Changes in electron density and collision frequency at University Park, Pennsylvania during the stratospheric warming of 1967/68

The electron density and collision frequency profiles obtained from the high power wave interaction observations at The Pennsylvania State University were examined for possible changes during the stratospheric warming of December 1967 to January 1968. The electron density increased quite sharply above 70 kilometers with maximum enhancement (about a factor of 10) at about 75 to 80 km. No change was observed in the collision frequency at heights between 50 and 90 km, and there was no significant change in the electron density below 70 km. From examination of the electron density and absorption data it appears that the effect began early December, 1967, reached a maximum between December 25 and January 1, and ended about January 20, 1968. There is some indication that the diurnal variation in electron density at 80 km became slower during the warming than during normal days, possibly indicating increasing control of ionization production through Lα