Jupiter, the largest planet in the solar system, is not only an emitter of thermal radiation like any other planet. Jupiter also emits relatively high-intensity non-thermal radiation in two bands, the decimetre wavelength range and the decametre wavelength range (5 MHz< f < 40 MHz). The decimetric radiation is believed to be due to synchrotron radiation of electrons trapped in a kind of Jovian "Van Allen belt". This thesis deals almost exclusively with the decametric radiation. Although the decametric radiation has been observed for 15 years since its discovery by Burke and Franklin in 1955, there is no generally accepted theoretical model of its generation to be found in the literature as yet. This is not surprising, as there are many complex and confusing aspects of the radiation. And since our knowledge of the Jovian ionosphere, magnetosphere and magnetic field is very limited indeed, every theoretical model must be based on some more or less well justified assumptions. It is, however, possible to draw some conclusions from the observed properties of the decimetric and decametric radiation. The radiation in both bands is polarized. It has been shown that at least part of the polarization is an intrinsic property of the radiation source at Jupiter, This indicates the existence of a Jovian magnetic field. The magnitude and shape of the magnetic field, however, is open to discussion, although a dipole field does seem to be a good approximation at least for large distances from Jupiter. Intro. p. 1-2.

This dissertation combines several new observations of the Io sodium cloud to create a consistent picture of the extended Io atmosphere and its interaction with the Jovian plasma torus. I used the LPL echelle spectrograph to obtain three types of high-resolution spectra of the extended sodium cloud at the sodium D-lines (5890, 5896Å). The first class of observations made use of the mutual satellite eclipses of 1985 to probe the density profile of the atmosphere in the range 1.4 to 10 Io radii, a previously unstudied region. The second type of observation examined the sodium emission in Io's immediate vicinity, allowing an accurate measurement of the velocity structure around Io. The final method employed a high-sensitivity detector to study faint jets of high-speed sodium farther out in the extended cloud. The synthesis of these three data sets results in a better understanding of how sodium is distributed about Io as a function of position and velocity. Io's extended atmosphere is composed of many kinematically distinct components. The distribution in space is linked to their characteristic velocities, with low-energy sodium confined near Io and faster atoms (10 to 100 km sec⁻¹) prevalent beyond ∼25 Io radii. The sodium density profile is steep near Io and shallower outside 5.6 Io radii, the effective limit of Io's gravity. The data indicate that the atmosphere is collisionally thick near the surface, but becomes thin by an altitude of ∼700 km. The upper limit of the exobase location is derived from reliable sodium density measurements made during the satellite eclipses. The lower limit is indirectly inferred from the velocity distribution of sodium near Io and the nature of high-speed jets far from Io. The high-speed sodium jets reveal a new type of close interaction between the corotating plasma and Io's atmosphere. The morphology and brightness of the jets require a two-reaction process, in which atmospheric sodium is ionized, accelerated to high speeds, and then charge-exchanges with other sodium atoms. These processes must occur near the atmospheric exobase, indicating that Io's atmosphere is not completely protected from the plasma flow.

Researchers analyzing the upper clouds of Jupiter and Saturn are unable to theoretically reproduce the data returned by Pioneers 10 and 11 and Voyagers 1 and 2 with an approach based on Mie theory. Ammonia crystals are believed to be an important constituent of Jupiter's upper clouds, but both their shape and scattering properties were unknown at the start of this work. Ammonia crystals and water crystals were grown in a cold chamber at temperatures 20°C below their freezing points (0°C and -77.7°C, respectively). The H₂O crystals formed had shapes in agreement with published growth habit diagrams. The NH₃ crystals formed were usually irregular in shape, but regular four-sided pyramids were commonly observed. This four-sided pyramidal shape is in agreement with ammonia's primitive cubic crystal structure. Ammonia crystals could not be formed at temperatures above -95°C due to nucleation problems. A scattering measuring instrument was constructed with fifteen separate lens-detector combinations aimed at a common point in the center of the cold chamber. A laser beam (6328Å wavelength) traversed the chamber center, illuminating any crystal aerosal clouds present. A computer was used to rapidly sample the outputs of the fifteen detectors and to drive a photoelectric modulator to change the slow speed polarization properties of the laser beam. The measurements resulted in a determination of the single scattering phase function and degree of linear polarization for the crystal species present. Water crystals were found to have scattering properties similar to that reported by previous researchers. The H₂O crystal scattering possesses a smaller backscatter peak and smaller polarization features than is common for water spheres of similar size. A negative polarization of 5% occurred in the forward scattering hemisphere and a positive polarization of 10% in the rear. Ammonia particles were observed to have a backscattering peak four times higher than for water crystals. The NH₃ particle light scattering produced very little polarization of the scattered light. A small (∼ 4%) negative polarization occurred in the forward scattering hemisphere. Work is continuing here to make scattering measurements using blue light illumination nearly simultaneous with the red HeNe laser wavelength illumination.

No description available.

No description available.

