共查询到20条相似文献，搜索用时 293 毫秒
1.
This paper presents the results of a recent rocket firing through a quiet, mid-day E-region in which measurements of ionospheric electron densities and electron temperatures were made using improved diagnostic techniques. Excellent agreement was found to exist between the in-situ measurements of electron density and those deduced from ionograms obtained during the flight using ground based equipment. Measurements of the contact potential difference existing between the two graphite coated grids forming the electron temperature probe demonstrated that serious errors can be introduced into the electron temperature measurements if not taken into account and showed further that appreciable changes in the contact potential difference can occur during a short flight. The results of the flight indicate that the modifications made to both experiments represent significant improvements and demonstrate that the data outputs of each experiment are in a convenient form to be electronically stored, read at a subsequent time compatible with the telemetry sampling and telemetred to ground using only a small number of low bandwidth channels. 相似文献
2.
The ionization structure of the auroral arc was measured on a sounding rocket which penetrated into a bright auroral arc. The E-region electron density becomes large (2 ～ 5 × 105 el/cm3 only in the moving auroral arc, whose N2+ 4278 Å brightness is 1 ～ 2·5 kR. The electron density in the D-region beneath the lower boundary of the arc (75 ～ 98 km in altitude) is also considerably enhanced to 2 ～ 5 × 104 el/cm3.The observed E-region electron density can be interpreted theoretically as due to the direct ionization by precipitating electrons, whose energy spectrum is approximately represented by an exponential type having the characteristic energy of 2 keV. The correlation between the electron density and the N2+ 4278 Å brightness can be reasonably explained by considering the simultaneous effects on the ionization and the optical excitation caused by the primary electrons having a flux of 9 × 109 el/cm2/sec per 1 kR of the 4278 Å emission.Further analyses using the electron density data from four other sounding rockets have shown that the D-region ionization has good correlations to the cosmic noise absorption (CNA) and the magnetic substorm activities observed simultaneously at the ground station, whereas it has poor correlation to the same quantity of the E-region measured in the same experiment. It is found that the observed D-region ionization is much larger than that predicted by the theory which takes into account the Bremsstrahlung X-ray ionization along with the direct impact ionization when it is applied to the precipitating electron flux spectrum consistent to the E-region ionization and optical excitation.After all the present experimental results suggest a dual nature of the electron precipitation spectrum in the substorm, i.e. the softer part which is localized in the auroral arc and the harder part which is spatially wide-spread over the substorm area. 相似文献
3.
Data from eight auroral ion composition measurements, seven of which have been reported in the literature, are analyzed and compared in terms of a single model format. We find, contrary to conclusions published previously for two of the experiments, that there is no discrepancy concerning O+ ions. In general, the mean CIRA 1972 neutral model is found to be quite suitable as a representative of the major gas composition required for auroral E-region calculations which agree with the data. Nitric oxide profiles inferred from analysis of the data range from about normal non-auroral E-region nitrix oxide distributions with peak concentrations near 108 cm?3 to profiles with peak populations near 109 cm?3. Although the higher concentrations are generally correlated with intense aurora, we acknowledge that the length and strength of auroral activity prior to the individual rocket flights can have an even greater bearing, at times, on the NO “snapshot” profile deduced from the auroral ion composition data. 相似文献
4.
Low and mid-latitude lower E-region electron temperature profiles which were obtained by means of an insitu probe were collected. Profiles which are discussed here cover the heights of 90–120 km and measurement reliability at these heights is discussed mainly in terms of electrode contamination and aerodynamical heating.Although measurement errors might exist in some of the electron temperature profiles, it is conclusively described that daytime electron temperature is very often much higher than the possible neutral temperature and Te ≈ Tn is rarely seen. 相似文献
5.
F. Primdahl A. Bahnsen M. Ejiri P. Høeg G. Marklund B.N. Mæehlum J.K. Olesen E. Ungstrup L.J. Zanetti 《Planetary and Space Science》1984,32(5):561-583
Results are reported from a rocket experiment conducted at Søndre Strømfjord, Greenland, on 22 August 1976, at 16.00 M.L.T. A series of plasma, particles, and fields and wave experiments were carried on board the payload, and the venture was supported by data from the AE-C satellite and by groundbased ionosondes and magnetometers at the launch site and at Godhavn. Two regions of field-aligned electron precipitation, electron density and temperature enhancements, and field-aligned upflowing current sheets were intercepted by the rocket. The density enhancements were also observed by groundbased ionosondes. Significant discrepancies were found between the currents carried by the streaming electrons in the 0.15–10 keV range and the upflowing currents seen by the on board magnetometer, suggesting that the upflowing current could not be the primary driver of the electron acceleration mechanism. The E-region was unstable to the combined Gradient-Drift and Farley-Buneman instability, and plasma turbulence was observed in situ, but the absolute density fluctuations were too small to return detectable HF-radar power to the ground. 相似文献
6.
