Photospheric and chromospheric oscillations in the base of coronal holes

In this paper we carry out an analysis of the spatial–temporal line-of-sight velocity variations measured in the chromospheric (H, H) and photospheric (Fei 6569 Å, Fei 4864 Å, Nii 4857 Å) lines at the base of 17 coronal holes. Time series of a duration from 43 to 120 min were recorded with the CCD line-array and the CCD matrix. Rather frequently we observed quasi-stationary upward flows with a measured velocity of up to 1 km s^–1 in the photosphere and up to 4–5 km s^–1 in the chromosphere (equivalent radial velocity of up to 3 km s^–1 and up to 12–15 km s^–1 accordingly) near dark points on the chromospheric network boundary inside polar CH. Line-of-sight velocity fluctuation spectra contain meaningful maxima in the low-frequency region clustering around the values 0.4, 0.75, and 1 mHz. Usually, the spatial localization of these maxima mutually coincides and, in our opinion, coincides with the chromospheric network boundary. Acoustic 3- and 5-min oscillations are enhanced in the coronal hole region and reach 1 km s^–1 in the photosphere and 3–4 km s^–1 in the chromosphere. These oscillations are not localized spatially and are distinguished throughout the entire region observed.     

Periodic processes and plasma motions in solar coronal holes

Episodic observations of coronal holes were carried out simultaneously in several spectral lines during the 2002–2005 observational seasons. An analysis of eighteen time series is used to obtain the amplitude—spectral properties of oscillatory wave motions of the solar plasma at the bases of coronal holes. It is found that the amplitudes of the 5-min and 3-min line-of-sight velocity oscillations increase in coronal holes. Low-frequency (1–2 mHz) oscillations are concentrated at the boundaries of the chromospheric network, while the 3-mHz and 5-mHz oscillations dominate in the network cells. Clear indications of propagating waves have been found at the bases of coronal holes. The 3 mHz phase velocities are 45 ± 5 km/s and 80–100 km/s for the equatorial and polar coronal holes, respectively.     

Periodic variations of the Hα profile width in the chromosphere of coronal holes as a possible indicator of Alfvén waves

We analyze the oscillations of the Hα profile width based on our observations of the chromosphere at the base of solar coronal holes. The maximum oscillation amplitude averaged over ten time series is 64 m 0 A. Direct calculations show that this value cannot be reached through temperature oscillations, because the periodic intensity fluctuations observed during our experiment did not exceed 5%, corresponding to Hα profile broadening only by 1.5–2 m Å. We hypothesize that the observed variations can result from the propagation of torsional Alfvén waves in the chromosphere of coronal holes.     

Multilevel hydrothermodynamic model of a deep basin

A hydrothermodynamic model based on the traditional system of differential equations is discussed. The model uses conservative finite-difference schemes based on the methods of identifying the barotropic and baroclinic velocity components and on the complete inversion of the dynamic operator. Test computations for the Black Sea basin have been conducted.Translated by Vladimir A. Puchkin.     

Electronic solar spectrum atlas of enriched functionality

Basic capabilities of the electronic solar spectrum atlas, together with the examples of its usage in observations or during the preparing to them, are presented. The program has been created at the Institute of Solar-Terrestrial Physics based on Liege Solar Spectrum Atlas and Kitt Peak Atlas and covers the spectral range from 3291 to 12000 Å. The convenient interface allows us to easily move to the required spectral range in order to obtain information about a spectral line of interest by a single click as well as to search line parameters in the database and to make changes in it. The additional functional abilities have made the atlas useful when calibrating magnetographs and estimating instrumental polarization degree.     

On the problem of numerical ocean hydrodynamics modelling

This paper describes a projection variant of the integration-interpolation technique which is used to construct monotonic difference schemes for solving the problems for an integral stream function and a level surface. The results of model numerical computations are presented which demonstrate the efficiency of the proposed techniques.Translated by Vladimir A. Puchkin.     

Characteristics of oscillatory-wave processes in solar structures with various magnetic field topology

Recognizing that waves play an important role in energy-exchange processes between layers of the solar atmosphere, and that the characteristics of propagating waves are determined by the physical conditions of the medium, and, most importantly, the magnetic-field configuration, we have carried out a comparative analysis of the properties of oscillations in solar structures with various magnetic-field topologies: sunspots, faculae, and coronal holes. Simultaneous measurements of the Doppler velocities and intensities at the photospheric and chromospheric levels were accompanied by episodic measurements of the longitudinal magnetic field. In the chromosphere, spot umbrae dominate the three-minute oscillations, while lower-frequency modes are also observed in the penumbrae and at the outer parts of spots. Clear signs of propagating waves have been observed at the bases of coronal holes and in faculae only at frequencies close to 3 mHz.     

On the calculation of the barotropic components of motion in models for the general circulation of the ocean

Issues related to the approximation of the stream function and its derivatives are discussed. Model numerical computations are presented, demonstrating the efficiency of the methods under discussion.Translated by Vladimir A. Puchkin. UDK 551.465.110.72; 519.632.4(04).