1,030 research outputs found
Transport and Loss of Ring Current Electrons Inside Geosynchronous Orbit During the 17 March 2013 Storm.
Ring current electrons (1-100 keV) have received significant attention in recent decades, but many questions regarding their major transport and loss mechanisms remain open. In this study, we use the four-dimensional Versatile Electron Radiation Belt code to model the enhancement of phase space density that occurred during the 17 March 2013 storm. Our model includes global convection, radial diffusion, and scattering into the Earth's atmosphere driven by whistler-mode hiss and chorus waves. We study the sensitivity of the model to the boundary conditions, global electric field, the electric field associated with subauroral polarization streams, electron loss rates, and radial diffusion coefficients. The results of the code are almost insensitive to the model parameters above 4.5 R E R E, which indicates that the general dynamics of the electrons between 4.5 R E and the geostationary orbit can be explained by global convection. We found that the major discrepancies between the model and data can stem from the inaccurate electric field model and uncertainties in lifetimes. We show that additional mechanisms that are responsible for radial transport are required to explain the dynamics of ≥40-keV electrons, and the inclusion of the radial diffusion rates that are typically assumed in radiation belt studies leads to a better agreement with the data. The overall effect of subauroral polarization streams on the electron phase space density profiles seems to be smaller than the uncertainties in other input parameters. This study is an initial step toward understanding the dynamics of these particles inside the geostationary orbit
Isolation of the Toxic Principle of \u3cem\u3eMoraea pallida\u3c/em\u3e by Means of the Sensory Receptors of Sheep
Chemical fractions of Moraea pallida were offered to a sheep in which aversion to the plant had previously been established. Fractions refused due to the presence of the aversive substance sensed by the sheep were further purified until a single substance had been isolated. The purified substance was characterized as epoxyscillirosidin, the toxic principle of M. pallida
Critical Phenomena in Neutron Stars I: Linearly Unstable Nonrotating Models
We consider the evolution in full general relativity of a family of linearly
unstable isolated spherical neutron stars under the effects of very small,
perturbations as induced by the truncation error. Using a simple ideal-fluid
equation of state we find that this system exhibits a type-I critical
behaviour, thus confirming the conclusions reached by Liebling et al. [1] for
rotating magnetized stars. Exploiting the relative simplicity of our system, we
are able carry out a more in-depth study providing solid evidences of the
criticality of this phenomenon and also to give a simple interpretation of the
putative critical solution as a spherical solution with the unstable mode being
the fundamental F-mode. Hence for any choice of the polytropic constant, the
critical solution will distinguish the set of subcritical models migrating to
the stable branch of the models of equilibrium from the set of subcritical
models collapsing to a black hole. Finally, we study how the dynamics changes
when the numerically perturbation is replaced by a finite-size, resolution
independent velocity perturbation and show that in such cases a nearly-critical
solution can be changed into either a sub or supercritical. The work reported
here also lays the basis for the analysis carried in a companion paper, where
the critical behaviour in the the head-on collision of two neutron stars is
instead considered [2].Comment: 15 pages, 9 figure
Preparation and characterization of Bi26–2xMn2xMo10O69-d and Bi26.4Mn0.6Mo10–2yMe2yO69-d(Me = V, Fe) solid solutions
Received: 06.06.2017; accepted: 23.06.2017; published: 14.07.2017.Single phase samples of bismuth molybdate, Bi26Mo10O69, doped with Mn on the bismuth sublattice and V, Fe on the molybdenum sublattice were found to crystallize in the triclinic Bi26Mo10O69 structure at low doping levels and in the monoclinic Bi26Mo10O69 structure - at higher dopant concentration. The assumption that all Mn ions have an oxidation state of +2 was confirmed by means of magnetic measurement results analysis using Curie-Weiss law. Conductivity was investigated using impedance spectroscopy. The conductivity of Bi26.4Mn0.6Mo9.6Fe0.4O69-d was 1.2*10-2 S*cm-1 at 973 K and 2.2*10-4 S*cm-1 at 623 K, and the conductivity of Bi26.4Mn0.6Mo9.2V0.8O69-d was 2.2*10-3 S*cm-1 at 973 K and 2.2*10-5 S*cm-1 at 623 K
Leadership style and its relation to employee attitudes and behaviour.
The purpose of this study was to determine the relationships between leadership style and organisational commitment, job satisfaction, job involvement and organisational citizenship behaviour and whether these relationships were stronger for transformational than for transactional leaders. A sample of 52 leaders and 276 raters from a world class engineering company participated. The results of a canonical correlation analysis using the rater data indicated that the most prominent relationship was that between transactional leadership and affective commitment. Furthermore, transformational and transactional leadership did not correlate significantly with the constructs of job involvement and job satisfaction
Space VLBI Observations of 3C371
We present the first space VLBI observations of 3C~371, carried out at a
frequency of 4.8 GHz. The combination of the high resolution provided by the
orbiting antenna Highly Advanced Laboratory for Communications and Astronomy
(HALCA) and the high sensitivity of the VLBA allows imaging of the jet of
3C~371 with an angular resolution of approximately 0.26 mas, which for this
relatively nearby source corresponds to 0.4 h pc. Comparison
between two epochs separated by 66 days reveals no apparent motions in the
inner 7 mas jet structure above an upper limit of c. This
value, the absence of detectable counterjet emission from the presumably
symmetric jet, plus the presence of extended double-lobe structure, are
consistent with the knots in the jet being stationary features such as standing
shocks. The jet intensity declines with the angular distance from the core as
. This is more gradual than that derived for 3C~120,
, for which there is evidence for strong intereactions between
the jet and ambient medium. This suggests that in 3C~371 there is a greater
level of {\it in situ} acceleration of electrons and amplification of magnetic
field. We interpret sharp bends in the jet at sites of off-center knots as
further evidence for the interaction between the jet and external medium, which
may also be responsible for the generation of standing recollimation shocks.
These recollimation shocks may be responsible for the presumably stationary
components. The radio properties of 3C~371 are intermediate between those of
other radio galaxies with bright cores and those of BL Lacertae objects.Comment: 5 pages, 4 figures. Accepted for publication in Ap
Multi-Wavelength Variability of the Synchrotron Self-Compton Model for Blazar Emission
Motivated by recent reports of strongly correlated radio and X-ray
variability in 3C279 (Grandi, etal 1995), we have computed the relative
amplitudes of variations in the synchrotron flux at and the self-Compton
X-ray flux at 1 keV () for a homogeneous sphere of relativistic
electrons orbiting in a tangled magnetic field. Relative to synchrotron
self-Compton scattering without induced Compton scattering, stimulated
scattering reduces the amplitude of by as much as an order of
magnitude when \tau_T \gtwid 1. When varies in a fixed magnetic
field, increases monotonically from 0.01 at , the
self-absorption turnover frequency, to at . The relative
amplitudes of the correlated fluctuations in the radio-mm and X-ray fluxes from
3C279 are consistent with the synchrotron self-Compton model if varies
in a fixed magnetic field and induced Compton scattering is the dominant source
of radio opacity. The variation amplitudes are are too small to be produced by
the passage of a shock through the synchrotron emission region unless the
magnetic field is perpendicular to the shock front.Comment: 21 pages, 4 fig
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