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Showing papers by "Goddard Space Flight Center published in 1992"


Journal ArticleDOI
TL;DR: In this paper, the first year of data from the differential microwave radiometers on the Cosmic Background Explorer was presented, and the angular autocorrelation of the signal in each radiometer channel and cross-correlation between channels were consistent and gave a primordial fluctuation power-law spectrum with index of 1.1 +/- 0.5, and an rms-quadrupole-normalized amplitude of 16 +/- 4 micro-K.
Abstract: Results of the first year of data from the differential microwave radiometers on the Cosmic Background Explorer are presented. Statistically significant structure that is well described as scale-invariant fluctuations with a Gaussian distribution is shown. The rms sky variation, smoothed to a total 10-deg FWHM Gaussian, is 30 +/-5 micro-K for Galactic latitude greater than 20-deg data with the dipole anisotropy removed. The rms cosmic quadrupole amplitude is 13 +/-4 micro-K. The angular autocorrelation of the signal in each radiometer channel and cross-correlation between channels are consistent and give a primordial fluctuation power-law spectrum with index of 1.1 +/-0.5, and an rms-quadrupole-normalized amplitude of 16 +/-4 micro-K. These features are in accord with the Harrison-Zel'dovich spectrum predicted by models of inflationary cosmology.

2,195 citations


Journal ArticleDOI
TL;DR: Simulations using radiative transfer computations on arithmetic and natural surface spectra, for various atmospheric conditions, show that ARVI has a similar dynamic range to the NDVI, but is, on average, four times less sensitive to atmospheric effects than theNDVI.
Abstract: An atmospherically resistant vegetation index (ARVI) is proposed and developed for remote sensing of vegetation from the Earth Observing System (EOS) MODIS sensor. The same index can be used for remote sensing from Landsat TM and the EOS-HIRIS sensor. The index takes advantage of the presence of the blue channel (0.47.+or-0.01 mu m) in the MODIS sensor, in addition to the red (0.66+or-0.025 mu m) and the near-IR (0.865+or-0.02 mu m) channels that compose the present normalized difference vegetation index (NDVI). The resistance of the ARVI to atmospheric effects (in comparison to the NDVI) is accomplished by a self-correction process for the atmospheric effect on the red channel, using the difference in the radiance between the blue and the red channels to correct the radiance in the red channel. Simulations using radiative transfer computations on arithmetic and natural surface spectra, for various atmospheric conditions, show that ARVI has a similar dynamic range to the NDVI, but is, on average, four times less sensitive to atmospheric effects than the NDVI. >

1,061 citations


Journal ArticleDOI
TL;DR: In this article, a simple implementation of the Arakawa and Schubert (1974) cumulus parameterization is presented, where the major simplification made is to "relax" the state toward equilibrium each time the parameterization was invoked, rather than requiring that the final state be balanced.
Abstract: A simple implementation of the Arakawa and Schubert (1974) cumulus parameterization is presented. The major simplification made is to 'relax' the state toward equilibrium each time the parameterization is invoked, rather than requiring that the final state be balanced, as in the original Arakawa-Schubert implementation. This relaxed Arakawa-Schubert (RAS) scheme is evaluated in off-line tests using the Global Atmospheric Research Program (GARP) Atlantic Tropical Experiment (GATE) Phase III data. The results show that RAS is equivalent to the standard implementation of Arakawa-Schubert but is more economical and simpler to code. RAS also avoids the ill-posed problem that occurs in Arakawa-Schubert as a result of having to solve for a balanced state.

