วันศุกร์, 19 เมษายน 2024, 7:51PM
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อภิธานศัพท์: อภิธานศัพท์ฟิสิกส์ (อวกาศ)
G
GAMMA A unit of magnetic field intensity equal to 1 x 10.0E-05 GAUSS,
also equal to 1 NANOTESLA.
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GAMMA RAYS High energy radiation (energies in excess of 100 keV) observed
during large, extremely energetic solar FLARES.
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GAUSS The unit of magnetic induction in the cgs (centimeter-gram-
second) system.
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GEOMAGNETIC ELEMENTS The components of the geomagnetic field at the sur-
face of the earth. In SESC use, the northward and eastward
components are often called the H and D components, where the
D component is expressed in gammas and is derived from D (the
declination angle) using the small angle approximation.
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GEOMAGNETIC FIELD The magnetic field observed in and around the earth.
The intensity of the magnetic field at the earth's surface is
approximately 0.32 gauss at the equator and 0.62 gauss at the
north pole.
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GEOMAGNETIC STORM A worldwide disturbance of the earth's magnetic field,
distinct from regular diurnal variations.
Minor Geomagnetic Storm: A storm for which the Ap index was
greater than 29 and less than 50.
Major Geomagnetic Storm: A storm for which the Ap index was
greater than 49 and less than 100.
Severe Geomagnetic Storm: A storm for which the Ap index was
100 or more.
Initial Phase: Of a geomagnetic storm, that period when there
may be an increase of the MIDDLE-LATITUDE horizontal
intensity (H).
Main Phase: Of a geomagnetic storm, that period when the hori-
zontal magnetic field at middle latitudes is generally
decreasing.
Recovery Phase: Of a geomagnetic storm, that period when the
depressed northward field component returns to normal levels.
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GEOPHYSICAL EVENTS Flares (Importance two or larger) with Centimetric
Outbursts (maximum of the flux higher than the Quiet Sun flux,
duration longer 10 minutes) and/or strong SID. Sometimes these
flares are followed by Geomagnetic Storms or small PCA. (Class M
Flares)
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GEOSYNCHRONOUS Term applied to any equatorial satellite with an orbital
velocity equal to the rotational velocity of the earth. The net
effect is that the satellite is virtually motionless with respect
to an observer on the ground.
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GMT Greenwich Mean Time. (See COORDINATED UNIVERSAL TIME.)
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GRADUAL COMMENCEMENT The commencement of a geomagnetic storm that has
no well-defined onset.
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GRANULATION Cellular structure of the PHOTOSPHERE visible at high spatial
resolution.
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GREEN LINE The green line is one of the strongest (and first-recognized)
visible coronal lines. It identifies moderate temperature regions
of the CORONA.
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GROUND-LEVEL EVENT (GLE) A sharp increase in ground-level COSMIC RAY count
to at least 10% above background, associated with solar protons of
energies greater than 500 MeV. GLEs are relatively rare, occur-
ring only a few times each SOLAR CYCLE.
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