The Mars opposition effect at 20°N. latitude and 20°W. longitude

Low phase angle observations in the Chryse-Acidalia region have been obtained the Viking Orbiter 1 spacecraft under clearer atmospheric conditions than reported earlier. A variety of surface features were recorded, e.g., crater streaks, dark and bright patches. Several findings for this scene include: an abrupt brightness increase (10%) was found at phase angles less than 3°, an effect dependent on surface albedo and possibly particle distribution; a slight weakening of reflectance surge with decreasing wavelengths; a larger opposition effect for features of high albedo was recorded; and a greater reddening with increase phase angle took place for low albedo regions. Both reflectance and contrast values are provided at three wavelengths as a function of phase angle from 0.15 to 20°.     

Seasonal variations of diffuse solar radiation at Ilorin (8°32′N,4°46′E), Nigeria

Hourly diffuse solar irradiance (H_d) and the corresponding global irradiance (H) falling on a horizontal surface at Ilorin (8°32N,4°46E), Nigeria has been measured for a period of fifteen months commencing from February, 1993. As expected, each monthly mean diurnal variation of H_d exhibits a mid-day maximum, while that of the ratio H_d/H exhibits a minimum. The month to month variations of these parameters are consequent on the dominant atmospheric conditions observed in the months concerned. The monthly average daily total of diffuse radiation (H_dm) was found to be highest in February, 1994 with a value of (3347 ± 45) Wm^–2day^–1, mainly due to the effects of Harmattan haze and thin clouds, while it was found to be lowest in November, 1993 and January, 1994 with a value of about 2500 Wm^–2day^–1. Similarly, the ratio of the monthly average daily total of diffuse radiation to the monthly average daily total of global radiation (H_dm/H_m) had the lowest value of 0.49 in the relatively clear sky month of November, 1993 and the highest value of 0.74 in the mainly cloudy month of August, 1993. On an annual average, the diffuse component constituted about 60% of the global solar radiation arriving on the ground at Ilorin, Nigeria primarily due to clouds and Harmattan haze which are seasonal, in addition to the constant background of molecular scattering.     

Nightglow OH (8, 3) band intensities and rotational temperature at 23°S

The OH (8, 3) band airglow emission has been observed over 1 year at a latitude of 23°S. The average band intensity observed was 385 Rayleighs with a nocturnal range typically less than 100 R. The nocturnal variation in rotational temperature was usually less than 10°K, and the mean temperature was 179°K. The nocturnal variation of intensity is usually uncorrelated with that of the rotational temperature. Time average values of these parameters do, however, show some correlation. On some occasions large post-twilight and pre-dawn intensity enhancements are observed.     

Winter anomalous D-region over Sardinia (40°N)

A simplified D-region model consisting of O₂⁺, NO⁺ and their respective cluster ions grouped as Z_o2⁺ and Z_NO⁺ is used to reproduce the available rocket data on positive ion relative composition and effective clustering rates for the height range 70–90 km. The results of this analysis for a winter anomalous day (Sardinia, 40°N) are in good agreement with the presently known ideas on NO densities, O₂⁺ production rates, mesospheric temperature, negative ion to electron density ratio and effective loss coefficient for electrons. Mesospheric nitric oxide density and temperature profiles from this study are in excellent agreement with the findings of Zbinden et al. (1975) and Hidalgo (1977) for the anomalous day at Sardinia.     

Airglow O2(1Σ) atmospheric band at 8645 Å and the rotational temperature observed at 23°S

Regular observations of theO₂(¹Σ), 0–1) atmospheric band at 8645 Å [O₂A(0, 1)] and the rotational temperature, together with the OH(9,4) band and OI 5577 Å airglow emissions, using multichannel tilting filter type photometers, have been carried out at Cachoeira Paulista (22.7°S, 45.0°W), Brazil, since February 1983. The O₂A(0, 1) band intensities occasionally vary from 200 to 1000 R during a night. Covariations in nocturnal and seasonal variation with the OI 5577 A emission were observed. The temperatures determined from the P branch of the O₂A(0, 1) band vary between 180 and 230 K. The amplitude of the nocturnal temperature variation is sometimes larger than that determined from the OH emission, and the phase of the variation, on some occasions, leads that of the OH.     

