Search for low energyν e,μ,τ andv e,μ,τ in coincidence with BATSE gamma ray bursts

A search for low energy neutrinos of all flavours in correlation with 553 ray bursts detected by BATSE aboard the Compton Observatory has been performed by the LSD (Liquid Scintillator Detector) neutrino telescope. No excess ofe,, orv _e,, candidate has been detected by LSD during the time interval in which BATSE detected the 90% of the photon flux for any of the GRBs analyzed. Upper limits on the neutrino fluxes are given in the paper.     

An examination of directional discontinuities and magnetic polarity changes around interplanetary sector boundaries usingE > 2 keV electrons

Past studies of interplanetary magnetic sector boundaries have been based on the assumption that one can determine the field polarities by comparing the field directions with those of the nominal Parker spiral angles. Previous investigators have found evidence for decreases of B, the magnitude of the magnetic fieldB, and increases of , the angle betweenB and the ecliptic plane, at sector boundaries. Others have argued that the characteristic thickness of sector boundaries exceeds that of tangential discontinuities, making sector boundaries a separate class of structures.We use a simple technique for inferring the polarities of interplanetary magnetic fields based on the assumption thatE > 2 keV electrons are always flowing along the magnetic field away from the Sun. Electron data from the UC Berkeley experiment on the ISEE-3 spacecraft are used to examine periods around several apparent sector boundaries in 1978 and 1979. We compare properties of (a) boundaries with field polarity changes and (b) large-angle ( > 60°) directional discontinuities with no field polarity changes. We find no significant differences between the sector boundaries and the directional discontinuities in terms of associated decreases in B or of values of . These results suggest no significant difference between sector boundaries and directional discontinuities other than the change in field polarities. Within limited statistics we find that about half the polarity changes would not have been identified using a requirement that > 90° and that half of the > 120° discontinuities would have been misidentified as polarity changes.     

Pulsar radio emission

A new version of the theory of pulsar radio emission is developed for the case of a coaxial rotator. It is based on the electric field that we established [G. S. Sahakian, Astrofizika, 37, 97 (1994)] for the radiation channel (the channel of open magnetic field lines) and on convenient approximations for the electron energy obtained in [G. S. Sahakian and É. S. Chubarian, Astrofizika, 37, 255 (1994)]. It is shown that, owing to the emission of photons of curvature radiation by particles, e e+_c', and photon annihilation, _c e⁺e^– in the lower part of the radiation channel, a special region (the magnetic funnel) is formed in which vigorous cascade multiplication of particles occurs. The height of the magnetic funnel is h 6R^0.2, where R is the radius of the neutron star and is its angular rotation rate. As a result of supersaturation of the plasma density in the magnetic funnel, a discharge occurs after each time intervalt5·10^–7–0.8B ₁₂ ^–1.4 R ₆ ^–0.2 , i.e., the longitudinal electric field disappears (B is the magnetic induction in the star). During the active radiative processes in the magnetic funnel, two main fluxes of particles with high ultrarelativistic energies are formed: an upward flux of electrons and a positron flux falling onto the star's magnetic cap. These fluxes are accompanied by narrow strips of positron and electron fluxes, respectively, of considerably lower energy, which are fairly powerful, coherent radio sources. The pulsar's radio luminosity is calculated to be L7.4·10^223.8 ₃₀ ³ R ₆ ^–2 erg/sec, where =BR 3/2 is the star's magnetic moment. Comparing this result with observations, we conclude that the magnetic moment and hence the mass of the neutron star evidently must be considerably smaller, on the average, for fast pulsars than for slow ones. It is shown that the magnetic moment of the neutron star can be determined from the intervals between micropulses in the pulse profiles. The problem of the origin of the macrostructure of the radio pulse is discussed.Translated from Astrofizika, Vol. 38, No. 1, pp. 141–185, January – March, 1995.     

