Molecular Ions NO Research Articles

Comparison of the midlatitude model with low-latitude ion composition data

Comparisons of the midlatitude ion composition model (Danilov and Smirnova, 1994) developed for IRI with low-latitude ion composition measurements are presented. The comparison demonstrates, that the model by Danilov and Smirnova (1994) quite satisfactorily represents the ratio ϕ + of the two principal molecular ions NO + and O + 2 at altitudes 110–170 km. Some correction of ϕ + is probably needed for altitudes h < 100 km, but there are still very few data for the D-region ion composition at low latitudes. The comparison shows also that the daytime experimental values of the O + relative concentration R(O +) at altitudes 170–240 km exceed the model ones. A correction of the midlatitude R(O +)-profiles by 20–25% is needed. At night both ϕ + and R(O +) experimental values are higher than the ones in the Danilov and Smirnova (1994) model for ζ = 90°, which demonstrates a need to create a comprehensive model for night-time conditions.

Long-term changes of the mesosphere and lower thermosphere temperature and composition

A brief review of the recent publications on long-term trends of atmospheric and ionospheric parameters in the mesosphere and lower thermosphere is presented. The rocket measurements of the ion composition in the ionospheric E region are analyzed. A systematic decrease of the ratio of two principal molecular ions NO + and O 2 + from the sixties to the end of the eighties is detected. It is shown that the derived trends of the ion composition may be important in linking the temperature trends around the mesopause and the electron concentration trends in the E region.

A modelling study of the coupled ionospheric and thermospheric response to an enhanced high-latitude electric field event

A modelling study of the effect of a short-lived, localized enhancement in the high-latitude dawnside convection electric field has been made using the Sheffield/UCL/SEL (Boulder) coupled ionosphere/ thermosphere model. The conditions imposed on the model are intended to represent a single fluctuation of the type often observed in this region and thought to be responsible for a number of dynamic effects in both the ionosphere and thermosphere. Results from the simulation show frictional heating of both ions and neutrals producing an expansion of the atmosphere. The ionospheric expansion, when combined with greatly enhanced chemical reaction rates, leads quickly to the establishment of an ionospheric trough accompanied by significant increases in the proportions of the molecular ions NO + and O + 2. The initial expansion of the atmosphere is followed by a subsequent relaxation, leading to the formation of a large-scale gravity wave which propagates equator-wards and polewards from the event region. The dynamics of the complete coupled system during the event are studied, with particular attention to coupling and feedback processes.

Chemistry of the nightside ionosphere of Venus

We have constructed a one-dimensional model of the nightside ionosphere of Venus in which it is assumed that the ionization is maintained by day-to-night transport of atomic ions. Downward fluxes of O +, C + and N + in the ratios measured on the dayside at high altitudes are imposed at the upper boundary of the model (about 235 km). We discuss the resulting sources and sinks of the molecular ions NO +,CO +,N 2 +,CO 2 + and O 2 +. As the O + flux is increased, the peak density of O + increases proportionally and the altitude of the peak decreases. The O 2 + peak density is approximately proportional to the square root of the O + flux and the peak rises as the O + flux increases. NO + densities near the peak are relatively unaffected by changes in the O + flux. If the ionosphere is maintained mostly by transport, the ratio of the peak densities of O + and O 2 + indicates the downward flux ofO +, independent of the absolute magnitudes of the densities. The densities of mass-28 ions are, however, still considered to be the most sensitive indicator of the importance of electron precipitation. We examine here the inbound and outbound portions of six early nightside orbits with low periapsis and use data from the Pioneer Venus orbiter ion mass spectrometer, the retarding potential analyzer and the electron temperature probe to determine the relative importance of ion transport and electron precipitation. For most of the orbits, precipitation is inferred to be of low to moderate importance. Only for orbit 65, which was the first nightside orbit published by Taylor et al. [ J. geophys. Res. 85, 7765 (1980)] and for the inbound portion of orbit 73 does the ionization structure appear to be greatly affected by electron precipitation.

UV-light-induced defects in alkali-halide crystals KBr and KI with molecular ions NO −2

The investigation of the UV-light-induced defects in alkalihalide crystals with molecular ions NO − 2 has been performed in the temperature range from 4 to 300 K. As a result we obtain the characteristic changes of electronic absorption band of NO − 2- ion after uv-light irradiation at 4,2 K. The experiments is obtained that the new continuous band is connected with the V K-center which is created effectively in the alkali-halide crystals with molecular ions NO − 2 by UV-irradiation.