Imaging of an unknown sector of Mercury (260–350°W) at the Special Astrophysical Observatory of the Russian Academy of Sciences using the short-exposure method

A series of observations of Mercury were performed at the Special Astrophysical Observatory using the short-exposure method to image a hitherto unknown part of the Hermean surface. Several thousand electronic frames of the planet were taken during its morning elongation in the period from November 20–24, 2006. The phase angle of Mercury varied from 103° to 80°, and the interval of planetocentric longitudes observed spanned from 260 to 350°W. Observations were made with a CCD camera attached to the 1-m Zeiss-1000 Ritchey-Chretien telescope operating with a KS-19 filter (short-wavelength border at 700 nm). The Hermean surface is known to be almost impossible to resolve on ordinary images. A reduction of a large number of frames taken with millisecond-long exposures made it possible to obtain a rather sharp image of the observed part of the Hermean surface. One of the primary aims of new observations was to have a general outline of the basin earlier found by one of the authors (L. Ksanfomaliti). We are the first to image this giant feature. The size of its inner part exceeds that of the largest lunar Mare — Mare Imbrium, however, unlike the latter the studied basin is of impact origin. The synthesized images reveal a number of large impact craters of various ages, as well as smaller features. The highest resolution achieved corresponds to the diffraction limit for the instrument employed, or about 100 km on the Hermean surface.     

Constraints on the flux of meteoritic and cometary water on the Moon from volatile element (N–Ar) analyses of single lunar soil grains,Luna 24 core

We report new nitrogen and argon isotope and abundance results for single breccia clasts and agglutinates from four different sections of the Luna 24 drill core in order to re-evaluate the provenance of N trapped in lunar regolith, and to place limits on the flux of planetary material to the Moon’s surface. Single Luna 24 grains with ⁴⁰Ar/³⁶Ar ratios <1 show δ¹⁵N values between ?54.5‰ and +123.3‰ relative to terrestrial atmosphere. Thus, low-antiquity lunar soils record both positive and negative δ¹⁵N signatures, and the secular increase of the δ¹⁵N value previously postulated by Kerridge (Kerridge, J.F. [1975]. Science 188(4184), 162–164. doi:10.1126/science.188.4184.162) is no longer apparent when the Luna and Apollo data are combined. Instead, the N isotope signatures, corrected for cosmogenic ¹⁵N, are consistent with binary mixing between isotopically light solar wind (SW) N and a planetary N component with a δ¹⁵N value of +100‰ to +160‰. The lower δ¹⁵N values of Luna 24 grains compared to Apollo samples reflect a higher relative proportion of solar N, resulting from the higher SW fluence in the region of Mare Crisium compared to the central near side of the Moon. Carbonaceous chondrite-like micro-impactors match well the required isotope characteristics of the non-solar N component trapped in low-antiquity lunar regolith. In contrast, a possible cometary contribution to the non-solar N flux is constrained to be ?3–13%. Based on the mixing ratio of SW to planetary N obtained for recently exposed lunar soils, we estimate the flux of micro-impactors to be (2.2–5.7) × 10³ tons yr^?1 at the surface of the Moon. Our estimate for Luna 24 agrees well with that for young Apollo regolith, indicating that the supply of planetary material does not depend on lunar location. Thus, the continuous influx of water-bearing cosmic dust may have represented an important source of water for the lunar surface over the past ～1 Ga, provided that water removal rates (i.e., by meteorite impacts, photodissociation, and sputtering) do not exceed accumulation rates.     

Cross section and astrophysical S-factor for 12C(p,γ)13N* reaction with Halo Effective Field Theory at low-energies

We considered one of the proton halo nuclei candidates, ¹³N* nucleus, and calculated the cross section and astrophysical S-factor for ¹²C(p, γ)¹³N* reaction using halo effective field theory without pion (hEFT${}^{\neg \pi }$). The halo effective field theory is used to examine the halo nucleus bound state with a large S-wave scattering length. We calculated the radiative proton capture cross section and the astrophysical S-factor from the fields of the core and the valence proton at the Leading-Order (LO). We showed that there is a good agreement among the our results for cross section and astrophysical S-factor of the ¹²C(p, γ)¹³N* reaction and the experimental data. The astrophysical S-factor that has been estimated at the zero energy (E_cm=0) by using a theoretical calculation of the cross section for direct radiative capture and an extrapolation of this calculation obtained $S\left(0\right)=1.883\times {10}^{-3}$ MeV-b.     

