Doctor of Technical Sciences Minligareev V.T. (1); Doctor of Physics and Mathematics Kopytenko (2); Candidates of Physics and Mathematics Merkuryev S.A. (2, 3), Aryutyunyan D.A. (1, 4), Grigoryev E.K. (5); Candidate of Technical Sciences Kuznetsov K.M. (4); Doctor of Physics and Mathematics Maximochkin V.I. (4)
The study of the drift of the Earth’s South Magnetic Pole and the magnetic field of the World Ocean in the Round-the-World Expedition of the oceanographic research vessel of the Russian Navy "Admiral Vladimirsky"
For the Earth, the magnetic field is vital in the global sense, acts as a magnetic shield from solar and galactic cosmic rays (SCR and GCR) for all living things and for the infrastructure of technical means and systems created by mankind across the planet. The Earth’s magnetic field (EMF) has been attracting the attention of mankind since ancient times, and it is used it to solve a wide range of problems. Initially, this was connected with seafaring and the need to solve the navigation problem using a marine compass, the history of which has more than two millennia. Currently, the characteristics of the magnetic field are used for the navigation of ships, aircraft, spaceships, and for mining. There are magnetic sensors in almost every mobile phone.
Therefore, observation of the Earth's magnetic field (EMF), its "behavior" and constant monitoring of its poles is especially important throughout the entire period of solar activity.
1. The main magnetic field of the Earth. Magnetic variations
According to modern concepts, the Earth’s magnetic field at any point on the earth’s surface and in near-Earth space can be represented in the form of three components: the main (normal) dipole field, variation field, and magnetic anomalies field (Fig. 1.2).
The main magnetic field, extending for over several radiuses of the Earth, protects us from the influence of the flow of protons and electrons coming from solar flares, as well as from galactic rays coming from outer space. The state of the magnetic field in near-Earth space is monitored by ground-based means and by numerous spacecraft, in particular by the Russian geostationary hydrometeorological and heliogeophysical satellites of the “Elektro-L” series.
The fluxes of SCR and GCR, disturbing the ionosphere and magnetosphere of the Earth, “bring” the variations of the magnetic field to the Earth's surface. The contribution of the variation field to the total Earth’s magnetic field can reach 5-10%, and is determined according to the data from a network of stationary recording magnetometers, the main of which is the Roshydromet State Observation Network. The head institution for magnetic observations of the State Observation Network is E.K. Fyodorov Institute of Applied Geophysics (FSBI IAG). It should be noted that significant changes in the magnetic field, which occur primarily during intense solar flares, cause magnetic storms on Earth that belong to the category of dangerous heliogeophysical phenomena (DHP). Magnetic storms in terms of intensity of development, duration or moment of occurrence can pose a serious threat to energy systems, pipelines, communication systems, navigation, spacecraft, and other high-tech systems, and can cause significant property damage. As a result of exposure, magnetic storms in some cases can affect people's health. Therefore, the role of magnetic observations in monitoring and forecasting DHP is extremely important and cannot be underestimated. Magnetic observations are an essential part of the State Observation Network. In addition, it is necessary to monitor the movement of the magnetic poles, as it is important to know their location when determining the magnetic declination for navigation, determining the degree of danger of the polar regions during strong magnetic disturbances.
The sources of the main magnetic field are in the Earth’s core. The contribution of the main field to the Earth’s magnetic field, for most regions of the Earth, is the most prominent one and varies from 80 to 98%. Studies have shown that the main field changes over time. It is characterized by the presence of secular variations. Recently, these changes have accelerated greatly. The fundamental research in this area is carried out by the academic institutions, in particular Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS and its St. Petersburg branch (IZMIRAN).
The criteria of the main field (Fig. 3) are determined according to international models, the main of which are: IGRF (International geomagnetic reference field), WMM (World Magnetic Model).
Among the problems solved by fundamental geophysics, it is worth to highlight the tasks of determining the age of the oceanic crust, studying its structure, mechanisms of formation and evolution. The origin of the Earth's magnetic field was considered by Albert Einstein as one of the three most important unsolved problems in physics. Although now we know that the magnetic field is created as a result of convection in the liquid metallic outer core of the Earth, where the self-generating action of the dynamo does not allow the field to decay. But the detailed physics of the work of geodynamo has not been fully studied.
