F. S. Bessarab

Application of the models of the middle and upper atmosphere to simulation of total electron content perturbations caused by the 2009 stratospheric warming

Sudden stratospheric warming (SSW) is a unique atmospheric phenomenon, which consists in a rapid rise of temperature at altitudes of ~30–40 km in high latitudes of the winter, typically, northern hemisphere. Modeling SSW effects in the mesosphere, thermosphere, and ionosphere is a challenging problem, because it must be done on a global scale, with consideration of numerous physical and chemical processes. This paper reports the results of calculations of the characteristics of total electron content (TEC) perturbations for the conditions of the SSW event in January 2009. The calculations are performed using the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) supplemented by the lower boundary conditions in the form of space–time distributions of the basic parameters of the mesosphere at an altitude of 80 km, as calculated by the SOCOL, KASIMA, and TIME GCM models. The simulation results show that, for some versions, the spatial distribution of total electron content disturbances ΔTEC shows a qualitative agreement with experimental data; however, the values of ΔTEC in all variants of calculations proved to be an order of magnitude lower than the measured.

Effect of NO concentration disturbances on the global distribution of ionospheric parameters during geomagnetic storms

The role of nitric oxide (NO) in the ionospheric effects during geomagnetic storm on May 1–3, 2010, is examined. The studies are performed using a global self-consistent model of the thermosphere, ionosphere and protonosphere (GSM TIP). Two versions of calculations are used: (1) based on an analytical approximation of the NO concentration and (2) self-consistent calculation of the global distribution of nitric oxide over the ionosphere. It is shown that, during a geomagnetic disturbance, the NO concentration at high latitudes shows an increase, which under the influence of the horizontal circulation of neutral gas leads to an increase in the concentration of NO at mid-latitudes ∼1 day after the start of the perturbation. Simulated values of foF2 are compared to experimental data obtained at a number of Russian mid-latitude stations. It is noted that the self-consistent calculations of the NO concentration better describes the spatial-temporal behavior of ionospheric parameters during geomagnetic storms.

Diurnal and longitudinal variations in the earth’s ionosphere in the period of solstice in conditions of a deep minimum of solar activity

The results of studies of longitudinal and LT variations in parameters of the ionosphere–plasmasphere system, obtained using the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP), assimilation ionospheric model IRI Real-Time Assimilation Mapping (IRTAM), and satellite and ground-based observational data are presented in the paper. The study of the main morphological features of longitudinal and LT variations in the critical frequency of the ionospheric F2 layer (foF2) and total electron content (TEC) depending on latitude in the winter solstice during a solar-activity minimum (December 22, 2009) is carried out. It is shown that the variations in foF2 and TEC, on the whole, are identical, and so mutually substitutable, while creating empirical models of these parameters in quiet geomagnetic conditions. The longitudinal and LT variations in both foF2 and TEC are within an order of magnitude everywhere except for the equator anomaly region, where LT variation is larger by an order of magnitude than longitudinal variation. According to the results of the study, in the American longitudinal sector at all latitudes of the Southern (summer) Hemisphere, maxima of foF2 and TEC are formed. The near-equatorial and high-latitudinal maxima are separated out from these. The estimate of the contribution into the longitudinal variation in foF2 and TEC for various local time sectors and at various latitudes has been obtained for the first time. In the Southern (summer) Hemisphere, longitudinal variation in foF2 and TEC is formed in the nighttime.

Modeling of response of the thermosphere-ionosphere system to sudden stratospheric warmings of years 2008 and 2009

A study of the response of the thermosphere and ionosphere to sudden stratospheric warmings (SSWs) which occurred in January of 2008 and 2009 is presented. The Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) developed in the West Department of IZMIRAN was a theoretical basis for this study. A comparison of the simulation results of the thermosphere-ionosphere response to SSW events with the observational data over Irkutsk and also with theoretical and experimental studies carried out during the recent years is performed. SSW events were modeled by setting disturbances in the neutral temperature and density at the lower boundary of the GSM TIP model (80 km above the Earth’s surface). It is shown that the disturbances related to SSW lead to substantial global effects in the thermosphere and ionosphere. The analysis of the experimental data showed that, in spite of very similar solar and geophysical conditions on the background of which two considered stratospheric warming events happened, the occurring disturbances in temperature at heights of the mesosphere and lower thermosphere differ substantially from each other, although some common regularities still take place especially at heights of the ionospheric F region.

