Astronomy Reports最新文献

Long-term manned space missions require the design and construction of “space greenhouses” to replenish food supplies and regenerate the atmosphere. Increased levels of ionizing radiation outside the Earth’s magnetosphere can significantly affect the efficiency of photosynthesis, the process by which plants use light energy to synthesize organic matter and produce oxygen. Identifying the mechanisms of the effect of ionizing radiation on photosynthesis and determining the optimal parameters for the operation of space greenhouses can help compensate for the impact of space conditions on plant productivity. This paper shows that irradiation of wheat plants (Triticum aestivum L.) at a dose of 100 Gy significantly increases the rate of plant development and disrupts their ability to use light energy in photosynthesis. A range of illumination intensities was found at which the efficiency of light energy use in irradiated plants coincided with this parameter in control plants. The disruption of the connection between photosystem II and the antenna of the light-harvesting complex caused by oxidative stress is assumed to be the mechanism of the identified imbalance in the functioning of the photosynthetic apparatus.

The paper presents the results of a laboratory experiment with detailed measurements of the dynamics and spatial structure of a plasma flow similar to astrophysical jets. For the first time in such experiments, the magnetic field component generated by a shear flow in a rarefied background plasma was measured. It was shown that it can be interpreted as an Alfvén wing. The drift electric field in the jet propagation region was also measured. All these findings confirm that the external magnetic field remains frozen into the plasma flow throughout its propagation over distances significantly exceeding the ion’s Larmor radius.

The magnetic field, including hypomagnetic conditions, is a key astrogeophysical factor that requires comprehensive study of its effects on living systems. Planned interplanetary missions will, on the one hand, encounter the absence of Earth’s geomagnetic field and, on the other, face strong inhomogeneity in the spacecraft’s own magnetic field. Of particular interest is how both the amplitude and the spatial characteristics of magnetic-field inhomogeneity affect human cells under laboratory conditions simulating orbital environments. In vitro cell culture under strictly controlled incubator conditions is a common experimental approach in biological research. CO₂-incubators provide control over temperature, gas composition, and humidity. Recent studies report that incubators can significantly alter the ambient magnetic field. Here, we show that two types of CO₂-incubators substantially modify magnetic-field parameters, and that the nature of these modifications depends on the incubator model. One incubator exhibited pronounced spatial inhomogeneity of the magnetic field, with regions of both low and high field strength. The other incubator, during operation, generated magnetic-field oscillations with period of oscillations about several seconds and peak-to-peak amplitude exceeding the mean value. We found that the magnetic background markedly affects the growth of human embryonic kidney cells. The effect of an ultra-low-frequency (ULF) magnetic field with a period of several seconds was especially pronounced and is relevant to space applications. Nutrient-deficiency-induced stress increased cellular sensitivity to this factor. These results emphasize the importance of weak static and time-varying magnetic fields for cell-growth processes, particularly in combination with other adverse conditions.

The results of MHD simulations of supersonic astrophysical and laboratory jets in an external poloidal magnetic field (({{B}_{r}}), ({{B}_{z}})) taking into account the rotation of the matter, are presented. The ejected matter is collimated by the magnetic field, the degree of collimation and the flow structure depend on the relation between of the magnetic field induction and the angular velocity of the matter. For a strong magnetic field and moderate rotation, a barrel-shaped structure of an elongated shape is formed, which leaves behind a stable outflow. Inside the jet ejection, a barrel-shaped a periodic shock-wave structure is observed. For a moderate magnetic field and rapid rotation, the ejected matter at first significantly expands, but then gradually collimates into a jet due to the appearance of a toroidal magnetic field ({{B}_{phi }}). A cocoon-shaped structure is formed. It spreads to the boundary of the computational domain. Inside the jet cocoon, a cavity with a low density of matter, quasi-stationary in time near is formed. In all cases, the rotation of the matter in the jet is transmitted to neighboring regions, which ultimately leads to the generation of magneto-torsional oscillations associated with the appearance of a toroidal component of the field. The toroidal field ({{B}_{phi }}) arises during the twisting of the poloidal magnetic field due to the dependence of the jet matter angular velocity on the radial ((r)) and axial ((z)) coordinates. The toroidal field also participates in the collimation of the jet.

