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Glossary of Solar Terrestrial Terms
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|
Ultraviolet Radiation
Radiation of immediately shorter wavelengths than visible light, between 5 and 400 nm.
Extreme ultraviolet (EUV) and X rays have shorter wavelengths again.
Universal Time
Greenwich Mean Time (GMT). Time referred to the zero meridian of
longitude (through Greenwich, UK). 0000 UT is local midnight at Greenwich. For example,
00 UT = 10 am Australian EST = 8 am Australian WST = 9.30 am Australian CST.
Upper Decile
The largest decile, one of nine, that has 90% of the ordered values below it.
Upper Decile MUF
This is a statistical prediction of the highest frequency for HF sky wave propagation.
If the prediction is correct, this frequency should be refracted by the ionosphere
10% of the time. See Maximum Usable Frequency and Optimum Working Frequency.
UT
See Universal Time.
UV
See Ultraviolet Radiation.
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Educational 
MAG: Normal
ION: Moderate