Spectrum of the relic neutrino background from past supernovae and cosmological models

It is greatly expected that the relic neutrino background from past supernovae will be detected by Superkamiokande (SK) which is now under construction. We calculate the spectrum and the event rate at SK systematically by using the results of simulations of a supernova explosion and reasonable supernova rates. We also investigate the effect of a cosmological constant, Λ, on the spectrum, since some recent cosmological observations strongly suggest the existence of Λ. We find following results. (1) The spectrum has a peak at about 3 MeV, which is much lower than that of previous estimates (6–10 MeV). (2) The event rate at SK in the range from 10 MeV to 50 MeV, where the relic neutrinos from past supernovae are dominant, is about 25h₅₀²(R_SN/0.1 yr⁻¹)(n_Gh₅₀⁻³/0.02 Mpc⁻³) events per year, where R_SN is the supernova rate in a galaxy, n_G is the number density of galaxies, and h₅₀ = H₀/(50 km/s Mpc), where H₀ is the Hubble constant. (3) The event rate is almost insensitive to Λ. The flux increases in the low energy side (< 10 MeV) with increasing Λ, but decreases in the high energy side (> 10 MeV) in models in which the integrated number of supernovae in one galaxy is fixed.     

A study of F2 region night-time vertical ionization fluxes at millstone hill

Vertical fluxes of ionization in the F2 region have been measured by the incoherent scatter technique over Millstone Hill in 1969. The results obtained near midnight for the region above h_maxF2 have been examined to determine whether there is a significant flux of ionization from the magnetosphere to the ionosphere that serves to maintain the F-layer. It is found that H⁺ ions are a minor constituent over the altitude range in which useful measurements can be made, so that any conclusion must rest upon properly interpreting the observed O⁺ fluxes. By selecting periods when the layer did not appear to be decaying rapidly it was hoped to find cases where the O⁺ flux did not vary with altitude in the range 500 h 800 km (i.e. where losses are unimportant), since this would imply that the flux is of magnetospheric origin.

While three cases exhibited this behaviour, the majority exhibited a decrease in the O⁺ flux with height, indicating that the layer was descending. Attempts to correct for this were made, and the average flux from the magnetosphere was estimated as 3 × 10⁷ el/cm²/sec. This is in fair agreement with other recent estimates, and implies that at this latitude the ionosphere is not maintained solely by the magnetospheric flux. Moreover, large increases in flux that could give rise to nocturnal increases in the total content of the layer do not appear to have been seen.     

Auroral N2(c′4Σu → aΠg emission

Inspection of recent spectra presented by Sivjee (1983) show evidence of the 0–4 and 0–5 bands of the N₂(c′₄¹Σ_u⁺ → a¹Π_g) Gaydon-Herman system. In conjunction with earlier spectra, it is now possible that this band system is a significant auroral component, with an intensity approx. 7% that of the N2 2P system. The absence in aurorae of the potentially far stronger N₂(c′₄¹Σ_u⁺ → X¹Π_g) system is discussed. It is that the O₂(A³Σ_u⁺ → X³Σ_g⁻) band system is indiscernible in Sivjee's auroral spectra, under conditio the foreground nightglow is expected to be clearly visible. On the other hand, at least one relatively strong O₂(A′³Δ_u → a¹Δ_g) band appears to be present in these spectra.     

Effects of E-region electric fields on F-region parameters at the magnetic equator

The effects of E-region electric fields on F-region parameters like height of constant electron density contours (h_N) and semi-thickness, at an equatorial station, Trivandrum, are investigated. The E-region east-west electric field (E_y) has been deduced using the horizontal magnetic field values from the ground magnetograms. It is found that the semi-thickness parameter and h_N follow closely the E-region electric field (E_y) variations in the forenoon and noon periods. In the afternoon, it is shown that there is close association between h_N and E_y, when the electric field variations are large. On a day-to-day basis also, h_N and the E-region electric field show very good correlation in the forenoon and noon hours. It is also shown that higher levels are affected more than the lower levels in the F-region by E_y.     

Statistics of structure and rotation parameters of disk galaxies

Through an analysis of the optical and radio rotation curves of 57 galaxies, the following conclusions are drawn. 1) As we go from early-type to late-type along the Hubble sequence, dynamical quantities characterizing the structure and rotation show systematic variations. The bulge-to-disk mass-ratio decreases, the peak velocity V_m decreases, the period at the peak-velocity-point P_m increases, the peak-velocity-radius r_m shifts outward relative to the optical Holmberg radius r_H, the spiral arms become more loosely-wound and the galaxy flattens. 2) Within a given morphological type, the dispersion in each of the dynamical quantities is related to the mass, the more massive galaxies have larger V_m and r_m and small k (= V_m²/r_m) and β (= r_H/r_m.3) another important factor in influencing the dynamical state of a galaxy and, within a morphological type, the tidal galaxies have greater k and β and smaller r_m.     

