Green Line Of Atomic Oxygen Research Articles

On how atmospheric temperature affects the intensity of oxygen emissions in the framework of the Barth’s mechanism

The three-body recombination of oxygen atoms O + O + M → O2(el) + M is the dominant process of oxygen excitation in the Earth’s nightglow at altitudes of 85–110 km. The rate coefficient of this reaction, as well as the quantum yields of electronically excited products (O2(el) in the electronic states: 5πg, A3Σu+, A′3Δu, c1Σu+, b1Σg+, a1Δg, X3Σg-) depend on the gas kinetic temperature. In addition to the direct one-stage excitation channel of these levels of the O2 molecule, the Barth’s mechanism considers the two-stage energy transfer channel. In this channel, higher excited levels of the O2 act as precursors for the excitation of the O(1S) atom and the underlying electronic levels of the O2. In this study, we use sensitivity analysis to consider the temperature dependence of the processes of excitation and quenching for each of the excited components. The analytical expressions are obtained for the sensitivity coefficients of the Volume Emission Rates depending on temperature for the green line of atomic oxygen O(1S → 1D), the Herzberg I band O2(A3Σu+→X3Σg-) and O2 Atmospheric band O2(b1Σg+,v'=0→X3Σg-, v''=0). With the help of the sensitivity analysis performed in this work, we (a) confirm that the state O2(5πg), produced by the three-body recombination of atomic oxygen, is a precursor for the formation of O2(b1Σg+), (b) estimate the quantum yield of the O2(b1Σg+) state formed as a result of collisional reaction O2(5πg) with O2, and (c) propose a method for determining a type of precursor for production of O(1S) in the Barth's mechanism.

Variations of the Nightglow 557.7 nm Emission Intensity during Solar Cycle 23

The results of photometric measurements of the intensity of 557.7 nm nightglow emission at a high geographical latitude of 63° N at the Yakutsk meridian (130° E) on days in 1997–2008 with low geomagnetic activity are presented. Statistical analysis shows that the long-term variations in the intensity of the green line of atomic oxygen are consistent with earlier observations at low and midlatitudes. The average intensity of the 557.7 nm emission for February and March had the largest values, ~400 and ~300 rayleighs, respectively, in the years of the maximum of solar cycle 23. This is likely determined by the growth in the concentration of atomic oxygen at the height of the green line emission upon an increase in solar activity according to the MSIS-90 empirical model. It is known that the green-line intensity may significantly vary at nighttime. Analysis of the coefficient of this emission variation shows that there is no close relationship between this parameter and solar activity.

Modeling nightglow in atomic oxygen red and green lines under moderate disturbed geomagnetic conditions at midlatitudes

We present results of a study of mid-latitude auroras. The study is based on optical measurements and theoretical modeling. The modeling shows that precipitation can indirectly generate airglow in red and green lines of atomic oxygen by increasing rates of ion formation and heating of thermal electrons. This causes an increase in the rate of dissociative recombination and thermal-electron-collision excitation of the 1D and 1S levels.

Моделирование ночных свечений красной и зеленой линий атомарного кислорода для умеренно-возмущенных геомагнитных условий на средних широтах

We present results of a study of mid-latitude auroras. The study is based on optical measurements and theoretical modeling. The modeling shows that precipitation can indirectly generate airglow in red and green lines of atomic oxygen by increasing rates of ion formation and heating of thermal electrons. This causes an increase in the rate of dissociative recombination and thermal-electron-collision excitation of the 1D and 1S levels.

The ionospheric source of the red and green lines of atomic oxygen in the Venus nightglow

We have modeled the nightside ionosphere of Venus for 11 solar zenith angles between 90° and 165° with a view toward determining the intensities of the atomic oxygen red, green and 2972Å features in the nightglow. The ionospheric source of these emissions is mainly dissociative recombination of O2+, which may proceed via four channels, which produce two O atoms in various combinations of the ground O(3P) state and the electronically excited O(1D) and O(1S) states. These excited states are the precursors to the nightglow features. We have modeled the O2+(v) vibrational distribution for each of the models, and we have used it to determine branching ratios for the DR channels. We have assumed that the ionosphere is produced by transport of atomic ions from the dayside, and that the ratios of the atomic ions are the same as the model values of the upward ion fluxes on the dayside. For each model, we have normalized the downward atomic ion fluxes to the peak O+ densities that were measured by the Pioneer Venus Orbiter Ion Mass Spectrometer. For the non-sunlit models, the O2+ densities peak in the altitude range 152–159km. We have computed the density profiles of O(1D) and O(1S), and the integrated overhead intensities of the transitions for each of the models. We find that the average intensities, weighted by the area of the solar zenith angle bins, for the red, green and 2972Å emissions are 26R, 4.6R, and 0.46R, respectively. Thus the average high solar activity nightside ionosphere cannot produce green line intensities that are as large as the maximum intensity of about 150R as measured from the ground. Our predicted red line intensities are, however, larger than the upper limits determined by ground based and spacecraft measurements. Possibilities for increasing the green line intensities and decreasing the red line intensities are discussed.

