The N4,5 - OO Auger and “N3” N4,5O2,3 Coster-Kronig spectra of xenon induced by electron impact

The N_4,5OO Auger electron spectrum in the kinetic energy region (14–37) eV has been measured with high resolution at electron incident energies between 71 eV and 2019 eV. The Auger and satellite lines are assigned by comparison with previous literature data. Several states which correspond to the resonant Auger transitions from the 4d_{3/2, 5/2} 6p states are observed. The PCI effects on the N₅-O_2,3O_2,3(¹S₀) Auger peak when the incident electron energy approaches to the N₅ edge (67.55 eV) is investigated and it is found that the dependence of the energy shift on the excess energy, E_exc, is well represented by the function E_exc^β with β = (-1.40 ± 0.05). The ^“N₃^” N_4,5O_2,3 Coster-Kronig spectrum is measured at various electron incident energies. The assignments of the features are made in comparison with a similar spectrum from synchrotron radiation measured by Kivimäki et al. [J. Electron Spectrosc. Relat. Phenom. 1999, 101–103, 43–47]. The Auger spectrum in the kinetic energy regions (68–78) eV and (90–138) eV is observed for the first time in an electron impact experiment and a comparison is made with the photoionization experiment by Hikosaka et al. [Phys. Rev. A 2007, 76, 032708].     

Launch and commissioning of the PAMELA experiment on board the Resurs-DK1 satellite

PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons: 80 MeV–700 GeV, electrons 50 MeV–400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV–190 GeV), positrons (50 MeV–270 GeV) and search for antimatter (with a precision of the order of 10⁻⁸). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15th 2006 in a 350 × 600 km orbit with an inclination of 70°. The detector consists of a permanent magnet spectrometer core to provide rigidity and charge sign information, a Time-of-Flight system for velocity and charge information, a silicon–tungsten calorimeter and a neutron detector for lepton/hadron identification. An anticounter system is used off-line to reject false triggers coming from the satellite. In self-trigger mode the calorimeter, the neutron detector and a shower tail catcher are capable of an independent measure of the lepton (e⁺ + e⁻) component up to 2 TeV. In this work we focus on the first months of operations of the experiment during the commissioning phase.     

Observations of 1–30 MeV gamma rays from the galactic center

Preliminary results are reported for gamma ray observations of the galactic center region made during a 15 hour balloon flight from Alice Springs, Australia on April 18, 1979. The observations were carried out with the UCR double-scatter gamma-ray telescope at energies of 1 to 30 MeV. The observations are compatible with a galactic source of approximately equal brightness along the region 300°<ℓII<60°. The energy distribution joins smoothly to previous spark chamber results at energies above 30 MeV and to scintillator results below 1 MeV. It appears to be a combination of nuclear gamma ray lines superimposed on a bremsstrahlung spectrum with a power law (1.3±.7) × 10⁻³ E⁻(^1.7±.2). The ¹²C* line at 4.4 MeV appears to be present with a significance of about 16σ. The flux in the line is (6±3) × 10⁻⁴photons cm⁻²s⁻¹rad⁻¹. The oxygen line at 6.1 MeV does not seem to appear significantly above background.     

Mercury Ion Analyzer (MIA) onboard Mercury Magnetospheric Orbiter: MMO

The Mercury Magnetopsheric Orbiter (MMO) is one of the spacecraft of the BepiColombo mission; the mission is scheduled for launch in 2014 and plans to revisit Mercury with modern instrumentation. MMO is to elucidate the detailed plasma structure and dynamics around Mercury, one of the least-explored planets in our solar system. The Mercury Plasma Particle Experiment (MPPE) on board MMO is a comprehensive instrument package for plasma, high-energy particle, and energetic neutral particle atom measurements. The Mercury Ion Analyzer (MIA) is one of the plasma instruments of MPPE, and measures the three dimensional velocity distribution of low-energy ions (from 5 eV to 30 keV) by using a top-hat electrostatic analyzer for half a spin period (2 s). By combining both the mechanical and electrical sensitivity controls, MIA has a wide dynamic range of count rates for the proton flux expected around Mercury, which ranges from 10⁶ to 10¹² cm⁻² s⁻¹ str⁻¹ keV⁻¹, in the solar wind between 0.3 and 0.47 AU from the sun, and in both the hot and cold plasma sheet of Mercury’s magnetosphere. The geometrical factor of MIA is variable, ranging from 1.0 × 10⁻⁷ cm² str keV/keV for large fluxes of solar wind ions to 4.7 × 10⁻⁴ cm² str keV/keV for small fluxes of magnetospheric ions. The entrance grid used for the mechanical sensitivity control of incident ions also work to significantly reduce the contamination of solar UV radiation, whose intensity is about 10 times larger than that around Earth’s orbit.     

