Muzeul Olteniei Craiova.
Studii şi comunicări. Ştiinţele Naturii. The continuous development of data acquisition and processing techniques in planetary geomagnetic observatories allows at this time to extract as complete information about the morphology and evolution over time of the terrestrial geomagnetic field. In the evolution of the acquisition of geomagnetic data, different physical phenomena were used for the realization of magnetic sensors for both absolute and triaxial variometric measurements.
These magnetic sensors communicate through specialized software programs with acquisition systems and process computers.
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This whole chain together with the underground labs where the sensors are located make up the infrastructure of a geomagnetic observer. The paper describes the physical phenomena underlying the geomagnetic field metrology, the equipment used and the software programs for communication and data transmission. The main research objectives are also presented, along with the applicative importance of measurements in the geomagnetic observatories.
Considerații privind infrastructura, dispozitivele și principiile fizice în metrologia câmpului geomagnetic. Dezvoltarea continuă a tehnicilor de achiziţie si procesare a datelor în observatoarele geomagnetice planetare permite în acest moment extragerea unor informaţii cât mai complete despre morfologia şi evoluţia în timp a câmpului geomagnetic terestru.
În evoluția achizițiilor datelor geomagnetice au fost folosite diferite fenomene fizice pentru realizarea de senzori magnetici atât pentru măsurătorile absolute cât și pentru măsurătorile variometrice triaxiale. Acești senzori magnetici comunică prin programe software specializate cu sistemele de achiziție și calculatoarele de proces. Tot acest lanț împreună cu laboratoarele subterane în care sunt amplasați senzorii alcștuiesc infrastructura unui observator geomagnetic. În lucrare sunt descrise fenomenele fizice care stau la baza metrologiei câmpului geomagnetic, aparatura folosită și programele software de comunicare și de transmitere a datelor.
Am făcut o detaliere a aparaturii și infrastructurii de la Observatorul Geomagnetic Național Șurlari situat într-o zonă fără anomalii magnetice, la cca. Sunt prezentate și principalele obiective de cercetare precum și importanța aplicativă a măsurătorilor din observatoarele geomagnetice. These distributions are obtained by repeated measurements in a network of points evenly distributed across the country.
Important applications are related to the appropriate dimensioning of the energy networks, in communications, aviation transport and oil pipeline transport due to additional induced currents.
A schematic diagram of the contribution of physical processes to the geomagnetic field is presented in Fig. Figure 1. A schematic representation of the frequency spectrum of the geomagnetic field is shown in Fig. Figure 2.
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The first phenomenon uses the tracking of the position of equilibrium of a permanent magnet under the exclusive action of the geomagnetic field or the action of a torque generated by it and determining the period of oscillation for quantitative assessment of the direction and intensity of the geomagnetic field. The action of the geomagnetic field on a magnet leads to a determined orientation, which coincides with the geomagnetic field orientation only when the magnet is not subject to any foreign constraints.
The magnetization of materials with high susceptibility, i. The directional distribution of the magnetic induction represents the cumulative effects through the relative parts of the magnetic sensor by materials, magnetization and amplification of each of these effects.
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The phenomenon of electromagnetic induction has contributed to the metrological technique. Rotating coils have been used since the first half of the nineteenth century for measuring the intensity of the geomagnetic components, or to track their space orientation.
The axis of rotation of the coil must be orthogonal on the field direction and measure the induced current in these conditions, which means the parallelism between the rotation axis and field direction.
Characteristic for the traditional geomagnetic measurements, based on the use of the phenomena mentioned, is the fact that they lead to the knowledge of the geomagnetic field through angles that define its direction and the intensity of its components after certain directions.
These parameters vary depending on the location of the observation point on Earth. Reported to a local reference system, defined by the horizontal and the north direction, i. The first way of defining was the first used and is in use today for absolute determinations.
The geomagnetic elements measured in this way are: 1 magnetic declination D, represented by the angle between projection on the horizontal of the field and the north direction, 2 magnetic inclination I, i. The second way is used in particular for the geomagnetic observatory records, where the following are tracked: declination changes ΔD, variations of the horizontal and vertical component, ΔH and ΔZ.