The coronal disturbance (W 90 °, N 25 °) in the eclipse spectra of July 31, 1981

The physical properties in the coronal disturbance (CD) (W90, N25°) associated with an active prominence are investigated on the basis of the intensities and profiles of 5694 Å Caxv and 6702 Å Nixv lines and continuum measured in the eclipse coronal spectra of 31 July, 1981. The spectrograms have been taken with a dispersion of between 7 to 10 Å mm^-1 and a solar image of 15 mm in diameter. The following characteristics of the CD have been deduced. The CD occurred cospatially with an active prominence and consisted of two discrete regions with different temperatures penetrating each other. (1) Caxv region: T _e= 3.8 × 10⁶ K, the length along the slit of the spectrograph Z 65000 km, the effective line-of-sight length L 20000 km, the average electron density , nonthermal velocities V _t= (20–32) km s^-1. (2)Nixv-Caxiii region: T _e= 2.3 × 10⁶ K, Z 37000 km, L 35000 km, n _e 1 × 10⁹ cm^-3, V _t= (23–30) km s^-1. A macroscopic mass motion has been discovered within the Nixv region of the CD from the Doppler shifts of the 6702 Å Nixv line: V _r= + 27 km s^-1 on the lower and V _r= - 12 km s^-1 on the upper border of the CD. The average height of the CD was H 0.08 R . The radial velocities in the prominence found from the emission line tilts are + 12 and - 8 km s^-1 on its lower and upper borders. A similar picture of the mass motion in the CD and the prominence speaks in favour of an intimate relation between them.     

Measurement of the 25Mg(p,γ)26Al reaction at stellar energies

Stellar nuclear reactions, generally occurring at energies well below the Coulomb barrier, have extremely low cross sections posing a very difficult task for their determination using the usual prompt γ-ray detection method. We describe here the application of the highly sensitive Accelerator Mass Spectrometry technique (AMS) as an alternative method for the determination of the resonance strengths of the ²⁵Mg(p,γ) reaction, by off-line counting of the produced ²⁶Al nuclei.     

High fluences of low energy (10–25 MeV/amu) C,N, O and heavier ions at 450 km altitude; results from the skylab experiment

High fluences (i.e. the integrated fluxes) of C, N, O group of nuclei and some of the heavier ones, in the energy interval 10–25 MeV/amu, have been identified in a Lexan polycarbonate detector assembly exposed on the exterior of the Skylab for 73 days. The existence of large flux of low energy nuclei in the Skylab orbit is surprising since the minimum geomagnetic cut-off energy for fully stripped nuclei (A/Z=2) is 50 MeV/amu at the orbit of the satellite, and the period of exposure was a quiet one, free from significant solar particle events. We have considered two sources for these particles: (i) partly ionized interplanetary ions accelerated within the magnetosphere and (ii) heavy nuclei trapped in the Earth's radiation belt. The flux and composition of the nuclei observed by us seem to be significantly different from those in the trapped radiation as known at present; hence it seems likely that the major part of the observed flux may be interpreted, in terms of partly ionized interplanetary ions that are further accelerated in the magnetosphere.     

The astrophysical S-Factor of 4He(3He,γ)7Be reaction at very low-energies

The astrophysical S-factor for ⁴He-³He radiative capture is calculated at very low-energies. We construct conserved two- and three-body electromagnetic currents, using minimal substitution in the explicit momentum dependence of the two- and three-cluster interactions. The realistic Argonne v ₁₈ two-nucleon and Urbana IX or Tucson-Melbourne three-cluster interactions are considered for calculation. The zero energy S-factor is found to be S(0)=0.563 (0.581) keV?b, with (without) three-body interactions, in satisfactory agreement with other theoretical results and experiment data.     

Contribution of 19F resonances on 18O(p,α)15N reaction rate

The ¹⁸O(p,α)¹⁵N reaction influences the isotopes production such as ¹⁹F, ¹⁸O, and ¹⁵N which can be used to test the models of stellar evolution. ¹⁹F is synthesized in both asymptotic giant branch (AGB) and metal-rich Wolf-Rayet (WR) stars. Using R-matrix theory we allow new values of resonances parameters in ¹⁹F. We show that the most important contribution to the differential and total cross section at low energies, comes from the levels in ¹⁹F situated at resonances energies E _R =151, 680 and 840 keV with spin and parity 1/2⁺. The total width of the 680 keV resonance is badly known. So, we have focused on this broad resonance corresponding to the 8.65 MeV level in ¹⁹F. We delimit the temperature range in which each resonance contribution to the total reaction rate occurs by analyzing the ratio (N _A 〈σν〉 _i /N _A 〈σν〉). This allowed us to show that the 680 and 840 keV broad resonances strongly dominate the reaction rate over the stellar temperature range T ₉=0.02–0.06 and T ₉=0.5–5. Finally, these results were compared to NACRE and Iliadis astrophysical compilations.     

Objective prism survey of QSO candidates in field centered at 00h00m + 0° 00': (I) The northeastern quarter

We present the coordinates, B_j, magnitudes and identification charts for 122 quasar candidates (Quality Class Q≥4) found in the northeastern quarter of UK Schmidt Sky Region 823 centered at 0^h00^m, +0°00'. For Q≥ 5 objects, spectral line identifications and redshifts are included.