1,050 citations


Journal ArticleDOI
TL;DR: The authors describe the status ofMODIS-N and its companion instrument MODIS-T (tilt), a tiltable cross-track scanning spectrometer with 32 uniformly spaced channels between 0.410 and 0.875 mu m, used for determining the total precipitable water vapor and atmospheric stability.
Abstract: The authors describe the status of MODIS-N and its companion instrument MODIS-T (tilt), a tiltable cross-track scanning spectrometer with 32 uniformly spaced channels between 0.410 and 0.875 mu m. They review the various methods being developed for the remote sensing of atmospheric properties using MODIS, placing primary emphasis on the principal atmospheric applications of determining the optical, microphysical, and physical properties of clouds and aerosol particles from spectral reflection and thermal emission measurements. In addition to cloud and aerosol properties, MODIS-N will be used for determining the total precipitable water vapor and atmospheric stability. The physical principles behind the determination of each of these atmospheric products are described, together with an example of their application to aircraft and/or satellite measurements. >

995 citations


Journal ArticleDOI
TL;DR: In this article, a more sophisticated and realistic treatment of leaf physiological processes within a new canopy integration scheme was proposed, and the results indicated that area-averaged spectral vegetation indices, as obtained from coarse-resolution satellite sensors, may give good estimates of the area-integrals of photosynthesis and conductance even for spatially heterogeneous (though physiologically uniform) vegetation covers.

930 citations


Journal ArticleDOI
22 May 1992-Science
TL;DR: Models and the observational network for oxidants are improving, but validation of global models is still at an early stage and positive and negative trends possible for OH and H2O2.
Abstract: A number of critical atmospheric chemical problems depend on the earth's oxidizing capacity, which is essentially the global burden of oxidants in the lower atmosphere. There is limited direct evidence for changes in the earth's oxidizing capacity since recent preindustrial times when, because of industrial and poulation growth, increasing amounts of O3 precursor trace gases (carbon monoxide, nitrogen oxides, and hydrocarbons) have been released into the atmosphere. The concentrations of O3 and possibly H2O2 have increased over large regions. Models predict that tropospheric O3 will increase about 0.3-1.0 percent per year over the next 50 years with both positive and negative trends possible for OH and H2O2. Models and the observational network for oxidants are improving, but validation of global models is still at an early stage.

764 citations


Journal ArticleDOI
TL;DR: In this article, an algorithm utilizing reflectance spectra bands in the photosynthetically active radiation (PAR) region of the solar spectrum was developed for the remote estimation of the concentrations of chlorophyll a, chlorophyck b, and carotenoids in soybeans.

747 citations


Journal ArticleDOI
17 Apr 1992-Science
TL;DR: Analysis of updated ozone records, including 29 stations in the former Soviet Union, and analysis of independently calibrated satellite data records confirm many of the findings originally derived from the Dobson record concerning northern midlatitude changes in ozone.
Abstract: Recent findings, based on both ground-based and satellite measurements, have established that there has been an apparent downward trend in the total column amount of ozone over mid-latitude areas of the Northern Hemisphere in all seasons. Measurements of the altitude profile of the change in the ozone concentration have established that decreases are taking place in the lower stratosphere in the region of highest ozone concentration. Analysis of updated ozone records, through March of 1991, including 29 stations in the former Soviet Union, and analysis of independently calibrated satellite data records from the Total Ozone Mapping Spectrometer and Stratospheric Aerosol and Gas Experiment instruments confirm many of the findings originally derived from the Dobson record concerning northern midlatitude changes in ozone. The data from many instruments now provide a fairly consistent picture of the change that has occurred in stratospheric ozone levels.

522 citations


Journal ArticleDOI
TL;DR: In this article, an efficient strategy for modeling the land surface boundary in general circulation models (GCMs) is presented which accounts for the effects of vegetation on surface energy fluxes and allows for an arbitrary number of vegetation types to coexist in a grid square.
Abstract: An efficient strategy for modeling the land surface boundary in general circulation models (GCMs) is presented which accounts for the effects of vegetation on surface energy fluxes and allows for an arbitrary number of vegetation types to coexist in a grid square. The GCM grid square is depicted as a 'mosaic' of vegetation 'tiles', with each tile consisting of a single vegetation type. The energy balance equation for each tile follows closely that of a single vegetation version of the simple biosphere (SiB) model of Sellers et al. (1986) but is simplified enough to be written in Penman-Monteith form. Each tile in the square is coupled independently to the GCM atmosphere, and tiles affect each other only through the atmosphere. This coupling strategy differs conceptually from that of models such as SiB that assume a homogeneous mixture of vegetation types within a GCM grid square. A quantitative comparison of the two strategies is presented.

