gov.noaa.ngdc.stp.ionosonde:G10145User ServicesDOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce19580101Ionograms 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.To produce Ionograms19580101UnknownUnknownIn workdaily-18018090-90NASA/GCMD Earth Science KeywordsSun-Earth >Interactions >Solar Energetic Particle Properties >Particle Density >Electron Density height ProfileSpectral/Engineering >Radar >Radar ReflectivityNASA/GCMD Data Center KeywordsDOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of CommerceWDC/STP, BOULDER > World Data Center for Solar-Terrestrial Physics, BoulderNASA/GCMD Location KeywordsVertical Location > IonosphereRestriction Code: otherRestrictions; Use Limitation: 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.; Other: Use Constraints: None; Other: Access Constraints: None; DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of CommerceJustin Mabiephysical and mailing NOAA/NESDIS/NGDC 325 Broadway BoulderCO80305(303) 497-6135ionosonde@noaa.govUnknown 20101021Justin MabieDOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commercemailing and physical 325 Broadway, Mail Code E/GC4 BoulderCO80305-3328(303) 497-6135Justin.Mabie@noaa.govContent Standard for Digital Geospatial Metadata: Extensions for Remote Sensing MetadataFGDC-STD-012-2002