Plasma resonances in the upper ionosphere

Plasma resonances, detected in the upper atmosphere with the Alouette topside sounder satellite, have been examined. The resonant frequencies have been found to be fN and (fN2+fH2)1/2, where fN is the plasma frequency and fH is the electron gyrofrequency. The two resonances are attributed to electron oscillations along and across the earth's magnetic field respectively.