and Filaments appear as dark filamentary objects on the solar disk (filaments)
and as protuberances on the edge of the solar disk (prominences). They generally
sit above magnetic neutral lines, outlining the demarcation of negative and
positive magnetic fields on the Sun's surface.
are formed in magnetic loops that hold relatively cool, dense gas suspended
above the surface of the Sun.
A huge solar
prominence erupted on Dec 6, 2010. This movie shows "cool" solar plasma
(60,000-80,000 K, seen in He II 30.4 nm) in red and hot plasma (almost 1 million
K, Fe IX 17.1 nm) in yellow, observed with the AIA instrument on SDO.
generally less violent than solar flares. They are cool sheets of gas that
condense out of the corona above the active regions. Some are quiet and hang
there for weeks, others rain matter down on the photosphere, still others
literally explode into space, pushing the corona out in front of them in a great
burst that carries the gas off the sun altogether."
prominences can sometimes be seen looming just beyond the edge of the sun.
A solar prominence is a cloud of solar gas held just above the surface by
the Sun's magnetic field. The Earth would easily fit below the prominence
on the left. A quiescent prominence typically lasts about a month, and may
erupt in a Coronal Mass Ejection (CME) expelling hot gas into the Solar
System. Although very hot, prominences typically appear dark when viewed
against the Sun, since they are slightly cooler than the surface.
The solar corona is constantly
losing particles. Protons and electrons evaporate off the sun, and reach the
earth at velocities of 500 km/s. Most of the mass of the sun is held in by
magnetic fields in the corona, but particles slip through occasional holes in
the fields. Solar wind affects the magnetic fields of all the planets in the
When the solar wind hits the
Earth's magnetic field, the wind compresses the field and creates a shock wave
called the Bow shock.
Earth's magnetic field
Closer to the
Earth are the Van Allen radiation belts where solar particles are trapped
due to magnetic forces.
James Alfred Van
Allen (September 7, 1914 – August 9, 2006) was an American space scientist at
the University of Iowa. The Van Allen radiation belts were named after him,
following the 1958 satellite missions (Explorer I and Explorer III) in which Van
Allen had argued that a Geiger counter should be used to detect charged
James Alfred Van Allen
Still closer are huge rings of
electric current around the poles, formed by the influence of the solar wind on
the magnetic field.Earth, Jupiter, Saturn, Uranus, and Neptune have magnetotails
where the wind extends their magnetic field.
The heliopause is the boundary
where the sun's solar wind hits the gasses of interstellar space. The sun's
particles flow at least to Neptune, and probably farther.
In the corona, above sunspots and
areas of complex magnetic field patterns, are solar flares. These sparks of
energy sometimes reach the size of the Earth and can last for up to several
hours. Their temperature has been recorded at 11 million K (20 million
degrees F). The extreme heat produces x rays that create light when they hit
the gasses of the corona.
Schematic diagram of a solar flare. Red and blue lines represent magnetic
fields, carrying solar material off the surface. Flares occur when these field
lines meet and "reconnect", producing huge explosions, and heating and
acceleration of solar material. Credit: NASA Marshall Space Flight Center.
NASA SOHO Image
Solar flares are intense, temporary releases of energy. They are seen at
ground-based observatories as bright areas on the Sun in optical wavelengths and
as bursts of noise at radio wavelengths; they can last from minutes to hours.
The primary energy source for flares appears to be the tearing and reconnection
of strong magnetic fields. They radiate throughout the electromagnetic spectrum
through visible light out to kilometer-long radio waves.
Massive Solar Storms Video From The National Geographic
A flare is defined as a sudden, rapid, and intense variation in brightness. A
solar flare occurs when magnetic energy that has built up in the solar
atmosphere is suddenly released. Radiation is emitted across virtually the
entire electromagnetic spectrum, from radio waves at the long wavelength end,
through optical emission to x-rays and gamma rays at the short wavelength end.
The amount of energy released is the equivalent of millions of 100-megaton
hydrogen bombs exploding at the same time.
This "lightbulb" Coronal Mass Ejection (CME) shows the three classical parts of
a CME: leading edge, void, and core. Taken on February 27, 2000 by the LASCO C3
As the magnetic energy is being released, particles, including electrons,
protons, and heavy nuclei, are heated and accelerated in the solar atmosphere.