Rapid variability of 10–140 keV X-rays from Cygnus X-1

On five occasions in 1977 and 1978, Cygnus X-1 was observed using the Low-Energy Detectors of the UCSD/MIT Hard X-Ray and Low-Energy Gamma-Ray Experiment on the HEAO-1 satellite. Rapid (0.08 s ≤ t ≤ 1000 s) variability was found in the 10 – 140 keV band. The power spectrum was “white” for 10⁻³ Hz < f ≤ 5 × 10⁻² Hz and was proportional to f⁻¹ for 5 × 10⁻² Hz ≤ f < 3 Hz, indicating correlations on all time scales < 20 s. If the emission is produced by Comptonization of a soft photon flux in a hot cloud, the heating of the cloud cannot be constant; it must vary on time scales up to 20 seconds. A variable accretion rate could cause the observed effects.     

High-energy neutrinos from powerful radio galaxies

In order to explore mechanisms for the production of radio lobes from radio galaxies, we propose observational tests involving neutrinos at E ≥ 4 TeV. Among the mechanisms that have been suggested are: an explosive burst of energy that has been stored in or near the galactic nucleus; diffusive escape of particles from the vicinity of the galactic nucleus into plasmons; a beam from the galactic core that interacts with the circumgalactic medium; and black holes or spinars ejected from the galactic nucleus by a gravitational slingshot mechanism. As an example, we estimate neutrino fluxes from Cen A. The annual neutrino event rate at energies above 4 TeV is ≈ 10²–10³ for a DUMAND-type dectector if relativistic particles are temporarily stored near the galactic nucleus, and if these have a differential energy spectrum with exponent –2.0. With a similar exponent, but allowing free escape from the galaxy, the fluxes are about 10 times lower.     

Asymmetric precipitation in a coronal loop as explanation of a singular observed spectrum

Almost 10 years of solar submillimeter observations have shown new aspects of solar activity, such as the presence of rapid solar spikes associated with the launch of coronal mass ejections and an increasing submillimeter spectral component in flares. We analyse the singular microwave–submillimeter spectrum of an M class solar flare on 20 December, 2002. Flux density observations measured by Sun patrol telescopes and the Solar Submillimeter Telescope are used to build the radio spectrum, which is fitted using Ramaty’s code. At submillimeter frequencies the spectrum shows a component different from the microwave classical burst. The fitting is achieved proposing two homogeneous sources of emission. This theoretical fitting is in agreement with differential precipitation through a magnetically asymmetric loop or set of loops. From a coronal magnetic field model we infer an asymmetric magnetic structure at the flare location. The model proposed to quantify the differential precipitation rates due to the asymmetry results in a total precipitation ratio Q₂/Q₁≈10⁴–10⁵, where Q₁(Q₂) represents the total precipitation in the loop foot with the high (low) magnetic field intensity. This ratio agrees with the electron total number ratio of the two sources proposed to fit the radio spectrum.     

