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1.
Recent improvements in rocket-borne mass spectrometer technology have made it possible to measure lower ionospheric ions with greater sensitivity and to extend the measurements to lower heights. The improvements made to the instrument and positive ion results from a flight of this instrument will be reported here. In addition to the previously known ions, such as NO+(H2O)n and H+(H2O)n, new ion species were found. The total fractional count rate of these ions was found to be constant with height indicating an upper altitude source. Possible identifications of these ions are proposed along with possible production mechanisms.  相似文献   

2.
The nature of negative ions in the altitude region 42–45 km has been investigated by means of a balloon borne mass spectrometer. Apart from the NO3− and HSO4− clusters, ions with different cores, which can be identified as CO3−, HCO3−, Cl− and ClO3− were observed. The spectra have been used to estimate the sulfuric acid number density at 45.2 and 42.3 km altitude.  相似文献   

3.
We use a 1-D chemical diffusive model, in conjunction with the measured neutral atmospheric structure, to analyze the Voyager RSS electron density, ne, profiles for the ionospheres of Jupiter and Saturn. As with previous studies we find serious difficulties in explaining the ne measurements. The model calculates ionospheres for both Jupiter and Saturn with ne peaks of 10 times the measured peaks at altitudes which are 900–1000 km lower than the altitude of peaks in the RSS electron densities. Based on our knowledge of neutral atmospheric structure, ionization sources, and known recombination mechanisms it seems that, vibrational excitation of H2 must play some role in the conversion of slowly radiatively recombining H+ ions to the relatively more rapidly recombining H2+ and H3+ ions. In addition, vertical ion flow induced by horizontal neutral winds or electric fields probably also play some role in maintaining the plasma peaks observed both for Jupiter and Saturn to be at high altitudes. For the ionosphere of Saturn, the electron densities are affected by a putative influx of H2O molecules, ΦH2O, from the rings. To reproduce the RSS V2 exit ne results model requires an influx of ΦH2O 2 × 107 molecules cm−2 s−1 without invoking H2f vibrational excitation. To maintain the model ne peak at the measured altitude vertical plasma drift maintained by meridional winds or vertical electric fields is required. The amounts of H2O are consistent with earlier estimates of Connerney and Waite (1984) and do not violate any observational constraints.  相似文献   

4.
High resolution E-region measurements carried out on 16 November 1983 using the EISCAT incoherent scatter radar are presented. The experiment was monostatic with a vertical radar beam, and it was based on a Barker-coded four-pulse code on one frequency channel and Barker-coded single pulses on three channels. The basic integration time was 15 s and the spatial resolution 450 m. The results reveal a short-lived but intense thin sporadic E-layer at 18:00–18:06 U.T. at an altitude of about 106 km. Both before and during the event, downward ion velocities of the order of 100 m s−1 are observed above this height. A convergent null in the vertical ion speed is occasionally seen at the layer altitude. The layer occurrence is associated with auroral arcs drifting across the radar beam. Simultaneous observations of the STARE radar show an ionospheric electric field of 25–30 mV m−1. The field always has a westward component, which is in accordance with the observed downward plasma flow. Most of the time when the layer is intense, the field points into the NW-sector. Theoretically, this field direction should create convergent vertical plasma motion. Therefore it is suggested that the observed Es-layer is created by the action of the auroral electric field rather than by the wind shear mechanism.  相似文献   

5.
Co-ordinated rocket measurements of the O2(a1Δg−X3Σg−) Infrared Atmospheric (0-0) band emission profile and the atomic oxygen densities in an undisturbed night-time atmosphere are used to investigate the processes responsible for the excitation of O2(a1Δg) in the terrestrial nightglow. It is shown that three-body recombination of atomic oxygen, and subsequent energy transfer processes, can explain only part of the observed emission profile and that at least two other sources of O2(a1Δg) emission must exist. One of these additional sources, responsible for most of the emission observed below 90km, is identified as arising from the night-time residual of the very large dayglow 1Δg population. The other additional source is required to explain most of the emission observed above 95km. The processes responsible for this high altitude component cannot be identified but the vertical distribution of the required source function strongly resembles the profile of the atomic oxygen density squared and suggests that a two-body radiative recombination process may be involved. However, the measured zenith emission rates can also be explained without the high altitude source of O2(a1Δg) if optical emission at 1.27 μm was induced by the rocket as it penetrated the nightglow layer.  相似文献   

