A MC approach to simulate up- and down-going neutrino showers including local topographic conditions

The extragalactic flux of protons is predicted to be suppressed above the famous Greisen–Zatsepin–Kuzmin cut-off at about E_GZK  50 EeV due to the resonant photo-pion production with the cosmic microwave background. Current cosmic ray data do not give a conclusive confirmation of the GZK cut-off and the quest about the origin and the chemical composition of the highest energy cosmic rays is still open. Amongst other particles neutrinos are expected to add to the composition of the cosmic radiation at highest energies. We present an approach to simulate neutrino induced air showers by a full Monte Carlo simulation chain. Starting with neutrinos at the top of the atmosphere, the performed simulations take into account the details of the neutrino propagation inside the Earth and atmosphere as well as inside the surrounding mountains. The products of the interactions are input for air shower simulations. The mountains are modelled by means of a digital elevation map. To exemplify the potential and features of the developed tools we study the possibility to detect neutrino induced extensive air showers with the fluorescence detector set-up of the Pierre Auger Observatory. Both, down-going neutrinos and up-going neutrinos are simulated and their rates are determined. To evaluate the sensitivity, as a function of the incoming direction, the aperture, the acceptance and the total observable event rates are calculated for the Waxman–Bahcall (WB) bound.     

A geometric method to determine the distances of galaxies

Es wird die Möglichkeit diskutiert, die Größenverteilungsfunktion von Kugelsternhaufen für die Entfernungsbestimmung von Galaxien zu nutzen.     

Planetary close encounters: geometry of approach and post-encounter orbital parameters

Öpik's assumptions on the geometry of particle trajectories leading to and through planetary close encounters are used to compute the distribution of changes in heliocentric orbital elements that result from such encounters for a range of initial heliocentric orbits. Behaviour at encounter is assumed to follow two-body (particle—planet) gravitational scattering, while before and after encounter particle motion is only governed by the force of the Sun. Derivation of these distributions allows precise analysis of the probability of various outcomes in terms of the physical characteristics of the bodies involved. For example, they allow an explanation and prediction of the asymmetry of the extreme energy perturbations for different initial orbits. The formulae derived here may be applied to problems including the original accumulation of planets and satellites, and the continuing evolution of populations of small bodies, such as asteroids and comets.     

A sheet-current approach to coronal-interplanetary modeling

The most pertinent effect of the currents in the coronal-interplanetary space is their alteration of the magnetic topology to form configurations of open field lines. The important currents seem to be those in the neighborhoods of the interfaces between closed and open field lines or between oppositely directed open field lines in the coronal helmet-streamer structures. Thus, the coronal-interplanetary space may be regarded as being partitioned by current-sheets into several piecewise current-free regions. These current sheets overlie the photospheric neutral lines, where the vertical component of the magnetic field reverses its polarity on the solar surface. But, their locations and strengths are determined by force balance between the magnetic field and the gas pressure in the coronal-interplanetary space. Since the pressure depends on the flow velocity of the solar wind and the solar wind channels along magnetic flux tubes, there is a strong magnetohydrodynamic coupling between the magnetic field and the solar wind. The sheetcurrent approach presented in this paper seems to be a reasonable way to account for this complicated interaction.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

A realistic approach to magnetic evolution

An improved scheme for measuring and analyzing the magnetic field of flares is presented in general outline form. The techniques employed during the last solar cycle are reviewed very briefly. The point is made that those techniques were inadequate due to fundamental limitations in the data. A realistic scheme for acquiring the necessary data is then proposed. The scheme is realistic in that it makes only those assumptions which appear to be indeed valid, and it presupposes only instrumental techniques which are presently available. It is suggested that, with this improved data, the structure and evolution of the pre-flare magnetic field can be calculated with sufficient accuracy to form the basis of theoretical models.This research supported by Company funds of The Aerospace Corporation.     

A special perturbation method in orbital dynamics

The special perturbation method considered in this paper combines simplicity of computer implementation, speed and precision, and can propagate the orbit of any material particle. The paper describes the evolution of some orbital elements based in Euler parameters, which are constants in the unperturbed problem, but which evolve in the time scale imposed by the perturbation. The variation of parameters technique is used to develop expressions for the derivatives of seven elements for the general case, which includes any type of perturbation. These basic differential equations are slightly modified by introducing one additional equation for the time, reaching a total order of eight. The method was developed in the Grupo de Dinámica de Tethers (GDT) of the UPM, as a tool for dynamic simulations of tethers. However, it can be used in any other field and with any kind of orbit and perturbation. It is free of singularities related to small inclination and/or eccentricity. The use of Euler parameters makes it robust. The perturbation forces are handled in a very simple way: the method requires their components in the orbital frame or in an inertial frame. A comparison with other schemes is performed in the paper to show the good performance of the method.     

A method to determine regional lunar gravity fields from earth-based satellite tracking data

A method to determine regional gravity fields of the Moon from Earth-based Doppler and range satellite tracking data residuals of a low Moon-orbiting satellite has been developed and thoroughly tested in a controlled simulation environment. A short-arc approach, where one arc consists of the time it takes the satellite to cross the grid of interest on the lunar surface, is used in order to filter out most long-wavelength signal that can still be present in the residuals. Simulation results where the data are contaminated with either typical systematic or stochastic noise show that recovery of the local gravity field down to the level of several mGal is possible. The inclusion of extremely low-altitude data also means that regularisation in the sense of including a priori information in the form of a regularisation matrix is not necessary in order to obtain a good solution at high resolution.     

