Ionospheric Summary and Forecast

Ionospheric Summary

(last updated 19 Dec 2025 23:30 UT)

Date T index 19 Dec 91 Observed Australian Regional MUFs Cocos Island Region: Depressed by 40% during local day. Depressed by 20% during local night. Niue Island Region: Mostly near predicted monthly values. Enhanced by 20% after local dawn. Northern Australian Region: Near predicted monthly values. Southern Australian Region: Near predicted monthly values. Antarctic Region (Casey/Davis/Mawson): Near predicted monthly values over the UT day. Monthly T index: Month T index Nov 103 Dec 89 Jan 89

Ionospheric Forecast

(last updated 19 Dec 2025 23:30 UT)

Date T index MUFs 20 Dec 95 Near predicted monthly values 21 Dec 90 Near predicted monthly values 22 Dec 75 About 10-15% below predicted monthly values COMMENT: Maximum usable frequencies (MUFs) were largely near predicted values during UT day 19-Dec, with the exception of the Cocos Islands, where depressions of 20-40% were observed. Low frequency sporadic-E was observed, with spread F also observed in the southern Australian region during local night hours. MUFs are forecast to be near monthly predicted values throughout 20-21 Dec, declining to be 10-15% depressed on 22-Dec as high-speed wind stream effects from an equatorial coronal hole commence. Sporadic-E during local night hours may also be observed.