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A
Active region: An area
of the solar atmosphere where the sun’s magnetic
field is both concentrated and contorted. The contortion
of the magnetic field results in the formation of dark
areas such as sunspots and bright
areas known as faculae . These
regions also produce flares and
plages .
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Aurora: Luminous and colorful
"curtains of light" typically seen in the
night skies of the high northern and southern latitudes.
During times of increased solar activity, they can be
seen at much lower latitudes. The aurora is produced
when electrons from the sun’s solar
wind disturb the earth’s magnetic field and
interact with molecules in the earth’s upper atmosphere.
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Aurora Australis: The
aurora in the southern hemisphere, also known as the
southern lights. THE
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Aurora Borealis:
The aurora in the northern hemisphere, also known as
the northern lights. (TOP
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Auroral Oval: From space,
the auroral zone looks like a donut of light hovering
over the north and south poles. This auroral oval can
easily be seen in satellite images, and its brightness
and size changes with the level of solar activity. (TOP
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C
Chromosphere: The
layer of the solar atmosphere immediately above the
visible surface of the sun with flame-like structures
called "spicules." The chromosphere extends
a few thousand kilometers above the sun’s surface.
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Corona: The outermost layer
of the sun’s atmosphere, which extends more than
two million kilometers above the sun’s visible
surface. The appearance and shape of the corona varies
with the sun’s activity cycle. The corona is most
prominent when the number of sunspots reaches a maximum
in the solar cycle. (TOP
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Coronal mass ejection:
Magnetic field lines within the sun’s corona that spread out into space, away from the sun.
The result is a region where streams of atomic particles
can follow the magnetic field and accelerate into space.
These streams are collectively called the solar
wind. (TOP
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E
Extreme ultraviolet:
Electromagmetic radiation, invisible to the naked eye,
with wavelengths shorter than ultraviolet radiation
and longer than X rays. (TOP
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F
Facula: Brighter-than-average
regions on the sun’s surface that typically appear
near a group of sunspots just before the sunspots themselves appear. (TOP
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Flare: A sudden outburst of
energy from the sun that occurs near concentrated magnetic
fields (known as active regions ) on the sun’s visible surface. Flares emit
high-energy atomic particles and all forms of electromagnetic
radiation into space. (TOP
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G
Gamma rays: High-energy
electromagnetic radiation, invisible to the naked eye,
with wavelengths shorter than X-rays. Gamma rays are
emitted from the sun during large eruptions on the solar
surface. (TOP
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Gauss: A unit of magnetic
field strength. (TOP
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Geomagnetic field: The
earth’s magnetic field. (TOP
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Geomagnetic storm:
A worldwide disturbance in the earth’s magnetic
field. (TOP OF
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I
Infrared radiation: Electromagnetic
radiation, invisible to the naked eye, with wavelengths
longer than visible light and shorter than microwaves.
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Ionosphere: The part
of the earth's atmosphere extending from 50 kilometers
above the surface to about 1000 kilometers, and consisting
of ionized gases. The aurora is produced when electrons
from the sun's solar wind disturb
the earth's magnetic field and interact with molecules
in the ionosphere. (TOP OF THE PAGE)
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L
Limb: The edge of the sun
or planet visible to an observer or instrument. (TOP
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M
Magnetic field: A map
of the magnetic forces around any object (such as the
sun or planet) that is magnetic. The map is created
by measuring the influence of the field on a small magnetic
compass. (TOP
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Magnetosphere: The
region around an astronomical object (like a sun or
planet) where the motion of charged atomic particles
is influenced by the shape, strength, and direction
of the object’s magnetic
field . (TOP
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P
Penumbra: A dark region
that surrounds an even darker central area of a sunspot.
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Plage: Bright regions of
gases heated by concentrated magnetic fields in the
solar chromosphere during
the sun’s active periods. They appear near groups
of sunspots just before the
sunspots emerge. (TOP
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Prominence: Eruptions
of clouds of solar material that extend into the outer
chromosphere and inner corona . They can
appear as loops (when they follow the sun’s magnetic
field ) or as sprays (when ejected by the sun’s
magnetic field ).
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S
Solar cycle: An 11-year
cycle during which the number of sunspots varies predictably.
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Solar flare. See Flare
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Solar maximum: A
period of increased solar activity when the number of
sunspots reaches a maximum in the 11-year solar cycle.
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Solar minimum: A
period of decreased solar activity when the number of
sunspots reaches a minimum in the 11-year solar cycle.
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Solar wind: The
outward flow of charged particles from the sun into
space. (TOP OF
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Sunspot: Cooler,
darker area on the sun’s surface thought to be
caused by concentrated, contorted magnetic fields that
suppress convection of hot matter from the sun’s
core. (TOP OF
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U
Ultraviolet radiation: Electromagmetic
radiation, invisible to the naked eye, with wavelengths
shorter than violet light and longer than X
rays. (TOP
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Umbra: The dark central
area of a sunspot.
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X
X rays: High-energy electromagnetic
radiation, invisible to the naked eye, with wavelengths
shorter than ultraviolet radiation and longer than gamma
rays and cosmic rays. (TOP
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W
White light: Electromagnetic
radiation composed of all wavelengths of light that
is visible to the naked eye (red through violet).
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