Type Ia supernovae: An explosion in the regime of a convergent delayed detonation wave

The model of a presupernova’s carbon-oxygen (C-O) core with an initial mass of 1.33 M _⊙, an initial carbon abundance X _C ⁽⁰⁾ =0.27, and a mean rate of increase in mass of 5 × 10^?7 M _⊙ yr^?1 through accretion in a binary system evolved from the central density and temperature ρ_c=10⁹ g cm^?3 and T _c=2.05 × 10⁸K, respectively, by forming a convective core and its subsequent expansion to an explosive fuel ignition at the center. The evolution and explosion equations included only the carbon burning reaction ¹²C+¹²C with energy release corresponding to the complete conversion of carbon and oxygen (at the same rate as that of carbon) into ⁵⁶Ni. The ratio of mixing length to convection-zone size α_c was chosen as the parameter. Although the model assumptions were crude, we obtained an acceptable (for the theory of supernovae) pattern of explosion with a strong dependence of its duration on α_c. In our calculations with sufficiently large values of this parameter, α_c=4.0 × 10^?3 and 3.0×10^?3, fuel burned in the regime of prompt detonation. In the range 2.0×10^?3≥α_c≥3.0×10^?4, there was initially a deflagration with the generation of model pulsations whose amplitude gradually increased. Eventually, the detonation regime of burning arose, which was triggered from the model surface layers (with m ? 1.33 M _⊙) and propagated deep into the model up to the deflagration front. The generation of model pulsations and the formation of a detonation front are described in detail for α_c=1.0 × 10^?3.     

Gravity field of Mars from Mariner 9 tracking data

Further reduction of Doppler tracking data from Mariner 9 confirms our earlier conclusion that the gravity field of Mars is considerably rougher than the fields of either the Earth or the Moon. The largest positive gravity anomaly uncovered is in the Tharsis region which is also topographically high and geologically unusual. The best determined coefficients of the harmonic expansion of the gravitational potential are: J₂ = (1.96 ± 10.01) × 10^?3 ; C₂₂ = ?(5.1 ± 0.2) × 10^?5; and S₂₂ = (3.4 ± 0.2) × 10^?5. The other coefficients have not been well determined on an individual basis, but the ensemble yields a useful model for the gravity field for all longitudes in the vicinity of 23° South latitude which corresponds to the periapse position for the orbiter.The value obtained for the inverse mass of Mars (3 098 720 ± 70 M⊙^?1) is in good agreement with prior determinations from Mariner flyby trajectories. The direction found for the rotational pole of Mars, referred to the mean equinox and equator of 1950.0, is characterized by α = 317°.3 ± 0°.2, δ = 52°.7 ± 0°.2. This result is in excellent agreement with Sinclair's recent value, determined from earth-based observations of Mars' satellites, but differs by about 0°.5 from the previously accepted value. Other important physical constants that have either been refined or confirmed by the Mariner 9 data include: (i) the dynamical flattening, f = (5.24 ± 0.02) × 10^?3; (ii) the maximum principal moment of inertia, C = (0.375 ± 0.006) MR²; and (iii) the period of precession of Mars' pole, P ? (1.73 ± 0.03) × 10⁵ yr, corresponding to a rate of 7.4 sec of arc per yr.     

Simultaneous measurements of No and No2 in the stratosphere

Simultaneous measurements of NO and NO₂ in the stratosphere leading to an NO_x determination have been performed by means of i.r. absorption spectrometry using the Sun as a source in the 5·2 μm band of NO and in the 6·2 μm band of NO₂. The observed abundance of NO_P peaks at 26 km where it is equal to (4·2 ± 1) × 10⁹ cm^?3. The volume mixing ratio of NO_p was observed to vary from 1·3 × 10^?9 at 20 km to 1·3 × 10^?8 at 34 km.     

