Low latitude observations of airglow.
Airglow emission analysis from low altitude observations, discussing temporal and spatial variations
SPECTRAL LINE↗
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Results for “spectral emissivity”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The solar X-ray spectrum
The characteristics of X-ray emission from the normal corona are considered, giving attention to questions of spatial and spectral distribution. Aspects of X-ray emission from solar flares are also investigated. Details of X-ray spectroscopy for coronal plasma diagnosis are discussed, taking into account techniques, the diagnosis of equilibrium plasmas, and the diagnosis of nonthermal events. The study of continuum emission and line emission is reported along with investigations of departures from equilibrium.
Culhane, J. L.↗
Fe XIII line in R Aquarii
The emission line of the forbidden coronal transition of Fe XIII at 10,747 A has been detected in data from a spectral survey at R Aquarii. Strong emission lines of He I at 10,830 A and P gamma have been identified; a line at 11,013 A may be He I 3(1)S-6(1)P. It is suggested that the observed iron line is produced by a corona surrounding R Aquarii inter alia. The corona may be the source of the radio emission reported by Gregory and Seaquist (1974).
Zirin, H.↗
Flame radiation and liner heat transfer in a tubular-can combustor
Heat transfer within a combuster were examined. Total and spectral flame radiation in a tubular can combustor at a series of parametric operating conditions was measured. Radiation measurements were taken for a range of inlet air pressures from 0.34 to 2.0 MPa, inlet air temperatures from 533 to 700 K, with two different fuels, Jet-A and ERBS. Measurements of liner temperatures combined with the parametric radiation results allowed a calculation of the combustor liner heat loads. Flame emissivity was determined from the spectral measurements.
Claus, R. W.↗
Flame radiation and linear heat transfer in a tubular can combustor
Heat transfer within a combuster were examined. Total and spectral flame radiation in a tubular can combustor at a series of parameteric operating conditions was measured. Radiation measurements were taken for a range of inlet air pressures from 0.34 to 2.0 MPa, inlet air temperatures from 533 to 700 K, with two different fuels, Jet-A and ERBS. Measurements of linear temperatures combined with the parametric radiation results allowed a calculation of the combustor linear heat loads. Flame emissivity was determined from the spectral measurements. Previously announced in STAR as N84-13188
Claus, R. W.↗
Faraday-Active Fabry-Perot Resonator: Transmission, Reflection, and Emissivity
The propagation of light within a semiconductor Faraday-active Fabry-Perot resonator (FAFR) is investigated theoretically and experimentally. It is shown that an external magnetic field radically changes the angular and spectral characteristics of transmission, reflection and emissivity of the resonator not only for polarized, but also for unpolarized light. Suppression of interference patterns and phase inversion of the interference extrema were observed in both monochromatic and polychromatic light. The investigations were carried out for the plane-parallel plates of n-InAs in the spectral range of free charge carrier absorption. The results can be used to create new controllable optical and spectroscopic devices for investigation of Faraday-active material properties and for control of parameters of plane-parallel layers and structures.
Liptuga, Anatoliy↗
On-Orbit Calibration Assessment of NOAA-21 VIIRS Thermal Emissive Bands and Implications for JPSS-4 VIIRS
The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument onboard the NOAA-21 (N21) satellite has been successfully operating for over three years collecting valuable scientific measurements. A large suite of weather forecasting models and scientific research applications are supported with the VIIRS measurements from N21 combined with those acquired from the VIIRS instrument onboard the S-NPP and NOAA-20 spacecraft. Among the 22 VIIRS spectral bands, there are seven thermal emissive bands (TEB) covering the 3.7 to 12.2 µm spectral range at two different spatial resolutions. The VIIRS TEB detectors are calibrated onboard using a blackbody at a controlled temperature and a space view for background signal measurement. In this paper, we discuss the on-orbit performance of the N21 VIIRS TEB using various parameters such as the detector gain, noise, and offset. This on-orbit assessment provides critical insights into instrument behavior and calibration performance that will inform pre-launch testing and post-launch validation strategies for the upcoming JPSS-4 VIIRS mission scheduled for launch in 2027. The methodologies and lessons learned from characterizing the N21 TEB performance will enable more efficient and comprehensive radiometric assessment of the next VIIRS instrument. Specific focus is placed on identifying performance trends and anomaly signatures observed during the N21 commissioning phase that can enhance the JPSS4 instrument checkout procedures and accelerate the transition to routine on-orbit operations. The established performance baselines and uncertainty estimates will serve as an acceptance criterion for the JPSS-4 commissioning activities, ensuring mission readiness and data continuity for operational users.