Determining the field by the third method north component Xeast component Y and vertical component downward Z is performed by means of a device, based on magnetic induction, with the magnetized bars oriented properly.
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Two phenomena able to highlight the existence of the geomagnetic field, and to serve, ensuring the required accuracy, for quantitative assessment, began to be taken into account for geomagnetic metrology purposes around Later on they were effectively introduced and used on a larger scale in the measurements: nuclear precession and optical pumping.
Intra-atomic processes occur in both phenomena, governed by the laws of quantum mechanics. They were used for indirect measurement of the geomagnetic field intensity, led to the construction of devices and the development of methods of modern geomagnetic metrology, designated through the term of quantum magnetometry. The case of nuclear precession, by applying an intense auxiliary magnetic field, with about two orders of van ifor williams ocazie swiss anti aging stronger than that of the Earthand with a transversal direction thereon on it, nuclei possessing a magnetic moment of some atoms — hydrogen is currently used in geomagnetic metrology, whose nucleus is an even proton, resulting in the term of proton precession or resonancecommonly used in this area — are oriented with their magnetic axes by this direction required by the auxiliary field polarizing field.
When this field is suppressed, small magnets represented by nuclei with magnetic moment for hydrogen: protons remain under the exclusive influence of the geomagnetic field, whose orientation tends to return from the polarization magnetic field direction to that of the geomagnetic field.
This takes place through a precession motion, whose frequency is proportional to its intensity. Thus, the knowledge of frequency of precession and the proportionality constant will be determining the total geomagnetic field intensity. Optical pumping is an excitation process of atoms or ions in an environment through irradiation with electromagnetic radiation.
Radiation and intensity spectrum, passing from higher energy levels on lower level, result in a population inversion between two energy levels. Van ifor williams ocazie swiss anti aging redistribution of electrons between two levels can be achieved by excitation with radiation of lower frequency corresponding to the energy difference between them.
In both these determinations, through proton precession or optical pumping, frequency is directly measured - a measure that requires complicated electronic devices but can be made with great precision - and resulting in a total geomagnetic field value. This system is composed of a counterbalanced clockwork mechanism and 3 wire- twisting magnetometers. The magnetometers consist cea mai bună cremă anti-îmbătrânire pentru noapte permanent magnets attached to non-magnetic material provided with mirror and snap at the end of the quartz wire for sensors D and H.
The Z component sensor consists of a permanent magnet located on two quartz slides which allow vertical movement. The whole mechanism is enclosed in a box so as not to be disturbed by possible air currents produced in the room.
The first daily magnetogram recorded in this format is shown in Fig. Maximum recording limit of the analog system The field in Vertical direction The field in North direction The field in East direction Parameters related to functionality of the analog recording system on thermosensitive paper.
First magnetogram recorded at Surlari Geomagnetic Observatory. Registered physical parameters are explained in the column on the right side of the figure. In addition to this system, an analog recording system consists of 3 Bobrov variometers and a clockwork mechanism Matting Weissenberg were brought to our observatory in Unlike Askania variometers, the Bobrov variometers have better stability in time, a reduced sensitivity to temperature changes and are less sensitive to shocks.
In a fourth variometer is attached to this system,whose magnet is oriented in the total magnetic field vector plane.
This is done by means of DC powered coils placed in the directions perpendicular to the axis sensors. The DC power has a known intensity. The two systems have operated continuously untilproducing analogue records on photographic paper.
It is also very important to obtain a base level of records with absolute measurements made with theodolite Matting Weissenberg, ground inductor and oscillations box in a first phase and then theodolite Matting Weissenberg and quartz horizontal magnetometer for the H component QHM. In addition to these device, a Varian proton precession magnetometer was brought inmeasuring the scalar value of the total field. The sensors of this magnetometer are magnetic inductive type and are made of coils with a large number of turns and a magnetic core with high permeability Permalloy.
