Spectral peculiarities of high energy X-ray radiation,gamma radiation,and Submillimeter radio emission in the impulsive phase of a solar flare

We analyze experimental data on the temporal behavior of fluxes and energy spectra of hard solar X-ray and gamma radiation in the energy range of 0.015 to 300 MeV, obtained onboard the CORONAS-F satellite during a solar flare on August 25, 2001. These data are compared with measurements of the radio emission fluxes over the wide frequency range of 1–405 GHz. For our analysis, we use data obtained onboard the YOHKOH, TRACE and GOES satellites, along with ground-based observations of this solar event using the Solar Submillimeter Telescope (SST; Argentina). For the first time, we find nearly simultaneous changes in the energy spectra of gamma radiation over the range 10–150 MeV and the frequency spectrum of radio emission at the beginning and during a impulsive phase of this event (whose duration did not exceed three minutes).     

Diagnostics of the HF-pumped ionospheric region using wide-band radio emission

We present the results of comprehensive studies of the spatio-temporal structure of the artificial ionospheric plasma turbulence created by powerful radio emission over the “Sura” heating facility. The elaborated methods of the transmitter-receiver operation control, wide-band signal recording, digital filtering and spectral analysis of the stimulated electromagnetic emissions and short radio pulses are used for diagnostics. Novel data are obtained on the evolution of the Langmuir and upper-hybrid turbulence spectrum, the altitude distribution of the plasma wave decay rates, and the amplitude-phase characteristics of the test signals under wide-band sounding of the ionospheric plasma. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 8, pp. 649–668, August 2007.     

Modeling VHF emissivity of snow cover with account of its stratigraphy

In this paper, we discuss a model of emissivity of snow cover taking into account its structure. We assume that upward and downward radiation inside a snow layer are diffuse and apply the two-flux theory of Kubelka and Munk. Snow cover is modelled by a medium comprising discrete scatterers. In the case of dry snow, the scatterers are ice grains. Wet snow is modelled by a mixture of ice grains (with or without water envelopes) and water drops. We assume that the scatterers are spherical particles that have lognormal distribution over size. The brightness temperature of radio emission from snow cover on the soil is calculated using the data of glaciological measurements of physical parameters and microstructure of snow. Results of calculations are compared to measurements of the brightness temperature of radio emission from various types of snow covers. Space Research Institute of Russian Academy of Sciences, Moscow, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 9, pp. 845–857, August 1999.     

Modification of the earth’s ionosphere by high-power HF radio emission: Artificial periodic inhomogeneities and the sporadic <Emphasis Type="Italic">E</Emphasis> layer

We present the results of new studies of the sporadic E layer in the case of heating of the ionosphere by high-power HF radio emission. The measurements were performed at the “Sura” heating facility. Ionosphere was modified by high-power radio emission from the “Sura” facility and was sounded by the probing radio waves of the same frequency and mode. The heating of the ionosphere resulted in the formation of artificial periodic inhomogeneities, and an increase in the intensity of all signals scattered by the D, E, and F regions and the sporadic E layer by 5–20 dB was observed. The increase was observed during heating of the ionosphere by each magnetoionic component, but was smaller for heating by an ordinary-mode wave. This effect was resonant and disappeared as a result of the frequency detuning down to 85 kHz. During the ionospheric modification, the signal-intensity increased due to modulation of the natural profile of the electron number density by the artificial periodic structure. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 8, pp. 695–708, August 2007.     

Nulling Phenomenon of the New Radio Pulsar J0810+37 at a Frequency of 111 MHz

Pulsar J0810+37 with a period of 1.2483 s is detected at a frequency of 111 MHz during the pulsar search at the Big Scanning Antenna (BSA) radio telescope of the Lebedev Physical Institute [1]. In this paper, we present the results of the detailed study of radio emission from J0810+37 which exhibits a rare nulling effect of different durations in a very wide time interval with an average nulling fraction in “switch-on” days 〈NF〉 = 38%; considering “switch-off” days, 〈NF〉 = 74%, since radio emission from this source is interrupted on average by 2–3 days, and then it again revives on average for 1–2 days. The “switch-off” periods reach 7 days.     

