High-frequency seismo-electromagnetic effects

Some statistical results on very low frequency radiowave emissions in the upper ionosphere over earthquake zones

The zone of anomalous diurnal variations in foF2, which is characterized by an excess of nighttime foF2 values over daytime ones, has been distinguished in the Southern Hemisphere based on the Intercosmos-19 satellite data. In English literature, this zone is usually defined as the Weddell Sea anomaly (WSA). The anomaly occupies the longitudes of 180°–360° E in the Western Hemisphere and the latitudes of 40°–80° S, and the effect is maximal (up to ∼5 MHz) at longitudes of 255°–315° E and latitudes of 60°–70° S (50°–55° ILAT). The anomaly is observed at all levels of solar activity. The anomaly formation causes have been considered based on calculations and qualitative analysis. For this purpose, the longitudinal variations in the ionospheric and thermospheric parameters in the Southern Hemisphere have been analyzed in detail for near-noon and near-midnight conditions. The analysis shows that the daytime foF2 values are much smaller in the Western Hemisphere than in the Eastern one, and, on the contrary, the nighttime values are much larger, as a result of which the foF2 diurnal variations are anomalous. Such a character of the longitudinal effect mainly depends on the vertical plasma drift under the action of the neutral wind and ionization by solar radiation. Other causes have also been considered: the composition and temperature of the atmosphere, plasma flows from the plasmasphere, electric fields, particle precipitation, and the relationship to the equatorial anomaly and the main ionospheric trough.

Morphology and causes of the Weddell Sea anomaly

. We present a statistical study of variations in the F2-layer peak electron density, NmF2, and altitude, hmF2, over the Argentine Islands ionosonde. The critical frequencies, foF2, and, foE, of the F2 and E-layers, and the propagation factor, M(3000)F2, measured by the ionosonde during the 1957–1959 and 1962–1995 time periods were used in the statistical analysis to determine the values of NmF2 and hmF2. The probabilities to observe maximum and minimum values of NmF2 and hmF2 in a diurnal variation of the electron density are calculated. Our study shows that the main part of the maximum diurnal values of NmF2 is observed in a time sector close to midnight in November, December, January, and February exhibiting the anomalous diurnal variations of NmF2. Another anomalous feature of the diurnal variations of NmF2 exhibited during November, December, and January when the minimum diurnal value of NmF2 is mainly located close to the noon sector. These anomalous diurnal variations of NmF2 are found to be during both geomagnetically quiet and disturbed conditions. Anomalous features are not found in the diurnal variations of hmF2. The statistical study of the NmF2 winter anomaly phenomena over the Argentine Islands ionosonde was carried out. The variations in a maximum daytime value, R, of a ratio of a geomagnetically quiet daytime winter NmF2 to a geomagnetically quiet daytime summer NmF2 taken at a given UT and for approximately the same level of solar activity were studied. The conditional probability of the occurrence of R in an interval of R, the most frequent value of R, the mean expected value of R, and the conditional probability to observe the F2-region winter anomaly during a daytime period were calculated for low, moderate, and high solar activity. The calculations show that the mean expected value of R and the occurrence frequency of the F2-region winter anomaly increase with increasing solar activity.

/pdf/anomalous-variations-of-nmf2-over-the-argentine-islands-a-3h53pdtgj4.pdf

Anomalous variations of NmF2 over the Argentine Islands: a statistical study

A short review is given of the contemporary concepts and controversies concerning the electromagnetic effects observed in space which are considered to be the results of energy transport from surface and/or lower atmosphere. A concept of a parametric amplifier in the stratosphere-mesosphere was recently suggested by the authors (1996) from the reanalysis of the experimental results from the AUREOL-3 satellite during active experiments MASSA with ground chemical explosions. Electric discharges in the stratosphere-mesosphere medium were suggested as a mechanism for this parametric amplifier. Such discharges, or localized electric current bursts in the Alfven wave frequency scale (∼0.1–1 s−1), could also play a role as a mechanism of effective energy transport from the surface to space layers. Among the possible EQ precursor effects, some can be related to local atmospheric electricity variations such as emanations of gas and/or aerosols, conductivity changes in the lower atmosphere, or non-linear combinations of acoustic waves with a meteor ionization channel. Thus a multidisciplinary search of EQ precursors, especially with regard to atmospheric electricity variations, lightning-type, or slower discharges related to meteor ionization, seems to be among the ways to deepen the understanding of the complicated relations between different layers of atmosphere and magnetosphere.

/pdf/on-a-possibility-of-parametric-amplifier-in-the-stratosphere-4d32p1okds.pdf

On a possibility of parametric amplifier in the stratosphere-mesosphere suggested by active MASSA experiments with the AUREOL-3 satellite

Very low frequency and ELF effects in the upper ionosphere caused by large-scale acoustic waves in the lower ionosphere observed from AUREOL-3 satellite

Y. V. Lissakov

Papers

Very low frequency and ELF effects in the upper ionosphere caused by large-scale acoustic waves in the lower ionosphere observed from AUREOL-3 satellite

Observations of low intensity particle fluxes inside the region of the ionospheric main trough and their variability