Annals of the New York Academy of SciencesVolume 688, Issue 1 p. 801-803 Preliminary Results of the Medium Scale Anisotropy Measurement1 J. Puchalla, J. Puchalla Massachusetts Institute of Technology, Room 20B–145, Cambridge, MA 02139Search for more papers by this authorE. Cheng, E. Cheng NASA/Goddard Space Flight Center, Code 685.0, Greenbelt, MD 20771Search for more papers by this authorD. Cottingham, D. Cottingham Universities Space Research Association, NASA/GSFC Code 685.3, Greenbelt, MD 20771Search for more papers by this authorD. Fixsen, D. Fixsen Applied Research Corporation, NASA/GSFC Code 685.3, Greenbelt, MD 20771Search for more papers by this authorE.P. Gentieu, E.P. Gentieu NASA/Goddard Space Flight Center, Code 685.0, Greenbelt, MD 20771Search for more papers by this authorC. Inman, C. Inman Massachusetts Institute of Technology, Room 20B–145, Cambridge, MA 02139Search for more papers by this authorM. Kowitt, M. Kowitt NASA/Goddard Space Flight Center, Code 685.0, Greenbelt, MD 20771Search for more papers by this authorS. Meyer, S. Meyer Massachusetts Institute of Technology, Room 20B–145, Cambridge, MA 02139Search for more papers by this authorL. Page, L. Page Princeton University Physics Dept., Princeton, NJ 08544Search for more papers by this authorR. Silverberg, R. Silverberg NASA/Goddard Space Flight Center, Code 685.0, Greenbelt, MD 20771Search for more papers by this author J. Puchalla, J. Puchalla Massachusetts Institute of Technology, Room 20B–145, Cambridge, MA 02139Search for more papers by this authorE. Cheng, E. Cheng NASA/Goddard Space Flight Center, Code 685.0, Greenbelt, MD 20771Search for more papers by this authorD. Cottingham, D. Cottingham Universities Space Research Association, NASA/GSFC Code 685.3, Greenbelt, MD 20771Search for more papers by this authorD. Fixsen, D. Fixsen Applied Research Corporation, NASA/GSFC Code 685.3, Greenbelt, MD 20771Search for more papers by this authorE.P. Gentieu, E.P. Gentieu NASA/Goddard Space Flight Center, Code 685.0, Greenbelt, MD 20771Search for more papers by this authorC. Inman, C. Inman Massachusetts Institute of Technology, Room 20B–145, Cambridge, MA 02139Search for more papers by this authorM. Kowitt, M. Kowitt NASA/Goddard Space Flight Center, Code 685.0, Greenbelt, MD 20771Search for more papers by this authorS. Meyer, S. Meyer Massachusetts Institute of Technology, Room 20B–145, Cambridge, MA 02139Search for more papers by this authorL. Page, L. Page Princeton University Physics Dept., Princeton, NJ 08544Search for more papers by this authorR. Silverberg, R. Silverberg NASA/Goddard Space Flight Center, Code 685.0, Greenbelt, MD 20771Search for more papers by this author First published: June 1993 https://doi.org/10.1111/j.1749-6632.1993.tb43975.x 1 The National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC) supports this research through grants NAGW 1841, NGT 50908, NGT 50720 and the Sigma Xi Society through grant 9203. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume688, Issue1Texas/Pascos '92: Relativistic Astrophysics and Particle CosmologyJune 1993Pages 801-803 RelatedInformation

Altitude profiles of the O + 834‐Å emission, obtained from rocket observations at moderate and high solar conditions, are compared with model calculations. The model showed that when viewing the atmosphere horizontally at altitudes below the F 2 layer, the 834‐Å intensity was virtually independent of the O + density. The 834‐Å intensity was found to be highly sensitive to the N 2 absorption cross section. Comparisons with model calculations suggest that absorption by N 2 is a factor of 10 lower than the currently accepted values. Agreement between calculated and observed intensities was obtained by adjusting the N 2 cross sections to 1×10 −19 , 4×10 −19 , and 1.2×10 −18 cm² at the O + triplet wavelengths of 832.75, 833.33, and 834.46 Å, respectively. This adjustment was required in order to simulate the overlap between rotational absorption lines of N 2 and the O + emission lines.