Ground-based microwave thermal sounding of the atmosphere

We apply the tensor transfer equation for downward radio emission in a weakly anisotropic medium and a generalized analysis of the generation conditions for such radiation to develope a unified approach to the solution of the problem on reconstruction of the atmospheric temperature prifile over a wide altitude range (from theoustasche layer to the mesosphere) using ground-based measurements of thermal radio emission. Radio emission in the oxygen spin—rotational band centered at the wavelength 5 mm was measured with radiometer equipment of various spectral resolutions. The capabilities of the remote sounding are illustrated by the results of the temperature profile reconstruction in theoustasche layer and troposphere using the radiometric measurements of the atmospheric radio emission, as well as by the results of numerical simulations of the radiometric experiment for the upper layers of the atmosphere. Trends in development of ground-based remote sounding of the temperature are discussed. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 1, pp. 45–59, January, 1999.     

Electromagnetic and plasma perturbations induced by radio emission of the EISCAT high-frequency heating facility in the outer ionosphere of the earth

We present the results of measuring the characteristics of electromagnetic and plasma perturbations at the altitudes of the Earth’s outer ionosphere, which were obtained by the onboard equipment of the French microsatellite DEMETER when it passed through the magnetic flux tube based on a region modified by high-power HF radio emission of the EISCAT heating facility. Physical mechanisms which allow one to explain the observed phenomena are considered. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 11, pp. 925–933, November 2008.     

New Results of Studying the Lower Ionosphere by the Method of Resonance Scattering of Radio Waves from Artificial Periodic Inhomogeneities

We present the results of studying the lower ionosphere in 2000–2004 at the “Sura” heating facility by the method of resonance scattering of radio waves from artificial periodic inhomogeneities of the ionospheric plasma. Experimental data on a study of the sunset–sunrise phenomena in the ionospheric D region and the possibility of determining the concentrations of atomic oxygen and excited molecular oxygen are discussed. The results of studying the sporadic layers of ionization are presented and the method for a study of ion composition of the E_s layer is discussed. Data of the August 2004 experiments on a study of the influence of heating the ionosphere on the E_s layer and characteristics of artificial periodic inhomogeneities are presented. Prospects for further research are discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 757–771, September 2005.     

Calibration of the solar radio spectrometer

This paper shows some improvements and new results of calibration of Chinese solar radio spectrometer by analyzing the daily calibration data recorded in the period of 1997–2007. First, the calibration coefficient is fitted for three bands (1.0–2.0 GHz, 2.6–3.8 GHz, 5.2–7.6 GHz) of the spectrometer by using the moving-average method confined by the property of the daily calibration data. By this calibration coefficient, the standard deviation of the calibration result was less than 10 sfu for 95% frequencies of 2.6–3.8 GHz band in 2003. This result is better than that calibrated with the constant coefficient. Second, the calibration coefficient is found in good correlation with local air temperature for most frequencies of 2.6–3.8 GHz band. Moreover, these results are helpful in the research of the quiet solar radio emission.     

Variability of the atmospheric N2O line (J=3→4)

We analyze the results of observations of the radio emission of atmospheric N₂O in the line J=3→4 at frequency near 100.5 GHz. Observations aimed at monitoring the nitrous oxide content at altitudes h>20 km were performed in Nizhny Novgorod from March to May, 1997. We discover variations of the optical-depth decrement in the line, which can be explained by the redistribution of nitrous oxide over the altitude range h=20–55 km. This assumption does not contradict published data on in-situ measurements of N₂O density at h=5–35 km. Using the obtained data we calculate the rotational-line spectra of atmospheric N₂O. We point out that the measured decrements of the optical depths are greater than the calculated ones. We discuss observations of the N₂O lines in the mm-wave band as a promising method for monitoring the vertical mixing in the atmosphere. N. I. Lobachevsky State University, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 10, pp. 933–939, October 1999.     

