Yu. Ya. Ruzhin

Seismoionospheric fountain-effect as analogue of active space experiment

Abstract Space investigation includes modelling and initiation of natural processes in ionospheric-magnetospheric plasma by active experimental methods with artificial influence as a specific part. For the first time we present here the possibility of triggering the unique equatorial ionosphere phenomenon known as fountain-effect by lithospheric processes before an earthquake. Anomalous influence of earthquake preparation processes with epicenter close to magnetic equator on latitudinal distribution of foF - F-region penetration frequencies and spread-F is discussed and considered by us as an analogue of an active experiment. Using Alouette-1 data it is shown that approximately one day before the earthquake foF2 dependence on magnetic latitude looks like a double-crest curve with minimum close to epicenter. Simul taneously oblique and spread traces appeared at topside ionograms. The effect is evident during evening hours. Such kind of foF2-dependence is unusual and is not observed during the preceding days, nor some days later. So, a possible reason for the observations might be connected with generation of an anomalous electric field near the epicenter during earthquake preparation stage, which initiates a phenomenon similar to the natural fountain-effect.

Earthquake precursors in magnetically conjugated ionosphere regions

Abstract It is known that the highly conducting geomagnetic field flux tube and quasitrapped energetic particles provide strong electrodynamic coupling between magnetically conjugated regions in the ionosphere. Such a connection is likely to cause ionospheric disturbances before a pending earthquake not only over the epicentral zone but also in the opposite hemisphere. Data from the INTERCOSMOS-18 and ALOUETTE satellites were analyzed from this point of view. Earthquake precursors in magnetically-conjugated ionosphere regions were found in very low frequency (VLF) emission and F2-peak parameters. F2-precursors appear some days before the earthquake, and manifest themselves as an Appleton-type anomaly if the epicenter of the future earthquake is situated near the magnetic equator. Estimation of the electric field magnitude necessary to generate the observed anomaly was made. It was shown that an electric field of less than one mV/m must be generated in the ionosphere. VLF precursors appearance some hours before the earthquake is localized close to the magnetic shell corresponding to the future earthquake epicenter and have a belt-like structure (longitudealigned for more than some tens thousands kilometers) in both hemispheres. VLF precursors are followed by energetic particle (electrons energy W>40 keV) precipitation.

Variations in the Total Electron Content during the Powerful Typhoon of August 5-11, 2006, near the Southeastern Coast of China

The variations in the total electron content (TEC), obtained from the data of 11 ground-based GPS stations in the region (5°S–80°N; 110–160°E) in the period August 2–15, 2006, have been analyzed in order to search for possible ionospheric manifestations of the SAOMAI powerful typhoon (August 5–11, 2006) near the south-eastern coast of China. The global TEC maps (GIM) have also been used. In the region of the typhoon action during the magnetic storm of August 7, 2006, an intensification of the TEC variations in the evening local time within the 32–128 min periods range was detected. However, this effect was most probably caused by the dynamics of the irregular structure of the equatorial anomaly and by the disturbed geomagnetic situation (Kp ∼ 3–6, Dst varied from −74 to −153 nT). The analysis of the diurnal variations in the absolute values of TEC and TEC variations with periods of 2–25 min did not reveal a substantial increase in the intensity and changes in the spectrum of the TEC variations in the period of typhoon action as compared to the adjacent days. Thus, we failed to detect ionospheric disturbances unambiguously related to the SAOMAI typhoon.

Controlled injection of high-power radio pulses into the ionosphere-magnetosphere system and appearance of microsubstorms on October 2, 2007

Insignificant geomagnetic disturbances, which originated during the experimental injection of high-power radio pulses into the magnetosphere-ionosphere system with the help of an HF transmitter of the Sura heating facility, are considered. The experiment was performed at 1840–1900 UT on October 2, 2007 (∼2100 MLT) at geomagnetic latitudes close to the zone of generation of the current wedge westward branch, responsible for geomagnetic substorms. The series of two magnetic microsubstorms, with a sudden initial pulse and an insignificant delay relative to the facility switching, was observed at 1840–2000 UT. A disturbance was registered at many stations in the Northern Hemisphere as a global event. The equivalent ionospheric current system of an initial pulse was similar to such a system of the westward auroral surge and had an intensity maximum at Karpogory magnetic observatory, which is the closest station to the Sura facility. Under the conditions of a quiet solar wind and low planetary geomagnetic activity, the AE auroral index correlated with the interplanetary medium parameters (the correlation coefficient reached 0.65) at 1710–2000 UT. It has been confirmed that an initial geomagnetic pulse is generated as a result of radiowave injection. The arguments for and against the generation of microsubstorms due to stimulated precipitation of magnetospheric electrons, as well as the assumption that the geoeffective impact of the interplanetary medium is intensified during the injection of high-power radiowaves near the zone where the westward branch of the current wedge of magnetospheric substorms is generated, are considered.

