Though the sun lies 93 million miles (149 million km)
from Earth, its unceasing activity assures an impact on our planet far beyond
the obvious light and heat. From a constant stream of particles in the form of solar
wind to the
unpredictable bombardment from solar flares and coronal mass ejections,
Earth often feels the effects of its stellar companions. Less noticeable are
thesunspots crossing the solar surface, though
they are related to the more violent interactions. All of these fall under the
definition of "space weather."
Sunspots
Studying the surface of the sun can
reveal small, dark areas that vary in number and location. These sunspots, which tend to
cluster in bands above and below the equator, result from the interaction of
the sun's surface plasmawith its magnetic field.
Sunspots are cooler regions that cap
some of the intense energy below them. Here’s how they form:
The material at the solar equator
travels significantly faster than the material at the poles. The magnetic field
lines become warped. When the magnetic field is strong enough — and twisted
enough — jet streams of flowing currents create ropes of magnetism. Most of the
rope lays inside the sun, but part of it may break through the visible layer,
where it is viewed in the form of two sunspots. The pair are polar opposites,
literally; think of them as magnetic north and south, with the rope acting as
the magnet in between.
See how solar flares, sun storms and huge eruptions from the sun work in
this SPACE.com infographic. View the full solar storm
infographic here.
Credit: Karl Tate/SPACE.com
Credit: Karl Tate/SPACE.com
At temperatures of 3,800 kelvins,
sunspot temperatures are nearly 2,000 K less than the rest of the sun. But
don't let the numbers fool you. If a single sunspot stood alone in the night
sky, it would be ten times brighter than the full moon.
Similarly, sunspots might seem small
when compared to the 865,000-mile (1,392,000 km) diameter of the sun, because
they typically cover less than 4 percent of its visible disk. However, ranging
from 1,500 miles to 30,000 miles (2,500-50,000 km) in size, they can reach the
width of the planet Neptune, the smallest of the gas planets. But with a
lifetime of anywhere from a few days to a few weeks, sunspots are far less
permanent.
Sunspots do not appear in random
locations. They tend to be concentrated in two mid-latitude bands on either
side of the equator. They begin appearing around 25 to 30 degrees north and
south of the center. As the solar cycle progresses, new sunspots appear closer
to the equator, with the last of them appearing at an average latitude of 5 to
10 degrees. Sunspots are almost never found at latitudes greater than 70
degrees.
It takes approximately 11 years for the sun to move through the solar cyclethat is defined by an increasing
and then decreasing number of sunspots. As it reaches the close of a cycle, new
sunspots appear near the equator, while a new cycle produces sunspots in higher
latitudes. The cycles overlap; sunspots from the previous cycle can still
develop even after sunspots from the new cycle appear. So solar scientists have
a very difficult time saying exactly when one cycle ends and the next begins.
Scientists measure the activity of the
sun by keeping track of the number of sunspots appearing on its surface. Since
the invention of the telescope, sunspot counts have been relatively constant.
In 1849, astronomers at the Zurich Observatory began observing and counting
sunspots on a daily basis. The Solar
Influence Data Analysis Center in Belgium and the
U.S. National Oceanic and Atmosphere
Administration are responsible for
monitoring sunspot activity today.
This snapshot from
NASA's Solar Dynamics Observatory shows a stunning prominence associated with a
Sept. 8, 2010 solar flare.
Credit: NASA/SDO
Credit: NASA/SDO
Solar Flares
The high magnetic fields in the
sunspot-producing active regions also give rise to explosions known as solar flares. When the twisted
field lines cross and reconnect, energy explodes outward with a force exceeding
that of millions of hydrogen bombs. [The Sun's Wrath: Worst Solar
Storms in History]
Temperatures in the outer layer of the
sun, known as the corona, typically fall around a few million kelvins. As solar
flares push through the corona, they heat its gas to anywhere from 10 to 20
million K, occasionally reaching as high as a hundred million.
Because solar flares form in the same
active regions as sunspots, they are connected to these smaller, less violent
events. Flares tend to follow the same 11-year cycle. At the peak of the cycle,
several flares may occur each day, with an average lifetime of only 10 minutes.
The largest, X-class flares, have the most
significant effect on Earth. They can cause long-lasting radiation storms in
the upper atmosphere, and trigger radio blackouts. Medium-size M-class flares
can cause brief radio blackouts in the polar regions and the occasional minor
radiation storms. C-class flares have few noticeable consequences.
