A sensor transmitting radiation and receiving reflections in the radio or microwave regions of the electromagnetic spectrum; in glaciological applications, either an imaging radar or a radar configure
d as a scatterometer or radar altimeter. Frequencies from about 12 mhz up to about 15 ghz have various applications in the study of mass balance with Active-microwave sensors.
Permanently frozen ground (permafrost) which, after thawing by artificial or unusual natural means, reverts to permafrost under normal climatic conditions; opposed to passive permafrost.
A localized, transient volume of the solar atmosphere in which plages, sunspots, faculae, flares, etc., may be observed. Active regions are the result of enhanced magnetic fields; they are bipolar and
may be complex if the region contains two or more bipolar groups.
A disturbed volume of the Sun's atmosphere that often consists of (from bottom to top) sunspots, plage, prominences, and hot magnetized loops. Active regions may release significant amounts of energy
during magnetic eruptions that produce coronal mass ejections and/or flares.
A mass of rock fragments and finer material, generally on a slope, that contains either an Ice core or interstitial Ice, and shows evidence of on-going movement. Active Rock Glaciers possess steep fro
nts with slope angles that approach or exceed the angle of repose.