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A | B | C | D | E | F | G | H | I |
J | K | L | M
N | O | P |
Q | R | S |
T | U | V | W | X |
Y | Z
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A
angstrom: A
unit of length equal to one hundred-millionth
of a centimeter.
active
region: An
area of the solar atmosphere where
the Sun’s magnetic field is
concentrated. The concentration
and bipolar nature 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.
aurora: Light
radiated by ions and atoms in the
Earth’s upper atmosphere,
mostly in polar regions, the result
of bombardment by energetic electrically
charged particles from the ionosphere
and magnetosphere.
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B
bow
shock: The shock
wave that flanks the magnetosphere on the day
side. It causes the solar wind flow to slow
down and flow around the magnetosphere.
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C
chromosphere: The
part of the Sun's (or another star's) atmosphere
between the photosphere and the corona.
convection: Circulation
of a fluid or gas.
corona: The
Sun’s outer atmosphere, with a temperature
of greater than a million degrees, that gives
rise to the solar wind.
coronal
mass ejection: A
vast magnetic blob of plasma that
erupts from the Sun's corona and
travels through space at high speed.
Coronal mass ejections may cause
intense geomagnetic storms when they
strike the Earth and accelerate vast
quantities of energetic particles
in both interplanetary space and
the magnetosphere.
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D
disk: The
visible surface of the Sun projected against the sky.
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E
extreme
ultraviolet: Electromagnetic
radiation, invisible to the naked eye, with wavelengths
shorter than ultraviolet radiation and longer than
x-rays. These wavelengths are mainly responsible
for the existence of the ionosphere.
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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.
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
charged particles (ions and electrons)
and all forms of electromagnetic radiation
into space.
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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 the most
energetic flares on the solar surface.
gauss: A
unit of magnetic field strength.
geomagnetic
field: The
Earth’s magnetic field.
geomagnetic
storm: A
worldwide large disturbance in the Earth’s
magnetic field, accompanied by intense
auroras in the northern and southern
polar regions and intensifications of
the particle radiation trapped in Earth's
magnetosphere (the Van Allen belts).
granulation: The
cellular structure of the photosphere. "Granules" are
formed by convection, each
one is quite large, about 700 to
1000 km (400 - 600 miles) in diameter.
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H
heliopause: The
outer edge of the heliosphere, where the solar
wind runs into the interstellar medium. At the
heliopause, the pressure of the solar wind balances
that of the interstellar medium.
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I
infrared
radiation: Electromagnetic
radiation, invisible to the naked eye, with
wavelengths longer than visible light and shorter
than microwaves.
interstellar
Medium: Electrified
gas and dust between the stars.
ionosphere: The
highest region of the Earth’s
atmosphere containing free electrons
and ions.
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K
Kelvin
(K): A unit of temperature
with a magnitude equal to that of the degree Celsius,
and based on a scale in which 0 K is absolute zero
(-273.15 °C). A temperature expressed in Kelvins
is equal to the Celsius temperature minus 273.15.
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L
limb: The
edge of the Sun or planet visible to an observer
or instrument.
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M
magnetic
field: A map of
the direction and strength of magnetic forces
around any object (such as the Sun or planet)
that is magnetic. Magnetic fields are caused
by electric currents in the Sun.
magnetometer: A
device used to measure the magnetic
fields in space and on the ground,
and its changes. For example, a magnetometer
can measure changes caused by solar
storms.
magnetopause: The
boundary of the magnetosphere, lying inside
the bow shock, usually about 10 Earth radii
toward the Sun. The solar wind is deflected
inside the bow shock to flow around the magnetopause
in the magnetosheath.
magnetosheath: The
region between the bow shock and the magnetopause,
characterized by very turbulent plasma. For
Earth, along the Sun-Earth axis, the magnetosheath
is about two Earth radii thick.
magnetosphere: The
region surrounding a planet within which
the planetary magnetic field is the dominant
force on electrically charged particles
that can be trapped within the magnetosphere,
making radiation belts like Earth's Van
Allen belts.
magnetotail: A
comet-like extension of a planet’s
magnetosphere formed on the planet’s
dark night side by the interaction of the
solar wind and the magnetosphere. It can
extend hundreds of planetary radii away
from the Sun.
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N
noctilucent
clouds: Clouds
formed at extremely high-altitude that shine
at night. A bit of a mystery, scientists aren't
sure why or how they are formed.
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P
penumbra: A
dark region that surrounds an even darker central
area of a sunspot.
photosphere: The
visible portion of the Sun.
plage: Bright
regions of gases with concentrated
magnetic fields in the solar chromosphere.
They appear near groups of sunspots and
in the regions surrounding sunspots
that are about to emerge.
plasma: A
low-density gas in which the individual
particles are charged and which contains
an equal number of positively charged
ions and negatively charged electrons.
plasmasphere: A
region of the inner magnetosphere that
contains relatively cool (low energy) and dense
plasma. This area can be considered an outer extension
of the ionosphere.
prominence: Complex
structures of relatively cool, dense
solar material that extend into the
outer chromosphere and inner corona.
They are generally static and believed
to be supported by magnetic forces.
They can appear as loops on the edge
of the solar disk or limb. Their shape
is probably controlled by the Sun's
magnetic field. Sometimes they erupt,
often in association with coronal mass
ejections.
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R
radiation: Radiation
has two different meanings. One is the stream of
particles emitted by decaying nuclei such as uranium.
This energy often takes the form of alpha or beta
particles, or neutrons. A second use is as part
of the term “electromagnetic radiation," which
refers to energy traveling in the form of electromagnetic
waves or photons. For example, yellow light is
a form of electromagnetic radiation, as are radio
waves and x-rays.
radiation
belts: Regions of of
high-energy particles traped by the magnetic influence
of the Earth. These belts are sometimes called "Van
Allen" belts because of their discovery in 1958
by Professor J.A. Van Allen. Radiation belts are
composed of electrons, protons, and smaller numbers
of other ions.
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S
solar
activity: Activity
of sunspots, flares and CME's which follow
the solar cycle.
solar
cycle: A
predictable 11-year cycle when
defined by solar activity, including
the number of sunspots, flares,
and CMEs, which follow this cycle.
When defined by the solar magnetic
field directions, the cycle is
22 years long.
solar
flare: An
explosive release of energy of the
Sun.
solar
maximum: A
period of increased solar activity
when the number of sunspots reaches
a maximum in the 11-year solar cycle.
solar
minimum: A
period of decreased solar activity
when the number of sunspots reaches
a minimum in the 11-year solar cycle.
solar
wind: The
charged particles (plasma), primarily
protons and electrons, that are continuously
emitted from the Sun and stream outward
throughout the solar system at speeds
of hundreds of kilometers per second.
sunspot: A
region of the solar surface that is
dark and relatively cool; it has an
extremely high magnetic field.
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U
ultraviolet
radiation: Electromagnetic
radiation, invisible to the naked eye, with
wavelengths shorter than violet light and longer
than x-rays.
umbra: The
dark central area of a sunspot.
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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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X
x-rays: High-energy
electromagnetic radiation, invisible to the naked
eye, with wavelengths shorter than ultraviolet
radiation and longer than gamma rays. |
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