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Learn How NASA Tracks The Solar Cycles
Space.com
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30/06/2025
The 11-year solar cycle is tracked by NASA, learn how they do it.
Credit: NASA Goddard Space Flight Center
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Tech
Transcript
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00:00
There's a rhythm emanating from the Sun to the edges of the solar system.
00:04
Roughly every 11 years, our star ramps up to a turbulent state expelling violent eruptions.
00:10
After a peak, it calms down to a quieter phase before starting all over again.
00:15
This is known as the solar cycle.
00:18
This ebb and flow of solar activity affects the entire solar system,
00:22
including spacecraft electronics and astronauts
00:25
that can be affected by particle radiation if they're not sufficiently protected.
00:29
Understanding the solar cycle is one of the oldest problems in solar physics,
00:34
and now predicting it is more critical than ever as we venture to the Moon, Mars and beyond.
00:40
So here are ways we've learned about tracking it.
00:47
So welcome to the dome.
00:49
Today we're going to observe the Sun and see if it has some sunspots.
00:53
Every morning when the skies are clear,
00:55
Olivier looks through this telescope in search of sunspots.
00:59
These are dark blotches on the Sun that are the main source of solar eruptions.
01:03
They appear and disappear on the Sun's surface.
01:06
So we're not looking at the Sun.
01:08
In fact, we're looking at the shadow of the instrument.
01:13
Then we put the paper always at the same place.
01:17
And then we can start drawing.
01:21
Olivier and a team of sun observers record the pattern of sunspots by pencil.
01:26
The first known record of sunspots date back to around a thousand years ago in China.
01:31
After the invention of the telescope in the 17th century,
01:34
routine observations were made.
01:36
Today, sunspot drawers still use the same technique.
01:40
While we've created satellites that can see the Sun in much more detail in recent decades,
01:45
drawing by hand keeps the centuries-long record consistent.
01:49
The sunspot number record goes back farther than any other instrument,
01:53
allowing scientists to analyze the Sun's behavior over many, many solar cycles.
01:57
Sunspot numbers are collected from observatories around the world and are averaged.
02:02
During every 11-year cycle, the number of sunspots rise from zero to a peak
02:07
and then go back down to zero again.
02:10
Scientists use these numbers to determine when a new solar cycle begins
02:14
and how active a cycle is.
02:16
Solar maximum, the period of highest activity, can vary wildly from cycle to cycle.
02:22
The more sunspots there are, the higher the frequency of solar storms of all types.
02:28
Some that create aurora and some that can affect power grids on Earth.
02:32
But sunspot number isn't the only indicator we see.
02:35
These numbers are often combined with other signs.
02:39
At the beginning of each cycle, sunspots appear on the Sun in the mid-latitudes
02:44
for a brief few hours to days.
02:46
At solar minimum, there are often days without any spots at all.
02:49
As the Sun becomes more active, sunspots form closer to the equator
02:54
and can stick around for weeks to months.
02:56
These sunspot patterns give clues to what drives the solar cycle,
03:00
the twisting of the Sun's magnetic field.
03:03
Like Earth, the Sun has a magnetic field with a north and south pole.
03:07
But unlike Earth, the Sun's magnetic field becomes extremely complex.
03:12
This is because the Sun is made of plasma, a charged gas that generates electric currents.
03:17
As the Sun rotates, plasma around the equator moves faster than near the poles,
03:22
causing the magnetic fields to become stretched, elongated and then twisted.
03:26
Then kinks in the magnetic fields burst through the surface as sunspots larger than the size of Earth.
03:33
As the solar cycle unfolds, more sunspots appear and the magnetic field becomes more tangled.
03:39
At the peak of the solar cycle, the Sun's magnetic field flips.
03:43
The North Pole switches to the south and vice versa.
03:47
The cycle then ramps down, ready to start a new cycle.
03:50
Scientists can eventually see the result of this flip inside sunspots using satellites.
03:56
This black and white image of the Sun shows the magnetic field on the surface.
04:02
Most sunspots appear in pairs.
04:05
Like a magnet, one side is positive and the other is negative.
04:08
After they form, they gradually disappear again, leaving behind remnants of magnetic fields that move towards the Sun's poles.
04:16
Eventually, each pole accumulates enough magnetic fields, forcing the Sun's poles to flip at the peak of the cycle.
04:24
Then, new sunspot groups appear with the polarities in the opposite direction.
04:29
Scientists look for a consistent string of these new sunspots in order to declare the next solar cycle.
04:36
But the transition between cycles is slow and messy.
04:39
Cycles often overlap, creating freckles of old and new sunspots on the Sun at the same time.
04:45
Scientists can only determine we're in the new cycle when the number of new sunspots overtake old ones,
04:52
which can be six months to a year after the new cycle has begun.
04:56
While these spots give us a visible tracker, in recent years, scientists have discovered another signal that's hard to see from Earth.
05:04
The strength of the Sun's poles during solar minimum can help predict how active the next cycle will be.
05:11
After the poles have reversed at the peak, scientists keep a close eye on it for the next few years.
05:17
If the magnetic fields accumulated at the poles become strong during this time,
05:22
it's likely the next solar cycle will be an active one.
05:25
If the build-up is weak, the next solar cycle won't be as active.
05:30
While we use these indicators to track the Sun, predictions are still hard.
05:35
After all, we've only had detailed satellite observations of the last four solar cycles,
05:41
and scientists are still learning about what causes the Sun's cycle.
05:45
So until we piece together those missing pieces, the Sun, even with its 11-year clock, will continue to surprise us.
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