Rocket-borne spectrometers have observed the high-latitude dayside aurora above Cape Parry, N.W.T. Ultraviolet spectra of optical emissions produced by ambient precipitating particles have been obtained in the wavelength region between 530 and 1500 Å, over a range of spectrometer line-of-sight orientations, from 100 km to the rocket apogee of 452 km. The spectrum below 1500 Å is dominated by transitions from neutral and singly ionized atomic oxygen. NI, NII, and molecular nitrogen emissions, which are prominent in day airglow and nighttime auroral spectra measured by the same instrumentation, are very weak, indicating energy from the dayside auroral particles is transferred to the atmosphere above most of the N2. Relative line strengths of OI and OII transitions in the high-latitude dayside aurora differ in comparison with either airglow or nighttime auroral observations. The differences arise from differing excitation mechanisms and radiative-transfer characteristics and indicate the far-UV region of the spectrum can serve as a useful probe for remotely sensing various auroral phenomena. Weak emission near 1170 Å is identified as the OI 3s′3D–2p42D intercombination transition at 1172 Å. Observed OI 1172 Å intensities are consistent with the branching-ratio measurements of Morrison

Observations of emissions extending from the extreme ultraviolet to the near-infrared region of the spectrum were obtained from a rocket payload flown from Cape Parry, N.W.T., Canada, during the CENTAUR campaign December 7, 1981. The flight, NASA 29.017CE (Terrier-Malemute), was launched near local magnetic noon during an electron-precipitation event in the dayside cleft region. Emission rates versus altitude and zenith angle were obtained for the principal atomic-oxygen emission features OI (989 Å), OI (1304 Å), OI (1356 Å), OI (6300 Å), OI (7774 Å), and OI (8446 Å), as well as HI (1216 Å) and OII (834 Å). Some data were also obtained for the [Formula: see text] (first negative) bands. The results suggest an emission layer peaked in the vicinity of 250 to 300 km. Temporal and spatial fluctuations were most pronounced at apogee and on the downleg portion of the flight. Emissions strongly affected by multiple scattering fluctuated less than optically thin emissions.In this paper, estimates of the input energy flux and characteristic energy are made based on the intensity of the OI (6300 Å) and OI (1356 Å) emissions and the altitude of the emission layer. A value of 0.3 to 0.4 erg/cm2∙s for the energy flux and a characteristic energy of approximately 200 eV are consistent with the observations (1 erg = 0.1 μJ).

The earth's far ultraviolet dayglow (1080–1515 Å) was observed at ∼3.5 Å resolution during a period of high solar activity near solar maximum on June 27, 1980. The observations were made at local noon by rocket‐borne spectrometers viewing toward the earth's northern limb at 90° zenith angle (ZA) at altitudes between 100 and 245 km, and at 98° ZA between 245 and 260 km. The solar zenith angle was 8.9°. These spectra are compared with earlier lower‐resolution dayglow data obtained during a period of lower solar activity and with auroral spectra. The brightness ratio of O I λ1356 to the N2 Lyman‐Birge‐Hopfield (LBH) system, an indicator of the O to N2 density ratio, is lower than that previously measured at mid‐latitudes and closer to the value found in aurorae. In the LBH system a depletion of the bands originating on the υ′ = 3 vibrational level of the excited state is found. Some weak N2 Birge‐Hopfield bands and N I lines only marginally detected previously in the dayglow are confirmed.

Rocket observations of the far ultraviolet dayglow spectrum near solar cycle maximum are analyzed using laboratory cross sections, atmospheric composition models, and photoelectron production models. Photoelectron-excited emissions of N2 and O are used to derive a self-consistent description of the atmosphere at solar maximum. Spectral synthesis of the N2 Lyman-Birge-Hopfield bands shows a departure of a 1Pi(q) state vibrational populations from the direct excitation theory. Observations of the N2 second positive (0, 0) 3371-A band and O I 1356-A emission indicate an exospheric temperature of 1600 K, 200 K higher than predicted by empirical models. The empirical models are also found to overestimate the O and O2 densities required to fit the data by a factor of 2 and 1.4, respectively. These results are compared to the results of an analysis of similar observations made in 1978 near solar minimum.

Daytime airglow spectra between 530 and 930 Å were obtained at ∼4 Å resolution from a rocket launch at White Sands, New Mexico, June 27, 1980. Portions of the spectrum were observed in second order at ∼2Å resolution. The higher resolution of the present data confirms our previous identification of O II transitions and resolves the identification of O II emission at 537–539 Å as due to both a doublet and a quartet component. For the case of viewing at 90° to the zenith between 196 and 242 km ∼1/3 of the 537‐539 Å emission originates from the O II 2 s 2 p 4 ² P state. We infer a 538/581 Å branching ratio of ∼ 3 in agreement with laboratory and calculated values of 1.6 to 3.3. Other O II branching ratios are in agreement with laboratory data. A somewhat low value for the 718/796 ratio in the flight data is interpreted as due to blended N 2 emission at 796 Å. The observed emission rate from the 2 s 2 p 4 ² P state is more adequately modeled using partial photoionization cross sections calculated using the dipole velocity rather than the dipole length approximation. This fact must be considered when computing the 834 Å emission rate from direct photoionization. N II is seen to be a very minor source of emission below 916 Å in the dayglow. The identification of O II 581 Å emission confirms a prediction made in 1977 by Delaboudinière. The O II emission at 581 Å complicates interpretation of low resolution spectral observations near 584 Å in the airglow and also for the case of comets and planets where O atoms and O bearing molecules are present.