Lunar and terrestrial tidal effects on the Moon's rotational motion

An accurate model of the rotation of the Moon, constructed by numerical integration, has been presented in a previous paper. All direct perturbations capable of producing at least 10^–4 seconds of arc on the Moon's rotational motion have been included, and the physical librations resulting from planetary effects and Earth-Moon figure-figure interactions have been presented. The present study deals with the Moon's physical librations resulting from the non-rigidities of the Moon and the Earth. The effects of the Moon's elasticity and of a lunar phase lag are analyzed. Physical librations due to lunar tides and those due to terrestrial tides are presented and described.     

An estimate of the PH3, CH3D,and GeH4 Abundances on Jupiter from the Voyager IRIS data at 4.5 μm

The abundances of PH₃, CH₃D, and GeH₄ are derived from the 2100- to 2250-cm^?1 region of the Voyager 1 IRIS spectra. No evidence is seen for large-scale variations of the phosphine abundance over Jovian latitudes between ?30 and +30°. In the atmospheric regions corresponding to 170–200°K, the derived PH₃/H₂ value is (4.5 ± 1.5) × 10^?7 or 0.75 ± 0.25 times the solar value. This result, compared with other PH₃ determinations at 10 μm, suggests than the PH₃/H₂ ratio on Jupiter decreases with atmospheric pressure. In the 200–250°K region, we derive, within a factor of 2, CH₃D/H₂ and GeH₄/H₂ ratios of 2.0 × 10^?7 and 1.0 × 10^?9, respectively. Assuming a C/H value of 1.0 × 10^?3, as derived from Voyager, our CH₃D/H₂ ratio implies a D/H ratio of 1.8 × 10^?5, in reasonable agreement with the interstellar medium value.     

Solar radiation scattered in the Venus atmosphere: The Venera 11,12 data

Results of the scattered solar radiation spectrum measurements made deep in the Venus atmosphere by the Venera 11 and 12 descent probes are presented. The instrument had two channels: spectrometric (to measure downward radiation in the range 0.45 < γ < 1.17 μm) and photometric (four filters and circular angle scanning in an almost vertical plane). Spectra and angular scans were made in the height range from 63 km above the planet surface. The integral flux of solar radiation is 90 ± 12 W m^?2 measured on the surface at the subsolar point. The mean value of surface absorbed radiation flux per planetary unit area is 17.5 ± 2.3 W m^?2. For Venera 11 and 12 landing sites the atmospheric absorbed radiation flux is ～15 W m^?2 for H >; 43 km and ～45 W m^?2 for H < 48 km in the range 0.45 to 1.55 μm. At the landing sites of the two probes the investigated portion of the cloud layer has almost the same structure: it consists of three parts with boundaries between them at about 51 and 57 km. The base of clouds is near 48 km above the surface. The optical depth of the cloud layer (below 63 km) in the range 0.5 to 1 μm does not depend on the wavelength and is ～29 and ～38 for the Venera 11 and 12 landing sites, respectively. The single-scattering albedo, ω₀, in the clouds is very close to 1 outside the absorption bands. Below 58 km the parameter (1 ? ω₀) is <10^?3 for 0.49 and 0.7 μm. The parameter (1 ? ω₀) obviously increases above 60 km. Below 48 km some aerosol is present. The optical depth here is a strong function of wavelength. It varies from 1.5 to 3 at λ = 0.49 μm and from 0.13 to 0.4 at 1.0 μm. The mean size of particles below the cloud deck is about 0.1 μm. Below 35 km true absorption was found at λ < 0.55 μm with the (1 ? ω₀) maximum at H ≈ 15 km. The wavelength and height dependence of the absorption coefficient are compatible with the assumption that sulfur with a mixing ratio ～2 × 10^?8 normalized to S₂ molecules is the absorber. The upper limits of the mixing ratio for Cl₂, Br₂, and NO₂ are 4 × 10^?8, 2 × 10^?11, and 4 × 10^?10, respectively. The CO₂ and H₂O bands are confidently identified in the observed spectra. The mean value of the H₂O mixing ratio is 3 × 10^?5 < F_H2O < 10^?4 in the undercloud atmosphere. The H₂O mixing ratio evidently varies with height. The most probable profile is characterized by a gradual increase from F_H2O = 2 × 10^?5 near the surface to a 10 to 20 times higher value in the clouds.     

