Ocean geomagnetic diurnal variation station

Abstract

The invention discloses a marine geomagnetic diurnal variation station, which comprises a pressure-resistant sealed cabin, a proton precession magnetometer system for measuring the intensity of a geomagnetic field, a power supply system integrated in the pressure-resistant sealed cabin, a positioning and time synchronization module, an environment monitoring unit and the like, and is characterized in that the pressure-resistant sealed cabin is of a glass floating ball structure, and the interior of the pressure-resistant sealed cabin is divided into an upper part and a lower part; the power supply system comprises a plurality of lithium iron phosphate batteries, and the host unit comprises a CPU board, a simulation board and the like, and is further provided with a deck control unit and the like. The geomagnetic field intensity can be accurately measured, interference is reduced through the watertight cable structure, position information and time calibration can be provided, the internal state of the cabin can be monitored, parameter configuration, data export and other functions can be achieved, the device can work well on the land and in the deep sea, and the alarm can be triggered when abnormity occurs.

Description

Technical Field

[0001] This application relates to the field of marine geomagnetic exploration, and in particular to a marine geomagnetic diurnal variation station. Background Technology

[0002] Marine geomagnetic surveying is used to explore seafloor geological structures, mineral resources, and topography. In geomagnetic measurements, changes in the geomagnetic field are not only related to geological features but also influenced by diurnal variations caused by solar activity; therefore, observation and correction must be performed using geomagnetic diurnal variation stations. Traditional geomagnetic diurnal variation stations are typically located on land or in nearshore areas, with an effective control range generally not exceeding 300 kilometers. However, in offshore and open-ocean geomagnetic surveys, because research vessels are far from land, it is impossible to establish diurnal variation observation stations within the effective range, leading to a significant reduction in the accuracy of magnetic measurement data and even the generation of false anomalies, seriously affecting the reliability of geological interpretation.

[0003] Currently, the most widely used marine geomagnetic diurnal variation stations internationally primarily employ Overhauser magnetometer technology, such as the SENTINEL magnetometer manufactured by Marine Magnetics in Canada. These magnetometers, based on dynamic nuclear polarization, offer advantages such as low power consumption and high resolution. However, in recent years, there has been a decline in equipment quality and after-sales service, with some devices experiencing immediate damage upon opening or premature failures, impacting the sustainability of actual observation work. Furthermore, this technology is monopolized by foreign manufacturers, posing technological barriers and supply risks to domestic users.

[0004] To address the aforementioned issues, China has begun developing geomagnetic diurnal variation stations based on proton precession magnetometers. Proton precession magnetometers use hydrogen-containing nuclear media (such as water or kerosene) as the detection medium, measuring magnetic field strength by the precession frequency of polarized protons in the Earth's magnetic field. Although this technology is relatively mature in China, its power consumption is significantly higher than that of Overhauser magnetometers, and issues related to pressure tolerance, electromagnetic interference, and long-term endurance need to be addressed for deep-sea applications. Existing seabed geomagnetic diurnal variation stations mostly employ mooring systems, deploying the magnetometer along with buoys, release devices, and gravity anchors to the seabed. However, these systems suffer from limited battery capacity, interference from magnetic components affecting measurement accuracy, and low retrieval reliability. Therefore, there is an urgent need for a geomagnetic diurnal variation station suitable for deep-sea environments, with long endurance and high stability. Summary of the Invention

[0005] To improve the stability and navigation capability of the equipment, this application provides a marine geomagnetic diurnal variation station.

[0006] The technical solution for a marine geomagnetic diurnal variation station provided in this application is as follows: A marine geomagnetic diurnal variation station, comprising: Pressure-resistant sealed chamber; The proton precession magnetometer system is used to measure the intensity of the geomagnetic field. It includes a main unit located inside the pressure-resistant sealed chamber and a probe unit located outside the pressure-resistant sealed chamber. A watertight cable structure is provided between the probe unit and the main unit to extend the distance between the main unit and the probe unit and reduce interference. The power supply system, integrated within the pressure-resistant sealed chamber, provides power to the proton precession magnetometer system. The positioning and time synchronization module is used to provide location information and time calibration; The environmental monitoring unit is used to monitor the internal condition of the cabin.

