Vladimir I. Kurkin

Solar activity variations of nighttime ionospheric peak electron density

[1] Monthly median NmF2 (maximum electron density of the F2-layer) data at Okinawa, Yamagawa, Kokubunji, and Wakkanai have been collected to investigate the solar activity dependence of the nighttime ionosphere. The result shows that there are seasonal and latitudinal differences of the solar activity variation of nighttime NmF2. The main seasonal effects are as follows: nighttime NmF2 increases with F107 linearly in equinoctial months (March and September), and it tends to saturate with F107 increasing in summer solstice month (June). What is peculiar is that there is an amplification trend of nighttime NmF2 with F107 in winter solstice month (December). The latitudinal difference is mainly displayed by the evolvement course of the variation trend between NmF2 and F107. Using hmF2 (peak height of the F2-layer) data and the NRLMSISE00 model, we estimated the recombination loss around the F2-peak at different solar activity levels. We found that the solar activity variation of the recombination processes around the F2-peak also shows seasonal dependence, which can explain the variation trends of nighttime NmF2 with F107 qualitatively, and field-aligned plasma influx plays an important role in the equatorial ionization anomaly (EIA) crest region. During the first several hours following sunset in December, there are faster recombination processes around the F2-peak at medium solar activity level in mid-latitude regions. This feature is suggested to be responsible for inducing the amplification trend in winter. In virtue of the calculation of neutral parameters at 300-km altitude and hmF2 data, the variation trend of the recombination processes around the F2-peak with F107 can be explained. It shows that both the solar activity variations of hmF2 and neutral parameters (neutral temperature, density, and vibrational excited N2) are important for the variation trend of nighttime NmF2 with F107. Furthermore, the obvious uplift of hmF2 at low solar activity level following sunset in December is important for the amplification trend.

Ionospheric effects of magnetospheric and thermospheric disturbances on March 17–19, 2015

Using vertical and oblique radio-sounding data, we analyze the ionospheric and thermospheric disturbances during the magnetic storm that occurred in northeastern Russia on March 17–19, 2015. We consider the heliospheric sources that induced the magnetic storm. During the main and early recovery phases, the midlatitude stations are characterized by extremely low values of electron density at the F2 layer maximum. Using oblique sounding data, we recorded signals that propagated outside the great circle arc. In evening and night hours, no radio signals were found to pass along the Norilsk–Irkutsk and Magadan–Irkutsk paths. The observed ionospheric effects are shown to be caused by a sharp shift of the boundaries of the main ionospheric trough to the invariant latitude 46° N during the main phase of the magnetic storm. The negative ionospheric disturbance during the recovery phase of the storm, which was associated with significant variations in the composition of the neutral atmosphere, led to a change in the mode composition of received radio signals and a decline in observed maximal frequencies in daytime hours of March 18, 2015 by more than 2 times.

Observations of abnormally powerful scattering with ISTP IS radar

We present the coherent echo observation results obtained by Irkutsk Incoherent Scatter radar during September 25, 1998 ionospheric storm. It is shown that during that time we have observed scattering from irregularities elongated with Earths magnetic field and located in the E-region of ionosphere. A good correlation between vertical component of magnetic field disturbance and logarithm of received power was found.

Hydrogenated Zr-Fe alloys encapsulated in Al2O3/Al matrix as catalysts for Fischer-Tropsch synthesis

Abstract The genesis of the ZrFe intermetallides with different atomic ratios during preparation of Zr y Fe z H y /Al 2 O 3 /Al catalysts and their performance in Fischer-Tropsch synthesis has been studied. The effect of structural, surface and textural properties on their activity had have been discussed.

The March 9, 1997 solar eclipse ionospheric effects over the Russian asian region

Abstract The ionospheric response to the total solar eclipse of 1997 March 9 was considered on the database of some ionosondes (longitudinal chain) and Irkustsk incoherent scatter radar. The deviations of ionospheric parameters as a consequence of solar eclipse effect during the rise period and at noon were determined experimentaly. Maximum deviation of plasma density in comparison with quiet conditions reached up to 50 % for the rise period and about 70% for noon near the peak height of the F2 region (∼200 km). The greatest change electron temperature occurred at heights ∼300 km and reached 30%.

Using IRI-95 in FMCW signal simulation

Abstract A ray tracing code for long distance propagation via the ionosphere has been established and applied with electron density profiles taken from IRI-90 and -95. The theoretical results for different distances were compared with experimental ones obtained by Chirp ionosonde techniques. When comparing maximum observable frequencies good agreement was found even with a transequatorial path.

Vertical ionosphere sounding using continuous signals with linear frequency modulation

Consideration of the digital chirp sounder design for the modern systems of a geophysical monitoring, communication channels state forecasting and the research problems solution is given. Given the comparative results of pulsed and of continuous signal vertical sounding ionosondes.

Vertical midscale ionospheric disturbances caused by surface seismic waves based on Irkutsk chirp ionosonde data in 2011–2016

Based on the Irkutsk fast monostatic chirp ionosonde data we made a statistical analysis of ionospheric effects for 28 earthquakes which appeared in 2011-2016 years. These effects are related with surface (Rayleigh) seismic waves far from epicenter. The analysis has shown that nine of these earthquakes were accompanied by vertical midscale ionospheric irregularities (multicusp). To estimate the ionospheric efficiency of the seismic waves we proposed new index

Lidar and satellite temperature measurements during the sudden stratospheric warmings over Siberia and the Russian Far East in 2008–2012

K_{W}

Ionosphere effects of tropical cyclones over the Asian region of Russia according to oblique radio-sounding data

. The index estimates the maximal amplitude of the acoustic shock wave generated by given spatial distribution of seismic vibrations and related with maximal spectral power of seismic oscillations. Based on the analysis of experimental data we have shown that earthquake-related multicusp is observed mostly at daytime [07:00-17:00]LST for