On the C/H and D/H ratios in the atmospheres of Jupiter and Saturn     

T. Encrenaz  M. Combes 《Icarus》1982,52(1):54-61

Using a method defined in a previous paper [M. Combes and T. Encrenaz, Icarus39 1–27 (1979)], we reestimated the C/H ratio in the atmospheres of Jupiter and Saturn by the measurements of the weak visible CH₄ bands, the CH₄ 3ν₃ band, and the (3-0) and (4-0) quadrupole bands of H₂. In the case of Jupiter we conclude that the C/H ratio is enriched by a factor ranging from 1.7 to 3.6 relative to the solar value. In the case of Saturn, our derived C/H value ranges from 1.2 to 3.2 times the solar value. The Jovian D/H ratio derived from this study is 1.2 × 10^?5 < D/H < 3.1 × 10^?5. The value derived for the D/H ratio on Saturn is not precise enough to be conclusive.  相似文献   

Study of the structure and kinematics of the NGC 7465/64/63 triplet galaxies     

O. A. Merkulova  G. M. Karataeva  V. A. Yakovleva  A. N. Burenkov 《Astronomy Letters》2012,38(5):290-304

We analyze new observational data obtained at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences with the multimode SCORPIO instrument and the Multi-Pupil Fiber Spectrograph for the group of galaxies NGC 7465/64/63. For one of the group members (NGC 7465), the presence of a polar ring has been suspected. We have constructed the large-scale brightness distributions, the ionized-gas velocity and velocity dispersion fields for all three galaxies as well as the line-of-sight velocity curves based on emission and absorption lines and the stellar velocity field in the central region for NGC 7465. As a result of our analysis of the data obtained, we have discovered an inner stellar disk (r ?? 0.5 kpc) and a warped gaseous disk in NGC 7465, in addition to the main stellar disk. Based on a joint study of our photometric and spectroscopic data, we have established that NGC 7464 is an irregular IrrI-type galaxy whose structural and kinematic peculiarities most likely resulted from its gravitational interaction with NGC 7465. The velocity field of the ionized gas in NGC 7463 turns out to be typical of barred spiral galaxies, and the warp of the outer parts of its disk could arise from a close encounter with one of the galaxies of the environment.  相似文献   

Changes in the frequency distribution of f₀E_s and f_bE_s over two solar cycles     

W.J. Baggaley 《Planetary and Space Science》1985,33(4):457-459

The dependence of the occurrence probabilities of ionosonde sporadic-E parameters f₀E_s and f_bE_s on probing frequency is analyzed for wintertime for day and night for two Southern Hemisphere stations. The ionosonde data indicate that significant changes have taken place over the period 1958–1983 suggesting that E_s has become increasingly dense and also less patchy.  相似文献   

Electrical coupling of the E- and F-regions and its effect on F-region drifts and winds     

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   

The semiannual variation in the magnetic activity indices A_a and A_p     

C.A. Green 《Planetary and Space Science》1984,32(3):297-305

The technique of Complex Demodulation is used to examine the long-term modulation of the semiannual variation in planetary magnetic activity as characterised by the A_a index for 1868–1980 and the A_p index for 1932–1980. From the phase results, strong support is found for an “equinoctial” mechanism for the semiannual variation. The amplitude shows a quasi 11 -year modulation for most of the period of analysis and a pronounced increase over the years 1938–1966 approximately. Comparison of the long-term modulation of the semiannual variation in activity, with that of the occurrence of stormy days suggests that the semiannual modulation is energy dependent, being more effective with increasing energy.  相似文献   

Resolving Differences in Absolute Irradiance Measurements Between the SOHO/CELIAS/SEM and the SDO/EVE     

S. R. Wieman  L. V. Didkovsky  D. L. Judge 《Solar physics》2014,289(8):2907-2925

The Solar EUV Monitor (SEM) onboard SOHO has measured absolute extreme ultraviolet (EUV) and soft X-ray solar irradiance nearly continuously since January 1996. The EUV Variability Experiment (EVE) on SDO, in operation since April of 2010, measures solar irradiance in a wide spectral range that encompasses the band passes (26?–?34 nm and 0.1?–?50 nm) measured by SOHO/SEM. However, throughout the mission overlap, irradiance values from these two instruments have differed by more than the combined stated uncertainties of the measurements. In an effort to identify the sources of these differences and eliminate them, we investigate in this work the effect of reprocessing the SEM data using a more accurate SEM response function (obtained from synchrotron measurements with a SEM sounding-rocket clone instrument taken after SOHO was already in orbit) and time-dependent, measured solar spectral distributions – i.e., solar reference spectra that were unavailable prior to the launch of the SDO. We find that recalculating the SEM data with these improved parameters reduces mean differences with the EVE measurements from about 20 % to less than 5 % in the 26?–?34 nm band, and from about 35 % to about 15 % for irradiances in the 0.1?–?7 nm band extracted from the SEM 0.1?–?50 nm channel.  相似文献   

