Search

The effects of Doppler shifting on the line centers of the magnetospheric O(+) cross section are investigated, and the resulting structure of the scattering rate as a function of bulk density is explained. Whereas the Doppler shifting frequently results in a decrease of the scattering rate, it is demonstrated that for certain drift speeds the overlap of the cross section and the solar intensity profile can lead to an increased rate, thus enhancing the relative brightness of the image above that obtained when v(p) is zero. Simulated images of the magnetosphere are obtained which are used to show quantitively how the magnetospheric image responds to variations in plasma drift speed and temperature. Changes in the brightness of the magnetospheric images also depend on the variability of the solar flux at 83.4 nm. In regions where there are plasma drifts, the brightness in the image is governed by the structure of the scattering rate, assuming a fixed temperature.

Simulated images of extreme ultraviolet (EUV) emissions from energetic outflowing ions have been constructed to study techniques for remotely sensing the dynamic behavior of hot plasmas in the near-Earth environment. These calculations include realistic assumptions about the energetic ion outflow from high latitudes and take into account the effects of cold plasmaspheric and ionospheric ions. The energetic ion outflow is determined from a statistical study based on five years of measurements from the Energetic Ion Composition Spectrometer on Dynamics Explorer 1. The simulated images change significantly with viewing geometry and certain spacecraft locations are clearly favorable for observing emissions from energetic ions. For example, for a near equatorial orbit, viewing locations greater than 9 Earth radii are required to observe outflowing ions above the cold plasmaspheric background. We will discuss other important considerations for magnetospheric imaging including the sensitivity requirements of the detector. In particular, we consider the performance of multi-layer optics for EUV wavelengths.

EUV images from emissions of O+ (83.4 nm) and He+ (30.4 nm) distributions in the plasmasphere and trough regions are constructed for a satellite at 9 Re (where Re is Earth radii). A diffusive equilibrium model is used to describe the density distribution along the field lines for ions in the plasmasphere, and a kinetic collisionless model is assumedto calculate ion densities in the high-latitude regions beyond the plasmapause. In our model ofthe plasmasphere, we assumethat ions move along astatic dipole field. Observational data on O+ and He+ densities in the ionosphere are used as boundaryconditionsto calculatethespatial distribution of densities along the field lines. Assuming thatthe day and night boundary conditions are asymmetric and exobase densities vary with latitude, we discuss how this would be reflected in the intensities and structure of the magnetospheric images.