8,072 research outputs found
May 12 1997 Cme Event: I. a Simplified Model of the Pre-Eruptive Magnetic Structure
A simple model of the coronal magnetic field prior to the CME eruption on May
12 1997 is developed. First, the magnetic field is constructed by superimposing
a large-scale background field and a localized bipolar field to model the
active region (AR) in the current-free approximation. Second, this potential
configuration is quasi-statically sheared by photospheric vortex motions
applied to two flux concentrations of the AR. Third, the resulting force-free
field is then evolved by canceling the photospheric magnetic flux with the help
of an appropriate tangential electric field applied to the central part of the
AR.
To understand the structure of the modeled configuration, we use the field
line mapping technique by generalizing it to spherical geometry. It is
demonstrated that the initial potential configuration contains a hyperbolic
flux tube (HFT) which is a union of two intersecting quasi-separatrix layers.
This HFT provides a partition of the closed magnetic flux between the AR and
the global solar magnetic field. The vortex motions applied to the AR interlock
the field lines in the coronal volume to form additionally two new HFTs pinched
into thin current layers. Reconnection in these current layers helps to
redistribute the magnetic flux and current within the AR in the
flux-cancellation phase. In this phase, a magnetic flux rope is formed together
with a bald patch separatrix surface wrapping around the rope. Other important
implications of the identified structural features of the modeled configuration
are also discussed.Comment: 25 pages, 11 figures, to appear in ApJ 200
Accounting for correlations with core electrons by means of the generalized relativistic effective core potentials: Atoms Hg and Pb and their compounds
A way to account for correlations between the chemically active (valence) and
innermore (core) electrons in the framework of the generalized relativistic
effective core potential (GRECP) method is suggested. The "correlated" GRECP's
(CGRECP's) are generated for the Hg and Pb atoms. Only correlations for the
external twelve and four electrons of them, correspondingly, should be treated
explicitly in the subsequent calculations with these CGRECP's whereas the
innermore electrons are excluded from the calculations. Results of atomic
calculations with the correlated and earlier GRECP versions are compared with
the corresponding all-electron Dirac-Coulomb values. Calculations with the
above GRECP's and CGRECP's are also carried out for the lowest-lying states of
the HgH molecule and its cation and for the ground state of the PbO molecule as
compared to earlier calculations and experimental data. The accuracy for the
vibrational frequencies is increased up to an order of magnitude and the errors
for the bond lengths (rotational constants) are decreased in about two times
when the correlated GRECP's are applied instead of earlier GRECP versions
employing the same innercore-outercore-valence partitioning.Comment: 12 pages, 4 tables, the text of the paper was significantly improve
On the VLBI measurement of the Solar System acceleration
We propose new estimates of the secular aberration drift, mainly due to the
rotation of the Solar System about the Galactic center, based on up-to-date
VLBI observations and and improved method of outlier elimination. We fit
degree-2 vector spherical harmonics to extragalactic radio source proper motion
field derived from geodetic VLBI observations spanning 1979-2013. We pay
particular attention to the outlier elimination procedure to remove outliers
from (i) radio source coordinate time series and (ii) the proper motion sample.
We obtain more accurate values of the Solar system acceleration compared to
those in our previous paper. The acceleration vector is oriented towards the
Galactic center within 7 deg. The component perpendicular to the Galactic plane
is statistically insignificant. We show that an insufficient cleaning of the
data set can lead to strong variations in the dipole amplitude and orientation,
and statistically biased results.Comment: Accepted for publication in A&
Vector meson-vector meson interaction in a hidden gauge unitary approach
The formalism developed recently to study vector meson--vector meson
interaction, and applied to the case of , is extended to study the
interaction of the nonet of vector mesons among themselves. The interaction
leads to poles of the scattering matrix corresponding to bound states or
resonances. We show that 11 states (either bound or resonant) get dynamically
generated in nine strangeness-isospin-spin channels. Five of them can be
identified with those reported in the PDG, i.e., the , ,
, , and . The masses of the latter three
tensor states have been used to fine-tune the free parameters of the unitary
approach, i.e., the subtraction constants in evaluating the vector meson
-vector meson loop functions in the dimensional regularization scheme. The
branching ratios of these five dynamically generated states are found to be
consistent with data. The existence of the other six states should be taken as
predictions to be tested by future experiments.Comment: typos corrected; more discussions; one of the appendix rearrange
Magnon activation by hot electrons via non-quasiparticle states
We consider the situation when a femtosecond laser pulse creates a hot
electron state in half-metallic ferromagnet (e. g. ferromagnetic semiconductor)
on a picosecond timescale but do not act directly on localized spin system. We
show that the energy and magnetic moment transfer from hot itinerant electrons
to localized spins is facilitated by the so-called non-quasiparticle states,
which are the scattering states of a magnon and spin-majority electron. The
magnon distribution is described by a quantum kinetic equation that we derive
using the Keldysh diagram technique. In a typical ferromagnetic semiconductor
such as EuO magnons remain essentially in non-equilibrium on a scale of the
order of microsecond after the laser pulse.Comment: 8 pages, 2 figure
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