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1.
Infrared observations of the Io eclipse of 12 April 1980 in five broad bands from 3 to 30 μm define the thermal emission spectrum both during and after eclipse. A substantial fraction of the emitted radiation during eclipse arises from hot spots; the equivalent global average heat flow is 1.5 ± 0.3 W m?2, corresponding to an internal source of (6 ± 1) × 1013 W. The hot spot spectra can be matched by components with color temperatures of 200–600°K covering 1–2% of the surface. Comparison with observations over the past 8 years suggests that, while the flux at the hottest temperatures may be highly variable, there is no evidence for major changes in the total heat flow, which is emitted primarily in the spectral region 10–20 μm. The heating curves of the surface were observed at 10 and 20 μm; when corrected for the hot spot contribution they indicate a typical global thermal inertia for Io of (0.2 ± 0.1) × 10?3cal cm?2sec?12K?1, similar to that of the other Galilean satellites.  相似文献   

2.
The beam cyclotron instability and electron acoustic instability, driven by cross-tail current and inhomogeneity in density and magnetic field, are found to be unstable in the earth's magnetic tail region. The anomalous resistivities due to these instabilities are found to be of the order of (10?1?10?3e?1e being the electron gyro frequency). It is also suggested that the non-linear saturation of the beam cyclotron instability may lead to conditions favourable for exciting ion acoustic instability.  相似文献   

3.
The quenching rate kN2 of O(1D) by N2 and the specific recombination rate α1D of O2+ leading to O(1D) are re-examined in light of available laboratory and satellite data. Use of recent experimental values for the O(1D) transition probabilities in a re-analysis of AE-C satellite 6300 Å airglow data results in a value for kN2 of 2.3 × 10?11 cm3s?1 at thermospheric temperatures, in excellent agreement with the laboratory measurements. This implies a value of JO2 = 1.5 × 10?6s?1 for the O2 photodissociation rate in the Schumann-Runge continuum. The specific recombination coefficient α1D = 2.1 × 10?7cm3s?1 is also in agreement with the laboratory value. Implications for the suggested N(2D) + O2 → O(1D) + NO reaction are discussed.  相似文献   

4.
Results are given of the calculations of the group delay time propagating τ(ω, φ0) of hydromagnetic whistlers, using outer ionospheric models closely resembling actual conditions. The τ(ω, φ0) dependencies were compared with the experimental data of τexp(ω, φ0) obtained from sonagrams. The sonagrams were recorded in the frequency range ? ? (0.5?2.5) Hz at observation points located at geomagnetic latitudes φ0 = (53?66)° and in the vicinity of the geomagnetic poles. This investigation has led us to new and important conclusions.The wave packets (W.P.) forming hydromagnetic whistlers (H.W.) are mainly generated in the plasma regions at L = 3.5?4.0. This is not consistent with ideas already expressed in the literature that their generation region is L ? 3?10. The overwhelming majority of the τexp values differ considerably from the times at which wave packets would, in theory, propagate along the magnetic field lines corresponding to those of the geomagnetic latitudes φ0 of the observation points. The second important fact is that the W.P. frequency ω is less than ΩH everywhere along its propagation trajectory, including the apogee of the magnetic force line (ΩH is the proton gyrofrequency). Proton flux spectra E ? (30?120) keV, responsible for H.W. generation, were determined. Comparison of the Explorer-45 and OGO-3 measurements published in the literature, with our data, showed that the proton flux density energy responsible for the H.W. excitation Np(MV622) ? (5 × 10?3?10?1) Ha2 where Ha is the magnetic field force in the generation region of these W.P. The electron concentration is Na ? (102?103) cm?3. The values given in the literature are Na ? (10?10?103) cm?3. The e data considered also leads to the conclusion that the generating mechanism of the W.P. studied probably always co-exists with the mechanism of their amplification.  相似文献   

