The electron temperature changes due to 3, 5 and 430 MHz radio wave heating in the lower ionosphere are measured using incoherent scatter diagnostic techniques and are also calculated from heating/cooling theory. The experiments were performed at Arecibo Observatory using the new HF heating facility and the Arecibo Observatory 430 MHz incoherent backscatter system. In order to interpret the incoherent scatter results a spectral parameter library is developed which gives the spectral width, the spectral maximum and the bandlimited power of the incoherent scatter spectrum for a wide range of ionospheric parameters. There are two collisional formulations which have been widely used to reduce incoherent scatter data in the D and E regions: Dougherty and Farley (1963) and Waldteufel (1970). To determine which collisional formulation should be used, we examine the results of recent Arecibo experiments performed in an unheated ionosphere. A comparison of the measured electron-neutral collision frequency values derived from the two different collisional formulations to the predicted model values show excellent agreement for the Dougherty and Farley formulation but less than satisfactory agreement for the Waldteufel formulation. Using the Dougherty and Farley formulation we determine electron temperature changes from the measured heated-to-ambient spectral parameter ratios. In comparing the measured electron temperature changes to the predicted changes for 430 MHz heating we find a large discrepancy throughout the D and E regions: the measured electron temperature changes are much less than the predicted. The discrepancy in the 75-100 km region can be removed by increasing the model O(,2) rotational cooling rate by a factor of 10, while the discrepancy below 75 km can be removed by a factor of 4 increase. The cooling rate increases, however, are not the only possible explanation for the discrepancies. Two other effects, the non-Maxwellian electron velocity distribution and heat conduction, could remove the discrepancies if the magnitude of their effects were significantly increased in the model. The discrepancies could also be removed by using a f('2.18) frequency scaling law for the predicted heating rather than the currently accepted f('2) law, but there are no physical explanations to support this modification. The 3 and 5 MHz heating results are in satisfactory agreement with the model if D region absorption is taken into account and, thus, do not support the increased cooling rates suggested by the 430 MHz results. The agreement of these results, however, would not be significantly affected by the other suggested modifications. The heating due to the 52 (mu)sec diagnostic pulse is also measured. The diagnostic pulse heating at 70 km is found to increase the electron temperature by a factor of 2.85 (+OR-) 1.35 above ambient. Although the error estimates are large, this increase is in agreement with the predictions of the model.

Voyager IRIS measurements on Jupiter show substantial vertical and horizontal structure which I apply to an assessment of the associated global scale dynamics. The retrieved temperature profiles indicate a variation of static stability between 4 x 10('8) cm('2)s('-2) and 2 x 10('9) cm('2)s('-2) from upper tropospheric ((TURN) 365 mb) to stratospheric ((TURN) 20 mb) levels. Meridional cross sections of the thermal deviations from both the zonal and global (area-weighted) means show a coherent organization on the scale of the belt-zone spacing. The computed zonal thermal wind shear between 100 and 300 mb is strongly correlated with the imaging measurements of the zonal flow and in the sense required to significantly reduce the strength of the observed jet streams over some 2-6 scale heights above the cloud deck. I compute the available potential energy reservoirs for the upper troposphere and show that these also vary with latitude in proportion to the kinetic energy reservoirs inferred from imaging measurements. Both the available potential energy and the eddy kinetic energy reservoirs are, however, more than a decade smaller than the estimated zonal mean kinetic energy. I review the observational evidence and constraints for possible planetary wave propagation in Jupiter's upper atmosphere from Voyager IRIS, radio occultation, and imaging measurements. I then apply the dispersion relations for planetary waves on an equatorial beta plane to a diagnostic assessment of the observed vertical and longitudinal scales. Although no single wave mode can be unequivocally identified, the lower order equatorial Rossby modes with an equivalent depth of h(, )<(, )2 km are most easily related to all the observations of features with a zonal planetary wavenumber n (LESSTHEQ) 20. The Kelvin and inertia-gravity modes with h(, )<(, )0.1 km are also acceptable solutions for a more restricted range of observations. If the wave interpretation is correct, unstable growth estimates consistent with the radio occultation profiles imply strong forcing at or below the tropopause.

