94 research outputs found
A Model for the Sources of the Slow Solar Wind
Models for the origin of the slow solar wind must account for two seemingly
contradictory observations: The slow wind has the composition of the closed
field corona, implying that it originates from the continuous opening and
closing of flux at the boundary between open and closed field. On the other
hand, the slow wind also has large angular width, up to ~ 60{\circ}, suggesting
that its source extends far from the open-closed boundary. We propose a model
that can explain both observations. The key idea is that the source of the slow
wind at the Sun is a network of narrow (possibly singular) open-field corridors
that map to a web of separatrices and quasi-separatrix layers in the
heliosphere. We compute analytically the topology of an open-field corridor and
show that it produces a quasi-separatrix layer in the heliosphere that extends
to angles far from the heliospheric current sheet. We then use an MHD code and
MDI/SOHO observations of the photospheric magnetic field to calculate
numerically, with high spatial resolution, the quasi-steady solar wind and
magnetic field for a time period preceding the August 1, 2008 total solar
eclipse. Our numerical results imply that, at least for this time period, a web
of separatrices (which we term an S-web) forms with sufficient density and
extent in the heliosphere to account for the observed properties of the slow
wind. We discuss the implications of our S-web model for the structure and
dynamics of the corona and heliosphere, and propose further tests of the model
