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Torr, D. G.

Publications and source records attributed to Torr, D. G..

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Associative ionization of N/2D/ and O

Recent laboratory measurements have shown that N(2P) atoms, and thus probably hot N(2D) atoms, will recombine with atomic oxygen via an associative ionization process at the gas kinetic rate. In the present paper the likelihood of the associative ionization of N(2D) and O playing a significant role in the normal ionosphere is investigated in the light of several recent studies. It is concluded that the associative ionization process is not an important factor and that a more probable cause for disagreements in the various determinations of the recombination coefficient, is the difference in excited states of the ions in the various experiments.

Torr, M. R.↗
NASA NTRS1979

Zodiacal light surface brightness measurements by Atmosphere Explorer-C

The visible airglow photometer on the Atmosphere Explorer-C satellite has been used to map the zodiacal light surface brightness at the wavelengths monitored by the instrument: 3371, 4278, 5200, 5577, 6300, and 7319 A. The study constitutes a survey over this wavelength range, covering most of the celestial sphere from altitudes above the atmospheric emissions and free from atmospheric scattering and attenuation. The intensity variations reveal enhancements near elongations of 130 deg and possibly near 60 deg at all wavelengths. The intensity of the zodiacal light near the ecliptic pole is found to be about 30 S10 units. The color ratio with respect to the sun is found to be redder than the sun (0.7) at all elongations.

Torr, M. R.↗
NASA NTRS1979

Ionization frequencies for major thermospheric constituents as a function of solar cycle 21

Increases in the solar ultraviolet flux (wavelengths shorter than 1250A) over the past five years of rising solar activity have been larger than anticipated. This increase in UV flux dramatically affects the production of ionization of the various constituents in the thermosphere. Measurements of the solar UV flux by the Atmosphere Explorer satellites are used to determine ionization frequencies for the major thermospheric species for various dates exhibiting notably different levels of solar activity. For the convenience of users of such data, a reduced set of cross-section and flux data is presented for the wavelength range below 1027A, consisting of 37 wavelength intervals

Torr, M. R.↗
NASA NTRS1979

Dissociative recombination of N2/+/ in the ionosphere

N2(+) ion measurements are examined which were made with the Atmospheric Explorer-C satellite during a phase of solar activity in 1978 that was significantly higher than near the earlier minimum. It is found that the major source of N2(+) is photoionization, rather than charge exchange with O(+) (2D), and that the major loss process above 300 km is dissociative recombination with electrons. A data sample for which the electron temperature (T sub e) covered the range from 1000 to 3400 K is used to evaluate the rate constant, alpha, for the dissociative-recombination process. The results show good agreement with laboratory measurements given by the expression: alpha = 1.8 x 10 to the -7th (T sub e/300) to the -0.39th cu cm/sec.

Torr, M. R.↗
NASA NTRS1979

Energetic oxygen - A direct coupling mechanism between the magnetosphere and thermosphere

The study investigates the effects of the precipitation of energetic O(+) ions (0.7 - 12 keV) into the atmosphere during magnetic storms. The energetic O(+) ion flux produces a splash of lower energy neutral oxygen atoms at the top of the atmosphere. As a result of the photo-ionization and charge exchange with H(+) ions in the plasmasphere, these backscattered atoms produce a low energy O(+) flux that is more than 10 times larger in magnitude than the original energetic O(+) flux. The energetic O(+) events thus provide a potential source mechanism for the lower energy (no greater than about 30 eV) O(+) ions observed in the plasmasphere. It is also suggested that the energetic ion events may be self-sustaining in that some of the ionized 'splash' particles (no greater than about 10%) are subsequently accelerated by an as yet unidentified mechanism to the higher observed energies. It is found that 96% of the incoming energy is transferred to the neutral atmosphere in the form of heating. Measured fluxes indicate heating rates as high as about 0.4 erg/sq cm/sec/ster.

Torr, M. R.↗
NASA NTRS1979

Determination of the auroral O/1S/ production sources from coordinated rocket and satellite measurements

This paper examines the auroral excitation mechanisms using data collected in a satellite/rocket/aurora coordination. Past theories considered that variation with altitude of the emission from the O(1S) state is the same as that from the N2(+) first negative band system. Actually, the source function for O(1S) does not covary with N2(+) but has a smaller scale height. The covariation is due to quenching of the source function by O(3P). The steadiness of the aurora in a flight of the Michigan Airglow Payload allows the profile to be differentiated for direct comparison with theory. It is concluded that when most of the relevant variables for production of the O(1S) state are simultaneously measured in aurora, the major source functions are dissociative recombination of O2(+) above 210 km to apogee at 250 km, and below 180 km the energy transfer from N2(A3sigma) in the oxygen atom quenching reaction.