Anomalous global plasma structures as seismoionospheric precursors

Abstract The earthquake ionospheric precursors main characteristics are enumerated according to observational results, obtained by different methods. They are inherent to earthquakes magnitudes M≥4 and are observable from several days to several tens of minutes prior to the earthquake in the areas that corresponds to the preparing zone boundary on the Earths surface of some thousands kilometers. As a result three independent arguments in favor of well-known hypothesis about atmospheric electricity variations due to lithospheric processes before earthquake as a possible reason of seismoionospheric precursors are proposed.

Physical mechanism of ionospheric total electron content perturbations over a seismoactive region

A mechanism for the total electron content (TEC) perturbation in the ionosphere during seismic activity strengthening is proposed. The spatial distribution of the TEC perturbation is shown to be determined by the joint effect of the following two factors: the heating of the ionosphere by electric current and the plasma drift in the electric field of this current. The TEC perturbation behavior depends on the relationship between these processes. The current arises in a global electric circuit as the EMF, which is related to the dynamics of charged aerosols injected into the atmosphere, and comes into being in atmospheric surface layers. The developed model allows calculation of the spatial TEC distribution in the ionosphere for a prescribed horizontal distribution of the charged aerosol concentration at the Earth’s surface.

Auroral activity caused by high-power radioemission from the SURA facility

A series of experimental modifications of the ionosphere in the HF range, performed at the SURA facility base, together with optical measurements onboard the International Space Station (ISS), indicated that such impacts on the ionosphere are effective when the facility operational frequency is higher than the critical plasma frequency (for the main ionospheric F2 layer). The experimental measurements were supported by measurements at ground-based observatories, ISS, and the Demeter and GPS satellites. The analysis results of the entire data set are presented. The ray HF radio tracing for the experiment of October 2, 2007, has been calculated, and it has been indicated that the ionosphere to the north of the facility up to 60°–62° N latitudes was irradiated by the facility beam (the effects of ray redistribution and refocusing) due to refraction on the gradient of the F2 layer critical frequencies. An analysis of the ground-based and satellite measurements (both in the vicinity of a heater and in the magnetically conjugate region) indicates that it is possible to trigger a substorm in experiments with the Sura heating facility.

Ionospheric response to the entry and explosion of the South Ural superbolide

The South Ural meteoroid (February 15, 2013; near the city of Chelyabinsk) is undoubtedly the best documented meteoroid in history. Its passage through the atmosphere has been recorded on videos and photographs, visually by observers, with ground-based infrasound microphones and seismographs, and by satellites in orbit. In this work, the results are presented of an analysis of the transionospheric GPS sounding data collected in the vicinity of the South Ural meteoroid site, which show a weak ionospheric effect. The ionospheric disturbances are found to be asymmetric about the explosion epicenter. The received signals are compared, both in shape and amplitude, with the reported ionospheric effects of ground level explosions with radio diagnostics. It is shown that the confident registration of ionospheric effects as acoustic gravity waves (AGWs) by means of vertical sounding and GPS technologies for ground explosions in the range of 0.26–0.6 kt casts doubt on the existing TNT equivalent estimates (up to 500 kt) for the Chelyabinsk event. The absence of effects in the magnetic field and in the ionosphere far zone at distances of 1500–2000 km from the superbolide explosion epicenter also raises a question about the possibility of an overestimated TNT equivalent. An alternative explanation is to consider the superposition of a cylindrical ballistic wave (due to the hypersonic motion of the meteoroid) with spherical shock waves caused by the multiple time points of fragmentation (multiple explosions) of the superbolide as a resulting source of the AGW impact on ionospheric layers.

GPS-based tomographic reconstruction of the ionosphere

Abstract Modern space navigational system GPS Navstar and its Russian analogue GLONASS allow to measure not only phase, but also group delays of the signals propagating through the ionosphere. Possibility of total electron content absolute measurements removes problem of unknown initial phase always existing for phase measurements in 150/400 MHz band but ground-based ionosphere tomography on GPS basis is impossible for realization. To remove these dificulties we offer to replace angular transmitter movement as it is in the case of radiotomography using TRANSIT system by fast moving of a receiver located on board of low-orbital satellite, thus having saved the condition of frozen ionosphere during measurements. For this purposes it is convenient to use independent compact satellites separated from space station ALFA. It is shown that equal inclinations of GPS orbits and orbital system ALFA provide ideal conditions for 2D-radiotomography application. GPS-based tomographic reconstraction provides the possibility to study the ionosphere above the ISS orbit, which is very interesting from a scientific point of view. During some ISS orbits one can map the global structure of the ionosphere which is very useful also for monitoring and forecasting of natural hazards (earthquakes).

The subauroral events generated by rocket launching

Abstract The observations of artificial ionospheric effects due to rockets launching in subauroral zone (L∼4.5) are presented. They were carried out on base of observatories triangle of Arkhangelsk IZMIRAN polygon. Some events in magnetic field and ionospheric parameters variations were revealed. Substorm events characteristics, which might be connected with complex of auroral processes, stimulated by launching, are discussed. This fact would be the evidence of the mankind activity influence on the environment state which manifest itself as a substorm.