- 3984 - LIGHTNING BOLTS - can become superbolts? Lightning forms when electrical charges in clouds and on the ground interact, and in most of these events the clouds are negatively charged. However, superbolts form during rare cloud-to-ground interactions in which the clouds are positively charged.
------------ 3984 - LIGHTNING BOLTS - can become superbolts?
- Lightning
bolts or flashes of lightning that are
up to 1,000 times brighter than average do exist. After evaluating years of data, scientists
confirmed these ultrabright bolts can produce at least 100 gigawatts of
power. To put that into perspective, the
power produced by all the solar panels and wind turbines in the United States
in 2018 was about 163 gigawatts.
-
- “Superbolts”
are lightning flashes that were over 100 times more intense than typical
lightning. Lightning data for that study
came from observations by “Vela satellites”, which were launched in 1969 to
detect nuclear explosions from space, and operated until 1979.
-
- Vela's
instruments recorded thousands of lightning strikes per year, including
superbolts that struck around the world with most frequent occurrence over the
North Pacific Ocean.
-
- One
superbolt flash near South Africa in 1979 was so powerful that it was thought
to be the detonation of a nuclear bomb.
Another superbolt that struck Newfoundland in 1978 left a one‐mile swath
of damage in its wake.
-
- Trees were
split; television antennas were twisted beyond recognition; transformers were
shattered and circuit breakers hung from power‐line poles, and there were
craters in the new‐fallen snow.
-
- Superbolts
are super-rare, occurring only about
five times in 10 million flashes. In
the southeastern United States on February 19, 2019, the lightning flash
spanned several hundred kilometers and lasted nearly 7 seconds.
-
- Research
focused on superbolts that are substantially brighter than normal lightning —
at least 100 times more energetic — and then looked at the top pulses above
that threshold, with the top cases even going beyond 1,000 times brighter.
-
- Using the
“Fast On‐Orbit Recording of Transient Events” (FORTE) satellite scientisrs
learned that certain viewing conditions did affect lightning brightness, when
the satellite's view was unobstructed by clouds, a bolt could appear somewhat
brighter, and some suspected superbolt observations did fall into that
category.
-
- GLM and
FORTE are both optical instruments, but they measure slightly different aspects
of lightning pulses. FORTE recorded
instantaneous peak power of the superbolts, the moment they were at their
brightest.
-
- By
comparison, GLM measured superbolts' total energy over a 2-microsecond period.
That might not seem like very long, but it is for lightning, where much of the
activity happens at microsecond scales.
-
- The
scientists found that superbolts could emanate from electrical pulses between
clouds, as well as from cloud-to-ground pulses. Superbolts that appeared over
the ocean were fueled by the gradual buildup of electrical charges in the
stormclouds. These bolts would be more
powerful when all that electricity was eventually released.
-
- The
brightest superbolts tended to cluster in geographic regions where large
thunderstorms are common, and superbolt appearance was associated with
"long-horizontal lightning flashes” that can span hundreds of kilometers,
which have been recently termed 'megaflashes”.
-
- 'Gigantic
jet' shot into space may be the most
powerful lightning bolt ever detected.
These lightning bolts blasting out of the top of a cloud over Oklahoma,
and shooting directly into space.
-
- Instead of
striking down toward the ground, or zipping sideways between clouds, this
lightning bolt does something unexpected: It blasts straight upward from the
top of the cloud, shooting 50 miles into the sky, grazing the lower edge of
space.
-
- These are
gigantic jets the rarest and most powerful sort of lightning, occurring as few
as 1,000 times a year and emitting more than 50 times as much energy as a
typical lightning bolt.
-
- By
studying the jet's radio-wave emissions using satellite and radar data,
researchers learned that the bolt moved approximately 300 coulombs of energy
from the top of the cloud to the lower ionosphere, the layer of charged
particles that separates Earth's upper atmosphere from the vacuum of space, or
roughly 60 times the 5-coulomb output of a typical lightning bolt.
-
- The charge
transfer is nearly double the previous largest by a gigantic jet and is
comparable to the largest ever recorded for cloud-to-ground strokes.
-
- Capturing
such detailed data on the massive stroke of lightning required an equally
massive stroke of luck. A citizen scientist based in Hawley, Texas filmed the
jet with a low-light camera on May 14, 2018, watching as the gargantuan
discharge shot out of a cloud top before connecting with charged particles in
the ionosphere, some 60 miles above the ground.
-
- Scientists
analyzing the footage found that, as luck would have it, the jet occurred very
near the center of a large lightning mapping array (LMA), a network of
ground-based radio antennas used to map the locations and times of lightning
strikes. The jet was also within range of several weather radar systems, as
well as a weather-watching satellite network.
-
- With these
sources combined, the researchers studied the size, shape and energy output of
the gigantic jet in unprecedented detail. The researchers found that the jet's highest-frequency
radio-wave emissions (the kind that LMAs are built to detect) came from small
structures called streamers, which develop at the very tip of a lightning bolt
and create a "direct electrical connection between the cloud top and the lower
ionosphere.
-
- The
strongest electric current, meanwhile, flowed considerably behind the
streamers, in a section called the “leader”. The data also showed that while
the streamers were relatively cool, with a temperature of roughly 400 degrees Fahrenheit,
the leader was scorching hot, with a temperature of more than 8,000 degrees F.
This discrepancy is true of all lightning strikes, not just gigantic jets.
-
- Why does
lightning sometimes blast up instead of down? Scientists still aren't totally
clear on that, but it likely involves some sort of blockage that prevents
lightning from escaping through the bottom of a cloud; gigantic jets are
typically observed in storms that don't produce many cloud-to-ground lightning
strikes.
-
- There is usually
a suppression of cloud-to-ground discharges.
In the absence of the lightning discharges we normally see, the gigantic
jet may relieve the buildup of excess negative charge in the cloud.
-
- More
research — and a lot more luck — is needed to understand these epic,
upside-down lightning strikes.
-
May 3, 2023 LIGHTNING
BOLTS - can become superbolts? 3984
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--------------------- --- Friday, May 5, 2023
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