The article deals with the possibility of using high-resolution imaging X-ray spectroscopy to study the parameters of the interaction region of a laser-plasma aluminium supersonic flow (jet) with an argon gas wall in a model experiment with astrophysical similarity to Herbig–Haro objects. Experiments of this kind are promising for the realisation with modern nanosecond laser complexes with a pulse energy of several tens of J up to several kJ (intensity I_las ~ 10¹²–10¹⁴ W/cm²) and can extend the understanding of the processes taking place in the space environment as well as verify existing theoretical models. The modelling of the laboratory object was carried out in 2 stages—first the macroscopic properties of the object were calculated using a hydrodynamic simulation, and then the calculated spatio-temporal profiles of the macroscopic parameters were fed into a non-stationary kinetic code, which was used to model the radiative properties of the process under consideration. It is shown that the simulated X-ray spectrograms allow to estimate the plasma parameters in the interaction region of the laser-plasma jet with the gas cloud based on the relative intensities of the spectral lines of multiply charged argon ions and the location of this region based on the spatial distribution of the argon ion glow.

Plasma jets injected into an external magnetic field and background plasma using electrodynamic coaxial accelerators can be used for limited laboratory modeling of various astrophysical phenomena, including jet formation, matter accretion in young stars, and supernova explosions. Estimates show that modeling such characteristic astrophysical phenomena as, for example, the generation of quasi-perpendicular collisionless shocks, requires relatively high plasma flow velocities—at least 100 km/s. Model experiments conducted at the large-scale “Krot” facility utilized a new power supply system for the coaxial accelerator, which allowed for an order-of-magnitude increase in the energy of the generated plasma and a several-fold increase in its velocity compared to the results obtained previously [1, 2]. Increasing the energy of the carbon-hydrogen plasma jet allows for an increased scale of its interaction with the magnetic field and background plasma, bringing the experimental conditions closer to the collisionless expansion regime, which is relevant for solving problems in space plasma dynamics. Specifically, using diagnostics based on synchronous high-speed plasma imaging and magnetic probe measurements, plasma fractions were identified that most likely represent ions of different masses accelerated to various energies, including a fraction with velocities exceeding 100 km/s. The picture of plasma flow instabilities, flute instabilities mainly, became much richer with increasing plasma flow energy and velocity compared to previous observations.

The paper presents a laboratory simulation of the electrostatic activation of lunar regolith dust particles at the light–shadow boundary. The experimental simulations were carried out in a vacuum chamber at a pressure of about ~5 × 10^–5 Torr in order to eliminate aerodynamic effects. Dust particles simulating lunar regolith were used, with grain-size distribution and dielectric properties close to those of real lunar material. A system of electrodes made it possible to create a tunable electric field above the particle-covered surface, with a field strength of up to 3 kV/cm. Excimer lamps were used as a simulator of solar radiation, providing hard ultraviolet emission with a power density close to the UV part of the solar spectrum that reaches the surfaces of airless bodies. A recording system based on a stereoscopic pair of video cameras captures images of particles in a region illuminated by a laser beam. Using a digital image-processing algorithm, three-dimensional particle trajectories were reconstructed. In this work, four different regimes leading to particle transport were investigated: (i) in the presence of an electric field only; (ii) with preliminary UV illumination and an applied electrostatic field; (iii) under abrupt changes of UV illumination (simulating transitions from light to shadow and vice versa); (iv) residual phenomena after the removal of external forcing. The experimental results obtained quantitatively and qualitatively confirmed the key role of photocharging (due to photoemission) in lowering the threshold of the electrostatic lifting and levitation mechanism for dust particles. A significant influence of abrupt changes in UV illumination of the regolith simulant on the dust dynamics was also demonstrated. The results are useful for refining models of the near-surface lunar dust exosphere and for the design of dust sensors and dust-mitigation measures in future missions.

The process of launching and supersonic propagation of plasma outflow is studied on the basis of numerical modeling in “plasma focus” type facilities within the framework of laboratory modeling of jets from young stellar objects. The energy flows existing at the initial stage of formation of plasma outflow are studied in detail. It is shown that such energy flows can play a significant role in the process of its launch, forming, as in astrophysical jets, the Poynting vector flow in the direction of the outflow. Quantitative agreement with the measured values is achieved by taking into account the toroidal currents and energy flows converging to the axis.

The development and improvement of methods for measuring and detecting lightning discharge phenomena in orbital and laboratory experiments was carried out. Laboratory modeling of lightning discharge was carried out jointly with the Institute of Applied Physics of the Russian Academy of Sciences by studying the parameters of electromagnetic radiation of high-voltage discharges at the Groza GIN-1MV facility. In this case, electromagnetic radiation of high-voltage discharges generated at the Groza GIN-1MV facility was detected using detectors-spectrometers developed by the Scientific Research Institute of Nuclear Physics of Moscow State University for X-rays and gamma rays (with photon energy over 10 keV).

In disk accretion of gas onto a neutron star, high densities and temperatures are expected. The objective of the quantitative accretion model is to obtain boundary layer gas parameters during the development of small-scale instability. For critical accretion of incident matter on a neutron star, we have discussed the possibility of nucleosynthesis.