Thermal ion complexities observed within the spacelab 2 bay

Examples of prominent thermal ion composition variations characteristic of the Shuttle environment as observed from within the open cargo bay on the Spacelab 2 mission are discussed. Although the prominent ionization source is the inflow of the ambient plasma (in particular O +), water ions of Shuttle origin were present throughout the mission, and there was evidence for a local source of molecular ions NO +and/or O + 2 which also exist in the ionosphere. Bursts in the fluxes of these contaminant species were frequently observed coincident with thruster firings while O + depletions or enhancements could occur depending on the scattering geometry. These effects bring into question whether reliable ambient thermal ion measurements can be made from the vicinity of such vehicles. The presence of significant inflows of contaminant ions into the bay within the Shuttle wake also indicates that Shuttle emissions play a significant role in the evolution of its wake structure.

Positive ion composition and derived particle heating in the lower auroral ionosphere

Two positive ion mass spectrometers of the University of Bern were launched from Kiruna on two Taurus-Orion payloads on 16 November (salvo B) and 30 November (salvo A2) as part of the European Energy Budget Campaign 1980. The payloads also included experiments of the University of Illinois for measurements of electron density and energetic particles. The ionization sources were predominantly precipitating electrons in salvo B and precipitating protons in salvo A2. Positive ion composition is evaluated from the ascent measurements in the altitude range 60–170 km. Altitude profiles of total and partial ion densities are calculated from the mass spectrometer ion currents normalized to electron density measurements at 90 km. Typical characteristics of the positive ion composition under winter-time auroral conditions are large NO + O + 2 density ratios, with maximum values of 20 at 118 km in salvo B and 100 at 100 km in salvo A2, respectively. The transition height from dominant proton hydrates H +(H 2O) 3 and H +(H 2O) 4 to dominant molecular ions NO + and O + 2 occurred at 79 km in salvo B and 76 km in salvo A2. The measured N + and O + number densities are generally in good agreement with model calculations. From these calculations the measured 28 + is interpreted mainly as N + 2 above 110 km in salvo B and above 105 km in salvo A2, and is Si + below these altitudes. Electron density and ion composition data are used for the calculation of ion-electron pair production rates in both flights. The energy flux of precipitating particles, derived from the altitude integrated electron-ion pair production, is 0.85 mW m −2 in salvo B and 1.00 mW m −2 in salvo A2.

On ionization of the lower mesosphere

Measurements made by rocket and ground based techniques reveal the presence of two distinct types of electron density profiles in the lower mesosphere. In one type, the electron density, N e , decreases monotonically below 70 km and assumes a value ⩽ 10 cm −3 at 60 km. In the other, the value of N e ~ 100 cm −3 in the 60–70 km altitude region with an occasional maximum around 65 km followed by a minimum around 70 km are observed. Positive ion composition measurements sometimes show the presence of molecular ions NO + and O 2 + around 65 km along with the hydrted protons. The negative ion composition measurements have the age old controversy about the predominance of CO 3 − or NO 3 − and their hydrates. Using the presently known ion chemical scheme in which both positive and negative ion are considered, an attempt has been made in this paper to examine how far the above mentioned features could be reproduced, theoretically, by varying the neutral temperature and the densities of minor neutral constituents. The implications of these variations on the ionization of the lower D-region are discussed.

Ion composition irregularities and ionosphere-plasmasphere coupling: Observations of a high latitude ion trough

Atomic and molecular ion composition results from the polar orbiting OGO-4 and 6 satellites identify a high latitude trough (HLT) in the topside ionosphere (600–1000 km), as a repeatable signature, separate from the light ion trough (LIT) in H + and He +, associated with the plasmapause. The HLT is often seen as a narrow (5°–10° latitude) depletion of a factor of 3 or more in the concentrations of the atomic ions H +, O +, N + and He +, accompanied by similarly abrupt enhancements in the concentrations of the molecular ions NO +, N 2 + and O 2 +. The coexistence of the HLT and the molecular ion peaks near 70° magnetic latitude suggests that the HLT may be associated with soft electron precipitation in the auroral zone/cusp region. This assumption is tentatively supported by the observation that low frequency hiss enhancements are observed simultaneously with the HLT. The presence of the HLT in addition to the LIT and its associated ‘plasmatail’ structure presents an added complication for identifying ionospheric signatures of ionosphere-plasmasphere coupling, illustrating the need for studies of energetic as well as plasma convection mechanisms involved in the coupling processes.

