Charged particle measurements in the polar summer mesosphere obtained by the DROPPS sounding rockets Original Research Article

Two Black Brant V sounding rocket payloads (DROPPS) were flown as part of the DROPPS/MIDAS program from the Andøya Rocket Range, Norway, during July 1999. One of these payloads was launched during the presence of PMSE, and the other flight occurred during NLC conditions. Both payloads were equipped to measure a number of different electrodynamic parameters of the mesosphere and lower thermosphere. A fixed-bias Langmuir probe observed small-scale structure in electron concentration. Significant electron depletions (more than an order of magnitude) were measured in a narrow altitude region during both flights. Layers of a thickness between 300 and 1400 meters were observed with very sharp transitions at the edges of the layers. These electron depletions do not appear to be artifacts produced by electrode collisions with large positive particulates. Absolute electron density concentrations were determined by a multiple-frequency radio wave propagation experiment. In addition, ion conductivities, mobilities, and number densities were determined by a Gerdien condenser. In this paper, we report on the instrumentation and the preliminary observations of the charged particle environment.