A semi-analytical approach to time-dependent coronal expansion

In this paper we point out the existence of a special class of solutions to the nonlinear hydrodynamic equations describing the time-dependent solar wind, namely that for which the velocity profile is time-invariant but the density at each point of the corona changes exponentially with time. Theoretical velocity curves are calculated for the case of isothermal expansion and compared with the Parker model for steady-state expansion. These solutions can be used to obtain quantitative estimates for the degree of departure from the latter of a real corona undergoing evolution on a finite time scale.On leave from Los Alamos Scientific Laboratory, Los Alamos, N.M., U.S.A.     

GLISSE: A GPU-optimized planetary system integrator with application to orbital stability calculations.

We present a GPU-accelerated numerical integrator specifically optimized for stability calculations of small bodies in planetary systems. Specifically, the integrator is designed for cases when large numbers of test particles (tens or hundreds of thousands) need to be followed for long durations (millions of orbits) to assess the orbital stability of their initially “close-encounter free” orbits. The GLISSE (Gpu Long-term Integrator for Solar System Evolution) code implements several optimizations to achieve a roughly factor of 100 speed increase over running the same code on a CPU. We explain how various hardware speed bottlenecks can be avoided by the careful code design, although some of the choices restrict the usage to specific types of application.As a first application, we study the long-term stability of small bodies initially on orbits between Uranus and Neptune. We map out in detail the small portion of the phase space in which small bodies can survive for 4.5 billion years of evolution; the ability to integrate large numbers of particles allow us to identify for the first time how instability-inducing mean-motion resonance overlaps sharply define the stable regions. As a second application, we map the boundaries of 4 Gyr stability for transneptunian objects in the 5:2 and 3:1 mean-motion resonances, demonstrating that long-term perturbations remove the initially stable Neptune-crossing members.     

A revised orbital ephemeris for HAT-P-9b

We present here three transit observations of HAT-P-9b taken on 14 February 2010 and 05 April 2010 UT from the University of Arizona’s 1.55 m Kuiper telescope on Mt. Bigelow. Our two light curves were obtained in the Arizona-I filter for all our observations, and underwent the same reduction process. Both transits occurred approximately 24 min earlier than expected from the ephemeris of Shporer et al. (2009). However, due to the large time span between our observed transits and those of Shporer et al. (2009), a 6.5 s shift downwards in orbital period from the value of Shporer et al. (2009) is sufficient to explain all available transit data. We find a new period of 3.922814 ± 0.000002 days for HAT-P-9b, an order of magnitude more precise than previous measurements, with no evidence for significant nonlinearities in the transit period.     

A simple procedure to extend the Gauss method of determining orbital parameters from three to N points

A simple procedure is developed to determine orbital elements of an object orbiting in a central force field which contribute more than three independent celestial positions. By manipulation of formal three point Gauss method of orbit determination, an initial set of heliocentric state vectors r _i and $\dot{\mathbf{r}}_{i}$ is calculated. Then using the fact that the object follows the path that keep the constants of motion unchanged, I derive conserved quantities by applying simple linear regression method on state vectors r _i and $\dot{\mathbf{r}}_{i}$ . The best orbital plane is fixed by applying an iterative procedure which minimize the variation in magnitude of angular momentum of the orbit. Same procedure is used to fix shape and orientation of the orbit in the plane by minimizing variation in total energy and Laplace Runge Lenz vector. The method is tested using simulated data for a hypothetical planet rotating around the sun.     

A method to determine the atmospheric temperature profile from in situ pressure data: Application to Titan

We have developed a new method to analyse in situ observations of atmospheric variables of state: the reconstruction of the vertical temperature profile from pressure measurements accompanied by rough knowledge of the atmospheric composition and the aerodynamical response properties of the descent vehicle. We can use the method to construct the temperature profile when no direct measurements are available, as well as to analyse the consistency between data from different instruments. We applied the method to the Huygens measurements of Titan's atmosphere, determining the aerodynamical drag properties from radar altimeter data. We discovered that the temperature profile computed in this manner differs from the profile from the temperature sensor (TEM) of the probe by up to 5% in the altitude range of 0–60 km, and up to 10% at higher altitudes due to increased noise. The method gives a tropopause altitude of about 50 km and a surface temperature of about 98 K, in contrast to the TEM temperature measurements. Our error analysis shows that these differences are caused by the known discrepancy in the Huygens altimeter data, with the estimates made by the reconstruction algorithm contributing only 1–2% of error.     

A new analytic approach to the Sitnikov problem

A new analytic approach to the solution of the Sitnikov Problem is introduced. It is valid for bounded small amplitude solutions (z _max = 0.20) (in dimensionless variables) and eccentricities of the primary bodies in the interval (–0.4 < e < 0.4). First solutions are searched for the limiting case of very small amplitudes for which it is possible to linearize the problem. The solution for this linear equation with a time dependent periodic coefficient is written up to the third order in the primaries eccentricity. After that the lowest order nonlinear amplitude contribution (being of order z ³) is dealt with as perturbation to the linear solution. We first introduce a transformation which reduces the linear part to a harmonic oscillator type equation. Then two near integrals for the nonlinear problem are derived in action angle notation and an analytic expression for the solution z(t) is derived from them. The so found analytic solution is compared to results obtained from numeric integration of the exact equation of motion and is found to be in very good agreement. CERN SL/AP     

A non imaging approach to solar oblateness measurements

A design is presented for an instrument to measure solar oblateness without forming a solar image and having two identical prisms as the only optical elements. Feasibility calculations indicate that this might be sensitive and quite free from instrumental induced errors.