[0007] By adopting the above technical solution, the main unit and probe unit of the proton precession magnetometer system are arranged separately via a watertight cable. This effectively increases the physical distance between the magnetically sensitive probe and the electronic components within the main unit, significantly reducing the impact of electromagnetic interference generated by the main unit during operation on the accuracy of geomagnetic field measurements. Integrating the main unit, power system, and other core components into a pressure-resistant sealed chamber provides unified and robust protection for the entire system, enabling it to withstand the high-pressure environment of the deep sea. This integrated design also simplifies the deployment and retrieval process on the seabed. The power system is directly integrated within the chamber to supply power to the magnetometer system, ensuring a stable energy supply. The positioning and time synchronization module provides accurate time and position references for measurement data, a prerequisite for effective diurnal variation correction. The environmental monitoring unit can monitor the internal status of the equipment in real time, ensuring long-term stable operation. This solution comprehensively addresses the electromagnetic interference, pressure resistance protection, and system integration challenges faced by proton precession magnetometers in deep-sea applications.

[0008] Preferably, the pressure-resistant sealed chamber is a glass float structure, and the internal part of the pressure-resistant sealed chamber is divided into upper and lower parts, with the upper part accommodating the host unit and data acquisition and control unit, and the lower part accommodating the power system.

[0009] By adopting the above technical solution, the glass buoy structure itself possesses excellent pressure resistance and non-magnetic properties, making it very suitable as a carrier for deep-sea exploration equipment. Dividing the pressure-resistant sealed chamber into upper and lower sections, with the upper section housing the main unit and the lower section housing the power system, this partitioned layout utilizes the weight of the batteries to lower the overall center of gravity of the equipment, enhancing its stability on the seabed and preventing capsizing. Simultaneously, it achieves rational planning and optimized utilization of the internal space, resulting in a more compact structure.

[0010] Preferably, the power system includes multiple lithium iron phosphate batteries with a total capacity of not less than 2000Wh.

[0011] By adopting the above technical solution and using multiple lithium iron phosphate batteries for power supply, which has high energy density and stable discharge characteristics, the configuration with a total capacity of not less than 2000Wh can provide sufficient energy reserves for the proton precession magnetometer system with relatively high power consumption. This solves the technical bottleneck of proton magnetometers being unable to achieve long-term continuous observation due to high power consumption, and is the key foundation for achieving the equipment's endurance of more than 90 days.

[0012] Preferably, the host unit includes a CPU board and an analog board. The CPU board is configured to control the analog board to send pulses to the probe unit, causing the probe unit to generate a proton precession effect and feeding back an analog signal to the analog board. The CPU board then analyzes the analog signal to obtain the magnetic field value.

[0013] By adopting the above technical solution, the host unit uses a separate design of CPU board and analog board, realizing a professional division of labor between digital control and analog signal processing. The CPU board is responsible for core logic control and data operation, while the analog board is dedicated to processing the weak analog signals returned by the probe. This architecture can effectively reduce high-frequency interference from digital circuits to the analog signal acquisition path, thereby improving the signal-to-noise ratio of magnetic field measurement and the accuracy of calculation results.

[0014] Preferably, the positioning and time synchronization module is a GPS or Beidou receiver that supports network time synchronization and crystal oscillator timekeeping functions. When working on land, it calibrates the collected time, and when working in the deep sea, it relies on the crystal oscillator to maintain the timekeeping.

[0015] By employing the above technical solutions, precise time synchronization and positioning are achieved using GPS or BeiDou receivers before equipment deployment, ensuring the accuracy of the initial timestamp. Once the equipment is submerged in the deep sea and unable to receive satellite signals, it automatically switches to high-precision crystal oscillators for timekeeping, maximizing the long-term accuracy of the time system. This ensures that the collected geomagnetic data sequences have a precise time reference, which is crucial for subsequent analysis of diurnal variations and short-period disturbances in the geomagnetic field.

[0016] Preferably, it also includes a deck control unit. The pressure-resistant sealed chamber is provided with a communication control interface. The communication control interface of the deck control unit is connected to the pressure-resistant sealed chamber and is used to realize parameter configuration, data export and equipment start-up and shutdown.

[0017] By adopting the above technical solution and setting up communication control interfaces on the deck control unit and the hull, operators can complete all critical operations such as powering on / off the equipment, setting operating parameters, and exporting data without opening the pressure-resistant sealed hull. This greatly simplifies the operation process, avoids the potential risks to the hull's sealing caused by frequent opening of the hull, and effectively prevents problems such as condensation inside the hull caused by the entry of outside air, thus improving the reliability and ease of maintenance of the equipment.