518 citations


Journal ArticleDOI
TL;DR: The explosive June 1991 eruptions of Pinatubo produced the largest sulfur dioxide cloud detected by the Total Ozone Mapping Spectrometer (TOMS) during its 13 years of operation: approximately 20 million tons of SO2, predominantly from the cataclysmic June 15th eruption.
Abstract: The explosive June 1991 eruptions of Mount Pinatubo produced the largest sulfur dioxide cloud detected by the Total Ozone Mapping Spectrometer (TOMS) during its 13 years of operation: approximately 20 million tons of SO2, predominantly from the cataclysmic June 15th eruption. The SO2 cloud observed by the TOMS encircled the earth in about 22 days (about 21 m/s); however, during the first three days the leading edge of the SO2 cloud moved with a speed that averaged about 35 m/s. Compared to the 1982 El Chichon eruptions, Pinatubo outgassed nearly three times the amount of SO2 during its explosive phases. The main cloud straddled the equator within the first two weeks of eruption, whereas the El Chichon cloud remained primarily in the Northern Hemisphere. The measurements indicate that Mount Pinatubo has produced a much larger and perhaps longer-lasting SO2 cloud; thus, climatic responses to the Pinatubo eruption can exceed those of El Chichon.

514 citations


Journal ArticleDOI
TL;DR: The Mars Observer laser altimeter (MOLA) was used to determine globally the topography of Mars at a level suitable for addressing problems in geology and geophysics as mentioned in this paper.
Abstract: The primary objective of the Mars Observer laser altimeter (MOLA) investigation is to determine globally the topography of Mars at a level suitable for addressing problems in geology and geophysics. Secondary objectives are to characterize the 1064-nm wavelength surface reflectivity of Mars to contribute to analyses of global surface mineralogy and seasonal albedo changes, to assist in addressing problems in atmospheric circulation, and to provide geodetic control and topographic context for the assessment of possible future Mars landing sites. The principal components of MOLA are a diode-pumped, neodymium-doped yttrium aluminum garnet laser transmitter that emits 1064-nm wavelength laser pulses, a 0.5-m-diameter telescope, a silicon avalanche photodiode detector, and a time interval unit with 10-ns resolution. MOLA will provide measurements of the topography of Mars within approximately 160-m footprints and a center-to-center along-track foot print spacing of 300 m along the Mars Observer subspacecraft ground track. The elevation measurements will be quantized with 1.5 m vertical resolution before correction for orbit- and pointing induced errors. MOLA profiles will be assembled into a global 0.2 deg x 0.2 deg grid that will be referenced to Mars' center of mass with an absolute accuracy of approximately 30 m. Other data products will include a global grid of topographic gradients, corrected individual profiles, and a global 0.2 deg x 0.2 deg grid of 1064-nm surface reflectivity.

Journal ArticleDOI
TL;DR: In this article, a high-resolution map of the velocity field of the central portion of Ice Stream E in West Antarctica, generated by the displacement-measuring technique, is presented, and a cross-correlation software is found to be a significant improvement over previous manually based photogrammetric methods for velocity measurement, and is far more cost-effective than in situ methods in remote polar areas.