Molecular and phenotypic characterisation of NS maize inbred lines.
ΠΡΠΊΡΡΡΠ· ΡΠ΅ Π±ΠΈΡΠ½Π° Π²ΡΡΡΠ° ΠΊΠΎΡΠ° ΠΈΡΠΏΠΎΡΠ°Π²Π° Π²Π΅Π»ΠΈΠΊΡ ΡΠ΅Π½ΠΎΡΠΈΠΏΡΠΊΡ ΠΈ Π³Π΅Π½Π΅ΡΠΈΡΠΊΡ
Π²Π°ΡΠΈΡΠ°Π±ΠΈΠ»Π½ΠΎΡΡ. Π£ ΠΎΠ²ΠΎΠΌ ΡΠ°Π΄Ρ ΠΈΠ·Π²ΡΡΠ΅Π½Π° ΡΠ΅ ΡΠ΅Π½ΠΎΡΠΈΠΏΡΠΊΠ° ΠΈ ΠΌΠΎΠ»Π΅ΠΊΡΠ»Π°ΡΠ½Π° ΠΊΠ°ΡΠ°ΠΊΡΠ΅ΡΠΈΠ·Π°ΡΠΈΡΠ°
Π΄ΠΈΠ²Π΅ΡΠ³Π΅Π½ΡΠ½ΠΈΡ
ΠΈΠ½Π±ΡΠ΅Π΄ Π»ΠΈΠ½ΠΈΡΠ° ΠΊΡΠΊΡΡΡΠ·Π° ΠΊΠΎΡΠ΅ ΡΠ΅ ΠΊΠΎΡΠΈΡΡΠ΅ Ρ ΠΎΠΏΠ»Π΅ΠΌΠ΅ΡΠΈΠ²Π°ΡΠΊΠΈΠΌ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΈΠΌΠ°
ΠΈ ΠΊΠΎΡΠ΅ ΠΏΡΠ΅Π΄ΡΡΠ°Π²ΡΠ°ΡΡ ΠΌΠΎΠ³ΡΡΠΈ ΠΈΠ·Π²ΠΎΡ Π°Π»Π΅Π»Π° ΡΠ° ΠΏΠΎΠ·ΠΈΡΠΈΠ²Π½ΠΈΠΌ ΡΡΠΈΡΠ°ΡΠ΅ΠΌ Π½Π° Π°Π³ΡΠΎΠΌΠΎΠ½ΡΠΊΠΈ Π²Π°ΠΆΠ½Π΅
ΠΎΡΠΎΠ±ΠΈΠ½Π΅. Π’Π°ΠΊΠΎΡΠ΅, ΠΈΠ΄Π΅Π½ΡΠΈΡΠΈΠΊΠΎΠ²Π°Π½ΠΈ ΡΡ Π°Π»Π΅Π»ΠΈ ΠΊΠ°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΡΠ½ΠΈ Π·Π° ΠΎΠ΄ΡΠ΅ΡΠ΅Π½Π΅
Ρ
Π΅ΡΠ΅ΡΠΎΡΠΈΡΠ½Π΅ Π³ΡΡΠΏΠ΅ ΠΈ ΡΡΠ²ΡΡΠ΅Π½Π΅ ΡΡ ΠΏΠΎΡΠ΅Π½ΡΠΈΡΠ°Π»Π½ΠΎ Π·Π½Π°ΡΠ°ΡΠ½Π΅ Π²Π΅Π·Π΅ ΠΈΠ·ΠΌΠ΅ΡΡ ΠΌΠ°ΡΠΊΠ΅ΡΠ° ΠΈ
Π°Π³ΡΠΎΠ½ΠΎΠΌΡΠΊΠΈ Π²Π°ΠΆΠ½ΠΈΡ
ΡΠ²ΠΎΡΡΡΠ°Π²Π° ΠΏΡΠΈΠΌΠ΅Π½ΠΎΠΌ Π°ΡΠΎΡΠΈΡΠ°ΡΠΈΠ²Π½Π΅ Π°Π½Π°Π»ΠΈΠ·Π΅, ΡΠ° ΡΠΈΡΠ΅ΠΌ Π΄Π°ΡΠ΅
ΠΏΡΠΈΠΌΠ΅Π½Π΅ Ρ ΠΌΠ°ΡΠΊΠ΅Ρ Π°ΡΠΈΡΡΠΈΡΠ°Π½ΠΎΡ ΡΠ΅Π»Π΅ΠΊΡΠΈΡΠΈ. ΠΠ½Π°Π»ΠΈΠ·ΠΈΡΠ°Π½ΠΈ ΠΌΠ°ΡΠ΅ΡΠΈΡΠ°Π» ΡΠ°ΡΡΠΎΡΠ°ΠΎ ΡΠ΅ ΠΎΠ΄ 96
ΠΈΠ½Π±ΡΠ΅Π΄ Π»ΠΈΠ½ΠΈΡΠ° ΠΈΠ· ΡΠ΅ΡΠΈΡΠΈ Ρ
Π΅ΡΠ΅ΡΠΎΡΠΈΡΠ½Π΅ Π³ΡΡΠΏΠ΅. Π’ΡΠΈΠ΄Π΅ΡΠ΅Ρ ΡΠ΅ΡΡ ΠΌΠΈΠΊΡΠΎΡΠ°ΡΠ΅Π»ΠΈΡΡΠΊΠΈΡ
ΠΌΠ°ΡΠΊΠ΅ΡΠ° ΠΊΠΎΡΠΈΡΡΠ΅Π½ΠΎ ΡΠ΅ Π·Π° ΠΈΠ·ΡΠ°ΡΡΠ½Π°Π²Π°ΡΠ΅ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΠ°ΡΠ° Π΄ΠΈΠ²Π΅ΡΠ·ΠΈΡΠ΅ΡΠ° Π³Π΅Π½ΡΠΊΠΈΡ
Π»ΠΎΠΊΡΡΠ°.
ΠΡΠΈΠΌΠ΅ΡΠ΅Π½Π΅ ΡΡ ΡΡΠΈ ΠΊΠ»Π°ΡΡΠ΅Ρ Π°Π½Π°Π»ΠΈΠ·Π΅ Π½Π° ΠΏΠΎΠ΄Π°ΡΠΈΠΌΠ° Π΄ΠΎΠ±ΠΈΡΠ΅Π½ΠΈΠΌ ΠΌΠΎΠ»Π΅ΠΊΡΠ»Π°ΡΠ½ΠΎΠΌ Π°Π½Π°Π»ΠΈΠ·ΠΎΠΌ.