[0018] Preferably, the pressure-resistant sealed chamber is provided with a sensor interface for connection to the watertight cable structure.

[0019] By adopting the above technical solution and setting up a dedicated sensor interface for connection with a watertight cable structure, a standardized and detachable connection between the probe unit and the main unit compartment is achieved. This design not only ensures the sealing reliability of the connection and adapts to the deep-sea environment, but also facilitates the installation, replacement, and maintenance of the probe, improving the modularity and engineering practicality of the equipment.

[0020] Preferably, the pressure-resistant sealed chamber is provided with an exhaust port for connecting to a vacuum pump. By evacuating the air from the inside of the pressure-resistant sealed chamber and then sealing the exhaust port, the vacuum state of the pressure-resistant sealed chamber is maintained.

[0021] By adopting the above technical solution, the interior of the pressure-resistant sealed chamber is evacuated (e.g., to 0.5 bar) through the exhaust port, and the interior of the chamber is kept under negative pressure, which has multiple benefits: First, the negative pressure environment helps to detect the sealing integrity of the chamber, and any leakage will directly lead to a pressure rebound; second, after most of the air is evacuated, condensation on the inner wall of the chamber can be prevented in the low temperature environment of the deep sea, avoiding damage to the precision circuits by water vapor; finally, it also reduces the external pressure difference that the chamber bears.

[0022] Preferably, the environmental monitoring unit includes a voltage and current meter and a pressure gauge. The voltage and current meter is installed on the power supply line between the power system and the host unit and is used to monitor and display the current and voltage usage and power status of the host unit in real time. The pressure gauge is used to test the pressure inside the pressure-resistant sealed chamber. When the voltage and current meter or the pressure gauge detects an abnormality, an alarm is triggered.

[0023] By adopting the above technical solution, the environmental monitoring unit monitors the power system output in real time using voltage and current meters, which can intuitively reflect the power consumption status and battery health of the equipment, providing a basis for assessing the remaining working time. The pressure gauge continuously monitors the vacuum level inside the chamber, serving as a direct indicator of the chamber's sealing integrity. When any parameter becomes abnormal, the system can trigger an alarm, prompting personnel to intervene promptly. This proactively warns of equipment status and prevents observation mission failures and data loss due to power depletion or chamber leakage, greatly improving the reliability of the entire system and the success rate of data acquisition.

[0024] In summary, this application includes at least one of the following beneficial technical effects: 1. By separating the main unit and probe unit of the proton precession magnetometer system through a watertight cable, the impact of electromagnetic interference generated by the main unit during operation on the accuracy of geomagnetic field measurement can be reduced, thus solving the electromagnetic interference problem faced by the proton precession magnetometer in deep-sea applications. 2. The main unit, power system and other core components are integrated into a pressure-resistant sealed cabin, which can withstand the high pressure environment in the deep sea, simplify the operation process of deployment and recovery on the seabed, and solve the pressure protection and system integration problems faced by the proton precession magnetometer in deep-sea applications; 3. The power supply system is integrated inside the cabin to power the magnetometer system, ensuring a stable energy supply. The positioning and time synchronization module provides accurate time and position references for measurement data. The environmental monitoring unit monitors the internal status of the equipment in real time, ensuring long-term stable operation of the equipment. 4. Vacuuming the inside of the pressure-resistant sealed chamber through the exhaust port can detect the integrity of the chamber's seal, prevent condensation on the inner walls, and reduce the external pressure difference that the chamber experiences.

[0025] 5. The environmental monitoring unit monitors the equipment status in real time through voltage and current meters and pressure gauges. When the parameters are abnormal, an alarm is triggered, which can prevent the failure of observation missions and data loss due to power depletion or cabin leakage, thereby improving the reliability of the system and the success rate of data acquisition. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the external structure of a marine geomagnetic diurnal variation station according to an embodiment of this application.

[0027] Figure 2 This is a schematic diagram of the internal structure of a marine geomagnetic diurnal variation station according to an embodiment of this application.