Sharp, W. E.↗
NASA NTRS1979

Recombination of NO/+/ in the mid-latitude trough and the polar ionization hole

The dissociative recombination of NO(+) with electrons is further examined using a sample of Atmosphere Explorer data from the midlatitude ionization trough. The electron temperature for this data sample covered a range of 2500 K, thus allowing an accurate determination of the temperature dependence of the rate coefficient. The results confirm earlier determinations which were made from a large data base, and the rate coefficient alpha is found to be inversely proportional to the electron temperature. The possibility of a neglected process in the NO(+) chemistry is investigated which, if it were included, might result in a smaller temperature dependence of alpha. Such a source would require a direct dependence on electron temperature. A possible candidate is associative recombination of energetic N(D-2) with O. The results confirm recent measurements which find that this process cannot be significant. The NO(+) chemistry is a very sensitive indicator of chemical equilibrium conditions. By using measurements of the relevant parameters made in the polar ionization hole it is found that horizontal drifts do not appear to be significant in this region.

Torr, M. R.↗
NASA NTRS1979

Chemistry of the thermosphere and ionosphere

In the present paper, some of the most important features of the Atmosphere Explorer program, involving studies of the chemistry of the ionosphere and thermosphere, are reviewed. Solar flux and cross sections are tabulated, along with the revised reference spectrum F47113 as compared with the preliminary R74113. The principal results examined include some unexpected variations in the EUV flux and in the response of the thermosphere, revealed by extreme ultraviolet spectrophotometers; discrepancies between the measured and calculated electron flux; recent developments in the detection of nocturnal mid- and low-latitude sources of ionization; and the application of AE satellite data to the study of ionospheric and thermospheric processes, rate coefficients, and atomic and molecular processes.

Torr, D. G.↗
NASA NTRS1979

Determination of the sources and sinks of N/+/ ions in the thermosphere

Measurements of atmospheric parameters made by the Atmosphere Explorer-C satellite used to identify mechanisms for the production and loss of N(+) ions in the ionosphere are presented. Photo-dissociative ionization of N2 is the main source below 250 km. Above 250 km the reaction O(+)(4S) + N(2D) yields N(+)(3P) + O(3P) is dominant, and a possible minor source of N(+) is the reaction O(+)(2P) + N2 yields N(+) + NO. Photoionization of N(4S) and dissociative charge exchange of He(+) with N2 constitute detectable sources above 350 km. Charge exchange of N(+) with O is a significant sink above 300 km, and the rate coefficients for these reactions are derived.

Torr, D. G.↗
NASA NTRS1979

An experimental and theoretical study of the mean diurnal variation of O/+/, NO/+/, O2/+/, and N2/+/ ions in the mid-latitude F1 layer of the ionosphere

A theoretical model of the diurnal variations in the compositions of the ions O(+), NO(+), O2(+) and N2(+) in the midlatitude F1 layer is presented and compared with measurements made by AE-C. The theoretical model includes the rate coefficients and branching ratios for the dissociative recombination of NO(+), O2(+) and N2(+) with electrons and the ion-atom interchanges of O(+) with N2 and N2(+) with O. Input parameters to the model comprise measurements of ion and electron temperatures, neutral atmosphere composition, the solar EUV flux and the photoelectron spectrum. In general, model calculations are found to agree with satellite measurements, confirming the major ion sources and sinks of the photochemical model, which has an accuracy of + or - 60%.

Torr, D. G.↗
NASA NTRS1979

N2 vibrational distribution in aurorae

The N2 vibrational distribution is calculated for a specific IBC Class II aurora using as input data obtained from coordinated rocket and satellite observations and currently accepted excitation and quenching rates. The results of the calculations indicate no significant vibrational enhancements for this specific aurora nor for 'upper limit' estimates for more intense aurorae. It is concluded that if significantly larger concentrations of vibrationally excited N2 molecules exist in the aurora, as recent rocket EUV measurements suggest, current concepts of the sources and sinks of N2 vibrational excitation will require significant revision.