Calculations on the rates, mechanisms, and interstellar importance of the reactions between C and NH₂ and between N and CH₂     

E. Herbst  R. Terzieva  D. Talbi 《Monthly notices of the Royal Astronomical Society》2000,311(4):869-876

The attempt to understand the temperature dependence of the HNC/HCN abundance ratio in interstellar clouds has been long standing and indecisive. In this paper we report quantum chemical and dynamical studies of two neutral–neutral reactions thought to be important in the formation of HNC and HCN, respectively – C+NH₂→HNC+H, and N+CH₂→HCN+H. We find that although these reactions do lead initially to the products suggested by astronomers, there is so much excess energy available in both reactions that the HCN and HNC products are able to undergo efficient isomerization reactions after production. The isomerization leads to near equal production rates of the two isomers, with HNC slightly favoured if there is sufficient rotational excitation. This result has been incorporated into our latest chemical model network of dense interstellar clouds.  相似文献   

Anomalous mixing of the w²P^o_3/2 and x⁶P^o_3/2 levels in Fe ii     

M. P. Donnelly  & A. Hibbert 《Monthly notices of the Royal Astronomical Society》1998,301(3):809-812

The neighbouring lines a ⁶D_5/2– x ⁶P^o_3/2 (1272.617 Å) and a ⁶D_5/2– w ²P^o_3/2 (1272.657 Å) have been observed in the UV spectrum of χ Lupi to be of comparable intensity. The latter, Δ S  = 2, transition would be expected to be very weak. The two upper states should display negligible mixing. We give a detailed, quantitative discussion of how the two upper states are in fact strongly mixed through their mixing with 3d⁶(³D)4p ⁴P^o_3/2, and hence we explain the relative strengths of the two UV lines.  相似文献   

Quantitative dependence of the polar cap electric field on the IMF B_z-component and solar wind velocity     

V.A. Sergeev  B.M. Kuznetsov 《Planetary and Space Science》1981,29(2):205-213

Ten years data set is used to separate the influence of IMF B_z-component and solar wind speed on the dawn-dusk component of magnetic variations in the summer polar cap. The reference level was chosen from most quiet periods of winter solstices (small polar cap and auroral zone conductivity) to exclude the inner source component. The linear regression analysis was then used to calculate the PC variation response to B_z under different ranges of solar wind speed. As a result, taking into account the value of polar cap conductivity and effects of induced currents, the response of dawn-dusk electric field component to B_z and V was obtained and the potential difference across the polar cap was estimated to be $\text{Δ?(}\text{kV}\text{) ≈ 6(}\text{V}\text{300}\text{)}{}^2\text{? 9B}{}_{\mathrm{z}}\text{(γ)}$ for B_z ? + 1γ. The results give a proof for simultaneous operation in the magnetosphere of two electric field generation mechanisms, related to the boundary layer processes and magnetic field reconnection. The above-mentioned functional form was shown to correlate effectively with AE index (R = 0.73).  相似文献   

Mass spectrometer measurements of the positive ion composition in the D- and E-regions of the ionosphere     