[0028] Explanation of reference numerals in the attached drawings: 1. Pressure-resistant sealed chamber; 11. Exhaust / exhaust port; 12. Communication control interface; 13. Sensor interface; 2. Probe unit; 3. Watertight cable structure; 4. Main board unit; 5. Power system; 6. Voltage and current meter; 7. Pressure gauge; 8. Positioning and time synchronization module. Detailed Implementation

[0029] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.

[0030] This application discloses a marine geomagnetic diurnal variation station, referring to... Figure 1 and Figure 2The system comprises a pressure-resistant sealed chamber 1, a proton precession magnetometer system, a power supply system 5, a positioning and time synchronization module 8, and an environmental monitoring unit. The main unit 4 of the proton precession magnetometer system is located inside the pressure-resistant sealed chamber 1, while the probe unit 2 is located outside. The two are connected by a watertight cable structure 3. The power supply system 5, integrated within the pressure-resistant sealed chamber 1, supplies power to the proton precession magnetometer system. The positioning and time synchronization module 8 provides position information and time calibration, while the environmental monitoring unit monitors the internal status of the chamber. This achieves the effects of reducing electromagnetic interference, adapting to the deep-sea environment, and ensuring stable equipment operation. This is because separating the main unit 4 from the probe unit 2 increases the distance between the probe and the electronic components within the main unit 4, reducing electromagnetic interference; integrating the core components within the pressure-resistant sealed chamber 1 allows it to withstand the high pressure of the deep sea; the power supply system 5 ensures power supply; the positioning and time synchronization module 8 provides an accurate reference for data; and the environmental monitoring unit monitors the equipment status in real time.

[0031] Specifically, the pressure-resistant sealed chamber 1 is a glass buoy structure. Glass buoys possess excellent pressure resistance and non-magnetic properties, making them ideal as a carrier for deep-sea exploration equipment. Alternatively, a spherical chamber made of high-strength plastic can be used, achieving the same pressure resistance and reducing magnetic interference. The pressure-resistant sealed chamber 1 is internally divided into upper and lower sections. The upper section houses the main unit 4 and the data acquisition and control unit, while the lower section houses the power system 5. This partitioned layout utilizes the weight of the batteries to lower the overall center of gravity of the equipment, enhancing its stability on the seabed and preventing capsizing. It also achieves rational planning and optimized utilization of the internal space, resulting in a more compact structure. Furthermore, the pressure-resistant sealed chamber 1 is equipped with a sensor interface 13. This interface features a sealed design and can be made of corrosion-resistant metal, such as stainless steel. It connects to the watertight cable structure 3 through this interface, enabling a standardized and detachable connection between the probe unit 2 and the main unit 4. This ensures reliable sealing at the connection point, adapts to the deep-sea environment, and facilitates the installation, replacement, and maintenance of the probe. The pressure-resistant sealed chamber 1 is also equipped with an exhaust / exhaust port 11. This port also features a sealed design and can be made of stainless steel. It is used to connect to vacuum equipment. After evacuating the pressure-resistant sealed chamber 1 (e.g., to 0.5 bar), the exhaust / exhaust port 11 is sealed with a screw containing an O-ring to maintain the vacuum state of the pressure-resistant sealed chamber 1. This helps to check the integrity of the chamber's seal, prevents condensation on the inner wall of the chamber in the low-temperature environment of the deep sea, avoids water vapor damage to precision circuits, and reduces the external pressure difference that the chamber experiences. Additionally, the exhaust function can be achieved by unscrewing the screw.

[0032] Specifically, the proton precession magnetometer system includes a main unit 4 located inside a pressure-resistant sealed chamber 1 and a probe unit 2 located outside the pressure-resistant sealed chamber 1. The probe unit 2 can be a container filled with a hydrogen-containing nucleus medium (such as water or kerosene), constructed as a sealed cylindrical structure, and made of non-magnetic plastic to avoid interference with magnetic field measurements. Alternatively, a spherical probe structure can be used, which can also detect magnetic fields. The probe unit 2 is connected to the main unit 4 via a watertight cable structure 3, specifically an 18-meter-long watertight cable wrapped with a special sealing material to ensure sealing in deep-sea environments and prevent seawater from entering and damaging the cable and equipment. The outer sheath of the watertight cable can be made of rubber, which has good flexibility and waterproof properties, or polyurethane, which has better wear resistance and corrosion resistance. The host unit 4 includes a CPU board and an analog board. The CPU board is a printed circuit board integrating a microprocessor and related control circuits. It is configured to control the analog board to send pulses to probe unit 2, causing proton precession in probe unit 2 and feeding back an analog signal to the analog board. The CPU board then analyzes the analog signal to obtain the magnetic field value. The analog board is a dedicated circuit board for processing the weak analog signal returned from the probe, employing low-noise amplifiers and filtering circuits to improve signal quality. The host unit 4 uses a separate design for the CPU board and analog board, achieving a specialized division of labor between digital control and analog signal processing. This effectively reduces high-frequency interference from digital circuits to the analog signal acquisition path, thereby improving the signal-to-noise ratio of magnetic field measurement and the accuracy of the calculation results.

