Ionosonde Stations

Metadata Updated: February 6, 2017

Ionograms are recorded tracings of reflected high frequency radio pulses generated by an ionosonde. Unique relationships exist between the sounding frequency and the ionization densities which can reflect it. As the sounder sweeps from lower to higher frequencies, the signal rises above the noise of commercial radio sources and records the return signal reflected from the different layers of the ionosphere. These echoes form characteristic patterns of "traces" that comprise the ionogram. Radio pulses travel more slowly within the ionosphere than in free space, therefore, the apparent or "virtual" height is recorded instead of a true height. For frequencies approaching the level of maximum plasma frequency in a layer, the virtual height tends to infinity, because the pulse must travel a finite distance at effectively zero speed. The frequencies at which this occurs are called the critical frequencies. Characteristic values of virtual heights (designated as h'E, h'F, and h'F2, etc.) and critical frequencies (designated as foE, foF1, and foF2, etc.) of each layer are scaled, manually or by computer, from these ionograms. Typically, an ionosonde station obtains one ionogram recording every 15 minutes. When the scaling is done manually only the hourly recordings are routinely reduced to numerical data. Modern ionosondes with computer-driven automatic scaling procedures routinely scale all the ionograms recorded. The resulting numerical values, along with the original ionograms and station reports, are archived at five World Data Centers (WDCs) for Ionosphere. The ionosphere is divided into four broad regions called D,E, F, and topside. These regions may be further divided into several regularly occurring layers, such as F1 or F2.D Region: The region between about 75 and 95km above the Earth in which the relatively weak) ionization is mainly responsible for absorption of high-frequency radio waves. E Region: The region between about 95 and 150km above the Earth that marks the height of the regular daytime E layer. Other subdivisions isolating separate layers of irregular occurrence within this region are also labeled with an E prefix, such as the thick layer, E2, and a highly variable thin layer, Sporadic E. Ions in this region are mainly O2+. F Region: The region above about 150km in which the important reflecting layer, F2, is found. Other layers within this region are also described using the prefix F, such as a temperate-latitude regular stratification, F1, and a low-latitude, semi-regular stratification, F1.5. Ions in the lower part of the F layer are mainly NO+ and are predominantly O+ in the upper part. The F layer is the region of primary interest for radio communications.

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Metadata Date September 18, 2015
Metadata Created Date September 26, 2015
Metadata Updated Date February 6, 2017
Reference Date(s) January 1, 1958 (publication)
Frequency Of Update daily

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Harvested from NOAA CSW Harvest Source

Additional Metadata

Resource Type Dataset
Metadata Date September 18, 2015
Metadata Created Date September 26, 2015
Metadata Updated Date February 6, 2017
Reference Date(s) January 1, 1958 (publication)
Responsible Party DOC/NOAA/NESDIS/NCEI > National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce (Point of Contact)
Contact Email
Access Constraints Use Constraints: None, Access Constraints: None
Bbox East Long 180
Bbox North Lat 90
Bbox South Lat -90
Bbox West Long -180
Coupled Resource
Frequency Of Update daily
Guid gov.noaa.ngdc.stp.ionosonde:G10145
Harvest Object Id 27af3013-8b9f-4fc7-a5c8-e388c547f77a
Harvest Source Id 2aed8e29-fc5b-4cde-aa66-fb1118fd705e
Harvest Source Title NOAA CSW Harvest Source
Licence While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.
Metadata Language
Metadata Type geospatial
Progress underDevelopment
Spatial Data Service Type
Spatial Reference System
Spatial Harvester True
Temporal Extent Begin 1958-01-01

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