Urca processes in dense matter and neutron star cooling

Urca-processes were introduced into astrophysics by Gamow and Schoenberg in 1941. Neutrino cooling resulting from urca-processes plays an important role at the latest stages of evolution of massive stars. Recent work on neutrino emissivity of dense matter shows that neutrino cooling via urca-processes could determine the thermal evolution of young neutron stars and depends dramatically on the composition of the neutron star core. In particular, if a neutron star contains a central core in which the direct urca-process is operative, the cooling timescale shortens by many orders of magnitude.     

Determination of station positions and velocities from laser ranging observations to Ajisai,Starlette and Stella satellites

The positions and velocities of the four Satellite Laser Ranging (SLR) stations: Yarragadee (7090), Greenbelt (7105), Graz (7839) and Herstmonceux (7840) from 5-year (2001–2005) SLR data of low orbiting satellites (LEO): Ajisai, Starlette and Stella were determined. The orbits of these satellites were computed from the data provided by 20 SLR stations. All orbital computations were performed by means of NASA Goddard’s GEODYN-II program. The geocentric coordinates were transformed to the topocentric North–South, East–West and Vertical components in reference to ITRF2005. The influence of the number of normal points per orbital arc and the empirical acceleration coefficients on the quality of station coordinates was studied. To get standard deviation of the coordinates determination lower than 1 cm, the number of the normal points per site had to be greater than 50. The computed positions and velocities were compared to those derived from LAGEOS-1/LAGEOS-2 data. Three parameters were used for this comparison: station coordinates stability, differences from ITRF2005 positions and velocities. The stability of coordinates of LEO satellites is significantly worse (17.8 mm) than those of LAGEOS (7.6 mm), the better results are for Ajisai (15.4 mm) than for Starlette/Stella (20.4 mm). The difference in positions between the computed values and ITRF2005 were little bit worse for Starlette/Stella (6.6 mm) than for LAGEOS (4.6 mm), the results for Ajisai were five times worse (29.7 mm) probably due to center of mass correction of this satellite. The station velocities with some exceptions were on the same level (≈1 mm/year) for all satellites. The results presented in this work show that results from Starlette/Stella are better than those from Ajisai for station coordinates determination. We can applied the data from LEO satellites, especially Starlette and Stella for determination of the SLR station coordinates but with two times lower accuracy than when using LAGEOS data.     

Modeling Multifractality of the Solar Wind

The question of multifractality is of great importance because it allows us to investigate interplanetary hydromagnetic turbulence. The multifractal spectrum has been investigated with Voyager (magnetic field) data in the outer heliosphere and with Helios (plasma) data in the inner heliosphere. We use the Grassberger and Procaccia method that allows calculation of the generalized dimensions of the solar wind attractor in the phase space directly from the cleaned experimental signal. We analyze time series of plasma parameters of the low-speed streams of the solar wind measured in situ by Helios in the inner heliosphere. The resulting spectrum of dimensions shows a multifractal structure of the solar wind attractor. In order to quantify that multifractality, we use a simple analytical model of the dynamical system. Namely, we consider the generalized self-similar baker’s map with two parameters describing uniform compression and natural invariant measure on the attractor of the system. The action of this map exhibits stretching and folding properties leading to sensitive dependence on initial conditions. The obtained solar wind singularity spectrum is consistent with that for the multifractal measure on the weighted baker’s map.     

Effect of Thermal Treatment on CFRP Parts Before and After Adhesive Bonding

Numerous non-destructive techniques are being investigated for assuring quality of the adhesive bonds.The research presented here is focused on non-destructive assessment of carbon fibre reinforced polymer(CFRP)parts.The surface condition directly influences the performance of adhesive bonds.The structural joints should ensure safe usage of a structure.However,some modifications of the surface may lead to weak bond that cannot carry the desired load.This is why there is a search for methods of surface assessment before bonding.Moreover,reliable techniques are required to allow to verify the integrity of the adhesive bond after manufacturing or bonded repair.We focus on the laser induced fluorescence(LIF)method for assessing the surface state.The LIF is a noncontact measurement method.In the context of adhesive bond assessment the electromechanical impedance(EMI)method is studied.The EMI uses surface bonded piezoelectric sensors for excitation and sensing.The investigated samples were made of CFRP layers.The samples were treated at elevated temperatures.The influence of the thermal treatment was studied using LIF.The thermal treatment at 220℃could be clearly distinguishedrom the rest of the considered samples.The thermally treated plates were bonded to untreated plate and then they were measured with the EMI method to study the influence of the treatment on the adhesive bond.The changes of EMI spectra were significant for the treatment at 280 ℃ and for some thermally treated samples that were later contaminated with de-icing fluid.     