ΠΠΎΡΡΠΊΠΈ ΠΎΠ³Π»Π΅Π΄ΠΈ ΡΡ ΠΏΠΎΡΡΠ°Π²ΡΠ΅Π½ΠΈ Ρ ΡΠΎΠΊΡ Π΄Π²Π΅ Π³ΠΎΠ΄ΠΈΠ½Π΅, ΠΏΠΎ ΠΏΠΎΡΠΏΡΠ½ΠΎ ΡΠ»ΡΡΠ°ΡΠ½ΠΎΠΌ Π±Π»ΠΎΠΊ ΡΠΈΡΡΠ΅ΠΌΡ
ΡΠ° ΡΡΠΈ ΠΏΠΎΠ½Π°Π²ΡΠ°ΡΠ°. ΠΠ΅ΡΠΊΡΠΈΠΏΡΠΈΠ²Π½Π° ΡΡΠ°ΡΠΈΡΡΠΈΠΊΠ°, Π°Π½Π°Π»ΠΈΠ·Π° Π²Π°ΡΠΈΡΠ°Π½ΡΠ΅, Π»ΠΈΠ½Π΅Π°ΡΠ½Π΅ ΠΊΠΎΡΠ΅Π»Π°ΡΠΈΡΠ΅
ΠΈ Π°Π½Π°Π»ΠΈΠ·Π° Π³Π»Π°Π²Π½ΠΈΡ
ΠΊΠΎΠΌΠΏΠΎΠ½Π΅Π½ΡΠΈ ΠΈΠ·ΡΠ°ΡΡΠ½Π°ΡΠ΅ ΡΡ Π·Π° 13 ΠΎΡΠΎΠ±ΠΈΠ½Π°. ΠΠ΅Π·Π΅ ΠΈΠ·ΠΌΠ΅ΡΡ ΠΌΠ°ΡΠΊΠ΅ΡΠ° ΠΈ
ΠΎΡΠΎΠ±ΠΈΠ½Π° ΡΡΠ²ΡΡΠ΅Π½Π΅ ΡΡ ΠΏΡΠΈΠΌΠ΅Π½ΠΎΠΌ ΠΎΠΏΡΡΠ΅Π³ ΠΈ ΠΌΠ΅ΡΠΎΠ²ΠΈΡΠΎΠ³ Π»ΠΈΠ½Π΅Π°ΡΠ½ΠΎΠ³ ΠΌΠΎΠ΄Π΅Π»Π°. ΠΡΠΎΡΠ΅ΡΠ°Π½
Π±ΡΠΎΡ Π°Π»Π΅Π»Π° ΠΈΠ·Π½ΠΎΡΠΈΠΎ ΡΠ΅ 8,3, ΠΏΡΠΎΡΠ΅ΡΠ½Π° ΠΏΠΎΠ»ΠΈΠΌΠΎΡΡΠ½ΠΎΡΡ ΠΏΠΎΡΠ΅Π΄ΠΈΠ½Π°ΡΠ½ΠΈΡ
Π»ΠΎΠΊΡΡΠ° ΠΈΠ·Π½ΠΎΡΠΈΠ»Π° ΡΠ΅
0,64, Π° ΠΏΡΠΎΡΠ΅Π½Π°Ρ ΡΠ΅ΡΠΊΠΈΡ
Π°Π»Π΅Π»Π° 8,5% ΠΏΠΎ Π»ΠΎΠΊΡΡΡ. Π£ΠΎΡΠ΅Π½ ΡΠ΅ Π²Π΅ΡΠΈ Π³Π΅Π½Π΅ΡΠΈΡΠΊΠΈ Π΄ΠΈΠ²Π΅ΡΠ·ΠΈΡΠ΅Ρ
ΠΊΠΎΠ΄ BSSS Π½Π΅Π³ΠΎ ΠΊΠΎΠ΄ Lancaster Π»ΠΈΠ½ΠΈΡΠ°. ΠΠΈΡΠ΅ ΠΎΠ΄ ΡΡΠ΅ΡΠΈΠ½Π΅ Π°Π»Π΅Π»Π° Π±ΠΈΠ»ΠΎ ΡΠ΅ ΠΊΠ°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΡΠ½ΠΎ
Π·Π° ΡΠ°ΠΌΠΎ ΡΠ΅Π΄Π½Ρ Π³ΡΡΠΏΡ. Π Π΅Π·ΡΠ»ΡΠ°ΡΠΈ ΠΊΠ»Π°ΡΡΠ΅Ρ Π°Π½Π°Π»ΠΈΠ·Π° ΡΡ Ρ Π²Π΅Π»ΠΈΠΊΠΎΡ ΠΌΠ΅ΡΠΈ Π±ΠΈΠ»ΠΈ Ρ ΠΌΠ΅ΡΡΡΠΎΠ±Π½ΠΎΡ
ΡΠ°Π³Π»Π°ΡΠ½ΠΎΡΡΠΈ. ΠΠ½Π°Π»ΠΈΠ·Π° Π²Π°ΡΠΈΡΠ°Π½ΡΠ΅ ΡΠΊΠ°Π·Π°Π»Π° ΡΠ΅ Π½Π° ΠΏΠΎΡΡΠΎΡΠ°ΡΠ΅ ΡΡΠ°ΡΠΈΡΡΠΈΡΠΊΠΈ Π·Π½Π°ΡΠ°ΡΠ½ΠΈΡ
ΡΠ°Π·Π»ΠΈΠΊΠ° ΠΎΡΠΎΠ±ΠΈΠ½Π° ΠΌΠ΅ΡΡ ΠΈΠ½Π±ΡΠ΅Π΄ Π»ΠΈΠ½ΠΈΡΠ°ΠΌΠ°, Π³ΠΎΠ΄ΠΈΠ½Π°ΠΌΠ° ΠΈ Π»ΠΎΠΊΠ°Π»ΠΈΡΠ΅ΡΠΈΠΌΠ°. Π Π΅Π·ΡΠ»ΡΠ°ΡΠΈ ΠΊΠ»Π°ΡΡΠ΅Ρ
Π°Π½Π°Π»ΠΈΠ·Π΅ ΡΠ΅Π½ΠΎΡΠΈΠΏΡΠΊΠΈΡ
ΠΏΠΎΠ΄Π°ΡΠ°ΠΊΠ° Π±ΠΈΠ»ΠΈ ΡΡ Ρ ΠΌΠ°ΡΠΎΡ ΠΌΠ΅ΡΠΈ ΡΠ°Π³Π»Π°ΡΠ½ΠΈ ΡΠ° ΠΏΠ΅Π΄ΠΈΠ³ΡΠ΅ΠΈΠΌΠ° Π»ΠΈΠ½ΠΈΡΠ°,
Π½Π΅Π³ΠΎ ΡΠ΅Π·ΡΠ»Π°ΡΠΈ Π°Π½Π°Π»ΠΈΠ·Π΅ ΠΌΠΎΠ»Π΅ΠΊΡΠ»Π°ΡΠ½ΠΈΡ
ΠΏΠΎΠ΄Π°ΡΠ°ΠΊΠ°. ΠΠ½Π°Π»ΠΈΠ·Π° Π³Π»Π°Π²Π½ΠΈΡ
ΠΊΠΎΠΌΠΏΠΎΠ½Π΅Π½ΡΠΈ
ΠΈΠ·Π΄Π²ΠΎΡΠΈΠ»Π° ΡΠ΅ Π»ΠΈΠ½ΠΈΡΠ΅ ΠΏΡΠ΅ΠΌΠ° Ρ
Π΅ΡΠ΅ΡΠΎΡΠΈΡΠ½ΠΈΠΌ Π³ΡΡΠΏΠ°ΠΌΠ° ΠΈ ΠΈΡΡΠ°ΠΊΠ»Π° ΡΠΈΡ
ΠΎΠ²Π΅ ΠΎΠΏΡΡΠ΅
ΠΊΠ°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠ΅. ΠΠ΅Π»ΠΈΠΊΠΈ Π±ΡΠΎΡ ΡΡΠ²ΡΡΠ΅Π½ΠΈΡ
Π°Π»Π΅Π»Π° ΠΌΠ°ΡΠΊΠ΅ΡΠ° ΡΠ° ΡΡΠ°Π±ΠΈΠ»Π½ΠΈΠΌ ΠΏΠΎΠ·ΠΈΡΠΈΠ²Π½ΠΈΠΌ
Π΅ΡΠ΅ΠΊΡΠΈΠΌΠ° Π½Π° ΠΏΡΠΈΠ½ΠΎΡ ΡΠΊΠ°Π·ΡΡΠ΅ Π½Π° ΠΌΠΎΠ³ΡΡΠΈ Π·Π½Π°ΡΠ°Ρ ΠΎΠ²ΠΈΡ