The characteristic response floor type of this magnetic sensor shows a very good functionality for a band of frequencies between 1Hz and Hz. The MAG 03 DAM logger has two connectors for analog input signal from two flux gate magnetometers and a RS connector with 25 pins for output signal.
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The logger is controlled recenzii juvacell soluție anti-îmbătrânire software developed in FORTRAN that allows selecting the number of channels to be recorded fromthe choice of sampling rate between one second and 10 seconds and the measuring range. The sampling rate refers to the frequency of purchase and not the storage, it is 10 times lower. These measurements are used to establish the base level of permanent records.
Measurements with DI Fluxgate are run at regular intervals, especially during periods of magnetic calm, and are national magnetic standards for the geomagnetic mapping work of the national territory. With their help, the magnetometers of other research or industrial companies are calibrated. This type of magnetometer can be used mounted on a Wild T1 theodolite nonmagnetic. It can measure both declination and inclination of the geomagnetic field with an accuracy of ± one second sexagesimal degree.
Typically, this device works with the zero method when the magnetic sensor is positioned perfectly horizontal and the declination of the magnetic field can be determined.
When placed in a perpendicular plane to the horizontal component of geomagnetic field, the inclination of the magnetic field can be determined.
Also, when the sensor is placed in a vertical plane, perpendicular to the horizontal geomagnetic field, the total field gradient gel de curatare fata garnier be determined. Geometrics G proton precession magnetometers are used for absolute measurements of total magnetic field.
They have a very good thermal stability and resolution consistent with the standards of IAGA. Data can be stored in the internal memory of electronic units or by connecting it to a computer. G can be used in differential version using two sensors, mounted on a particular tripod to obtain geomagnetic field variation with distance. The variation with temperature of recorded values due sensors is below 0. For a good stability of the baseline, a suspended version of the cube of marble was adopted in most of geomagnetic observatories.
In this way the baseline drift is less than 3. The alignment error of the three vector components is maximum 2mrad 7 min of arc. GSM90 Overhauser proton magnetometer is a scalar magnetometer designed for magnetic observatories and other applications Volcanologywhere stability and accuracy are van ifor williams ocazie swiss anti aging necessary. With a resolution of 0. The torsion photoelectric magnetometer PSM The magnetometer is composed of a set of 3 torsion variometers.
The variometers are connected to an electronic system based on the principle of compensation feedback. The compensation current is proportional to the intensity of the geomagnetic field to be compensated by current injected in coils located van ifor williams ocazie swiss anti aging the variometer. The resolution of these variometers is 0. The technical specifications of the logger are masca pentru ridurile de pe frunte above.
By using different calibration methods, further exemplified, we obtained the transfer functions for the recorded values with each magnetometer.
For each device we make a calibration and we calculate transfer functions. Figure 5. Figure 6. The differences between the two curves obtained after calibration are very small maximum 0.
The curve in blue colour is only visible in some points, while only the red curve can be seen otherwise. This effect occurs because the red curve is in the front plane and the blue curve is in the back plane. The geomagnetic field variation study provides information on the Earth's internal conductivity, their knowledge being also useful in magnetic prospecting works whose results need to be processed to extract the effects of diurnal variations, the value of the normal field at the date and location of the prospecting, and of secular variation when using panels measured in different epochs.
An important application of observer data is the determination of the magnetic declination the angle between the geographic and magnetic north used for the correction of navigational instruments on board aircraft during landing and take-off maneuvers, for GPS guidance systems used in civil aviation, and military, satellite trajectories, missiles and missiles, etc.
This parameter can be estimated with good accuracy for magnetically calm days. For agitated days, and even more so during magnetic storms, the variation of the declination parameter becomes significant.
A geomagnetic storm is known to have different characteristics amplitudes, gradient, geomagnetic coefficients depending on the latitude at which it is measured. Thus, at the beginning of a geomagnetic storm, the data from the closest to ground geomagnetic observation points is needed on-line for the corrections of the guidance systems. Another important application is related to the appropriate dimensioning of energy networks van ifor williams ocazie swiss anti aging, transport cables, etc.