Irkutsk Incoherent Scatter Radar Research Articles

Studying magnetospheric disturbances accompanied by midlatitude coherent echo signals

The results of an analysis of midlatitude coherent echo, registered with the Irkutsk incoherent scatter radar during 53 observational seances, are presented. The observations continued for 4358 h from January 1998 to January 2005. Echo signals revealed during an analysis are divided into two groups with respect to power: strong (s) and weak (w) echoes. It was detected that echo signals with coherent echo characteristics are observed during all local time hours and at different levels of geomagnetic activity. The probability of s-echo appearance is minimal in noon hours and is maximal in post-midnight-morning hours. It has been indicated that the longest and strongest coherent echoes are observed at midlatitudes during great magnetic storms at an increased dynamic pressure of the solar wind.

An investigation of ionospheric disturbances over the north-eastern region of Russia in October 2003 using auroral images and data from a network of ground-based instruments

This paper presents the results of analyzing the experimental data from the Irkutsk incoherent scatter radar, GPS receiver in Yakutsk, digital ionosounders for vertical- and oblique-incidence sounding combined with auroral images during geomagnetic disturbances as a consequence of high flaring activity of the Sun from 19 to 29 of October, 2003. Overall the observations can be interpreted in terms of the thermosphere storm model and main ionospheric trough motion. At once the negative critical frequency disturbance observed during the major storm on October 29 can not be explained in terms of the noted models.

Response of ionosphere to the great geomagnetic storm of September 1998: Observation and modeling

We present the results derived from investigating of the ionospheric effects of the great geomagnetic storm on September 24–27, 1998 based on analyzing the data obtained at ionospheric stations located in the region of Siberia and the Far East. For the sake of comparison we have also introduced the data from some European stations. In addition to the vertical-incidence sounding data the measurements from the Irkutsk incoherent scatter radar are used. It is obtained that the intense negative disturbances during the main phase of the storm are observed at all stations under investigation. A comparison of the foF2 variations for the two meridians shows that even with a relatively small difference of longitudes (45°), the recovery phase has substantial differences of ionospheric disturbances. On September 26, the positive disturbances are observed and persist the following day at all stations except Salekhard and the Norilsk chain. At the Norilsk chain and at Salekhard the negative disturbances recurred after positive disturbances. The sign reversal of disturbance during the recovery phase extends over in the further displacement from the west to the east. An interpretation of the measurements includes their comparing with the results of calculations in terms of a numerical model of the ionosphere and plasmasphere. The modeling results are in the satisfied agreement with the measurements. According to the model calculations the sign of the ionospheric disturbance is changed from negative to positive as the result of combined effects of corpuscular and photo ionization. The sign of ionospheric disturbance is determined by a local time at which the magnetic storm has begun.

The comparison of incoherent scatter data with IRI-2001 in East-Siberian region

The paper deals with the comparison of observations by the Irkutsk incoherent scatter radar (ISR) during the period of 1998–2003 with predictions of the International Reference Ionosphere model, IRI-2001. For the comparison, we used data for only magnetically calm days ( K p ⩽ 4). Our study showed: (1) good agreement between IRI and ISR data during the equinoxes for the electron density N e, electron temperature T e and ion temperatures T i; (2) during daytime hours in summer the model overestimates the measured electron densities by 30–50% and underestimates the electron temperatures by 400–800 K, in winter, on the other hand, the model predictions of electron density are lower by 15–25% and are larger than the measured electron and ion temperatures; (3) during winter the radar shows a night enhancement in N e at predawn, while the model predicts a weak enhancement near midnight.