Amit Angal↗
Extended infrared emission around IRAS 21282 + 5050
Multiaperture 3-4-micron spectra along with K- and L-band images of the compact planetary nebula IRAS 21282 + 5050 show a 5 arcsec - 20 arcsec diameter nebula with structure similar to many other planetary nebulae. The spectral observations and the L-band image show evidence for extended PAH emission out to a radius of 20 arcsec, while the K-band image shows a 5 arcsec diameter nebula. An observed linear increase of integrated brightness with aperture size at L band implies a 1/r exp 2 volume emissivity for a spherically symmetric model. The spectral similarity of the emission in the small and large apertures suggests fluorescent emission by the PAHs. If the observed emission is from PAHs which formed during the planetary nebulae stage of IRAs 21282 + 5050, then PAHs have been forming for not less than 3000 yr. If the PAH emission is from material produced during the earlier red giant phase, then the formation time frame was much longer. The morphological and spectral similarity of IRAS 21282 + 5050 to many other planetary nebulae suggests that this phenomenon may be widespread, and that planetary nebulae may be a significant source of interstellar PAHs.
Bregman, Jesse D.↗
Spectra of plages on the sun and stars. I - Ca II H and K lines. II - The H I H-alpha line
Spectra of solar plages are used to define indices of plage properties in the Ca II H and K line region. Chromospheric and photospheric emission is examined and the details of height structure are noted. It is found that: (1) all spectral lines are weakened in plages except those of H I, He I, and some ionized metals; (2) the irradiation contribution from a plage is roughly constant throughout its disk passage; and (3) plage emission distorts spectral and photometric measures of stellar gravity, metallicity, and temperature.
Labonte, B. J.↗
Detection of a weak maser emission pedestal associated with the SiO maser
Results are reported for high-spectral-resolution observations of the v = 1, J = 1-0 SiO maser sources at 43,122.027 MHz (6.95 mm wavelength) associated with the variable stars Omega Cet, NML Tau, VY CMa, R Leo, W Hya, VX Sgr, NML Cyg, and R Cas. A weak underlying maser emission pedestal is clearly observed in the spectra of all but NML Cyg and R Cas. The data indicate that the underlying pedestal of SiO emission appears to originate in a shell-like region around the star, has a thermal appearance even though it must be due to weak maser emission, and appears to be part of the spectral signature of SiO maser emission from late-type stars. It is found that the center velocities of the pedestals may be used to determine stellar radial velocities. Observations of large-scale time variations in the intensity of the Ori A SiO maser and the detection of weak maser pedestals associated with each of the two strong emission-feature groups in Orion are also discussed. It is suggested that the Orion molecular cloud might contain two late-type long-period variable stars that may be semiregular variables.
Snyder, L. E.↗
The 27-28 October 1986 FIRE IFO cirrus case study - Spectral properties of cirrus clouds in the 8-12 micron window
Lidar and radiometric observations are employed for detecting the presence of cirrus and describing their radiative properties. The study focuses on observations of the radiative properties of cirrus clouds within the 8-12 micron spectral region. The instrumentation that achieved the spectral radiance observations used in this study is described. Results are presented for October 28, 1986 FIRE case study day in terms of brightness temperature differences, cirrus effective emissivities, and the gross microphysical characteristics of the observed clouds. The HIS and lidar observations were combined to derive the spectral effective beam emissivity of the cirrus clouds. Fifty percent of clouds on this day displayed a spectral variation of effective beam emissivity from 2-10 percent. These differences, in conjunction with large differences in the HIS observed brightness temperatures, indicate that cirrus clouds cannot be considered gray in the 8-12 micron region. Also, the derived spectral transmittance of the cloud is used to infer the effective radii of the particle size distribution.
