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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|
E Layer Screening
When a radio wave directed for F region communications is instead refracted from the E region.
This is likely to occur when the take-off angles of the F mode and the E mode are similar and the
operating frequency is below the E region MUF for the E mode. The radio wave is then likely to propagate
via multiple E layer hops. The E modes can be heavily attenuated, especially when
more than two hops occur.
Electromagnetic Radiation
Radiation which has both electric and magnetic properties. Examples: microwaves,
light, infra-red, ultraviolet, X rays, gamma, radio and
television. Travels at 300 million m/s.
Electron
An atomic particle with a fixed negative electric charge.
Electron Density
The number of electrons in a unit volume, e.g., 1 cubic centimetre.
Elevation Angle
Angle between the horizontal and the direction of concern.
Equatorial Anomaly
A depression in F region frequencies at the geomagnetic equator relative to
frequencies at low latitudes. A daytime phenomenon.
Equatorial Electroject
A thin electric current in the ionosphere over the magnetic
equator around 100 to 115 km altitude normally flowing eastward during the day. The electrojet
may reverse its direction during geomagnetically disturbed conditions and
magnetically quiet times. The reversals during quiet times have been related to lunar
tides. There is a strong correlation between the electrojet and equatorial sporadic E.
Equinox
Time when the Sun crosses the geographic equator. Day and night are of equal
lengths. Occurs in March and September.
E Region
A solar controlled ionospheric region around 90-140 km capable of refracting HF radio waves.
This region is only significant for HF communications during daylight hours.
EUV Radiation
See Extreme Ultraviolet Radiation.
Extraordinary Wave
A radio wave may split into two oppositely polarised components due to, in the case
of the ionosphere, the geomagnetic field. The ordinary wave obeys the laws of
refraction and is unaffected by the magnetic field. The extraordinary wave travels
a different path through the ionosphere.
Extreme Ultraviolet Radiation
Electromagnetic radiation at the high frequency end of the ultraviolet spectrum.
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Educational