Journal ArticleDOI
TL;DR: In this article, an agreement was achieved between helicopter and satellite measures of surface reflectance to within +/- 1 percent absolute for both the visible and the NIR bands, which translates into a +/- 10 percent error in the estimation in Fpar.
Abstract: Utilizing single-view-angle visible and NIR satellite observations, it was possible to make the necessary radiometric corrections to produce reliable estimates of the simple ratio and the normalized difference vegetation index as inputs to surface evaporation models. Agreement was achieved between helicopter and satellite measures of surface reflectance to within +/-1 percent absolute for both the visible and the NIR bands. A theoretical calculation utilizing radiative transfer models indicates that this translates into a +/-10 percent error in the estimation in Fpar.

Journal ArticleDOI
TL;DR: A nighttime operating Raman lidar system that is designed for the measurement of high vertical and temporal resolution profiles of the water vapor mixing ratio and the aerosol backscattering ratio is described.
Abstract: A nighttime operating Raman lidar system that is designed for the measurement of high vertical and temporal resolution profiles of the water vapor mixing ratio and the aerosol backscattering ratio is described. The theory of the measurements is presented. Particular attention is given to operational problems that have been solved during the development of the system. Data are presented from Sept. 1987 and described in their meteorological context.

Journal ArticleDOI
TL;DR: In this article, the authors reviewed the history and scientific background leading up to FIFE, the experiment design, the scientific teams and equipment involved, and the actual execution of the experiment.
Abstract: This paper reviews the history and scientific background leading up to FIFE, the experiment design, the scientific teams and equipment involved, and the actual execution of the experiment. The experiment was tasked with exploring techniques for utilizing satellite data to quantify important biophysical states and rates for model input. During the intensive field campaigns the fluxes of moisture, heat, carbon dioxide and radiation were measured with airborne and surface equipment in coordination with measurements of atmospheric and surface parameters and satellite overpasses.

Journal ArticleDOI
TL;DR: In this article, a comparative analysis of the 1987 Southern Hemisphere and 1989 Northern Hemisphere lower stratospheric, polar vortex circulation and constituent distributions as observed by the Airborne Antarctic Ozone Experiment, August 17-September 22, 1987, and Airborne Arctic Stratospheric Expedition, January 3-February 19, 1989 aircraft campaigns is presented.
Abstract: The paper develops a comparative picture of the 1987 Southern Hemisphere and 1989 Northern Hemisphere lower stratospheric, polar vortex circulation and constituent distributions as observed by the Airborne Antarctic Ozone Experiment, August 17-September 22, 1987, and Airborne Arctic Stratospheric Expedition, January 3-February 19, 1989 aircraft campaigns. Overall, both polar vortices define a region of highly isolated air, where the exchange of trace gases occurs principally at the vortex edge through erosional wave activity. Aircraft measurement showed that between 50 and 100 mbar, horizontally stratified long-lived tracers such as N2O are displaced downward 2-3 km on the cyclonic (poleward) side of the jet with the meridional tracer gradient sharpest at the jet core. Eddy mixing rates, computed using parcel ensemble statistics, are an order of magnitude or more lower on the cyclonic side of the jet compared to those on the anticyclonic side. Poleward zonal mean meridional flow on the anticyclonic side of the jet terminates in a descent zone at the jet core.

Journal ArticleDOI
TL;DR: In this paper, a model for the formation of the low-boundary layer in which a magnetosheath flux tube reconnects in the north and south beyond the cusp when the IMF is strongly northward is presented.
Abstract: A model for the formation of the low-boundary layer in which a magnetosheath flux tube reconnects in the north and south beyond the cusp when the IMF is strongly northward is presented. For northward IMF the geomagnetic field captures solar wind flux tubes through intermittent reconnection at the cusp region. These newly captured flux tubes shorten and sink into the magnetosphere while the flux tubes reorient themselves as they become assimilated into the magnetosphere. There is no significant acceleration for the particles within the flux tubes. In the magnetosphere the interchange instability disperses the flux tube azimuthally along the magnetopause to form a boundary layer. Subsequent reconnection forms sublayers of the boundary layer and different sublayers represent different ages after reconnection. The interchange instability is stable radially, which keeps sharp boundaries between sublayers and between the boundary layer and magnetosphere.