Quantitative estimates of ionization sources that maintain the night-time E- and F-region ionosphere are given. Starlight (stellar continuum radiation in the spectral inverval 911–1026 Å) and resonance scattering of solar Ly-β into the night sector are the most important sources in the E-region and are capable of maintaining observable electron densities of order (1–4) × 103 cm?3. Starlight ionization rates have substantial variations (factors of 2–4) with latitude and time of year since the brightest stars in the night sky occur in the southern Milky Way and Orion regions. In the lower F-region the major O+ source in the equatorial ionosphere is 910 Å radiation from the O+ recombination in the F2-region, whereas in the extratropical ionosphere interplanetary 584 Å radiation only exceeds resonance scattering of solar 584 and 304 Å radiation as the dominant O+ source during the month of December. 相似文献
7.
A rocket C.W. radio propagation experiment has been used to measure electron density profiles and the results compared with values calculated from ionograms. In general the agreement is satisfactory but significant discrepancies in the rocket measurements, during the up-leg portions of several rocket flights above 110 km were observed and possible causes are discussed. In one flight the effect of a travelling ionospheric disturbance on the N(h) profile was recorded. Sporadic E strata with thicknesses of 0.6–0.8 km were recorded in these flights. 相似文献
8.
This paper presents an empirical model for space-time distribution of the basic parameters of the general circulation of the atmosphere at ionospheric levels (E-and F-regions). The model is based on the results of a physico-statistical analysis of experimental data on the measurement of horizontal ionospheric drifts by close spaced receivers, carried out by the world network of stations in 1958–1970. This model allows an evaluation of the motion parameters at a given latitude, local time, season and the level of solar activity to be made. The limitations and shortcomings of the model are discussed, the results are compared with theoretical and semi-empirical schemes of the atmospheric general circulation, as well as with data of both rocket measurements of wind and drift measurements of plasma by the method of incoherent scatter of radio waves. The physics of the results obtained are stressed. The characteristics of the model are tested and defined using the materials af the coordinated program of drift measurements in the E-region from 8 stations of the northern hemisphere in 1971–1974. The characteristics of motions at higher latitudes and the longitudinal effect are discussed. 相似文献
9.
D.N. Anderson 《Planetary and Space Science》1976,24(1):69-77
Under magnetically quiet conditions, ionospheric plasma in the midlatitude F-region corotates with the Earth and relative east-west drifts are small compared to the corotation velocity. During magnetic storms, however, the enhanced dawn-to-dusk magnetospheric convection electric field often penetrates into the midlatitude region, where it maps into the ionosphere as a poleward electric field in the 18:00 LT sector, producing a strong westward plasma drift. To evaluate the ionospheric response to this east-west drift, the time-dependent O+ continuity equation is solved numerically, including the effects of production by photoionization, loss by charge exchange and transport by diffusion, neutral wind and drift. In this investigation only the neutral wind's meridional component and east-west drift are included. It is found that an enhanced equatorward wind coupled with westward drift produces an enhancement in the peak electron density (NMAX(F2)) and in the electron content (up to 1000 km) in the afternoon sector and a subsequent greater-than-normal decay in ionization after 18:00 LT. These results agree in general with midlatitude F-region ionospheric storm observations of NMAX(F2) and electron content which show an afternoon enhancement over quiet-time values followed by an abrupt transition to lower-than-normal values. Westward drift appears to be a sufficient mechanism in bringing about this sharp transition. 相似文献
10.
The discrepancy between the overhead E-region current and the magnetic D-component is studied using data obtained by the Chatanika incoherent scatter radar (L = 5.6). The F-region horizontal current is estimated to be too small to cause the observed D-deflection. Also, the assumption that the magnetic effects of the Pedersen and field-aligned currents cancel each other on the ground is shown to be inadequate to solve the problem. The significance of the inclination angle in the data analysis and the importance of the field-aligned current sheets are discussed. 相似文献
11.
A sounding rocket was launched in March 1982 from Thumba, India, shortly after sunrise. The measurements included the concentration of nitric oxide and ozone, the total ion density and the Lyman-α flux. Hence most parameters important for the formation of the D-region during daytime are available with the exception of solar radiation other than Lyman-α which only becomes important above 95 km. The mutual agreement is satisfactory which adds weight to the measurements. 相似文献
12.
Detailed studies of the daytime E-region critical frequency at Aberystwyth (geomagnetic latitude +56°) show clear evidence for changes associated with both the axially-symmetric (Dst) and asymmetric (DS) components of the disturbance magnetic field. Comparison of the sensitivity of the E-region peak density to these two influences shows that the changes cannot entirely (if at all) be ascribed to the influence of electric currents in the region. It is suggested that a major role is played by dynamical influences associated with the neutral air “storm circulation” which distributes the energy fed into the auroral region to lower latitudes. 相似文献
13.
R.A. Heelis P.C. Kendall R.J. Moffett D.W. Windle H. Rishbeth 《Planetary and Space Science》1974,22(5):743-756
Electric currents, generated by thermospheric winds, flow along the geomagnetic field lines linking the E-and F-regions. Their effects on the electric field distribution are investigated by solving the electrical and dynamical equations. The input data include appropriate models of the F-region tidal winds, the thermospheric pressure distribution and the E-and F-layer concentrations. At the magnetic equator, the calculated neutral air wind at 240 km height has a prevailling eastward component of 55 m sec-1 and the west-east and vertical ion drifts agree in their general form with incoherent scatter data from Jicamarca 相似文献
14.