On the velocity of jets powering hot spots similar to those in Cygnus A

Hot spots similar to those in the radio galaxy Cygnus A can be explained by the strong shock produced by a supersonic but classical jet \(\left( {u_{jet}< c/\sqrt 3 } \right)\) . The high integrated radio luminosity (L?2×10⁴⁴ erg s^?1) and the strength of mean magnetic field (B?2×10^?4 G) suggest the hot spots are the downstream flow of a very strong shock which generates the ultrarelativistic electrons of energy ?≥20 MeV. The fully-developed subsonic turbulence amplifies the magnetic field of the jet up to 1.6×10^?4 G by the dynamo effect. If we assume that the post-shock pressure is dominated by relativistic particles, the ratio between the magnetic energy density to the energy density in relativistic particles is found to be ?2×10^?2, showing that the generally accepted hypothesis of equipartition is not valid for hot spots. The current analysis allows the determination of physical parameters inside hot spots. It is found that:

1. The velocity of the upstream flow in the frame of reference of the shock isu ₁?0.2c. Radio observations indicate that the velocity of separation of hot spots isu _sep?0.05c, so that the velocity of the jet isu _jet=u ₁+u _sep?0.25c.
2. The density of the thermal electrons inside the hot spot isn ₂?5×10^?3 e ^? cm^?3 and the mass ejected per year to power the hot spot is ?4M ₀yr^?1.
3. The relativistic electron density is less than 20% of the thermal electron density inside the hot spot and the spectrum is a power law which continues to energies as low as 30 MeV.
4. The energy density of relativistic protons is lower than the energy density of relativistic electrons unlike the situation for cosmic rays in the Galaxy.

     

Impact of the Quadrupole Moment of the Sun on the Dynamics of the Earth-Moon System

Range of values of the Sun's mass quadrupole moment of coefficient J₂ arising both from experimental and theoretical determinations enlarge across literature on two orders of magnitude, from around 10^-7 until to 10^-5. The accurate knowledge of the Moon's physical librations, for which the Lunar Laser Ranging data reach an outstanding precision level, prove to be appropriate to reduce the interval of J₂ values by giving an upper bound of J₂. A solar quadrupole moment as high as 1.1 10^-5 given either from the upper bounds of the error bars of the observations, or from the Roche's theory, is not compatible with the knowledge of the lunar librations accurately modeled and observed with the LLR experiment. The suitable values of J₂ have to be smaller than 3.0 10^-6. As a consequence, this upper bound of 3.0 10^-6 is accepted to study the impact of the Sun's quadrupole moment of mass on the dynamics of the Earth-Moon system. Such as effect (with J₂ = 5.5±1.3 × 10^-6) has been already tested in 1983 by Campbell & Moffat using analytical approximate equations, and thus for the orbits of Mercury, Venus, the Earth and Icarus. The approximate equations are no longer sufficient compared with present observational data and exact equations are required. As if to compute the effect on the lunar librations, we have used our BJV relativistic model of solar system integration including the spin-orbit coupled motion of the Moon. The model is solved by numerical integration. The BJV model stems from general relativity by using the DSX formalism for purposes of celestial mechanics when it is about to deal with a system of n extended, weakly self-gravitating, rotating and deformable bodies in mutual interactions. The resulting effects on the orbital elements of the Earth have been computed and plotted over 160 and 1600 years. The impact of the quadrupole moment of the Sun on the Earth's orbital motion is mainly characterized by variations of , , and . As a consequence, the Sun's quadrupole moment of mass could play a sensible role over long time periods of integration of solar system models. This revised version was published online in July 2006 with corrections to the Cover Date.     