Currently, there is a tendency toward a decrease in the Earth’s dipole magnetic moment, which is partly due to the South Atlantic Anomaly, where the field on the earth’s surface is now about 35% weaker than average. If this tendency continues, this can lead to the dipole field decay. The answer to the question of how long the current decay rate of the dipole field will be maintained, whether the inversion of the main magnetic field is going to follow, is of more than academic interest. As noted earlier, it is the dipole magnetic field (the main field) that protects our planet from SCR and GCR.
When studying the spatial structure of the Earth’s main magnetic field and the dynamics of its changes, a special role should be assigned to the measurements in the waters of the World Ocean, since there are practically no magnetic observatories. For more than 30 years (from 1953 to 1991) on board the sailing-motor schooner “Zarya” (IZMIRAN), systematic measurements of four components of the geomagnetic field — the modulus of the strength vector, the horizontal and vertical components, and magnetic declination — have been carried out, on the basis of which an extensive database has been created. In the course of these studies, marine secular variation points were created, which helped to track the change dynamics of the EMF at certain points in the World ocean. The key regions where the measurements help to correct the global models of the geomagnetic field are the polar regions, i.e. areas that are close to the South and North Magnetic Poles.
Thus, determining the position of the North and South Magnetic Poles and their movement is an important and relevant fundamental and applied task. Investigation of the migration features of the Earth’s magnetic poles helps to understand the nature of the main magnetic field generation.
2. The anomalous Earth’s magnetic field
The anomalous component of the Earth’s magnetic field (AEMF) is the magnetic field of regional and local magnetic anomalies, the sources of which are located in the Earth’s crust (Fig. 2,4). The AEMF exists due to the irregularity of the magnetic properties of rocks composing the Earth's crust, and it reflects the features of its structure, the history of formation and development. The AEMF is technically a time-stable component of the magnetic field, which can only change as a result of tectonic processes or major anthropogenic activities.
The study of the parameters of the AEMF is carried out for geological exploration, studies in the field of Earth sciences, and is also used in the Earth’s geophysical fields autonomous navigation systems.
To study the features of the magnetic field of the World ocean, towed (outboard) marine magnetometers are used. In addition to solving academic scientific problems, magnetometric systems of this type are traditionally actively used for conducting geological exploration, for engineering and archaeological surveys in the waters of the World Ocean by leading domestic and foreign service, and research and production companies (Fig. 5). One of the domestic enterprises that carries out marine magnetometric surveys is JSC “Yuzhmorgeologiya”. They are the pioneers of the establishment of the marine magnetic survey method in our country. Over the past five years (2015-2020) alone, the company (subsidiary of JSC “Rusgeology”) has performed more than 100,000 linear kilometers of magnetometric measurements in the waters of the Russian shelf, foreign countries and the World Ocean.
3. Magnetic poles drift studies
The magnetic pole is a wandering point on the surface of the Northern and Southern hemispheres of the Earth, where the geomagnetic field is directed vertically (the horizontal component is zero). Despite the fact that all lines of equal magnetic declination converge at the magnetic pole, the declination at the pole itself is not defined. All compasses are directed to the South or North magnetic poles, but due to the presence of a non-dipole component of the EMF, the arrows do not point directly to the poles. And even in the polar regions, the convergence of the lines of magnetic declination is not radial.
Until 2019, models of the 2015 epoch had been used to calculate the main field. In all epochs, the magnetic poles were drifting. The drift velocity of the North magnetic pole in the 1970s was 10 km / year, in 2001 - 40 km / year, in 2004 - 60 km / year, in 2015 - 48 km / year. Since 2016, the unusually high speed at which the Earth’s North magnetic pole is shifting has led to serious errors in the calculations of the 2015 model. At the beginning of 2019, the discrepancy in the location of the North magnetic pole was about 40 km. To eliminate such errors in the beginning of 2019, an early update of international models of Earth’s magnetic field started. The WWM was updated by the US National Geophysical Data Center (NGDC) in February; an updated version of the WMM 2020 was released in December (Fig. 6).
In December 2019, the International Association of Geomagnetism and Aeronomy (IAGA) released the next version of the model - IGRF-13. These models are necessary for the functioning of both professional navigation systems and home navigators, including in mobile phones. With slower speeds and non-coaxially, the position of the South Magnetic Pole (SMP) also changed. Figure 6 clearly shows the convergence site of the isogons (lines of equal magnetic declination) between Australia and Antarctica. This is the SMP.
