Neutrinos in dense quark matter and cooling of compact stars

We discuss that observational constraints on neutrino cooling processes may restrict the spectrum of quark matter phases admissible for compact star interiors.Comment: 3 pages, contribution to International School of Nuclear Physics on "Neutrinos in Cosmology, in Astro-, Particle- and Nuclear Physics, Erice-Sicily, September 16-24, 200

Neutrino emissivities and bulk viscosity in neutral two-flavor quark matter

We study thermodynamic and transport properties for the isotropic color-spin-locking (iso-CSL) phase of two-flavor superconducting quark matter under compact star constraints within a NJL-type chiral quark model. Chiral symmetry breaking and the phase transition to superconducting quark matter leads to a density dependent change of quark masses, chemical potentials and diquark gap. A self-consistent treatment of these physical quantities influences on the microscopic calculations of transport properties. We present results for the iso-CSL direct URCA emissivities and bulk viscosities, which fulfill the constraints on quark matter derived from cooling and rotational evolution of compact stars. We compare our results with the phenomenologically successful, but yet heuristic 2SC+X phase. We show that the microscopically founded iso-CSL phase can replace the purely phenomenological 2SC+X phase in modern simulations of the cooling evolution for compact stars with color superconducting quark matter interior.Comment: 15 pages, 6 figures, references added, text improve

Forecast of Total Electron Content over Europe for disturbed ionospheric Conditions

A general picture of the occurrence of ionospheric storms as function of local time, season and location is known from numerous studies over the past 50 years. Nevertheless, it is not yet possible to say how the ionosphere will actually respond to a given space weather event because the measurements of the onset time, location of maximum perturbation, amplitude and type of storm (positive or negative) deviate much from the climatology. However, statistical analyses of numerous storm events observed in the Total Electron Content (TEC) since 1995 enable to estimate and predict a most probable upcoming perturbed TEC over Europe based on forecasts of geomagnetic activity. A first approach will be presented here. The forecast of perturbed TEC is part of the Forecast System Ionosphere build under the umbrella of the FP7 project AFFECTS∗ (Advanced Forecast For Ensuring Communication Through Space). It aims to help users mitigating the impact on communication system

Early Warning of ionospheric disturbances for GNSS users

Temporal and spatial gradients in the ionosphere can cause major threats on communication and navigation satellite systems, because the propagation of transionospheric radio signals is influenced by the ionospheric electron content. Space weather events are often the source of strong ionospheric disturbances. Forecasting ionospheric perturbations related to space weather events is therefore a crucial task being of special interest for GNSS users. The climatology of ionospheric storms seen in the Total Electron Content (TEC) over Europe as a response of the ionosphere towards Earth oriented space weather events is well known. It depends on season, elapsed time from event arrival, location and local time. However, the deviation of a single storm to the mean behavior can be large. A good correlation between strength of the ionospheric storm, i.e. the maximum deviation of the TEC to 27 day median, to solar wind or geomagnetic activity indices is hard to define. Hence forecasting TEC for disturbed conditions is a challenging task. However, the storm climatology and comprehensive correlation studies allow forecasting of the most probable TEC perturbation amplitude for the European region. GNSS users are in need of information about arriving threads due to space weather events as early as possible. Therefore, an Early Warning message for GNSS users has been developed at the DLR within the FP7-Project AFFECTS. It provides information about Earth endangering space weather events to interested GNSS users up to two days before their arrival. Additional information are now added by a second warning message distributed thirty minutes before arrival at Earth giving more specific information like exact arrival time, forecasts of geomagnetic indices, approximate TEC perturbation and range error for the European region. An overview on the Early Warning for GNSS user service provided by DLR is presented in this paper

Radiation hardness of diamond and silicon sensors compared

The radiation hardness of silicon charged particle sensors is compared with single crystal and polycrystalline diamond sensors, both experimentally and theoretically. It is shown that for Si- and C-sensors, the NIEL hypothesis, which states that the signal loss is proportional to the Non-Ionizing Energy Loss, is a good approximation to the present data. At incident proton and neutron energies well above 0.1 GeV the radiation damage is dominated by the inelastic cross section, while at non-relativistic energies the elastic cross section prevails. The smaller inelastic nucleon-Carbon cross section and the light nuclear fragments imply that at high energies diamond is an order of magnitude more radiation hard than silicon, while at energies below 0.1 GeV the difference becomes significantly smaller.Comment: 6 pages, 4 figurs, invited talk at the Hasselt Diamond Workshop, Feb. 200

Transionospheric Microwave Propagation: Higher-Order Effects up to 100 GHz

Ionospheric refraction is considered as one of the major accuracy limiting factors in microwave space-based geodetic techniques such as the Global Positioning System (GPS), Satellite Laser Ranging (SLR), very-long-baseline interferometry (VLBI), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and satellite altimetry. Similarly, a high-performance ground-to-space and space-to-ground microwave link is considered to be very important for synchronizing clocks in global networks. Moreover, precise time and frequency transfer may lead to new applications in navigation, Earth observation, solar system science, and telecommunications. However, all transionospheric microwave signals are subject to ionospheric refraction and subsequent delays in the travel time. Since the ionosphere is a dispersive medium for radio signals, the first-order propagation effect can be removed by combining signals at two or more frequencies. Anyway, higher-order ionospheric effects remain uncorrected in such combinations. The residuals can significantly affect the accuracy of precise positioning, navigation, as well as the performance of time and frequency transfer. Here, we studied ionospheric propagation effects including higher-order terms for microwave signals up to 100 GHz frequencies. The possible combination between the L, S, C, X, Ku, and Ka band frequencies is studied for the first-order ionosphere-free solutions. We estimated the higher-order propagation effects such as the second- and third-order terms and ray-path bending effects in the dual-frequency group delay and phase advance computation. Moreover, the correction formulas originally developed for global navigation satellite systems (GNSS) L-band frequencies are tested for mitigating residual errors at higher frequencies up to 100 GHz