Browsing by Author "Dempsey, Donna Lynn"

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    Observations of dayside magnetopause oscillations and concurrent temporal variations in cusp precipitation
    (1999) Dempsey, Donna Lynn; Young, David T.
    On April 13, 1996, while Russia's Interball Tail spacecraft was travelling through the dayside magnetosheath, NASA's Polar spacecraft traversed the northern cusp. Transients observed in the data from the Interball Tail/SCA-1 particle instrument are shown to be multiple crossings of the magnetopause. Analysis of data from the SCA-1 instrument and magnetic field data from the MIF instrument shows quasi-periodic motions of the magnetopause. Simultaneous observations of changes in cusp precipitation by the Polar/TIDE instrument and changes in the He2+/H+ density ratio in the cusp by the Polar/TIMAS instrument show variations on the same time scale. We show that the variations in the cusp data observed by Polar are the result of changes in the reconnection rate at the magnetopause and that these changes are associated with the magnetopause oscillations observed by Interball.
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    Optical development of an ion/electron acceleration facility
    (1998) Dempsey, Donna Lynn; Young, David T.
    This thesis details the optical development of an ion/electron accelerating facility at Southwest Research Institute which is currently being used to calibrate the Plasma Spectrometer for the Cassini Mission to Saturn. The optical development involves particle (ion) ray tracing of each element in the facility in order to computationally determine the focusing and mass separating parameters of each of the elements. This computational data is then compared with the actual output beam from the accelerating facility. The behavior of each of the elements is determined and its affect on the output beam is established. Changes to the design of the facility can then be made based upon this information.