5.
The orbit of the satellite 1967-104B has been analysed as it passed through 29:2 resonance with the Earth's gravitational field between January 1977 and September 1978. From the changes in inclination and eccentricity the following lumped 29th-order geopotential harmonic coefficients were obtained: 109C?290.2 = 4.1 ± 0.8, 109S?290.2 = 10.3 ± 2.4, 109C?291.1 = ? 160 ± 19, 109S?291.1 = 79 ± 10, 109C?29?1.3 = 38 ± 14, 109S?29?1.3 = 19 ± 5. These values have been compared with existing comprehensive geopotential models: the best agreement is with the model of Rapp (1981).  相似文献   

6.
The calculated radiative lifetime of the metastable ion is 6.4 × 10?3s. Used in conjunction with the results of measurements by Erdman, Espy and Zipf this sets 1.3 × 10?18 cm2 as the upper limit to the cross section for the formation of N+(5S) in e - N2 collisions at 100eV which leaves the possibility that the process is responsible for the λ2145A? feature in auroras only just open. The cross section for the formation of N+(5S) in e — N collisions is large. However for this process to lead to the observed intensity of λ2145A? relative to λ3914A? the N:N2 abundance ratio would have to be as high as 1.6 × 10?2.  相似文献   

7.
Measurements of N2+ and supporting data made on the Atmosphere Explorer-C satellite in the ionosphere are used to study the charge exchange process
O+(2D)+N2kN+2+O
The equality k = (5 ± 1.7) × 10?10cm3s?1. This value lies close to the lower limit of experimental uncertainty of the rate coefficient determined in the laboratory. We have also investigated atomic oxygen quenching of O+(2D) and find that the rate coefficient is 2 × 10?11 cm3s?1 to within approximately a factor of two.  相似文献   

8.
Previous studies based on radio scintillation measurements of the atmosphere of Venus have identified two regions of small-scale temperature fluctuations located in the vicinity of 45 and 60 km. A global study of the fluctuations near 60 km, which are consistent with wind-shear-generated turbulence, was conducted using the Pioneer Venus measurements. The structure constants of refractive index fluctuations cn2 and temperature fluctuations cT2 increase poleward, peak near 70° latitude, and decrease over the pole; cn2 varies from 2 × 10?15 to 1.5 × 10?14m23 and cT2 from 4 × 10?3 to 7 × 10?2°K2m?23. These results indicate greater turbulent activity at the higher latitudes. In the region near 45 km the refractive index fluctuations and the corresponding temperature fluctuations are substantially lower. Based on the analysis of one representative occultation measurement, cn2 = 2 × 10?16m?23and cT2 = 7.3 × 10?4°K2m?23 in the 45-km region. The fluctuations in this region also appear to be consistent with wind-shear-generated turbulence. The turbulence level is considerably weaker than that at 60 km; the energy dissipation rate ε is 4.9 × 10?5m2sec?3 and the small-scale eddy diffusion coefficient K is 2 × 103 cm2 sec?1.  相似文献   

9.
The photodissociation of water vapour in the mesosphere depends on the absorption of solar radiation in the region (175–200 nm) of the O2 Schumann-Runge band system and also at H-Lyman alpha. The photodissociation products are OH + H, OH + H, O + 2H and H2 + O at Lyman alpha; the percentages for these four channels are 70, 8, 12 and 10%, respectively, but OH + H is the only channel between 175 and 200 nm. Such proportions lead to a production of H atoms corresponding to practically the total photodissociation of H2O, while the production of H2 molecules is only 10% of the H2O photodissociation by Lyman alpha.The photodissociation frequency (s?1) at Lyman alpha can be expressed by a simple formula
JLyαH2O=4.5 ×10?61+0.2F10.7?65100exp[?4.4 ×10?19 N0.917]
where F10.7 cm is the solar radioflux at 10.7 cm and N the total number of O2 molecules (cm?2), and when the following conventional value is accepted for the Lyman alpha solar irradiance at the top of the Earth's atmosphere (Δλ = 3.5 A?) qLyα,∞ = 3 × 1011 photons cm?2 s1?.The photodissociation frequency for the Schumann-Runge band region is also given for mesospheric conditions by a simple formula
JSRB(H2O) = JSRB,∞(H2O) exp [?10?7N0.35]
where JSRB,∞(H2O) = 1.2 × 10?6 and 1.4 × 10?6 s?1 for quiet and active sun conditions, respectively.The precision of both formulae is good, with an uncertainty less than 10%, but their accuracy depends on the accuracy of observational and experimental parameters such as the absolute solar irradiances, the variable transmittance of O2 and the H2O effective absorption cross sections. The various uncertainties are discussed. As an example, the absolute values deduced from the above formulae could be decreased by about 25-20% if the possible minimum values of the solar irradiances were used.  相似文献   

