Long term changes in the electrical conductivity of the stratosphere

Stratospheric electrical conductivity measurements have been made from high altitude research balloons at various locations around the world for more than 30 years. In the stratosphere, conductivity is affected by a number of things, including changes in aerosol or water vapor content. In this paper, we compare data taken in the last five years at mid latitude locations with data taken in the previous three decades at both mid and high latitude from a total of more than 40 balloon flights. Existing models for the effects of geomagnetic latitude, temperature, and other factors have been used to normalize the conductivity data for comparison. Low noise background has permitted the observation of a solar cycle dependence in the equatorial data. Otherwise, this limited statistical sample exhibits short term variations that completely obscure any long term climatic trends that may have occurred during the past three decades.