Direct dark matter searches with CDMS and XENON

The cryogenic dark matter search (CDMS) and XENON experiments aim to directly detect dark matter in the form of weakly interacting massive particles (WIMPs) via their elastic scattering on the target nuclei. The experiments use different techniques to suppress background event rates to the minimum, and at the same time, to achieve a high WIMP detection rate. The operation of cryogenic Ge and Si crystals of the CDMS-II experiment in the Soudan mine reported spectrum-weighted exposures of 34 (12) kg-d for the Ge (Si) targets after cuts, over the recoil energies 10–100 keV for a WIMP mass of 60 GeV/c². It gives an upper limit (90% C.L.) of spin-independent WIMP-nucleon cross-section at 1.6 × 10⁻⁴³ cm² for a WIMP mass of 60 GeV/c², starting to constrain predications in supersymmetry models. The two-phase xenon detector of the XENON10 experiment is currently taking data in the Gran Sasso underground lab and promising preliminary results were recently reported. Both experiments are expected to increase their WIMP sensitivity by a one order of magnitude in the scheduled science runs for 2007.     

Dark matter search with the CALET detector on-board ISS

The CALorimetric Electron Telescope, CALET, mission is proposed for the observation of high-energy electrons and gamma-rays at the Exposed Facility of the Japanese Experiment Module on the International Space Station. The CALET has a capability to observe the electrons (without separation between e⁺ and e⁻) in 1 GeV–10 TeV and the gamma-rays in 20 MeV–several TeV with a high-energy resolution of 2% at 100 GeV, a good angular resolution of 0.06 degree at 100 GeV, and a high proton-rejection power of nearly 10⁶. The CALET has a geometrical factor of 1 m²sr, and the observation period is expected for more than three years. The very precise measurement of electrons enables us to detect a distinctive feature in the energy spectrum caused from WIMP dark matter in the Galactic halo. The excellent energy resolution of CALET, which is much better than GLAST or air Cherenkov telescopes over 10 GeV, enables us to detect gamma-ray lines in the sub-TeV region from WIMP dark matter annihilations. The CALET has, therefore, a unique capability to search for WIMP dark matter by the hybrid observations of electrons and gamma-rays.     

Attempt to study Marangoni flow of low-Pr-number fluids using a liquid bridge of silver

In order to experimentally investigate the Marangoni flow of low-Prandtl-number fluids in a liquid bridge geometry under the condition of small Marangoni numbers close to the critical Marangoni numbers Ma_c1 and Ma_c2, the formation of a liquid bridge of silver was attempted. The available temperature difference between the upper and lower rods to obtain a small Marangoni number, such as Ma = 50, was calculated for a 5 mm high liquid bridge for several molten metals. For molten silver, the possible temperature difference was estimated to be 16 K, whereas, for molten silicon, this was 0.38 K, which is unrealistic for the purposes of experiments. For silver, a free surface can be obtained in the wide range of oxygen partial pressures, whereas, for molten silicon, the available oxygen partial pressure range is very small; equilibrium oxygen partial pressure for SiO₂ formation is as low as 1.1 × 10⁻¹⁴ Pa. A liquid bridge of molten silver was successfully prepared and temperature oscillation was observed; the estimated Marangoni number was 160 and oscillation frequency was 0.26 Hz.     

On the origin of ultrahigh energy cosmic rays

The origin of cosmic rays with energy E ? 10¹⁸ eV is a long-standing problem in astrophysics. The development of ever larger detectors has brought in key experimental results in the past decade, most particularly the detection of a cut-off at the expected position for the long sought Greisen–Zatsepin–Kuzmin suppression as well as evidence for large scale anisotropies. This paper summarizes and discusses the recent achievements in this field.     

Nonlinear processes in cosmic-ray precursor of strong supernova shock: Maximum energy and average energy spectrum of accelerated particles

The instability in the cosmic-ray precursor of a supernova shock is studied. The level of turbulence in this region determines the maximum energy of accelerated particles. The consideration is not limited by the case of weak turbulence. It is assumed that the Kolmogorov type nonlinear wave interactions together with the ion-neutral collisions restrict the amplitude of random magnetic field. As a result, the maximum energy of accelerated particles strongly depends on the age of a SNR. The average spectrum of cosmic rays injected in the interstellar medium in the course of adiabatic SNR evolution takes the approximate form E⁻² at energies larger than 10–30 GeV/nucleon with the maximum energy that is close to the position of the knee in cosmic-ray spectrum at 4 × 10¹⁵ eV. At an earlier stage of SNR evolution – the ejecta-dominated stage, the particles are accelerated to higher energies and have a rather steep power-law distribution. These results suggest that the knee may mark the transition from the ejecta-dominated to the adiabatic evolution of SNR shocks which accelerate cosmic rays.     