Numerical simulation of effects of the August 11, 1999 solar eclipse in the outer ionosphere

The results of a numerical simulation of such parameters of the topside ionosphere as concentration Ne and temperature Te of electrons, and concentration n(H+) and fluxes along the magnetic field lines Φ(H+) of H+ ions at an altitude of ∼2000 km for the conditions of the August 11, 1999 solar eclipse are presented. The calculations were performed using the Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere of the Earth (GSM TIP). It is shown that during the eclipse, in addition to a region of decreased values of Te in the Northern Hemisphere and in the magnetically conjugate region in the Southern Hemisphere, regions of electron heating emerge in both hemispheres. Simultaneously, an extended region of decreased values of Ne comes into existence and moves behind the Moon’s shadow. Regions with decreased (down to ∼30%) and enhanced (up to ∼50%) concentrations of H+ ions are detected in the global distribution of these ions.

Sensitivity of GSM TIP model to the variability of the UV and EUV solar radiation

Abstract A self-consistent numerical global model of the coupled thermosphere, ionosphere and protonosphere (GSM TIP) has been used to examine the variations of the upper atmospheric parameters with respect to the changes of the solar extreme ultraviolet/ultraviolet (EUV/UV) flux from solar minimum to solar maximum conditions. Two model runs were executed for equinox and quiet geomagnetic periods for the same initial conditions. In the first case for the given UV flux the amplitude of the EUV flux was changed, whereas in the second case the UV flux was increased at a constant level of the EUV flux. For these cases only the global dynamical structure of the thermosphere has been studied. The model results have shown that in the first case the diurnal mode of the neutral wind increased at an altitude of 300 km and the semidiurnal mode increased at 120 km. In the second case the variation of the neutral wind circulation was opposite. Amplitudes of the variation were 15 m/s at 300 km and 5 m/s at 120 km.

Model study of the response of the thermosphere to perturbations of mesospheric tides and planetary waves during a sudden stratospheric warming

The results of numerical simulations of the effects of a sudden stratospheric warming (SSW) in January 2009 are examined. The calculations are performed within the framework of the Global Self-Consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP), which calculates the parameters of the neutral and charged components of the upper atmosphere. An analysis of the numerical simulation results showed that the perturbation of mesospheric tidal and planetary waves significantly affects the structure of variations of the thermosphere at altitudes below 150 km. At higher altitudes, the characteristics of planetary and tidal waves in the thermosphere are practically insensitive to the corresponding mesospheric perturbations. The calculated space–time structure of ionospheric perturbations caused by mesospheric and planetary tidal waves is in qualitative agreement with observation data. The results show that the main reason for the observed ionospheric effects is the perturbation of the electric fields in the dynamo region. However, the calculated magnitudes of the ionospheric effects produced by the SSW are at least two- to threefold weaker than the observed. It is assumed that, in order to achieve a quantitative agreement between simulation and experimental results on the ionospheric effects of the SSW, it is not enough to consider only the dynamics of planetary and tidal waves in the mesosphere. An additional source of the perturbation of the thermosphere and ionosphere during the SSW may be associated with the propagation of internal gravity waves from the lower atmosphere and their dissipation in the thermosphere.

Planetary Wave Periods in foF2 Time Variations Based on Winter Data from Kaliningrad Station in 2008−2010

The study presents the results of the analysis of the F2-layer critical frequency variations obtained for the winter periods of 2008–2010, during which sudden stratospheric warmings were observed. The data were obtained at Kaliningrad ionospheric station (54.6° N, 20° E) with the Parus digital ionosonde in standard sounding mode. The mean daily foF2 values were used in the analysis. The results of spectral analysis based on continuous wavelet transform showed that, during all of the warmings that occurred in 2008–2010, the foF2 time variations demonstrated the presence of wave processes with periods of approximately 5−6 days, as well as more extended processes with periods of ~10−13 and 23−30 days. These periods coincide with the characteristic periods of planetary waves observed in the mesosphere during sudden stratospheric warmings, while the 13- and 30-day periods can be conditioned by the influence of the Sun.

Quasi-wave variations in foEs during stratospheric warmings of 2008–2010 according to data from Kaliningrad ionospheric station

The results of analysis of variations in the sporadic layer critical frequency (foEs) for winter periods of 2008–2010 in which sudden stratospheric warmings were observed are presented in the paper. The data were obtained at Kaliningrad ionospheric station (54.6° N, 20° E) by a Parus digital ionosonde under the usual sounding regime with an interval of 15 min. Daily mean values of foEs were used for the analysis. Solar and geomagnetic activity remained low during the periods under study, making it possible to relate the quasiwave time variations in foEs to the parameters of stratospheric warmings. The results of spectral analysis performed on the basis of continuous wavelet transform showed that, during all warmings occurring in 2008–2010, time variations in foEs show the presence of wave processes with a period of an order of 5 days and longer ones with a period of ~10—11 days. These periods coincide with characteristic periods of planetary waves observed in the atmosphere during sudden stratospheric warnings.