6.
A detailed analysis of the D-region ion composition measurements performed by Zbinden et al. (1975), during a winter day of high ionospheric absorption, has been carried out. The study examines the interactive mesosphere-D-region processes which occur in such anomalous conditions and their implication for water cluster ion chemistry. Two clustering regimes for NO+ have been observed in the data. Association with N2 is identified as the dominant process below 76 km. Between 76 and 78 km altitude the effective loss rate of NO+ drops by two orders of magnitude. Above 77 km, the three-body reaction NO+ + CO2+M→NO+CO2+M seems to be the main NO+ loss. A mesospheric temperature profile could be derived from the ion composition data. This indicates the presence of a strong inversion above 76 km altitude. The wavelike structure obtained, is shown to be consistent with in situ winter temperature measurements. The sharp suppression of the N2 association reaction could, thus, be explained by an increase in the collisional break-up of the NO+N2 ion because of the enhanced temperature. In conclusion, our study indicates that, besides the increase in the production of NO+ and O2+, due to an enhancement in the minor ionizable constituents, an additional thermal mesosphere-D-region interaction seems necessary to explain this winter anomalous ion composition data.  相似文献   

7.
The absorption of solar ionizing radiation during twilight is investigated. Ion production rates are obtained as a function of altitude and twilight intensities and altitude profiles of emissions arising from the fluorescence of solar ionizing radiation are calculated for various solar depression angles. For an atmosphere with an exospheric temperature of 750°K, the predicted overhead intensity from fluorescence of the O+(2P — 2D) lines at 7319–7330 diminishes from 175 R at dusk to 10 R at a solar depression angle of 10°. The predicted overhead intensities from fluorescence of the N2+ Meinel and first negative systems are respectively about 175 R and 20 R at dusk diminishing to respectively 1.5 R and 0.1 R at a solar depression angle of 10°.

It is suggested that a charge transfer reaction of O+2D in N2 is a significant source of N2+ ions. This reaction offers a possible explanation for the high apparent rotational temperatures in the first negative system observed by Broadfoot and Hunten. Other excitation and ionization mechanisms are briefly discussed.  相似文献   


8.
We have studied the escape of neutral helium from the terrestrial atmosphere through exothermic charge exchange reactions between He+ ions and the major atmospheric constituents N2, O2, and O. Elastic collisions with the neutral background particles were treated quantitatively using a recently developed kinetic theory approach. An interhemispheric plasma transport model was employed to provide a global distribution of He+ ions as a function of altitude, latitude and local solar time and for different levels of solar ionization. Combining these ion densities with neutral densities from an MSIS model and best estimates for the reaction rate coefficients of the charge exchange reactions, we computed the global distribution of the neutral He escape flux. The escape rates show large diurnal and latitudinal variations, while the global average does not vary by more than a factor of three over a solar cycle. We find that this escape mechanism is potentially important for the overall balance of helium in the Earth's atmosphere. However, more accurate values for the reaction rate coefficients of the charge exchange reactions are required to make a definitive assessment of its importance.  相似文献   

9.
The composition, energy and angular characteristics of upward flowing ionospheric ions at altitudes greater than ～ 20,000 km have been studied by means of the PROGNOZ-7 ion composition experiment. Very narrow beams, having widths corresponding to a mirroring altitude of the order a few thousand kilometers or less, may be found up to altitudes exceeding 30,000 km on the nightside. At much higher altitudes and in regions connected to the dayside/flank boundary layer and plasma mantle, the beams are much broader than expected from adiabatic particle motions from an ionospheric source/acceleration region, suggesting that pitch angle scattering or transverse acceleration processes are present there. Considerable mass dispersion effects have also been observed in some upward flowing ionospheric ion beams. The peak energy for the O+ ions may differ by several keV compared to that for the H+ ions in one and the same ion beam at altitudes above ～ 20,000 km. The O+ ions in these beams have gained considerably more energy than H+ in the acceleration process. Many examples with a much higher O+ than H+ content in the beam have been observed. Possible mechanisms giving rise to the observed effects are discussed, one being several kV of potential drop below the neutral H, O-crossover altitude (500–1500 km). At altitudes where the upflowing ionospheric ions are intermixed with magnetosheath ions, mass dispersion effects are also observed. This dispersion often appears to be the result of a velocity filtering effect caused by the dawn-dusk electric field (earthward convection).  相似文献   

