- 4546 -
SOLAR FLARES and the damage they cause? - The
sun is on the verge of a significant event called a “magnetic field
reversal”. This phenomenon happens
roughly every 11 years and marks an important stage in the solar cycle. The
shift in polarity indicates the halfway point of solar maximum, the height of
solar activity, and the beginning of the shift toward solar minimum.
---------------------------------- 4546 - SOLAR FLARES and the damage they cause?
- The last time the sun's magnetic field
flipped was toward the end of 2013. To
understand the magnetic field's reversal, it's important to be familiar with
the solar cycle. This approximately 11-year cycle of solar activity is driven
by the sun's magnetic field and is indicated by the frequency and intensity of
sunspots visible on the surface. The height of solar activity during a given
solar cycle is known as solar maximum, and current estimates predict it will
occur between late 2024 and early 2026.
-
- A lesser-known cycle that encapsulates two
11-year solar cycles. Known as the “Hale cycle”, this magnetic cycle lasts
approximately 22 years, through which the sun's magnetic field reverses and
then reverts to its original state.
-
- During solar minimum, the sun's magnetic
field is close to a dipole, with one north pole and one south pole, similar to
Earth's magnetic field. But as we shift toward solar maximum, the sun's
magnetic field becomes more complex, without a clear north-south pole
separation. By the time solar maximum passes and solar minimum arrives, the sun
has returned to a dipole, with a flipped
polarity.
-
- The upcoming switch in polarity will be
from the northern to southern magnetic field in the Northern Hemisphere and
vice versa in the Southern Hemisphere.
This will bring it to a similar magnetic orientation to Earth, which
also has its southern-pointing magnetic field in the Northern Hemisphere.
-
- The reversal is driven by sunspots,
magnetically complex regions of the sun's surface that can spawn significant
solar events, such as solar flares and “coronal mass ejections” (CMEs), large
blasts of plasma and magnetic field.
-
- As sunspots emerge close to the equator,
they will have an orientation matching the old magnetic field, while sunspots
forming closer to the poles will have a magnetic field matching the incoming
magnetic orientation. This is called “Hale's law”.
-
- The magnetic field from active regions
makes its way toward the poles and eventually causes the reversal. But the exact underlying cause of such a flip
in polarity remains mysterious.
-
- What we do know is that the solar magnetic
field flip is not instantaneous. It's a gradual transition from a dipole to a
complex magnetic field, to a reversed dipole over the entire 11-year solar
cycle. "In short, there is no specific 'moment' in which the sun's poles
flip. It's not like the Earth, where
the flip is measured by the migration of the North/South pole.
-
- It generally takes a year or two for a
complete reversal, but it can vary significantly. The north polar field of Solar Cycle 24,
which ended in December 2019, took nearly five years to reverse.
-
- How does the sun's magnetic flip affect
us? There is no doubt that the sun has
been incredibly active recently, firing out numerous powerful solar flares and
CMEs, triggering strong geomagnetic storms on Earth, which, in turn, have
produced some incredible auroral displays.
-
- Space weather is typically the strongest
during solar maximum, when the sun's magnetic field is also the most
complex. One side effect of the
magnetic field shift is slight but primarily beneficial. It can help shield Earth from galactic cosmic
rays which are high-energy subatomic particles that travel at near light speed
and can damage spacecraft and harm orbiting astronauts who are outside Earth's
protective atmosphere.
-
- As the sun's magnetic field shifts, the
"current sheet", a sprawling surface that radiates billions of miles
outward from the sun's equator, becomes very wavy, providing a better barrier
against cosmic rays.
-
- When giant solar storms hit Earth, they
trigger beautiful auroral displays high in Earth’s atmosphere. There’s a dark
side to this solar activity, though. The “space weather” it sets off also
threatens our technology. The potential for damage is why we need highly
accurate predictions of just when these storms will impact our planet’s
magnetosphere.
-
- The specific places on the Sun where these
storms erupt are called “coronal mass ejections” (CMEs). They’re huge
explosions of magnetically charged particles and gases from the Sun. They
travel through space and hit whatever is in their way, including planets.
-
- When that cloud of charged particles hits
our magnetic field, it sets off a chain reaction of events. It creates beautiful auroral displays,
northern and southern lights that dance in the skies. But, they also slam into
and can damage orbiting satellites, including all our telecommunications and
navigation systems for planes, boats, and trains.
-
- The danger is even greater for astronauts
aboard orbiting space stations because radiation is a constant threat to human
life. On Earth, those storms can cause huge circulating electrical currents
that can damage electric power grids. The damage to technology just ripples
across the planet.
-
- This is why satellite operators and others
want more accurate predictions of just when a space weather event triggered by
a CME will hit us. To figure that out, solar physicists have to look back at
the Sun and the sequence of events that cause CMEs.
-
- CMEs emanate from active regions on the
Sun. These are places with very strong magnetic fields. The magnetic field
lines form loops that get twisted and eventually, they break. When that
happens, there’s a huge outburst of material, the CME. Typically, they travel
out from the Sun at anywhere from 100 km/sec to 3,000 km/sec. That large
uncertainty makes it tough to predict when the solar cloud will hit Earth.
-
- The height above the Sun where the magnetic
field becomes unstable is called the “critical height” and it can help
scientists predict the speed and arrival time of a coronal mass ejection.
By measuring how the strength
of the magnetic field decreases with height, we can determine this critical
height. This data can then be used along
with a geometric model which is used to track the true speed of CMEs in three
dimensions, rather than just two, which is essential for precise predictions.
-
- Knowing the actual speed of the CME to a
higher degree of accuracy will let solar physicists predict when it will hit
Earth. That, in turn, will allow satellite operators, grid owners, space
agencies, and others to prepare for the action and protect their assets.
-
- Our Sun goes through periods where it is
more “outbursty” than others. Some of the strongest solar storms occur during
the solar maximum part of the Sun’s 11-year sunspot cycle. Whenever they happen
they can cause a lot of damage.
-
- One famous storm occurred on March 13,
1989. It was a combo of two CMEs that lifted off the Sun on March 10th and
March 12th. They stirred up currents low in Earth’s atmosphere at the same time
they triggered auroral displays. At the time, power grids were not necessarily
“hardened” against such events. As a result, the Hydro-Quebec power grid shut
down and suffered tremendous damage. The power was out for days across eastern
Canada and parts of the United States.
-
- Another huge storm hit around Halloween in
2003. It affected satellite systems, cut off communications, some power systems
shut down, and people around the world saw a dazzling display of aurorae. In
space, the SOHO solar satellite shut down briefly. Astronauts onboard the ISS
had to take shelter in a safe place aboard the station.
-
- Today, we’re in another cycle of heightened
solar activity. We’ve already seen strong storms in May of 2024, and more will
surely occur. So far they haven’t caused much damage, and they’ve given us some
lovely auroral displays. Luckily, advanced research on these solar storms has
helped technology operators and space agencies “harden” their systems.
-
- However, there’s only so much they can do
to protect their assets. Having highly accurate advance predictions of just
when a CME will impact our planet is a big step forward. At the very least,
these operators will be able to reposition satellites, strengthen their power
grids and other communications technology, and give astronauts in space advance
warning. In future years, when we have people on the Moon or on their way to
Mars, such predictions will help keep them safe, too.
-
-
August 31, 2024 SOLAR
FLARES and the damage they
cause? 4546
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-- email feedback, corrections, request for
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--- to:
------
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------ “Jim Detrick” -----------
--------------------- --- Tuesday, September 3,
2024
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