When the energized particles exploding
from solar flares race toward us, they arrive in only eight minutes. Astronauts
in space risk being hit by these hazardous particles, and manned missions to
the moon or Mars must take this danger into account. Everyone else is shielded by the
Earth's atmosphere and magnetic field. Sensitive electronic equipment in space
can also be damaged by these energetic particles.
Absorbing X-rays affects the atmosphere.
The increase in heat and energy result in an expansion of the Earth's
ionosphere. Man-made radio waves travel through this portion of the upper
atmosphere, so radio communications can be disturbed by its sudden
unpredictable growth. Similarly, satellites previously circling through
vacuum-free space can find themselves caught in the expanded sphere. The
resulting friction slows down their orbit, and can bring them back to Earth
sooner than intended.
Despite their size and high energy,
solar flares are almost never visible optically. The bright emission of the
surrounding photosphere, where the sun's light originates, tends to overshadow
even these explosive phenomena. Radio and optical emissions can be observed on
Earth. However, since X-rays and gamma rays fail to penetrate the atmosphere,
only space-based telescopes can detect their signatures.
This still from SDO
caught the action in freeze-frame splendor when the Sun popped off two events
at once (Jan. 28, 2011). A filament on the left side became unstable and
erupted, while an M-1 flare (mid-sized) and a coronal mass ejection on the
right blasted into space.
Credit: NASA/SDO/GSFC
Credit: NASA/SDO/GSFC
Coronal Mass Ejections
The magnetic field lines that twist up
to form solar flares occasionally become so warped that, like rubber bands
under tension, they snap and break, then reconnect at other points. The gaps
that form no longer hold the sun's plasma on its surface. Freed, the plasma
explodes into space as a coronal mass ejection (CME).
It takes several hours for the CME to
detach itself from the sun, but once it does, it races away at speeds of up to
1,000 km (more than 7 million miles per hour). The cloud of hot plasma and
charged particles may be up to a hundred billion kilograms (220 billion pounds)
in size.
The northern lights
are more formally known as auroras, and are caused by interactions between the
solar wind and the Earth's magnetic field.
Credit: Karl Tate, SPACE.com Contributor
Credit: Karl Tate, SPACE.com Contributor
As with solar flares, if the CME is
aimed in our direction, it takes the particles eight minutes to reach Earth.
However, the particles take anywhere from one to five days to travel the
distance to our planet. The solar wind, a constant stream of
charged particles ejected by the sun, acts on the cloud like a current on a
boat. Faster CMEs feel the drag of the wind and slow down, while those with low
initial velocities speed up.
- Auroras (Northern Lights): When the energy from a solar storm reaches the vicinity of Earth, charged particles in our planet’s upper atmosphere interact with air molecules to create aurora. These Northern Lights, as they are also called, can be fantastic displays of color. The solar wind also generates a near-constant but less spectacular display of aurora.
Many solar storms aren't aimed toward
us. At the high point of the solar cycle, the sun may produce as many as five
CMEs in a given day; even at the low point, it averages one a day. The
spherical shape of the sun means that most of them miss the Earth completely.
In fact, we can't even observe all of the ejections; those emerging directly
opposite our planet are undetectable.
However, when the sun does eject a cloud
of plasma and gas directly toward us, the incoming matter seems to surround the
sun. Much like a baseball falling from the direction of the sun can seem to
grow larger and dwarf the star, the so-called "halo coronal mass
ejection" can appear to overshadow its source. Such ejections cause the
most problems for the people on Earth.
Like solar flares, CMEs bring an
increase in radiation to astronauts and electronics in space. But unlike
flares, they also bring charged particles of matter that interact with the
field surrounding our planet. The results vary depending on the size, speed and
magnetic strength of the particles.
When the particles reach the Earth's
magnetic sphere, they stretch and distort. Much like a tree in a strong wind,
the day side — the first side affected — is compressed, while the night side is
stretched out like a tail. When it reconnects on the night side, it releases
the energy found in a bolt of lightning. While lightning lasts on the order of
microseconds, however, the magnetic storm created lasts far longer. It races back
toward Earth's upper atmosphere.
The sudden increase in power can damage
sensitive electronic equipment. Power transformers can overload, causing
long-lasting blackouts. Long metal structures like oil and gas pipelines can
carry currents, which can enhance their corrosion over time and lead to
devastating effects if proper safety measures are not in place. The resulting
variations in the ionosophere can disrupt GPS signals, giving inaccurate
readings.