A further study of the method of identifying absorption line systems in QSO spectra

The method of identifying absorption line systems in QSO spectra (Cui et al. 1983; Chen et al. 1983) is further developed here. Certain limitations of the method and their improvements are discussed. Certain other problems requiring further study are pointed out. The improved method is applied to PKS 0528-250, and gives two new absorption line systems Z_a = 0.065 and 0.0345 in addition to the four systems Z_a = 2.8110, 2.8130, 2.5275, 2.1410, consistent with the systems A₁A₂, B, C of Norton et al. (1980). However, the systems D₁, D₂, E, F and G of Chen and Norton (1984) are not recovered. The reason for this discrepancy is discussed.     

A measurement of the O2 ultra-violet nightglow emission

New measurements of the Herzberg I emission height profile in the night airglow are reported and indicate a peak emission height near 96 km in agreement with previous measurements. Using an atomic oxygen concentration profile determined from the oxygen green line profile measured on the same rocket it is concluded that the O₂(A³Σ_u⁺) state is not excited in the direct three body recombination of atomic oxygen. It is suggested that the excitation mechanism is a two step process, similar to the Barth mechanism for the atomic oxygen green lineand that the excited intermediate state is C³Δ_u.     

Charged boson stars and vacuum instabilities

We consider charged boson stars and study their effect on the structure of the vacuum. For very compact particle like “stars”, with constituent mass m_* close to the Planck mass m_Pl, i.e. m²_* = O(m²_Pl), we argue that there is electric charge Z_c, which, primarily, is due to the formation of a pion condensate (Z_c 0.5⁻¹e, where is the fine structure constant and e is the electric charge of the positron). If the charge of the “star” is larger than Z_c we find numerical evidence for a complete screening indicating a limiting charge for a very compact object. There is also a less efficient competing charge screening mechanism due to spontaneous electron-positron pair creation in which case Z_c ⁻¹e. Astrophysical and cosmological abundances of charged compact boson stars are briefly discussed in terms of dark matter.     

Cyclotron amplification of geomagnetic micropulsations Pc1 in the magnetosphere

A numerical analysis of cyclotron instabilities is carried out by computing the dispersion relation for a three component cold plasma-beam system. Rates of growth and damping for various values of the stream density are calculated from the dispersion relation. The rates of growth and damping increase monotonically as the number density of the proton stream increases. It is found that the frequencies at the rates of maximum growth and the damping decrease slightly to lower frequencies and a sharp peak at these frequencies becomes blunt. The minimum e-folding times of an ion cyclotron wave for (a) σ_s = 10⁻⁴, σ_i = 10⁻² and (b) σ_s = 10⁻¹, σ_i = 10⁻² are about 3·84 and 0·16 sec respectively in the vicinity of the equatorial plane at 6 Re, where σ_s and σ_i are the ratios of the beam density N_s and the helium ion (H₆⁺) density N_i to the total positive ions in the plasma-beam system.     

Some aspects of Sporadic-E at mid-latitudes

Evidence is presented to suggest that the ƒ₀E_s value tends to be high at positions in the E_s-layer where trough slope-lines and crest slope-lines of F2-layer irregularities meet the E_s-layer. These slope-lines are drawn through the troughs and crests, respectively, of the characteristic kinks in the F2-layer ionization contours, which are associated with F2-layer irregularities.

A rotating-loop direction-finding system has allowed an estimation of the distribution of ionization, which gives rise to Sporadic-E echoes. Analysis of Sporadic-E occurrence, on two occasions, suggests that the reflecting surfaces are frontal in nature, the fronts having a separation from each other of some tens of kilometres, and probably existing as closed curves, with diameters of the order of several hundreds of kilometres. A possible association between these structures and the occurrence of the green line of the airglow, is discussed.

A distribution of ionization, which will give contours showing “clouds” of ionization at some frequencies and a ripple structure at other frequencies, is proposed, in an endeavour to explain the apparent dual nature of Sporadic-E occurrence.

The evidence seems to indicate that the mechanism operating at the E_s-layer level, producing the phenomenon of Sporadic-E, is the same as that which produces the F2-layer irregularities which are responsible for “Spread-F”.     

Ducted propagation of hydromagnetic waves in the upper ionosphere

This paper presents a theoretical investigation of the ducting of Pc1 hydromagnetic waves in an ionospheric layer situated above the F₂ region. Theoretical calculations show that this upper ionospheric duct may also sustain horizontal propagation of Pc1 pulsations over appreciable distances. It is found that there is a low-frequency cutoff as in the case of the F₂ layer waveguide. The group velocity of waves in the upper ionospheric duct is considerably greater, and dispersion is more pronounced compared to the ducted propagation in the F₂ region.     

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.     

Le guidage des whistlers par le champ magnetique

In this paper the question is examined of how the v.l.f. radio-waves are guided along the magnetic field. Energy passes through the magnetic field under two sets of conditions. Corresponding to the “nose-whistlers” explained by Helliwell, the first one occurs when the wave-normal itself is in the direction of the magnetic field. This does not happen in the second case when the remarkable property is also shown that all frequencies are propagated at the same velocity V₀ = cƒ_H/2ƒ₀ (ƒ_H gyrofrequency, ƒ₀ frequency of the plasma). Considerations of energy point out that, if such a propagation is not easily observable in the case of an isotropic emission, it is not the same thing for an emission produced by erenkov effect, which is able to produce all energy by this mode of propagation, provided the particle's velocity has a low fixed value (˜ 10,000 km/sec in the exosphere). All frequencies being emitted at the same time and following the same path wtih the same velocity, we can explain the broadband noise observed during the reception of whistlers. The required velocity of particles is exactly the velocity V₀. This coincidence is explained in an appendix, and extended to other anisotropic media.     

