45-Day Ap and F10.7cm Flux Forecast

The 45-day forecast product includes two forecast components issued by SWPC’s space weather forecast office:

1. The 7-day forecast of Ap and F10.7 is updated daily using the latest space weather observations.

2. The outlook for days 8 through 45 is updated weekly, on every Sunday. These long-term forecasts are based primarily on the persistence of patterns of solar and geophysical activity from one 27-day solar rotation to the next. Solar-terrestrial predictions on time scales of 27 days to several years (medium term) are less developed than short-term (days) or long-term solar cycle scale predictions. Recurrence of solar phenomena varies throughout the solar cycle, and therefore, the accuracy of these forecasts is partly a function of the strength of recurrent activity. For example, geomagnetic activity resulting from stable coronal holes is most prevalent in the declining portion of the solar cycle, and the accuracy of 45-day geomagnetic forecasts based on recurrence is better during that time. The 10.7 cm flux forecast is likely to be less accurate during the rising phase of the cycle, when there are no long-lived active regions and active Carrington longitudes have yet to form. The outlook contains predicted 10.7cm Radio Flux, planetary A index (Ap); these values are intended for guidance only.

For more information on the Ap index and F10.7 cm radio emissions, please visit:

https://www.swpc.noaa.gov/products/station-k-and-indices (under Details tab)

https://www.swpc.noaa.gov/phenomena/f107-cm-radio-emissions