Geomagnetism and Aeronomy最新文献

Сorotating interaction regions of solar wind flows with different velocities have actively been magnetohydrodynamically simulated for many years. However, the main goal is to predict heliospheric characteristics in Earth’s orbit, and so calculations are performed to distances of 1–1.5 AU. In the last decade, systematic magnetohydrodynamic calculations of corotating interaction regions up to much larger distances have appeared, which are necessary for studying recurrent variations in the intensity of galactic cosmic rays. Based on one of these calculations, we previously showed that, at least for one rotation of the Sun (Carrington rotation 2066, January–February 2008), the effect of corotating interaction regions on large-scale characteristics of the heliosphere that are important for GCR modulation and, therefore, the intensity averaged over longitude is significant. We assumed that the main principles of this effect of corotating interaction regions on GCRs can be studied both by 3D modeling of the GCR intensity and in much simpler 2D models. In this paper, we discuss the results, prospects, and shortcomings of such a 2D description of the effect of corotating interaction regions on the GCR intensity.

The cause of the asymmetry in the sunspot distribution in the northern and southern hemispheres of the Sun at the end of the Maunder Minimum is studied. It is demonstrated that the expected asymmetry of generation sources is insufficient for such an explanation. To study the influence of asymmetry of generation sources, numerical simulation is used, based on modifications to the Parker model.

The results of observations of coronal jets on the Sun are briefly reviewed. Data on jets of different types (jets, jetlets) were collected. Their properties are considered, such as lifetime, length, width, velocities, coupling to the magnetic field, and their putative role in hot plasma and energy transfer into the corona. Observational data obtained with ground-based and space telescopes were used. There is growing evidence that jets play a key role in imparting mass to the corona and solar wind and can provide sufficient energy to power the solar wind (see, e.g., (Tian et al., 2014)). Modern observations by the Parker Solar Probe and Solar Orbiter spacecraft will contribute to the understanding of solar jets and related phenomena.

The results of analyzing the relationship between large-scale epidemics (pandemics) caused by the Ebola, influenza AH1N1, and AH7N9 viruses and the MERS-CoV coronavirus with global solar factors for the period from 2008 to 2019 (24th cycle of solar activity) are presented. A variable change in the annual values of pandemic cases has been established, corresponding to the regular course of F10.7 cm (r ~ 0.65), MF (r ~ 0.85) and λ315 nm (r ~ 0.83) in the 24th SA cycle. It was concluded that the dynamics of the spread of pandemics depend on temporary changes in UVB radiation power, in particular, at the boundary of the spectral bactericidal efficiency curve (λ315 nm).

Here we studied the planetary features of the spatiotemporal distribution of ionospheric electrojets recorded in the onset of a substorm and in time on the activity maximum of three very intense substorms (with an AL-index from –1200 to –1700 nT) observed during the main phase of the strong magnetic storm on March 23−24, 2023. We have analyzed the substorms by applying the global maps of the planetary distribution of high-latitude ionospheric currents, compiled from simultaneous magnetic measurements on 66 low-orbit satellites of the AMPERE project, as well as ground-based magnetograms from the Scandinavian IMAGE profile and mid-latitude IZMIRAN stations located in the same longitudinal region. It was established that the onset of all the studied substorms on the IMAGE meridian was accompanied by the development of a nighttime current vortex with clockwise rotation, which is an indicator of an increase in downward field-aligned currents. The ground-based mid-latitude observations at the IZMIRAN station network confirmed that the center of the current wedge of the substorm was located in the nighttime sector significantly east of the IMAGE meridian. In the time of the substorm intensity maximum, a similar but more extensive current vortex was observed in the morning sector, which is probably typical of intense substorms.

In this work the problem of reconstructing the vector anomalous magnetic field from single-component data was solved by means of artificial neural networks. For training an artificial neural network a database of anomalous magnetic field components ({{B}_{x}}), ({{B}_{y}}), ({{B}_{z}}) was created using a set of point magnetic dipoles lying under the field measurement plane. Using a synthetic example, the work of a trained neural network was shown in comparison with a well-known numerical algorithm for restoring a vector field from data of one component. Further, according to the data of the vertical component of the anomalous geomagnetic field the horizontal components of the anomalous geomagnetic field were restored using artificial neural networks in the territory of 58°–85° E, 52°–74° N with a grid step of 2 arc minutes.

