Effect of Coulomb collisions on time variations of the solar neutrino flux

We consider the processes that might suppress the time variations in the solar neutrino flux produced by the radial motion of the Earth through the neutrino interference pattern. We calculate these time variations and the extent to which they are suppressed by Coulomb collisions of the neutrino-emitting nuclei. This is done for both the 0.862-MeV ⁷Be neutrino line and the continuous neutrino spectrum, assuming a Gaussian energy response function of the neutrino detector. We find that the collisional decoherence averages out the time variations for neutrino masses A simple and clear physical picture of the time-dependent solar neutrino problem is presented and qualitative coherence criteria are discussed.     

Light scattering by anisotropic particles

The Stokes parameters of radiation scattered by anisotropic particles (cosmic dust grains or molecules) are calculated. The effective mechanisms of transformation of the linear polarization into the circular one by free-oriented anisotropic particles are proposed. The optical activity of the irregular-shaped particles is shown to be rather large even though they consist of isotropic inactive material.     

Planetary spectra for anisotropic scattering

We examine here some of the effects on planetary spectra that would be produced by departures from isotropic scattering. The phase function $\text{}\text{?}\text{gw(1 + a}\text{cos}\text{θ)}$ is the simplest departure to handle analytically and the only phase function, other than the isotropic one, that can be incorporated into a Chandrasekhar first approximation. This approach has the advantage of illustrating effects resulting from anisotropies while retaining the simplicity that yields analytic solutions.The curve of growth is the sine qua non of planetary spectroscopy. Our discussion emphasizes the difficulties and importance of ascertaining curves of growth as functions of observing geometry. A plea is made to observers to analyze their empirical curves of growth, whenever it seems feasible, in terms of coefficients of $\text{(1?}\text{}\text{?}\text{gw)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and $\text{(1?}\text{}\text{?}\text{gw)}$, which are the leading terms in radiative-transfer analysis.An algebraic solution to the two sets of anisotropic H functions is developed in the appendix. It is readily adaptable to programmable desk calculators and gives emergent intensities accurate to 0.3%, which is sufficient even for spectroscopic analysis.     

Radar scattering by anisotropic Langmuir turbulence

Radar scattering by anisotropic Langmuir turbulence generated by Type III electrons is discussed. It is shown that in the framework of this model effective echo cross sections, scattering altitudes, and bandwidths of echo profiles can be understood.     

Anisotropy and polarization of solar X-ray bursts

The effects of the Compton back-scattered X-ray flux from the photosphere on the directivity and polarization of flare X-rays between 15 keV and 150 keV are computed. The calculations are made with a thin target model for flares of De Jager-Kundu type with electrons spiralling downward around a vertical magnetic field and for an Isotropie source. The resulting polarization for an isotropic source is not higher than 4%. The resulting directivity of anisotropic sources is greatly reduced, particularly below 70 keV. The results of the statistical studies of the center-limb distribution of solar X-ray bursts are then compatible with the existing measures of polarization. The hypothesis for existence of De JagerKundu type flares is enforced.     

Inverse compton scattering in anisotropic synchrotron sources

Models of compact, high brightness temperature sources such as quasars and active galactic nuclei often predict substantial inverse-compton scattered flux to be produced at high frequencies. As these fluxes are not observed, it is necessary to assume that extreme relativistic and/or anisotropic effects dominate the source. The often used equations to include these effects however are derived with several simplifying assumptions, which may not always be consistent with the derived source parameters (for example, the assumption of no time dependence in a violently variable quasar may not be appropriate). We therefore present here an explicit derivation of the dependence of the rate of inverse compton scattering on anisotropies in the source, to emphasise the importance and number of assumptions required in the derivation.     

Circular polarization of solar bursts at 22 GHz

The circular polarization of complex solar bursts was measured at short microwaves (22 GHz, × 1.35 cm) with high sensitivity (0.03 s.f.u. r.m.s.) and high time resolution (5 ms). The polarization shows up as soon as an excess burst emission is measured. Two components are found in the time development of the degree of circular polarization: (1) a steady level, sometime changing smoothly with time; (2) superimposed faster polarization time structures, small compared to the basic steady degree of polarization, and often not clearly related to the burst flux time structures. The observed degrees may range from 10% to more than 85%.In memoriam (1942–1981).     

