Amateur ExtraE3C10
What does the 304A solar parameter measure?
B
Answer
Radio wave propagation
Type
A
The ratio of X-ray flux to radio flux, correlated to sunspot number
B
UV emissions at 304 angstroms, correlated to the solar flux index
C
The solar wind velocity at an angle of 304 degrees from the solar equator, correlated to geomagnetic storms
D
The solar emission at 304 GHz, correlated to X-ray flare levels
Answer Notes
The 304A parameter refers to the measurement of extreme ultraviolet (EUV) light emitted by ionized helium in the sun's chromosphere at a specific wavelength of 304 angstroms. This particular UV emission is highly correlated with the Solar Flux Index (SFI) and is a primary driver of ionization in the F layer of Earth's ionosphere.
Distractors often try to confuse the number 304 with an angle for solar wind, a ratio, or a radio frequency like 304 GHz. Recognizing that the 'A' stands for Angstroms—a unit of length used to measure the wavelength of light—will lead you straight to the correct answer.
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