Ionospheric research from space vehicles

Bourdeau, R. E.

doi:10.1007/bf00212448

Cited by 41 publications

(5 citation statements)

References 52 publications

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“…[3] It was not until the early 1960s that it became obvious that electron temperatures were sometimes much larger than neutral temperatures in the terrestrial ionosphere, particularly at altitudes near and above the F region [Bourdeau, 1963]. Since that time, dramatic advances have been made in understanding the physical theory and measuring the parameters relevant to plasma temperature calculations, as summarized by, for example, Banks and Kockarts [1973], Cicerone et al [1973], and Schunk and Nagy [2008].…”

Section: Introductionmentioning

confidence: 99%

Plasma temperatures in Saturn's ionosphere

et al. 2008

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We have calculated self‐consistent electron and ion temperatures in Saturn's ionosphere using a series of coupled fluid and kinetic models developed to help interpret Cassini observations and to examine the energy budget of Saturn's upper atmosphere. Electron temperatures in the midlatitude topside ionosphere during solar maximum are calculated to range between 500 and 560 K during the Saturn day, approximately 80–140 K above the neutral temperature. Ion temperatures, calculated for only the major ions H+ and H3+, are nearly equal to the neutral temperature at altitudes near and below the height of peak electron density, while they can reach 500 K during the day at the topside. Plasma scale heights of the dusk electron density profile from radio occultation measurements of the Voyager 2 flyby of Saturn have been used to estimate plasma temperature as a comparison. Such an estimate agrees well with the temperatures calculated here, although there is a topside enhancement in electron density that remains unexplained by ionospheric calculations that include photochemistry and plasma diffusion. Finally, parameterizations of the heating rate from photoelectrons and secondary electrons to thermal, ambient electrons have been developed. They may apply for other conditions at Saturn and possibly at other giant planets and exoplanets as well.

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Section: Introductionmentioning

confidence: 99%

Plasma temperatures in Saturn's ionosphere

et al. 2008

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“…Unfortunately, spaceflight methods for measuring the low electron densities characteristic of the lower D region are not considered reliable (Bourdeau, 1963).…”

Section: The Ionospheric Modelmentioning

confidence: 99%

Transmission of VLF Radio Waves Through the Ionosphere

Wieder

1967

Radio Science

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The fields of 10-kHz radio waves propagating into and through the lower ionosphere are calculated by numerical methods, and the attenuation, polarization, and power flow characteristics are examined as a function of height for daytime and nighttime ionospheric electron density profiles with varying angles of incidence, directions of propagation relative to the earth's magnetic iield, and dip angle. The conclusions are that virtually all the attenuation of the wave occurs in the lower D region of the ionosphere, that the transmitted wave is nearly circularly polarized, and that the energy of the transmitted wave is traveling nearly along the magnetic lines of force in agreement with the predictions of "ray theory." The analysis also shows the strong variation in transmission with dip angle and with change from day to night ionosphere in agreement with observed variations in intensity and in frequency of occurrence of "whistlers." lntrodudionThe coupling of VLF radio energy between the earthionosphere waveguide and the exosphere has important bearing on the understanding of such phenomena as whistler propagation and VLF emissions and on the detection and measurement in space vehicles of VLF signals from transmitters on the ground. The theory of the cou.Plillg of such signals through the ionosphere remains the least well understood facet of VLF propagation phenomena, if not qualitatively, at least quantitatively. This is a consequence of the fact that, for the long wavelengths involved, the ionosphere is a medium which changes significantly within a wavelength so that ray-theory techniques are not appropriate. Full-wave solutions are required which cannot be handled with the same· analytic ease that the ray theory allows..With the advent of large, high-speed digital computers, however, tractable numerical methods have been developed for calculating the fields as the wave penetrates into the ionosphere

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“…The ambipoIar diffusion velocity is expressed by [Shimazaki, 1959] Because it is generally accepted that the atmospheric components are in thermal equilibrium at all heights during the night under quiet solar conditions [Evans, 1962;Bourdeau, 1963], the temperatures are ass•ed to be the same •or ions, electrons, and neutral particles. If they differ, the formula may be modified: T in (5) should be changed •o T • = % (T• + T,), and T in (6) should be changed to T" = (T. + T,)•/2(T, • T•).…”

Section: = V• + V• + W (4)mentioning

confidence: 99%

Nighttime variations ofF-region electron density profiles at Puerto Rico: 2. An attempt to separate the effects of temperature variation and drift velocity

Shimazaki¹

1966

J. Geophys. Res.

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A least‐squares method is presented to determine simultaneously the temporal variations in temperature and drift velocity in the ionosphere from the observed temporal variations in electron density profiles. These are determined so that the continuity equation for electron density may be satisfied very well at all heights and at all hours. The application of the method to the nighttime variations of F‐region electron density profiles at Puerto Rico, March 1959, indicates that the implied nocturnal variations in temperature and drift velocity are quite reasonable and that the relative significance of these two effects strongly depends upon time; the effect of a rapid temperature decrease predominates over the effect of small drift velocity before midnight, while the effect of a large downward drift velocity overcomes the effect of small temperature variations for several hours after midnight. After around 0400 hours in the morning the temperature rises rapidly and both effects of temperature variation and drift velocity are equally dominant. It remains difficult to reconcile the theoretical value of ambipolar diffusion cross section with rocket observations of neutral atmosphere density and composition on the one hand, and with ionospheric observations on the other hand.

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Ionospheric research from space vehicles

Cited by 41 publications

References 52 publications

Plasma temperatures in Saturn's ionosphere

Plasma temperatures in Saturn's ionosphere

Transmission of VLF Radio Waves Through the Ionosphere

Nighttime variations ofF-region electron density profiles at Puerto Rico: 2. An attempt to separate the effects of temperature variation and drift velocity

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