Том 24, № 6 (2024)

The paper presents a description of an automated system and the algorithms implemented in it for detection, association and location of low-frequency acoustic events based on infrasound array data. An algorithm for detecting infrasound signals by calculating the cross-correlation function between records of individual sensors in a array is described. The implemented algorithm is optimized for working with arrays consisting of a large number of sensors, which allows minimizing the computational load on the monitoring system in near-real time mode. A procedure for recognizing long-term signals with a source position that may change over time, such as moving vehicles or snow avalanches, is described. The paper also describes algorithms for associating infrasound signals recorded by different arrays, as well as locating a signal source based on data from several infrasound arrays. The system is capable of simultaneously analyzing seismic and infrasound monitoring data and detecting pairs of two types of signals associated with a common source. The algorithm for such an association is also given in the paper. The described system of automatic detection and location of infrasound signals can be used for monitoring dangerous natural and man-made processes and phenomena in a mode close to real time.

The Vema Channel is a deep narrow passage in the South Atlantic and a main path for bottom water which flows northward from the Argentine Basin to the Brazil Basin and after all into the North Atlantic. The thermohaline structure and dynamics in it have been studied for many years. In this study we report our new data on dissolved oxygen and nutrients measurements performed in 2022 at the exit of the Vema Channel. This is the first time that such measurements have been made with high spatial resolution. Data from standard oceanographic sections located near the study area are also analyzed. A significant dependence in the distribution of dissolved oxygen and nutrients on the hydrological structure is shown. Local dissolved oxygen minimum indicates the lower boundary of Circumpolar waters. It was also revealed insignificant temporal variability of nutrients concentration.

This review considers several issues of space weather studies that are directly related to the problem of geomagnetically induced current (GIC) excitation in the power line transmission systems. Expectations to reduce the damage to technological systems from space weather were related with elaboration of models capable of real-time predictions of electromagnetic disturbances at the Earth's surface. However, the examination of the feasibility of the MHD simulation to predict the level of geomagnetic field variability, and consequently GICs, during the May 27–28, 2017 storm showed that the modeling reasonably well reproduced the global magnetospheric parameters, but the predicted magnetic field variability dB/dt has turned out to be more than order of magnitude less than that observed. The reason is the inability of current global MHD models to adequately predict the fine structure of the storm/substorm – Pi3 disturbances, and consequently GICs that they drive. Moreover, impulsive disturbances such as Pi3 pulsations demand a special tool for their analysis. Data processing technique for a 2D network of magnetic stations has to be elaborated to automatically recognize eddy current structures in the ionosphere and estimate their characteristics. The proposed technique applied to Pi3 pulsations on March 17, 2013 revealed that each vortex caused a disturbance of the vertical magnetic component Z and GIC burst up to ∼ 100A. The efficiency of GIC generation by different types of magnetic storms must be examined. For that it is necessary to compare GIC responses to storms caused by coronal mass ejection and by corotating interaction region, and to estimate the normalized GIC-effectiveness of each storm. The excitation rate of GIC during storms may be associated with the occurrence of mesoscale current vortices.