10.
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+,N2+,CO2+ and O2+. As the O+ flux is increased, the peak density of O+ increases proportionally and the altitude of the peak decreases. The O2+ 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 O2+ 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.  相似文献   

11.
W.J. Borucki  R.C. Whitten  E. Barth 《Icarus》2006,181(2):527-544
The electrical conductivity and electrical charge on the aerosols in atmosphere of Titan are computed for altitudes between 0 and 400 km. Ionization of methane and nitrogen due to galactic cosmic rays (GCR) is important at night where these ions are converted to ion clusters such as CH+5CH4, C7H+7, C4H+7, and H4C7N+. The ubiquitous aerosols observed also play an important role in determining the charge distribution in the atmosphere. Because polycyclic aromatic hydrocarbons (PAHs) are expected in Titan's atmosphere and have been observed in the laboratory and found to be electrophilic, we consider the formation of negative ions. During the night, the very smallest molecular complexes accept free electrons to form negative ions. This results in a large reduction of the electron abundance both in the region between 150 and 350 km over that predicted when such aerosols are not considered. During the day time, ionization by photoemission from aerosols irradiated by solar ultraviolet (UV) radiation overwhelms the GCR-produced ionization. The presence of hydrocarbon and nitrile minor constituents substantially reduces the UV flux in the wavelength band from the cutoff of CH4 at 155 to 200 nm. These aerosols have such a low ionization potential that the bulk of the solar radiation at longer wavelengths is energetic enough to produce a photoionization rate sufficient to create an ionosphere even without galactic cosmic ray (GCR) bombardment. At altitudes below 60 km, the electron and positive ion abundances are influenced by the three-body recombination of ions and electrons. The addition of this reaction significantly reduces the predicted electron abundance over that previously predicted. Our calculations for the dayside show that the peaks of the charge distributions move to larger values as the altitude increases. This variation is the result of the increased UV flux present at the highest altitudes. Clearly, the situation is quite different than that for the night where the peak of the distribution for a particular size is nearly constant with altitude when negative ions are not present. The presence of very small aerosol particles (embryos) may cause the peak of the distribution to decrease from about 8 negative charges to as little as one negative charge or even zero charge. This dependence on altitude will require models of the aerosol formation to change their algorithms to better represent the effect of charged aerosols as a function of altitude. In particular, the charge state will be much higher than previously predicted and it will not be constant with altitude during the day time. Charging of aerosol particles, whether on the dayside or nightside, has a major influence on both the electron abundance and electrical conductivity. The predicted conductivities are within the measurement range of the HASI PWA instrument over most but not all, of the altitude range sampled.  相似文献   

12.
A sky-mapping filter photometer has been used to determine the 630.0 nm airglow enhancement produced by explosive release of 3 × 1026 CO2 molecules into the F-region at 320 km altitude on 8 September 1982 as part of project BIME. The enhancement is produced when COg molecules engage in atom transfer with the F-region O+ ions to form O2+ ions, which subsequently dissociatively recombine with the ambient electrons to produce O(1D) atoms to yield the 630.0 nm radiation. The morphology of the enhanced airglow region has been traced in a series of 630.0 nm intensity contour maps as a function of time, the enhancement reaching a central brightness of approximately 400 R about 2 min after release and a diameter of 250 km some 3 min after release. The measurements of central intensity and enhanced region radius as a function of time are compared with model calculations by Mendillo and Herniter of diffusive expansion of CO2 molecules from either a point release or from an initial, extended volume. While peak intensities are reasonably reproduced, the measured decay of the 630.0 nm intensity and the growth in size of the enhanced region are rather different from the model predictions. The measured 200 m/s drift southeastward of the enhanced region is consistent with the motion of the neutral thermosphere determined from optical doppler shifts less than an hour earlier.  相似文献   

