Exchange and correlation interactions in electron-positron plasma

The effect of particle-particle interaction on the adiabatic index γ for an electron-positron plasma is considered. An improved method for numerically calculating the Hartree-Fock exchange integral is presented and its relativistic asymptotics is determined. An approximation formula is derived for the correlation part of the interaction in the low-density limit. This formula includes degeneracy and the positron component.     

Comparison between polar regions of Mars from HEND/Odyssey data

In this paper, we have analyzed neutron spectroscopy data gathered by the High Energy Neutron Detector (HEND) instrument onboard Mars Odyssey for comparison of polar regions. It is known that observation of the neutron albedo of Mars provides important information about the distribution of water-ice in subsurface layers and about peculiarities of the CO₂ seasonal cycle. It was found that there are large water-rich permafrost areas with contents of up to ∼50% water by mass fraction at both the north and south Mars polar regions. The water-ice layers at high northern latitudes are placed close to the surface, but in the south they are covered by a dry and relatively thick (10-20 cm) layer of soil. Analysis of temporal variations of neutron flux between summer and winter seasons allowed the estimation of the masses of the CO₂ deposits which seasonally condense at the polar regions. The total mass of the southern seasonal deposition was estimated as 6.3×¹⁰¹⁵ kg, which is larger than the total mass of the seasonal deposition at the north by 40-50%. These results are in good agreement with predictions from the NASA Ames Research Center General Circulation Model (GCM). But, the dynamics of the condensation and sublimation processes are not quite as consistent with these models: the peak accumulation of the condensed mass of CO₂ occurred 10-15 degrees of Ls later than is predicted by the GCM.     

Composition of brines in halite‐hosted fluid inclusions in the Upper Ordovician,Canning Basin,Western Australia: new data on seawater chemistry

Analyses of primary and early diagenetic fluid inclusions in the halite from the Late Ordovician Mallowa Salt, Canning Basin, Western Australia indicate a Ca‐rich composition and high concentration of parent brines in the basin which were close to sylvite and carnallite precipitation. The salt‐bearing series in the sampled interval was overheated up to 62 °C. The recorded differences in gas compositions result from the input of several gas sources including dispersed organic matter in the salt series and hydrocarbon deposits in the underlying rocks. The high concentration of the brines in fluid inclusions does not allow quantitative reconstruction of the chemical composition of Late Ordovician parent seawater. Using the information from Early Cambrian and Late Silurian basins as a proxy, however, the new data indicate that Late Ordovician seawater was undoubtedly Ca‐rich and, in comparison with modern seawater, had a similar K content, considerably lower Mg content (c. 30%), approximately three times the Ca content and one‐third the SO₄ content.     

Strong magnetic field in W75N OH maser flare

A flare of OH maser emission was discovered in W75N in 2000. Its location was determined with the Very Long Baseline Array (VLBA) to be within 110 au from one of the ultracompact H  ii regions, Very Large Array 2 (VLA2). The flare consisted of several maser spots. Four of the spots were found to form Zeeman pairs, all of them with a magnetic field strength of about 40 mG. This is the highest ever magnetic field strength found in OH masers, an order of magnitude higher than in typical OH masers. Three possible sources for the enhanced magnetic field are discussed: (i) the magnetic field of the exciting star dragged out by the stellar wind; (ii) the general interstellar field in the gas compressed by the magnetohydrodynamic shock; and (iii) the magnetic field of planets which orbit the exciting star and produce maser emission in gaseous envelopes.     

Non-Existence of New Meromorphic First Integrals in the Planar Three-Body Problem

We consider the planar three-body problem and prove that, apart from some exceptional cases, there is no additional first integral meromorphic with respect to positions, mutual distances and momenta.     

Observations of High Resolution Spectra of Comet Hale-Bopp (C/1995 O1) at the SAO of the RAS

We present the results of the preliminary study of the comet Hale-Bopp spectrum obtained April 17, 1997 by K. Churyumov and F. Mussayev with the help of the 1-meter Zeiss reflector and the echelle spectrometer (spectral resolutionλ/Δ λ ≈ 50000), CCD and the long slit, oriented along the radius-vector(“Sun-comet direction”). Energy distributions for three selected regions including the C₃, C₂ (0-0) and CN(Δ ν = 0) molecules emissions of the comet Hale-Bopp spectrum were built. The rotational lines of the CN(Δ ν = 0) band were identified. The nature of the high emission peak near λ 4020 Å in the C₃ band is discussed. The presence of the cometary continuum of the nonsolar origin is assumed.     

A possible presence of HeH+ in white dwarfs

The equivalent width calculations for the fundamental vibration rotation band lines of HeH⁺ have been carried out for a non-DA white dwarf model with an effective temperature of 12 000 K. BothP andR branch lines with rotational quantum numbersJ=3 to 18 were included in the calculations. A search for these lines in helium rich white dwarfs is suggested.     

Low-frequency electric field fluctuations excited by ring current protons

Energetic protons haying ring type distributions are shown to generate low-frequency electrostatic waves, propagating nearly transverse to the geomagnetic field lines, in the ring current region by exciting Mode 1 arid Mode 2 nonresonant instabilities and a resonant instability. Mode 1 nonresonant instability has frequencies around ~4 Hz with transverse wavelengths of ~(8–80) km, and it is likely to occur in the region L = (7–8). Mode 2 nonresonant instability can generate frequencies ~(850–1450) Hz with transverse wavelengths ~(2–20) km. The typical frequencies and transverse wavelengths associated with the resonant instability are (950–1250) Hz and (30–65) km. Both the Mode 2 nonresonant instability and the resonant instability can occur in the ring current region with L = (4–6). The low-frequency modes driven by energetic protons could attain maximum saturation electric field amplitude varying from 0.8 mV/m to 70 mV/m. It is suggested that the turbulence produced by the low-frequency modes may cause pitch angle scattering of ring current protons in the region outside the plasmapause resulting in the ring current decay.