Three meter striations are produced in response to the heating of the ionosphere by a powerful high frequency (HF) radio wave. The striations are electron density perturbations aligned parallel to the geomagnetic field in the heated region of the ionosphere. They are formed within seconds as a direct consequence of the heating, and disappear rapidly after the heater has been turned off. Recent experiments were conducted to investigate the evolution times of the striations. The experiments combined the use of the new HF facility at the Arecibo Observatory with a portable 50 MHz radar located on either the island of St. Croix or Guadeloupe. Striations were observed in both the E and the F regions of the ionosphere. The conclusions of our investigation can be summarized as follows. First, relationships have been determined between the striations' rise and fall times and the electron collision frequency, temperature, and density. Second, the rise times of the striations are found to be dependent on the HF electric field. The nature of this dependency is presented and interpreted. Third, both the E and the F region data verify previous theoretical predictions that the striations' decay times are directly proportional to the electron diffusion across the magnetic field. Finally, the temporal interaction between the striations and the enhanced plasma line, another HF-induced phenomenon, is studied. For the first time, a relationship between the rise times of the striations and the overshoot of the enhanced plasma line has been experimentally determined. This last finding addresses the primary motivation of plasma heating experiments; that is, an understanding of the mechanism by which energy is transferred to and through the plasma. Our results suggest that energy cascades from the large scales of initial HF excitation to the smaller scales associated with the striations.

In this study a hierarchy of simple climate models is built and used to assess the impact of changes in the trace gas abundance of Earth's atmosphere on the global and zonal surface temperatures. Two of the four models presented use the Equivalent Radiative Atomosphere approximation to treat the greenhouse effect of water vapor, carbon dioxide and ozone. The other two models have vertically resolved atmospheres and use broad band absorptance and emissivity models in the treatment of radiative exchanges. Two of the models have resolution in the meridional direction and the horizontal energy transport is approximated by a linear, constant coefficient diffusion. A series of sensitivity experiments is conducted with these models to assess the relative importance of various parameters and modeling assumptions. All of the models are sensitive to variations in solar irradiance: the range of the response, quantified in terms of the (beta) parameter, ranges from 71 K to 186 K. The response is highly dependent on the strength of the water vapor feedback in the particular model. Another series of calculations is concerned with the impact of changes in the CO(,2) abundance of the atmosphere on the surface temperatures. The range of the response to a doubling of the CO(,2) abundance is from 2.5 K to 10 K for ERA based models and from 1.9 K to 6 K for the others. The response depends on the latitude and most importantly on the water vapor feedback strength. The effect of minor trace gases O(,3), CH(,4) and N(,2)O on the globally averaged temperature is also studied. A 50% decrease in O(,3) column density lowers the surface temperature by 0.28 K. A doubling of the present atmospheric abundance of CH(,4) and N(,2)O heats the surface by 0.25 K and 0.42 K, respectively.

The theory of planetary exospheres is extended to incorporate solar radiation pressure in a rigorous manner, and an evaporative geocoronal prototype (classical, motionless exobase) is constructed using Liouville's theorem. Calculations for density and kinetic temperature at points along the Earth-Sun axis (solar and anti-solar directions) reveal an extensive satellite component, comprising (TURN)2/3 of the total hydrogen density near 10 Earth radii, and a temperature profile suggestive of a near-isotropic quasi-Maxwellian kinetic distribution for the bound component. A geotail is also evident in this model as an enhancement of the local midnight density compared to local noon that increases radially outward from roughly 25% at 10 Earth radii to over 60% at 20 Earth radii. Additional mechanisms acting upon the geocorona alter this evaporative case in notable ways. Solar ionization has been included in a simple fashion; the effect is to deplete the density somewhat without otherwise altering the structure. Interaction with a simple plasmasphere via the Boltzmann equation results in heating the geocorona and enhancing the escape flux at the expense of the density of the bound component, an effect not appreciated in earlier studies; the geotail survives this interaction.