Physics of Electric Discharges in Atmospheric Gases: An Informal Introduction

A short account of the physics of electrical discharges in gases is given from the viewpoint of its historical evolution and application to planetary atmospheres. As such it serves as an introduction to the papers on particular aspects of electric discharges contained in this issue, in particular in the chapters on lightning and the discharges which in the last two decades have been observed to take place in Earth’s upper atmosphere. In addition to briefly reviewing the early history of gas discharge physics we discuss the main parameters affecting atmospheric discharges like collision frequency, mean free path and critical electric field strength. Any discharge current in the atmosphere is clearly carried only by electrons. Above the lower boundary of the mesosphere the electrons must be considered magnetized with the conductivity becoming a tensor. Moreover, the collisional mean free path in the upper atmosphere becomes relatively large which lowers the critical electric field there and more easily enables discharges than at lower altitudes. Finally we briefly mention the importance of such discharges as sources for wave emission.     

Emission mechanism for low-frequency radiation in the outer heliosphere

The question of how low-frequency radio emissions in the outer heliosphere might be generated is considered. It is argued that the free energy contained in an electron beam distribution is first transformed into electrostatic Langmuir waves. The nonlinear interactions of these waves which can produce electromagnetic waves are then treated in the semi-classical formalism. Comparison of the results of the discussed model with electromagnetic radiation coming from upstream of the Earth's bow shock shows that the model adequately explains the generation of plasma waves at planetary shocks. By analogy, this model can provide a quantitative explanation of intensity of radio emissions at 2 to 3 kHz detected by the Voyager plasma wave instrument in the outer heliosphere provided that the electron beams generating Langmuir waves exist also in the postshock plasma due to secondary shocks in the compressed solar wind beyond the termination shock. The field strength of Langmuir waves required to generate the second harmonic emissions are approximately of 100–200 V m^–1 for the primary and 50–100 V m^–1 for the secondary foreshocks. However, only in the secondary foreshock the expected density is consistent with the observed frequency.     

Estimation of the Love and Shida numbers: h2, l2 using SLR data for the low satellites

In this paper we present results for the global elastic parameters: Love number h₂ and Shida number l₂ derived from the analysis of Satellite Laser Ranging (SLR) data. SLR data for the two low satellites STELLA (H = 800 km) and STARLETTE (H = 810 km) observed during 2.5 years from January 3, 2005 until July 1, 2007 with 18 globally distributed ground stations were analyzed. The analysis was done separately for the two satellites. We do a sequential analysis and study the stability and convergence of the estimates as a function of length of the data set used.     

Updating the Local Model of the TEC during the Solar Eclipse on August 11, 1999

A total solar eclipse with the locations and times of the pass well-known in advance can be used to update the local model of the TEC for these particular circumstances. The observations using GPS receivers at the Warsaw and Borowiec stations and the ionosonde in Warsaw were analyzed in order to justify the results given by the IRI theoretical predictions. The IRI program with this updating creates a useful tool for preparation of the corrections for the process of network adjustment using the GPS technique and for navigation using single frequency receivers.     

Revisiting the Ariel Trough Work for HF Telecommunication Purposes

Muldrew [1] was the pioneer who reported the midlatitude electron density trough at the topside ionosphere. For about ten to fifteen years the trough, its morphology, dynamical behavior, relationship to the equatorial plasmapause, and physical and chemical processes which lead to the trough formation had been extensively investigated. Then, the work on the trough had been slowed down gradually. As the new space systems have become more vulnerable to space weather effects, a need for robust programs and a long track record in space environment sensing and modeling to produce new space environment models and products that would meet high-priority defense and commercial needs arises naturally. In this context, it is intended to go over the reported trough work dating back to the 1970s and some typical findings of later developments briefly. Most of the aspects of the trough studies have been repeated with new data for newer physical models. From this point of view, the Ariel 3 and Ariel 4 satellite trough results are chosen since the work on the Ariel trough had been very original and very extensive quantitatively and qualitatively in the 1970s. The results reviewed here are based on more than 1000 beautiful selected trough cases. Due to the good quality and quantity of the Ariel satellite data, equal coverage in space and time were maintained, which makes the trough results very important. This paper will end with some reference to the trough models, results that establish a link between the topside and the F2 region of the ionosphere. As one typical application, HF radiocommunication is chosen to be the point of interest. In practical applications of the HF radiocommunications any model that does not include the trough is not complete.     

Forecasting of the Total Electron Content at a Single Location

The autocovariance prediction method previously used for the forecast of VI derived ionospheric characteristics has been used for forecast of one of the most important ionospheric—the total electron content (TEC)—at single locations. Quiet and disturbed conditions at different European stations were studied in regard to clarify the forecasting capabilities of the method for determination of the TEC. The accuracies of the method achieved in dependence on the time range of the forecast are demonstrated.