Page 32 - EngineerIt February 2021

SPACE SCIENCES

What if a perfect CME hit Earth?

By Dr Tony Phillips, Spaceweather.com

ou’ve heard of a “perfect storm.”
But what about a perfect solar
Ystorm? A new study just
published in the research journal Space
Weather considers what might happen if
a worst-case coronal mass ejection
(CME) were to hit Earth.
For years, researchers have been
wondering: what’s the worst the sun
could do? In 2014, Bruce Tsurutani (JPL)
and Gurbax Lakhina (Indian Institute of
Geomagnetism) introduced the “perfect
CME.” It would be fast, leaving the sun at
around 3 000 km/s, and aimed directly at
Earth. Moreover, it would follow another
CME, which would clear the path in front
of it, allowing the storm cloud to hit Earth
with maximum force.
None of this is fantasy. The Solar
and Heliospheric Observatory (SOHO) Sample results from computer modelling a perfect CME impact. The images show the
has observed CMEs leaving the sun at distortion and compression of Earth’s magnetic field as well as induced currents in the
atmosphere. Source: Welling et al, 2020.
speeds up to 3,000 km/s, and there are
many documented cases of one CME
clearing the way for another. Perfect Welling. “MHD results contain far more complexity and hopefully, better reflect the real
CMEs are real. world system.”
Using simple calculations, The team found that geomagnetic disturbances in response to a perfect CME could
Tsurutani and Lakhina showed that a be ten times stronger than Tsurutani and Lakhina had calculated, particularly at latitudes
perfect CME would reach Earth in only above 45 to 50 degrees. “[Our results] exceed values observed during many past
12 hours, allowing emergency extreme events, including the March 1989 storm that brought down the Hydro-Quebec
managers little time to prepare, and power grid in eastern Canada, the May 1921 railroad storm and the Carrington event
slamming into our magnetosphere at itself,” says Welling.
45 times the local speed of sound. In A key result of the new study is how the CME would distort and compress Earth’s
response to such a shock, there would
be a geomagnetic storm perhaps twice
as strong as the Carrington event of
1859. Power grids, GPS and other
high-tech services could experience
significant outages.

Sounds bad? Turns out it could
be worse
In 2020, a team of researchers led by
physicist Dan Welling of the University of
Texas in Arlington, took a fresh look at
Tsurutani and Lakhina’s perfect CME.
Space weather modelling has come a
long way in the intervening six years, so
they were able to come to new
conclusions.
“We used a coupled magneto
hydrodynamic(MHD) ring current-
ionosphere computer model,” says

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