Electric field measurements inside two severe thunderstorms in Oklahoma were acquired with instrumented free balloons in order to investigate the properties of the storm electrical charge regions. These measurements are analyzed in conjunction with the balloon meteorological measurements and standard weather and Doppler radar data sets to relate the charge regions with the storm environmental features. The first known electric field measurements to be made within the core of a severe storm are presented. The storm exhibited a bipolar charge structure with diffuse net positive charge in the upper portion of the cloud and concentrated negative charge in the lower cloud. The average charge concentrations of the two regions were 0.15 nC/m('3) and -1.2 nC/m('3) respectively. The lower negative region was less than a kilometer in vertical extent, located at the -9 C atmospheric temperature level, and coincident with downdraft air in heavy precipitation. Highly concentrated charge of up to -16.7 nC/m('3) was observed in a thin region less than 100 meters in vertical extent. Electric fields in the anvil region of a severe storm were measured in two widely separated locations. The similar features of both measurements indicate that large amounts of layered charges extended horizontally for several tens of kilometers within the severe storm anvil. A 2 km thick layer of positive charge was measured in the lower portion of the anvil. A layer of negative charge, previously unobserved in thunderstorm anvils, was measured above the positive layer. Three measurements of charge screening layers at cloud boundaries were acquired. The layers were observed to extend approximately 300 meters or more into the cloud with evidence that their depth was largely influenced by turbulence at the cloud boundary. Measured charge concentrations were comparable to those of the main charge regions in thunderstorms. The unique calibration of the electric field measuring instrument, a corona probe, is presented. The effects of the various atmospheric parameters on the electric field measurements are evaluated so that for the first time, thunderstorm electric fields can be accurately determined with a corona probe.

Observations of an air-mass thunderstorm occurring July 22, 1977, during the Thunderstorm Research International Program (TRIP-77) at Kennedy Space Center (KSC), Florida are interpreted. These observations yield insight into storm dynamical and eletrical mechanisms and their interrelationships. The dynamics of this storm are markedly different from that of the classical picture of an isolated convective system. The observed air-mass cells exhibit dynamic and electric changes on time and spatial scales that are significantly smaller than described in text book examples: time scales on the order of 10 rather than 30-90 minutes and areal extents on the order of < 4 km rather than 6-10 km. Fast scanning radar (NMIMT-REDBALL) images indicate that dynamic periodicity is produced by rapid buoyant-bubble growth. Comparison of acoustic and radio frequency (RF) derived source locations suggest that these techniques depict entirely different scale phenomena. The RF (KSC-REAL TIME LDAR) consistently located sources higher in the cloud than the concurrent thunder locations. These thunderstorms produce copious quantities of RF radiation from small discharge processes that are not classically considered lightning (i.e., a flash of light followed by thunder). There is temporal complementarity (anticorrelation) in the activity profiles of the small upper-cloud discharges and lightnings; i.e., RF "sizzle" precedes lightning that produces an acoustic "bang". When acoustic source locations of sequential events are overlaid, the volumes depicted by these loci seek or fill disjoint jet contiguous regions rather than repeatedly discharging the same volume. This is important to considerations of thunderstorm charging rates because the lightnings are not discharging the same volume, hence, cloud volume recharging between events is not necessary. The inherent temporal and spatial "granularity" in the data acquisition makes data comparisons difficult which inhibits the ability of such experiments to resolve questions of cloud electrification. The testing of these hypotheses requires highly resolved ground based observations and in situ microphysical and electrical measurements. Attention to simultaneity in data acquisition is paramount in the design of cooperative thunderstorm electrification studies.

