Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “DAYGLOW”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Linewidth studies on the the NI(4S-4P) resonance multiplet

Doppler broadening of the 8691, 8212, and 1200-A multiplet lines of N I is investigated experimentally, and its implications for the interpretation of the earth's 1200-A UV dayglow are considered. A regulated 100-eV, 1-mA electron beam is passed through N2 at 300 K and about 0.0005 torr flowing through a collision chamber within a UHV system, and the radiation emitted is observed with a temperature-stabilized short-focal length monochromator with a bandpass of 0.2 A in the IR and an effective UV resolution (in second-order operation with a 3600-groove/mm plane grating) of about 0.04 A. Both the IR and VUV lines are found to be broadened to about 25 times the thermal Doppler linewidth, with the IR transitions accounting for more than half of the total N(4P) cross section at 100 eV. The kinetic energy of the N(4P) atoms produced by dissociative excitation is such that their 1200-A resonance radiation (2p2 3s4P - 2p3 4SO) would be optically thin in the upper atmosphere, contrary to what has been observed. A need to revise some aspects of current UV-dayglow models is identified.

Erdman, P. W.↗
NASA NTRS1986

On the influx of small comets into the earth's upper atmosphere. I - Observations. II - Interpretation

The atmospheric dayglow in the atomic oxygen emissions at 130.4 nm observed by the spin-scan photometer of the Dynamics Explorer 1 satellite is analyzed. Large, transient decreases in dayglow intensities of 5-20 percent are detected; the decreases referred to as an atmospheric hole or dark spot covers an area of 2000 sq km and 10 atmospheric holes/min occur in the dayside upper atmosphere. The diurnal variation of the occurrence rate is examined; the relation between the variation and the influx of extraterrestrial objects is studied. These cometlike objects are composed of water snow or clathrate in the form of a fluffy aggregate. The effects caused by the impact of the comet with the earth's atmosphere are investigated.

Frank, L. A.↗
NASA NTRS1989

Calibration of the Berkeley EUV Airglow Rocket Spectrometer

The Berkeley Extreme-ultraviolet Airglow Rocket Spectrometer (BEARS), a multiinstrument sounding rocket payload, made comprehensive measurements of the earth's dayglow. The primary instruments consisted of two near-normal Rowland mount spectrometers: one channel to measure several atomic oxygen features at high spectral resolution (about 1.5 A) in the band passes 980-1040 and 1300-1360 A, and the other to measure EUV dayglow and the solar EUV simultaneously in a much broader bandpass (250-1150 A) at moderate resolution (about 10 A). The payload also included a hydrogen Lyman-alpha photometer to monitor the solar irradiance and goecoronal emissions. The instrument was calibrated at the EUV calibration facility at the University of California at Berkeley, and was subsequently launched successfully on September 30, 1988 aboard a four-stage experimental sounding rocket, Black Brant XII flight 12.041 WT. The calibration procedure and resulting data are presented.

Cotton, Daniel M.↗
NASA NTRS1991

Report on the search for atmospheric holes using airs image data

Frank et al (1986) presented a very controversial hypothesis which states that the Earth is being bombarded by water-vapor clouds resulting from the disruption and vaporization of small comets. This hypothesis was based on single-pixel intensity decreases in the images of the earth's dayglow emissions at vacuum-ultraviolet (VUV) wavelengths using the DE-1 imager. These dark spots, or atmospheric holes, are hypothesized to be the result of VUV absorption by a water-vapor cloud between the imager and the dayglow-emitting region. Examined here is the VUV data set from the Auroral Ionospheric Remote Sensor (AIRS) instrument that was flown on the Polar BEAR satellite. AIRS was uniquely situated to test this hypothesis. Due to the altitude of the sensor, the holes should show multi-pixel intensity decreases in a scan line. A statistical estimate indicated that sufficient 130.4-nm data from AIRS existed to detect eight to nine such holes, but none was detected. The probability of this occurring is less than 1.0 x 10(exp -4). A statistical estimate indicated that sufficient 135.6-nm data from AIRS existed to detect approx. 2 holes, and two ambiguous cases are shown. In spite of the two ambiguous cases, the 135.6-nm data did not show clear support for the small-comet hypothesis. The 130.4-nm data clearly do not support the small-comet hypothesis.

Reinleitner, Lee A.↗
NASA NTRS1993

An evaluation of the rate of absorption of solar radiation in the O2(X3Sigma-g - b1Sigma-g) transition

The rate at which molecular oxygen absorbs radiation in the O2(X3Sigma-g - b1Sigma-g) transition is calculated using a line-by-line radiative transfer model. This rate is critical to the determination of the population of the O2(b1Sigma-g) state required for studies of the O2(b1Sigma-g - X3Sigma-g) dayglow, the O2(a1Delta-g - X3Sigma-g) dayglow, and possibly the rates of oxidation of H2 and N2O. Previous evaluations of this rate (which is sometimes called the g-factor) have significantly overestimated its value. The rate is tabulated as a function of altitude, pressure, and solar zenith angle.

