Search Results (8)

The formation of international networks of magnetic observatories has provided new opportunities for monitoring geomagnetic disturbances and solving problems related to space weather. On the other hand, collective processing of data from numerous observatories revealed problems with the quality of data provided by some of them. Sometimes, the reason for the decrease in data quality is associated with faulty measuring instruments. However, every year, industrial interference also increases its influence on measurement quality. INTERMAGNET suggests carrying out a mutual comparison between the values of neighboring magnetic observatories as one of the methods for solving the problem of maintaining data quality. This paper proposes a method to improve the quality of magnetograms, which makes it possible to eliminate the results of interference of local origin through the use of four spatially separated magnetic observatories located in Kazakhstan. This method is suitable for automating the magnetograms’ quality control process. Full article

The geomagnetic dynamo is currently considered the most likely source of the Earth’s main dipole field. However, the radius of the current ring located in the Earth’s core is not reliably known. There are methods for indirectly estimating the radius of this current. Another method is proposed that allows one to indirectly estimate the radius of the current ring inside the Earth’s core based on measurements of the Earth’s magnetic field by observatories included in the INTERMAGNET network. The results of measurements taken on a day with low magnetic activity were compared using the least squares method with fields that could be created by ring currents of different diameters at the locations of magnetic observatories. The assumption was made that the ring current in the model used is located in the plane of the Earth’s equator with the center coinciding with the axis of rotation of the Earth. Estimates of the current radius in the range of 957–1595 km were obtained, which corresponds to the boundary between the solid and liquid cores of the Earth. These results can refine the model of the structure of the Earth’s core and Earth’s magnetism. Full article

This study aimed to investigate the effect of human heart-rate synchronization with variations in the geomagnetic field (GMF) (“biogeophysical synchronization effect”). We analyzed 403 electrocardiogram (ECG) recordings of 100 or 120 min that were obtained in 2012–2023 from two middle-aged female volunteers in good health. The minute-value series of the GMF vector from the INTERMAGNET network was used. Each ECG recording was individually examined using cross-correlation and wavelet analysis. The findings from two separate experimental sets (306 recordings from Volunteer A and 97 from Volunteer B) displayed notable similarity in all aspects analyzed: (1) For both participants, the biogeophysical synchronization effect is observed in 40–53% of the recordings as a statistically significant (p < 0.0045) correlation between minute heart-rate (HR) time-series values and at least one of the horizontal components of the GMF, with a time shift between values of [−5, +5] min. (2) Wavelet analysis indicates that the spectra of the HR series and at least one GMF component exhibit similarity in 58–61% of cases. (3) The synchronization is most evident within the period range between 8–13 min. The probability of the synchronization effect manifestation was independent of the geomagnetic activity (GMA) level, which was recorded during the observations. Full article

A large-scale underwater volcanic eruption occurred at the volcano of Hunga Tonga-Hunga Ha’apai (HTHH) on 15 January 2022. At present, there is no consensus on the ionospheric response characteristics and interaction mechanism during volcanic eruptions. Based on the Global Navigation Satellite System (GNSS), AQUA satellite’s Atmospheric Infrared Sounder (AIRS), the experiment studies the response characteristics of the ionosphere and gravity waves during the eruption of the volcano and their interaction mechanisms and the International Real-Time Geomagnetic Observation Network (INTERMAGNET). First, a geomagnetic anomaly was detected before the eruption, which caused variations in the ionospheric VTEC (Vertical Total Electron Content) by about 15 TECU. Based on the IGS (International GNSS Service) observations, the VTEC distribution between 60° north and south latitudes was retrieved. The results show that before and after the eruption of Tonga Volcano, significant ionospheric anomalies were observed to the south, northwest and southwest of the volcano, with a maximum anomaly of 15 TECU. The study indicates that the geomagnetic anomaly disturbance is one of the precursors of volcanic eruption and has a certain degree of impact on the ionosphere. A correlation between geomagnetic anomalies and ionospheric anomalies was found to exist. The vast impact from the volcanic eruption excites gravity waves over the surface, which then propagate longitudinally, further perturbing the ionosphere. It is also detected that the ionospheric anomaly perturbation has a high coincidence effect with the gravity wave anomaly. Therefore, the gravity waves generated by atmospheric variations are used to explain the ionospheric perturbation phenomenon caused by volcanic eruptions. Full article