Journal ArticleDOI
TL;DR: The LOWTRAN-7 code was used to simulate remote sensing of water vapor over 20 different surface covers to optimize the water vapor channel selection and to test the accuracy of the remote sensing method.
Abstract: The LOWTRAN-7 code was used to simulate remote sensing of water vapor over 20 different surface covers. The simulation was used to optimize the water vapor channel selection and to test the accuracy of the remote sensing method. The channel selection minimizes the uncertainty in the derived water vapor due to variations in the spectral dependence of the surface reflectance. The selection also minimizes the sensitivity of the selected channels to possible drift in the channel position. The use of additional MODIS channels reduces the errors due to the effect of haze, subpixel clouds and uncertainties in the temperature profile. Remote sensing of the variation of water vapor from day to day will be more accurate, because the surface reflectances vary slowly with time. The method was applied to Airborne Visible Infrared Imaging Spectrometer (AVIRIS) data. >

Journal ArticleDOI
TL;DR: In this paper, the authors examined current disruption events observed by the Charge Composition Explorer during 1985 and 1986 and found that current disruption was accompanied by large magnetic field turbulence and frequently with reversal in the sign of the field component normal to the neutral sheet.
Abstract: Current disruption events observed by the Charge Composition Explorer during 1985 and 1986 are examined. Occurrence of current disruption was accompanied by large magnetic field turbulence and frequently with reversal in the sign of the field component normal to the neutral sheet. Current disruptions in the near-earth region are found to be typically shortlived (about 1-5 min), and their onsets coincide well with the ground onsets of substorm expansion or intensification in the local time sector of the footpoint of the spacecraft. These events are found almost exclusively close to the field reversal plane of the neutral sheet (within about 0.5 RE). Prior to current disruption the field strength can be reduced to as low as one seventh of the dipole field value and can recover to nearly the dipole value after disruption. The temporal evolution of particle pressure in the near-earth neutral sheet during the onset of current disruption indicates that the current buildup during the substorm growth phase is associated with enhancement in the particle pressure at the neutral sheet.

Journal ArticleDOI
TL;DR: The thermal emission spectrometer (TES) was used for the Mars Observer mission as mentioned in this paper to determine and map the composition of the surface rocks, minerals, and the condensates.
Abstract: The paper describes the thermal emission spectrometer (TES) designed for the Mars Observer mission. The TES measurements of the surface and the atmosphere of Mars will be used to determine and map the composition of the surface rocks, minerals, and the condensates. Examples of information that will be obtained from TES data include mineral abundance maps, condensate properties and their distribution in time and space, aerosol properties and their distribution in time and space, the rock abundance, the polar energy balance, and properties of gaseous species. Where appropriate, these derived parameters will be distributed in the form of gridded map, to allow direct comparison with other derived data sets.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the phenomenon of an urban heat island by the use of Landsat/Thematic Mapper data sets collected over the metropolitan area of Washington, DC, by combining the derived spectral albedos and temperatures, surface energy composites of five surface categories were analyzed.
Abstract: The phenomenon of an urban heat island was investigated by the use of Landsat/Thematic Mapper data sets collected over the metropolitan area of Washington, DC. By combining the derived spectral albedos and temperatures, surface energy composites of five surface categories were analysed. The results indicate that urban heating is attributable to a large excess in heat from the rapidly heating urban surfaces consisting of buildings, asphalt, bare-soil and short grasses. In summer, the symptoms of diurnal heating begin to appear by mid-morning and can be about 10°C warmer than nearby woodlands.