Calculation of spatial intensity distribution of InAsSb/InAsSbP laser diode emission

The spatial distribution of emission intensity in the active layer of a laser diode (LD) based on an InAsSb/InAsSbP heterostructure (generation wavelength λ_gen ∼ 3.3 μm) is obtained for various stripe widths w by means of numerical solution of the wave equation in the 2D approximation taking into account the refractive index nonlinearity. It has been shown that the special distribution of emission intensity becomes strongly inhomogeneous at w values exceeding 9–10 μm, which results in the appearance of additional maxima in the far-field pattern. Calculated far-field patterns in the active layer plane of the LD agree with corresponding experimental data. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 804–808, November–December, 2008.     

Some results of measuring the characteristics of electromagnetic and plasma disturbances stimulated in the outer ionosphere by high-power high-frequency radio emission from the “Sura” facility

We present the results of measuring the characteristics of electromagnetic and plasma disturbances at altitudes of about 700 km, obtained by using the onboard equipment of the French microsatellite DEMETER during its passage through the magnetic tube resting upon the region of intense generation of artificial ionospheric turbulence created due to modification of the ionospheric F₂ region by high-power radio emission from the “Sura” facility. It is shown that an artificial density duct emerging from the disturbed region and extending to the Earth’s magnetosphere can be formed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 8, pp. 709–721, August 2007.     

Results of studying the sporadic <Emphasis Type="Italic">E</Emphasis> layer by the method of resonant scattering of radio waves by artificial periodic inhomogeneities of the ionospheric plasma

We report on the results of studying the lower ionosphere by a method based on the resonant scattering of radio waves by artificial periodic inhomogeneities of the ionospheric plasma. Different aspects of studying the sporadic E layer such as the influence of the vertical transfer on its formation, the possibility of examination of its ion composition, and the influence of the ionosphere heating on the layer characteristics are discussed. The results of determining the parameters of the E _s layer and some characteristics of the lower ionosphere during the creation of artificial periodic inhomogeneities at two frequencies are presented. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 11, pp. 956–969, November 2008.     

RT-2 radio telescope of the Ussuriysk Astrophysical Observatory: current state and observation data

An RT-2 radio telescope of the Ussuriysk Astrophysical Observatory (UAO) is intended for measuring the total flux of solar radio emission at a frequency of 2.804 GHz. Regular observations have been carried out in the UAO since 1990. The current state of the instrument and the data survey for the observation years are presented. The emphasis is on the transition to digital registration of the radio flux in 2002, which offers new opportunities of the data analysis. Digital recording allows us to improve the accuracy of the daily radio-flux measurements, ensures their comparison with the data of the integral radio emission at other frequencies, and provides for reconstruction of the time profiles of powerful radio bursts. Possible problems which can be solved using the UAO radiometer data are outlined. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 12, pp. 1005–1010, December 2008.     

Results of Determining the Electron Number Density in the Ionospheric E Region from Relaxation Times of Artificial Periodic Irregularities of Different Scales

We present the first results of determining the electron number density in the ionospheric E region by a novel technique based on the creation of artificial periodic irregularities when the ionosphere is affected by powerful radio emission at two frequencies. Using the results of the measurements performed in October 2006 during heating of the ionosphere by the “Sura” facility radiation at frequencies 4.7 and 5.6 MHz, we obtained the electron number density profiles in an altitude range of 100 to 110 km. Features of the procedure of measurement and calculation of the electron number density are described in detail. It is shown that the method can be used for a study of the irregular structure of the lower ionosphere. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 6, pp. 477–484, June 2008.     

Features of limb sounding of minor atmospheric constitutents at various microwave lines

We analyze the characteristics of radio emission from the middle atmosphere during limb sounding of minor gas constituents with rotational transitions of the molecules located in the atmospheric transparency windows 105–118 GHz and 180–210 GHz. Optimal frequencies and height ranges for the sounding of minor gases are found by numerical modeling for typical values of the receiver bandwidth. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 3, pp. 235–239, March 1999.     

