53 research outputs found
Eigenoscillations of the Differentially Rotating Sun: I. 22-year, 4000-year, and quasi-biennial modes
Retrograde waves with frequencies much lower than the rotation frequency
become trapped in the solar radiative interior. The eigenfunctions of the
compressible, nonadiabatic, Rossby-like modes (-mechanism and
radiative losses taken into account) are obtained by an asymptotic method
assuming a very small latitudinal gradient of rotation, without an arbitrary
choice of other free parameters. An integral dispersion relation for the
complex eigenfrequencies is derived as a solution of the boundary value
problem. The discovered resonant cavity modes (called R-modes) are
fundamentally different from the known r-modes: their frequencies are functions
of the solar interior structure, and the reason for their existence is not
related to geometrical effects. The most unstable R-modes are those with
periods of 1--3 yr, 18--30 yr, and 1500--20000 yrs; these three separate period
ranges are known from solar and geophysical data. The growing times of those
modes which are unstable with respect to the -mechanism are and years, respectively. The amplitudes of the R-modes are
growing towards the center of the Sun. We discuss some prospects to develop the
theory of R-modes as a driver of the dynamics in the convective zone which
could explain, e.g., observed short-term fluctuations of rotation, a control of
the solar magnetic cycle, and abrupt changes of terrestrial climate in the
past.Comment: 17 pages, 6 figures, To appear in Astronomy and Astrophysic
Eigenoscillations of the differentially rotating Sun: II. Generalization of Laplace's tidal equation
The general PDE governing linear, adiabatic, nonraradial oscillations in a
spherical, differentially and slowly rotating non-magnetic star is derived.
This equation describes mainly low-frequency and high-degree g-modes,
convective g-modes, and rotational Rossby-like vorticity modes and their mutual
interaction for arbitrarily given radial and latitudinal gradients of the
rotation rate. In "traditional approximation" the angular parts of the
eigenfunctions are described by Laplace's tidal equation generalized here to
take into account differential rotation. From a qualitative analysis of
Laplace's tidal equation the sufficient condition for the formation of the
dynamic shear latitudinal Kelvin-Helmholtz instability (LKHI) is obtained. The
exact solutions of Laplace's equation for low frequencies and rigid rotation
are obtained. There exists only a retrograde wave spectrum in this ideal case.
The modes are subdivided into two branches: fast and slow modes. The long fast
waves carry energy opposite to the rotation direction, while the shorter
slow-mode group velocity is in the azimuthal plane along the direction of
rotation. The eigenfuncions are expressed by Jacobi's polynomials which are
polynomials of higher order than the Legendre's for spherical harmonics. The
solar 22-year mode spectrum is calculated. It is shown that the slow 22-year
modes are concentrated around the equator, while the fast modes are around the
poles. The band of latitude where the mode energy is concentrated is narrow,
and the spatial place of these band depends on the wave numbers (l, m).Comment: 16 pages, 11 figures, to appear in Astronomy and Astrophysic
Gravitational Instability in Radiation Pressure Dominated Backgrounds
I consider the physics of gravitational instabilities in the presence of
dynamically important radiation pressure and gray radiative diffusion, governed
by a constant opacity, kappa. For any non-zero radiation diffusion rate on an
optically-thick scale, the medium is unstable unless the classical gas-only
isothermal Jeans criterion is satisfied. When diffusion is "slow," although the
dynamical Jeans instability is stabilized by radiation pressure on scales
smaller than the adiabatic Jeans length, on these same spatial scales the
medium is unstable to a diffusive mode. In this regime, neglecting gas
pressure, the characteristic timescale for growth is independent of spatial
scale and given by (3 kappa c_s^2)/(4 pi G c), where c_s is the adiabatic sound
speed. This timescale is that required for a fluid parcel to radiate away its
thermal energy content at the Eddington limit, the Kelvin-Helmholz timescale
for a radiation pressure supported self-gravitating object. In the limit of
"rapid" diffusion, radiation does nothing to suppress the Jeans instability and
the medium is dynamically unstable unless the gas-only Jeans criterion is
satisfied. I connect with treatments of Silk damping in the early universe. I
discuss several applications, including photons diffusing in regions of extreme
star formation (starburst galaxies & pc-scale AGN disks), and the diffusion of
cosmic rays in normal galaxies and galaxy clusters. The former (particularly,
starbursts) are "rapidly" diffusing and thus cannot be supported against
dynamical instability in the linear regime by radiation pressure alone. The
latter are more nearly "slowly" diffusing. I speculate that the turbulence in
starbursts may be driven by the dynamical coupling between the radiation field
and the self-gravitating gas, perhaps mediated by magnetic fields. (Abridged)Comment: 15 pages; accepted to Ap
Neutrino Oscillations, Fluctuations and Solar Magneto-gravity Waves
This review has two parts. The first part summarizes the current
observational constraints on fluctuations in the solar medium deep within the
solar Radiative Zone, and shows how the KamLAND and SNO-salt data combine to
make the experimental determination of the neutrino oscillation parameters
largely insensitive to prior assumptions about the nature of these
oscillations. As part of a search for plausible sources of solar fluctuations
to which neutrinos could be sensitive, the second part of the talk summarizes a
preliminary analysis of the influence of magnetic fields on helioseismic waves.
