Despite numerous observational and theoretical attempts, the heating problem of the solar chromosphere still remains unsolved. We develop a novel 3D two-fluid model that accounts for dynamics of ...charged species and neutrals, and use it to perform the numerical simulations of granulation driven jets and associated waves in a quiet region of the solar chromosphere. The energy carried by the waves is dissipated through ion-neutral collisions, which are sufficient to balance radiative energy losses and to sustain the quasi-stationary atmosphere whose ion and neutral number densities, ionization fraction, and temperature profiles are relatively close to the observationally based semi-empirical model. Additional verification of our results is provided by a good fit of the numerically predicted waveperiod variations with height to the recent observational data. These observational validations of the numerical results demonstrate that the wave heating problem of a quiet region of the chromosphere may be solved.
A novel model of the solar atmosphere that accounts for partially ionized plasma is developed and used to study the propagation of magnetoacoustic-gravity waves, which are generated by solar ...granulation. The model includes neutrals in otherwise ionized plasma and therefore the considered waves are two-fluid waves. Numerical simulations of these waves allow computing their cutoff period and its variations in the solar atmosphere. The results of these computations are compared to the observational data collected by Wi niewska et al. and Kayshap et al., and a good agreement between the theory and observations is obtained. This first theoretical confirmation of the observational data profoundly shows the importance of effects caused by partially ionized plasma on the behavior of waves in the solar atmosphere, and on the origin of solar chromospheric oscillations. It is also suggested that theoretically predicted differences between the behavior of ions and neutrals can be verified by some currently operating solar missions.
Context.
We investigate the wave heating problem of a solar quiet region and present its plausible solution without involving shock formation.
Aims.
We aim to use numerical simulations to study wave ...propagation and dissipation in the partially ionized solar atmosphere, whose model includes both neutrals and ions.
Methods.
We used a 2.5D two-fluid model of the solar atmosphere to study the wave generation and propagation. The source of these waves is the solar convection located beneath the photosphere.
Results.
The energy carried by the waves is dissipated through ion-neutral collisions, which replace shocks used in some previous studies as the main source of local heating in quiet regions.
Conclusions.
We show that the resulting wave dissipation is sufficient to balance radiative and thermal energy losses, and to sustain a quasi-stationary atmosphere whose averaged temperature profile agrees well with the observationally based semi-empirical model of Avrett & Loeser (2008, ApJS, 175, 229).
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Using high-resolution numerical simulations we investigate the plasma heating driven by periodic two-fluid acoustic waves that originate at the bottom of the photosphere and propagate into the ...gravitationally stratified and partially ionized solar atmosphere. We consider ions+electrons and neutrals as separate fluids that interact between themselves via collision forces. The latter play an important role in the chromosphere, leading to significant damping of short-period waves. Long-period waves do not essentially alter the photospheric temperatures, but they exhibit the capability of depositing a part of their energy in the chromosphere. This results in up about a five times increase of ion temperature that takes place there on a timescale of a few minutes. The most effective heating corresponds to waveperiods within the range of about 30-200 s with a peak value located at 80 s. However, we conclude that for the amplitude of the driver chosen to be equal to 0.1 km s−1, this heating is too low to balance the radiative losses in the chromosphere.
With the use of our JOANNA code, which solves radiative equations for ion + electron and neutral fluids, we perform realistic 2.5D numerical simulations of plasma outflows associated with the solar ...granulation. These outflows exhibit physical quantities that are consistent, to the order of magnitude, with the observational findings for mass and energy losses in the upper chromosphere, transition region, and inner corona, and they may originate the fast solar wind.
Context.
We present new insight into the long-standing problem of plasma heating in the lower solar atmosphere in terms of collisional dissipation caused by two-fluid Alfvén waves.
Aims.
Using ...numerical simulations, we study Alfvén wave propagation and dissipation in a magnetic flux tube and their heating effect.
Methods.
We set up 2.5-dimensional numerical simulations with a semi-empirical model of a stratified solar atmosphere and a force-free magnetic field mimicking a magnetic flux tube. We consider a partially ionized plasma consisting of ion + electron and neutral fluids, which are coupled by ion-neutral collisions.
Results.
