📘 Definition
The F10.7 solar flux is a measure of solar radio emission at a wavelength of 10.7 cm (2,800 MHz), measured in solar flux units (SFU, 1 SFU = 10⁻²² W/m²/Hz). It serves as the primary proxy for solar extreme ultraviolet (EUV) radiation, which heats and expands Earth's upper atmosphere. Higher F10.7 values → hotter, more expanded thermosphere → greater drag on LEO satellites → faster orbital decay. During solar maximum, F10.7 can exceed 200 SFU; during solar minimum, it drops to 65–70 SFU. This index is a critical input to atmospheric density models used by satellite operators.
65–70 SFU
Solar Minimum
150–250+ SFU
Solar Maximum
2,800 MHz (10.7 cm)
Frequency
Atmospheric expansion → drag
Impact