Using simplifying assumptions which should apply to modes in the solar
radiative zone, we find a resonance between Alfven waves and helioseismic
g-modes which potentially modifies the solar density profile fairly
significantly over comparatively short distance scales, too narrow to be ruled
out by present-day analyses of p-wave helioseismic spectra.Comment: Plenary talk presented at AHEP 2003, Valencia, Spain, October 200
Large mixing angle oscillations as a probe of the deep solar interior
We re-examine the sensitivity of solar neutrino oscillations to noise in the
solar interior using the best current estimates of neutrino properties. Our
results show that the measurement of neutrino properties at KamLAND provides
new information about fluctuations in the solar environment on scales to which
standard helioseismic constraints are largely insensitive. We also show how the
determination of neutrino oscillation parameters from a combined fit of KamLAND
and solar data depends strongly on the magnitude of solar density fluctuations.
We argue that a resonance between helioseismic and Alfven waves might provide a
physical mechanism for generating these fluctuations and, if so,
neutrino-oscillation measurements could be used to constrain the size of
magnetic fields deep within the solar radiative zone.Comment: 13 pages, LaTeX file using AASLaTeX, 6 figures included. Improved
version including the new KamLAND data. To appear in APJ letter
Resonant origin for density fluctuations deep within the Sun: helioseismology and magneto-gravity waves
We analyze helioseismic waves near the solar equator in the presence of
magnetic fields deep within the solar radiative zone. We find that reasonable
magnetic fields can significantly alter the shapes of the wave profiles for
helioseismic g-modes. They can do so because the existence of density gradients
allows g-modes to resonantly excite Alfven waves, causing mode energy to be
funnelled along magnetic field lines, away from the solar equatorial plane. The
resulting wave forms show comparatively sharp spikes in the density profile at
radii where these resonances take place. We estimate how big these waves might
be in the Sun, and perform a first search for observable consequences. We find
the density excursions at the resonances to be too narrow to be ruled out by
present-day analyses of p-wave helioseismic spectra, even if their amplitudes
were to be larger than a few percent. (In contrast it has been shown in
(Burgess et al. 2002) that such density excursions could affect solar neutrino
fluxes in an important way.) Because solar p-waves are not strongly influenced
by radiative-zone magnetic fields, standard analyses of helioseismic data
should not be significantly altered. The influence of the magnetic field on the
g-mode frequency spectrum could be used to probe sufficiently large
radiative-zone magnetic fields should solar g-modes ever be definitively
observed. Our results would have stronger implications if overstable solar
g-modes should prove to have very large amplitudes, as has sometimes been
argued.Comment: 18 pages, 6 figures; misprints correcte
Cornering Solar Radiative-Zone Fluctuations with KamLAND and SNO Salt
We update the best constraints on fluctuations in the solar medium deep
within the solar Radiative Zone to include the new SNO-salt solar neutrino
measurements. We find that these new measurements are now sufficiently precise
that neutrino oscillation parameters can be inferred independently of any
assumptions about fluctuation properties. Constraints on fluctuations are also
improved, with amplitudes of 5% now excluded at the 99% confidence level for
correlation lengths in the range of several hundred km. Because they are
sensitive to correlation lengths which are so short, these solar neutrino
results are complementary to constraints coming from helioseismology.Comment: 4 pages, LaTeX file using RevTEX4, 6 figures include
БИОЛОГИЧЕСКАЯ ЭФФЕКТИВНОСТЬ РАЗЛИЧНЫХ ПРЕПАРАТОВ ПРОТИВ СЕМЕННОЙ ИНФЕКЦИИ СОСУДИСТОГО БАКТЕРИОЗА КАПУСТЫ
Black rot (pathogen – Xanthomonas campestris pv. campestris) is one of the most harmful diseases of brassicas. Seedlings growing in trays in greenhouse can meet rapid spreading of the pathogen and heavy yield loss even at very low seed infection level. This work was targeted on efficiency comparison for different plant protection agents against black root infection in seeds. Antibacterial effect of the agents was tested in vitro by well diffusion, direct placement of the agent onto bacterial lawn, and by incubation of bacterial suspension with the agents. Biological efficiency of the agents against seed infection was tests by seed soaking or by wet treatment. High antibacterial effect against black rot pathogen in vitro was shown for bacteriophage cocktail, Biocomposite-correct, Zeroxxe, Peroxyacetic acid (NUK15), Ps 11, and Kocide 2000. Highest biological efficiency against seed infection by black rot was shown for bacteriophage cocktail, Biocomposite-correct, Zeroxxe, Peroxyacetic acid (NUK15), and Kocide 2000.Сосудистый бактериоз (возбудитель – Xanthomonas campestris pv. campestris) – одна из наиболее опасных болезней капустных культур. При выращивании рассадным методом даже небольшая зараженность семян приводит к массовому распространению патогена и, в дальнейшем, к значительным потерям урожая в поле. Целью работы было сравнительное испытание эффективности препаратов различного происхождения в отношении семенной инфекции сосудистого бактериоза капусты. Проводили оценку антибактериальной активности препаратов in vitro методом диффузии из лунок, методом нанесения капли препарата на газон бактерий, а также методом совместной инкубации суспензий испытываемых препаратов и патогена. Оценку биологическую эффективности препаратов против семенной инфекции сосудистого бактериоза капусты проводили методами замачивания семян и обработки с увлажнением. Показано, что сильной антибактериальной активностью по отношению к возбудителю сосудистого бактериоза капусты в условиях in vitro обладали консорциум бактериофагов, Биокомпозит-коррект, Зерокс, НУК 15, Ps 11 и Косайд 2000. Наибольшую биологическую эффективность в подавлении семенной инфекции сосудистого бактериоза показали бактериофаги, Биокомпозит-коррект, НУК 15, Зерокс и Косайд 2000
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