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NASA NTRS2014

Interstellar Organics, the Solar Nebula, and Saturn's Satellite Phoebe

The diffuse interstellar medium inventory of organic material (Pendleton et al. 1994, Pendleton Allamandola 2002) was likely incorporated into the molecular cloud in which the solar nebula condensed. This provided the feedstock for the formation of the Sun, major planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Saturn's satellites Phoebe, Iapetus, and Hyperion open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS - Visible and Infrared Mapping Spectrometer) on the Cassini spacecraft at Saturn. Phoebe (mean diameter 213 kilometers) is a former TNO now orbiting Saturn. VIMS spectral maps of Phoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and aliphatic hydrocarbon (CH2, CH3) absorption bands (3.2-3.6 meters). Phoebe is the source of a huge debris ring encircling Saturn, and from which particles (5-20 meter size) spiral inward toward Saturn. They encounter Iapetus and Hyperion where they mix with and blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aromatic CH is 10 times as abundant as aliphatic CH2 plus CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, comet particles, and in carbonaceous meteorites (Cruikshank et al. 2013). A similar excess of aromatics over aliphatics is seen in the qualitative analysis of Hyperion and Phoebe itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 4, which is larger than the value found in the diffuse ISM (InterStellar Matter - (2-2.5). Insofar as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inventory, it can be key to understanding the content and degree of processing of that nebular material. There are other Phoebe-like TNOs that are presently beyond our ability to study in the organic spectral region, but JWST (James Webb Space Telescope) will open that possibility for a number of objects. We now need to explore and understand the connection of this organic-bearing Solar System material to the solar nebula and the inventory of ISM (Interstellar Medium) materials incorporated therein.

Phoebe↗

NASA NTRS2014

Interstellar Organics, the Solar Nebula, and Saturn's Satellite Phoebe

The diffuse interstellar medium inventory of organic material (Pendleton et al. 1994, Pendleton & Allamandola 2002) was likely incorporated into the molecular cloud in which the solar nebula condensed. This provided the feedstock for the formation of the Sun, major planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Saturn's satellites Phoebe, Iapetus, and Hyperion open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS) on the Cassini spacecraft at Saturn. Phoebe (mean diameter 213 km) is a former TNO now orbiting Saurn. VIMS spaectral maps of PHoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and alophatic hydrocarbon (CH2, CH3) absorption bands (3.2-3.6 micrometers). Phoebe is the source of a huge debris ring encircling Saturn, and from which particles (approximately 5-20 micrometer size) spiral inward toward Saturn. They encounter Iapetus and Hperion where they mix with and blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aromatic CH is approximately 10 times as abundant as aliphatic CH2+CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, comet particles, ad in carbonaceous meteorites (Cruikshank et al. 2013). A similar excess of aromatics over aliphatics is seen in the qualitative analysis of Hyperion and Phoebe itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 approximately 4, which is larger than the value found in the diffuse ISM (approximately 2-2.5). In so far as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inventory, it can be key to understanding the content and degree of procesing of the nebular material. There are other Phoebe-like TNOs that are presently beyond our ability to study in the organic spectral region, but JWST will open that possibility for a number of objects. We now need to explore and understand the connection of this organic-bearing Solar System material to the solar nebula the the inventory of ISM materials incorporated therein.

Interstellar↗

NASA NTRS1986

The propagation of solar flare particles in a coronal loop

A time-dependent diffusion equation with velocity-dependent diffusion and energy-loss coefficients was solved for the case where energetic solar particles are injected into a coronal loop and then diffuse out the ends of the loop into the lower corona/chromosphere. The solution yields for the case of relativistic electrons, precipitation rates and populations which are necessary for calculating thick and thin target X-ray emission. It follows that the thick target emission is necessarily delayed with respect to the particle acceleration on injection by more than the mere travel time of the particle over the loop length. In addition the time-dependent electron population at the top of the loop is calculated. This is useful in estimating the resulting micron-wave emission. The results show relative timing differences in the different emission processes which are functions of particle species, energy and the point of injection of the particles into the loop. Equivalent quantities are calculated for non-relativistic protons.

