Deactivation of N2A Σumolecules in the aurora

Recent rocket observations of the N₂ V-K (Vegard-Kaplan) system in the aurora have been reinterpreted using an atmospheric model based on mass spectrometer measurements in an aurora of similar intensity at the same time of year. In contrast to the original interpretation, we find that population by cascade from the C³Π_u and B³Π_g states in the A³Σ_u⁺v=0,1 levels, as calculated using recently measured electron excitation cross sections, accurately accounts for the observed relative emission rates (IV-K/12PG_0.0). In addition there is no need to change the production rate of A ³ Σ _u⁺ molecules relative to that of C³Π_uv=0 as a function of altitude in order to fit the profile of the deactivation probability to the atmospheric model. Quenching of A ³ Σ _u⁺ molecules at high altitudes is dominated by atomic oxygen. The rate constants for the v=0 and v=1 levels are 8 × 10⁻¹¹ cm³ sec⁻¹ and 1.7 × 10⁻¹⁰ cm³ sec⁻¹ respectively, as determined using the model atmosphere mentioned above. Recent observations with a helium cooled mass spectrometer suggest that conventional mass spectrometer measurements tend to underestimate the atomic oxygen relative concentration. The rate coefficients may therefore be too large by as much as a factor of 3. Below 130 Km we find that it is possible to account for the deactivation in bright auroras by invoking large nitric oxide concentrations, similar to those recently observed mass spectrometrically and using a rate constant of 8 × 10⁻¹¹ cm³ sec⁻¹ for both the v=1 levels. This rate constant is very nearly the same as that measured in the laboratory (7 × 10⁻¹¹ cm³ sec⁻¹). Molecular oxygen appears not to play a significant role in deactivating the lower A ³ Σ _u⁺ levels.     

Generalized limits to the number of light particle degrees of freedom from big bang nucleosynthesis

We compute the big bang nucleosynthesis limit on the number of light neutrino degrees of freedom in a model-independent likelihood analysis based on the abundances of ⁴He and ⁷Li. We use the two-dimensional likelihood functions to simultaneously constrain the baryon-to-photon ratio and the number of light neutrinos for a range of ⁴He abundances Y_p = 0.225–0.250, as well as a range in primordial ⁷Li abundances from (1.6 to 4.1) ×10⁻¹⁰. For (⁷Li/H)_p = 1.6 × 10⁻¹⁰, as can be inferred from the ⁷Li data from Population II halo stars, the upper limit to N_ν based on the current best estimate of the primordial ⁴He abundance of Y_p = 0.238 is N_ν < 4.3 and varies from N_ν < 3.3 (at 95% C.L.) when Y_p = 0.225 to N_ν < 5.3 when Y_p = 0.250. If ⁷Li is depleted in these stars the upper limit to N_ν is relaxed. Taking (⁷Li/H)_p = 4.1 × 10⁻¹⁰, the limit varies from N_ν < 3.9 when Y_p = 0.225 to N_ν 6 when Y_p = 0.250. We also consider the consequences on the upper limit to N_ν if recent observations of deuterium in high-redshift quasar absorption-line systems are confirmed.     

The Cr and Sr sources in BOREXINO as tools for neutrino magnetic moment searches

We calculate the event rates induced by a ⁵¹Cr ν_e source and by a ⁹⁰Sr---⁹⁰Y source in BOREXINO through elastic scattering on electrons, assuming a nonzero neutrino magnetic moment μ_ν. We consider a source activity of about 2 MCi and estimate the solar ν (“source-off”) background for various oscillation scenarios. It is shown that values of μ_ν as low as 0.5 × 10⁻¹⁰μ_B ( 0.2 × 10⁻¹⁰μ_B) can be proved with the ⁵¹Cr source (⁹⁰Sr source) in about 100 days of data taking.     

