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Roble, R. G.

Publications and source records attributed to Roble, R. G..

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Solar-terrestrial coupling through atmospheric electricity

There are a number of measurements of electrical variations that suggest a solar-terrestrial influence on the global atmospheric electrical circuit. The measurements show variations associated with solar flares, solar magnetic sector boundary crossings, geomagnetic activity, aurorae, differences between ground current and potential gradients at high and low latitudes, and solar cycle variations. The evidence for each variation is examined. Both the experimental evidence and the calculations made with a global model of atmospheric electricity indicate that there is solar-terrestrial coupling through atmospheric electricity which operates by altering the global electric current and field distribution. A global redistribution of currents and fields can be caused by large-scale changes in electrical conductivity, by alteration of the columnar resistance between thunderstorm cloud tops and the ionosphere, or by both. If the columnar resistance is altered above thunderstorms, more current will flow in the global circuit, changing the ionospheric potential and basic circuit variables such as current density and electric fields. The observed variations of currents and fields during solar-induced disturbances are generally less than 50% of mean values near the earth's surface.

Roble, R. G.↗
NASA NTRS1978

Effect of anomalous transport coefficients on the thermal structure of the storm time auroral ionosphere

By analyzing an observed storm time auroral electron temperature profile it is shown that anomalous transport effects strongly influence the thermal structure of the disturbed auroral ionosphere. Such anomalous transport effects are a consequence of plasma turbulence, the existence of which has been established by a large number of observations in the auroral ionosphere. The electron and composite ion energy equations are solved with anomalous electron thermal conductivity and parallel electrical resistivity coefficients. The solutions are parameterized with respect to a phenomenological altitude-dependent anomaly coefficient A and are compared with an observed storm time electron temperature profile above Chatanika. The calculated temperature profile for the classical case (A = 1) disagrees considerably with the measured profile over most of the altitude range up to 450 km. It is shown that an anomaly coefficient with a sharp peak of the order of 10,000 centered around the F2 peak is consistent with observations.

Fontheim, E. G.↗
NASA NTRS1978

The O I /6300 A/ airglow

The production and destruction of O(D-1) atoms in the thermosphere are studied on the basis of observations conducted by the Atmosphere Explorer-C spacecraft. In particular, measurements of the O I transition at 6300 A provide a means of calculating the strength of the O2(+) dissociative recombination source of O(D-1), which amounts to 1.33. A value of 3 times 10 to the minus 11th power cu cm/sec is established for the quenching rate of O(D-1) by molecular nitrogen, while the photodissociation rate for O2 is set at three millionths per sec. These determinations are in agreement with the conventional theory of the day 6300-A airglow.

Hays, P. B.↗
NASA NTRS1978

The calculated and observed ionospheric properties during Atmospheric Explorer-C satellite crossings over Millstone Hill

Results are presented for calculated and observed incoherent scatter radar data on ionospheric and atmospheric properties during the crossings of the Atmospheric Explorer-C satellite over the Millstone Hill, Massachusetts incoherent scatter radar station. The incoherent scatter radar measured electron density vertical profiles and electron and ion temperatures. These values yielded the exospheric temperature and the vertical distribution of neutral gas temperature. The satellite measured electron and ion temperatures and densities, neutral gas composition, and photoelectron spectra. Measurements were also made of solar UV and EUV fluxes, the vertical profile of the NO number density, and the vertical profile of the 6300 A airglow-volume emission rate. The results are compared to those of a time-dependent coupled model of the ionospheric E- and F-regions. Good agreement is found between satellite results, incoherent scatter radar measurements, and model calculations. Along the orbital path satellite measurements show significant latitudinal gradients in the measured properties.

Roble, R. G.↗
NASA NTRS1977

Photoemission in the second positive system of molecular nitrogen in the earth's dayglow

The results are presented of analyses of 3371-A profiles measured by the visible airglow experiment reported by Hayes et al. (1973). The measured emission rate profiles are presented as functions of the O and N2 densities determined simultaneously by means of an open source mass spectrometer. The experimental methods used are discussed along with the obtained results. The experimental data are compared with theoretical predictions. It is found that the 3371-A emission depends greatly on the O/N2 concentration ratio.

Kopp, J. P.↗
NASA NTRS1975

Atmospheric heating by solar EUV radiation

A diurnal model of the mid-latitude ionospheric R region is used to calculate the diurnal variation of the neutral gas heating rates and neutral gas heating efficiency for conditions similar to those over Millstone Hill on March 23-24, 1970. The calculations show that the absorbed solar EUV (wavelength less than or equal to 1025 A) energy is almost equally split between photoelectrons and ion pair production. Photoelectrons heat the ambient electron gas by Coulomb collisions and by the quenching of certain excited ion species, whereas the ion gas is primarily heated by collisions with hot electrons and by chemical reactions. Heating processes above 300 km, between 170 and 300 km, and below 170 km are identified.

