36,507 research outputs found
Tracking Vector Magnetograms with the Magnetic Induction Equation
The differential affine velocity estimator (DAVE) developed in Schuck (2006)
for estimating velocities from line-of-sight magnetograms is modified to
directly incorporate horizontal magnetic fields to produce a differential
affine velocity estimator for vector magnetograms (DAVE4VM). The DAVE4VM's
performance is demonstrated on the synthetic data from the anelastic
pseudospectral ANMHD simulations that were used in the recent comparison of
velocity inversion techniques by Welsch (2007). The DAVE4VM predicts roughly
95% of the helicity rate and 75% of the power transmitted through the
simulation slice. Inter-comparison between DAVE4VM and DAVE and further
analysis of the DAVE method demonstrates that line-of-sight tracking methods
capture the shearing motion of magnetic footpoints but are insensitive to flux
emergence -- the velocities determined from line-of-sight methods are more
consistent with horizontal plasma velocities than with flux transport
velocities. These results suggest that previous studies that rely on velocities
determined from line-of-sight methods such as the DAVE or local correlation
tracking may substantially misrepresent the total helicity rates and power
through the photosphere.Comment: 30 pages, 13 figure
Topological vortices in generalized Born-Infeld-Higgs electrodynamics
A consistent BPS formalism to study the existence of topological axially
symmetric vortices in generalized versions of the Born-Infeld-Higgs
electrodynamics is implemented. Such a generalization modifies the field
dynamics via introduction of three non-negative functions depending only in the
Higgs field, namely, , and . A set of
first-order differential equations is attained when these functions satisfy a
constraint related to the Ampere law. Such a constraint allows to minimize the
system energy in such way that it becomes proportional to the magnetic flux.
Our results provides an enhancement of topological vortex solutions in
Born-Infeld-Higgs electrodynamics. Finally, we analyze a set of models such
that a generalized version of Maxwell-Higgs electrodynamics is recovered in a
certain limit of the theory.Comment: 8 pages, 8 figures, to appear in EPJ
Dynamical evolution of V-type asteroids in the central main belt
V-type asteroids are associated with basaltic composition, and are supposed
to be fragments of crust of differentiated objects. Most V-type asteroids in
the main belt are found in the inner main belt, and are either current members
of the Vesta dynamical family (Vestoids), or past members that drifted away.
However, several V-type photometric candidates have been recently identified in
the central and outer main belt.
The origin of this large population of V-type objects is not well understood.
Since it seems unlikely that Vestoids crossing the 3J:-1A mean-motion resonance
with Jupiter could account for the whole population of V-type asteroids in the
central and outer main belt, origin from local sources, such as the parent
bodies of the Eunomia, and of the Merxia and Agnia asteroid families, has been
proposed as an alternative mechanism.
In this work we investigated the dynamical evolution of the V-type
photometric candidates in the central main belt, under the effect of
gravitational and non-gravitational forces. Our results show that dynamical
evolution from the parent bodies of the Eunomia and Merxia/Agnia families on
timescales of 2 Byr or more could be responsible for the current orbital
location of most of the low-inclined V-type asteroids.Comment: 16 pages, 10 figures, 3 tables. Accepted for publication in MNRA
Dynamical evolution and chronology of the Hygiea asteroid family
The asteroid (10) Hygiea is the fourth largest asteroid of the Main Belt, by
volume and mass, and it is the largest member of its own family. Previous works
investigated the long-term effects of close encounters with (10) Hygiea of
asteroids in the orbital region of the family, and analyzed the taxonomical and
dynamical properties of members of this family. In this paper we apply the
high-quality SDSS-MOC4 taxonomic scheme of DeMeo and Carry (2013) to members of
the Hygiea family core and halo, we obtain an estimate of the minimum time and
number of encounter necessary to obtain a (or 99.7%) compatible
frequency distribution function of changes in proper caused by close
encounters with (10) Hygiea, we study the behavior of asteroids near secular
resonance configurations, in the presence and absence of the Yarkovsky force,
and obtain a first estimate of the age of the family based on orbital diffusion
by the Yarkovsky and YORP effects with two methods.
The Hygiea family is at least 2 Byr old, with an estimated age of Myr and a relatively large initial ejection velocity field,
according to the approach of Vokrouhlick\'{y} et al. (2006a, b). Surprisingly,
we found that the family age can be shortened by 25% if the dynamical
mobility caused by close encounters with (10) Hygiea is also accounted for,
which opens interesting new research lines for the dynamical evolution of
families associated with massive bodies. In our taxonomical analysis of the
Hygiea asteroid family, we also identified a new V-type candidate: the asteroid
(177904) (2005 SV5). If confirmed, this could be the fourth V-type object ever
to be identified in the outer main belt.Comment: 13 page, 15 figures, and 4 table
MIMAC : A micro-tpc matrix for directional detection of dark matter
Directional detection of non-baryonic Dark Matter is a promising search
strategy for discriminating WIMP events from background. However, this strategy
requires both a precise measurement of the energy down to a few keV and 3D
reconstruction of tracks down to a few mm. To achieve this goal, the MIMAC
project has been developed. It is based on a gaseous micro-TPC matrix, filled
with CF4 and CHF3. The first results on low energy nuclear recoils (H, F)
obtained with a low mono-energetic neutron field are presented. The discovery
potential of this search strategy is discussed and illustrated by a realistic
case accessible to MIMAC.Comment: 6 pages, Proc. of the fifth international symposium on large TPCs for
low energy rare event detection, Paris, France, Dec. 2010. To appear in
Journal of Physic
Quantum open systems and turbulence
We show that the problem of non conservation of energy found in the
spontaneous localization model developed by Ghirardi, Rimini and Weber is very
similar to the inconsistency between the stochastic models for turbulence and
the Navier-Stokes equation. This sort of analogy may be useful in the
development of both areas.Comment: to appear in Physical Review
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