P. A. Zbinden  M. A. Hidalgo  P. Eberhahdt  J. Geiss 《Planetary and Space Science》1975,23(12):1621-1642

On 14 December 1971, during the maximum of the Geminid Meteor Shower, the positive ion composition was measured in the D- and E-regions above Sardinia. The payload was launched at 12:11 UT, and measurements were made between 68.5 and 152 km altitude. A magnetic sector type mass spectrometer with dual collector and a liquid helium cryopump was used. The instrument covered the mass range from 11 to 73 AMU and had a resolution at the 1 % level of M/ΔM = 60.In the E-region two distinct metal ion layers were observed, centred at 95 and 119 km, respectively. In the lower layer Fe⁺ and Mg⁺ were the most abundant metal ions, and in the upper layer Si⁺ was dominant. Si⁺ ions were conspicuously absent in the lower layer (Si⁺/Mg⁺ < 2 × 10⁻³). This particular behaviour of Si could be due to the inability of atomic oxygen to reduce SiO, whereas in the upper layer Si⁺ions might be formed directly by the charge rearrangement reaction SiO + O⁺ → Si⁺+ O₂. In addition, Na⁺, Al⁺, K⁺, Ca⁺, Ti⁺, Cr⁺, Ni⁺ and Co⁺ were also identified. The metal oxide ions AlO⁺ and SiO⁺ were detected, and probably also MgO⁺ and SiOH⁺. The concentrations of NO⁺ and O₂⁺ show a deep minimum at the maximum of the lower metal ion layer. A very high neutral metal density of 6 × 10⁷ cm⁻³ would be required to explain this feature as resulting from charge transfer reactions between the molecular and metal ions Such a high metal density is in contradiction to direct measurements and to cosmic dust influx rates. The isotopic ratios of Mg⁺, Si⁺, and of the major isotopes of Fe⁺ and Ni⁺ were measured, some of them with an accuracy of a few per cent (²⁵Mg⁺/²⁴Mg⁺ = 0.124 ± 0.006; ²⁶Mg⁺/²⁴Mg⁺ = 0.139 ± 0.008; ²⁹Si⁺/²⁸Si⁺ = 0.050 ± 0.004; ⁵⁴Fe⁺/⁵⁶Fe⁺ = 0.069 ± 0.005; ⁵⁷Fe⁺/⁵⁶Fe⁺ = 0.029 ± 0.004; ⁶⁰Ni⁺/⁵⁸Ni⁺ = 0.31 ± 0.12). The isotopic ratios agree within the experimental errors with the corresponding terrestrial ratios, thus giving evidence that these elements have the same isotopic composition in the Geminid meteors as in the Earth's crust, in chrondrites, and in lunar material.In the D-region the ions Na⁺H₂O, Na⁺(H₂O)₂, NaO⁺ and NaOH⁺ were tentatively identified. Below 95 km altitude the relative abundances of the ions 32⁺, 33⁺ and 34⁺ deviate from the values expected for molecular oxygen isotopes. Their abundances can not be explained by the presence of S-ions only, and we conclude that HO₂⁺ and H₂O₂⁺ are present.The ion density profiles of the major D-region constituents show some remarkable deviations from typical D-region conditions. These deviations are related to the winter anomaly in ionospheric absorption observed over Spain during the launch day, and our data represent the first ion composition measurements during such conditions. In particular, H⁺(H₂O)₂ is the major ion only up to 77 km, and at 80 km altitude the NO⁺ concentration exceeds the total water cluster ion density by almost two orders of magnitude. An increase of the mesospheric NO, O₃ and O concentrations as well as of the O/H₂O ratio could explain the observed ion profiles. The low NO⁺/O₂⁺ ratios of approximately unity measured in the E-region are in agreement with a strong downward transport of NO and/or O into the mesosphere during the launch day. A simple four-ion model was used to interpret our D-region data. The calculated neutral NO concentration increases from about 2 × 10⁷ cm⁻³ at 85 km to 5 × 10⁷ cm⁻³ at 80 km. In addition, evidence for an increased O₂⁺ production rate above 83 km was found, probably due to an enhanced O₃ concentration. We conclude that our data strongly support vertical transport of minor neutral consituents as cause of the winter anomaly.  相似文献   

The environmental dependence of u-, g-, r-, i-, and z-band luminosities for galaxies above and below the value of M_r^*     

Xin-Fa Deng  Jun Song  Yi-Qing Chen  Peng Jiang  Ying-Ping Ding 《Astronomy Letters》2012,38(4):213-221

Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), we have explored the difference of the environmental dependence of u-, g-, r-, i-, and z-band luminosities between galaxies above and below the value of M _r^*. It turns out that in the luminous volume-limited sample, all the five band luminosities strongly correlate with local environments. Because the u-band luminosity of galaxies still strongly depends on local environments in the faint volumelimited sample, we conclude that M _r^* is not an important characteristic parameter for the environmental dependence of the u-band luminosity. It is worth noting that for the u-band, the subsample at low density has a higher proportion of luminous galaxies and a lower proportion of faint galaxies than the one at high density, which is opposite to widely accepted conclusion: luminous galaxies exist preferentially in the densest regions of the universe, but faint galaxies are located preferentially in low density regions. Our results show that the environmental dependence of luminosity is not a single trend in different luminosity regions and for different bands.  相似文献   