Phase Fluctuations of Radio Waves Behind a Turbulent Phase Screen

We consider the problem of phase fluctuations of radio waves behind a turbulent optically thin irregular layer (phase screen). Expressions are derived for the main statistical characteristics of phase fluctuations in the case where modern direct methods based on measurements of the complex field of the received radiation are used to obtain these characteristics. Regimes of weak and saturated scintillations of signals are analyzed. It is shown that in the case of weak scintillations, such statistical characteristics of phase fluctuations of the received radiation as the structure function and the fluctuation spectra for single-point and interference reception almost coincide with those at the screen output. In the regime of saturated scintillations, we obtain an information on the structure function of phase fluctuations of the received radiation in the cases of relatively large and small spatial separations of the reception points. The results obtained allow one to correctly analyze the data of modern experiments on remote sensing of the near-Earth and space plasmas with the help of direct phase methods for environmental diagnostics. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 7, pp. 563–573, July 2005.     

Experimental determination of physical processes in space,leading to deviations of radio synchrotron radiation spectra from the power law

We present universal formulas for spectral characteristics of cosmic radio sources of synchrotron radiation upon the presence of spectral density maxima at certain frequencies (spectra with negative curvature) taking into account most typical physical processes observed in space. On the basis of long-term observations of angular radiation structure of cosmic radio sources in the decameter wavelength range by the URAN radio interferometer system, we determine most probable physical processes resulting in spectra with extremum values for several quasars, radio galaxies, and their separate components. On the basis of these data, we estimate some parameters of cosmic medium, magnetic field, and angular sizes of compact radio sources and their components. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 2, pp. 91–110, February 2008.     

Sounding of an artificially perturbed ionosphere by means of an ionosonde/position finder with chirp modulation of the signal

We describe the operation of an ionosonde/position finder with chirp modulation of the signal. The first results of measuring the characteristics of short-wave radio signals scattered by artificial small-scale inhomogeneities, which were obtained by means of an ionosonde/position finder on the IZMIRAN—“SURA”—Rostov-on-Don path are presented. It was found that under certain ionospheric conditions, the angular and frequency selection of the scattered signals take place, in which case the signals are observed simultaneously in several frequency intervals (mainly, in three, namely, 6–9.5 MHz, 10–12 MHz, and 15–18 MHz) with different angles of incidence of radio waves in the vertical plane. In this case, the incidence angles were 20◦–35◦, 18◦–32◦, and 10◦–20◦ from the horizon for the first, second, and third frequency interval, respectively. Ionograms of oblique sounding were modeled allowing for the scattering of radio waves by artificial small-scale inhomogeneities. It is shown that at frequencies from 10 to 12 MHz, aspect conditions are fulfilled for the signals ducting along the high-angle beam (Pedersen mode). At frequencies 15–18 MHz (higher than the maximum observable frequency of the forward signal on the path IZMIRAN—Rostov-on-Don), aspect scattering conditions are fulfilled for the signals incident on a scattering area in the ascending part of the trajectory. At low frequencies 6–9.5 MHz (below the maximum observed frequency of the forward signal on the IZMIRAN—Rostov-on-Don path), the observable additional signals are caused by the scattering of radio waves by artificial inhomogeneities with subsequent relfection of the scattered signal from the Earth on the “SURA”—Rostov-on-Don path. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 4, pp. 267–278, April 2009.     

Nanostructure model and optical properties of InAs/GaAs quantum dot in vertical cavity surface emitting lasers

We apply 8-band k.p model to study InAs/GaAs quantum dots (QDs). The strain was calculated using the valence force field (VFF) model which includes the four nearest-neighbour interactions. For the optical properties, we take into account both homogeneous and non-homogeneous broadening for the optical spectrum. Our simulation result is in good agreement with the experimental micro-photoluminescence (μ-PL) result which is from InAs/GaAs QD vertical cavity surface emitting lasers (VCSELs) structure wafer at room temperature. Accordingly, our simulation model is used to predict the QD emission from this QD-VCSELs structure wafer at different temperature ranging from 200–400 K. The simulation results show a decrease of 41 meV of QD ground state (GS) transition energy from 250–350 K. The changes of QDGS transition energy with different temperature indicate the possible detuning range for 1.3-μm wave band QD-VCSELs applications without temperature control. Furthermore, QD differential gain at 300 K is computed based on this model, which will be useful for predicting the intrinsic modulation characteristics of QD-VCSELs.