The task of determining the position of the South Magnetic Pole has a long history. The first geomagnetic measurements (declination measurements) in the Antarctic region were performed during the second voyage of J. Cook (1772-1775). However, no estimates were made of the location of the SMP. The first experimental determination of its location was made during the round-the-world Antarctic expedition of the Russian navigators Bellingshausen and Lazarev (1819-1821). Shortly after the expedition to the North Magnetic Pole, the German physicist Johann Carl Friedrich Gauss calculated, based on the spherical harmonic analysis, that the SMP was located at a point with coordinates 66 ° S, 146 ° E. It was only on January 16, 1909, that the British Antarctic expedition led by Ernest Shackleton (the “Nimrod” expedition) managed to reach this point and carry out measurements. Later, the SMP was determined in 1912, 1931, 1951, 1962. (Fig. 7).
Continuing the traditions of Russian navigators and discoverers of Antarctica, Lazarev and Bellingshausen, the sailors of the USSR Navy, with the participation of SPbF IZMIRAN employees, determined the location of the South Magnetic Pole during the first round-the-world expedition on the oceanographic research vessels “Admiral Vladimirsky” and “Faddey Bellingshausen” (1982-1983). A few tacks were made in the area of the SMP in order to determine its location. The research supervisor was Rear Admiral L.Mitin. (Fig. 8).
The most recent observation of the South Magnetic Pole was made by the Australian Geoscience Organization on the “Sir Hubert Wilkins” vessel in 2000.
4. Round-the-world expedition of the oceanographic research vessel of the Russian Navy “Admiral Vladimirsky” 2019-2020
In 2019-2020, by the decision of the Minister of Defense, in honor of the 200th anniversary of the discovery of Antarctica and the 250th birthday anniversary of Admiral I.F.Kruzenshtern, the round-the-world expedition on the oceanographic research vessel of the Russian Navy “Admiral Vladimirsky” was successfully conducted.
One of the tasks of the Antarctic expedition was the en-route measurement of the magnetic field parameters of individual sections of the World Ocean; the determination of the coordinates of the South Magnetic Pole in the D'Urville Sea (near Adélie Land of Antarctica); as well as the determination of the magnetic pole discrepancies in the world models. This task, aboard the oceanographic research vessel, was carried out by the joint geophysical group of the FSBI IAG, Lomonosov Moscow State University (Faculty of Physics and Geology), IZMIRAN and JSC “Yuzhmorgeologiya” with the support of the Russian Geographical Society, the Hydrometeorological Service of the Armed Forces of Russian Federation, and the Hydrographic Service of the Russian Navy.
As part of the geophysical group for measuring the parameters of the magnetic field, the following people were conducting the research: Ilya Grushnikov - Department of Earth Physics, Faculty of Physics, MSU (Moscow); Vadim Soldatov - IZMIRAN (St. Petersburg); Mikhail Kuzyakin – “Yuzhmorgeologiya” (Gelendzhik) (Fig. 10).
The research program, the survey coordination were done by the specialists and management of the FSBI IAG, IZMIRAN, and the Geological Faculty of Moscow State University. Determining the characteristics of the EMF (the modulus and the magnetic flux density) in the World ocean is a difficult task. The intrinsic and the induced magnetic fields of the vessel require the use of towed marine magnetometers. In addition, the absence of the stationary recording magnetometers in the ocean makes it difficult to take into account the variable component of the Earth’s magnetic field. To solve the measurement problems during the expedition, two types of instruments were used. The first is a traditional towed magnetometer. At present, most magnetometric measurements in the waters of the World ocean are carried out by towed proton marine magnetometers, and the measured value is the modulus of the magnetic field strength.
To accomplish the tasks of the expedition, the JSC “Yuzhmorgeologiya” provided a set of magnetometric equipment and an experienced qualified operator who accompanied the progress of the work. An important factor that influenced the successful completion of the work to clarify the position of the SMP was the company's extensive experience and understanding of the specifics of performing magnetometric measurements in the polar regions (Fig. 11).
Modular areal mapping was carried out using towed proton marine magnetometers to measure the modulus of the magnetic flux density. They were working in the differential mode for observing and taking into account variations in the magnetic field. The Earth’s magnetic field parameters were measured by two fish with sensors using the nuclear Overhauser effect, pulled sequentially one after another at a distance of at least 300-400 m behind the ship in order to minimize the influence of the vessel’s magnetic field.