10.
The space erosion of stony meteorites has been determined to be 650μm 106y?1, while that of iron meteorites has been determined to be 22 μm 106y?1. The erosion rates are based on flux and size distributions of small particles in the solar system, meteoroid orbitals and the relation, determined by laboratory experiments, between excavated volume due to a collision and the size and velocity of the impacting small particle. Neither multiple collision or space erosion can explain the difference in cosmic ray exposure ages based on 40K and those based on 36Cl, 39Ar and10Be. It is concluded that there is a long term cosmic ray variation.  相似文献   

11.
The paper gives the results of detailed studies of the frequency spectra Ss(?) of the chain of the wave packets Fs(t) of geomagnetic pulsations PC-1 recorded at the Novolazarevskaya station. The bulk of the energy of Fs(t) is concentrated in the vicinity of the central frequencies ?s0 of spectra—the carrier frequencies of the signals. The velocity V0 ≌ 6.103km s?1 of the flux of protons generating these signals correspond to them. The spectra of the signals have oscillations—“satellites” irregularly distributed in frequency. These satellites, as the authors believe, testify to the presence of the individual groups of protons of low concentration whose velocities vary within 103–104 km s?1.Their energy is only of the order of 10?2–10?3 of the energy of the main proton flux. Clearly pronounced maxima on double and triple frequencies ? = 2?s0and 3?s0 are detected. They show that the generation of pulsations PC-1 is accompanied by the generation on the overtones of wave packets called in this paper “two-fold” and “three-fold” pulsations PC-1. Intensive symmetrical satellites of a modulation character have been discovered on frequencies ?±sK. Frequency differences Δ?sK± = ¦?s0 ? ?sK±¦ = (0.011,0.022 and 0.035) Hz correspond to them. The authors believe that the values of Δ?±sK are resonance frequencies of the magnetospheric cavity in which geomagnetic pulsations PC-1 are generated. It is established that the values of Δ?±sK coincide closely with the carrier frequencies of geomagnetic pulsations PC-3 and PC-4 generated in the magnetosphere. This leads to the conclusion that the resonance oscillations of the magnetospheric cavity are their source. Thus, the generation of geomagnetic pulsations of different types and resonance oscillations in the magnetosphere are integrated into a unified process. The importance of the results obtained and the necessity to check further their trustworthiness and universality, using experimental data gathered in different conditions, is stressed.  相似文献   

12.
The influence of aerodynamic drag and the geopotential on the motion of the satellite 1964-52B is considered. A model of the atmosphere is adopted that allows for oblateness, and in which the density behaviour approximates to the observed diurnal variation. A differential equation governing the variation of the orbital inclination combining the effects of air drag with those of the Earth's gravitational field is given.The 310 observed values of inclination are modified by the removal of perturbations due to luni-solar attraction, solid Earth and ocean tides, solar radiation pressure, low-order long-periodic tesseral harmonic perturbations and changes due to precession. The method of removal of these effects is given in some detail.The variations in inclination due to drag are analysed to give four values of the average atmospheric rotation rate at heights of 296–476 km at latitude 0–54°. These values are as expected from previous analyses.The analysis of the change in inclination due to solar radiation pressure shows that this rapidly tumbling cylindrical satellite may be considered as equivalent to a spherical satellite of a given area-to-mass ratio.Analysis of the inclination near 15:1 resonance with the geopotential yields values of lumped geopotential harmonics of order 15 and 30, namely, 109C?0.115 = ?31.2 ± 2.3 109S?0.115 = ?4.4 ± 3.2 109C?0.230 = 39.0 ± 10.7 109S?0.230 = 51.8 ± 10.0  相似文献   

