[ntp:questions] GPS and the December 5/6 Solar Flare

David J Taylor david-taylor at blueyonder.not-this-bit.nor-this-part.co.uk
Sat Apr 7 08:38:12 UTC 2007

Eugen COCA wrote:
> Other data available on this subject at:
> http://gps.ece.cornell.edu/spaceweather.html

Thanks for that pointer.  I do wonder slightly about these results.  They 

"The S4 index is quite high indicating the rapid variations of the signal 
power caused by the solar radio burst. The S4 index is NOT high because of 
ionospheric irregularities causing diffraction/refraction of the GPS 

However, they seem to be measuring S/N, and elsewhere on that page they 
show that the noise alone increased greatly.  So I don't quite see why 
they are saying the satellite output power was less, when the decreased 
S/N could simply have been due to increased noise (such as happens in 
spring and autumn with Ku-band domestic TV at 11GHz when the sun passes 
behind the satellite).

Perhaps they are actually saying "noise varies", although they say "signal 
power varies".  At least, that's the way I read it!


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