Some recent results on extragalactic X-ray sources from the Einstein observatory

Extragalactic research studies by the Harvard/Smithsonian group with the Einstein Observatory have emphasized quasars and clusters of galaxies. More than 100 QSO's have been detected, including 20 serendipitous discoveries. The ratio of L_x/L_o for radio loud quasars is on the average 3 times that of radio quiet ones. QSO's with a large intrinsic optical luminosity have a smaller ratio of L_x/L_o. X-ray images of clusters of galaxies reveal a variety of morphological types which may correspond to different stages in their evolution. Several examples of bi-modal clusters have been discovered. An X-ray plume associated with M86 is apparently gas being stripped. From X-ray studies, a mass between 1.7 × 10¹³M_θ and 4.0 × 10¹³ M_θ has been derived for M87.     

Low energy observations of Cygnus X-2 by Ariel VI

Ariel VI observations of Cygnus X-2 have revealed a rather flat spectrum between 0.1 and 1.5 keV with variable emission at low energy. Of the two conflicting interpretations of this object in terms of i) a distant high-luminosity (L_x 10³⁸ ergs s⁻¹) binary and ii) a nearby low-luminosity (L_x 10³⁵ ergs s⁻¹) degenerate dwarf system, our measurements support the latter.     

A linear stability analysis of large-Prandtl-number thermocapillary liquid bridges

A linear stability analysis is applied to determine the onset of oscillatory thermocapillary convection in cylindrical liquid bridges of large Prandtl numbers (4  Pr  50). We focus on the relationships between the critical Reynolds number Re_c, the azimuthal wave number m, the aspect ratio Γ and the Prandtl number Pr. A detailed Re_c–Pr stability diagram is given for liquid bridges with various Γ. In the region of Pr > 1, which has been less studied previously and where Re_c has been usually believed to decrease with the increase of Pr, we found Re_c exhibits an early increase for liquid bridges with Γ around one. From the computed surface temperature gradient, it is concluded that the boundary layers developed at both solid ends of liquid bridges strengthen the stability of basic axisymmetric thermocapillary convection at large Prandtl number, and that the stability property of the basic flow is determined by the “effective” part of liquid bridge.     

Prognoz-6 data about ultraviolet sky background in dark and Milky Way regions of the sky

Ultraviolet spectra (1100–1900 Å) of the sky background of 10 wide angle (6°×6°) regions obtained between 70 000 km and 200 000 km from the Earth with the photoelectric spectrometer “GALACTIKA” on board the satellite “PROGNOZ-6” are considered. The spectral energy distribution of the sky background, after subtraction of the stellar component, is similar for regions on both sides of the Milky Way and exhibits a strong U.V. light contribution. On the contrary, the Milky Way (l_II=190° b_II=+6°) is less rich in far U.V. light; this can be related to the predominance of an expected selective absorption near the galactic plane. The nature of U.V. excess at high galactic latitudes needs further investigations.     

ETALON spin period determination from kHz SLR data

Using kHz Satellite LASER Ranging (SLR) data of the SLR station Graz only, we determined the spin periods of the two ETALON satellites – launched into high orbits of about 20,000 km – and their spin period increase during 3 years. The determined spin period values and spin period increase rates at 2004-01-01 are: T_ET1 = 63 s + 0.484 s/year, and T_ET2 = 65.5 s + 0.401 s/year.     