The energy released during a flare is typically on the order of 1027 ergs per
second. Large flares can emit up to 1032 ergs of energy. This energy is ten
million times greater than the energy released from a volcanic explosion. On the
other hand, it is less than one-tenth of the total energy emitted by the Sun
every second. There are typically three stages to a solar flare. First is the
precursor stage, where the release of magnetic energy is triggered. Soft x-ray
emission is detected in this stage. In the second or impulsive stage, protons
and electrons are accelerated to energies exceeding 1 MeV. During the impulsive
stage, radio waves, hard x-rays, and gamma rays are emitted. The gradual build
up and decay of soft x-rays can be detected in the third, decay stage. The
duration of these stages can be as short as a few seconds or as long as an hour.
Solar flares extend out to the layer of the Sun called the corona. The corona is
the outermost atmosphere of the Sun, consisting of highly rarefied gas. This gas
normally has a temperature of a few million degrees Kelvin. Inside a flare, the
temperature typically reaches 10 or 20 million degrees Kelvin, and can be as
high as 100 million degrees Kelvin. The corona is visible in soft x-rays, as in
the above image. Notice that the corona is not uniformly bright, but is
concentrated around the solar equator in loop-shaped features. These bright
loops are located within and connect areas of strong magnetic field called
active regions. Sunspots are located within these active regions. Solar flares
occur in active regions. The frequency of flares coincides with the Sun's eleven
year cycle. When the solar cycle is at a minimum, active regions are small and
rare and few solar flares are detected. These increase in number as the Sun
approaches the maximum part of its cycle.
The Classification of Solar Flares
A solar flare is an explosion
on the Sun that happens when energy stored in twisted magnetic fields (usually
above sunspots) is suddenly released. Flares produce a burst of radiation across
the electromagnetic spectrum, from radio waves to x-rays and gamma-rays.
Scientists classify solar flares
according to their x-ray brightness in the wavelength range 1 to 8 Angstroms.
There are 3 categories: X-class flares are big; they are major events
that can trigger planet-wide radio blackouts and long-lasting radiation storms.
M-class flares are medium-sized; they can cause brief radio blackouts that
affect Earth's polar regions. Minor radiation storms sometimes follow an M-class
flare. Compared to X- and M-class events, C-class flares are small with
few noticeable consequences here on Earth.
Each category for x-ray flares
has nine subdivisions ranging from, e.g., C1 to C9, M1 to M9, and X1 to
X9. In this figure, the three indicated flares registered (from left to right)
X2, M5, and X6.
Peak (W/m2)between 1 and 8 Angstroms
I < 10-6
< = I < 10-5
< = I < 10-4
I > = 10-4
Coronal Mass Ejections
Lasco C3 Full Halo Coronal Mass Ejection June 6 2000
The outer solar atmosphere, the corona, is structured by strong magnetic fields.
Where these fields are closed, often above sunspot groups, the confined solar
atmosphere can suddenly and violently release bubbles or tongues of gas and
magnetic fields called coronal mass ejections.
This fiery Coronal Mass Ejection (CME) shows stunning details in the ejected
material. Taken by LASCO C2 on January 4, 2002. In coronagraph images,
direct sunlight is blocked by an occulter, revealing the surrounding faint
corona. The approximate size of the Sun is represented by the white
A large CME can contain 10.0E16 grams (a billion tons) of matter that can be
accelerated to several million miles per hour in a spectacular explosion. Solar
material streaks out through the interplanetary medium, impacting any planets or
spacecraft in its path. CMEs are often associated with major solar flares.
Usually, the CMEs which cause the Earth the most trouble are indeed those
associated with solar flares. The others occur with filament eruptions.
SOHO depiction of a Magnetic Storm caused by a solar flare
SOHO is a project between The European Space Agency and NASA
A sequence of LASCO C2 images showing the evolution of a Coronal Mass
Ejection over a time span of about an hour
NASA: The Mystery of the Aurora
People in the Northern Hemisphere have particular reason to keep an eye on the
sun, both because of geography and geology. The region is relatively close to
the magnetic North Pole, where solar disturbances often enter the Earth's
atmosphere, and the granite bedrock below readily conducts surges of
Though NASA scientists say the solar maximum this cycle may be more potent
as the last one, society is more vulnerable to damage today because so much more
technology orbits the Earth. Hundreds of
satellites, most of them used for telecommunications, have been launched since
Geomagnetic Substorm over Asia NASA Polar Satellite image
In a worst-case scenario, they say solar storms could knock out all
high-frequency radio on the sunlit side of the Earth or expose airplane
passengers in northern latitudes (near the North Pole) to the equivalent of 100
Data compiled from The
British Antarctic Study, NASA, Environment Canada, UNEP, EPA and
other sources as stated and credited Researched by Charles
Welch-Updated daily This Website is a project of the The Ozooe Hole