Ackerman, Steven A.↗
Localized interlayer excitons in MoSe 2 –WSe 2 heterostructures without a moiré potential
Interlayer excitons (IXs) in MoSe 2 –WSe 2 heterobilayers have generated interest as highly tunable light emitters in transition metal dichalcogenide (TMD) heterostructures. Previous reports of spectrally narrow (<1 meV) photoluminescence (PL) emission lines at low temperature have been attributed to IXs localized by the moiré potential between the TMD layers. We show that spectrally narrow IX PL lines are present even when the moiré potential is suppressed by inserting a bilayer hexagonal boron nitride (hBN) spacer between the TMD layers. We compare the doping, electric field, magnetic field, and temperature dependence of IXs in a directly contacted MoSe 2 –WSe 2 region to those in a region separated by bilayer hBN. The doping, electric field, and temperature dependence of the narrow IX lines are similar for both regions, but their excitonic g-factors have opposite signs, indicating that the origin of narrow IX PL is not the moiré potential.
36 MATERIALS SCIENCE↗
Broadband electrostatic noise and field-aligned currents in Jupiter's middle magnetosphere
Voyager 1 plasma wave observations have revealed the presence of an impulsive electrostatic emission localized to the Jovian middle magnetosphere that appears on the edges of the plasma sheet. This plasma mode has the same spectral and morphological characteristics of an emission that has been extensively studied in the earth's magnetosphere and has been associated with the presence of field-aligned currents. The results of a detailed study of the properties of this Jovian emission are presented by using comparisons with terrestrial observations as a basis for mode identification. The occurrence regions of the waves are compared with the measured magnetic field configuration to establish a correspondence with the plasma sheet. It is argued that this is a quasi-permanent global system of field-aligned currents linking the ionosphere of Jupiter to the middle magnetosphere, which powers energetic plasma heating processes occurring there. On the basis of knowledge of the consequences of field-aligned currents in the terrestrial magnetosphere, a scenario for acceleration/precipitation of inverted V electrons, concomitant aurorae, and energetic (approximately 10 keV) proton deposition into the middle magnetosphere resulting from field-aligned potential drops associated with this current system is suggested.
Barbosa, D. D.↗
Radio and X-Ray Observations of the 1998 Outburst of the Recurrent X-Ray Transient 4U 1630-47
We report radio (VLA and ATCA), soft X-ray (RXTE ASM), and hard X-ray (CGRO BATSE) observations of a 1998 outburst in the recurring X-ray transient 4U 1630-47 where radio emission was detected for the first time. The radio observations identify the position of 4U 1630-47 to within 1". Because the radio emission is optically thin with a spectral index of approximately -0.6 during the rise and approximately -1 during the peak and decay of the initial radio event, the emission is probably coming from an optically thin radio jet ejected over a period of time. The 20-100 keV emission first appeared 1998 January 28 (MJD 50841), the 2-12 keV emission first appeared February 3 (MJD 50847), and the first radio emission was detected February 12.6 (MJD 50856.6). The rise of the radio emission probably began about February 7 (MJD 50851) when the X-rays were in a very hard, fluctuating hardness state, just before changing to a softer, more stable hardness state.
