The spectral index, α, over a given frequency range is simply the slope on a diagram of vs. .

A narrow-waveband spectral index that tracks diurnal changes in photosynthetic efficiency.

Some researchers have suggested that there is a running spectral index, but no statistically significant study has revealed one.

Note that if flux does not follow a power law in frequency, the spectral index itself is a function of frequency.

The spectral index of a source can hint at its properties.

The spectral index, n is equal to one for a scale-invariant spectrum.

This will concentrate on the three Peas' polarity and completing their spectral index.

Number of recent simulations report the spectral indices to be closer to 5/3.

There are others that report the spectral indices near 3/2.

Actually a negative spectral index of the order of 2 is required in order to maintain the solar corona.