The knowledge of the magnetic field components is extremely important for determining the position of the SMP, therefore, during the survey, three-component magnetometers were additionally used.
The component measurements were carried out using the MVC-2 stationary recording magnetometers complex developed by IZMIRAN and consisting of 3 torsion-type sensors. In conjunction with this complex, a component magnetometer with sensors based on the magnetoresistance was used. The sensors were oriented along the longitudinal, transverse and vertical axes of the ship. All magnetometric equipment was in the laboratory located at the stern of the vessel in such a way that the sensors were positioned as far as possible from the vessel's hull in order to reduce the influence of the ship’s magnetic field on the sensor readings (Fig. 12).
This work was carried out by V. Soldatov, a researcher at the Laboratory of Marine Geomagnetic Research, SPbF IZMIRAN. Component magnetometric measurements were carried out almost continuously at all stages of the expedition, which allowed to perform tens of thousands of linear kilometers of marine component magnetic surveys. This is of great value for the study of the Earth's magnetic field, since outboard measurements were sometimes not carried out due to weather conditions. The total measurements volume is several terabytes and requires careful laboratory processing, which will be performed by the laboratory staff.
During the expedition, the measurements were carried out by magnetometers of both types, which made it possible to analyze and compare these measurements and constantly monitor the operation of the equipment. During the voyage, the vessel’s intrinsic and induced magnetic fields were studied several times (deviation study). To do this, it was necessary to determine the areas and the methodology, to coordinate proposals with the leadership of the expedition. Grushnikov I.Yu., Graduate student of the Department of Earth Physics, Faculty of Physics, Lomonosov Moscow State University, was doing this during the expedition. (Fig. 13.14).
The task to determine the SMP was scheduled for early April 2020 according to the plan of the expedition. Despite severe storms in the Southern Ocean - winds exceeding 30 meters per second and 7-meter waves - the “Admiral Vladimirsky” crew completed one of the main tasks of the expedition.
On April 6, 2020, the “Admiral Vladimirsky” vessel arrived at the Earth’s magnetic field survey area in D'Urville Sea in the region of Adélie Land (Antarctica) to determine the position of the SMP. For more than 48 hours, specialists, crew members were continuously conducting surveys of the magnetic field parameters in difficult weather conditions. To determine the position of the magnetic pole, the expedition carried out areal marine magnetometric mapping using a three-component and a towed proton marine magnetometers (Fig. 15-16).
An experimental determination of the position of the magnetic pole implies a magnetic survey, from which it is possible to determine the area where the field is directed almost vertically. The fact that the ship was positioned directly in the area of the Earth’s magnetic field location was, for example, evidenced by the “crazy” compass needle, which changed direction with the vessel, turned 180 degrees, turned around in all directions for no reason.
For the parametric determination of the position of the SMP, an areal observation network was designed in advance. Figure 17 shows the positions of the pole according to the data of the international geomagnetic field model IGRF-13 in 2020, as well as the positions in the previous years and the predicted position. Along with the data of the IGRF-13 model, the figure shows the positions of the SMP according to the data of the IGRF-12 model and WMM model. If we consider the history of the drift of the SMP, we can see that its trajectory is described not by a straight line, but by a curved line (Fig. 16). In 2019 and 2020, it was shifting in the west-south-west direction. Based on the position of the pole according to various models and its shift trend in previous years, the designed observation network has been expanded to the south-west relative to the position of the pole according to the IGRF-13 model.
Figure 17 shows the position of the tacks of a detailed marine magnetic survey of the Southern Ocean off the coast of Antarctica, performed by the oceanographic research vessel “Admiral Vladimirsky”, with the aim of determining the position of the SMP (on the right). Yellow circles - the position of the pole for the epoch indicated by numbers; green stars - the position of the SMP on the WMM and IGRF-12 models.
The magnetic variations on the day of the survey (taken from the nearest magnetic observatories: Dumont D'Urville (France) in Antarctica, and on Macquarie Island (New Zealand)) will be used to amend the obtained data. The magnetic measurements data in the D'Urville Sea, in the area of the SMP, will be transferred to the organizations of the expedition participants, where it will undergo office studies, comparison with other parameters, and undergo the procedure of final clarification of the position of the Earth’s South magnetic pole. The consolidated final report on the research of the Earth’s magnetic field will be presented at a meeting of the Russian Geographical Society at the end of 2020.
