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Ionospheric scintillation is characterised by large variations in the received signal power. It is not often seen on the widebeam antenna, nor at lower time resolutions (such as 2 minutes used by the online plots). This is because wide beams and long sampling intervals both average out the variation in cosmic noise level. It is unusual to see ionospheric scintillation in the summary line plots, even though it is common in requested data. Any scintillation seen in the widebeam antenna is a clue that the ionosphere was very irregular at that time.

Scintillation is sometimes seen in the keogram plots, such as the example below.

Scintillation - keogram

The cause of ionospheric scintillation is due to irregularities in the ionosphere being illuminated by a strong point source. The irregularities act as a diffraction grating and the riometer measures large variations in signal strength, corresponding to whether the wave fronts are reinforcing or cancelling each other. At Kilpisjärvi scintillation is only usually apparent when Cassiopeia (or occasionally Cygnus) are in view.

Times when scintillation is likely can be predicted with the IRIS scintillation calculator.


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