Vol 64, No 3 (2024)

Forbush decreases in galactic cosmic rays (according to data from a network of neutron monitors) and accompanying geomagnetic disturbances over a long period from 1957 to 2022 have been identified and studied. Statistical relationships between various parameters of cosmic ray flux and geomagnetic activity indices are analyzed. It has been established that the magnitude of Forbush decreases depends nonlinearly on the class of geomagnetic storm. A moderate correlation is found between the extreme values of various geomagnetic activity indices (Ap, Kp, Dst) and the characteristics of cosmic rays. It is also shown that the simultaneous registration of extreme values of cosmic rays and geomagnetic activity parameters does not always occur but depends on the sign of the Bz-component of the interplanetary magnetic field in a particular event.

The article presents the results of a studying detection of the sudden commencement (SC) and main impulse (MI) of a magnetic storm as a function of the geographic coordinates of magnetic observatories and Universal Time, using modern data with second time resolution. The analysis was carried out for two events in which an interplanetary shock wave impacting the magnetosphere was associated with interplanetary coronal mass ejections (CMEs) with sources in different hemispheres of the Sun. The authors propose an approach to determine the time points of SC and MI detection. It is concluded that the SC and MI detection times may differ by several seconds to more than a minute at magnetic observatories located at different geographic latitudes and longitudes. For the studied events, the graphs of SC and MI detection as functions of the geographic coordinates of magnetic observatories and Universal Time revealed trends according to which, on average, the higher station the latitude, the later SC and MI are detected at the station.

Based on data from a network of oblique-incidence sounding radio paths at mid-latitudes in the Asian region of Russia, a high (up to 40−50%) average-daily recording probability of the medium-scale traveling ionospheric disturbances in years of moderate solar activity has been identified. The daily variation in the recording probability of these disturbances at mid-latitude radio paths in the Asian region of Russia has a pronounced seasonal dependence. For the winter season, there is a daily maximum probability, reaching 100% on some days. In the summer season, it occurs at night hours of local time at the midpoint of the corresponding radio path. The most likely reason for this is the transition from winter to summer pattern of the atmosphere zonal circulation.

An analysis of a large array of observation data (over ~50–80 years) for 456 meteorological stations in Russia revealed a distinct difference in the monthly amount of precipitation (DP) during years of maximum and minimum solar activity depending on months and seasons of the year and on latitudes and longitudes. Particularly large DP values are observed in the latitude belt of U = 40–55° N in the longitude range D = 20–40° E in October, DP being 13.6±2.2 mm, as well as in the longitude range D = 110–130° E in June, DP being −8.5±1.0 mm. In the zone of maximum influence of solar activity on the amount of precipitation, a study was conducted on the presence of a correlation between Wolf numbers and the amount of precipitation. As a result, a strong increase in the correlation was discovered in the case of a backward shift in the Wolf numbers, which argued in favor of the influence of solar activity on weather. The author is convinced of the physical significance of the correlation, because it is obtained from data from several geographical points. It is concluded that solar and geomagnetic activity can govern the development of internal instabilities of the atmosphere and thereby influence climate.

The auroral electrojet index AE is often used in forecasting models as a characteristic of a source of the disturbance propagation in the geosphere from the pole to middle and low latitudes. However, these data are no longer available digitally since January 2020. Instead of the AE−index, we suggest using the recently introduced 1 h Apo−index, given the close proximity of magnetometer networks for these indices at high latitudes and the availability of the Apo−index in real time. To this end their correlation is analyzed during 276 intense storms for 1995–2017. Storm profiles are constructed by method of superposed epoch with zero epoch time t₀ = 0 taken at the threshold value of AE ≥ 1000 nT. A comparison is made of the storm profiles of AE(t), Apo(t), the interplanetary electric field E(t) and the solar wind speed Vsw(t) within 72 hours: 24 hours before the storm peak t₀, and 48 hours after it. A good agreement is obtained between the sets AE(t) and Apo(t) with a correlation coefficient of 0.70. Comparison with the interplanetary parameters testifies on the correlation of AE(t) and Apo(t) with the electric field E(t) but absence of their coupling with the solar wind speed Vsw(t). A two−parametric formula is derived for dependence of the auroral electrojet index AE(t) on the interplanetary electric field E(t) and the geomagnetic Apo(t) index for the geomagnetic storm forecasting. In the absence of E(t) data, formulae for the dependence of AE(t) on Apo(t) is introduced for implementation in real time and the inverse dependence of Apo(t) on AE(t) for reconstruction of the 1 h Apo−index before 1995. Validation of the proposed models with data for 5 intense storms in 2018 has shown a close resemblance of the model with observation data of the AE−index with a high coefficient of determination R² ranging from 0.62 to 0.81.