Revivals of a coronal arch

The giant post-flare arch of 6 November 1980 revived 11 hr and 25 hr after its formation. Both these revivals were caused by two-ribbon flares with growing systems of loops. The first two brightenings of the arch were homologous events with brightness maxima moving upwards through the corona with rather constant speed; during all three brightenings the arch showed a velocity pattern with two components: a slow one (8–12 km^?1), related to the moving maxima of brightness, and a fast one (～ 35 km s^?1), the source of which is unknown. During the first revival, at an altitude of 100000 km, temperature in the arch peaked ～ 1 hr, brightness ～ 2 hr, and emission measure ～ 3.5 hr after the onset of the brightening. Thus the arch looks like a magnified flare, with the scales both in size and time increased by an order of magnitude. At ～ 100000 km altitude the maximum temperature was ?14 × 10⁶K, max.n _e? 2.5 × 10⁹cm^?3, and max. energy density ? 11.2 erg cm^?3. The volume of the whole arch can be estimated to 1.1 × 10³⁰ cm³, total energy ?1.2 × 10³¹ erg, and total mass ?4.4 × 10¹⁵g. The density decreased with the increasing altitude and remained below 7 × 10⁹ cm^?3 anywhere in the arch. The arch cooled very slowly through radiation whereas conductive cooling was inhibited. Since its onset the revived arch was subject to energy input within the whole extent of the preexisting arch while a thermal disturbance (a new arch?) propagated slowly from below. We suggest that the first heating of the revived arch was due to reconnection of some of the distended flare loops with the magnetic field of the old preexisting arch. The formation of the ‘post’-flare loop system was delayed and started only some 30–40 min later. Since that time a new arch began to be formed above the loops and the velocities we found reflect this formation.     

Measurements of the light flash produced by high velocity particle impact

The impact light flash produced by electrostatically accelerated iron particles with diameters meters ranging from 5 to 0.05 μm and velocities lying between 1 km/sec and 30 km/sec has been investigated by means of photomultipliers. As target materials mainly gold and tungsten were used. The pulse of the multiplier was registered directly and after electronic integration. The pulse height of the multiplier signal, the amplitude of the integrated signal as well as its rise time were found to be unique functions of the mass and velocity of the impacting particle. For the pulse height of the differential signal the relation I = c₁ × m^1.25 × v⁵ was obtained, and for the integrated signal the relation I = c₂ × m^1.25 × v^3.8, with only c₁ and C₂ depending on the target material. The rise time of the integrated signal follows the relation T = 2.2 × 10² × v^?0.4 using gold as target, and in the case of tungsten material follows the relation T = 9.8 × 10² × v^?1.2, where v is expressed in km/sec and T in μsec. Using the spectral distribution of the light intensity, measured by means of calibrated photomultipliers, the total amount of light energy emitted in the visible range could be calculated. As a result we obtained that for v = 4 km/sec and m = 10^?11 g about 3 × 10^?4 of the kinetic energy of the particle was converted into light energy. The variation of the impact flash intensity with the target material and the measured spectral distribution allowed the temperature of the crater after the impact to be estimated as between 2000 and 3000 K.     

On the petrology and structure of a gravitionally differentiated moon of fission origin

