Generation of gravity waves within the ionosphere by transient heating during high-power wave propagation

Non-linear r.f. heating of ionospheric plasma

Abstract: The non-linear heating of electrons in the ionospheric plasma due to high-power radio wave propagation has been investigated through an integro-differential equation derived from Boltzmann velocity-moment equations. Various processes appropriate to the situation under study are taken into account. The numerical solution of the derived equation is presented graphically.

Ionospheric irregularities produced by internal atmospheric gravity waves

Abstract: A perturbation treatment is used to determine the nature and magnitude of the effects of internal atmospheric gravity waves on the ambient rates of production, chemical loss, and motion of the ionization. The relative and absolute importance of these effects in the creation of ionospheric irregularities are assessed. This assessment yields several conclusions of particular interest. Firstly, in the F 2-region the dominant effect of the gravity waves is that of imparting the motion of the neutral gas parallel to the magnetic field to the ionization through collisional interaction. Secondly, at heights at or below the height of the F1 -ledge, chemical effects, in particular the effect of gravity waves on the rate of photoionization, are quite important. Thirdly, gravity waves affect the rate of photoionization at a given point by changing both the neutral gas number density and the ionizing radiation flux at that point, and this latter effect, hitherto ignored, is in some respects the more important of the two. Fourthly, as a result of the interplay of a number of factors, certain Fourier components of that portion of the gravity-wave spectrum permitted at ionospheric heights are more successful than others in creating observable disturbances. Finally, gravity waves creating neutral gas velocities of the order of 20 m sec −1 seem capable under the right conditions of creating TID's of the largest magnitudes observed.

HF Doppler studies of traveling ionospheric disturbances

Abstract: Wavelike ionospheric motions observed with a network of CW Doppler sounders are analyzed and found to fall into four separate classes not previously distinguished The motions of each type are attributed to various kinds of atmospheric waves that interact with the ionosphere Those previously called merely ‘large traveling disturbances’ are broken into two types: ‘very large,’ which usually follow magnetic storms; and ‘medium-scale,’ which are common during the day but whose association with other geophysical events is not yet known The third class of motions is associated with acoustic waves from severe weather, and the fourth with incoherent, superposed gravity waves propagating to ionospheric heights from below

Atmospheric gravity waves launched by auroral currents

Abstract: Auroral currents have been recognized in the past both theoretically and observationally, as a probable source of atmospheric gravity waves and of associated travelling ionospheric disturbances (TID's). A model calculation is performed here, by which the magnitude and form of the anticipated atmospheric wave train may be assessed. Both are found to be consistent with observations already recorded. The question, as to whether the Lorentz force or the Joule dissipation is the more important exciting agency provided by the current, is left unanswered because of present uncertainties connected with the nature of the current itself.

Observations of joule and particle heating in the auroral zone

Abstract: Observational data from the Chatanika, Alaska incoherent scatter radar have been used to deduce atmospheric heating rates associated with particle precipitation and joule dissipation. During periods when Chatanika is in the vicinity of the auroral oval the height-integrated heat input to the lower thermosphere can be as large as 100 ergs per sq cm per sec with joule and particle heating rates of comparable magnitude. Altitude profiles of these heat inputs are also obtained, showing that the energy liberated by joule dissipation tends to peak at a substantially higher altitude (about 130 km) than that due to particles (100-120 km). As a consequence, it follows that joule heating can be expected to provide a rapid means for creating thermospheric disturbances. It is also pointed out that joule and particle heating are permanent features of the auroral oval and polar cap. As such, expansion of the auroral oval leads to an increase in the total global heating and, hence, to the close relationship between magnetic disturbances and thermospheric perturbation.

Determination of the Structure of the Atmosphere between 90 and 250 km by means of Contaminant Releases at Woomera, May 1968

Abstract: Two Skylark rockets were launched from Woomera rocket range, Australia (31 degrees S) on the morning and evening of 31 May 1968. Coordinated series of measurements of neutral atmospheric wind velocity, turbulent structure, temperature and density were made during each launch between 90 and 250 km altitude, combining the experimental techniques of the two groups involved. This paper attempts to construct from the combined measurements made on these occasions a dynamic picture of the interactions of atmospheric structure, and to relate the observations to previous results obtained by ourselves and other workers.