Calculation of the parameters of a spectrophotometric system for measuring airglow brightness in the upper atmosphere from space

We present energy calculations for the basic parameters of a spectrophotometric system designed for recording the vertical distributions of the spectral brightness of hydroxyl airglow and the brightness of airglow from the green line of atomic oxygen in the upper layer of the Earth's atmosphere. We consider the scheme for conducting the “Hydroxyl” space experiment with instrumentation in the spectrophotometric system and methods for measuring the brightnesses of the indicated airglow components in sessions for observation of the Earth's night upper atmosphere in the altitude range 80–110 km from on board the International Space Station (ISS).

Comment on using auroral spectra to detect extraterrestrial life

Syun Akasofu,in an opinion published in Eos [1999], suggests using auroral spectra as a tool to detect extraterrestrial life. He argues that the green line of atomic oxygen at 557.7 nm wavelength is direct evidence for the existence of free oxygen in a planetary atmosphere. As the green line in the terrestrial aurora arises mostly from the fact that plants release abundant free oxygen into the atmosphere by the photosynthesis process, detecting an extraterrestrial aurora would indicate that the possibility of the presence of plant life is high. This idea is a good one because auroral spectra point to two key elements of the existence of life: atmospheric oxygen and a magnetic field. It also extends the search for extraterrestrial intelligence to the search for lower life forms.

Mechanism for the Green Glow of the Upper Ionosphere

The generation of the green line of atomic oxygen by dissociative recombination of O 2 + occurs by the capture of an electron into a repulsive state of O 2 followed by dissociation along another state of a different electronic symmetry. The two states are coupled together by mixed symmetry Rydberg states. Quantum chemical calculations give a rate coefficient at room temperature of (0.39 −0.19 +0.31 ) × 10 −8 cubic centimeters per second. The quantum yield of excited oxygen is within the range deduced from ground, rocket, and satellite observations. The rate coefficients and yields are needed in models of the optical emission, chemistry, and energy balance of planetary ionospheres.

Emission of forbidden red and green lines of atomic oxygen from the nocturnal F region

The O + 2 dissociative recombination quantum yields, f( 1S) and f( 1D), that have been deduced from nocturnal rocket measurements on the volume emission rates V(5577) and V(6300) in the equatorial F region have been analysed to see if they are consistent with the results of ab initio computations on dissociative recombination. In the case of the 557.7 nm emission the only serious problem is that the rocket f( 1S) values are much larger than expected in the region below about 220 km. The most interesting feature of the apparent f( 1D) altitude profile is that it is markedly influenced by the transport of the suprathermal O( 1D) atoms produced by the dissociative recombination.

The red and green lines of atomic oxygen in the nightglow of Venus

O( 1D) and O( 1S) , the excited states that give rise to the atomic oxygen red and green lines, are produced in the Venus nightglow in dissociative recombination of O 2 +. The emissions should also be excited by precipitation of soft electrons, the suggested source of the “auroral” emission features of atomic oxygen at 1304 and 1356 Å, which have been reported from observations of the Pioneer Venus Orbiter Ultraviolet Spectrometer. No emission at 6300 or 5577 Å was detected, however, by the visible spectrophotometers on the Soviet spacecraft Veneras 9 and 10 and upper limits have been placed on the intensities of these features. Here we evaluate the constraints placed on models for the auroral production mechanism by the Venera upper limits by modeling the intensities of the red and green lines in the nightglow. We combine a model for the vibrational distribution of O 2 + on the nightside of Venus with rate coefficients recently computed by Guberman for production of O( 1S) and O( 1D) in dissociative recombination of O 2 + from different vibrational levels. The integrated overhead intensities are 1 – 2 R for the green line and about 46 R for the red line.

