Geomagnetism and Aeronomy最新文献

The accuracy of the M. Aschwanden’s (2020) model for short-term (24 h) prediction of the maximum X-ray class of solar flares based on the power-law dependence on the energy of the potential magnetic field of active regions is checked and assessed. For this purpose, a sample of 275 flares (253 M-class and 22 X-class) in isolated active regions on the solar disk in 2010−2023 is analyzed. Magnetic field extrapolations are made in the nonlinear force-free and potential approximations using the GX Simulator based on photospheric vector magnetograms from the Helioseismic and Magnetic Imager (HMI) instrument onboard the Solar Dynamics Observatory (SDO). It is found that in 6% of cases, Aschwanden’s model underestimates the predicted maximum flare class with respect to the observed one (maximal underestimation by 4.4 times). The accuracy of this model (the average ratio of the observed to predicted maximum flare class) is 0.31 ± 0.47. Four other statistical models are proposed, two of which, like Aschwanden’s model, are based on the power-law dependence of the maximum flare class on the energy of potential magnetic field, and the other two are based on the power-law dependence on the free magnetic energy of active regions. These models give fewer (or no) underestimations of the maximum flare class, but two to three times lower forecast accuracy, ranging from 0.11 to 0.17. Additionally, based on the obtained statistical sample, estimates of the limiting X-ray class of solar flares are made. The five models give different limits ranging from ~X14 to ~X250. The realism of these values and the possibility of refining the models by expanding the sample of events is briefly discussed.

Earthquakes, representing some of the most devastating natural phenomena, pose a persistent challenge in prediction due to their unpredictable nature. Despite significant insights offered by traditional methods, their lack of precision often leaves communities at risk. This research explores a cutting-edge approach in earthquake prediction using artificial intelligence (AI), with a particular emphasis on the attention encoder–decoder long short-term memory (LSTM) model. Focused on modeling seismic events of varied scales that occurred from 2007 to 2010 in the North Anatolian Fault Zone (NAFZ), Turkey, this study compares the efficacy of various AI models including multi-layer perceptron (MLP) and LSTM. The research reveals that the attention encoder–decoder LSTM model surpasses its counterparts in performance. It demonstrates a remarkable capability in forecasting earthquakes by effectively deciphering complex patterns within the data, underscoring its viability as a powerful tool in seismic prediction. The attention encoder–decoder LSTM model, utilizing AI’s latest advancements, offers a nuanced approach by selectively concentrating on relevant data segments, a method particularly beneficial in analyzing complex seismic patterns. This study endeavors to advance the field of earthquake prediction, proposing a model that combines sophisticated AI techniques with in-depth seismic data analysis for more accurate forecasting.

In the evolving field of seismo-ionospheric studies, understanding the variations in the Total Electron Content (TEC) and their implications for seismic forecasting stands paramount. This investigation presents an exhaustive scrutiny of TEC deviations and their prospective role as leading indicators for seismic activities, with a concentrated focus on the tectonically significant East Anatolian Fault Zone. Through the methodical analysis of a 26-day temporal window encapsulating the advent of a notable seismic event, we harnessed advanced statistical approaches to discern and typify TEC aberrations. One of the standout revelations from our research was the unambiguous identification of marked ionospheric TEC irregularities preceding the seismic event. Remarkably, these deviations manifest discernible configurations that, when juxtaposed with geomagnetic storm indices and solar dynamics, suggest their potential utility as seismic harbingers, particularly during epochs typified by serene geomagnetic ambiances. By penetrating these configurations, our inquiry illuminates the complex dynamism intertwining TEC modulations, seismic episodes, and geomagnetic perturbations. Consequently, this exploration augments the contemporary discourse on earthquake-ionosphere dynamics, offering pivotal perspectives that could shape future research trajectories in the domain.

The change with time in parameter S, which characterizes the relation of the critical frequency foF2 to the height hmF2 of the ionospheric F 2 layer is considered. The results of measurements by the vertical sounding method at two stations (Moscow and Juliusruh) are analyzed. The dependence of foF2 on hmF2 is plotted for three intervals: 1957–1980, 1996–2023, and 2011–2023. Five near-noon LT moments and two seasons (winter (January and February) and summer (June and July)) are considered. It is found for both stations and both seasons that the S value has been increasing systematically from the earlier to later periods. At the same time, the winter S values are approximately by a factor of 3 higher than the summer ones for all periods. It is suggested that the found changes in parameter S could provide valuable information on long-term variations (trends) in thermospheric parameters with the help of current theoretical models of the TIEGCM or WACCM-X type.