In a previous paper, it was shown that the basic properties and the developmental history of a gravitationally differentiated Moon of fission origin match those known for the Moon. In the first part of this report, the models of a differentiated Moon are critically reviewed based on second order considerations of some of the chemical systems used to develope the earlier models and based on new lunar data. As a result, slightly updated models are developed and the results indicate that a Moon of fission origin has a feldspar rich crust (≈70% Or_0.8Ab_5.3An_93.9 with ≈30% pyroxene and olivine) reaching an average depth of ≈65 km. A KREEP rich layer is located at the interface of the crust and the upper mantle. The upper mantle consists of peridotite (≈80% Wo₁₀En₇₀Fs₂₀ and ≈20% Fo_75–80 with ≈3% Al₂O₃ and ≈ 2% TiO₂) and reaches a depth of 300–400 km. Below 300–400 km lies a dunite (≈Fo₉₅) lower mantle. A simple model for the distribution of K, U and Th (and by inference, KREEP) in the differentiated Moon model is developed using a distribution coefficient of 0.1 for the three elements. This coefficient is derived from published data on the distribution of U in Apollo 11 basalts. The simple model successfully accounts for the observed K, U and Th contents of the various mare basalts and upland rocks and yields a heat flow of 21 erg cm^?2s^?1 for the Moon. A model for the fine structure of the peridotite upper mantle of the model Moon is developed based on the TiO₂ and trace element variations observed in the various mare basalts. It is proposed that the upper mantle is rhythmically banded on the scale of 10's of km and that this banding leads to local variations of a factor of ±3 in the K, U and Th content, _-10 ⁺⁵ in the TiO₂ content and _-∞ ⁺² in the olivine content of the peridotite. It is also proposed that this banding leads to large scale horizontal inhomogenuities in the composition of the upper mantle. It is also shown that the formation of the primitive suite of upland rocks is easily explained by the cumulation of plagioclase, which carried varying amounts of pyroxene, olivine and melt with it, during the peritectic crystallization of the last 20% of the differentiating Moon. It is found that the 100 Mg/(Mg+Fe) ratios of the mafics and the An contents of the plagioclases of the rocks are controlled by several factors, the most important of which is the ratio of melt to crystals which together formed the various upland rocks. The inverse relationship between the An contents and the Mg contents of the upland rocks is a direct consequence of the differentiation sequence proposed. The results and models presented in this paper further support the hypothesis that the Moon formed as a result of fission from the proto-Earth.     

Manganese‐chromium formation intervals for chondrules from the Bishunpur and Chainpur meteorites

Abstract— Whole‐chondrule Mn‐Cr isochrons are presented for chondrules separated from the Chainpur (LL3.4) and Bishunpur (LL3.1) meteorites. The chondrules were initially surveyed by instrumental neutron activation analysis. LL‐chondrite‐normalized Mn/Cr, Mn/Fe, and Sc/Fe served to identify chondrules with unusually high or low Mn/Cr ratios, and to correlate the abundances of other elements to Sc, the most refractory element measured. A subset of chondrules from each chondrite was chosen for analysis by a scanning electron microscope equipped with an energy dispersive x‐ray spectrometer prior to high‐precision Cr‐isotopic analyses. ⁵³Cr/⁵²Cr correlates with ⁵⁵Mn/⁵²Cr to give initial (⁵³Mn/⁵⁵Mn)_I = (9.4 ± 1.7) × 10^?6 for Chainpur chondrules and (⁵³Mn/⁵⁵Mn)_I = (9.5 ± 3.1) × 10^?6 for Bishunpur chondrules. The corresponding chondrule formation intervals are, respectively, Δ_tLEW = ?10 ± 1 Ma for Chainpur and ?10 ± 2 Ma for Bishunpur relative to the time of igneous crystallization of the Lewis Cliff (LEW) 86010 angrite. Because Mn/Sc correlates positively with Mn/Cr for both the Chainpur and Bishunpur chondrules, indicating dependence of the Mn/Cr ratio on the relative volatility of the elements, we identify the event dated by the isochrons as volatility‐driven elemental fractionation for chondrule precursors in the solar nebula. Thus, our data suggest that the precursors to LL chondrules condensed from the nebula 5.8 ± 2.7 Ma after the time when initial (⁵³Mn/⁵⁵Mn)_I = (2.8 ± 0.3) × 10^?5 for calcium‐aluminum‐rich inclusions (CAIs), our preferred value, determined from data for (a) mineral separates of type B Allende CAI BR1, (b) spinels from Efremovka CAI E38, and (c) bulk chondrites. Mn‐Cr formation intervals for meteorites are presented relative to average I(Mn) = (⁵³Mn/⁵⁵Mn)_Ch = 9.46 × 10^?6 for chondrules. Mn/Cr ratios for radiogenic growth of ⁵³Cr in the solar nebula and later reservoirs are calculated relative to average (I(Mn), ?(⁵³Cr)_I) = ((9.46 ± 0.08) × 10^?6, ?0.23 ± 0.08) for chondrules. Inferred values of Mn/Cr lie within expected ranges. Thus, it appears that evolution of the Cr‐isotopic composition can be traced from condensation of CAIs via condensation of the ferromagnesian precursors of chondrules to basalt generation on differentiated asteroids. Measured values of ?(⁵³Cr) for individual chondrules exhibit the entire range of values that has been observed as initial ?(⁵³Cr) values for samples from various planetary objects, and which has been attributed to radial heterogeneity in initial ⁵³Mn/⁵⁵Mn in the early solar system. Estimated ⁵⁵Mn/⁵²Cr = 0.42 ± 0.05 for the bulk Earth, combined with ?(⁵³Cr) = 0 for the Earth, plots very close to the chondrule isochrons, so that the Earth appears to have the Mn‐Cr systematics of a refractory chondrule. Thus, the Earth apparently formed from material that had been depleted in Mn relative to Cr contemporaneously with condensation of chondrule precursors. If, as seems likely, the Earth's core formed after complete decay of ⁵³Mn, there must have been little differential partitioning of Mn and Cr at that time.     

