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Vertical Soundings (Ionograms) 


Definition of Structure


Ionospheric Related Models

Ionospheric Indices (defined)

Scintillation Predictions

HF Radio Interest

Forecasting Ionospheric Real-time Scintillation (FIRST) Tool


By monitoring the height rise of the equatorial ionospheric F layer near dusk, an evening equatorial scintillation forecast is possible. Previous studies established a relationship between the Pre-Reversal Enhancement (PRE) vertical ExB drift and the scintillation S4 index. The FIRST technique extends this understanding by establishing a relationship between the readily available ionosonde produced h'F characteristic and ExB drift. h'F is defined as the minimum height of the ionospheric F layer Ordinary mode trace. With this new relationship in hand, an evening forecast is made possible. NGDC's Mirrion ionosonde measurement processing system provides real time data to support FIRST. At present, FIRST includes a forecast for the regions near Jicamarca and Kwajalein. Other longitudes are presently under pursuit. The FIRST technique is most directly related to scintillation in the VHF band.

The forecasts above display the h’F-observed values for the Jicamarca (left) and Kwajalein (right) regions for local times between 18:30 and 19:30 LT (near sunset) for the most recent 7 days. The h’F values are coded “Red”, “Yellow” or “Green” depending on whether the F region is "likely", "potentially", or "unlikely" to be unstable, respectively. A blue “N/A” indicates that data was not available near the local time in question, while a “*” next to a forecast value indicates that interpolation between two neighboring observation times was performed to yield a uniform forecast time. Quality control in an operational environment is accomplished by providing the user with both an automatic quality assessment and manual tools. The Qualscan algorithm (McNamara, 2006) provides an automatic qualifier by looking for specific anomalies caused by the Automatic Real-Time Ionogram Scaler with True height (ARTIST). Forecasts using suspicious data are labeled with a grey background. When available, a hypertext internet link to the original ionogram interpretation and the resultant electron density profile is provided for each observation time. The operational user can use these tools to manually qualify the forecast and can use post sunset ionogram images at later times to monitor the F-region response to a disturbed evening.

The technique employed represents an active area of research and can be utilized to enhance the usual suite of forecaster tools.

Future work:

  • Acquire additional, real-time, equatorial h’F values at other longitudes, e.g. Brazilian, Indian and African sectors
  • Theoretically examine, the R-T growth rates and threshold h’F (1930 LT) values as a function of solar cycle activity by incorporating a suite of first-principle models of the ambient ionosphere (PBMOD) developed at the Air Force Research Lab (AFRL)


  • Redmon, R., Anderson, D., Caton, R., Bullett, T. (2010), A Forecasting Ionospheric Real-time Scintillation Tool (FIRST), Space Weather, (in press).
  • McNamara, L. F. (2006), Quality figures and error bars for autoscaled Digisonde vertical incidence ionograms, Radio Sci., 41, RS4011, doi:10.1029/2005RS003440.

Contact: This service is maintained by Rob Redmon and you may use the email at the bottom right to send feedback or questions.