Ryan, J. M.↗

NASA NTRS1980

A clear-sky spectral solar radiation model for snow-covered mountainous terrain

A clear-sky spectral solar radiation model for direct and diffuse fluxes, combined with topographic calculations from digital terrain data, computes either incident, net, or reflected solar radiation at any point on a snow surface in mountainous terrain. The radiation may be integrated over any wavelength range from 250 to 5000 nm, or over any time step. Atmospheric attenuation parameters are ozone, water vapor, the Angstrom turbidity coefficient and exponent, and the absorptance to reflectance ratio of the atmospheric aerosols. The model derives these, from measurements which may contain both systematic and random errors, by finding the least squares solution to an overdetermined set of nonlinear equations. For calculations over a specified area, it employs table look-up procedures, so that computation speed for the spectral model approaches that for a lumped model. Thus it may be useful as part of a snow surface energy budget calculation over a drainage basin.

Dozier, J.↗

NASA NTRS1977

Solar particle propagation from 1 to 5 AU

The radial variation of the interplanetary propagation of solar cosmic rays is investigated on a grand scale by performing a statistical analysis of charged-particle data obtained by Pioneers 10 and 11 from launch to Jovian encounter (i.e., at distances of 1 to 5 AU). A numerical propagation model is adopted which includes diffusion, convection, and adiabatic deceleration, as well as a variable power-law diffusion coefficient. The study of solar particle events is carried out by analyzing individually each of five key parameters that are uniquely defined in each solar particle event: the time to maximum flux starting from the initial release at the sun, the anisotropy at the time to maximum flux, the flux at that time, the time width of the event at half the flux at the time to maximum, and the decay time. Combined results for the proton energy ranges from 3.4 to 5.2 MeV and 24 to 30 MeV are presented, the average radial diffusion coefficients between 1 and 5 AU are determined for each energy range, and it is found that the combination of a near-impusive injection with a temporally constant spectral index produces a reasonably good fit to the high-energy data but not as good a fit to the low-energy data. Implications of the results obtained are discussed for cosmic-ray propagation theory, solar modulation studies, and interplanetary acceleration of solar particles.

Zwickl, R. D.↗

NASA NTRS1986

Particle acceleration at a termination shock. I - Application to the solar wind and the anomalous component

The results of a numerical study of the diffusive acceleration of charged particles at the termination shock of the solar wind are reported. In the model a realistic magnetic field structure is employed which is similar to that observed in the solar wind. In addition to causing spatial variation of the diffusion tensor, a major effect of the magnetic field is to cause guiding-center drifts of the accelerated particles, both in the solar wind and at the shock. It is demonstrated that the inclusion of the drifts has a large effect on the acceleration. It is concluded, furthermore, that acceleration at the termination shock, in conjunction with drifts, can explain several observed features of the anomalous component.

Jokipii, J. R.↗

NASA NTRS1973

Aerosol scattering of ultraviolet sunlight in the tropical maritime atmosphere

The effects of atmospheric aerosol scattering on the vertical profile of solar ultraviolet radiation are investigated. Measurements of diffuse and total ultraviolet radiation were made using a rocketborne optical sonde in the marine atmosphere of Antigua. During observations, the sun was at zenith. Vertical profiles of directly transmitted solar radiation were calculated by subtraction of the diffuse component from the total radiance. Using these values of direct downward solar UV-flux, the optical thickness of the atmosphere was derived as a function of altitude. Absorption by ozone was also considered. In the troposphere the values of observed optical thickness were in general equal to or lower than those expected theoretically from Rayleigh scattering alone. The measured radiation profiles were compared with those computed for a multiple scattering model atmosphere. Some computations regarding the interaction of UV-sunlight with maritime aerosols are presented.

Ghazi, A.↗

NASA NTRS1981

Effects of diffusion and mass flows on C IV and Si IV lines formed in the solar atmosphere

A model for the transition region is derived from an initial interpretation of EUV observations, assuming ionization equilibrium and constant elemental abundance with height. The effects of diffusion and mass flows are then included in the initial model and the emergent profiles of several C IV and Si IV lines are computed. It is found that diffusion and mass flows have a strong effect on both the emergent intensity and spectral shape of these lines. Diffusion acts to deplete the transition region of heavy ions to an extent which depends on the detailed temperature and density structure. The net effect is a weighting of the coronal emission relative to that in the transition. On the basis of the results, it is suggested that the downflows observed in the network in lines of C IV and Si IV could be due to gravitational settling of the ions following their injection, via diffusion, into the corona from spicules. When flows are superposed on the basic diffusion model, the rapid change in elemental abundance characteristic of the model is virtually eliminated and the coronal contribution to the emission in C IV and Si IV lines becomes negligible relative to that in the transition region. Flows have a strong effect on the computed line intensities and introduce large asymmetries into the line shapes.