13.
The cross-section for dissociative photoionization of hydrogen by 584 Å radiation has been measured, yielding a value of 5 × 10?20 cm2. The process can be explained as a transition from the X1 Σg+ ground state to a continuum level of the X2 Σg+ ionized state of H2 The branching ratio for proton (H+) vs molecular ion (H2+) production at this energy is 8 × 10?3. This process is quite likely an important source of protons in the Jovian ionosphere near altitudes where peak ionization rates are found.  相似文献   

14.
In the forward part of the magnetosphere the distant tail current system approximates a magnetic quadrupole composed of two distorted adjacent solenoids. The current in the neutral sheet at this distance is accurately approximated as an infinitesimally thin current sheet. We have calculated the magnetic field near the Earth by integrating over the entire tail current system assuming the magnetotail is a cylinder of constant radius and that the tail current decreases with distance into the tail as |x|?13. The field is then represented by a scalar potential expanded into spherical harmonics which may be conveniently added to the spherical harmonic expansion of the scalar potential representing the magnetopause current system.  相似文献   

15.
The influence of aerodynamic drag and the geopotential on the motion of the satellite 1964-52B is considered. A model of the atmosphere is adopted that allows for oblateness, and in which the density behaviour approximates to the observed diurnal variation. A differential equation governing the variation of the eccentricity, e, combining the effects of air drag with those of the Earth's gravitational field is given. This is solved numerically using as initial conditions 310 computed orbits of 1964-52B.The observed values of eccentricity are modified by the removal of perturbations due to luni-solar attraction, solid Earth and ocean tides, solar radiation pressure and low-order long-periodic tesseral harmonic perturbations. The method of removal of these effects is given in some detail. The behaviour of the orbital eccentricity predicted by the numerical solution is compared with the modified observed eccentricity to obtain values of atmospheric parameters at heights between 310 and 430 km. The daytime maximum of air density is found to be at 14.5 hours local time. Analysis of the eccentricity near 15th order resonance with the geopotential yielded values of four lumped geopotential harmonics of order 15, namely: 109C1,015 = ?78.8 ± 7.0, 109S1,015 = ?69.4 ± 5.3, 109C?1,215 = ?41.6 ± 3.5109S?1,215 = ?26.1 ± 8.9, at inclination 98.68°.  相似文献   

16.
An approximate form of the Boltzmann equation has been used to obtain local ionization rates due to the absorption of galactic cosmic rays in the Jovian atmosphere. It is shown that the muon flux component of the cosmic ray-induced cascade may be especially importannt in ionizing the atmosphere at levels where the total number density exceeds 1019 cm?3 (well below the ionospheric layers produced by solar euv). A model containing both positive and negative ion reactions has been employed to compute equilibrium electron and ion number densities. Peak electron number densities on the order of 103 cm?3 may be expected even at relatively low magnetic latitudes. The dominant positive ions are NH4+ and CnHm+ cluster ions, with n ? 2; it is suggested that the absorption of galactic cosmic ray energy at such relatively high pressures in the Jovian atmosphere (M ? 1018to 1020cm?3) and the subsequent chemical reactions may be instrumental in the local formation of complex hydrocarbons.  相似文献   

17.
An attempt to observe radar echoes from the comet Kohoutek was made at a radio frequency of 7840 MHz (λ ~- 3.8 cm) on 12 January 1974 using the Haystack Observatory radar in Massachusetts. A search for an echo over a range of band-widths covering 2Hz to 66kHz yielded no positive result. The upper limit on the radar cross section is therefore approximately 104B12km2, where B is the (unknown) bandwidth of the echo in Hertz. For B ? 100 Hz, it follows that (i) the nucleus, if a perfect spherical reflector, must be less than 250 km in diameter, and (ii) the density of any millimeter-sized particles must be less than 1m?3 for a coma of diameter 104km.  相似文献   