ΠΌΠ°ΡΠΊΠ΅ΡΠ° Ρ ΠΎΠΏΠ»Π΅ΠΌΠ΅ΡΠΈΠ²Π°ΡΡ ΠΊΡΠΊΡΡΡΠ·Π°.Maize has great phenotypic and genotypic variability. In this study a diverse set
of maize inbred lines used in breeding programmes as a potential source of alleles with
positive effects on important agronomic traits, was characterised at phenotypic and
molecular level. Furthermore, alleles specific to heterotic groups were identified and
potentially significant associations between markers and important agronomic traits which
could be employed in marker assisted selection were determined. Ninety eight inbred lines
from four heterotic groups were analysed. Thirty six microsatellite markers were used to
obtain parameters for genetic diversity and three claster analyses were employed based on
molecular data. The field trials were set in randomised block design with three replications
during two years to acquire phenotypic data. Descriptive statistics, analysis of variance,
linear correlations and principal component analysis were performed for 13 traits. The
associations between markers and traits were identified by the application of general and
mixed linear model. The average number of alleles was 8,3, the average value of
polymorphism information content was 0,64, whereas the percentage of rare alleles was
8,5%. Greater genetic diversity of BSSS inbred lines compared to the lines from Lancaster
group were observed. More than one third of alleles were specific to only one of these two
groups. The results of cluster analyses were to a large extent in agreement with each other.
Analysis of variance indicated statistically significant differences in traits among inbred
lines, years and locations. Cluster analysis based on phenotypic data was in less consistent
with pedigrees of the inbred lines than the cluster analysis based on molecular data.
Principal component analysis grouped inbreds into heterotic groups and indicated their
general characteristics. A large number of identified marker alleles with stable positive
effects on grain yield suggested the potential importance of these markers in maiz
