Experiment Luxembourg: Cross modulation at high latitude, low height. Part I: Theoretical aspects

Experiment Luxembourg, based on cross modulation of two radio waves, was put into operation at College, Alaska, at the beginning of the summer in 1960 to study the
D
-region ionization. Part I of this paper presents an extensive analysis of the radio-wave interaction mechanism. It discusses how the cross modulation can be produced not only by changing the electron collision frequency (the classical Luxembourg effect), but also by changing the electron density. It shows that both contributions can be significant. The changes in electron density that are considered are not related to ionization processes, but to perturbations of the attachment processes. Part II of this paper gives a critical examination of the analytical results derived in Part I. Important experimental aspects related to the operation of Experiment Luxembourg are illustrated. Some of the records obtained during the first period of operation are presented and discussed. From the discussion of the experimental results, it is clear that 1)ionization was detected at heights as low as 30 km, and 2) the electrons, at least at 40 km, are not in thermal equilibrium with the atmosphere, but show a temperature of about
1200\deg
K.