Lightnings and nitric oxide on Venus

In an updating of energy characteristics of lightnings on Venus obtained from Venera-9 and -10 optical observations, the flash energy is given as 8 × 10⁸ J and the mean energy release of lightnings is 1 erg cm^?2 s which is 25 times as high as that on the Earth. Lightnings were observed in the cloud layer. The stroke rate in the near-surface atmosphere is less than 5 s^?1 over the entire planet if the light energy of the stroke exceeds 4 × 10⁵ J and less than 15 s^?1 for (1–4) × 10⁵ J.The average NO production due to lightnings equals 5 × 10⁸ cm^?2 s^?1, the atomic nitrogen production is equal to 7 × 10⁹ cm^?2s^?1,the N flux toward the nightside is 3.2 × 10⁹ cm^?2s^?1, the number densities [N] = 3 × 10⁷cm^?3 and [NO] = 1.8 × 10⁶cm^?3 at 135 km. Almost all NO molecules in the upper atmosphere vanish interacting with N and the resulting NO flux at 90-80 km equals 5 × 10⁵cm^?2s^?1, which is negligibly small as compared with lightning production. If the predissociation at 80–90 km is regarded as the single sink of NO, its mixing ratio, f_NO, is 4 × 10^?8, for the case of a surface sink f_NO = 0.8 × 10^?9 at 50 km. Excess amounts, $\text{f}{}_{\mathrm{<mtext>NO</mtext>}}\text{? 4 × 10}{}^{\mathrm{?8}}$, may exist in the thunderstorm region.     

A seasonal climate model of the atmospheres of the giant planets at the voyager encounter time: I. Saturn's stratosphere

