Theoretical studies of the mid-latitude ionosphere

  • Ali A. Al-Naghmoosh

    Student thesis: Doctoral ThesisDoctor of Philosophy


    Following a brief description of the atmosphere and ionosphere in Chapter I we describe how the equations of continuity and momentum for 0+, H+, He+, 0++ are derived from the formulations of St-Maurice and Schunk(1977) and Quegan et al.(1981) in Chapter II.
    In Chapter III we investigate the nature of the downward flow of protons in a collapsing post-sunset ionosphere. We derive an analytical form for the limiting temperature, we also note the importance of the polarization field term and concluded that the flow will remain subsonic for realistic conditions.
    The time-dependent behaviour of He+ under sunspot minimum conditions is
    investigated in Chapter IV. This is achieved by numerical solution of the 0+, H+ and,He+ continuity and momentum equations, treating He+ as a minor ion with 0+ , H+ as major ions. We found that He+ flows upwards during the day-time
    and downwards during the nighttime. He+ flux tube content reached a maximum on the 8th day of the integration period and started to decreasing. This is due
    to the large amount of H+ present at the late stages of the integration period
    which makes He+ unable to diffuse through the H+ layer away from the loss region.
    In Chapter V we investigate the behaviour of 0++ using sunspot maximum
    parameters. Although our results support the findings of Geis and Young (1981)
    that the large amounts of 0++ at the equator are caused mainly by thermal diffusion, the model used by Geis and Young overemphesizes the effect of thermal diffusion. The importance of 0++ - 0+ collision frequency is also noted.
    In Chapter VI we extend the work of Chapter IV, presenting a comparative study
    of H and He at sunspot minimum and sunspot maximum.In this last Chapter all
    three ions, O+ ,H+ and He+ , are treated theoretically as major ions and we
    concentrate mainly on light ion contents and fluxes. The results of this Chapter
    indicate that by assuming He+ as a minor ion we under-estimate He+ and over-estimate. H+. Some interesting features concerning the day to day behaviour of the light ion fluxes arise. In particular the day-time H+ fluxes decrease from day to day in contrast to the work of Murphy et al.(1976).
    In appendix.A we derive some analytical forms for the optical depth so that
    the models can include a realistic description of photoionization.
    Date of AwardNov 1981
    Original languageEnglish


    • modelling
    • terrestrial ionosphere
    • mid-latitudes

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