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The region in which a particular type of force can be observed; depending on the force, one can thus speak of a gravity field, magnetic field, electric field (or when the two are linked by fast oscillations, electromagnetic field) and nuclear field. The laws of physics suggest that fields represent more than a possibility of force being observed, but that they can also transmit energy and momentum, e.g. a light wave is a phenomenon completely defined by fields. For that reason a field is often viewed as a space which was modified by the sources of the force which the field represents.
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A property of an ideal plasma, well approximated in real plasmas, characterizing the way the flow of plasma may deform the magnetic field in which it is embedded. The law of preservation states, "If two particles in a flowing plasma are initially on the same magnetic field line, they continue doing so in the future."
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The celestial sphere and the collection of stars whose position is fixed on it.
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Another name for the position on the celestial sphere of the vernal equinox. It is called so because in ancient time that point was in Aries, a constellation of the zodiac. It is currently moving from Pisces to Aquarius.
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a rapid outburst on the Sun, usually in the vicinity of active sunspots. A sudden brightening (only rarely seen without special filters, isolating the red light of hydrogen) may be followed by the signatures of particle acceleration to high energies--x-rays, radio noise and often, a bit later, the arrival of high-energy ions from the Sun. Flares appear to be associated with rapid energy releases high above the photosphere, apparently from the magnetic fields of sunspots. Their link to coronal mass ejections, which may also be powered by magnetic energy, is still unclear.
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another name for (planetary or lunar) "gravity assist" or "swing-by" maneuver.
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In mechanics, the cause of motion. It is a vector quantity, in the direction of the acceleration it causes.
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The system of coordinates (and the objects that determine it) in which motion or any physical effects are calculated or measures. Einstein's principle of relativity states that the laws of physics are exactly the same in two frames of reference moving with constant velocity along a straight line relative to each other.
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(Often denoted by n, the Greek letter letter nu.) --the number of back-and-forth cycles per second, in a wave or wave-like process. Expressed this way, the frequency is said to be given in units of Hertz (Hz), named after the scientist who first produced and observed radio waves in the lab. Alternating current in homes in the US goes through 60 cycles each second, hence its frequency is 60 Hz; in Europe it is 50 cycles and 50 Hz.
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