[0033] Specifically, power system 5 includes nine lithium iron phosphate batteries, installed below the main unit 4. Lithium iron phosphate batteries have high energy density and stable discharge characteristics. Their casings are generally made of aluminum to ensure heat dissipation and protection. Ternary lithium batteries can also be used, but lithium iron phosphate batteries have advantages in safety and cycle life. Each battery has a capacity of 15.6AH and a voltage of 16.8V, totaling nine batteries. The total capacity of power system 5 is no less than 2000Wh. This configuration provides sufficient energy reserves for the relatively high-power proton precession magnetometer system, solving the technical bottleneck of the proton magnetometer's high power consumption, which makes long-term continuous observation difficult. This is a key foundation for achieving a battery life of over 90 days.

[0034] Specifically, the positioning and time synchronization module 8 is a GPS or BeiDou receiver, installed inside the pressure-resistant sealed cabin 1, supporting network time synchronization and crystal oscillator timekeeping functions. The GPS or BeiDou receiver is a module integrating a satellite signal receiving antenna and related processing circuitry. When operating on land, it receives satellite signals to calibrate the acquisition time, ensuring the accuracy of the initial timestamp. When operating in the deep sea, where satellite signals cannot be received, timing is maintained using a high-precision crystal oscillator. The crystal oscillator is a high-precision timing element that can be installed on the circuit board of the positioning and time synchronization module 8, maximizing the long-term accuracy of the time system and ensuring that the acquired geomagnetic data sequence has a precise time reference.

[0035] Specifically, the environmental monitoring unit is installed inside the pressure-resistant sealed chamber 1, and includes a voltmeter / ammeter 6 and a pressure gauge 7. The voltmeter / ammeter 6 can be a digital meter, installed on the power supply line between the power system 5 and the main unit 4. It collects current and voltage signals, converts them into digital signals, and displays them in real time to monitor and display the current and voltage usage and power status of the main unit 4. The pressure gauge 7 can be a high-precision pressure sensor, installed inside the pressure-resistant sealed chamber 1, to test the pressure inside the chamber. When the voltmeter / ammeter 6 or the pressure gauge 7 detects an abnormality, it triggers an alarm. The alarm can be an audible and visual alarm, installed on the surface of the pressure-resistant sealed chamber 1, so that personnel can promptly detect problems. By monitoring the output of the power system 5 and the internal pressure of the chamber in real time, the environmental monitoring unit provides proactive early warning of equipment status, avoiding observation mission failure and data loss due to power depletion or chamber leakage, greatly improving the reliability of the entire system and the success rate of data acquisition.

[0036] This embodiment of the marine geomagnetic diurnal variation station also includes a deck control unit, which is a device for operating and managing the marine geomagnetic diurnal variation station. It can be a device integrating a display screen, operation buttons, and control circuitry, connected to the pressure-resistant sealed chamber 1 via a communication control interface 12. The deck control unit connects to a computer to achieve data transmission and control the internal CPU board. Operators can input commands through the operation buttons on the deck control unit to configure the parameters of the marine geomagnetic diurnal variation station, such as setting the measurement frequency of the proton precession magnetometer system and the timing mode of the positioning and time synchronization module 8; it can also export data stored in the pressure-resistant sealed chamber 1 to an external storage device for subsequent data analysis and processing; simultaneously, the deck control unit can control the on / off operation of the equipment without opening the pressure-resistant sealed chamber 1, avoiding damage to the chamber's seal and problems such as condensation caused by outside air entering the chamber. Specifically, this design is mainly to achieve instrument control and data transmission without opening the sealed chamber.