Journal ArticleDOI
TL;DR: Comparisons of results obtained using this microwave scattering model with measurements from deciduous and coniferous forests show good agreement at several frequencies for both like and cross polarizations.
Abstract: A microwave scattering model was developed for layered vegetation based on an iterative solution of the radiative transfer equation up to the second order to account for multiple scattering within the canopy and between the ground and the canopy. The model is designed to operate over a wide frequency range for both deciduous and coniferous forest and to account for the branch size distribution, leaf orientation distribution, and branch orientation distribution for each size. The canopy is modeled as a two-layered medium above a rough interface. The upper layer is the crown, containing leaves, stems, and branches. The lower layer is the trunk region, modeled as randomly positioned cylinders with a preferred orientation distribution above an irregular soil surface. Comparisons of results obtained using this model with measurements from deciduous and coniferous forests show good agreement at several frequencies for both like and cross polarizations. >

Journal ArticleDOI
TL;DR: In this article, the presence of a filamentary structure has been detected in daily global tropospheric water vapor flux values, where the filamentary structures have lengths many times their widths and persist for many days while being translated through the atmosphere.
Abstract: Computations of daily global tropospheric water vapor flux values show the presence of a filamentary structure The filaments, here called rivers, have lengths many times their widths and persist for many days while being translated through the atmosphere They are present in data analyzed for both 1981 and 1991 The water vapor flux maxima coincide quite closely to reflectivity features (averaged from wavelengths of 380 and 360 nm) as revealed by the Total Ozone Mapping Spectrometer (TOMS) It is suggested that the filamentary structure may also be present in other trace constituents

Journal ArticleDOI
TL;DR: In this paper, the authors compared five test fires performed during August and September 1990 in the cerrado (savannal-like region) in central Brazil (three fires) and tropical moist forest (two fires) in the eastern Amazon.
Abstract: Five test fires were performed during August and September 1990 in the cerrado (savannalike region) in central Brazil (three fires) and tropical moist forest (two fires) in the eastern Amazon. This paper details the gases released, the ratios of the gases to each other and to particulate matter, fuel loads, and the fraction consumed (combustion factors), and the fire behavior associated with biomass consumption. Models are presented for evaluating emission factors for CH4, CO2, CO, H2, and particles less than 2.5 micron diam (PM2.5) as a function of combustion efficiency. The ratio of carbon released as CO2 (combustion efficiency) for the cerrado fires averaged 0.94 and for the deforestation fires it decreased from 0.88 for the flaming phase to less than 0.80 during the smoldering phase of combustion. For tropical ecosystems, emissions of most products of incomplete combustion are projected to be lower than previous estimates for savanna ecosystems and somewhat higher for fires used for deforestation purposes.

Journal ArticleDOI
TL;DR: Investigation of the effect of atmospheric constituents on NOAA Advanced Very High Resolution Radiometer (AVHRR) visible and near-infrared data is presented andariant effects and variant effects are shown to dominate the atmospheric effects in the AVHRR solar bands.
Abstract: Investigation of the effect of atmospheric constituents on NOAA Advanced Very High Resolution Radiometer (AVHRR) visible and near-infrared data is presented. The general remote sensing equation, including scattering, absorption, and bidirectional reflectance effects for the AVHRR solar bands, is described. The magnitude of the atmospheric effects for AVHRR solar bands with respect to their impact on the normalized difference vegetation index (NDVI) and the surface bidirection reflectance is examined. Possible approaches for acquiring atmospheric information are discussed, and examples of atmospheric correction of surface reflectance and NDVI are given. Invariant effects (ozone absorption and molecular scattering) and variant effects (water vapor absorption and aerosol scattering) are shown to dominate the atmospheric effects in the AVHRR solar bands. >

Journal ArticleDOI
TL;DR: In this paper, a 3D radiative transfer model was used to investigate the relationship between spectral indices and fraction of absorbed photosynthetically active radiation (PAR) in horizontally heterogeneous vegetation canopies.

