On the mechanism of the post-midnight winter NmF2 enhancements: dependence on solar activity

The mechanism of the N_mF₂ peak formation at different levels of solar activity is analyzed using Millstone Hill IS radar observations. The h_mF₂ nighttime increase due to thermospheric winds and the downward plasmaspheric fluxes are the key processes responsible for the N_mF₂ peak formation. The electron temperature follows with the opposite sign the electron density variations in this process. This mechanism provides a consistency with the Millstone Hill observations on the set of main parameters. The observed decrease of the nighttime N_mF₂ peak amplitude with solar activity is due to faster increasing of the recombination efficiency compared to the plasmaspheric flux increase. The E × B plasma drifts are shown to be inefficient for the N_mF₂ nighttime peak formation at high solar activity.     

A self-similar solution for spherically symmetric gravitational collapse

A model of gas-dynamical flow during gravitational collapse is analyzed mathematically by assuming its spherical symmetry and self-similarity. A shock wave diverging from the center emerges in this model. The physical requirements imposed on the post-shock flow at the center for the specified parameters at infinity unambiguously determine the shock front and the flow behind it.     

He II → He I recombination of primordial helium plasma including the effect of neutral hydrogen

The He II → He I recombination of primordial helium plasma (z ? 1500–3000) is considered in terms of the standard cosmological model. This process affects the formation of cosmic microwave background anisotropy and spectral distortions. We investigate the effect of neutral hydrogen on the He II → He I recombination kinetics with partial and complete redistributions of radiation in frequency in the He I resonance lines. We show that to properly compute the He II → He I recombination kinetics, it is important to take into account not only the wings in the absorption and emission profiles of the He I resonance lines, but also the mechanism of the redistribution of resonance photons in frequency. Thus, for example, the relative difference in the numbers of free electrons for the model using Doppler absorption and emission profiles and the model using a partial redistribution in frequency is 1–1.3% for the epoch z = 1770–1920. The relative difference in the numbers of free electrons for the model using a partial redistribution in frequency and the model using a complete redistribution in frequency is 1–3.8% for the epoch z = 1750–2350.     

Unusual stripes in emission and absorption in solar radio bursts: Ropes of fibers in the meter wave band

Based on data from the spectrographs of IZMIRAN and Tremsdorf station (Astronomical Institute, Potsdam), we analyze the ropes of narrow-band fibers in the spectra of solar radio bursts in the meter wave band by invoking events of satellite data (SOHO/LASCO, EIT, MDI) for the analysis. We consider in detail basic properties of the ropes in four events in comparison with previously known data. The fibers in ropes are more commonly observed with an overlap in time and frequency, but occasionally (more often at the end of the ropes) they can follow with a separation in time. The fiber duration and recurrence period seldom remain stable and, in general, increase from 0.3–0.5 s at the beginning to several seconds at the end of the rope. The relative values of the instantaneous and total fiber frequency bandwidths change only slightly in different events; δ f / f ≈ 0.003–0.005 and Δf / f ≈ 0.02–0.03. Most of the ropes exhibit a low-frequency absorption. The fibers in ropes are similar to ordinary intermediate drift bursts (fiber bursts), but they drift in a narrow frequency band and have a more frequent recurrence in some events. The ropes of fibers are usually observed in the time interval when the shock front catches up with the leading edge of a coronal mass ejection. Under the condition of a unified approach to interpreting the ropes of fibers in all events, their basic properties can be explained in terms of the model of fiber bursts. The connection of fibers with the developed zebra pattern is shown within the framework of a unified approach to the formation theory of stripes in emission and absorption in the model on whistlers.     

Analysis of bromate and bromide in drinking water by ion chromatography-inductively coupled plasma mass spectrometry

A method for the detection of bromate and bromide in drinking water by ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) was developed. The optimized conditions of IC including pH and concentration of the effluent were studied. The results showed that the above two species of bromine were baseline separated within nine minutes under the optimized conditions. The detection limits (S/N=3) of bromate and bromide were 0.23 and 0.12 μg/L, respectively. The RSD (n=6) of the peak areas was 1.2%-3.5%. The method has been successfully applied to the determination of the type bromide in drinking water samples. The recoveries were 95%-109%. The method can be used for the regular analysis of bromate and bromide in real drinking water samples.     

Plasma cortisol and glucose concentrations in the striped mullet (Mugil cephalus L.) subjected to intense handling stress

The plasma cortisol and glucose concentrations were determined in mature female striped mullet (Mugil cephalus L.) subjected to short term intense handling stress. The results indicated that plasma cortisol levels reached a peak 20 min after stress and declined gradually afterwards. The highest concentration of plasma glucose was observed 30 min after stress. The present study showed that the rise of plasma glucose was associated with the plasma cortisol levels.     

Dynamics of the flows accreting onto a magnetized neutron star

We investigate the unsteady column accretion of material at a rate \(10^{15} g s^{ - 1} \leqslant \dot M \leqslant 10^{16} g s^{ - 1}\) onto the surface of a magnetized neutron star using a modified first-order Godunov method with splitting. We study the dynamics of the formation and evolution of a shock in an accretion column near the surface of a star with a magnetic field 5×10¹¹≤B≤10¹³ G. An effective transformation of the accretion flow energy into cyclotron radiation is shown to be possible for unsteady accretion with a collisionless shock whose front executes damped oscillations. The collisionless deceleration of the accreting material admits the conservation of a fraction of the heavy nuclei that have not been destroyed in spallation reactions. The fraction of the CNO nuclei that reach the stellar atmosphere is shown to depend on the magnetic field strength of the star.     

High-time resolution conjugate SuperDARN radar observations of the dayside convection response to changes in IMF B y

We present data from conjugate SuperDARN radars describing the high-latitude ionospheres response to changes in the direction of IMF B_y during a period of steady IMF B_z southward and B_x positive. During this interval, the radars were operating in a special mode which gave high-time resolution data (30 s sampling period) on three adjacent beams with a full scan every 3 min. The location of the radars around magnetic local noon at the time of the event allowed detailed observations of the variations in the ionospheric convection patterns close to the cusp region as IMF B_y varied. A significant time delay was observed in the ionospheric response to the IMF By changes between the two hemispheres. This is explained as being partially a consequence of the location of the dominant merging region on the magnetopause, which is 8/12R_E closer to the northern ionosphere than to the southern ionosphere (along the magnetic field line) due to the dipole tilt of the magnetosphere and the orientation of the IMF. This interpretation supports the anti-parallel merging hypothesis and highlights the importance of the IMF B_x component in solar wind-magnetosphere coupling.     

Space Plasma Exploration by Active Radar (SPEAR): an overview of a future radar facility

SPEAR is a new polar cap HF radar facility which is to be deployed on Svalbard. The principal capabilities of SPEAR will include the generation of artificial plasma irregularities, operation as an all-sky HF radar, the excitation of ULF waves, and remote sounding of the magnetosphere. Operation of SPEAR in conjunction with the multitude of other instruments on Svalbard, including the EISCAT Svalbard radar, and the overlap of its extensive field-of-view with that of several of the HF radars in the SuperDARN network, will enable in-depth diagnosis of many geophysical and plasma phenomena associated with the cusp region and the substorm expansion phase. Moreover, its ability to produce artificial radar aurora will provide a means for the other instruments to undertake polar cap plasma physics experiments in a controlled manner. Another potential use of the facility is in field-line tagging experiments, for coordinated ground-satellite experiments. Here the scientific objectives of SPEAR are detailed, along with the proposed technical specifications of the system.