Waite, J. H.↗
NASA NTRS1979

Ionospheric chemistry

This report deals primarily with progress in the chemistry of minor neutrals and ionized constituents of the thermosphere. Significant progress was made over the last few years in quantitative studies of many chemical processes. This success was primarily due to the advent of multiparameter multisatellite programs which permitted accurate simultaneous measurements to be made of many important parameters. In many cases studies of chemical reactions were made with laboratory-like precision. Rate coefficients have been derived as functions of temperature for a number of important reactions. New information has been acquired on nearly every major process which occurs in the thermosphere, including the recombination rates of all major molecular ions, charge transfer reactions, ion atom interchange reactions, and reactions of neutral and ionized metastable atoms and molecules.

Torr, D. G.↗
NASA NTRS1979

Refinement of the aeronomically determined rate coefficient for the reaction of N2/+/ with O

An earlier aeronomic determination of the rate coefficient for the reaction N2(+) + O yields NO(+) + N using Atmosphere Explorer data indicated a small increase in the rate coefficient with ion temperature, contrary to laboratory observations. This was incorrectly attributed to neglect of an increase in the N2(+) recombination rate with vibrational excitation. Recent aeronomical results have shown that the rate coefficient for charge exchange of O(+)(2D) with N2 is about an order of magnitude smaller at thermal temperatures than at energies greater than 0.5 eV (i.e., energies at which laboratory measurements have been made). It is shown that the use of the smaller charge exchange rate coefficient coupled with recent results on N2 quenching of O(+)(2D) yields a temperature dependence in excellent agreement with the laboratory results for the rate coefficient.

Torr, D. G.↗
NASA NTRS1979

Charge exchange of metastable 2D oxygen ions with molecular oxygen - A new source of thermospheric O2/+/ ions

Reactions involving metastable ions are difficult to study in the laboratory. Much new information on these reactions has been derived from satellite measurements of aeronomic parameters. In this paper, Atmosphere Explorer D data are used to study charge exchange of metastable O(+)(2D) ions with O2. Using direct measurements of the O2 at 200 km to compute O2 densities at 300 km and supporting ionic concentrations and temperature observations, we find the rate coefficient for this reaction to be 1 + or - 0.6 times 10 to the minus 9th cu cm/sec. The process constitutes a significant source of O2(+) ions in the F2 layer at times when the N2 and O2 densities are enhanced. This finding leads to the conclusion that charge exchange with O2 must be a major sink for O(+)(2D) and an important source of O2(+) ions in the E region, because of the increase in the O2 concentration/N2 concentration ratio with decreasing altitude. The results imply that 80% of all O(+) ions formed in the E region are converted to O2(+) and that only about 20% of the metastable O(+) ions are converted into N2(+) through charge exchange with N2.

Torr, D. G.↗
NASA NTRS1978

Zodiacal light dynamics experiment: A wideband imaging Fabry-Perot interferometer

The Solar Probe will provide an ideal platform from which to study dynamics of dust particles near the sun by measuring the detailed character of the Fraunhofer structure of the zodiacal light. The suggested instrument is a wideband imaging Fabry-Perot interferometer with state of the art technology in both the optics and the detector. The instrument would function as a high-resolution imaging device providing wavelength resolution of 0.03 A over about a 20 A range. The wideband imaging capability would provide sky maps of the zodiacal light on a despun spacecraft without mechanical scanning. The Solar Probe mission would allow the velocity distribution of the dust to be mapped along most of the trajectory of the spacecraft.

Torr, D. G.↗
NASA NTRS1978

The effect of N2/+/ recombination on the aeronomic determination of the charge exchange rate coefficient of O/+//2D/ with N2

The Atmosphere Explorer (AE) data are reexamined in the light of new laboratory measurements of the N2(+) recombination rate coefficient alpha. The new measurements support earlier measurements which yielded values of alpha significantly lower than the AE values. It is found that the values for alpha determined from the satellite data can be reconciled with the laboratory measurements, if the charge exchange rate coefficient for O(+)(2D) with N2 is less than one-quarter of that derived in the laboratory by Rutherford and Vroom (1971).

Torr, D. G.↗
NASA NTRS1978

Review of rate coefficients of ionic reactions determined from measurements made by the atmosphere explorer satellites

The large data base of aeronomic parameters measured by the Atmosphere Explorer C, D, and E satellites since December 1973 has been used to determine a number of reaction rate coefficients highly relevant to our understanding of thermospheric chemistry. In this paper the results are reviewed for ionic rate coefficients for recombination of NO(+), O2(+), for reactions of O(+) + N2, N2(+) + O, and O(++) + O, and for various reactions involving O(+)(2D) and O(+)(2P) ions with O and N2.

Torr, D. G.↗