Geomagnetism and Aeronomy最新文献

In this study, we consider historical geomagnetic satellite data obtained during a strong magnetic storm on March 8−9, 1970. In addition to the data of the Soviet satellite Kosmos-321, data from the American satellite OGO-6, which performed geomagnetic measurements at the same time, were used. We analyzed time variations of external magnetic fields recorded in satellite and ground-based observations of the magnetic field. The research also gave impetus to the creation of the improved software implementation of the auroral oval model APM, which enables reconstruction of its position and precipitation intensity in both the past and near real time. The magnetic variations originating in the near-Earth space from various sources were identified. In particular, we revealed the signatures of the storm-time ring current and equatorial and auroral electrojects. The paper highlights the enduring value of historical data of magnetic field observations stored in data centers and continuously digitized by their staff.

When analyzing a narrowband signal, the Hilbert transform is often used, which makes it possible to describe the process through slowly changing functions: the envelope (amplitude) and, weakly dependent on time, the characteristic signal frequency—the “instantaneous” frequency. Based on the smoothness of these characteristics, one can evaluate the process and compare it at different periods. This approach was used to analyze the spectral components of a series of average monthly Wolf numbers. This description of the main and second harmonics, supplemented by the properties of the long-period component, gives a fairly complete picture of the entire series of monthly averages. The work examines the correspondence of the characteristics of reliable data, with this approach, to the accepted description in terms of the parameters of cycles (maximum of the cycle, duration of the cycle, and its growth branches) and constructs an “envelope” of the maxima of the cycles. The time dynamics of the instantaneous frequencies of the fundamental and second harmonics of the entire series are also presented, and significant differences in their behavior are noted in the intervals corresponding to the reconstructed and reliable parts.

The presence of ions within the atmospheric region near the soil surface has considerable implications for enhancing our understanding of Earth’s complex systems. This study delves into the intricate relationship between the atmospheric electric field in the boundary layer and lithosphere. The focus was specifically on investigating how soil radon and its progeny influence the production rate of ions in both the soil and the atmosphere. To achieve this, we combined the radon transport equation with advanced machine learning techniques. Using a well-suited machine learning model, we effectively modeled the responses of soil radon and seamlessly integrated them into the radon transport equation. The resulting insights were used to predict the rates at which radon-induced ion pairs were produced. A particularly important parameter is the surface-ion production rate, which is crucial for estimating the amplitude of the near-surface electric field. This methodology was applied to analyze data from two radon monitoring stations in Turkey: Erzincan, located along the North Anatolian Fault (NAF), and Malatya, situated close to the East Anatolian Fault regions. The significance of this estimation approach resonates within the field of lithospheric–atmospheric studies. This innovative methodology holds promise as a valuable tool for future investigations in the domains of lithosphere–atmosphere–ionosphere coupling (LAIC), global electric circuits (GEC), and seismo-ionospheric coupling. Ultimately, this study underscores the importance of carefully considering the intricate interconnections that exist among different components of Earth’s intricate system. This advocates the adoption of novel methods to shed light on these complex interactions.

Active development of the Arctic and increased intensity of navigation along the Northern Sea Route and air traffic in the Arctic Ocean airspace draws attention to the problem of disruptions of transpolar radio wave propagation. In high-latitude regions, the passage of navigation signals of global positioning systems depends on the state of the ionosphere. During geomagnetic disturbances, ionospheric inhomogeneities develop that interfere with satellite positioning systems. The position and shape of auroras depend on the state of the magnetosphere. In this study, the component model of the auroral magnetic field has been calculated for the first time using the updated digital model of the full values of Earth’s magnetic field components of the St. Petersburg Branch of the Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation of the Russian Academy of Sciences for the first time. The magnetic field of the auroral zone was calculated for heights from 0 to 1000 km for the period from 1900 to 2023, including for heights of 100–110 km, where the intensity of auroras reaches its maximum in the near-Earth space of the Arctic. The spatial displacement of the auroral oval has been estimated for the period from 1957 (its first mathematical description) to the present. As the analysis showed, the displacement of the boundaries of the auroral oval during the period under consideration has occurred in time and in space codirectionally with the displacement of the isolines of the extremes of the horizontal and vertical components of the auroral magnetic field of the Northern Hemisphere.

Long-term variations (trends) in the height of the ionospheric F2 layer peak hmF2 is analyzed based on the data of Moscow and Juliusruh stations. The near-noon LT hours and two winter months (January and February) and two summer months (June and July) are considered for a period of 1996–2023. Well-pronounced and statistically significant negative hmF2 trends are found both in summer and winter. Overall, the F2 layer height decreased during the analyzed period by 0.5–1 km per year. The “Delta” method developed and published by the authors earlier is applied to the same data. The results confirm a systematic decrease in the hmF2 value in the past two decades. It is found that the F2 layer height has decreased in recent years more rapidly than in the earlier years.