The clouds of Venus: An anisotropic scattering model

The phase function $\text{ω}\text{?}\text{(1 + a}\text{cos}\text{θ)}$ for anisotropic scattering is applied to a homogeneous atmospheric model to ascertain the effects of anisotropy on the near-infrared spectrum of Venus. L. D. G. Young's equivalent widths for the 820 Å CO₂ band are analyzed to derive allowed combinations of CO₂ specific abundance, continuum albedo, pressure, and degree of anisotropy. From these combinations, values are derived for the photon mean-free path and total optical thickness of the clouds. The Venera 10 measurement of the transmitted flux at 7200 Å is then used in conjunction with spherical albedo requirements to reduce the range of possible solutions to the equivalent-width analysis. Through the application of approximate similarity relations, the “true” (i.e., anisotropic) atmospheric parameters are derived from the isotropic values. For an assumed Mie scatterer with an average anisotropy factor of 〈cos θ〉 = 0.7, the results indicate a total optical thickness of about 55 with a single-scattering albedo of 0.9992 to 0.9995.     

Circular polarization by scattering from spheroidal dust grains

Large degrees of circular polarization at near-infrared wavelengths have been reported in the OMC1 star-forming region. This discovery, in combination with compelling evidence for the existence of non-spherical aligned grains in star formation regions, has prompted us to investigate scattering from spheroidal particles as a possible mechanism for the production of large circular polarization in reflection nebulae. We use a dipole calculation to model the small particle limit and a T -matrix code to treat arbitrarily sized particles. We find that size distributions of perfectly aligned spheroids, with only modest 2:1 axis ratios, are capable of producing circular polarization of up to 50 per cent when scattering unpolarized incident light. This is the case even for dielectric materials, such as 'astronomical silicate', as long as sufficient large particles are included in the size distribution. We consider the effects of particle alignment and find that spinning oblate spheroids should be much more efficient circular polarizers than equivalent prolate spheroids.     

New measurements of the polarization of X-ray solar flares

Measurements of three X-ray flares in October/November 1970 abord the Intercosmos 4 satellite confirm the existence of polarization in the initial phase of the X-ray bursts. The polarization can be observed for a few up to ten minutes, and an increase in polarization is observed during secondary maxima of the bursts as well.     

Power spectra of CMB polarization by scattering in clusters

Mapping cosmic microwave background (CMB) polarization is an essential ingredient of current cosmological research. Particularly challenging is the measurement of an extremely weak B-mode polarization that can potentially yield unique insight on inflation. Achieving this objective requires very precise measurements of the secondary polarization components on both large and small angular scales. Scattering of the CMB in galaxy clusters induces several polarization effects whose measurements can probe cluster properties. Perhaps more important are levels of the statistical polarization signals from the population of clusters. Power spectra of five of these polarization components are calculated and compared with the primary polarization spectra. These spectra peak at multipoles  ℓ≥ 3000  , and attain levels that are unlikely to appreciably contaminate the primordial polarization signals.     

Removing instrumental polarization from infrared solar polarimetric observations

Full Stokes polarimetry is obtained using the National Solar Observatory Vacuum Tower Telescope at Sacramento Peak while observing the magnetically sensitive infrared Fei line at wavelength of 1.56. A technique is described which makes use of the high magnetic resolution in this spectral range to remove instrumental polarization from observed StokesQ, U, andV line profiles.Supported under a USAF/AFOSR research initiative.Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.     

Further polarization measurements of the solar flare X-ray emission

An improved X-ray polarimeter is briefly described and preliminary results of the measurements carried out on the satellite Intercosmos-7 are presented. One flare with considerable polarization (P 16%) was observed on 1972 August 4. Two other flares with rather low polarization (P 4%; P 2%) were observed on 1972 August 7 and 11.     