We analyze the experimental results of multifrequency oblique radio sounding of the ionosphere on the Norilsk–Irkutsk meridional transauroral radio path during the moderate geomagnetic storm on September 22, 2018, with a maximum value of the disturbance index Kp ~ 5. The Global Dynamic Model of the Ionosphere (GDMI), which takes into account the dynamic state of the basic large-scale structures of the polar ionosphere—the main ionospheric trough (MIT), polar oval, and auroral E layer—is used to demonstrate the overall correspondence of maximum observed frequencies (MOF 1F2) and calculated maximum usable frequencies (MUF 1F2) with variations in the geomagnetic disturbance dynamics. A physical explanation is given for the recorded phenomenon of complete blocking of radio waves transmission in local nighttime conditions (“blackout”). The main factor of this effect is the presence of the auroral E-layer in the ionosphere, generated by precipitating charged particles, which are highly inhomogeneous in the longitudinal section of the radio path. Under daytime conditions, the presence of the auroral component in the E layer leads to a weaker effect of degradation of multiple reflections traces on oblique radio sounding ionograms.

The authors performed wavelet analysis of the average monthly changes in the values of the time series of the geomagnetic field, as well as correlation analysis of the wavelet coefficients with fixed values of the scale factor for three European, Asian and North American magnetic observatories. The results suggest that the processes related to the phenomenon of jerks have a morphologically complex character and dynamics that differ significantly for different time scales and probably represent the consequences of a set of phenomena that are similar in nature, but different.

Using data from the 2D IMAGE network and magnetic stations located in Russia, Pc5 geomagnetic pulsations with a frequency of ~2.8 mHz, which occurred in the afternoon sector against the background of the magnetic storm of August 27, 2014, preceded by a 5-day period with low magnetic activity, are studied in detail. In two time intervals, at the beginning of the storm and during the period of maximum magnetic activity, instantaneous 2D distributions of Pc5 magnetic field amplitudes on Earth’s surface are plotted. It has been found that the ionospheric sources of Pc5 (vortex Hall currents) have an elliptical shape with a larger axis in the south–north direction. At the beginning of the magnetic storm, a single burst of Pc5 pulsations was detected, the center of the source of which was located at the geomagnetic latitude ~67.5° (L ~ 6.8 R_E) and moved westward with a velocity of ~0.7 km/s. The estimated size of this ionospheric source is ~150 km in the west–east direction and ~330 km in the south–north direction. During the maximum of the magnetic storm, Pc5 pulsations are produced by two ionospheric sources following each other. These ionospheric sources have a more elongated elliptical shape with axes of ~250 km in the west–east direction and ~670 km in the south–north direction. The centers of these sources were shifted by 4° to a more southern geomagnetic latitude ~63.5° (L ~ 5 R_E) and moved westward with a velocity of ~1.7 km/s. Estimates of the size of the two-time magnetic field tube in which the resonance MHD waves have been generated and its velocity in the equatorial plane of the magnetosphere are presented.

The article examines the properties of a statistical functional constructed from a set of measurements of the H-component of magnetic field measurements. A set of quasilinear objects with very similar parameters has been identified. Based on the hypothesis of the correspondence of these structures to seismic processes, authors estimate the characteristic time intervals for the phases of increase and decrease in the level of compression of lithospheric plates in probable preparation zones for impending earthquakes. It is shown that the statistical approach in geophysical problems can be used to assess seismic hazard in a given region in near real time.

The article develops a method for determining the geomagnetic cutoff rigidity based on tracing of charged particles in Earth’s magnetic field using the particle-in-cell method implemented in the Buneman–Boris scheme. In order to test the method, the geomagnetic cutoff rigidity in the field of an ideal dipole and in the field given by the IGRF model are calculated. In the first case, the obtained data are compared with analytical values. The calculation accuracy in this case is 3 MV. In the second case, the penumbra pattern is reproduced in different geographical locations, for different periods, and the stability of the method to small perturbations of the initial parameters is investigated. As the main results, the article constructs and analyzes geomagnetic cutoff rigidity maps at low-orbit satellite altitudes for different directions in space as well as their variations from 1900 to 2015.

The results of an analysis of some irregularities in a series of coordinates of the shift in the geographic North Pole along Earth’s surface are presented in order to establish a temporal relationship between their appearance and some global jerks in the geomagnetic field. The calculations used average daily data from the IERS service on movement of the North Pole from 1962 to 2021, as well as information on global jerks in the geomagnetic field at all magnetic observatories on the globe. To identify and analyze irregularities in the movement of the pole along the Earth’s surface, the following methods were used: Fourier methods and wavelet analysis of time series, methods for determining the threshold of a fixed shape and minimax in the procedure for analyzing non-Gaussian noise, methods of phase and pseudophase space, as well as the stroboscopic method of constructing the Poincaré map. Analysis of local Fourier spectra and wavelet spectra reveal irregularities in the shift of the North Pole along the Earth’s surface in the following time intervals: 1967.04.09–1967.11.30, 1974.03.29–1974.09.12, 2005.11.03–2006.03.07, comparable to the appearance of global jerks in 1969, 1978 and local jerks in 2005. It is believed that the changes in energy that caused short-term deviations of the shift in the pole’s trajectory and return to the previous trajectory at cusp points are associated with singularities in the interaction of oscillations in Earth’s rotational and translational motion in the Solar System. The time of the appearance of irregularities on the graphs of the polar shift along the Earth’s surface in 1967 and 1974 is ahead of the time of the appearance of global jerks in the geomagnetic field.