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Eng ID Term Definition
2561
inversion layer
Atmospheric LAYER, horizontal or ap­proximately so, in which the temperature increases with increasing HEIGHT. See TEMPERATURE INVERSION.
2562
inverted compass
See COMPASS: HANGING.
2563
inverted image
See IMAGE.
2564
inverting eyepiece
See EYEPIECE: ERECTING.
2565
ionosphere
That part of the ATMOSPHERE, extending from about 70 to 500 km, in which ions and free elec­trons exist in sufficient quantities to reflect ... more
That part of the ATMOSPHERE, extending from about 70 to 500 km, in which ions and free elec­trons exist in sufficient quantities to reflect ELEC­TROMA­GNETIC WAVES.
2566
ionospheric disturbance
A sudden outburst of ul­travio­let light on the sun, known as a Solar Flare, which produces abnormally high ionization in the region of the ... more
A sudden outburst of ul­travio­let light on the sun, known as a Solar Flare, which produces abnormally high ionization in the region of the D-layer. The result is a sudden increase in radio wave absorption, with particular severity in the upper medium and lower high frequen­cies. It has negligible effects on the heights of the reflecting/­refracting layers and, consequently, upon critical frequencies, but enormous transmission may occur.
2567
ionospheric storm
Violent changes in the state of the IONOSPHERE.
2568
ionospheric wave
See WAVE: SKY.
2569
ironbound
(adj.). Said of a rugged, rocky COAST which affords no ANCHORAGE.
2570
irradiance (at a point of a surface)
Quotient of the FLUX of RADIATION incident on an infinitesimal element of surface containing the point under consideration, by the area of t... more
Quotient of the FLUX of RADIATION incident on an infinitesimal element of surface containing the point under consideration, by the area of that element.
2571
irradiation (at a point of a surface)
Product of an IRRADIANCE and its duration.
2572
irregular error
See ERROR: ACCIDENTAL.
2573
island
A piece of LAND completely surrounded by water.
2574
island harbour
See under HARBOUR.
2575
island shelf
See CONTINEN­TAL SHELF.
2576
island slope
See CONTINEN­TAL SLOPE.
2577
isle
An ISLAND. Now more usually applied to an ISLAND of smaller size, except in established appellation, as the 'British Isles'.
2578
islet
A small ISLAND.
2579
isobar
Line joining points of equal pressure on a given surface (level surface, vertical cross section, etc.).
2580
isobath
See DEPTH CURVE, FATHOM LINE.