In September 1983 a series of HF ionospheric modification exper- iments were conducted in Scandinavia using the heating facility near Tromso, Norway. The purpose of these experiments was to examine the mechanisms by which high-power HF radio waves produce geo- magnetic field-aligned striations (FAS) in the auroral E region. The vast majority of the backscatter observations were made with radars operating at 47 and 144 MHz (STARE Finland). Additionally, limited observations were conducted at 140 (STARE Norway) and 21 MHz (SAFARI). These radars are sensitive to irregularities having scale lengths between 1 and 7 m across the geomagnetic field lines. During periods of full power O-mode heating, striations having peak cross sections of 40 - 50 dBsm are observed. Striations are not detected during times of X-mode heating. When the heater output is varied a corresponding change in the cross section is measured. The magnitude of the change is most pronounced for heater level changes in the range 12.5 to 50% of full power. These cross sections are significantly larger than those measured at midlatitudes using the Arecibo heater ((TURN)10('1) m('2)). This is consistent with theoretical studies which indicate that it is easier to excite short-scale FAS at places where the geomagnetic dip angle is large. The growth and decay times of the striations are frequency dependent. The growths are variable and can range up to a few seconds if the ionospheric conditions are only marginal for striation development. Under more ideal conditions, growth times are 10('1) - 10('2) ms at VHF frequencies and 10('2) - 10('3) ms at 21 MHz. Decay times follow closely with predictions based upon diffusion across field lines. The times range from 1 s at 21 MHz.

Earth, Mars, and Venus formed at about the same time and in the same region of the solar nebula. It is therefore reasonable to assume that their initial composition and tectonic activity were similar. I use this as the major assumption in my study of the early atmospheres of these planets. A primary goal was to estimate the partial pressure of CO(,2) in the early atmospheres. This problem was approached in an inverse sense. I used a one dimensional radiative-convective model of the atmosphere to determine what levels of CO(,2) would be needed to maintain the climatic conditions that are thought to have existed on these planets 4.0 billion years ago. The range of possible atmospheric compositions is large for any one planet, but narrows considerably when the composition must be compatible with conditions on all three planets. From a comparative analysis of the planets, I estimate that 4.0 billion years ago the surface partial pressure of CO(,2) on Mars was between 1.3 and 2.1 bars and its partial pressure on Earth may have been as high as 14 bars. The Earth and Martian atmospheres were very stable and would not have gone into a runaway greenhouse state even if the CO(,2) partial pressure had been equivalent to 100 bars on Earth. On the other hand, because of its proximity to the sun, radiative-convective equilibrium could not be reached on early Venus for CO(,2) partial pressures less than about 3.5 bars. For surface pressures up to 11 bars, the Venus atmosphere was very susceptible to the rapid photodissociation of water vapor and the subsequent escape of hydrogen. At partial pressures greater than 15 bars of CO(,2), the increased albedo of Venus due to Rayleigh scattering dominates and the atmosphere becomes stable against a runaway greenhouse state. This stabilizing effect of Rayleigh scattering in massive CO(,2) atmospheres, along with the relative distance of the Earth and Venus from the sun played an important role in the very divergent evolutions of the terrestrial atmospheres.

Sidebands on the high frequency (HF) waves received from two transmitted waves separated by small frequency intervals were first observed by Gordon and Ganguly in January, 1984 at Arecibo, Puerto Rico. Papadopoulos proposed that HF sidebands would arise from the nonlinear interaction of an ELF wave with the two high frequency waves. The nonlinear mechanism for ELF and HF sideband generation is parametric decay of a high frequency radio wave into a low frequency compressional Alfven wave and a high frequency sideband (Papadopoulos et al., 1982). In 1984 Fejer proposed another nonlinear mechanism (phase modulation theory) for HF sideband generation. Fejer points out that the effect of the ponderomotive force is a reduction in the electron density and an increase in the phase delay which is greater for more powerful waves. Numerical solutions show that the phase delay would relate to the power density of the HF wave. This modulation index theory using the W.K.B. approximation shows that the amplitude of sidebands is related to: (1) the effective HF power; (2) the HF frequency; (3) the temperature of the electrons; (4) the scale height of the ionosphere; and (5) the difference frequency of the two pump waves. Observations of HF sidebands were again made in January, 1986. The 430 MHz incoherent radar provided the ionospheric background measurements. The modulation index theory provides the most complete interpretation of the observations.