5-8 erg cm-2s -1 energy content and 1.75- to 2.5-keV characteristic energy. The N2 Lyman-Birge- Hopfield spectral synthesis shows that the vibrational populations for the observed emissions are in agreement with laboratory electron impact spectra and the Franck-Condon factors to v" = 0. This precludes any cascade process to the aIIg state, which significantly changes the relative populations. Altitude profiles of the various bands can be reprodouced by theory. Dissociation of N2 can account for N I lines at 1134, 1200,' and 1493 , and NII 1085 A. Contrary to previous observations of auroras and the dayglow, there is no evidence of multiple scattering of 1200-A radiation by atomic nitrogen in the present observations. The atomic oxygen density required to explain the O I 1356, 1304, and 989- emissions is 4 x 101øcm -3 at 120 km, a factor of 3.5 lower than the Jacchia (1971) model. lin, 1978). The radiative transport analysis of the EUV molecular band systems is rather involved, in that a model must be developed that takes account of multiple scattering in the presence of predissociation and branching to intermediate electronic levels. While some of the emission cross sections for electron impact excitation and some branching ratios have recently been measured (Zipf and Gorman, 1980), many are not yet known. The development of such a model based on the known molecular constants has just begun, but is not yet completed. Therefore we shall limit the task of the present paper to the analysis of FUV emissions of N2 and atomic oxygen. Far ultraviolet observations of the aurora and airglow provide quantitative diagnostics of atmospheric abundances, energy deposition and excitation processes because many atmospheric species have resonance transitions in this spec- tral regime. The accompanying paper (Feldman and Gen- tieu, this issue) discusses such an observation, namely the spectroscopy of an active auroral arc above Fort Churchill on March 29, 1978. In the present paper we attempt to quantify the measurements with a self-consistent approach used earlier by us in the analysis of the FUV dayglow (Meier

High‐resolution (∼1 Å) dayglow observations of the O I(1304 Å) and O I(989 Å) multiplets were made from an Astrobee‐F rocket payload (25.046 CE) launched from White Sands, New Mexico at local noon on June 27, 1980 to an apogee of 260 km. Three components of the O I(1304 Å) multiplet were measured at zenith angles of approximately 50° and 140° at 1.1 Å resolution. Over the entire altitude range of observation, i.e., 100–260 km, the three components were found to be equal to within ±15%. The absolute intensity profile of the total O I(1304 Å) multiplet was approximately 30% greater than that obtained on an earlier rocket flight (25.029 GA) launched January 9, 1978 from White Sands, when the solar activity and the elevation angle of the sun were both lower. The shape of the O I(989 Å) multiplet distribution observed on the flight at 1.3‐Å resolution was indistinguishable from an optically thin source with the energy levels of the excited state populated according to their statistical weights in spite of the large optical depths of the O I(989 Å) multiplet at rocket altitudes. Experiments with a laboratory UV source also showed the insensitivity of the multiplet distribution to the optical depth of the source. These results are entirely consistent with a recently developed PFR radiative transport code (Meier, this issue) in the absence of selective absorption by rotational lines of N2.

Ultraviolet spectra between 530 and 1520 Å of an active auroral arc were obtained at 6.5‐Å instrumental resolution. Several new emission features are identified, including several bands of the N2 Birge‐Hopfield (1,υ″) progression and numerous N I multiplets, the latter being preponderant at low altitudes. The improved instrumental resolution over previous experiments in the wavelength region below 1200 Å allows for a partial resolution of the complex structure between 900 and 1100 Å reported in earlier work. The ratio of O I λ1356 to N2 Lyman‐Birge‐Hopfield is smaller than in the dayglow at a similar altitude, and this is interpreted as evidence for a depletion of atomic oxygen in the auroral ionosphere relative to mid‐latitude composition.

The emission line spectrum of singly ionized atomic oxygen (O II) dominates the day airglow spectrum in the extreme ultraviolet below 834 Å. The strongest resonance line, at 834 Å, is optically thick and an analysis of height profiles obtained from rocket observations between 140 and 265 km in specific viewing directions indicates that the principal excitation source is direct photoionization of neutral atomic oxygen. Strong emission at 538–539 Å is most likely due to the quartet rather than the doublet transitions, which both occur at these wavelengths and which are not spectrally resolved in the data. The intensities of the weaker lines are consistent with recent laboratory measurements of transition branching ratios. Several strong O II lines near He I 584 produce severe contamination of low‐altitude (<400 km) measurements of geocoronal helium emission made with thin‐film broadband photometers.

