In situ and laboratory measurements of cold plasmas.

摘要

Measurement of the ionospheric thermal particle population bridges the two different communities of ground-based radar and space-based rocket studies, which have the common goal of characterizing heavy ion transport in the cusp/cleft region. We report on the results of the SERSIO (Svalbard EISCAT Rocket Study of Ion Outflows) mission, which show broad-band-extremely-low-frequency wave-ion heating in an environment observed by the EISCAT (European Incoherent Scatter) radars to have enhanced thermal electron temperature and density, and inferred ion-acoustic activity. The SERSIO data raise questions about the effects of spacecraft charging and sheath formation on thermal particle data analysis. These questions determined the design requirements for a low energy laboratory plasma calibration facility which we built and have begun to use. We discuss the magnetron-based cylindrical resonant plasma source, which produces charged particles with ionospheric energies and densities. The plasmas created with this source have Debye lengths similar to those encountered on ionospheric rocket flights, creating an ideal environment for charging and sheath studies that inform future thermal flight detector design. We investigate electron sheath structures by varying ion to electron collection ratios. The non-monotonic electron sheaths obtained by embedding a positively biased electrode within the sheath of a more negative conductor are explored. These initial plasma ion and electron sheath investigations both clarify the behavior of a thermal electron detector previously flown, and explore a low density and long Debye length parameter regime that is under-studied in the laboratory.