The shape of the power spectrum of cosmic ray at ground level up to 7 × 10 Hz

The power spectral density of cosmic ray fluctuations observed at ground level during the years 1966–1968 has been calculated. In order to obtain the correct shape of the spectrum, the Fast Fourier Transform method with a triangular data window was used and corrections were made for uncorrelated errors and aliasing effects. When ignoring the Earth rotation peaks, the spectral index , for a sample of polar, middle latitude and equatorial stations, is − 1.96 in the frequency range 3 × 10⁻⁷–10⁻⁴ Hz. A possible break around 10⁻⁵ Hz, if existing, would be, on the whole, barely significant as a would change from − 1.96 to − 2.10. There are indications that beyond 10⁻⁴ Hz up to 7 × 10⁻³ Hz the spectrum continues with − 2.     

Nightside ionosphere of Venus

Venera 9, 10 measurements of the nightside ionospheric profile and the night airglow were used for investigating ionosphere formation processes. The upper ionospheric layer may be formed by HeI 584 Å radiation; the lower layer by meteorite ionization. Upper limits on the electron energy flux, <4 × 10⁸eV cm⁻² s⁻¹, the helium ion flux <10⁷ cm⁻² s⁻¹, the nitric oxide mixing ratio, <1.5 × 10⁻⁴ and the atomic sulphur mixing ratio, <10⁻⁶, are deduced for ionospheric altitudes.     

Observation and Study of the CO, CO, HCO and N2H Molecular Lines Towards IRAS 02232+6138

Using the 13.7 m millimeter-wave telescope at the Qinghai Station of Purple Mountain Observatory, we have made observations of ¹³CO, C¹⁸O, HCO⁺ and N₂H⁺ molecular lines towards IRAS 02232+6138. As the excitation density of the probe molecule increases from ¹³CO to HCO⁺, the size of the cloud core associated with IRAS 02232+6138 decreases from 2.40 pc to 0.54 pc, and the virial mass of the cloud core decreases from 2.2 × 10³M to 5.1 × 10²M. A bipolar molecular outflow is found towards IRAS 02232+6138. Using the power function n(r) ∝ r⁻ to fit the spatial density structure of the cloud core, we obtain the power-law index  = 2.3 − 1.2; and we find that, as the probed density increases, the power function becomes more flat. The abundance ratio of ¹³CO to C¹⁸O is 12.4 ± 6.9, comparable with the values 11.8 ± 5.9 for dark clouds and the values 9.0–15.6 for massive cores. The abundance of N₂H⁺ molecules is 3.5 ± 2.5 × 10⁻¹⁰, consistent with the value 1.0 − 5.0 × 10⁻¹⁰ for dark cloud cores and the value 1.2 − 12.8 × 10⁻¹⁰ for massive cores. The abundance of HCO⁺ molecules is 0.9 ± 0.5 × 10⁻⁹, close to the value 1.6 − 2.4 × 10⁻⁹ for massive cores. An increase of HCO⁺ abundance in the outflow region was not found. Combining with the IRAS data, the luminosity-mass ratio of the cloud core is obtained in the range 37–163(L/M). Based on the IRAS luminosity, it is estimated that a main-sequence O7.5 star is probably embedded in the IRAS 02232+6138 cloud core.     

Galactic gamma halo by heavy neutrino annihilations?

The diffused gamma halo around our Galaxy recently discovered by EGRET could be produced by annihilations of heavy relic neutrinos N (of fourth generation), whose mass is within a narrow range (M_Z/2<m_N<M_Z). Neutrino annihilation in the halo may lead to either ultrarelativistic electron pairs whose Inverse Compton Scattering on infrared and optical galactic photons could be the source of observed GeV gamma rays, or prompt 100 MeV–1 GeV photons (due to neutral pion secondaries) born by reactions. The consequent gamma flux (10⁻⁷–10⁻⁶ cm⁻² s⁻¹ sr⁻¹) is well comparable to the EGRET observed one, and it is also compatible with the narrow window of neutrino mass 45 GeV <m_N<50 GeV, recently required to explain the underground DAMA signals.The presence of heavy neutrinos of fourth generation do not contribute much to solve the dark matter problem of the Universe, but may be easily detectable by outcoming LEP II data.     

