January 29, 2010, 12:00 pm - 1:00 pm

January 29, 2010, 12:00 pm - 1:00 pm

Thermal Ion Imaging: Technique and Results

David Knudsen (Department of Physics and Astronomy and Institute for Space Imaging Science University of Calgary)

Ionospheric plasma flow and temperature measurements made in-situ pose numerous challenges: large variations in density and flux, small temperatures and flow energies (typically << 1 eV), sheath and stray potentials of the same order (tens to hundreds of mV) around and within instruments, wake effects, and more. This talk will describe the development over the past decade of the thermal ion imaging technique (TII) that was designed with these challenges in mind. TII uses a novel electrostatic analyzer design to form 2-D images (angle- energy) of charged particle distribution functions from which temperature and velocity moments can be computed. The technique is unusual also in that is uses a CCD-based detector instead of more conventional position-sensitive detectors such as wedge-and-strip. I will explain the technical motivations for the TII approach, and will show scientific applications from four sounding rocket flights including measurements of localized ion heating cavities in the aurora, demagnetization and neutral wind entrainment of ions in the auroral E region, dayside cusp upflows, and post-sunset field-aligned plasma flows at mid latitudes.