Roussel-Dupre, R.↗

NASA NTRS1984

Excimer laser annealing to fabricate low cost solar cells

The objective is to show whether or not pulsed excimer laser annealing (PELA) of ion-implanted junctions is a cost effective replacement for diffused junctions in fabricating crystalline silicon solar cells. The preliminary economic analysis completed shows that the use of PELA to fabricate both the front junction and back surface field (BSF) would cost approximately 35 cents per peak watt (Wp), compared to a cost of 15 cents/Wp for diffusion, aluminum BSF and an extra cleaning step in the baseline process. The cost advantage of the PELA process depends on improving the average cell efficiency from 14% to 16%, which would lower the overall cost of the module by about 15 cents/Wp. An optimized PELA process compatible with commercial production is to be developed, and increased cell efficiency with sufficient product for adequate statistical analysis demonstrated. An excimer laser annealing station was set-up and made operational. The first experiment used 248 nm radiation to anneal phosphorus implants in polished and texture-etched silicon.

Source record↗

NASA NTRS2003

Solar System Connections to the Organic Material In the ISM

The organic component of the interstellar medium (ISM) has relevance to the formation of the early solar nebula, since our solar system formed out of ISM material. Comparisons of near infrared spectra of the diffuse ISM dust with those of primitive solar system bodies (such as comets and meteorites) show a remarkable similarity, suggesting that perhaps some of the interstellar organic material made its way, unaltered, into our solar system. Tracing the interstellar organic material is necessary to understand how these materials may be important links in the development of prebiotic phenomena. Studies of the ISM reveal that the organic refractory component of the diffuse ISM is largely hydrocarbon in nature, possessing little N or O, with carbon distributed between the aromatic and aliphatic forms. There is a strong similarity in the near IR spectra of the diffuse ISM (the 3.4 micron hydrocarbon bands) and those seen in the Murchison and Orgueil meteorites, however, detailed comparisons at longer wavelengths reveal critical dissimilarities. Here we will present comparisons and discussion of relevant spectra. As we continue to explore, we will gain insight into the connection between planetesimals in the solar system and chemistry in the dusty space between the stars.

Pendleton, Yvonne J.↗

NASA NTRS1995

Energization in regions of CIRs unconnected to shocks are probably not the result of cross-field transport

Corotating energetic ion populations (CEIPs) associated with the forward and reverse shocks of corotating interaction regions (CIRs) are observed in CIRs at places where models say are magnetically unconnected to either shock. Such disconnections between CEIPs and shocks are common and have been documented with data from Pioneers 10 and 11 and confirmed with data from Ulysses. They pose a problem for models that account for these CEIPs in terms of ion energization at the shocks followed by ion propagation along field lines. Two possible resolutions to this problem have been suggested: diffusion of the ions across field lines and extension of the ion energization process to regions beyond the shock waves. Here we quantitatively examine the first of these possibilities. We give the Green's function solution to the convection-diffusion equation applied to idealized CIR geometry, with a source at the reverse shock -- the main producer of CEIPs. Two kinds of diffusion are considered: resonant diffusion and stochastic field line diffusion. We find that for resonant diffusion the computed ratio is many orders of magnitudes below the observed ratio. For stochastic field line diffusion, the computed ratio approximately equals the observed ratio if a diffusion coefficient appropriate to the free solar wind is used. It is several orders of magnitude below the observed ratio, however, if a diffusion coefficient appropriate to CIRs is used. We conclude that cross-field diffusion probably does not account for the presence of energetic ions in regions of CIRs that are magnetically unconnected to its shock waves. We suggest that the alternative possibility -- the energetic ions in regions magnetically unconnected to shocks result from an acceleration process that is independent of shocks -- be pursued to the point where quantitative tests can be performed.