Journal ArticleDOI
TL;DR: In this paper, a solar radiation routine is developed for use in climate studies that includes absorption and scattering due to ozone, water vapor, oxygen, carbon dioxide, clouds, and aerosols.
Abstract: A solar radiation routine is developed for use in climate studies that includes absorption and scattering due to ozone, water vapor, oxygen, carbon dioxide, clouds, and aerosols. Rayleigh scattering is also included. Broadband parameterization is used to compute the absorption by water vapor in a clear atmosphere, and the k-distribution method is applied to compute fluxes in a scattering atmosphere. The reflectivity and transmissivity of a scattering layer are computed analytically using the delta-four-stream discrete-ordinate approximation. The two-stream adding method is then applied to compute fluxes for a composite of clear and scattering layers. Compared to the results of high spectral resolution and detailed multiple-scattering calculations, fluxes and heating rate are accurately computed to within a few percent. The high accuracy of the flux and heating-rate calculations is achieved with a reasonable amount of computing time. With the UV and visible region grouped into four bands, this solar radiation routine is useful not only for climate studies but also for studies on photolysis in the upper atmosphere and photosynthesis in the biosphere.

Journal ArticleDOI
TL;DR: In this article, the long-slit optical spectra of 10 Wolf-Rayet galaxies and four other starburst galaxies were obtained using the nebular emission lines and the electron temperatures, electron densities, extinctions, oxygen abundances, mass of ionized hydrogen, and numbers of ionizing photons due to hot stars in these galaxies.
Abstract: We have obtained long-slit optical spectra of 10 Wolf-Rayet galaxies and four other starburst galaxies. Using the nebular emission lines we have determined the electron temperatures, electron densities, extinctions, oxygen abundances, mass of ionized hydrogen, and numbers of ionizing photons due to hot stars in these galaxies. The various forbidden line ratios clearly indicate a stellar origin for the emission-line spectrum. From the flux of the broad He II 4686 A emission feature we have estimated the number of Wolf-Rayet stars present. We have accounted for the contribution of these stars to the total ionizing flux and have calculated the ratio of the number of these stars to the number of O stars. Wolf-Rayet galaxies are among the youngest examples of the starburst phenomenon, which we observed at a propitious moment.

Journal ArticleDOI
TL;DR: In this article, the temperature changes that are possible in inhomogeneous low-density astrophysical plasmas were investigated for a variety of boundary distribution functions that occur in astrophysics, with emphasis placed on the spatial changes in temperature and their correlations with those of the density caused by time-independent, but spatially varying, conservative potentials.
Abstract: The temperature changes that are possible in inhomogeneous low-density astrophysical plasmas were investigated for a variety of boundary distribution functions that occur in astrophysics, with emphasis placed on the spatial changes in temperature and their correlations with those of the density caused by time-independent, but spatially varying, conservative potentials. It is proven that decelerating forces produce equilibrium temperatures that are anticorrelated with densities, provided that the boundary condition is non-Maxwellian, and the proof is extended analytically for a generalized Lorentzian distribution, showing that they obey a polytrope relation with the value of gamma between 0 and l.

Journal ArticleDOI
TL;DR: The large-scale cosmic background anisotropy detected by the COBE Differential Microwave Radiometer (DMR) instrument is compared to the sensitive previous measurements on various angular scales, and to the predictions of a wide variety of models of structure formation driven by gravitational instability as discussed by the authors.
Abstract: The large-scale cosmic background anisotropy detected by the COBE Differential Microwave Radiometer (DMR) instrument is compared to the sensitive previous measurements on various angular scales, and to the predictions of a wide variety of models of structure formation driven by gravitational instability. The observed anisotropy is consistent with all previously measured upper limits and with a number of dynamical models of structure formation. For example, the data agree with an unbiased cold dark matter (CDM) model with H0 = 50 km/s Mpc and Delta-M/M = 1 in a 16 Mpc radius sphere. Other models, such as CDM plus massive neutrinos (hot dark matter (HDM)), or CDM with a nonzero cosmological constant are also consistent with the COBE detection and can provide the extra power seen on 5-10,000 km/s scales.