The spectral characteristics of the mid-latitude daytime airglow observed between 530 and 1500 A under conditions of high solar activity are compared with those obtained at the same location during markedly lower solar activity. The spectral observations were made by two scanning spectrometers and an N2 3371 A photometer carried aboard Astrobee-F rockets launched from White Sands Missile Range, NM, on January 9, 1978 and June 27, 1980. The more recent data allow the partial resolution of the emission spectrum between 800 and 1200 A into a large number of weak N I, O I and N2 transitions. Data taken at 220 km altitude suggest an increase in atomic nitrogen density of more than a factor of 3 between the two observations, along with a doubling of the solar EUV flux at wavelengths less than 688 A. No evidence of a corresponding increase in the 10 to 50 eV photoelectron flux is found, however, an ionospheric sounding data indicate the peak electron density to have decreased during this period. The mechanism for this electron flux decrease in the face of increased EUV flux and only a three-fold increase in N concentration remains unknown.

Rocket observations of the Lyman α and Lyman β day airglow are analyzed using a nonisothermal spherical model of the radiation field. This new model provides, for the first time, a method of determining atomic hydrogen densities in the mesosphere and thermosphere. Interpretation of Lyman α data taken between 80 and 260 km is consistent with current mesospheric and thermospheric models, with H density equal to 1.9 × 107 cm−3 at 100 km. Analysis of 1025A data suggests that the emission is dominated by Lyman β with perhaps as much as a 30% contribution from OI 1027.

Rocket observations of the dayglow spectrum between 530 and 1500A were obtained on 9 January 1978 at a solar zenith angle of 56°. Data were obtained from 80 to 260km with viewing angles of 40°, 90°, and 180° to the local zenith. OI emissions were observed at 989, 1027, 1152, 1304, and 1356A. Analysis of these data with a radiative transfer model using the energy dependences of currently accepted excitation cross sections, branching ratios, and photoelectron fluxes shows that electron impact excitation is the primary source of these emissions. The infrared emission rates at 7990 and 11287A are also calculated in this analysis for comparison with previous observations and estimates.

Far ultraviolet rocket spectra of N I and N2 dayglow emissions have been analyzed by using AE‐E photoelectron spectra, laboratory‐measured excitation cross sections, and photochemical models of atomic nitrogen. A self‐consistent picture of both optically thick and thin emission features is found by using a model in which the principal production mechanism for N I 1200‐Å and 1493‐Å photons is photodissociative excitation of N2. The aeronomic data require that ∼50–70% of the excited 4P atoms produced dissociatively have velocities within the Doppler core of the ambient nitrogen atoms, contrary to the expectation that those atoms are produced with large excess kinetic energy. The derived atomic nitrogen density has a maximum density of 2.7 × 107 cm−3 at 170 km, a value that is within 40% of that from recent models of odd nitrogen photochemistry.

EUV spectra (530‐1500Å) of the day airglow in up, down and horizontal aspect orientations have been obtained with 6.5Å resolution and a limiting sensitivity of 5R from a rocket experiment. Below 834Å the spectrum is rich in previously unobserved OII transitions connecting with 4So, ²Do, and ²Po states. Recent broad‐band photometric observations of geocoronal HeI 584Å emission can be understood in terms of the newly observed OII emissions. The OI 989Å and OI 1304Å emissions exhibit similar dependence on altitude and viewing geometry with the OI 989Å brightness 1/15 that of OI 1304. Emission at 1026Å is identified as geocoronal HI Lyman‐β rather than OI multiplet emission and observed intensities agree well with model estimates. An unexpectedly high NI 1200/NI 1134Å brightness ratio is evidence of a significant contribution from photodissociative excitation of N2 to the NI 1200Å source function.

Cross sections have been measured with 0.5 Å resolution between 584 Å and respective thresholds for CO+2 A and B excited states as they fluoresce to the CO+2 ground state. Beutler–Fano resonance profiles are observed in both cross sections converging to the CO+2 C 2Σ ion limit at 640 Å. Characteristics of the initial and final states involved in the ionization process are discussed in detail. The ratio of the absolute magnitudes of the A:B fluorescence cross sections reported in this work is in excellent agreement with results of previous workers near 584 Å, pointing up a fundamental discrepancy between initial and final state measurements of CO+2 A and B excited state populations.