The global characteristics of atmospheric emissions in the lower thermosphere and their aeronomic implications

The green line of atomic oxygen and the Herzberg bands of molecular oxygen as observed from the OGO-4 airglow photometer are discussed in terms of their spatial and temporal distributions and their relation to the atomic oxygen content in the lower thermosphere. Daily maps of the distribution of emissions show considerable structure (cells, patches, and bands) with appreciable daily changes. When data are averaged over periods of several days in length, the resulting patterns have occasional tendencies to follow geomagnetic parallels. The Seasonal variations are characterized by maxima in both the Northern and Southern Hemispheres in October, with the Northern Hemisphere having substantially higher emission rates. Formulae are derived relating the vertical column emission rates of the green line and the Herzberg bands to the atomic oxygen peak density. Global averages for the time period for these data (August 1967 to January 1968), when converted to maximum atomic oxygen densities near 95 km, have a range of 2.0 x 10 to the 11th power/cu cm 2.7 x 10 to the 11th power/cu cm.

Electron fluxes and correlations with quiet time auroral arcs

Primary electron fluxes, measured by two satellites as they crossed quiet time (Kp = 1, Σ Kp = 11+) auroral arcs, are presented for times near 1420 UT on November 12, 1972. The DMSP 30 satellite measured the optical intensity at 0.6–1.0 µm full width at half maximum (FWHM) and precipitated electrons with 0.22 ≤ E ≤ 19.7 keV near 2100 MLT. The 72-1 satellite crossed the auroral arc system near 2200 MLT and measured 0.36- to 16.5-keV electrons at all pitch angles. A detailed description of the electron morphology that includes comparisons of electron fluxes with optical intensities is presented. We find that the optical intensities extending from 2100 to 2200 MLT correlate best with electrons with E > 1 keV. The strongest emission bands at these near-infrared wavelengths are N2(IP) (first-positive band of N2) and N2+(M) (Meinel band of N2+). We estimate that between 4 and 10% of the primary electron energy input is converted to an optical intensity of 140 kR between 0.6 and 1.0 µm FWHM and is equivalent to a weak IBC 2 in the 5577-A green line of atomic oxygen.

Decay of the O I λ5577 line in meteor wakes

Multiple-exposure spectra of six meteors showing the auroral green line of atomic oxygen have been measured photometrically. The decay of the green line is described in terms of two parameters which are given as functions of height. It is shown that the maximum intensity occurs after a measurable time interval, which varies from 0.3 s at 115 km to 0.06 s at 105 km and decreases further with decreasing height. The subsequent decay rate is close to the natural rate (1 s−1) of the 1S state above 110 km, but increases with decreasing height to 3 s−1 at 100 km. The height of the green-line emission is consistent with most previous measurements, and corresponds with the height of the atmospheric atomic oxygen layer. The observations do not show a correlation of green-line characteristics with geomagnetic activity. Various possible excitation and quenching mechanisms are discussed.

Note: Excitation of the Auroral Green Line of Atomic Oxygen (^{1}S -> ^{1}D) by N_{2}(A ^{3}Σ_{u}^{+})

Note: Excitation of the Auroral Green Line of Atomic Oxygen (^{1}S -> ^{1}D) by N_{2}(A ^{3}Σ_{u}^{+})

The Green Line of Atomic Oxygen in the Day Airglow

Abstract It is argued from the observations of the red line that the rate coefficient for deactivation of the excited oxygen atoms in collisions with molecular oxygen cannot be much less than 10−10 cm3 sec−1 and that the solar flux in the region of 1450 A cannot be as large as the reported measured values. It is further argued that photodissociation of molecular oxygen and recombination of molecular ions are inadequate to explain the observations and that an additional mechanism is operative at high altitudes. The mechanisms of fluorescent excitation and of non-thermal excitation by photoelectrons are briefly examined and it is concluded that although the latter may be a significant source of excited atoms, neither mechanism explains the observed variability. It is suggested that the variability in red line intensities is associated with the presence of hot thermal electrons and sample calculations are presented of the altitude profiles that may result from this source.

Rocket Optical Observation of a Day-time Aurora

STUDIES of the day-time aurora have been restricted almost entirely to investigations by radio techniques. So far as we are aware the only published optical work is that by Noxon1 on the red and green lines of atomic oxygen. In this communication we report the preliminary results of an investigation of the spectral region 4000–5900 A obtained during a day-time aurora by means of a rocket probe launched from Fort Churchill, Manitoba, Canada.

Relative Intensities of the Oxygen Lines at 5577 A. and 6300 A. in the Night Sky

A PATROL spectrograph on loan from the U.S. International Geophysical Year Committee through the Air Force Cambridge Research Center has been operating at Invercargill since August 13, 1957. This spectrograph scans a 165° strip of sky along the spectral line, the strip of sky in this case lying along the geomagnetic meridian. With exposures of the order of four to five hours on the night sky, using film with Kodak 103a–F(3) emulsion, the spectrograph has recorded the red and green lines of atomic oxygen (6300 A. and 5577 A. of OI). A preliminary analysis of 220 spectra has been carried out for the period August 13–December 31, 1957.