Frequency shift in ionogram gyrofrequency resonance

Additional evidence is presented from Alouette II ionogram data for the observed frequency difference between the plasma resonance detected near the electron gyrofrequency f
H
and the ionospheric value of f
H
=2.8 MHz ċ gauss
^-1
. The observed values of the electron gyrofrequency resonance are usually about one percent higher than the ionospheric values of f
H
.