Stolarski, R. S.↗
NASA NTRS1973

Study of the technique of stellar occultation

The results are reported of a study of the stellar occultation technique for measuring the composition of the atmosphere. The intensity of starlight was monitored during the occultation using the Wisconsin stellar ultraviolet photometers aboard the Orbiting Astronomical Observatory (OAO-A2). A schematic diagram of an occultation is shown where the change in intensity at a given wavelength is illustrated. The vertical projection of the attenuation region is typically 60 km deep for molecular oxygen and 30 km deep for ozone. Intensity profiles obtained during various occultations were analyzed by first determining the tangential columm density of the absorbing gases, and then Abel inverting the column densities to obtain the number density profile. Errors are associated with each step in the inversion scheme and have been considered as an integral part of this study.

Hays, P. B.↗
NASA NTRS1973

Stellar occultation measurements of molecular oxygen in the lower thermosphere.

Stellar ultraviolet light near 1500 A is attenuated in the earth's upper atmosphere due to strong absorption in the Schumann-Runge continuum of molecular oxygen. The intensity of stars in the Schumann-Runge continuum region has been monitored by the University of Wisconsin stellar photometers aboard the OAO-2 satellite during occultation of the star by the earth's atmosphere. These data have been used to determine the molecular oxygen number density profile at the occultation tangent point. The results of 14 stellar occultations obtained in low and middle latitudes are presented giving the night-time vertical number density profile of molecular oxygen in the 140-200 km region. In general, the measured molecular oxygen number density is about a factor of 2 lower than the number densities predicted by the CIRA 1965 model.

Hays, P. B.↗
NASA NTRS1973

Observation of mesospheric ozone at low latitudes.

Stellar ultraviolet light near 2500 A is attenuated in the earth's upper atmosphere due to strong absorption in the Hartley continuum of ozone. The intensity of stars in the Hartley continuum region has been monitored by the University of Wisconsin stellar photometers aboard the OAO-2 satellite during occultation of the star by the earth's atmosphere. These data have been used to determine the ozone number density profile at the occultation tangent point. The results of approximately 12 stellar occultations, obtained in low latitudes, are presented, giving the nighttime vertical number density profile of ozone in the 60- to 100-km region.

Hays, P. B.↗
NASA NTRS1973

The nighttime distribution of ozone in the low-latitude mesosphere.

Results of OAO-2 satellite ozone measurements are compared with theory and other nighttime ozone measurements. The results of a single occultation scan are also presented, and calculations illustrating the difference in retrieving, from stellar and solar occultation data, the bulge that the nighttime ozone number density profile has at an altitude of about 80 km are discussed.

Roble, R. G.↗
NASA NTRS1972

The stable auroral red arc of October 31 - November 1, 1968 and its interaction with the neutral atmosphere

Satellite observations of electron temperature and the topside electron density structure are used to calculate the red arc according to the thermal conduction model. In this model, energy from the magnetosphere flows in the electron gas along geomagnetic field lines into the ionosphere. This energy heats the ambient F-region electrons sufficiently to excite the oxygen atoms to the O I(1D) level by collisional impact giving rise to the 6300 A emission characteristic of the arc. For the 31 October/1 November 1968 red arc, the calculated emission rate, geographical position, and horizontal extent of the red arc are in agreement with the photometric data obtained by airglow observatories. Almost all of the energy conducted into the red arc is ultimately transferred to the neutral gas through elastic and inelastic collisions. This energy drives a large thermal cell and the circulation extends the influence of the arc thousands of kilometers beyond the region of direct heat input. The calculated neutral gas temperature response to electron heating within the arc is small.

Roble, R. G.↗
NASA NTRS1972

Terrestrial atmospheric composition from stellar occultations

Stellar ultraviolet light transmitted through the upper mesosphere and lower thermosphere of the earth's atmosphere is primarily affected by the photoabsorption processes of ozone and molecular oxygen. The stellar ultraviolet photometers aboard the OAO-2 satellite have measured the intensity changes of several stars during occultation of the star by the earth. The measurements of the relative intensity change in certain atmospheric absorption bands are used to recover the vertical number density profiles of the absorbing species. Using the OAO-2 occultation data, the vertical number density profiles of molecular oxygen in the 100-200 km altitude region and ozone in the 60-100 km altitude region are determined.

Hays, P. B.↗
NASA NTRS1971

Calculated and observed features of stable auroral red arcs during three geomagnetic storms.

Satellite electron temperature and density data are used to calculate the structure of several stable auroral red arcs (SAR arcs) according to the thermal conduction model of the arc. The calculated lambda 6300 emission rates are compared with ground-based photometric observations taken at the same time and in the vicinity of the satellite crossings of the arcs. The SAR arcs analyzed include a range of lambda 6300 intensities, geographical locations, and times during the associated geomagnetic storm. In addition, satellite data were obtained at different altitudes over and within the SAR-arc region. Enhanced electron temperatures within or on the equatorward edge of an electron-density depression are common features of all the SAR arcs examined. There is general agreement between the calculated and observed lambda 6300 emission features for SAR arcs observed during the geomagnetic storm periods of Oct. 29 to Nov. 2, 1968, May 14-15, 1969, and Mar. 8-9, 1970. For these SAR arcs, thermal conduction from the magnetosphere alone is sufficient to excite the lambda 6300 emission to its observed intensity.

Roble, R. G.↗