A radiative seasonal model which incorporates a multilayer radiative transfer treatment at wave-lengths longward of 7 μm is presented and applied to Saturn's stratosphere. Opacities due to H₂-He, CH₄, C₂H₂, and C₂H₆ are included. Season-dependent insolation is shown to produce a strong hemispheric asymmetry decreasing with depth at the Voyager encounter times, and seasonal amplitudes of 30°K at the poles are predicted in the high stratosphere. The ring-modulated dependence of the insolation and the orbital eccentricity are shown to have a significant effect. Calculations agree closely with the Voyager 1 and 2 radio occultation ingress profiles recorded at 76°S and 36.5°S for CH₄/H₂ = 3.5 + 1.4/? 1.0 × 10^?3;the estimated errors include modeling systematic errors and uncertainties in the occultations profiles. The possible role of aerosols in the stratospheric heating is analyzed. The Voyager 2 egress profile recorded at 31°S cannot be reproduced by calculations. Some constraints on the C₂H₂ and C₂H₆ abundances are derived. The upper portion of the occultation profiles (p < 3mbar) can be matched for C₂H₂/H₂ = 1.0 + 1.3/?0.6 × 10^?7, C₂H₆/H₂ = 1.5 + 1.8/?0.9 × 10^?6 at 76°S and C₂H₂/H₂ = 4 + 6/?4 × 10^?8, C₂H₆/H₂ = 6 + 9/?6 × 10^?7 at 36.5°N. At the northern occultation latitude, the discrepancy with the concentrations derived from analysis of IRIS spectra by R. Courtin, D. Gautier, A. Marten, B. Bézard, and R. Hanel (1984, Astrophys. J.287) can be explained by a sharp variation of the mixing ratios of these gases with altitude in the upper stratosphere. Other interpretations are discussed.     

Infrared photometry of Nova Delphini 2013 (=V339 Del) in the first sixty days after its outburst

The results of JHKLM photometry for Nova Delphini 2013 obtained in the first sixty days after its outburst are analyzed. Analysis of the energy distribution in a wide spectral range (0.36–5 µm) has shown that the source mimics the emission of normal supergiants of spectral types B5 and A0 for two dates near its optical brightness maximum, August 15.94 UT and August 16.86 UT, respectively. The distance to the nova has been estimated to be D ≈ 3 kpc. For these dates, the following parameters have been estimated: the source’s bolometric fluxes ～9 × 10^?7 and ～7.2 × 10^?7 erg s^?1 cm^?2, luminosities L ≈ 2.5 × 10⁵ L _⊙ and ≈2 × 10⁵ L _⊙, and radii R ≈ 6.3 × 10¹² and ≈1.2 × 10¹³ cm. The nova’s expansion velocity near its optical brightness maximum was ～700 km s^?1. An infrared (IR) excess associated with the formation of a dust shell is shown to have appeared in the energy distribution one month after the optical brightness maximum. The parameters of the dust component have been estimated for two dates of observations, JD2456557.28 (September 21, 2013) and JD2456577.18 (October 11, 2013). For these dates, the dust shell parameters have been estimated: the color temperatures ≈1500 and ≈1200 K, radii ≈6.5 × 10¹³ and 1.7 × 10¹⁴ cm, luminosities ～4 × 10³ L _⊙ and ～1.1 × 10⁴ L _⊙, and the dust mass ～1.6 × 10²⁴ and ～10²⁵ g. The total mass of the material ejected in twenty days (gas + dust) could reach ～1.1 × 10^?6 M _⊙. The rate of dust supply to the nova shell was ～8 × 10^?8 M _⊙ yr^?1. The expansion velocity of the dust shell was about 600 km s^?1.     

Variations of the stratospheric temperature along the limb of Uranus: Results of the 22 April 1982 stellar occultation

