Superpressure balloon-borne instruments that measure the vector stratospheric electric field at latitudes near 45¿¿10 ¿S reveal several features in fair weather that cannot be attributed to ionospheric, thunderstorm, or other known sources. Over 180 days of electric field, conductivity, and current density data have been taken at the constant altitude of 26 km, using long-duration balloon flights in the southern hemisphere. Throughout these data the fair-weather horizontal electric field has a magnitude (10--50 mV m-1) that cannot be due to mid-latitude ionospheric dynamo action. Furthermore, the fields are highly variable in amplitude, almost turbulent in appearance, while the vector direction steadily rotates in a counterclockwise manner. The period of this rotation is close to the quasi-inertial wave period for the latitude of the balloon. For these flights the electric field rotation period varies between 14 and 21 hours. Some possible causes that might explain the electric field and current measurements reported herein are discussed. ¿ American Geophysical Union 1989