Geomagnetic effects on mid-latitude railways: A statistical study of anomalies in the operation of signaling and train control equipment on the East-Siberian Railway

Intense geomagnetically induced currents (GIC) can hamper rail traffic by disturbing signaling and train control systems. GIC threats have been a concern for technological systems at high-latitude locations due to geomagnetic disturbances driven by substorm expansion electrojet or convection electrojet intensifications. However, other geomagnetic storm processes such as storm sudden commencement (SSC) and geomagnetic pulsations can also cause GIC concerns for technological systems. We present in this paper the first evidence based on statistical data for links between geomagnetic disturbances and faulty operations (anomalies) in the functioning of railway automatics and telemetry. We analyze anomalies of automatic signaling and train control equipment which occurred in 2004 on the East-Siberian Railway (corrected geomagnetic latitude _m = 46–51°N and longitude λ_m = 168–187°E). Our results reveal a seasonal effect in the number of anomalies per train similar to the one observed in geomagnetic activity (Kp, Ap, Dst indices). We also found an increase by a factor of 3 in the total duration of daily anomalies during intense geomagnetic storms (local geomagnetic index specific to Siberian Observatory A_max > 30), with a significant correlation between the daily sum of durations of anomalies with geomagnetic activity. Special attention was paid to failures not related to recognized technical malfunctions. We found that the probability of these failures occurring in geomagnetically disturbed periods was 5–7 times higher than the average anomaly occurrence.     

Photoelectron flux variations observed from the FAST satellite

This paper examines high resolution (ΔE/E = 0.15) photoelectron energy spectra from 10 eV to 1 keV, created by solar irradiances between 1.2 and 120 nm. The observations were made from the FAST satellite at ∼3000 km, equatorward of the auroral oval for the July–August, 2002 solar rotation. These data are compared with the solar irradiance observed by the Solar EUV Experiment (SEE) on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite and fluxes calculated using the Field Line Interhemispheric Plasma (FLIP) code. The 41 eV photoelectron flux, which corresponds to solar EUV fluxes near 20 nm, shows a clear solar rotation variation in very good agreement with the EUV flux measurements. This offers the possibility that the 41 eV photoelectron flux could be used as a check on measured solar EUV fluxes near 20 nm. Because of unexpected noise, the solar rotation signal is not evident in the integral photoelectron flux between 156 and 1000 eV corresponding to EUV wavelengths between 0.1 and 7 nm measured by the SEE instrument. Examination of daily averaged photoelectron fluxes at energies between 25 and 500 eV show significant changes in the photoelectron spectra in response X and M class flares. The intensity of photoelectrons produced in this energy region is primarily due to two very narrow EUV wavelength regions at 2.3 and 3 nm driving Auger photoionization in O at 500 eV and N₂ at ∼360 eV. Comparison of calculated and daily averaged electron fluxes shows that the HEUVAC model solar spectrum used in the FLIP code does not reproduce the observed variations in photoelectron intensity. In principle, the 21 discrete photoelectron energy channels could be used to improve the reliability of the solar EUV fluxes at 2.3 and 3 nm inferred from broad band observations. In practice, orbital biases in the way the data were accumulated and/or noise signals arising from natural and anthropogenic longitudinally restricted sources of ionization complicate the application of this technique.     

Studying the evolution of the hot universe with the X-ray evolving universe spectroscopy mission – XEUS

Europe is one of the major partners building the International Space Station (ISS) and European industry, together with ESA, is responsible for many station components including the Columbus Orbital Facility, the Automated Transport Vehicle, two connecting modules and the European Robotic Arm. Together with this impressive list of contributions there is a strong desire within the ESA Member States to benefit from this investment by utilizing the unique capabilities of the ISS to perform world-class science. XEUS is one of the astronomical applications being studied by ESA to utilize the capabilities of the ISS. XEUS will be a long-term X-ray observatory with an initial mirror area of 6 m² at 1 keV that will be expanded to 30 m² following a visit to the ISS. The 1 keV spatial resolution is expected to be 2–5″ half-energy-width. XEUS will consist of separate detector and mirror spacecraft (MSC) aligned by active control to provide a focal length of 50 m. A new detector spacecraft, complete with the next generation of instruments, will also be added after visiting the ISS. The limiting 0.1–2.5 keV sensitivity will then be 4 × 10⁻¹⁸ erg cm⁻² s⁻¹, around 200 times better than XMM-Newton, allowing XEUS to study the properties of the hot baryons and dark matter at high redshift.