Inversion of Zeeman polarization for solar magnetic field diagnostics

The topic of magnetic field diagnostics with the Zeeman effect is currently vividly discussed. There are some testable inversion codes available to the spectropolarimetry community and their application allowed for a better understanding of the magnetism of the solar atmosphere. In this context, we propose an inversion technique associated with a new numerical code. The inversion procedure is promising and particularly successful for interpreting the Stokes profiles in quick and sufficiently precise way. In our inversion, we fit a part of each Stokes profile around a target wavelength, and then determine the magnetic field as a function of the wavelength which is equivalent to get the magnetic field as a function of the height of line formation.To test the performance of the new numerical code, we employed “hare and hound” approach by comparing an exact solution (called input) with the solution obtained by the code (called output). The precision of the code is also checked by comparing our results to the ones obtained with the HAO MERLIN code. The inversion code has been applied to synthetic Stokes profiles of the Na D₁ line available in the literature. We investigated the limitations in recovering the input field in case of noisy data. As an application, we applied our inversion code to the polarization profiles of the Fe i λ 6302.5 Å observed at IRSOL in Locarno.     

On the polarization of the solar coronal emission lines

The results of the spectrophotometrical measurements of the polarization in the coronal lines Fe xiv 5303 Å and Fe × 6374 Å are given. Polarization spectrograms were obtained by two spectrographs (prism and echelle types) during the solar eclipse in Mexico on 7 March, 1970 near the region of the second contact at the heights 0.06 to 0.12 R above the limb. The polarization in the green line is about 30% (for averaged height 1.08 R ). The polarization in the red line is close to the errors of the measurement and does not exceed 6%. A brief discussion of the results is also given.     

On the influence of resonant scattering on cosmic microwave background polarization anisotropies

We implement the theory of resonant scattering in the context of cosmic microwave background (CMB) polarization anisotropies. We compute the changes in the E-mode polarization (EE) and temperature E-mode (TE) CMB power spectra introduced by the scattering on a resonant transition with a given optical depth τ_X and polarization coefficient E ₁. The latter parameter, accounting for how anisotropic the scattering is, depends on the exchange of angular momentum in the transition, enabling observational discrimination between different resonances. We use this formalism in two different scenarios: cosmological recombination and cosmological re-ionization. In the context of cosmological recombination, we compute predictions in frequency and multipole space for the change in the TE and EE power spectra introduced by scattering on the Hα and Pα lines of hydrogen. This constitutes a fundamental test of the standard model of recombination, and the sensitivity it requires is comparable to that needed in measuring the primordial CMB B-mode polarization component. In the context of re-ionization, we study the scattering off metals and ions produced by the first stars, and find that polarization anisotropies, apart from providing a consistency test for intensity measurements, give some insight on how re-ionization evolved. Since polarization anisotropies have memory of how anisotropic the line scattering is, they should be able to discern the O  i 63.2-μm transition from other possible transitions associated to O  iii , N  ii , N  iii , etc. The amplitude of these signals are, however, between 10 and 100 times below the (already challenging) level of CMB B-mode polarization anisotropies.     

Photometric intensity and polarization measurements of the solar corona

During the 7 March, 1970, total eclipse of the Sun, the NASA Langley Research Center's Satellite Photometric Observatory (SPO) was used to measure the solar corona from Miahuatlan, Mexico. The SPO is equipped with a 24-inch Cassegrainian telescope, a four-channel photoelectric photometer, a Wollaston prism, and a rotating half-wave plate. Simultaneous measurements were made of the two orthogonal components of coronal light in the B and R bands of the UBVRI system. A 1-minute arc aperture was scanned from the lunar disk center out to five solar radii in a series of spirals of gradually increasing radius. For the first time, simultaneous multicolor intensity, degree, and angle of polarization profiles are computed from photoelectric measurements. Comparison of the variations of the measurements for each spiral scan yield a detailed picture of the intensity and polarization features in the K corona.     

Radiation transfer through atmospheric aerosol media with anisotropic scattering

Radiation transfer in atmospheric aerosol media with general boundary conditions has been studied for anisotropic scattering. The considered aerosol medium assumed to have specular and diffused reflecting boundary surfaces and in the presence of internal source. The radiation transfer scattering parameters as single scattering albedo, asymmetry factor, scattering, absorption, extinction efficiencies and anisotropic scattering coefficient have been calculated using the Mie theory. The problem with general boundary conditions is solved in terms of the solution of source-free problem with simply boundary conditions. Pomraning-Eddington approximation is used to solve the source-free problem. For the sake of comparison, a weight function is introduced and used in two special forms. The calculated partial heat fluxes with the two methods are compared and showed good agreement. Some of our results are found in a good agreement with published data.