13.
On the basis of observations in the dayside magnetosphere of the O+ and H+ ion densities as function of radial distance under fairly undisturbed and under storm conditions it is argued that acceleration of the hot magnetospheric ions of ionospheric origin cannot be limited to the outer parts of the field tubes. The extraction process seems to work below 1000 km altitude in storm conditions and to have a fairly small extension in altitude. The acceleration mechanism(s) do(es) not affect only one ion species. Variation in the altitude of the extraction of ionospheric ions is the most likely reason for the observed variations in the n(O+)/n(H+) ratio. Extraction of ionospheric ions into the magnetosphere does not seem to be a main cause of the storm time density decrease of the ionosphere.  相似文献   

14.
Vertical fluxes of ionization in the F2 region have been measured by the incoherent scatter technique over Millstone Hill in 1969. The results obtained near midnight for the region above hmaxF2 have been examined to determine whether there is a significant flux of ionization from the magnetosphere to the ionosphere that serves to maintain the F-layer. It is found that H+ ions are a minor constituent over the altitude range in which useful measurements can be made, so that any conclusion must rest upon properly interpreting the observed O+ fluxes. By selecting periods when the layer did not appear to be decaying rapidly it was hoped to find cases where the O+ flux did not vary with altitude in the range 500 h 800 km (i.e. where losses are unimportant), since this would imply that the flux is of magnetospheric origin.

While three cases exhibited this behaviour, the majority exhibited a decrease in the O+ flux with height, indicating that the layer was descending. Attempts to correct for this were made, and the average flux from the magnetosphere was estimated as 3 × 107 el/cm2/sec. This is in fair agreement with other recent estimates, and implies that at this latitude the ionosphere is not maintained solely by the magnetospheric flux. Moreover, large increases in flux that could give rise to nocturnal increases in the total content of the layer do not appear to have been seen.  相似文献   


15.
A general analysis of ionospheric conditions has been made in the light of possible ionic reactions occurring in the upper atmosphere. Data obtained on various parameters, such as ionic production and recombination, show that precise knowledge of the spectral distribution of solar radiation is needed and that other experimental determinations on dissociative recombinations are required.

The ionic complexity of the ionosphere is underlined by describing how the atomic ions O+ and N+ react with N2, O2 and NO molecules. The behavior of the molecular ions N+2, O+2and NO+depends on a group of simultaneous processes involving charge transfers and ionatom interchanges which are more important than dissociative recombinations. The altitude distribution of ions is exemplified by discussing the relative importance of various loss coefficients in the D-, E- and F-regions. It is seen that molecular nitrogen ions are subject to important charge transfer processes, that nitric oxide ions are always final products destroyed only by dissociative recombination. Additionally, the entire production of atomic oxygen ions is related to the photoionization of molecular nitrogen. Some information is also given on possible anomalies in the ratio of O+2 and NO+ densities in the lower ionosphere. From the lack of sufficient experimental information on ionic processes it is shown that a precise analysis of ionospheric behavior remains highly speculative.  相似文献   


16.
A chemical model of negative ions in the troposhere (0–15 km) is presented. This model is an extension of the negative ion composition model in the lower stratosphere (Kawamoto and Ogawa, 1984, Planet. Space Sci. 32, 1223) with some modifications. The computed result shows that the predominant ions are NO3−HNO3H2O below 10km and NO−3(HNO3)2 above 10km, and that the fractional abundance of cluster ions having a HSO−4 core increases with height below 12km and decreases with height above it. The ions having CO−3 cores are at most 2% in fractional abundance. The other kinds of negative ions are far smaller in fractional abundance than the NO−3, HSO−4 and CO−3 core ions. The result is compared with the two mass spectrometric observed results (Heitmann and Arnold, 1983, Nature, Lond. 306, 747; Perkins and Eisele, 1984, J. geophys. Res. 89, 9649). The problems on the tropospheric negative ions which arose are discussed.  相似文献   