We find that Alfvén waves, which are directly generated by a monochromatic driver at the bottom of the photosphere, experience strong damping. Low-amplitude waves do not thermalize sufficient wave energy to heat the solar atmospheric plasma. However, Alfvén waves with amplitudes greater than 0.1 km s
−1
drive through ponderomotive force magneto-acoustic waves in higher atmospheric layers. These waves are damped by ion-neutral collisions, and the thermal energy released in this process leads to heating of the upper photosphere and the chromosphere.
Conclusions.
We infer that, as a result of ion-neutral collisions, the energy carried initially by Alfvén waves is thermalized in the upper photosphere and the chromosphere, and the corresponding heating rate is large enough to compensate radiative and thermal-conduction energy losses therein.
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Context.
We present new insight into the propagation of ion magnetoacoustic and neutral acoustic waves in a magnetic arcade in the lower solar atmosphere.
Aims.
By means of numerical simulations, we ...(a) study two-fluid waves propagating in a magnetic arcade embedded in the partially ionised, lower solar atmosphere and (b) investigate the effect of the background magnetic field configuration on the observed wave-periods.
Methods.
We considered a 2D approximation of the gravitationally stratified and partially ionised lower solar atmosphere consisting of ion plus electron and neutral fluids that are coupled by ion-neutral collisions. In this model, the convection below the photosphere causes the excitation of ion magnetoacoustic-gravity and neutral acoustic-gravity waves.
Results.
We find that in the solar photosphere, where ions and neutrals are strongly coupled by collisions, ion magnetoacoustic-gravity and neutral acoustic-gravity waves have periods ranging from 250 s to 350 s. In the chromosphere, where the collisional coupling is weak, the wave characteristics strongly depend on the magnetic field configuration. Above the footpoints of the considered arcade, the plasma is dominated by a vertical magnetic field along which ion magnetoacoustic-gravity waves propagate. These waves exhibit a broad range of periods, and the most prominent periods are 180 s, 220 s, and 300 s. Above the main loop of the solar arcade, where mostly horizontal magnetic field lines guide ion magnetoacoustic-gravity waves, the main spectral power reduces to the period of about 180 s, and no longer wave-periods exist.
Conclusions.
In photospheric regions, ongoing solar granulation excites a broad spectrum of wave-periods that undergoes complex interactions: mode-coupling, refractions through the inhomogeneous atmosphere, real physical absorption, and conversion of wave power. We found that, in addition, the magnetic arcade configuration with a partially ionised plasma drastically changes the image of wave-periods observed in the upper layers of the chromosphere and corona. Our results agree with recent observational data.
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The possibility of inducing resistance to the two-spotted spider mite,
Tetranychus urticae
Koch, in ‘Gala’ apple trees growing under optimal fertilization or nitrogen-deficiency conditions was ...investigated. The effects of jasmonic acid (JA) at 1.5 and 2.5 mM, and acibenzolar-
S
-methyl (benzothiadiazole, BTH) at 0.5 and 1.5 mM, applied separately or together, on the fecundity of
T. urticae
females in a laboratory test as well as on the population growth of the pest in a greenhouse experiment were determined. The influence of both elicitors on the induction of LOX and PAL gene expression was assessed in a parallel experiment using real-time PCR. Jasmonic acid showed significantly higher effectiveness in inducing apple tree resistance to
T. urticae
, as compared to BTH. This was particularly evident in the reduction in pest numbers that was observed in the greenhouse experiment and was also confirmed by increased LOX gene expression after treatment with JA. BTH induced the expression of the PAL gene more strongly than jasmonic acid; however, this was not reflected in the performance of the two-spotted spider mite in the laboratory and greenhouse experiments. It was also found that the antagonistic effect of BTH on JA might lead to decreased effectiveness of the jasmonic acid used to induce apple tree resistance to the two-spotted spider mite. Although nitrogen fertilization stimulated the development of spider mite populations, the resistance induction mechanism was more effective in N-fertilized plants, which was especially evident at the higher jasmonic acid concentration.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
The multitude of measurement data obtained from BSPM (Body Surface Potential Mapping) requires automatic detection and classification methods to detect disturbances. The article describes ...the method of classification of heart rate disorders based on the characteristics of signals from sensors. For the research, a coefficient was created that allows the classification of cardiac arrhythmias in the BSPM measurements. In addition, BSPM signals were simulated using a system constructed for testing an innovative measuring vest with 102 measuring electrodes.
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