Signatures of solar wind interaction with the nightside ionosphere of Venus

Plasma and field relationships observed across the nightside of Venus evidence a chaotic variety of interactions between the ionosphere and the combined effect of the solar wind and interplanetary magnetic field draped about the planet. Close examination of these data reveal within the chaos a number of repeatable signatures key to understanding fundamental field-plasma interactions. Observed from the Pioneer Venus Orbiter, (PVO), nightside conditions range from extensive, full-up ionospheres with little evidence of dynamic or energetic perturbations, to an almost full depletion, sometimes described as disappearing ionospheres. Between these extremes, the ionospheric structure is often irregular, sometimes exhibiting well-defined density troughs, at other times complex intervals of either abundant or minimal plasma concentration. Consistently, large B-fields (typically exceeding 5–10 nanoteslas) coincide with plasma decreases, whereas stable, abundant plasma distributions are associated with very low-level field. We examine hundreds of nightside orbits, identifying close correlations between regions of elevated magnetic fields featuring polarity reversals, and (a) exclusive low-frequency or distinctive broadband noise, or both, in the electric field data, (b) turbulent, superthermal behavior of the the ions and electrons. We review extensive studies of nightside fields to show that the correlations observed are consistent with theoretical arguments that the presence of strong magnetic fields within normal ionospheric heights indicates the intrusion of magnetosheath fields and plasma within such regions. We find abundant evidence that the ionosphere is frequently disrupted by such events, exhibiting a chaotic, auroral-like complexity appearing over a wide range of altitude and local time. We show that field-plasma disturbances, widely suggested to be similar to conditions in the Earth's auroral regions, are tightly linked to the electric field noise otherwise attributed to lightning. Owing to the coincidence inherent in this relationship, we suggest that natural, predictable plasma instabilities associated with the plasma gradients and current sheets evident within these events produce the E-field noise. The data relationships argue for a more detailed investigation of solar wind induced E-field noise mechanisms as the appropriate scientific procedure for invoking sources for the noise previously attributed to lightning. Consistent with these views, we note that independent analyses have offered alternative explanations of the noise as arising from ionospheric disturbances, that repeated searches for optical evidence of lightning have found no such evidence, and that no accepted theoretical work has yet surfaced to support the inference of lightning at Venus.     

Apsidal motion in the eclipsing binary system V 451 Ophiuchi

MulticolourWBVR photoelectric observations of the eclipsing binary V 451 Oph were carried out, and a highly accurate light curve was obtained. The angular velocity of the orbital rotation, =2.1 deg yr^–1, and the apsidal motion constantk ₂=0.0045 are given.     

Distribution of absolute energy of bright Be stars in pleiades

We present newly measured energy distributions from 3200–7500 Å of five late-type Be stars in Pleiades cluster for search of peculiarities of Be stars continuum energy distributions. Empirical effective temperatures of Be stars have been derived by comparing observed and computed fluxes in the visible region. The variation of the flux in the Balmer continuum region of Pleione (28 Tau) has been discussed.     

Ammonia photolysis and the greenhouse effect in the primordial atmosphere of the earth

Photochemical calculations indicate that in the prebiotic atmosphere of the Earth ammonia would have been irreversibly converted to N₂ in less than 40 years if the ammonia surface mixing ratio were ≤ 10^?4. However, if a continuous outgassing of ammonia were maintained, radiative equilibrium calculations indicate that a surface mixing ratio of ammonia of 10^?5 or greater would provide a sufficient greenhouse effect to keep the surface temperature above freezing. With a 10^?4 mixing ratio of ammonia, 60 to 70% of the present day solar luminosity would be adequate to maintain surface temperatures above freezing. A lower limit to the time constant for accumulation of an amount of nitrogen equivalent to the present day value is 10 my if the outgassing were such as to provide a continuous surface mixing ratio of ammonia ≥ 10^?5.     

The satellites of Neptune and the origin of Pluto

Pluto and the chaotic satellite system of Neptune may have originated from a single encounter of Neptune with a massive solar system body. A series of numerical experiments has been carried out to try to set limits on the circumstances of such an encounter. These experiments show that orbits very much like those of Pluto, Triton, and Nereid can result from a single close encounter of such a body with Neptune. The implied mass range and encounter velocities limit the source of the encountering body to a former trans-Neptunian planet in the 2- to 5-Earth-mass range.     

Thermodynamics of selected trace elements in the Jovian atmosphere

The thermochemistry of several hundred compounds of twelve selected trace elements (Ge, Se, Ga, As, Te, Pb, Sn, Cd, Sb, Tl, In, and Bi) has been investigated for solar composition material along a Jupiter adiabat. The results indicate that AsF₃, InBr, TlI, and SbS, in addition to CO, PH₃, GeH₄, AsH₃, H₂Se, HCl, HF, and H₃BO₃ proposed by Barshay and Lewis (1978), may be potential chemical tracers of atmospheric dynamics. The reported observations of GeH₄ is interpreted on the basis of new calculations as implying rapid vertical transport from levels where T ? 800°K. Upper limits are also set on the abundances of many gaseous compounds of the elements investigated.     

Spectroscopic observations of winds on Venus: I. Technique and data reduction

We present out methods of measurement and reduction of high-dispersion photographic spectra of Venus. Our preliminary results are consistent with slow direct or no rotation at the level we sample, and disagree strongly with a 4-day retrograde rotation. A serious systematic error, which affects much published work, is due to blending of solar lines in the sky with those reflected from the planet. This always tends to produce a spurious retrograde “rotation.” Only data obtained in a dark sky, or daytime observations from which the sky lines have been accurately subtracted, can be relied upon. All such data give low wind speeds.