CPI's Auroral ModelCPI's auroral model has been used extensively by CPI scientists and others within the auroral community to investigate emission and ionization characteristics in theoretical studies, data analyses, and development of remote sensing algorithms. Pure electron, pure proton/H atom, and mixed electron/proton/H atom aurora may be addressed by the model. Particle transport calculations are performed that provide altitude profiles of particle fluxes versus energy for specifying excitation and ionization rates. These rates, in turn, are used to calculate column emission rates for a variety of optical emission features and density profiles of chemically active species (neutral and ion). An example of column emission rates in spectral form (in Rayleighs/nanometer) is shown in the figure below for the molecular nitrogen Lyman-Birge-Hopfield band system. The calculation was performed for viewing in the nadir direction from satellite altitudes (i.e., from above the emitting layer). Electron auroral precipitation is considered for narrow distributions in energy (characterized by Gaussian distributions) peaking at 2 and 10 keV. The differences in these spectra arise from absorption within the emitting region by molecular oxygen. The shaded regions identify wavelength intervals for which measurements will be made by the SSUSI instrument on future DMSP satellites. CPI has developed remote sensing algorithms for SSUSI that utilize differences such as those shown for inferring the average energy of the precipitation and related ionospheric parameters.
A second example of model results is shown in the following figure along with rocket photometer measurements from the ARIA II auroral experiment conducted by scientists from the Aerospace Corp. [see Strickland et al., J. Geophys. Res., 105, 2461, 2000 for details]. The data for the five emission features identified in the figure were recorded on the upleg portion of the experiment with the photometers viewing in the zenith direction. Good overall fits to the data are obtained with departures at the higher altitudes arising from soft structured electron precipitation not included in the calculations. As reported in the above paper, data such as these allow one to infer information about neutral composition. For the given experiment, interesting reductions in the density of atomic oxygen are observed (more than a factor of two) that arise from heating associated with particle precipitation and Joule heating.
Approximately thirty papers have been published in peer-reviewed journals documenting CPI's auroral model and its applications. Papers in the former category include: Strickland, D. J., R. E. Daniell, Jr., B. Basu, and J. R. Jasperse, Transport-Theoretic Model for the Electron-Proton-Hydrogen Atom Aurora: 2. Model Results, J. Geophys. Res., 98, 21533, 1993. Basu, B., J. R. Jasperse, D. J. Strickland, and R. E. Daniell, Jr., Transport-Theoretic Model for the Electron-Proton-Hydrogen Atom Aurora: 1. Theory, J. Geophys. Res., 98, 21517, 1993. Strickland, D. J., D. L. Book, T. P. Coffey and J. A. Fedder, Transport Equation Techniques for the Deposition of Auroral Electrons, J. Geophys. Res., 81, 2755, 1976. Under applications, we place the papers into the following categories:
Representative examples of papers in these categories are as follows: Development and use of ground-based remote sensing techniques Strickland, D. J., R. R. Meier, J. H. Hecht and A. B. Christensen, Deducing Composition and Incident Electron Spectra from Ground-Based Auroral Optical Measurements: Theory and Model Results, J. Geophys. Res., 94, 13527, 1989. Hecht, J. H., A. B. Christensen, D. J. Strickland and R. R. Meier, Deducing Composition and Incident Electron Spectra from Ground-Based Auroral Optical Measurements: Variations in Oxygen Density, J. Geophys. Res., 94, 13553, 1989. Hecht, J. A., A. B. Christensen, D. J. Strickland, T. Majeed, R. L. Gattinger, A. Vallance Jones, and T. Moretto, A comparison between auroral particle characteristics and atmospheric composition inferred from analyzing optical emission measurements alone and in combination with incoherent scatter radar measurements, J. Geophys. Res., 104, 33, 1999. Development of satellite remote sensing techniques Strickland, D. J., R. E. Daniell, Jr., B. Basu, and J. R. Jasperse, Transport-Theoretic Model for the Electron-Proton-Hydrogen Atom Aurora: 2. Model Results, J. Geophys. Res., 98, 21533, 1993. Daniell, Jr., R. E. and D. J. Strickland, Dependence of Auroral Middle UV Emissions on the Incident Electron Spectrum and Neutral Atmosphere, J. Geophys. Res., 91, 321, 1986. Strickland, D. J., J. R. Jasperse and J. A. Whalen, Dependence of Auroral FUV Emission on the Incident Electron Spectrum and Neutral Atmosphere, J. Geophys. Res., 88, 8051, 1983. Analyses of rocket and satellite data Strickland, D. J., J. H. Hecht, A. B. Christensen, and D. J. McEwen, Thermospheric disturbance recorded by photometers on-board the ARIA II rocket, J. Geophys. Res., 105, 2461, 2000. Strickland, D. J., J. Bishop, J. S. Evans, T. Majeed, R. J. Cox, D. Morrison, G. J. Romick, J. F. Carbary, L. J. Paxton, and C.-I. Meng, MSX/UVISI limb observations of combined electron/proton/hydrogen aurora, J. Geophys. Res., 106 65, 2001. Anderson, P. C., I. W. McCrea, D. J. Strickland, J. B. Blake, and M. D. Looper, Coordinated EISCAT/DMSP measurements of electron density and energetic electron precipitation, J. Geophys. Res., 102, 7421, 1997. Miscellaneous applications Strickland, D. J., J. H. Hecht, and A. B. Christensen, The Relationship between energy flux Q and mean energy <E> of auroral electron spectra based on radar data from the 1987 CEDAR campaign at Sondre Stromfjord, Greenland, J. Geophys. Res., 99, 19,467, 1994. Strobel, D. F., A. F. Cheng, M. E. Summers, and D. J. Strickland, Magnetospheric Interaction with Triton's Ionosphere, Geophys. Res. Lett., 17, 1661, 1990. Prasad, S. S., D. J. Strickland and Y. T. Chiu, Auroral Electron Interaction with the Atmosphere in the Presence of a Conjugate Field-Aligned Electrostatic Potential, J. Geophys. Res., 87, 4123, 1982. |
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