The Siberian Solar Radio Telescope: the current state of the instrument,observations, and data

The Siberian Solar Radio Telescope (SSRT) is one of the world's largest solar radio heliographs. It commenced operation in 1983, and since then has undergone several upgrades. The operating frequency of the SSRT is 5.7 GHz. Since 1992 the instrument has had the capability to make one-dimensional scans with a high time resolution of 56 ms and an angular resolution of 15 arc sec. Making one of these scans now takes 14 ms. In 1996 the capability was added to make full, two-dimensional images of the solar disk. The SSRT is now capable of obtaining images with an angular resolution of 21 arc sec every 2 min. In this paper we describe the main features and operation of the instrument, particularly emphasizing issues pertaining to the imaging process and factors limiting data quality. Some of the data processing and analysis techniques are discussed. We present examples of full-disk solar images of the quiet Sun, recorded near solar activity minimum, and images of specific structures: plages, coronal bright points, filaments and prominences, and coronal holes. We also present some observations of dynamic phenomena, such as eruptive prominences and solar flares, which illustrate the high-time-resolution observations that can be done with this instrument. We compare SSRT observations at 5.7 GHz, including computed `light curves', both morphologically and quantatively, with observations made in other spectral domains, such as 17 GHz radio images, Hα filtergrams and magnetograms, extreme-ultraviolet and X-ray observations, and dynamic radio spectra.     

Formation and cooling of the giant HXIS arches of November 6–7, 1980

Giant arches, first detected by the HXIS instrument aboard SMM, are still a poorly understood component of the flare scenario. Their origin remains uncertain and their behavior, quite different in separate events, has not yet been satisfactorily explained. The purpose of the present paper is to analyze the giant arches imaged on November 6–7, 1980, which, in contrast to that observed on May 21, 1980, were not stationary and had shorter cooling times. In particular, we use a procedure, already applied to the May 21 case, to compute the three-dimensional topology of the magnetic field which forms by reconnection over the active region containing the November arches. This technique allows us to verify that the observed structures are aligned with the computed field lines, lending support to the hypothesis that they originate through a reconnection process which occurs at progressively larger altitudes. Moreover, a calculation of the magnetic energy liberated by reconnection shows that enough energy may be thereby released to account for the observed thermal energy enhancement of the HXIS arches. Finally, the lifetime of the features is shown to be consistent with that predicted by cooling via radiation and field-aligned conduction to the underlying chromosphere.     

BACODINE,the real-time BATSE gamma-ray burst coordinates distribution network

The celestial coordinates of gamma-ray burst sources observed with BATSE on GRO are automatically determined and distributed in real time to members of the global scientific community. These data are now being used by more than 20 operations to enable searches for associated transients in a variety of other wavelength or energy regimes to identify the burst source objects. The minimum total delay time from the onset of a burst to the receipt of its coordinates by distant experimenters can be under 4 sec, less than the duration of a typical GRB, and the maximum total delay is 7 sec, or longer, depending on the distribution method. Some improvements to the BACODINE system and a summary of the follow-up observations made by some of the sites are given.     

Cosmological implications of BL Lac objects

It has become clear in recent years that relativistic beaming is a good explanation for the BL Lac phenomenon. Of studies based on the relativistic beaming model of BL Lac objects, we note that the orientation of jet's axis to the line-of-sight is very small and, therefore, the observed flux emitted from a rapidly moving source is orders of magnitude higher than the flux in its rest-frame:F _obs = ^{3 +} F _intr, where is the bulk relativistic Doppler factor. Then the observed apparent magnitudem _v must be corrected for this effect. For our 39 samples, the corrected apparent magnitudem _v ^corr and logZ have a good correlation.     

Equilibrium temperatures of interstellar iron grains

Because of the relatively low number densities found in typical interstellar clouds, molecules observed there must be produced by a combination of both two-body gas-phase reactions and surface reactions. The latter type includes various catalytic reactions, such as the formation of H₂ on transition metal grains. These reactions are very temperature dependent, the grain temperature appearing in the exponential of the rate equations. Because of the small heat capacities of the grains due to their small sizes, they may be subject to considerable fluctuations in temperature. This problem is examined for iron grains and found to be minimal for sizes greater than 100 Å. Steady-state equilibrium temperatures are then calculated for a size distribution of iron particles ranging from 10³ to 10⁹ atoms per grain by a refined method of an earlier work by one of us (RGT). The results are that iron grain temperatures are significantly greater than those of dielectric grains of comparable size in the same radiation field.     

Detection of radio recombination lines of hydrogen ionized by cosmic-ray protons in the cool interstellar medium

The emission of hydrogen radio recombination lines from a cloud of cool interstellar matter toward the radio source Cassiopeia A has been detected. The formation of the radio recombination lines is initiated by cosmic rays. The rate of ionization of the interstellar hydrogen by cosmic-ray protons measured from the radio recombination lines using the most direct method is ζ_H = (1 ± 0.25)×10⁻¹⁶ s⁻¹. This value of ζ_H is compared with measurements obtained using other methods.     

Organized Roll Circulation and Transport of Mineral Aerosols in the Atmospheric Boundary Layer

Izvestiya, Atmospheric and Oceanic Physics - An investigation into mesoscale roll circulation and its transport characteristics in the atmospheric boundary layer (ABL) is carried out. The case...     

On the infrared observations of stellar flares

In connection with the appearance of the first results of infrared observations of stellar flares, a more elaborate analysis ofnegative infrared flares as a phenomenon, predicted by the fastelectron hypothesis, has been carried out. As a result, the wavelength regions of negative flares are established for the stars of different spectral types as well as the calculated amplitudes of the negative flares (Tables I and II). The analysis of the infrared observations (c.f. Kilyachkoet al., 1978) lead to the following conclusions:

1. The negative infrared flares discovered around 8000 Å is not in agreement with the theory in the case of the flare star UV Cet. Some traces of negative flares have been noted for a number of less powerful flares of EV Lac.
2. The amplitudes of the recorded positive flares of UV Cet and EV Lac on λ8000 Å are in good agreement with the magnitudes predicted by the fast-electron hypothesis (non-thermal bremsstrahlung).
3. In the future the negative flares around 8000 Å should be looked for in early-type flare stars of types M0-K5.
4. For a positive discovery of negative flares, future observations must be carried out in the wavelength region of 1–3 μm.