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Solar Flux Index (SFI)
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The flux density of radio emissions from the Sun has been measured at a frequency of 2800 MHz since approximatey 1950. This solar flux measurement is referred to as F10.7, because 2800 MHz corresponds to a wavelength of 10.7 cm. F10.7 is strongly correlated with the amount of UV radiation coming from the Sun, but can be measured on the ground, as opposed to UV measurements which must be measured from space, above the absorption of the Earth's atmosphere. Making accurate long-term ground-based radio measurements is more reliable and less costly than producing long-term space-based UV measurements.
The amount of solar UV energy, as traced by F10.7, is an important assessment of ionization in the Earth's ionosphere, which in turn has a major impact on radio communications on Earth. F10.7 can also be used to study solar storms, which can produce major disruptions to satellite systems and terrestrial power grids.
F10.7 has always been measured by Canadian radio astronomy stations. It is presently produced by the Dominion Radio Astrophysical Observatory (DRAO) near Penticton, British Columbia.
F10.7, also called the Solar Flux Index (SFI), is measured in a 100 MHz bandwidth from 2750-2850 MHz. It is in units of 10^-22 W/m^2/Hz.
A good article on measurement of the Solar Flux Index appeared in the February 2013 issue of QST magazine.
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Frequency Bands |
| Band | Use | Service11 | Table |
| 2750 - 2850 MHz | Solar Flux Index (SFI) | Radio Astronomy | - |
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