High-quality geomagnetic measurements are widely used in both fundamental research of the magnetic field and numerous industrial applications. However, vector data measured by fluxgate sensors show a dependency on temperature due to sensitive coil core material and components of the sensor electronics. Here, we propose a new method for detecting and eliminating temperature dependence in magnetic observatory data. The method is designed to correct temperature drifts in variation vector magnetometer measurements when preparing quasi-definitive data according to an INTERMAGNET standard. A special feature of the method is the semi-automatic adjustment of localization intervals for temperature correction, which prevents boundary jumps and discontinuities in the course of sequential data processing over long intervals. The conservative nature of the approach implies the minimization of the original data amount subjected to correction. The described method is successfully applied in the routine monthly preparation of quasi-definitive data of the Saint Petersburg Observatory (IAGA-code SPG) and can be efficiently introduced at other magnetic observatories worldwide. Full article

We analyze vertical total electron content (vTEC) variations from the Global Navigation Satellite System (GNSS) at different latitudes in different continents of the world during the geomagnetic storms of June 2015, August 2018, and November 2021. The resulting ionospheric perturbations at the low and mid-latitudes are investigated in terms of the prompt penetration electric field (PPEF), the equatorial electrojet (EEJ), and the magnetic H component from INTERMAGNET stations near the equator. East and Southeast Asia, Russia, and Oceania exhibited positive vTEC disturbances, while South American stations showed negative vTEC disturbances during all the storms. We also analyzed the vTEC from the Swarm satellites and found similar results to the retrieved vTEC data during the June 2015 and August 2018 storms. Moreover, we observed that ionospheric plasma tended to increase rapidly during the local afternoon in the main phase of the storms and has the opposite behavior at nighttime. The equatorial ionization anomaly (EIA) crest expansion to higher latitudes is driven by PPEF during daytime at the main and recovery phases of the storms. The magnetic H component exhibits longitudinal behavior along with the EEJ enhancement near the magnetic equator. Full article

This article describes a method for recognizing sudden commencement events using digital differentiating filters. This method is applied to INTERMAGNET observatory data. Maximum amplitude derivatives for the magnetic components (X, Y, Z) and the total intensity (F) of the geomagnetic field are introduced, and the decision-making rule is formulated. The authors developed a procedure for selecting optimal digital differentiating filters. Estimates of probabilities of correct and false recognition of sudden commencements were obtained. The calculations of the probabilistic characteristics have confirmed the effectiveness of the method. Full article

The longitudinal variability and local time of equatorial electrojet (EEJ) current using simultaneous data recorded by ground and satellite magnetometers at different levels of solar activity were investigated. In this study, we used data from the CHAMP and Swarm satellites to obtain EEJ current measurements around the globe. The ground data were provided by the MAGDAS, INTERMAGNET, and IIG networks. The ground observation was carried out by analyzing magnetometer data in four different sectors: the South American, Indian, African, and Southeast Asian sectors. These ground data were normalized to the dip equator to overcome the latitudinal variation of each station. The analysis for both measurements was performed using quiet day data. Both the ground and satellite data were categorized according to solar activity level; low, moderate, and high. The results revealed that, during the low solar activity, there was a good agreement between the longitudinal profiles of the EEJ measured using the satellite and the ground data. In general, strong correlations were obtained in most of the sectors where ground data were available between 11 and 13 local time (LT). Besides that, our analysis revealed that the different times of maximum EEJ appearances were seasonally dependent only at certain longitude sectors. Full article