17.
The properties of energetic (65–95 keV) cometary water-group ions in the extended solar wind pick-up region surrounding comet Giacobini-Zinner are examined using data from the EPAS instrument on the ICE spacecraft. In the outer part of this region, extending from cometocentric distances of several hundred thousand to a few million kilometres (the limit of pick-up ion detectability), it is found that large modulations of the ion flux occur (with JMAX/JMIN 102-103) which are related to the direction of the magnetic field. It is also found that the ions stream in a direction which is intermediate between the directions of the solar wind flow and the E × B drift, and that ions are present at energies somewhat above the local pick-up energy. These properties indicate that the waves which are excited by the unstable “ring-beam” pick-up ion velocity distributions do result in significant scattering of the ions in this region, both in pitch angle and in energy, but that they have insufficient amplitude to scatter the ions into near isotropy in the solar wind frame. Closer to the comet (but still upstream from the bow shock), the ion flux modulations are considerably reduced in amplitude and the ions respond less to the E × B drift, indicating that the ions are scattered nearer to isotropy in this region. Inbound, this transition takes place relatively abruptly at a distance of 4 × 105 km in association with an increase in the solar wind speed, after which the ion flux increases, and ceases to be modulated by the field direction, while the streaming direction is continuously antisolar and unmodulated by the direction of the E × B drift. Outbound, weak vestiges of the ring-beam ion anisotropy are present in the region immediately upstream from the bow shock (at −1 × 105 km), but these become more marked at distances in excess of t4 × 105 km, increasing gradually with increasing distance from the comet. It is shown that the evolution of the ion properties is qualitatively consistent with expectations based on quasi-linear diffusion of the ions by the magnetosonic waves observed during the encounter.  相似文献   

18.
For the first time, height profiles of the stratospheric negative ion composition are presented. The results are from two nights of balloon borne mass spectrometers and cover an altitude range from 23.8 to 38.9 km. Below approx. 30km, NO?3 · mHNO3 ions are dominant. These are replaced by HSO4? · nH2SO4 · oHNO3 ions above this height. There are indications that the most abundant ions above 32 km have masses greater than 280 atomic mass units (amu), the instruments' mass range. The fractional ion count rates as a function of altitude are presented and their significance for neutral trace gas analysis and ion sampling is discussed.  相似文献   

19.
On 14 July 1974 the Atmosphere Explorer-C satellite flew through an aurora at F-region altitudes just after local midnight. The effects of the particle influx are clearly evident in the ion densities, the 6300 Å airglow, and the electron and ion temperatures. This event provided an opportunity to study the agreement between the observed ion densities and those calculated from photochemical theory using in situ measurements of such atmospheric parameters as the neutral densities and the differential electron energy spectra obtained along the satellite track. Good agreement is obtained for the ions O2+, NO+ and N2+ using photochemical theory and measured rate constants and electron impact cross sections. Atomic nitrogen densities are calculated from the observed [NO+]/[O2+] ratio. In the region of most intense electron fluxes (20 erg cm−2 sec−1) at 280 km, the N density is found to be between 2 and 7 × 107 cm−3. The resulting N densities are found to account for approx. 60% of the production of N+ through electron impact on N and the resonant charge exchange of O+(2P) with N(4S). This reaction also provides a significant source of O(1S) in the aurora at F-region altitudes. In the region of intense fast electron influx, the reaction with atomic nitrogen is found to be the main loss of O+(2P).  相似文献   

20.
Ion velocity distributions in the auroral ionosphere   总被引：1，自引：0，他引：1  
For application to studies of the auroral ionosphere we have calculated the velocity distribution of the ions in a weakly-ionized plasma subjected to crossed electric and magnetic fields. We have retained enough terms in the series expansion of the distribution to enable us to determine under what conditions departures from the Maxwellian form become significant and what the nature of these departures is, but we cannot calculate precise values of the distribution function when the departures are large. Departures are negligibly small under conditions appropriate to the auroral ionosphere at low altitudes, where the ion-neutral collision frequency is much larger than the ion cyclotron frequency. At altitudes above about 120 km, however, the magnitude of the departures varies little with altitude. Electric fields greater than 25 mV m−1 cause departures from the Maxwellian distribution that are greater than 20 per cent at random velocities equal to or greater than twice the mean thermal speed of the ions. Under almost all conditions we find that the distribution is depleted in ions moving parallel to the magnetic field relative to those moving perpendicular, an effect that might be detectable in ionospheric measurements of ion temperature.  相似文献   

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