18.
An astrophysical electron acceleration process is described which involves turbulent plasma effects: the acceleration mechanism will operate in ‘collision free’ magnetoactive astrophysical plasmas when ion-acoustic turbulence is generated by an electric field which acts parallel to the ambient magnetic lines of force. The role of ‘anomalous’ (ion-sound) resistivity is crucial in maintaining the parallel electric field. It is shown that, in spite of the turbulence, a small fraction of the electron population can accelerate freely, i.e. runaway, in the high parallel electric potential. The number density n(B) of the runaway electron component is of order n(B)?n2(csU?)2, where n = background electron number density, cs = ion-sound speed and U? = relative drift velocity between the electron and ion populations. The runaway mechanism and the number density n(B) do not depend critically on the details of the non-linear saturation of the ion-sound instability.  相似文献   

19.
We have measured the linewidths of the NI multiplets [2p2 3p4D0?2p23s4P, λ8691 A?; 2p2 3p4P0 ?2p23s4P, λ8212 A?; 2p2 3s4P?2p34S0, λ1200 A?] produced in the dissociative excitation of N2 by energy electrons. The infrared transitions excite the N(4P) resonance state by cascade and they account for > 50% of the total N(4P) cross section at 100 eV. Both the i.r. and v.u.v. lines are found to be highly Doppler broadened ( ~ 25 times the thermal Doppler line width). These results indicate that dissociative excitation of N2 produces N (4P) atoms with sufficient kinetic energy so that the λ1200 A? resonance radiation [2p2 3s4P ?2p34S0] emitted by these excited atoms would be optically thin in the Earth's upper atmosphere. We also found that the line strength ratios for the resolved components of the λ1200 A? triplet excited by dissociative excitation differ from those predicted by the multiplicities of the states involved and used in current entrapment models; the intensity ratios also vary with the energy of the incident electron. These developments introduce new complications into the analysis of the terrestrial ultraviolet dayglow.  相似文献   

20.
A mechanism has been proposed for uv-accelerated desorption from Fe2+ sites on mineral surfaces that satisfies kinetic constraints determined in the laboratory by Huguenin. The process is an integral step of the photochemical weathering mechanism for producing dust on Mars, and it now appears that it may play primary roles in stabilizing CO2 against dissociation by sunlight and in controlling the oxidation state of the atmosphere. We propose that adsorption occurs at octahedrally coordinated Fe2+ surface sites to form seven-coordinate transition-state complexes. These complexes acquire 16–18 kcal mole?1 of ligand field stabilization energy. During illumination (λ ≤ 0.35 μm), electrons are photoemitted from the surfaced Fe2+, temporarily oxidizing them to Fe3+. Fe3+ has no ligand field stabilization energy, and the complexes lose 16–18 kcal mole?1 of stabilization energy. This is a large fraction of the 19- to 28-kcal mole?1 activation energy for dissociating the complexes, and desorption should proceed spontaneously. The gases that were observed to undergo adsorption-photodesorption include O2, CO2, CO, H2O, N2, and Ar. Photodesorption can drive several catalytic reactions, one of which is the oxidation of CO to CO2. The rate of this reaction should be limited by the supply of CO and O2 to the surface to ~2 × 1012 cm?2 sec?1 (column photodissociation rate of CO2). By including this surface reaction in models of Martian atmospheric CO2 chemistry, CO2 can be stabilized against photodissociation with eddy diffusion coefficients of only 3 × 105?1 × 107 cm2 sec?1 below 40 km, raising to ~ 109 cm2 sec?1 at 140 km. Odd hydrogen is not needed to catalyze the oxidation of CO below 40 km, and odd hydrogen mixing ratios need only to be fH ? 10?10 to depress ozone concentrations below the observed upper limit in equatorial regions. Another catalytic reaction that should be driven by photodesorption on Mars is 20H?(ads)H2O + 12O2(g) + 2e?crystal. This is an important source of atmospheric O2, amounting to 7 × 1013?2 × 1017 O2 molecules cm?2 yr?1, and it could have a significant effect on atmospheric oxidation state.  相似文献   

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