The relationship between geology and geochemistry in the Undarum/Spumans/Balmer region of the Moon     

P. E. Clark  B. R. Hawke 《Earth, Moon, and Planets》1987,38(2):97-112

A detailed study of geochemical variation in the Undarum/Spumans/Balmer region identifies major rock components which form the region's regolith. The northern portion of the region contains numerous small mare deposits, which cluster in the Undarum and Spumans areas particularly. In the southern portion of the region lies the Balmer basin chemical anomaly, which correlates with extensive plains deposits. Regional maps of the orbital geochemical variables (Mg, Al, Fe, Ti, and Th) are examined individually, then correlated to one another and to the most recent geological map of the region. Results of the study indicate the presence of basalt components, which show considerable variation in character and which are correlated with both mare and plains features in a region otherwise dominated by ANT suite material. The northeastern area is the most characteristically anorthositic part of the region and mare plains deposits from this area have relatively anorthositic composition. A basalt intermediate in composition between mare basalt and Fra Mauro basalt is proposed as a probable component of the Balmer plains deposits. Southeastern Crisium basalts, and the parts of other mare deposits that are distributed along a structurally-related ring have a similar character. The major basalt deposits around the eastern part of Fecunditatis appear to have a different character. All deposits, particularly those in the northeastern area, appear to be mare basalt contiminated with ANT suite material from the surrounding highlands. In general, the surface geochemistry of the Undarum/Spumans/Balmer region is quite heterogeneous, showing a distinct north/south dichotomy.  相似文献   

Chaotic behavior and the origin of the $\text{3}\text{1}$ Kirkwood gap     

Jack Wisdom 《Icarus》1983,56(1):51-74

The sudden eccentricity increases discovered by J. Wisdom (Astron J.87, 577–593, 1982) are reproduced in numerical integrations of the planar-elliptic restricted three-body problem, verifying that this phenomenon is real. Maximum Lyapunov characteristic exponents for trajectories near the $\text{3}\text{1}$ commensurability are computed both with the mappings presented in Wisdom (1982) and by numerical integration of the planar-elliptic problem. In all cases the agreement is excellent, indicating that the mappings accurately reflect whether trajectories are chaotic or quasiperiodic. The mappings are used to trace out the chaotic zone near the $\text{3}\text{1}$ commensurability, both in the planar-elliptic problem and to a more limited extent in the three-dimensional elliptic problem. The outer boundary of the chaotic zone coincides with the boundary of the $\text{3}\text{1}$ Kirkwood gap in the actual distribution of asteroids within the errors of the asteroid orbital elements.  相似文献   

Disc evolution and the relationship between L_acc and L_* in T Tauri stars     

I. Tilling  C. J. Clarke  J. E. Pringle  C. A. Tout 《Monthly notices of the Royal Astronomical Society》2008,385(3):1530-1534

  相似文献   

A comparison of the spectral characteristics of the Wolf Sunspot Number (R_Z) and Group Sunspot Number (R_G)     

H. H. Faria  E. Echer  N. R. Rigozo  L. E. A. Vieira  D. J. R. Nordemann  A. Prestes 《Solar physics》2004,223(1):305-318

The objective of this paper is to compare the spectral features of the recently derived Group Sunspot Numbers (R _G) and the traditional Wolf Sunspot Numbers (R _Z) for the 1700–1995 period. In order to study the spectral features of both time series, two methods were used, including: (a) the multitaper analysis and (b) the wavelet analysis. Well-known features of the solar variability, such as the 98.6-yr (Gleissberg cycle), 10–11-yr (Schwabe cycle) and 5-yr (second solar harmonic) periodicities were identified with high confidence using the multitaper analysis. Also observed was a larger amount of power spread in high frequencies for R _Z than for R _G spectra. Furthermore, a multitaper analysis of two subsets, A (1700–1850) and B (1851–1995), has indicated that the main differences occurred in the first subset and seem to be due to uncertainties in the early observations. The wavelet transform, which allows observing the spectra evolution of both series, showed a strong and persistent 10–11-yr signal that remained during the whole period. The Meyer Wavelet Transform was applied to both R _Z and R _G. This study indicates that the main spectral characteristics of both series are similar and that their long-term variability has the same behavior.  相似文献   