Genetic Variability in Different Lucerne (\u3cem\u3eMedicago Sativa\u3c/em\u3e) Genotypes
One of the basic goals of modern lucerne breeding programmes is creation of new cultivars with a great potential for high quality and stable yields of both forage and hay (Riday & Brummer, 2002). Such cultivars meet increased needs of animal husbandry and must contribute to diverse farming systems (Luki , 2000). Our trial was aimed at determining genetic variability of yield components in 7 lucerne genotypes, as well as at evaluation of their breeding potential as gene donors to new lucerne cultivar
Evidence for topological nonequilibrium in magnetic configurations
We use direct numerical simulations to study the evolution, or relaxation, of
magnetic configurations to an equilibrium state. We use the full single-fluid
equations of motion for a magnetized, non-resistive, but viscous fluid; and a
Lagrangian approach is used to obtain exact solutions for the magnetic field.
As a result, the topology of the magnetic field remains unchanged, which makes
it possible to study the case of topological nonequilibrium. We find two cases
for which such nonequilibrium appears, indicating that these configurations may
develop singular current sheets.Comment: 10 pages, 5 figure
Nonlinear force-free magnetic field extrapolations: comparison of the Grad-Rubin and Wheatland-Sturrock-Roumeliotis algorithm
We compare the performance of two alternative algorithms which aim to
construct a force-free magnetic field given suitable boundary conditions. For
this comparison, we have implemented both algorithms on the same finite element
grid which uses Whitney forms to describe the fields within the grid cells. The
additional use of conjugate gradient and multigrid iterations result in quite
effective codes. The Grad-Rubin and Wheatland-Sturrock-Roumeliotis algorithms
both perform well for the reconstruction of a known analytic force-free field.