Hjellming, R. M.↗
Formation and Destruction Processes of Interstellar Dust: From Organic Molecules to carbonaceous Grains
The study of the formation and destruction processes of cosmic dust is essential to understand and to quantify the budget of extraterrestrial organic molecules. interstellar dust presents a continuous size distribution from large molecules, radicals and ions to nanometer-sized particles to micron-sized grains. The lower end of the dust size distribution is thought to be responsible for the ubiquitous spectral features that are seen in emission in the IR (UIBs) and in absorption in the visible (DIBs). The higher end of the dust-size distribution is thought to be responsible for the continuum emission plateau that is seen in the IR and for the strong absorption seen in the interstellar UV extinction curve. All these spectral signatures are characteristic of cosmic organic materials that are ubiquitous and present in various forms from gas-phase molecules to solid-state grains. Although dust with all its components plays an important role in the evolution of interstellar chemistry and in the formation of organic molecules, little is known on the formation and destruction processes of dust. Recent space observations in the UV (HST) and in the IR (ISO) help place size constraints on the molecular component of carbonaceous IS dust and indicate that small (ie., subnanometer) PAHs cannot contribute significantly to the IS features in the UV and in the IR. Studies of large molecular and nano-sized IS dust analogs formed from PAH precursors have been performed in our laboratory under conditions that simulate diffuse ISM environments (the particles are cold -100 K vibrational energy, isolated in the gas phase and exposed to a high-energy discharge environment in a cold plasma). The species (molecules, molecular fragments, ions, nanoparticles, etc) formed in the pulsed discharge nozzle (PDN) plasma source are detected with a high-sensitivity cavity ring-down spectrometer (CRDS). We will present new experimental results that indicate that nanoparticles are generated in the plasma. From these unique measurements, we derive information on the nature, the size and the structure of interstellar dust particles, the growth and the destruction processes of IS dust and the resulting budget of extraterrestrial organic molecules.
Salama, F.↗
Non-Detection of L-Band Line Emission from the Exoplanet HD 189733b
We attempt to confirm bright non-local thermodynamic equilibrium (non-LTE) emission from the exoplanet HD 189733b at 3.25 microns, as recently reported by Swain et al. based on observations at low spectral resolving power (lambda/delta lambda approximately equals 30). Non-LTE emission lines from gas in an exoplanet atmosphere will not be significantly broadened by collisions, so the measured emission intensity per resolution element must be substantially brighter when observed at high spectral resolving power. We observed the planet before, during, and after a secondary eclipse event at a resolving power lambda/delta lambda equals 27,000 using the NIRSPEC spectrometer on the Keck II telescope. Our spectra cover a spectral window near the peak found by Swain et al., and we compare emission cases that could account for the magnitude and wavelength dependence of the Swain et al. result with our final spectral residuals. To model the expected line emission, we use a general non-equilibrium formulation to synthesize emission features from all plausible molecules that emit in this spectral region. In every case, we detect no line emission to a high degree of confidence. After considering possible explanations for the Swain et at., results and the disparity with our own data, we conclude that an astrophysical source for the putative non-LTE emission is unlikely. We note that the wavelength dependence of the signal seen by Swain et al. closely matches the 2(sub 1/2) band of water vapor at 300 K, and we suggest that an imperfect correction for telluric water is the source of the feature claimed by Swain et al.
Mandell, Avi M.↗
Spectrographic observations of comet West /1975 n/
The spectrum of comet West (1975 n) was recorded on March 7 and 11, 1976, in the wavelength interval from 5700 to 8200 A at an intermediate resolution. One hundred twenty-two emission lines are reported, with 78 lines having identifications with spectral features of NH2, H2O(+), C2, O I forbidden emission, and Na I.
Gary, G. A.↗
Evidence for inhomogeneous thermal sources of two similar solar spike event of 1978, May 5 and December 4
Two short duration single spike events of 1978 May 5 and December 4 exhibit similar time profiles in the microwave and hard X-ray ranges, indicating emission from compact sources. Microwave spectral observations exhibit inhomogeneities present in the source parameters. The existence of fine time structures in the microwave time profiles at 10.4 GHz from Berne are interpreted as a signature of the dynamics of a disturbance travelling through the souce at the ion-sound speed. Stereoscopic observations with the hard X-ray detector on the solar orbiter, Helios-2, and the Berne microwave antennae do not indicate any time lag or differences in the time profiles during the impulsive phase. This is taken as evidence for the absence of directionality of emission making beam models unlikely for short duration single spike events.
Wiehl, H. J.↗