Vocabulary Section
* The terms are organized alphabetically and by main topic
A. The Sun
1. Coronal Mass Ejection (CME)-
a huge release of plasma from the Sun�s corona. It can disrupt the flow of the
solar wind. One of the S/WAVES Mission�s goals is to track and measure the
extent and structure of CME�s.
2. Prominence- an eruption of plasma that extends out
in the corona and appears to be darker than the rest of the Sun. This is
because in comparison with the corona�s extremely hot plasma, prominences
contain much cooler plasma. The temperature of the Sun�s corona is approximately
2 million degree C and prominences are approximately 5000�C.
3. Solar Flares- a release of
magnetic energy from the Sun�s corona. Even though they are smaller than CME�s,
solar flares can also accelerate and eject particles into space. They are
energetic explosions that can reach temperatures from 10 or 20 million degrees
Kelvin. Solar flares are also associated with sunspots. One of the S/WAVES�
objectives is to track and probe solar flare electrons.
4. Solar wind- a constant discharge of particles
(protons and electrons) released in all directions from the upper atmosphere of
the Sun. Solar wind moves at an average speed of approximately 400km/s (in the
ecliptic plane) and it takes about 4 days to travel from the Sun to the Earth.
5. Type II radio
burst-
radio emissions produced by a fraction of the CME in the interplanetary medium
(IPM). Energized electrons from CME- driven shocks produce these radio
emissions. The further away these emissions are from the Sun, the lower their
frequency. The S/WAVES instrument measures radio sources to track the
propagation of the shocks and CMEs.
6. Type III radio
burst-
intense radio emissions produced by the acceleration of electrons during solar
flare events. S/WAVES tracks these bursts from high frequencies close to the
Sun (15MHz) to 1AU from the Sun (~30 KHz).
B. Astronomy
7. Angstroms- a very small unit of length equal to
one hundred-millionth (10) of a centimeter. Its abbreviation or symbol is �.
For example, the distance between atoms is said to be from 3 to 5 angstroms.
8. Astronomical units (AU)-
a standard unit used to measure distances within the solar system. It is the
mean distance between the Earth and the Sun. One AU is 149,597,870 kilometers,
slightly less than thedistance of 150 million
kilometers (93 million miles) identified as the value of 1AU.
C. General Science
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9. Electromagnetic
spectrum- The spectrum of waves from radio waves
to gamma rays. These waves have a dual component; they contain electric and
magnetic field oscillations. Because of this duality, electromagnetic waves can
travel without a medium and they may behave as waves or as particles (photons).
Waves in the electromagnetic spectrum are organized by their relative
wavelength and frequency. The electromagnetic wave with the lowest frequency is
the radio wave, followed by infrared, white light (combination of the colors
red, orange, yellow, green, blue, indigo and violet- each with their own
frequency range), ultraviolet, x-rays and finally, gamma rays. Notice that from
all the waves that form the electromagnetic spectrum, the only one that our
eyes can detect is white light, also called visible or optic light
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10. Electrons- negative particles that surround the
nucleus of an atom. These particles are located in different energy levels. The
further away the electrons are from the nucleus, the higher the energy level. Sometimes,
when energy is added to certain atoms, its electrons may become exited and jump
to higher energy levels.� This happens in
the Earth�s magnetosphere forming the spectacular show of the �northern lights�
or aurora borealis.
11. Frequency- is the number of waves� oscillations
that pass a fixed point per unit time. Its basic unit is Hertz (Hz)- one Hz is one cycle per second. Radio waves measured by
the S/WAVES instrument range from 10 KHz to 16 MHz.
12. In-situ measurements-
for the S/WAVES instrument, in-situ measurement refers to the waves data being collected around the STEREO spacecraft.
Such signals can come from electrons or waves moving close to the antennas.
13. Nuclear Fusion- process in which
multiple atoms combine together releasing a tremendous amount of energy. The
Sun�s energy comes form this process. Isotopes of
hydrogen collide with each other forming helium and releasing atomic particles
and energy.
14. Plasma- state of matter composed of ionized
gas. It occurs when the electrons and ions of a gas separate due to high
temperatures or other reasons.
15. Radio wave-
is an electromagnetic wave with the longest wavelength and relatively smallest
frequency of the electromagnetic spectrum. Stars, planets and many other
objects in space emit light at very large wavelengths. These long waves are in
the radio region of the electromagnetic spectrum.
16. Triangulation- is a process or technique in which the source of a radio wave can be determined by measuring the direction of the signal from two or three different points. S/WAVES uses triangulation to determine the source location of CME shocks.
17. Wavelength- is the distance between two
consecutive maximum points in a wave. The symbol for wavelength is l
and its units may vary depending on how great that distance is (mm, cm, m, km,
etc.).
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