Alexey V. Oinats

Statistical characteristics of medium-scale traveling ionospheric disturbances revealed from the Hokkaido East and Ekaterinburg HF radar data

We present a statistical study of medium-scale traveling ionospheric disturbances (MSTIDs) using the Hokkaido East (43.53° N, 143.61° E) and Ekaterinburg (56.42° N, 58.53° E) high-frequency (HF) radar data. Radar datasets are available from 2007 to 2014 for the Hokkaido and from 2013 to 2014 for the Ekaterinburg radar. In the case of the Hokkaido East radar, we have utilized the elevation angle information to study the MSTIDs propagating at the heights of the E and F ionospheric regions separately. We have analyzed the diurnal and seasonal behavior of the following medium-scale traveling ionospheric disturbance (MSTID) parameters: propagation direction, apparent horizontal velocity and wavelength, period, and relative amplitude. The F region MSTID azimuthal patterns were observed to be quite similar by the two radars. The E region northwestward MSTIDs (from 280° to 320°) were typical of summer daytime. Comparison with the horizontal wind model (HWM07) has showed that the dominant MSTID propagation directions match the anti-wind direction well, at least during sunlight hours. We have also found that the wavelength and period tend to decrease with an increase in solar activity. On the contrary, the relative amplitude increases with an increase in solar activity. Moreover, the relative amplitude tends to increase with increasing auroral electrojet (AE) index, as do the wavelength and velocity.

Observations of field-aligned ionospheric irregularities during quiet and disturbed conditions with EKB radar: first results

This paper presents the first results of statistical analysis of 2-year data series obtained with the first midlatitude decameter coherent radar of Russian segment of SuperDARN network. Based on individual events observed on 13–15 December 2013 and 1–4 January 2014, we also demonstrate the possibility of using the radar data for monitoring of magnetosphere-ionosphere dynamics in quiet and disturbed geomagnetic conditions.

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

The possibility of manifestation of tropical cyclones in variations of ionospheric parameters in the zone far removed from the disturbance source region has been studied. The data from frequency analysis by maximal observed frequencies (MOF) for the oblique sounding (OS) signals were used. We revealed 1–5 h time intervals with higher oscillation energetics along the Norilsk–Irkutsk, Magadan–Irkutsk, and Khabarovsk–Irkutsk paths (Eastern Siberia and the Far East of Russia) during equinoctial periods (March, September 2005–2011), in November, 2005 and in summer 2010-2011 for different periods of the solar cycle. These time intervals may be interpreted as a manifestation of large-scale traveling ionospheric disturbances (TIDs) whose sources are atmospheric internal gravity waves. By jointly analyzing ionospheric, heliomagnetic, atmospheric, and satellite data on tropical cyclones (TCs), we attempted to associate the series of the revealed TIDs with ionospheric responses to TCs over the Western North Pacific Ocean during the above periods. A significant increase in wave disturbances on OS paths was established to be noted during active tropical cyclogenesis periods in autumn months. For spring equinox (March, 2005–2011), we also note TID manifestations in MOF time variations under quiet heliomagnetic conditions and in TC absence, but the intensity of these wave disturbances was significantly lower, than that of autumn seasons for various years. We estimated the wavelike disturbance propagation velocity by the delay time of TID passing the medium points of the spaced OS paths.

Study of large-scale traveling ionospheric disturbances using the data of SuperDARN Hokkaido radar and Russian chirp sounding network

In the paper a study of the large-scale traveling ionospheric disturbances observed on March 17, 2007 is presented. The TIDs main parameters were estimated using the data of SuperDARN Hokkaido radar and Russian chirp sounding network separately. The comparison of the estimations shows some discrepancies in propagation direction that can be explained by convex shape of the TIDs front.

The technique for calculating of HF-signals characteristics taking into consideration ionosphere waveguide propagation

A technique based on the waveguide approach for calculating ionosphere oblique-incidence sounding signal characteristics and taking account of ionosphere waveguide excitation is offered. Comparison of our calculation results and experimental ionograms on the path Alice-Springs (Australia) rkutsk (Russia) is given.