The impact of the Weddell Sea Anomaly on the structure of the nightside ionosphere in the summer Southern Hemisphere is considered in detail. For this, data from the CHAMP satellite were used in January 2003 under high solar activity and in January 2008 under low solar activity. The data relate to the local time interval 02−04 LT, when the increase in electron density due to the formation of the anomaly is the strongest. At longitudes of 60°−180° E under high solar activity and 0°–210° E under low solar activity, where there is no anomaly, the main ionospheric trough is observed. The plasma peak in the nightside ionosphere associated with formation of the anomaly reaches 6 MHz under low solar activity and 10 MHz under high solar activity. The strongly developed plasma peak decreases sharply to high latitudes at the equatorward boundary of auroral diffuse precipitation, which corresponds to the plasmapause. When the anomaly is weakly developed, the contribution of diffuse precipitation becomes noticeable, so that the plasma peak expands poleward due to this precipitation. Poleward of the anomaly, the high-latitude trough is usually observed at latitudes of the auroral oval. A well-defined electron density minimum is often formed equatorward of the Weddell Sea Anomaly, which can be defined as a subtrough. Sometimes the subtrough is created by the escape of ionospheric plasma from the summer to the winter hemisphere. Then a density maximum forms in the winter hemisphere at adjacent latitudes. A subtrough is much more common under low solar activity than under high.

Positioning, navigation and time are the cornerstones of satellite navigation. These aspects are frequently affected by ionospheric variations caused by solar flares (SF). In this study, we have attempted to predict the range error (RE) caused by ionospheric delay in Global Positioning System (GPS) signals during six different X-class SF that occurred in the 25th solar cycle using two different approaches, namely, a recurrent neural network (RNN) and the ordinary Kriging-based surrogate model (OKSM). The total electron content (TEC) collected from Hyderabad station along with other input parameter includes the Planetary A and K index (Ap and Kp), solar sunspot number (SSN), disturbance storm time index (Dst), and radio flux measured at 10.7 cm (F10.7) were used for prediction. The OKSM uses the previous six days of datasets to predict the RE on the seventh day, whereas the RNN model uses the previous 45 days of datasets to predict the RE on the 46th day. The performance of both models is evaluated using statistical parameters such as root mean square error (RMSE), normalized root mean square error (NRMSE), Pearson’s correlation coefficient (CC), and symmetric mean absolute percentage error (sMAPE). The results indicate that the OKSM performs well in adverse space weather conditions when compared to RNN.

Ionospheric sporadic E layers are very thin, but with a much higher electron density than normal E regions that occur at altitudes of about 90–130 km. Vertical wind shear is considered the main source of mid-latitude sporadic E layer formation, which leads to periodicity, such as 24-h, 12-h, and so on. In this paper, a time series analysis of the critical frequency of the sporadic E layer (foEs) observed by an ionosonde is performed at seven stations (spanning about 37° N–51° N and 29° S–67° S) to investigate the terdiurnal signature in it. Except for the already known 24-h and 12-h periodicities features which are related to diurnal and semidiurnal tides, new findings are also obtained. The 8-h periodicity is a regular and repeatable feature at high mid-latitude regions of both hemispheres. The 8-h periodicity is more prominent at mid-latitudes (~50° N and ~60° S) during the winter and spring months of the hemisphere, which agrees with the terdiurnal tide features. It also shows that the amplitude of the 8-h periodicity is equivalent to the 12-h periodicity component in summer and autumn and almost the same as the 24-h periodicity component in winter under certain circumstances. This indicates that the 8-h periodicity should be taken into consideration for sporadic E layer modeling.

Events of induced proton precipitations from the inner radiation belt have been detected. They accompanied almost a half (11) of 25 anomalous electron precipitations recorded onboard the Meteor-M No. 2 satellite in 2014−2022 in Oceania at low latitudes in the morning hours of local time under quiet geomagnetic conditions. It is surmised that such events could be provoked by proton fall into cyclotron resonance with low-frequency radiation stimulated by a mobile ionospheric heater. The observed effects in anomalous electron precipitations which may be interpreted in the framework of the mobile ionospheric heater conception are also discussed.