Astronomy:S4 Index

Short description: Parameter used to measure ionospheric disturbances

The [math]\displaystyle{ S_4 }[/math] Index is a standard index used to measure ionospheric disturbances. It is defined as the ratio of the standard deviation of signal intensity to the average signal intensity.

Real Time data

This parameter is displayed in real time by many institutions:

• at Arecibo Observatory
• at Cornell University
• at INPE, in Brasil