On the identification of the C₆₀⁺ interstellar features     

G. A. Galazutdinov  J. Kreowski  F. A. Musaev  P. Ehrenfreund  B. H. Foing 《Monthly notices of the Royal Astronomical Society》2000,317(4):750-758

The identity of the carriers of the diffuse interstellar bands (DIBs) is one of the most fascinating puzzles of modern spectroscopy. Over the last few years the number of known DIBs has grown substantially. In this paper we discuss the two recently discovered near-infrared weak interstellar features which have already been proposed as fingerprints of the buckminsterfullerene We present and discuss measurements of the two related DIBs within a larger sample of reddened targets, observed with different spectrometers, telescopes and site conditions. We provide additional arguments in favour of the interstellar origin of the two bands. We find evidence around the 9577-Å DIB of far-wing structures, which may affect broad-band measurements. We estimate corrections and errors for telluric and stellar blends, and show that the cores of the two DIBs are well correlated with a ratio near unity within 20 per cent. Finally, we discuss their relation to the laboratory spectra of and the search for two expected weaker transitions.  相似文献   

P/GE-Wang joins P/Slaughter-Burnham and P/Boethin in the club of comets in 1/1 resonance with jupiter     

Daniel G. Benest 《Celestial Mechanics and Dynamical Astronomy》1989,47(4):361-374

Three comets are now known to be at or near the 1/1 resonance with Jupiter P/Slaughter-Burnham, P/Boethin and the newly discovered P/Ge-Wang. Their orbital evolutions are compared, using the elliptic three-dimensional restricted three-body model Sun-Jupiter-comet. Although details of the individual orbits differ, the three comets have very similar general dynamical behaviours, and stay during a long time at or near the 1/1 resonance, at least for several thousand years.  相似文献   

Some instabilities in the 3/1 and 2/1 resonances     

Tadashi Yokoyama  Massae Sato  Masayoshi Tsuchida 《Celestial Mechanics and Dynamical Astronomy》1987,41(1-4):99-105

In a very simple way, it is possible to show the existence of small regions of instability, inside the observed 3/1 and 2/1 Kirkwood Gap, by using the classical Laplace-Lagrange secular theory.  相似文献   

Possible collisions of P/Halley and P/Machholz 1 with Jupiter and the terrestrial planets     

Yu. V. Obrubov 《Earth, Moon, and Planets》1996,72(1-3):293-300

The perturbed motion of comet Halley and comet Mackholz 1 1986 VIII was investigated within a time interval of about 20 millennia. The minimal distance of 0.043 AU between P/Halley and Venus may occur on April 4, 4868 AD. The distance of 0.036 AU between P/Halley and Jupiter will take place on April 1, 6616 AD. The orbit of P/Machholz 1 crosses the orbits of Mercury and Venus eight times, that of the Earth six or eight times, and the orbit of Mars four times per a period of advance of the argument of perihelion. A distance of about 0.06 AU between P/Machholz 1 and the Earth may take place in August 2576 AD and 5751 AD and in February 4770 AD. The minimal comet-Earth distance of 0.035 AU occurs on September 14, 5971 AD. The closest encounter between P/Machholz 1 and Jupiter at the distance of 0.098 AU may be in May 4499 AD. These results may be considered as a forecast of possible collisions.  相似文献   

Possible collisions of P/Halley and P/Machholz 1 with Jupiter and the terrestrial planets     

Yu. V. Obrubov 《Earth, Moon, and Planets》1995,71(3):293-300

The perturbed motion of comet Halley and comet Mackholz 1 1986 VIII was investigated within a time interval of about 20 millennia. The minimal distance of 0.043 AU between P/Halley and Venus may occur on April 4, 4868 AD. The distance of 0.036 AU between P/Halley and Jupiter will take place on April 1, 6616 AD.The orbit of P/Machholz 1 crosses the orbits of Mercury and Venus eight times, that of the Earth six or eight times, and the orbit of Mars four times per a period of advance of the argument of perihelion. A distance of about 0.06 AU between P/Machholz 1 and the Earth may take place in August 2576 AD and 5751 AD and in February 4770 AD. The minimal comet-Earth distance of 0.035 AU occurs on September 14, 5971 AD. The closest encounter between P/Machholz 1 and Jupiter at the distance of 0.098 AU may be in May 4499 AD. These results may be considered as a forecast of possible collisions.  相似文献