To summarize, the crew of the oceanographic research vessel “Admiral Vladimirsky” carried out work in the area of the South Magnetic Pole near the coast of Antarctica 20 years after the last determination of the magnetic pole. This fact is a serious contribution of Russian science (with the undeniable support of the Russian Navy and the Russian Geographical Society) to the world treasury of achievements in understanding the fundamental geophysical processes taking place on our planet for fundamental and applied tasks.
Taking into account the importance and global nature of such studies, it is necessary to determine the prospects for research and monitoring of the Earth's magnetic field. It is advisable to combine ground-based observation networks and individual magnetic observatories of Roshydromet, RAS, the Ministry of Science and Higher Education, and Rusgeology.
In international cooperation within the framework of the International Association of Geomagnetism and Aeronomy (IAGA), in connection with the acceleration of the movement of the magnetic poles, it is necessary to reach agreements on regular monitoring of the magnetic poles to refine world models.
Using the experience of the International Geophysical Year - IGY (at the height of the Cold War of 1957-1958), on the eve of the new 25th solar cycle, and in difficult international relations, it is advisable to conduct the International Magnetic Field Year(or a new IGY) in order to study and forecast “health” and the state of our planet.
1. E.K. Fyodorov Institute of Applied Geophysics of Roshydromet (FSBI IAG).
2. St. Petersburg branch of Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS (SPbF IZMIRAN).
3. St. Petersburg State University.
4. Lomonosov Moscow State University.
5. JSC “Yuzhmorgeologiya”, Rusgeology.
The team of authors is grateful to everyone who participated in the training of the specialists, processing of the measurement results, delivery of the equipment for the expedition; who promptly organized the transfer of information, provided communication and coordination along the route of the oceanographic research vessel “Admiral Vladimirsky”, provided support and scientific advice.
1. The Head of the Expedition of the “Admiral Vladimirsky” oceanographic research vessel, Deputy Head of the Department of Navigation and Oceanography of the Ministry of Defense of the Russian Federation, Oleg Dmitrievich Osipov.
2. Head of E.K. Fyodorov Institute of Applied Geophysics of Roshydromet (FSBI IAG), Doctor of Physics and Mathematics, Andrei Yuryevich Repin, and the employees of the institute.
3. Lomonosov Moscow State University. Faculty of Physics. Head of the Department of Physics of the Earth, Doctor of Physics and Mathematics, Professor Vladimir Borisovich Smirnov, and the employees of the department.
4. Lomonosov Moscow State University. Faculty of Geology. Head of the Geophysical Department, Doctor of Physics and Mathematics, Professor Andrei Aleksandrovich Bulychev; Associate Professor of the Department, Candidate of Geologo-Mineralogical Sciences, Ivan Vladimirovich Lygin; the employees and students of the department.
5. St. Petersburg branch of Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS (SPbF IZMIRAN). The researchers at the Department of Geomagnetic Research: Candidate of Physics and Mathematics, Demina I.M; Candidate of Physics and Mathematics, Ivanov S.A.; Candidate of Engineering Sciences, Sergushin P.A., Zaitsev D.B., Levanenko V.A., Petlenko A.V.
6. The Managing Director of the JSC “Yuzhmorgeologiya”, Yegor Mikhailovich Krasinsky (Russian geological holding “Rusgeology”)
7. Arctic and Antarctic Research Institute of Roshydromet (FSBI "AARI"). The Director of the institute, Doctor of Geographic Sciences, Aleksandr Sergeevich Makarov; Head of the Russian Antarctic Expedition (RAE), Candidate of Physics and Mathematics, Aleksandr Vyacheslavovich Klepikov; Head of the Department of Geophysics, Candidate of Engineering Sciences, Alexey Sergeevich Kalishin.
8. Head of the Hydrometeorological Service of the Armed Forces of the Russian Federation, Vladimir Viktorovich Udrish; and the Service employees.
9. The Russian Hydrographic Service. Candidate of Engineering Sciences, Sergey Vladimirovich Protsayenko.
Photos from the “Admiral Vladimirsky” oceanographic research vessel were provided by the expedition members, the press service of the Russian Geographical Society and RIA Novosti.
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