[0037] The implementation principle of this embodiment is as follows: Through reasonable structural design and component configuration, the marine geomagnetic diurnal variation station of this embodiment solves the problems of electromagnetic interference, pressure resistance protection, and system integration faced by proton precession magnetometers in deep-sea applications. Separating the main unit 4 from the probe unit 2 reduces electromagnetic interference; the pressure-resistant sealed chamber 1 with a glass float structure improves the equipment's pressure resistance; the power system 5 uses multiple lithium iron phosphate batteries to ensure long-term battery life; the positioning and time synchronization module 8 provides accurate time and position references for data; and the environmental monitoring unit monitors the equipment status in real time, improving system reliability. Compared with existing technologies, the marine geomagnetic diurnal variation station of this embodiment has higher stability and endurance, better adapts to the deep-sea environment, and provides more accurate data for marine geomagnetic measurements.

[0038] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A marine geomagnetic diurnal station, characterized in that: The application relates to a pressure-resistant sealed cabin body (1); a proton precession magnetometer system for measuring the intensity of the geomagnetic field, which comprises a main unit (4) located inside the pressure-resistant sealed cabin body (1) and a probe unit (2) located outside the pressure-resistant sealed cabin body (1), a watertight cable structure (3) is arranged between the probe unit (2) and the main unit (4), the distance between the main unit (4) and the probe unit (2) is extended through the watertight cable structure (3) to reduce interference; a power supply system (5) integrated in the pressure-resistant sealed cabin body (1) and providing power for the proton precession magnetometer system; a positioning and time synchronization module (8) for providing position information and time calibration; and an environment monitoring unit for monitoring the internal state of the cabin body. The pressure-resistant sealed cabin body (1) is a glass floating ball structure, and the pressure-resistant sealed cabin body (1) is divided into an upper part and a lower part, the upper part accommodating the main unit (4) and a data acquisition and control unit, and the lower part accommodating the power supply system (5). The power supply system (5) comprises a plurality of lithium iron phosphate batteries, and the total capacity is not less than 2000Wh. The main unit (4) comprises a CPU board and an analog board, the CPU board is configured to control the analog board to give a pulse to the probe unit (2), the probe unit (2) generates a proton precession effect and feeds back an analog signal to the analog board, and the CPU board analyzes the analog signal to obtain a magnetic field value. The positioning and time synchronization module (8) is a GPS or Beidou receiver, supports network time service and crystal oscillator time service, calibrates the collection time when working on land, and relies on the crystal oscillator to maintain timing when working in deep sea. The pressure-resistant sealed cabin body (1) is provided with a communication control interface (12), the deck control unit is connected with the pressure-resistant sealed cabin body (1) through the communication control interface (12), and is used for realizing parameter configuration, data export and equipment switching.

2. A marine geomagnetic diurnal station according to claim 1, characterized in that: The pressure-resistant sealed cabin body (1) is provided with a sensor interface (13) connected with the watertight cable structure (3).

3. A marine geomagnetic diurnal station according to claim 1, characterized in that: The pressure-resistant sealed cabin body (1) is provided with an air exhaust interface (11) connected with a vacuumizing device, the vacuumizing device is used for exhausting the air in the pressure-resistant sealed cabin body (1), and the air exhaust interface (11) is blocked to maintain the vacuum state of the pressure-resistant sealed cabin body (1).

4. A marine geomagnetic diurnal station according to claim 1, characterized in that: The environment monitoring unit comprises a voltmeter and ammeter (6) and a pressure gauge (7), the voltmeter and ammeter (6) is installed on a power supply line between the power supply system (5) and the main unit (4) and is used for monitoring and displaying the current and voltage use and power supply state of the main unit (4) in real time, and the pressure gauge (7) is used for testing the pressure in the pressure-resistant sealed cabin body (1), and an alarm is triggered when the voltmeter and ammeter (6) or the pressure gauge (7) detects an abnormality.

5. A marine geomagnetic diurnal station according to claim 1, characterized in that: ​ 6. A marine geomagnetic diurnal station according to claim 1, characterized in that: ​ 7. A marine geomagnetic diurnal station according to claim 1, characterized in that: ​ 8. A marine geomagnetic diurnal station according to claim 1, characterized in that: ​ 9. An oceanographic geomagnetic diurnal station according to claim 8, characterized in that: ​

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