On Feb. 13th at 1738
UT, sunspot 1158 unleashed the strongest solar flare of the year so far, an
M6.6-category X-ray irradiance magnitude blast. NASA's Solar Dynamics
Observatory recorded an intense flash of extreme ultraviolet radiation. The
source of this activity, sunspot 1158 is growing rapidly.
Credit: NASA/SDO
Credit: NASA/SDO
On Sept. 1, 1859, Richard Carrington and
Richard Hodgson, both amateur English astronomers, independently made the first
observations of a solar flare, one which resulted in the largest geomagnetic
storm ever recorded. Auroras, which normally occupy the polar regions, were
visible in tropical latitudes. Telegraph operators reported being shocked —
literally — by their instruments. Even after unhooking them from the power
supply, messages could still be transmitted, powered by the currents in the
atmosphere.
The so-called Carrington Event would be far more devastating if it happened today, given the greater
reliance on electronics and the expanded power supply. However, thus far, it is
the strongest storm yet recorded.
A ULA Atlas 5 rocket carrying NASA’s Solar Dynamics Observatory satellite
rolls out to its Space Launch Complex-41 launch pad at Cape Canaveral Air Force
Station in Fla., for a planned Feb. 10, 2010 launch.
Credit: Pat Corkery, United Launch Alliance.
Credit: Pat Corkery, United Launch Alliance.
Observing the Sun
NASA is currently implementing Project Solar Shield to provide warnings to vital systems after an Earth-affecting CME occurs.
This allows satellites and power transformers to be shut down if necessary for
a short period of time. The result is a short- term, controlled blackout rather
than a longer one caused by the destruction of vital equipment.
Similarly, several satellites keep the
entire sun under constant observation. NASA’s Solar & Heliospheric
Observatory (SOHO) spacecraft studies the sun, while the Solar Dynamic Observatory (SDO) focuses on solar atmosphere. And the Advanced Composition Explorer (ACE) samples particles from the sun as they
stream toward our planet. These programs will help bring a greater
understanding of the subject of space weather on Earth.
Questions:
1. What is Solar Flares?
a. The high magnetic fields in the sunspot-producing active regions that
also give riese to explosions
b. The high temperature fields in the sunspot-producing active regions
that also give riese to explosions
c. The high land in the sunspot-producing active regions that
also give riese to explosions
d. The high magnetic fields in the sunspot-producing active regions that
also give a massive light
e. Temperatures in the outer layer of the sun
2. Did Sunspots appear in random locations? Why?
a. Yes, because they are moving
b. Yes, because they are big
c. No, because they tend to be concentrated in two mid-latitude bands on
either side of the equator
d. No, because they are not moving
e. Yes, becuase they did not tend to be concentrated in two mid-latitude
bands on either side of the equator
3. How long for the sun to move through the solar cycle?
a. 11 years c. 9 years e. 7 years
b. 10 years d. 8 years
4. How long an average lifetime of several solar flares may occure each
day?
a. 10 minutes c. 15 minutes e. 2 minutes
b. 5 minutes d. 8 minutes
5. Whatis the name of the largest solar flares?
a. M-class c. X-class e. O-class
b. C-lass d. F-class
Questions:
1. What is Solar Flares?
a. The high magnetic fields in the sunspot-producing active regions that
also give riese to explosions
b. The high temperature fields in the sunspot-producing active regions
that also give riese to explosions
c. The high land in the sunspot-producing active regions that
also give riese to explosions
d. The high magnetic fields in the sunspot-producing active regions that
also give a massive light
e. Temperatures in the outer layer of the sun
2. Did Sunspots appear in random locations? Why?
a. Yes, because they are moving
b. Yes, because they are big
c. No, because they tend to be concentrated in two mid-latitude bands on
either side of the equator
d. No, because they are not moving
e. Yes, becuase they did not tend to be concentrated in two mid-latitude
bands on either side of the equator
3. How long for the sun to move through the solar cycle?
a. 11 years c. 9 years e. 7 years
b. 10 years d. 8 years
4. How long an average lifetime of several solar flares may occure each
day?
a. 10 minutes c. 15 minutes e. 2 minutes
b. 5 minutes d. 8 minutes
5. Whatis the name of the largest solar flares?
a. M-class c. X-class e. O-class
b. C-lass d. F-class
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