Intriligator, Devrie S.↗

NASA NTRS1971

Recent progress in the remote detection of vapours and gaseous pollutants

Work has been continuing on the correlation spectrometry techniques described at previous remote sensing symposiums. Advances in the techniques are described which enable accurate quantitative measurements of diffused atmospheric gases to be made using controlled light sources, accurate quantitative measurements of gas clouds relative to background using solar illumination and semi-quantitation measurements of well diffused atmospheric gases using solar illumination. Specific applications of these techniques are described including preliminary results of a high altitude balloon experiment designed to test the feasibility of measuring pollution at the earth's surface from high altitude balloons and satellites.

Moffat, A. J.↗

NASA NTRS1987

Diffusive shock acceleration - Comparison of a unified shock model to bow shock observations

A comparison is made between recent AMPTE/IRM observations of diffuse ions detected upstream of the earth's bow shock when the interplanetary magnetic field was nearly parallel to the solar wind direction and a known collisionless quasi-parallel shock model. These observations, which provide the proton spectrum for all of velocity space, give a direct measure of the shock acceleration efficiency and show how thermal solar winds are injected into the diffusive shock acceleration mechanism. The model accurately describes the proton spectrum; moreover, it predicts the shock structure, the complete particle spectrum, the relative velocity distributions of different ion species in the down stream region, and the enhancement of heavy ions over protons relative to the unshocked solar wind.

Ellison, Donald C.↗

NASA NTRS2014

Interstellar Organics, the Solar Nebula, and Saturn's Satellite Phoebe

The diffuse interstellar medium inventory of organic material (Pendleton et al. 1994, Pe 2002) was likely incorporated into the molecular cloud in which the solar nebula condensed. This provided the feedstock for the fo planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Saturn's satellites Phoeb open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS) on the Cass Phoebe (mean diameter 213 km) is a former TNO now orbiting Saturn. VIMS spectral maps of Phoebe's surface reveal a complex consisting of prominent aromatic (CH) and aliphatic hydrocarbon (CH2, CH3) absorption bands (3.2-3.6 μm). Phoebe is the source encircling Saturn, and from which particles (~5-20 μm size) spiral inward toward Saturn. They encounter Iapetus and Hyperion wh blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aroma abundant as aliphatic CH2+CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, com carbonaceous meteorites (Cruikshank et al. 2013). A similar excess of aromatics over aliphatics is seen in the qualitative analysis o itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 ~4, which is larger than the value found in the di as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inv understanding the content and degree of processing of that nebular material. There are other Phoebe-like TNOs that are presently b in the organic spectral region, but JWST will open that possibility for a number of objects. We now need to explore and understand organic-bearing Solar System material to the solar nebula and the inventory of ISM materials incorporated therein.

Interstellar↗

NASA NTRS1972

A self-consistent model for Jupiter's radiation belts

The solar wind is assumed to be a sufficient source for the radiation belts of Jupiter, with radial diffusion as the process for getting the solar wind fluxes into the inner regions of the radiation belts. The process of a radial diffusion source is combined with pitch-angle diffusion losses to estimate an upper limit to the proton and electron fluxes. The upper limit to the integral proton and electron fluxes in the outer zone scale as L to the -6th power throughout the outer zone, assuming that the magnetic moment is conserved. It is important that these fluxes are above the stably trapped flux levels in the outer regions of the belts; the instability will work because the energies of the particles are above the critical value required.

Thorne, R. M.↗

NASA NTRS1989

Photovoltaic power system operation in the Mars environment

Detailed information on the environmental conditions on Mars are very desirable for the design of photovoltaic systems for establishing outposts on the Martian surface. The variation of solar insolation (global, direct, and diffuse) at the Viking lander's locations is addressed. It can be used, to a first approximation, for other latitudes. The radiation data is based on measured optical depth of the Martian atmosphere derived from images taken of the sun with a special diode on the Viking cameras; and computation based on multiple wavelength and multiple scattering of the solar radiation. The data are used to make estimates of photovoltaic system power, area and mass for a surface power system using regenerative fuel cells for storage and nighttime operation.

Appelbaum, Joseph↗

NASA NTRS1989

Photovoltaic power system operation in the Mars environment

Appelbaum, Joseph↗

NASA NTRS1967

Process controls introduction of selected impurities into semiconductor wafers

Modified three-step process controls the concentration of lithium diffused as a dopant into the base region of a diffused n-on-p silicon solar cell wafer. Part of the surface layer of the base region of the p-type silicon containing the diffused dopant is removed, prior to redistributing the remaining portion of the dopant into the bulk of the wafer.

Bartholomay, W. C.↗