Sudden ionospheric disturbance
A sudden ionospheric disturbance (SID) is any one of several ionospheric perturbations, resulting from abnormally high ionization/
telecommunications systems.[1]
Discovery
The Dellinger effect, or sometimes Mögel–Dellinger effect, is another name for a sudden ionospheric disturbance.[2] The effect was discovered by John Howard Dellinger around 1935 and also described by the German physicist Hans Mögel (1900-1944) in 1930.[3][4] The fadeouts are characterized by sudden onset and a recovery that takes minutes or hours.
Cause
When a solar flare occurs on the
E region) immediately increase in density over the entire dayside. The ionospheric disturbance enhances VLF radio propagation. Scientists on the ground can use this enhancement to detect solar flares; by monitoring the signal strength of a distant VLF transmitter, sudden ionospheric disturbances (SIDs) are recorded and indicate when solar flares have taken place.[5] The small geomagnetic effect in the lower ionosphere appears as a small hook on magnetic records and is therefore called "geomagnetic crochet effect" or "sudden field effect".[6]
Effects on radio waves
Short wave radio waves (in the
fadeout (SWF). These fadeouts last for a few minutes to a few hours and are most severe in the equatorial regions where the Sun is most directly overhead. Although High Frequency signals suffer a fadeout because of the enhanced D-layer, the Sudden Ionospheric Disturbance enhances long wave (VLF) radio propagation. SIDs are observed and recorded by monitoring the signal strength of a distant VLF transmitter
.
A whole array of sub-classes of SIDs exist, detectable by different techniques at various wavelengths: the short-wave fadeout (SWF), the SPA (Sudden Phase Anomaly), SFD (Sudden Frequency Deviation), SCNA (Sudden Cosmic Noise Absorption), SEA (Sudden Enhancement of Atmospherics), etc.
See also
References
- ^ Federal Standard 1037C Glossary of Telecommunications Terms, http://www.its.bldrdoc.gov/fs-1037/fs-1037c.htm, retrieved 2011 Dec 15
- ISBN 978-0-86341-186-1.
- ^ Mögel, H. (1930). "Über die Beziehungen zwischen Empfangsstörungen bei Kurzwellen und den Störungen des magnetischen Feldes der Erde" [On the relations between disturbances of shortwave reception and disturbances of the Earth's magnetic field]. Telefunken Zeitung. 11: 14–31.
- ^ See:
- Dellinger, J. H. (11 October 1935). "A new cosmic phenomenon". Science. 82 (2128): 351. S2CID 239877535.
- Dellinger, J. H. (March 1937). "Sudden ionospheric disturbances". Terrestrial Magnetism and Atmospheric Electricity. 42 (1): 49–53. .
- Dellinger, John Howard (August 1937). "Sudden disturbances of the ionosphere". Journal of Research of the National Bureau of Standards. 19 (2): 111–141.
- Dellinger, J. H. (11 October 1935). "A new cosmic phenomenon". Science. 82 (2128): 351.
- ^ AAVSO: SIDs – Sudden Ionospheric Disturbances
- ISBN 978-3-642-46082-1)
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