G.A. Zherebtsov

Regular changes in the critical frequency of the F2 layer of the quiet midlatitude ionosphere

A method for constructing the empirical model of the F2 layer critical frequency (foF2) under magnetically quiet conditions, aimed at analyzing disturbances of any nature, is proposed. This method has been analyzed, and typical features of regular changes in foF2 of the quiet ionosphere and day-to-day foF2 variability are analyzed using the data from Irkutsk and Slough stations as an example. In particular, it has been obtained that this model differs from the international IRI model, and this difference is mainly caused by the fact that the foF2 values in the IRI model do not correspond to quiet conditions. Therefore, this model gives a larger amplitude of the annual and semiannual variations in foF2 than the IRI model. In addition, this model more accurately reproduces the rate of foF2 annual variations at a fixed local time, especially in equinoxes, when foF2 variations can exceed 1 MHz within one month.

Variability of parameters of the F2-layer maximum in the quiet midlatitude ionosphere under low solar activity: 1. Statistical properties

Results of statistical analysis of the properties of variability of F2-layer maximum parameters (critical frequency foF2 and the height hmF2) in quiet midlatitude ionosphere under low solar activity in the daytime (1000–1500 LT) and nighttime (2200–0300 LT) hours are presented on the basis of Irkutsk station data for 2007–2008. It is found that the distribution density of δfoF2 could be presented as consisting of two distinctly different normal laws of this distribution, one of which corresponds to weak (|δfoF2| < 10%) fluctuations in foF2 and the other corresponds to strong (30% > |δfoF2| > 10%) fluctuations. Weak fluctuations in foF2 to a substantial degree are related to ionospheric variability at times less of than 1–3 h and determine the δfoF2 variability in the daytime hours. Strong fluctuations in foF2 are mainly related to day-to-day variability of the ionosphere at a fixed local time, the variability increasing by approximately a factor of 3 during the transition from day to night and determining the δfoF2 variability in the nighttime hours. The distribution density of ΔhmF2 is close to the normal distribution law. An interpretation of the different character of the distribution densities of δfoF2 and ΔhmF2 is given.

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%.

Variability of parameters of the F2-layer maximum in the quiet midlatitude ionosphere under low solar activity: 2. Strong fluctuations of critical frequency

This paper presents a qualitative analysis of the properties and particular examples of strong (10% < |δfoF2| < 30%) and very strong (|δfoF2| > 30%) fluctuations in the critical frequency of the F2 layer (foF2) of the quiet ionosphere at midlatitudes under low solar activity according to the Irkutsk station data for 2007–2008. It is found that strong day-to-day fluctuations in foF2 are mainly related to changes in thermospheric parameters, which have a nature of planetary waves and tides. Evidently, very strong day-to-day fluctuations in foF2 are caused by superposition of the effects in the ionosphere caused by changes in the thermospheric parameters and those related to a complex of processes of solar wind interaction with the magnetosphere, including the effects caused by the reversal of the vertical component of the solar wind magnetic field southwards. The increase in foF2 during nighttime hours in winter up to values typical for the daytime maximum in foF2 is the brightest example of very strong changes in foF2 in the quiet ionosphere.

Role of atmospheric circulation in the baric field response to the Earth’s crossing of the interplanetary magnetic field sector boundaries

The Earth’s crossings of the magnetic sector boundaries are accompanied by changes in the magnetosphere, ionosphere, and troposphere. We considered the baric field’s response to the crossing of the inter-planetary magnetic field (IMF) sector boundaries during a geomagnetically quiet period. The IMF sign is shown to affect atmospheric pressure in high-latitude regions. The efficiency and sign of the relationship vary during the year. The baric field response to the Earth’s crossing of the IMF sector boundaries is most distinct during equinoxes. It is shown that, during a geomagnetically quiet period, the circulation processes in the atmosphere drive the changes in the atmospheric pressure when the Earth passes from one IMF sector into another.

THE SOLAR WIND MAGNETIC CLOUD OF OCTOBER 18-20, 1995: EFFECT ON IONOSPHERE OF THE RUSSIAN ASIAN REGION

Based on data from a chain of ionospheric stations we investigate the response of ionospheric parameters to the magnetic storm of October, 18-23, 1995. During this storm an abrupt decrease in critical frequencies to 35-45% in the F-region in the daytime hours and intense sporadic E-layers of the auroral type at night were recorded by the entire chain of stations. The analysis of experimental data suggests that the trough boundaries are displaced as far as 41 ° magnetic latitude.

The possible response of the total ozone content on the solar and geomagnetic activity

Abstract The possible total ozone content (TOC) response on the external forcing from solar activity variations, geomagnetic activity variations, and geomagnetic storms was tested on the basis of TOC satellite measurements (NIMBUS-7, TOMS versions 6.0 and 7.0). We tested the existence of 27-day variations in the spectra of TOC variations. The external forcing was investigated for different phases of Quasi-Biennial Oscillations (QBO), which play an important role in Solar-Atmosphere relationships. The results are presented first for East Siberia area and then for different areas well spaced along latitude 52°N.

Modeling of the electron density distribution in the polar ionosphere

Abstract This paper presents the precepts to the development of a high-latitude semi-empirical model and the results obtained by modeling electron density in the height range 100 to 500 km. When constructing the model, advantage was taken of an earlier approach used to model the midlatitude ionosphere, in which, based on empirical data a map of critical frequencies foF2 is deduced. The electron density profile is calculated by solving the set of aeronomic equations controlling the electron and ion distribution.

The role of solar activity in observed climate changes in the 20th century

The possible contribution of solar and geomagnetic activity to changes in the characteristics of the main components of the climatic system—the ocean and the atmosphere—is considered and discussed. The mechanisms and models of the solar activity impact on thermobaric and climatic characteristics of the troposphere are presented. Based on a complex analysis of hydrometeorological data, it has been shown that changes in the temperature of the troposphere and the World Ocean reflect a response both to individual helio-geophysical perturbations and to long-term changes (1854–2015) of solar and geomagnetic activity. It is established that the climatic response to the influence of solar and geomagnetic activity is characterized by considerable spatio-temporal heterogeneity, is of a regional nature, and depends on the general circulation of the atmosphere. The largest contribution of solar activity to the global climate changes was observed in the period 1910–1943.

Solar activity and dynamic processes in the atmosphere and world ocean heat content

The scenario of climatic changes in the 20th century has been presented in the scope of the developed model concerning the effect of solar activity on the parameters of the climatic system governing the energy flux, outgoing from the Earth into space in the high-latitude regions. The regularities of changes in the circulation in the atmosphere and ocean are discussed. Specific attention is paid to the causes of a “cold snap” in 1940–1976 in the Northern Hemisphere and the nature of an anomalous increase in the heat content in the Earth climatic system (ocean) in 1969–1980. It has been indicated that these phenomena result from changes in the circulation in the atmosphere and ocean (specifically, a change in the thermohaline circulation in the Northern Atlantic), heat exchange between the ocean and the atmosphere and cryosphere.