The article studies interdiurnal variations in the statistical characteristics of the electron number density NmE of the ionospheric E layer peak for each month of the year in geomagnetically quiet conditions with low and average solar activity based on hourly measurements of the critical frequency of the E layer from the ground-based Dourbes ionosonde from 1957 to 2023. The authors have calculated the mathematical expectation NmE_E; the most probable NmE_MP; the arithmetically monthly median NmE_MED; the standard deviations of σ_E, σ_MP and σ_MED of quantity NmE from NmE_E, NmE_MP, and NmE_MED; the variation coefficients CV_E, CV_MP, and CV_MED of quantity NmE with respect to NmE_E, NmE_MP, and NmE_MED, respectively. It is shown that NmE_E provides the best description of the set of measurements of NmE using only the statistical parameter due to the smaller interdiurnal variability of NmE compared to NmE_MP or NmE_MED. For the first time, it is proved that the transition from low to average solar activity leads to significant changes in the interdiurnal variability of NmE, with the longest periods of increase and decrease in the studied variability in March and December, respectively.

The propagation velocities of geomagnetic Pc5 pulsations in the azimuthal and meridional directions were analyzed for a series of events. Two methods were used: based on the phase delays of the signal between stations and the displacement of vortex centers of their equivalent current systems. The analysis showed that the propagation of pulsations and vortices coincides in direction—along the meridian, they predominantly propagate northward. In most cases, the propagation velocity is 5 km/s for pulsations and 2 km/s for vortices. In the azimuthal direction, pulsations and vortices propagate westward, with pulsation propagation velocity of 10 km/s and vortex propagation velocity of 3 km/s. However, the distributions of azimuthal velocities for both pulsations and vortices exhibit comparable maxima corresponding to eastward propagation: pulsations at a velocity of 10 km/s and vortices at 5 km/s. It is concluded that the measured phase velocities of pulsations at the ionospheric level are approximately twice the group velocities of vortices.

A search for long-term trends in the F 2 layer critical frequency foF 2 is performed based on vertical sounding observations at three stations of the Northern Hemisphere (Juliusruh, Boulder, and Moscow) and three stations of the Southern Hemisphere (Townsville, Hobart, and Canberra). A method developed and extensively described by the authors is used. The data for two winter months in each hemisphere for five near-noon LT moments were analyzed. Three solar activity (SA) proxies (F 30, Ly-α, and MgII) were used to eliminate SA effects. Negative trends are obtained for all considered situations (station, month, LT moment, SA proxy). The trends agree well with each other both if stations of the Northern and Southern hemispheres are compared individually or in aggregate.

Based on data from mid-latitude ionospheric stations at close corrected geomagnetic latitudes, the properties of the variability in the F2 layer peak density (NmF2) at different longitudes were analyzed during increased (48 > ap(τ) > 27) and high (ap(τ) > 48) geomagnetic activity, where ap(τ) is the weighted average ap-index of this activity. The standard deviation σ of Nm fluctuations with respect to the quiet level and the average shift of these fluctuations x_ave were used as characteristics of this variability. It was found that at all analyzed stations, the variance σ ² for increased geomagnetic activity is greater than for quiet conditions but hardly differs from σ ² for high geomagnetic activity. For all analyzed cases, the average shift x_ave < 0, and for high geomagnetic activity, the absolute value of x_ave is greater than for increased geomagnetic activity. The difference in x_ave values between the analyzed stations is quite large. One reason for this difference may be related to the dependence of x_ave on geomagnetic latitudes. Approximations of the geomagnetic field by the tilted dipole (TD), eccentric dipole (ED), or using corrected geomagnetic (CGM) coordinates were used to select these latitudes. It was found that the dependence of x_ave on ED latitude is more accurate than the dependence of x_ave on TD latitude and, moreover, the dependence of x_ave on CGM latitude. Therefore, ED latitudes, and not CGM latitudes, are optimal for accounting for storm effects on the F2 layer peak density at mid-latitudes. This conclusion has apparently been obtained for the first time.

Abstract—Based on data from a system of oblique sounding radio paths at mid-latitudes in the Asian Russia, a high (up to 40–50%) average daily probability of medium-scale traveling ionospheric disturbances in years of moderate solar activity is revealed. The daily variation in the probability of recording these disturbances has a pronounced seasonal dependence. For the winter season, there is a daytime maximum probability that reaches 100% on some days. During the summer season, the maximum probability falls on the nighttime hours of local time at the midpoint of the corresponding path. A possible reason for this is the transition from the winter to summer atmospheric circulation system.