Measurements of radio noise at 0.700 mc and 2.200 mc from a high-altitude rocket probe

Radio noise observations at frequencies of 0·700 Mc and 2·200 Mc were made at altitudes between 3000 and 11,000 km from a Blue Scout Jr. high-altitude rocket probe on 30 July 1963. A steady background flux of (7·5₋₃⁺⁶) × 10⁻¹⁹ W m⁻²)(c/s)⁻¹ at 0·700 Mc and (1·8^+1.0_−0.5 × 10⁻¹⁹ W m⁻² (c/s)⁻¹ at 2·200 Mc was observed. Assuming a galactic origin of the observed fluxes at both frequencies, the averaged sky brightnesses are b(0·700 Mc) = (6₋₃⁺⁵) × 10⁻²⁰ W m⁻² (c/s)⁻¹ sr⁻¹b(2·200 Mc) = (1.4^+1.0_−0.5 × 10⁻²⁰ W m⁻² (c/s)⁻¹ sr⁻¹ The observed brightness at 2·200 Mc is in reasonable agreement with the results of other observers. The apparent brightness at 0·700 Mc is, however, greater than was expected from previous observations. An alternative source of the 0·700 Mc flux in the terrestrial exosphere, as well as characteristics of several noise bursts observed during the flight, is briefly discussed.     

Power spectra of cosmic ray intensity variations at the ground and atmospheric pressure oscillations

Power spectrum estimates are computed for cosmic ray and pressure variations in the frequency range of 1.6 × 10⁻⁶ to 4.15 × 10⁻³ c/sec for three data sets each of 27 days length (2 min interval) recorded at Chacaltaya (Bolivia) during 1965–1966. The general trend of these spectra showy ƒ⁻ fit having exponent values from −1.5 to −1.9 for L.F. side. From the semi-diurnal peaks both in cosmic rays and pressure, the average value of pressure coefficient is found to be 0.3 per cent/mm of Hg. For the same three sets of data, a detailed analysis of cross-spectrum, coherence and phase relationship between cosmic rays and pressure is carried out in the frequency range of 1–12 c/day. Besides semi-diurnal peak, variations of 3, 4, 7 and 8 c/day are found to be common both in cosmic rays and pressure. The value of pressure coefficient and residual amplitude of cosmic rays for these particular frequencies are calculated.     

Excitation of the Aπu state of N by electrons

Absolute values of the emission cross sections for five vibrational bands in the Meinel system of N₂⁺,A²π_u to X²Σ_g⁺, excited by electron impact are presented. From these, a value was obtained for the total excitation cross section of the A²π_u state at 100 eV of 26·5 × 10⁻¹⁸ cm². The results are compared with those of other workers and with theory. Collisional transfer of the excitation energy from the levels of the A²π_u state was also observed with a transfer cross section of approximately 10⁻¹⁴ cm².     

The cosmic ray primary composition in the “knee” region through the EAS electromagnetic and muon measurements at EAS-TOP

The evolution of the cosmic ray primary composition in the energy range 10⁶–10⁷ GeV (i.e. the “knee” region) is studied by means of the e.m. and muon data of the Extensive Air Shower EAS-TOP array (Campo Imperatore, National Gran Sasso Laboratories). The measurement is performed through: (a) the correlated muon number (N_μ) and shower size (N_e) spectra, and (b) the evolution of the average muon numbers and their distributions as a function of the shower size. From analysis (a) the dominance of helium primaries at the knee, and therefore the possibility that the knee itself is due to a break in their energy spectrum (at E_k^He=(3.5±0.3)×10⁶ GeV) are deduced. Concerning analysis (b), the measurement accuracies allow the classification in terms of three mass groups: light (p,He), intermediate (CNO), and heavy (Fe). At primary energies E₀≈10⁶ GeV the results are consistent with the extrapolations of the data from direct experiments. In the knee region the obtained evolution of the energy spectra leads to: (i) an average steep spectrum of the light mass group (γ_p,He>3.1), (ii) a spectrum of the intermediate mass group harder than the one of the light component (γ_CNO2.75, possibly bending at E_k^CNO≈(6–7)×10⁶ GeV), (iii) a constant slope for the spectrum of the heavy primaries (γ_Fe2.3–2.7) consistent with the direct measurements. In the investigated energy range, the average primary mass increases from lnA=1.6–1.9 at E₀1.5×10⁶ GeV to lnA=2.8–3.1 at E₀1.5×10⁷ GeV. The result supports the standard acceleration and propagation models of galactic cosmic rays that predict rigidity dependent cut-offs for the primary spectra of the different nuclei. The uncertainties connected to the hadronic interaction model (QGSJET in CORSIKA) used for the interpretation are discussed.     

