PROPAGATION
As this column goes to press, it is safe to say that the Sun’s sunspot activity is increasing. Space weather scientists are making an assessment of Sunspot Cycle 25 and they say it appears to be moving more quickly toward a solar cycle maximum, as the numbers reveal that the activity level is moving higher than the current forecast.
The current solar prediction is now updated each month using historical data as well as the latest month’s observed solar indices to provide estimates for the rest of the current solar cycle and the next. These predictions are made by the Space Environments Team in the Natural Environments Branch of the Engineering Directorate at Marshall Space Flight Center (MSFC). Their forecast provides solar cycle predictions for NASA engineering programs and the aerospace community.
The updated forecast provides future statistical estimates of sunspot number, solar radio 10.7-cm flux (F10.7), and the geomagnetic planetary index, Ap, for many groups that have use of this space weather data. Some use these numbers for input to various space environment models. HF radio communicators — including the amateur radio community — use the sunspot count, the F10.7, and the Ap as inputs to VOA-CAP computer models used for planning and analyzing the radio propagation paths that use the ionosphere for DXing.
The forecasted solar indices represent the 13-month smoothed values consisting of a best estimate value stated as a 50-percentile value along with the 95-and 5-percentile statistical values. The F10.7 prediction also includes a 75-percentile value. The estimation technique is used to predict the remainder of the current cycle, but it is not able to predict the next solar cycle at this time.
The period when. The most recent solar minimum was between the last solar cycle, numbered 24 since these cycles have been recorded, and the current Solar Cycle 25. The last solar minimum period happened in December 2019, when the 13-month smoothed sunspot number fell to 1.8, according to the Solar Cycle 25 Prediction Panel, co-chaired by NOAA and NASA. The panel now expects peak sunspot activity in 2025.
