130308 Io-B - ionospheric electron concentration change rate from Mount 2013 04 09 publication

I analyze Mount's published spectrum and measure:

Drift rate ~  -1.4E-3 MHz/s at 21 MHz on 130308 0130 UTC
Relative drift rate = -6.7E-5 per second

Relative ionospheric electron concentration change rate ~ -1.3E-4 per  second ~ - 0.78 % per minute

More about ionospheric modulations at:
http://herrero-radio-astronomy.blogspot.com/search/label/Ionospheric%20Modulations

Many thanks to Andy for his publication.