Reflection and refraction of hydromagnetk waves at the magnetopause

Reflection and transmission coefficients of MHD waves are obtained at a stable, plane interface which separates two compressible, perfectly conducting media in relative motion to each other. The coefficients are evaluated for representative conditions of the quiettime, near-Earth magnetopause. The transmission coefficient averaged over a hemispherical distribution of incident waves is found to be 1–2 per cent. Yet the magnitude of the energy flux deposited into the magnetosphere in a day averaged over a hemispherical distribution of waves having amplitudes of say 2–3 gamma, is estimated to be of the order 10²² erg. Therefore the energy input of MHD waves must contribute significantly to the energy budget of the magnetosphere. The assumption that the boundary surface is a tangential discontinuity with no curvature limits the present theory to hydromagnetic frequencies higher than about 10⁻¹ Hz. The ion gyrofrequencies for the models assumed here lie above 2 × 10⁻¹ Hz. Therefore the present treatment applies to MHD waves near 10⁻¹ Hz.     

A discussion on the mass loss formulae for OH/IR stars

It is found that the mass loss rate derived from S₂₅/S₁₂ is generally greater than that from the OH flux. This suggests an increasing loss rate with time. It is found that the gas-to-dust ratio decreases during the evolution Of OH/IR stars. An empirical relation between the gas-to-dust ratio and the dust mass loss rate is derived, leading to a formula for calculating the total mass loss rate directly from the IRAS 60 μm flux. OH/IR stars with silicate emission have a larger range of mass loss ratio, from 10⁻⁷ to 10⁻⁵ M/yr; those with silicate absorption, a smaller range between 10⁻⁵ and 10⁻⁴ M/yr. So a large increase in the mass loss rate takes place during the emission phase.     

Flux limits on ultra high energy neutrinos with AMANDA-B10

Data taken during 1997 with the AMANDA-B10 detector are searched for a diffuse flux of neutrinos of all flavors with energies above 10¹⁶ eV. At these energies the Earth is opaque to neutrinos, and thus neutrino induced events are concentrated at the horizon. The background are large muon bundles from down-going atmospheric air shower events. No excess events above the background expectation are observed and a neutrino flux following E⁻², with an equal mix of all flavors, is limited to E²Φ(10¹⁵ eV < E < 3 × 10¹⁸ eV)  0.99 × 10⁻⁶ GeV cm⁻² s⁻¹ sr⁻¹ at 90% confidence level. This is the most restrictive experimental bound placed by any neutrino detector at these energies. Bounds to specific extraterrestrial neutrino flux predictions are also presented.     