For more arbitrary boundary conditions the Wheatland-Sturrock-Roumeliotis
approach has some difficulties because it requires overdetermined boundary
information which may include inconsistencies. The Grad-Rubin code on the other
hand loses convergence for strong current densities. For the example we have
investigated, however, the maximum possible current density seems to be not far
from the limit beyond which a force free field cannot exist anymore for a given
normal magnetic field intensity on the boundary.Comment: 21 pages, 13 figure
3D Coronal Density Reconstruction and Retrieving the Magnetic Field Structure during Solar Minimum
Measurement of the coronal magnetic field is a crucial ingredient in
understanding the nature of solar coronal phenomena at all scales. We employed
STEREO/COR1 data obtained during a deep minimum of solar activity in February
2008 (Carrington rotation CR 2066) to retrieve and analyze the
three-dimensional (3D) coronal electron density in the range of heights from
1.5 to 4 Rsun using a tomography method. With this, we qualitatively deduced
structures of the coronal magnetic field. The 3D electron density analysis is
complemented by the 3D STEREO/EUVI emissivity in the 195 A band obtained by
tomography for the same CR. A global 3D MHD model of the solar corona was used
to relate the reconstructed 3D density and emissivity to open/closed magnetic
field structures. We show that the density maximum locations can serve as an
indicator of current sheet position, while the locations of the density
gradient maximum can be a reliable indicator of coronal hole boundaries. We
find that the magnetic field configuration during CR 2066 has a tendency to
become radially open at heliocentric distances greater than 2.5 Rsun. We also
find that the potential field model with a fixed source surface (PFSS) is
inconsistent with the boundaries between the regions with open and closed
magnetic field structures. This indicates that the assumption of the potential
nature of the coronal global magnetic field is not satisfied even during the
deep solar minimum. Results of our 3D density reconstruction will help to
constrain solar coronal field models and test the accuracy of the magnetic
field approximations for coronal modeling.Comment: Published in "Solar Physics
Structure and Dynamics of the Sun's Open Magnetic Field
The solar magnetic field is the primary agent that drives solar activity and
couples the Sun to the Heliosphere. Although the details of this coupling
depend on the quantitative properties of the field, many important aspects of
the corona - solar wind connection can be understood by considering only the
general topological properties of those regions on the Sun where the field
extends from the photosphere out to interplanetary space, the so-called open
field regions that are usually observed as coronal holes. From the simple
assumptions that underlie the standard quasi-steady corona-wind theoretical
models, and that are likely to hold for the Sun, as well, we derive two
conjectures on the possible structure and dynamics of coronal holes: (1)
Coronal holes are unique in that every unipolar region on the photosphere can
contain at most one coronal hole. (2) Coronal holes of nested polarity regions
must themselves be nested. Magnetic reconnection plays the central role in
enforcing these constraints on the field topology. From these conjectures we
derive additional properties for the topology of open field regions, and
propose several observational predictions for both the slowly varying and
transient corona/solar wind.Comment: 26 pages, 6 figure
Slip-Squashing Factors as a Measure of Three-Dimensional Magnetic Reconnection
A general method for describing magnetic reconnection in arbitrary
three-dimensional magnetic configurations is proposed. The method is based on
the field-line mapping technique previously used only for the analysis of
magnetic structure at a given time. This technique is extended here so as to
analyze the evolution of magnetic structure. Such a generalization is made with
the help of new dimensionless quantities called "slip-squashing factors". Their
large values define the surfaces that border the reconnected or
to-be-reconnected magnetic flux tubes for a given period of time during the
magnetic evolution. The proposed method is universal, since it assumes only
that the time sequence of evolving magnetic field and the tangential boundary
flows are known. The application of the method is illustrated for simple
examples, one of which was considered previously by Hesse and coworkers in the
framework of the general magnetic reconnection theory. The examples help us to
compare these two approaches; they reveal also that, just as for magnetic null
points, hyperbolic and cusp minimum points of a magnetic field may serve as
favorable sites for magnetic reconnection. The new method admits a
straightforward numerical implementation and provides a powerful tool for the
diagnostics of magnetic reconnection in numerical models of solar-flare-like
phenomena in space and laboratory plasmas.Comment: 39 pages, 9 figures, corrected typos, to appear in ApJ, March 200
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