Decameter radiation was first observed from Jupiter by Burke and Franklin (JGR 60, 213, 1955). In 1964 Bigg (Nature, 203, 1008, (1964)) found that 1o exerted a profound effect on the radiation. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency. Intro., p. 1. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency (for a review see eg. Warwick, Space Sci. Rev. &" 841 (1967)). More recent work centred around the question of how 10 modulates the emission (see the article of Carr and Gulkis (Annual Review of Astronomy and Astrophysics Vol 8 (1970)) for a detailed review).

From introduction: Jupiter is the largest planet in the solar system. Its distance from the Sun is five times that of the Earth and its mass is nearly two and a half times that of all the other planets added together. Jupiter turns about its own axis rather rapidly, once in just under ten hours, and it completes one revolution about the Sun in just under twelve years. Thus Earth has to pass almost directly between the Sun and Jupiter once every thirteen months. When this happens Jupiter is said to be in "opposition", as its position is then opposite to that of the Sun, when viewed from Earth. Around this time the planet will be most favourably placed for observations, as it is at its closest to Earth and up in the sky for a large part of the night. During the day observations on radio frequencies are more difficult, as the Sun is a source of great interference. Besides being an emitter of thermal electromagnetic radiation, as one would expect, Jupiter also emits two kinds of non-thermal radiation, one in the decimetre wavelength range and the other in the decametre wavelength range. A large number of scientists have worked on the problems of decimetre and decametre radiation. This thesis deals with some aspects of decametre radiation.

Thèse : Sciences : Paris : 1855. / Thèse d'astronomie, 78 p. at end, has title: Application de la méthode de M.-Hamilton au calcul des perturbations de Jupiter. Titre provenant de l'écran-titre.

Spectroscopic measurements in the infrared have proven to be a valuable source of information about the Jovian atmosphere. However, numerous questions remain, many of which will be addressed by the Galileo μission, due to arrive at Jupiter in December, 1995. One of the instruments on Galileo is the Near-Infrared Mapping Spectrometer (NIMS), which will measure temperature structure, cheμical composition, and cloud properties. The objective of the work described in this thesis was to investigate the transmittance properties of the Jovian atmosphere and, in particular, to obtain transmittance functions of CH₄ for future use in the planning and interpretation of NIMS measurements. This thesis begins with a review of our current understanding of the Jovian atmosphere (Chapter 1), and a description of the Galileo μission and the design and objectives of NIMS (Chapter 2). It is then shown (Chapter 3) that absorption bands of CH₄ doμinate the nearinfrared spectrum of Jupiter, but that line data for CH₄ are currently inadequate over much of the NIMS spectral range (0.7-5.2 /μi). For the purposes of NIMS, which has a low resolution of 0.25 /μi, the spectrum of CH₄ can be characterised using band models of transmittance as a function of temperature, pressure, and abundance. The theory of band modelling is presented, and previous band-modelling studies of CH₄ are reviewed and are also shown to be inadequate for NIMS (Chapter 4). An experimental investigation was therefore undertaken to record CH₄ spectra under Jovian conditions of low temperature, large abundance, and H₂-broadening. The experimental resources used to obtain these spectra are described (Chapter 5), the generation of the transmittance spectra is discussed, and their quality is assessed (Chapter 6). The range of frequencies and laboratory conditions covered by these spectra (listed in Appendix A) makes them one of the most comprehensive data sets of this kind yet published. These spectra were subsequently used to derive transmittance functions for CH₄ (Chapter 7). A variety of models were fitted to the self-broadened CH₄ spectra, and the Goody and Malkmus random band models, using the Voigt lineshape, are shown to provide the best fits. These two models were then fitted to the combined set of self- and H₂-broadened CH₄ spectra. The parameters fitted with the Goody-Voigt model are included in this thesis (Appendices B and C). Finally, the application of these new band model fits to the problem of Jovian remote sounding is addressed (Chapter 8). This includes an assessment of the reliability of extrapolation to Jovian conditions, a calculation of the level in the Jovian atmosphere that will be sounded by observations of CH₄ absorption, and a calculation of how the uncertainties in the fitted band model will affect the retrieval of atmospheric parameters from NIMS spectra. This thesis concludes with a detailed summary, and with suggestions for future investigations which will help to maximise the return of information from NIMS.

This thesis describes the investigation carried out of the radio noise emitted by the planet Jupiter on 18 Mc/s and 22 Mc/s. Chapter I gives a brief introduction and outlines radioastronomical as well as astronomical ideas concerning Jupiter. A detailed survey of the research done to date including some of the hypotheses formulated by previous workers is presented in Chapter II . Chapter III deals with the apparatus used in this research. Two similar sets of apparatus were used. The aerials were folded dipoles. The signals were fed to the receiver, an R 206 , via a 300 ohm impedance line. To increase the gain an extra I -F. stage was included. This gave a gain of better than a 120 dB. To match the signals into the recorder a cathode follower was used. The operating procedure appears in the fourth chapter. The results obtained are discussed and tabulated at the end of the chapter. They agree with the findings made by previous workers, within the experimental limit. Histograms of the occurrence probability versus the revised System III coordinates are presented for each frequency and compared to previous ones. The final chapter contains the author ' s interpretation of the observed effects. A model based on a radiation analogous to the Cerenkov effect is found to be not inconsistent with the available data . Ending the chapter suggestions for further research are made.