Properties of the infrared dark cloud G79.2+0.38

The MSX infrared dark cloud G79.2+0.38 has been observed over a 11′×′ region simultaneously in the J=1-0 rotational transition lines of the ¹²CO and its isotopic molecules ¹³CO and ¹⁸CO. The dense molecular cores defined by the C¹⁸O line are found to be associated with the two high-extinction patches shown in the MSX A-band image. The two dense cores have the column density N (H₂) (5 – 12) × 10²² cm⁻² and the mean number density n (3 ± 1) × 10⁴ cm⁻³. Their sizes are 1.7 and 1.2 pc in ¹³CO(1-0) line, 1.2 and 0.6 pc in C¹⁸O(1-0) line, respectively. The masses of these cloud cores are estimated to be in the range from 2 × 10² to 2 × 10³ M. The profile of radial mean density of the cloud core can be described by the exponential function ¯n(p) p^{−0.34±0.02}. Compared with the cases of typical optical dark clouds, the abundances of the CO isotopic molecules ¹³CO and C¹⁸O in this MSX infrared dark cloud appear to be depleted by a factor of 4–11, but at present there is no evidence for any obvious variation of the relative abundance ratio X_13/18 between ¹³CO and C¹⁸O with the column density.     

Rapid periodic light variations of EM Cephei

In 1990 and 1992, using the 60 cm reflector of Beijing Observatory, we carried out photoelectric UBV observations of the Be star EM Cep and obtained 277 data sets. After combining the published minimum times over the years we made the O — C analysis and found an improved period of 0.806184 d or a single wave period of 0.403092d. Our analysis also showed a quickening tendency of the period at a rate dP/dt = −8.8514 × 10⁻¹⁰. The light curve is characterized by sharp minima and broad maxima. We found a detectable variation of the U — B colour index with the phase.     

A prediction for three neutrino masses and mixings and similarity between quark and lepton mixings

If neutrinos have mass, we give reasons for a possible pattern of three (squaed) mass eigenvalues: m₁² (2.8−5.8) (eV)², m₂² 0.01 (eV)², m₃² (1.5−1) × 10⁻⁴ (eV)². The flavor states ν_μ and ν_e are mixtures of the eigenstates with m₂ and m₃ with a significant mixing, corresponding to an effective mixing angle of about 0.45. The ν_τ is nearly the state with m₁; the other two effective mixing angles are about an order of magnitude smaller than 0.45. There is a marked similarity to mixing in the quark sector.     

A plasmon model for the knots of M 87

A plasmon model for the optical-radio knots of M87 is discussed with reference to their observed characteristics and physical conditions. The spectral evolution is investigated under the joint dissipation through expansion, Fermi acceleration and synchrotron radiation. A Fermi acceleration coefficient of 10⁻⁹ s⁻¹ was obtained, and it was also shown that a spectral break should occur at 5 × 10¹⁴Hz and that this frequency should vary very slowly in time, in agreement with observations.     

Analysis of the variation in inclination of Intercosmos 13 Rocket, 1975-22B

The orbit of Intercosmos 13 rocket (1975-22B) has been determined at 103 epochs between 30 April 1975 and 10 April 1980 from almost 7000 observations. One hundred and three values of inclination have been determined and corrections incoporated for the effects due to zonal harmonic, lunisolar and tesseral harmonic perturbations, precession, and solid Earth tides. The modified data have been analysed to yield values of the atmospheric rotation rate, Λ rev day⁻¹, viz. Λ = 0.94 ± 0.10 at an average height of 322 ± 6 km and Λ = 1.27 ± 0.02 at 288 km. Analysis of the inclination near 14th-order resonance has indicated lumped harmonic values 10^{9 1.0}_1.4 = − 76.13 ± 12.47, 10^{9 1,0}₁₄ = − 29.89 ± 32.64, 10^{9 −1.2}₁₄ = − 63.11 ± 15.44 10^{9 −1.2}₁₄ = − 32.52 ± 26.96, for inclination 82.952°.     

On the determination of the earth''s rotation using the McDonald lunar laser ranging data of 1971.6 – 1979.0

Using 1658 normal points of the McDonald lunar ranging data in the period 1971.6–1979.0, I calculated the Earth's rotation curve, and found an offset of −330 × 10⁻¹⁰ for UT₁ – UTC. The difference between the UT₁ values given by the lunar data and BIH is 3.6 ms. This difference and the standard error of single determinations increase with increasing interval length used in the data reduction. This is shown to be due to the neglect of the secular term in UT₁-UTC. It appears that an interval length of 2 days is suitable when calculating the Earth's rotation.