Sudden Ionospheric Disturbances (SID)

Sudden ionospheric disturbances (SID) are caused by solar flare enhanced X-rays in the 1 to 10 angstrom range. Solar flares can produce large increases of ionization in the D-region of the ionosphere over the daylit hemisphere of the Earth. SID's typically begin simultaneously or a few minutes after the start of a solar flare, and can have a time duration somewhat longer than the flare with a rise time more rapid than the decay time.Types of SIDs are SCNA--sudden cosmic noise absorption is a riometer-detected sudden daytime absorption increases; SEA--sudden enhancement of atmospherics are increases in signal strength on wideband equipment operated in the VLF, 10 to 50 KHz frequency range; SES--sudden enhancement of signal, observed on VLF frequencies in the 15 to 50 KHz range are nearly identical to SEA except that the receivers are narrow-band receivers designed to pick up man-made VLF transmission. Like SEA, signal strength increase is the SID indicator; SFD--sudden frequency deviation is the sudden increase of high frequency radiowaves which reaches a peak, and then decays back to the transmitting frequency; SPA--sudden phase anomaly is an abrupt shift in the phase of a radio signal on VLF frequencies received by ionospheric reflection; SWF--short wave fadeouts are abrupt decreases of radio signal strength observed at VLF frequencies.Tables of SIDs include the date; beginning, maximum and ending times; type of SID; importance on a scale of 1- to 3+ and the corresponding solar flare, if known.
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Distribution Formats
Distributor Distributor information not available
Dataset No POCs available for this dataset
Time Period 1958-01-01 to Present
Spatial Bounding Box Coordinates
N: 90.000000
S: -90.000000
E: 180.000000
W: -180.000000
Spatial Coverage Map
Documentation links not available.
Publication Dates
  • publication: 1958-01-01
Edition First
Dataset Progress Status Under development - data is currently in the process of being created
Data Update Frequency Monthly
Purpose Solar Disturbances Research
Use Limitations
  • 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.
  • DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
  • DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
Theme keywords NASA/GCMD Earth Science Keywords
  • EARTH SCIENCE > Sun-earth Interactions > Solar Activity > Solar Radio Waves
Uncontrolled Keywords
  • Solar Physics
  • Short Wave Fade
  • Sudden Phase Anomaly
  • Solar Flare Atmospherics
  • D Region
  • Soft X-Rays
Place keywords NASA/GCMD Location Keywords
  • Ionosphere
      Use Constraints
      • Use Constraints: None
      Access Constraints
      • Access Constraints: No Constraints
      • None
      Last Modified: 2015-09-18
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