The Cameo Barium Releases: E_∥ Fields Over the Polar Cap

force at orbital velocity would accelerate the Ba + ions to much greater altitudes for measuring Ell fields by observing perturbations in the motion of the visible ions. The principal unexpected characteristic in the release dynamics was the high, 1.4 to 2.6 km/s, initial Ba + expansion velocity relative to an expected velocity of 0.9 km/s. Characteristics of the neutral gas expansion are also discussed. Under the combined influence of/VB and Ell forces the finely striated Ba + streamers from the 8 kg releases elongated along the field to dimensions > 10,000 km and were photographed from California and Hawaii as well as higher latitude sites. Although observed up to one hour after release and to elevation angles >55 ø from Southern California, triangulations of upper tips were limited to the initial 25 min and altitudes <23,000 km. The average E_ convection of the Ba + flux tubes was very normal for Kœ -- 3 conditions and closely followed model patterns for convection between the pole and the midnight auroral zone. However, over shorter space-time dimensions the El field is observed to be irregular; this also is a normal polar cap condition. From the analysis of field aligned motions in terms of the potential changes required in the equation of motion to match the altitude versus time observations: (1) Eli fields do not appear below 1400 km, (2) between 1500 and 4200 km the changes in energy are typically 20-40 eV with a 71 eV maximum, (3) between 4200 and 15,000 km maximum values are in the range 80-720 eV with the highest values coming from the highest latitude releases, and (4) in the case of one release a 6 keV acceleration appears above 15,800 km. These changes appear as both accelerating (upward Ell ) and decelerating (downward Ell ) fields with an apparent periodicity of 3 to 4 min and are in phase at all four locations for 3, and possibly 4 or 5, cycles within the limitations imposed by a 1 min resolution and data gaps. This apparent wave characteristic could, under selective error assumptions, result from several impulsive decelerations superimposed on a more general, but variable, accelerating field. This possibility is considered to be less likely than a hydromagnetic wave association. The unique capabilities for measuring very weak fields and for separating temporal and spatial variations may explain the lack of precedent from previous Ell measurements.