1,236 research outputs found
Multiple Polar Cap Arcs: Akebono (Exos D) Observations
Akebono (Exos D) observations demonstrate that polar cap arcs sometimes have a fine structure, that is, multiple (double or triple) arcs with spacing of a few tens of kilometers. The multiple polar cap arcs are dominantly observed in the nightside polar cap region, suggesting that low background conductance favors the appearance of the structured arcs. A relationship between the spacing and the average energy of the precipitating electrons is investigated. Results show that a higher energy leads to a wider spacing. Akebono observations also show the existence of a downward current region embedded between upward current regions (arcs). Comparison of the observations with results from a coupled magnetosphere-ionosphere Sun-aligned arc model is made, which shows good qualitative agreement between the modeling and observational results on the spacing-energy dependence and the effect of background ionospheric conductance
LHR band emissions at mid-latitude and their relationship to ionospheric ELF hiss and relativistic electrons
LHR band emissions observed at mid-latitude were investigated using data from the EXOS-C (Ohzora) satellite. A typical feature of the LHR band emissions is a continuous banded structure without burst-like and cut-off features whose center frequency decreases as the satellite moves to higher latitudes. A statistical analysis of the occurrence characteristics of the phenomena showed that mid-latitude LHR emissions are distributed inside the plasmapause during magnetically quiet periods, and the poleward boundary of the emission region moves to lower latitudes as the magnetic activity increases. The altitude distribution of the waves suggests that the propagation in the LHR duct formed horizontally in the mid-latitude upper-ionosphere. The emission is closely related to the occurrence of ionospheric ELF hiss. It is also shown that LHR emissions are commonly observed in the slot region of the radiation belt, and they sometimes accompany the enhancement of the ionospheric electron temperature. The generation of the LHR band emissions is discussed based on the observed characteristics
Prominent 5d-orbital contribution to the conduction electrons in gold
We have examined the valence-band electronic structures of gold and silver in
the same column in the periodic table with nominally filled d orbitals by means
of a recently developed polarization-dependent hard x-ray photoemission.
Contrary to a common expectation, it is found that the 5d-orbital electrons
contribute prominently to the conduction electrons in gold while the conduction
electrons in silver are to some extent free-electron-like with negligible 4d
contribution, which could be related to a well-known fact that gold is more
stable than silver in air. The 4d electron correlation effects are found to be
essential for the conduction electron character in silver.Comment: 8 pages, 4 figures, to be appeared in New J. Phys
Oral Transmission of Chagas Disease by Consumption of Açaí Palm Fruit, Brazil
In 2006, a total of 178 cases of acute Chagas disease were reported from the Amazonian state of Pará, Brazil. Eleven occurred in Barcarena and were confirmed by visualization of parasites on blood smears. Using cohort and case–control studies, we implicated oral transmission by consumption of açaí palm fruit
Field-driven topological glass transition in a model flux line lattice
We show that the flux line lattice in a model layered HTSC becomes unstable
above a critical magnetic field with respect to a plastic deformation via
penetration of pairs of point-like disclination defects. The instability is
characterized by the competition between the elastic and the pinning energies
and is essentially assisted by softening of the lattice induced by a
dimensional crossover of the fluctuations as field increases. We confirm
through a computer simulation that this indeed may lead to a phase transition
from crystalline order at low fields to a topologically disordered phase at
higher fields. We propose that this mechanism provides a model of the low
temperature field--driven disordering transition observed in neutron
diffraction experiments on single crystals.Comment: 11 pages, 4 figures available upon request via snail mail from
[email protected]
Study of electron anti-neutrinos associated with gamma-ray bursts using KamLAND
We search for electron anti-neutrinos () from long and
short-duration gamma-ray bursts~(GRBs) using data taken by the KamLAND detector
from August 2002 to June 2013. No statistically significant excess over the
background level is found. We place the tightest upper limits on
fluence from GRBs below 7 MeV and place first constraints on
the relation between luminosity and effective temperature.Comment: 16 pages and 5 figure
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