Ionospheric constraints of mesospheric nitric oxide

In view of the unreliabilities of γ-band estimates of mesospheric nitric oxide, ionospheric measurements of different types, including some controlled experiments specifically undertaken for this purpose, have been used to define an acceptable range of NO concentration. The ionospheric observations used are (i)the level of ionization reversal with solar activity ( Mitra, 1966), (ii) the gradual loss of solar control in the diurnal variation of electron density at levels below 70 km ( Mitra, 1969), (iii) magnitude and changes in the ratio of the two molecular ions NO + and O 2 +. The controlled experiment was the continuous monitoring of changes in mesospheric ionization profiles with the high power wave interaction facility at Pennsylvania State University during selected solar flare events. The flare measurements provide an NO profile similar to, but displaced downwards in height, from that given by Meira's γ-band measurements. The sharp ledge in electron density observed around 85 km requires a sharper valley in NO distribution at this height and the observed electron and positive ion densities at 70 km require that Meira's NO concentration should be increased by a factor between 5 and 7 at 70 km.

High latitude minor ion enhancements: A clue for studies of magnetosphere-atmosphere coupling

Unexpectedly abrupt and pronounced distributions of the thermal molecular ions NO +, O 2 + and N 2 + are observed at mid and high latitudes by the OGO-6 ion mass spectrometer. Normally considered trace constituents of the topside ionosphere, following magnetic storms these minor ions may reach concentration levels exceeding 10 3 ions/cm 3 at altitudes as great as 1000 km, suggestive of scale heights well in excess of those inferred from low and mid-latitude measurements, under relatively undisturbed conditions. The high latitude ion enhancements are sometimes observed to be narrowly defined in time and space, with molecular ion concentrations changing by as much as an order of magnitude between successive orbits. Assuming that these localized ion enhancements are associated with energetic perturbation of the lower ionosphere, it would follow that energy coupled to the lower altitudes may at times also be narrowly distributed in time and space within a given hemisphere. This view seems consistent with the observation that local magnetic substorm activity is closely associated in time and space with the anomalous ion enhancements. These results suggest that the search for a link between solar-magnetic processes and perturbation of the lower atmosphere may well benefit from phenomenological investigations, in support of statistical methods attempted previously.

High resolution D‐region measurements at Arecibo

D‐region electron densities have been measured with a height resolution of less than 1 km using the incoherent scatter technique with coded pulses. Using a theoretical production model and the measured densities, recombination coefficients were computed for the altitude range from 80 to 95 km. The effective recombination coefficient decreases across the D‐region ledge from a value of about 2 × 10−5 cm3 sec−1 below the ledge to a value of the order of 1 to 5 × 10−7 above. The change is presumably due to a transition from water cluster ions to the molecular ions NO+ and O2+.

Implications for ionospheric chemistry and dynamics of a direct measurement of ion composition in theF2region

The positive ion mass spectrometer on the Geoprobe (NASA 8.25) rocket measured the concentrations of O+, N+, H+, He+, NO+, O2+ and N2+ between 200 km and peak altitude, 630 km, at 1300 EST on March 2, 1966, above Wallops Island, Virginia. The dominant ion throughout the altitude range was O+, with a maximum concentration of 5 × 105 ions/cm³ at 260 km. The first detection of H+ occurred at 230 km, its concentration increasing to 7 × 10³ ions/cm³ at peak altitude. The H+/He+ ratio was never lower than 6.0, the value at 420 km. The molecular ions NO+ and O2+ were important constituents at 200 km, the concentration of each being 5 × 104 ions/cm³; they fell off rapidly above this altitude. Photochemical equilibrium held for He+ up to 400 km with a rate coefficient of about 0.5 × 10−9 cm³ sec−1 for charge transfer with N2, in agreement with laboratory measurement. Charge exchange equilibrium of H+ with O+, O, and H held up to 350 km; the temperature derived for the neutrals below 350 km, where it is believed that Tg = Ti, was 850°K, which agrees with Tg measured by companion neutral particle sensors. From the variation of [H+]/[O+] and an [O] distribution based on a simultaneous EUV measurement, a profile of [H] in the chemical equilibrium region was calculated. The derived H concentrations are higher than the Jacchia 1964 Model predictions, but agree with Explorer 32 spectrometer results. Analysis indicates that N+ was not in diffusive equilibrium at 300 km, and that a neutral wind having a field-aligned downward component of 25 m/sec is required to produce the observed N+ scale height at this altitude. Distributions of O+ and H+ above 300 km were derived by solving the continuity equations along field lines; an upward H+ flux of 1.5 × 108/cm² sec was required to reproduce the observed profiles, indicating that the critical flux is at least an order of magnitude higher than previously believed.