Name: 在太陽風暴期間，地球磁場是如何扭曲和彎曲的？ (How Earth's Magnetic Field Twists and Buckles During Solar Storms)
Uploaded: 2021-01-14T09:58:40.000Z
Duration: 10 min 23 s
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Traveling at the near speed of light, energetic particles shooting out from the sun can zip

through space, smack into our planet’s atmosphere, and cause incredible disruptions. And one

of the biggest impacts we know of happened during the tail end of the Vietnam War. President

Nixon really wanted to pull us out, but wanted to do it sort of saving face, and decided

that the best way to do that was to stop the flow of war material into North Vietnam. The

decision was to mine Haiphong Harbor, and many of the smaller harbors to the South.

This is Delores Knipp, a space weather scientist and former officer in the US Air Force. She

likes digging into dusty archives, and uncovered a war mystery that’s now connected to a

major solar event. Space weather forecasters had noticed that there was one region on the

Sun that appeared to be a little more active than anticipated. They kept watching it, and

then when it came around in late July 1972 on the east limb of the Sun it was already

large. It did start producing solar flares, producing coronal mass ejections but at that

time we didn't have those words. We didn't really understand the concept of the Sun actually

throwing mass, and magnetic material out. We had a general sense that something like

a plasma cloud was coming at us, but our ideas were that, "Well, okay it might get here in

a couple three days." As a matter of fact, it got here in 14.6 hours. Typically, the

solar wind is moving at about 400 kilometers per second, which is supersonic, but very,

very tenuous. But this particular event in 1972 traveled at about 2,800 kilometers per

second, so seven times faster than the norm, and carrying tremendous magnetic field, and

mass with it. And when that hit, our magnetic shield virtually buckled. We had no idea that

something could come from the Sun that fast. We were pretty much unprepared. And when it

hit earth, those sea mines blew up. Those mines were what the president was relying

on to keep the pressure on in the war. And suddenly the whole mine field had been swept

by nature, by the Sun, by a CME. That created probably one of the largest solar energetic

particle events in recorded history. The naval observers who were up at the time, it was

just past dawn, noted that there were a half-dozen sea mines that blew within 30 seconds. And

they go, "Whoa! Did we do that?" It was a furious time in terms of the Navy records,

trying to figure out what had happened. In these declassified reports, Delores found

just a few lines that had basically said, "Yes, in August of 1972 "a solar storm swept

the sea mines in Haiphong Harbor." And so I go, "Oh, it looks like something did happen." There

were and are many impacts that have not been adequately described. And they're just now

starting to come to light. Our sun is a huge ball of magnetized gas and plasma, and it’s

activity goes through a roughly 11 year cycle. We know whether we’re in a solar maximum or

solar minimum by counting the number of sunspots on the surface. These spots are indicators

for giant eruptions, like solar flares, which are sudden outbursts of energy and coronal

mass ejections, which are even larger but slower eruptions from the Sun’s corona. They

can increase during the sun’s cycle, but luckily, we have some built in protection.

We can think of Earth's magnetic field as being kind of a magnetic cocoon that keeps

most of the solar winds, magnetic field, and the plasma outside of Earth's atmosphere.

But when the sun decides to launch a really big ejection, sometimes the magnetic field

has to deform so dramatically that currents are generated, and those currents can actually

flow along the magnetic field lines down to Earth's surface. And that's one of our biggest

concerns. If those extra currents are flowing in the ground, they're always looking for

the path of least resistance. And when they find a path along a long conducting pipe,

or in older times, telegraph wires, or now in our power grid, they will take that path. We're

starting to understand that these are not once in a century events. These probably occur

more often than we think. We're in solar minimum now, we're kind of relaxed the next

solar maximum was forecast to be not too spectacular. The August '72 event came out of small sunspot

cycles. So we can't just take the sunspot count as the, oh, we don't have to worry about

it situation. We actually have to be monitoring the Sun 24/7. Today at NOAA’s Space Weather

Prediction Center, we have more eyes on the sun and better models to help us predict space

weather, which is affecting our magnetosphere, it's creating the Aurora, it's also energizing

particles and creating radiation environment that can affect satellites, it affects the

ionosphere in those regions and that impacts airlines that have flights from New York to

Beijing. There are several things that are really important for conducting space weather

operations. The first are satellites, which serve as sentinels out in the abyss. The

GOES satellites give you the daily weather that you see on the news at night. But in

addition, the space weather observations consist of monitoring the energetic particles

in Earth's radiation belt at geosynchronous orbit. They also monitor the earth's magnetic

field and its variations. There's solar observations that are looking at the Sun in x-rays, in

extreme ultraviolet to give us information about activity on the sun. Activity like coronal

mass ejections and solar flares, which have different lead times once they erupt. We

classify solar flares here starting with what we call A. And then we have the B level and

then C level and then M’s and then X’s. And each one of those categories is ten times

more intense than the other. The 1972 event that blew up a bunch of sea mines were connected

to X class flares. We have instruments measuring the intensity of the solar radiation and it

appears very quickly in near real time in front of our forecasters and then they could

use that information to provide their warnings and alerts. The other type of major event

is this coronal mass ejection, it’s moving much slower. Right now we're using coronagraphs

that are on a NASA satellite. It takes as short as maybe 14 hours for a very fast event…but

it can take more normally several days to reach us. We have a little bit more lead

time..to say something about how fast is it moving? When do we expect it at Earth? How

long do we expect it to last?" We've got another satellite that's entirely outside of earth's

magnetosphere in a location between Earth and the Sun called the Lagrange point L1.

That's a stable place where both the gravity and the centrifugal force of the satellite

balance out the earth's gravitational force and it's always there as a buoy upstream to

give us a warning of what's coming at Earth. Another key piece of their operations are models,

which are constantly evolving to improve predictions. The Wang Sheeley Arge Enlil model shows us where

there's high speed solar wind coming at us, where there's low speed solar wind coming

at us, the density of that solar wind. When there's a large eruption on the sun of a coronal

mass ejection. The Wang Sheeley Arge Enlil model.. takes that coronal mass ejection and

puts it through that system and then it tells us what's going to arrive at Earth. The Geospace

model is telling us about magnetic variations in the vicinity of Earth and those magnetic

variations can cause geo electric fields. Those geo electric fields can drive currents

and power lines and disrupt power grids. Models are only as good as our understanding and

models don't catch everything and there are times where we have been surprised. There

are a lot of features about the sun that we still don't understand. We need to be able

to model how the Sun's interior works the solar atmosphere. We need to be able to monitor

active regions of the sun and how they form. There is a huge concerns at the highest levels in

government to be able to better prepare for a large event to better mitigate the effects. I'm

optimistic about all of these new advances that are coming in and all of these things

which are going to contribute to our preparedness for the things the Sun is throwing at us.

It's a real sense of adventure. It's like you can realize that you're a part of something

that is developing. The Sun, it's so far away and yet, within a short amount of time, it

can have this amazing impact. And it's not just oh yeah, the sun warms us up and we have

seasons, there's a lot more going on, and it's a very connected system. Even though

some of these stories have been hidden these things have actually happened, and there's

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在太陽風暴期間，地球磁場是如何扭曲和彎曲的？ (How Earth's Magnetic Field Twists and Buckles During Solar Storms)

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