counterparts, this space storm was instigated by an area of low
pressure that gave rise to rapid convection.
On Earth, that convective process occurs from below:
heat from warm ocean waters drives evaporation and rising air, dumping energy
into the atmosphere that gets focused by inrushing wind.
In space, though, that convective energy comes from
above — thanks to the magnetic fields of the Earth and Sun interacting and
shearing across one another.
The Sun’s magnetic field has a wavy pattern as it
stretches out into the solar system, meaning it can be aligned northward or
southward depending on where Earth sits in it. On that August day in 2014, the
region of the Sun’s magnetic field around Earth happened to be aligned
northward. That means it doesn’t neatly connect to Earth’s magnetic field,
which is also aligned northward — the field lines tend to repel each other,
typically leading to calm space weather conditions. But these conditions
sometimes give rise to a spot of aurora near the poles, where electrons rain
downward and electric current flows up, just like the convection at the heart
of a hurricane.
This caused the surrounding plasma to begin flowing
around the central spot of convection, forming “rain bands” of electrons that
produced spiral auroral arms around a stable eye. At the core of the system was
a corkscrew-shaped magnetic field that funneled magnetic energy from space into
Earth’s ionosphere — and it lasted eight hours before dissipating.
Universal phenomenon
Though space hurricanes don’t have the same kind of
deadly impact that atmospheric cousins can, the influx of energetic particles
such storms bring to the ionosphere could interfere with satellites, even
affecting their orbits by creating more drag on them.
And because this particular storm popped up during a
relatively quiet period of geomagnetic activity, the researchers say space
hurricanes may be even more common than we thought. “Plasma and magnetic fields
in the atmosphere of planets exist throughout the universe, so the findings
suggest space hurricanes should be a widespread phenomena,” said Lockwood.
Reference: Press Release
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