Mlynczak, Martin G.↗
NASA NTRS1994

Observations of the far ultraviolet airflow by the Ultraviolet Limb Imaging experiment on STS-39

The Ultraviolet Limb Imaging (UVLIM) experiment flew on STS-39 in the spring of 1991 to observe the Earth's thermospheric airglow and included a far ultraviolet (1080-1800 A) spectrometer. We present first results from this spectrometer, including a spectroscopic analysis at 6-A resolution of H, O, N, and N2 dayglow emissions and modeling of the observed limb-scan profiles of dayglow emissions. The observed N2 Lyman-Birge-Hopfield (LBH) emission reflects a vibrational population distribution in the a(1 Pi)(sub g) state that differs significantly from those predicted for direct electron excitation and excitation with cascade from the a('1 Sigma)(sub u)(-) and w(1 Delta)(sub u) states. The vibrational population distribution and LBH brightness suggest a total cascade rate 45% that of direct excitation, in contrast to laboratory measurements. For the first time, pronounced limb brightening is observed in both the N I lambda 1200 limb emission profiles, as expected for emissions excited by N2 dissociation which produces kinetically fast N fragments; however, optically thick components of these features are also observed. Preliminary modeling of the OI lambda 1356, HI lambda 1216, and OI lambda 1304 and OI lambda 1641 emissions agrees to within roughly 10% of the observed limb-scan profiles, but the models underestimate the N2 LBH profiles by a factor of 1.4-1.6, consistent with the inferred cascade effect. Other findings include: an OI lambda 1152/lambda 1356 intensity ratio that is inconsistent with the large cascade contribution to OI lambda 1356 from np 5P states required by laboratory and nightglow observations; nightglow observations of the tropical ultraviolet arcs exhibit a wide range of OI lambda 1356/lambda 1304 intensity ratios and illustrate the complicated observing geometry and radiative transfer effects that must be modeled; and we find a 3-sigma upper limit of 8.5 R to the total LBH vehicle glow emission.

Budzien, S. A.↗
NASA NTRS1997

Does the Ultraviolet Imager on Polar Detect Cometesimals?

The Earth's dayglow images obtained by the Ultraviolet Imager (UVI) on Polar should show darkened pixels if cometesimals bombard Earth. This darkening occurs because the UV emissions are absorbed by water between the altitude where the dayglow emissions are produced and the Polar spacecraft. We have asked: (1) Does the UVI detect darkened pixels? (2) If so, what are their characteristics? (3) What can the UVI say about the presence/absence of cometesimals? The UVI does see dark pixels, which tend to be clustered. But the calibration data obtained from the same instrument just before the instrument was launched show similarly darkened pixel clusters. After a though statistical analysis of these images, we conclude that the darkened pixels are instrumental artifacts. Therefore, the UVI does not provide evidence for the existence of the cometesimals.

Parks, G. K.↗
NASA NTRS2001

Quantification of Changes in Thermospheric O/N2 from Observations of UV Airglow and Aurora

The primary goal of the proposed research was to use images from the Ultraviolet Imager (UVI) as remote monitors of changes in the ratio of thermospheric O to N2 at high latitudes in response to geomagnetic disturbances. The principal project tasks were to select UVI image data, develop and extend modeling/analysis tools, and, finally, correlate observed changes with geomagnetic activity. In particular, it was necessary to model the average expected dayglow surface to isolate changes from storms. Note that this research differs significantly from previous efforts in that the 'quiet-time' dayglow surface is modeled from first principles rather than being developed empirically from observations. This technique should thus be more generally applicable to observations from other missions.

Germany, G. A.↗
NASA NTRS2014

Global Investigation of the Mg Atom and ion Layers using SCIAMACHY/Envisat Observations between 70 km and 150 km Altitude and WACCM-MG Model Results

Mg and Mg+ concentration fields in the upper mesosphere/lower thermosphere (UMLT) region are retrieved from SCIAMACHY/Envisat limb measurements of Mg and Mg+ dayglow emissions using a 2-D tomographic retrieval approach. The time series of monthly means of Mg and Mg+ for number density as well as vertical column density in different latitudinal regions are shown. Data from the limb mesosphere-thermosphere mode of SCIAMACHY/Envisat are used, which covers the 50 km to 150 km altitude region with a vertical sampling of 3.3 km and a highest latitude of 82 deg. The high latitudes are not covered in the winter months, because there is no dayglow emission during polar night. The measurements were performed every 14 days from mid-2008 until April 2012. Mg profiles show a peak at around 90 km altitude with a density between 750 cm(exp−3) and 2000 cm(exp−3). Mg does not show strong seasonal variation at mid-latitudes. The Mg+ peak occurs 5-15 km above the neutral Mg peak at 95-105 km. Furthermore, the ions show a significant seasonal cycle with a summer maximum in both hemispheres at mid- and high-latitudes. The strongest seasonal variations of the ions are observed at mid-latitudes between 20-40 deg and densities at the peak altitude range from 500 cm(exp−3) to 6000 cm(exp−3). The peak altitude of the ions shows a latitudinal dependence with a maximum at mid-latitudes that is up to 10 km higher than the peak altitude at the equator. The SCIAMACHY measurements are compared to other measurements and WACCM model results. In contrast to the SCIAMACHY results, the WACCM results show a strong seasonal variability for Mg with a winter maximum, which is not observable by SCIAMACHY, and globally higher peak densities. Although the peak densities do not agree the vertical column densities agree, since SCIAMACHY results show a wider vertical profile. The agreement of SCIAMACHY and WACCM results is much better for Mg+, showing the same seasonality and similar peak densities. However, there are the following minor differences: there is no latitudinal dependence of the peak altitude for WACCM and the density maximum, passing the equatorial region during equinox conditions, is not reduced as for SCIAMACHY.

SCIAMACHYEnvisat↗