Electron temperature measurements made with Langmuir probes at E-region heights together with deviative absorption data show that the electrons are not in thermal equilibrium with the neutrals. Moreover, for very quiet days (Ap ? 7, Kp ? 1+ throughout the whole day) and hours close to noon the quotients between the electron and neutral gas temperature profiles have a similar behaviour. In this paper Te profiles measured in situ with Langmuir probes and Tn, profiles given by neutral atmosphere models, both in the specified ionospheric conditions, are used to compute profiles. Each of the profiles thus obtained is fitted by a Lorentzian curve and the variation with F10.7 of its parameters is also fitted by simple mathematical expressions. 相似文献
15.
Knowledge of the structure of the polar ionosphere during exceptionally quiet periods is basic for studying complicated ionospheric behaviors during disturbances. On the basis of data from an airborne ionosonde as well as a meridian chain of ground-basedionosondes, the circumpolar structure of the E,-and F-regions is elucidated. There are two circumpolar zones of E-region ionization with differing characteristics. The first is an auroral E,-layer and/or retarded type sporadic E-band that has previously (Whalen et al., 1971) been found to be identical with the continuous aurora. The second is a zone of non-retarded type spora die E located poleward of the former band. In general, discrete auroras are co-located with the latter. The main trough, a prominent feature of the night sector F-region, is most pronounced in the early morning. The main trough is bounded on the poleward side by a well defined ‘wall’ of F-region ionization. The night sector poleward trough wall is located approximately three degrees of latitude equatorward of the auroral oval. A ‘plateau’ of F-region ionization extends from the poleward trough wall to the auroral oval. 相似文献
16.
The absolute cross-sections for the excitation of the 989 Å, 1027 Å, 7990 Å, 8446 Å, 1.1287 μm and 1.3164 μm multiplets of atomic oxygen by electron impact dissociation of O2 are reported. The radiative branching ratios for these transitions are calculated from these results and compared with the NBS compilation of Wiese et al. (1966) and the recent theoretical calculations of Pradhan and Saraph (1977). The cascade models of O+ radiative recombination and of electron-impact excitation of the OI(3S) state in the terrestrial airglow are discussed in the light of the laboratory measurements, and the effects of the resonant absorption of components of the λ 989 Å and λ. 1027 Å multiplets by the Birge-Hopfield band system of N2 are investigated. This process is shown to depend sensitively on the N2 vibrational temperature and to cause characteristic changes in the OI e.u.v. emission spectrum in auroras and in the sunlit F-region at high exospheric temperatures. It is also suggested that the λ 1027 Å radiation observed in auroral spectra is actually due to molecular nitrogen band emission that has been enhanced by entrapment effects and not to the excitation of the 2p 3P-3d 3D0 transition of atomic oxygen as believed previously. 相似文献
17.
In this paper we present the results of a study of the thermal balance of the lower F-region at mid- to low latitudes. By using a mathematical model with input data based on in situ measurements along AE-C orbits 457, 666 and 677 (26 January, 1974, 14 February, 1974 and 15 February, 1974, respectively) we demonstrate that electron heat conduction along the magnetic field lines has to be included in the model if good agreement between the calculated and observed electron temperatures is to be achieved. This gives support to the suggestion made by Hoegy and Brace (1978), that the discrepancy in the shape of the electron heating and electron cooling rate distributions reported by Brace et al. (1976) resulted mainly from neglecting heat conduction in the electron gas. In addition, our results indicate that the currently used plasma heating and plasma cooling rates and the photoelectron heating rates calculated by Brace et al. (1976) for the orbits used in this study are consistent with the AE-C in situ measurements. 相似文献
18.
Ionospheric drifts using total reflections from the E-region have been compared with neutral winds measured by meteor radar. Close agreement was found when both measurements were made in a common volume of atmosphere. Even with a separation of 700 km between the measuring regions the results were very similar. It is concluded that the drift technique does measure the movement of the neutral atmosphere in the altitude range 95–120 km. The agreement between measurements from widely separated regions indicates the horizontal scale of the wind structure is at least 700 km. 相似文献
19.
It is shown that it is possible to define an empirical law between ionospheric slab thickness and mean gradient of the electron temperature in the F-region. This law is obtained by using data of the incoherent scatter of Saint-Santin (France) and can be used under certain conditions in connexion with ionograms to find the electronic temperature and density profiles above the ionization maximum level. 相似文献
20.
In the mid-latitude E-region, the wind-shear mechanism produces thin ionized layers at levels where the vertical ion velocity is zero. We show that such layers conduct electric current only towards the magnetic equator, and not in the zonal direction. We surmise that this property may influence the electric field distribution in the nocturnal ionosphere, and possibly also the coupling between ion drifts and neutral air winds in the F-region. Detailed case studies of nocturnal layers located near the peak of ion Pedersen conductivity (around 130km) are needed to test this idea. 相似文献