A numerical investigation of thermosphere-ionosphere interaction over Millstone Hill

The upper thermosphere and F-region ionosphere system at 43°N is modelled for equinox and moderate solar conditions via a series of iterative calculations employing a thermospheric wind model and a one-dimensional ionospheric model which are mutually coupled. Several feedback loops within the system involving F₂-layer peak height, F₂-layer peak density, zonal wind, meridional wind, and Coriolis force are investigated to better understand the interactive aspect of ionosphere-thermosphere coupling. The interplay of primary importance involves the night-time ascent/descent of the F-layer due to equatorward/poleward neutral winds, the resulting changes in ion drag presented to the meridional and zonal wind fields, and the Coriolis force modification of the ion drag coupling. Wind shear and plasma profile shape are not significantly coupled. For magnetically undisturbed conditions, self-consistent treatment of these effects modifies a non-interactive “control” calculation by 20–35 m s⁻¹ in the wind field. During geomagnetically disturbed periods interactive processes play a more crucial role in determining thermospheric and ionospheric storm responses. Our calculations reveal wind enhancements of up to 100 m s⁻¹ associated with the lifting and negative-phase depletion of the F-region for prolonged magnetic disturbance conditions, the former mechanism accounting for a major portion of the effect.     

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.     

Density profiles of dark matter halos with anisotropic velocity tensors

We present density profiles, that are solutions of the spherical Jeans equation, derived under the following two assumptions: (i) the coarse grained phase-density follows a power-law of radius, ρ/σ³ ∝ r⁻, and (ii) the velocity anisotropy parameter is given by the relation β_a(r)=β₁+2β₂ (r/r_*)/[1+(r/r_*)²] where β₁, β₂ are parameters and r_* equals twice the virial radius, r_vir, of the system. These assumptions are well motivated by the results of N-body simulations. Density profiles have increasing logarithmic slopes γ, defined by γ=−d ln ρ/d ln r. The values of γ at r=10^−2.5r_vir, a distance where the systems could be resolved by large N-body simulations, lie in the range 1.0–1.6. These inner values of γ increase for increasing β₁ and for increasing concentration of the system. On the other hand, slopes at r=r_vir lie in the range 2.42–3.82. A model density profile that fits well the results at radial distances between 10⁻³r_vir and r_vir and connects kinematic and structural characteristics of spherical systems is described.     

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.     

Variations in air density at heights near 200 km during 1967–1969, from the orbit of 1967-31A

Air density at a height of 180–200 km from July 1967 to September 1969 has been determined from analysis of the high eccentricity orbit of satellite 1967-31A. The data show good correlation between sudden density increase and geomagnetic disturbance. The increases for disturbances of equal strength are approximately 40% greater during night-time than daytime hours. The day-night influence is also observed in the changes in density with changes in the solar flux index, F₁₀. The 27-day density variation is predominant mainly during night-time, although the atmospheric response to F₁₀ variations is quite variable regardless of local time. A semi-annual variation of approx. 40% is observed. Also found is a 25% diurnal variation for heights near 170–180 km, which is in good agreement with the CIRA 1972 atmosphere.     

Spectroscopic orbits of eclipsing binaries: WX Cancri

We have determined for the first time a spectroscopic orbit for WX Cnc. The orbital elements are V₀ = +9.8 km/s, k₁ = 110.2 km/s, K₂ = 149.0 km/s, T_o = HJD 2446 480.0309. After combining with the published photometric results, we derive the the following absolute parameters: A = 6.32R, R₁ = 1.53R, R₂=1.18R, M₁ = 1.29 M, M₂ = 0.96M. The spectroscopic mass-ratio is q = 0.74.     

On the thermal regeneration rate for light gravitinos in the early Universe

We investigate the light gravitino regeneration rate in the early Universe in models based on N = 1 supergravity. Motivated by a recent claim by Fischler, we evaluate finite-temperature effects on the gravitino regeneration rate due to the hot primordial plasma for a wide range of the supersymmetry-breaking scale F. We find that the leading thermal corrections to the gravitino pole mass and to the Goldstino coupling are negligible for a wide range of temperatures, thereby justifying the extension of the equivalence theorem for the helicity-1/2 gravitino and Goldstino to a hot primordial plasma background. Utilizing the Braaten-Pisarski resummation method, and assuming that the other particles are close to thermal equilibrium, the helicity-1/2 gravitino regeneration rate is found to be insensitive to magnetic Debye screening and of order _s(T) log(1/_s(T))¦m_soft/ F ¦²T³(1_s(T) log(1/_s(T))T²/¦F ¦) up to a calculable, model-dependent O(1) numerical factor. We review the implications of this regeneration rate for supergravity cosmology, focusing in particular on scenarios for baryogenesis.