Stratospheric temperature profiles of Uranus were derived from the stellar occultation of 22 April 1982 in the pressure range 5–30 μbar. The observations were made at the European Southern Observatory, Chile, and at the Observatoire du Pic du Midi et de Toulouse, France with two telescopes in both sites. The study of these profiles confirms that Uranus' stratosphere is warmer than had been expected from radiative models (J. F. Appleby, 1980, Atmospheric Structures of the Giant Planets from Radiative-Convective Equilibrium Models. PhD. Thesis, State University of New York at Stony Brook) and that there has been a general increase of temperature since 1977 (R. G. French, J. L. Elliot, E. W. Dunham, D. A. Allen, J. H. Elias, J. A. Frogel, and W. Liller, 1983, Icarus53, 399–414). Furthermore, the profiles exhibit a nonisothermal feature with a maximum temperature around the 8-μbar pressure level. The amplitude of this feature increases linearly with the diurnally averaged insolation 〈D〉 up to the observed value 〈D〉 ～ 0.15. Moreover, the temperature at 8 μbar, as well as the mean stratospheric temperature, reaches a plateau around the equator of the planet which is far from maximum insolation. For a nominal abundance of methane η_CH4 ～ 3 × 10^?5 and normal incidence, the UV absorption could compete with the IR methane absorption bands at the pressure level 8 μbar. However, the high temperatures observed even at grazing incidence imply important circulation phenomena to isothermalize distant regions of the planet. Alternatively, the observed profiles may suggest that an optically thin aerosol layer distributed over one scale height is responsible for the temperature maximum at 8 μbar. The total mass of dust necessary to heat this region up significantly would be a small fraction (6 × 10¹⁰ g vs 5 × 10¹⁸ g) of the Uranian ring system, which appears then as a possible reservoir of dust. However, a falling rate of ～1 msec^?1 would deplete the rings in a short time (≈2 × 10⁵ years) so that a dynamical process is needed to sustain the aerosol layer.     

Lunar electric fields,surface Potential and Associated Plasma Sheaths

This paper reviews the electric field environment of the Moon. Lunar surface electric potentials are reported as follows: Solar Wind - Dayside: ø_o + 10 to + 18 V Solar Wind - Terminator: ø_o ç ? 10 to ? 100 V Electron and ion densities in the plasma sheath adjacent to each surface potential regime are evaluated and the corresponding Debye length estimated. The electric fields are then approximated by the surface potential over the Debye length. The results are: Solar Wind - Dayside: E_o ? 10 V m^?1 outward Solar Wind - Terminator: E_o ç 1 to 10 V m^?1 inward These fields are all at least 3 orders of magnitude higher than the pervasive solar wind electric field; however they are confined to within a few tens of meters of the lunar surface.     

Relation of a contracting earth to the apparent accelerations of the sun and moon

The tidal theory of the evolution of the lunar orbit has remained inconsistent with the observational values of the apparent secular accelerations of the Sun and Moon since it was first developed by Jeffreys in 1920. Allowance for a changing moment of inertia of the Earth enables the discrepancy to be completely removed if a decrease is occurring at a rate of just about the amount already required by the phase-change theory of the nature of the terrestrial core. The agreement of the resulting theory with the latest determinations of the lunar acceleration increases confidence in the phase-change hypothesis. On the other hand the theory renders it most unlikely that a changing constant of gravitation will prove necessary to account for the observations. On the present theory of itself the Moon would have been extremely close to the Earth only about 10⁹ yr ago which suggests that some additional process may at times have influenced the lunar orbit.     

Spectral analysis of the optical continuum in the 24 April 1981 flare

Spectrograph and multiple-band polarimeter observations of the 24 April 1981 white-light flare indicate the presence of an optical continuum with intensity increasing strongly below 4000 Å. The flare emission (lines and continuum combined) is unpolarized and, at 3600 Å, exceeds the brightness of the background solar surface by 360%. Analysis of the spectrum between 3600 and 8200 Å, at a location three arc sec from the brightest point in the kernel, yields a probable temperature of 6700 K for the continuum emitting layer. The wavelength dependence of the continuum indicates emission by both negative hydrogen (H^?) and Balmer continuum, with the H^? probably originating in the upper photosphere at a height (above τ_{5000 Å} = 1) in the range 200–300 km. Analysis of the Balmer lines and continuum yields an electron density 5.3 × 10¹³ cm^?3 and a second-level hydrogen column density 1.1 × 10¹⁶ cm^?2. The peak radiative output integrated over wavelength is 6.1 × 10²⁷ erg s^?1. The observed continuum intensity, if originating at a height of 300 km, implies an energy loss rate of 10³ erg s^?1 cm^?3.