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[en] Complete text of publication follows. Since the beginning of this decade fast DIDD magnetometers have been also applied to record the geomagnetic variation as an 'INTERMAGNET standard' instrument. The principle of this instrument makes it clear, that the values recorded by DIDD are void from offset and scalar factor errors. For the description of the reference frame only four parameters are needed: The angle between the two magnetic axes of the coil system (εID) and the three orientation angles (I0, D0 and ε0). Two methods were developed in the past to find and monitor the coordinate system of the DIDD by using independent geomagnetic measurements. The first method uses absolute measurements to calibrate the DIDD (Schott and Pankratz 2001) while the other is the inter-calibration process developed in Tihany Geophysical Observatory (Heilig 2007). The second method is based on simultaneous recordings of a DIDD and a tri-axial fluxgate magnetometer. A simple new procedure is applied in order to measure εID value directly from DIDD recordings themselves. The sensitivity of this calculation is at the order of arc seconds at the geomagnetic latitude of Tihany Geophysical Observatory. The advantage of this method is double. First, we will be able to adjust the orthogonality accurately, and on the other hand we can monitor the value of this angle periodically. The cognition of this angle is an important station in the development of DIDD instrument, because it gives the possibility for self-calibration of the orthogonality. After the orthoganality error is eliminated only the three orientation angles including the levelling of the D axis (ε0) left to be determined. This can be done using absolute measurements. The poster will describe the new methods and present the first test results to demonstrate the accuracy and the limitation of the new observatory practices.
[en] Complete text of publication follows. Five sets of variometers are continuously operated at the NCK observatory for different purposes. Three sets of fluxgate, one set of torsion magnetometer and one semi-absolute vector magnetometer had been tested for scale value, sensor orientation, temperature effects and long term stability by using natural variations. Differences between measured and calculated total field, as well as baseline variations were considered and different transfer functions among components were analyzed to achieve higher accuracy.
[en] Complete text of publication follows. There are three Geomagnetic Observatories (GOs) in territory of Ukraine: GO 'Lviv', GO 'Kiev' and GO 'Odesa'. GO 'Lviv' starts to operate in 1932. Unfortunately all materials of the observation till 1941 were lose. Observations were renew at 1952. Two series of the magnetometers were put into operation: main series - H, D, Z La Cour and duplicate series - H, D, Z Eshengagen. Absolute measurement carry out by magnetic theodolite COOK, induction inclinometer and quartz magnetometer. In 1966 proton magnetometer PM - 1 was installed. In 1970 geomagnetic variation stations were changed. Two series of Bobrov variation stations were installed. Now at the observatory operate two digital variation stations PSM - 8811 constructed by Polish Institute of Geophysics. Absolute measurements fulfill by DI fluxgate magnetometer with FLM1/B electronics. Observatory sent observation data to WDC - B2 in Moscow and is member of the INTERMAGNET. GO 'Kiev' was located in Demidov with 1958 and now is in Dymer with 1964 (distance between these points about 10 km). Regular variation and absolute measurements was begun in 1958 by the standard equipment (La Cour, Bobrov, QHM, BMZ, PM-1). Now at the observatory operate two digital variometers LEMI-008 with GPS reference and internal memory (from 2004) and one digital variation stations PSM - 8811 (from 2009, March), DI fluxgate magnetometer LEMI -203 (Lviv Centre of Institute of Space Research) and proton variation station MV-01 (Geologorazvedka, St.Peterburg). GO 'Kiev' works in the test mode INTERMAGNET from 2005. The regular measurements of the Earth's magnetic field at the GO 'Odesa' are carried out by the standard equipment from a 1948 year for a present tense. GO 'Odessa' needs modernization. Software MATLAB is used for the analysis and data processing of the Ukrainian GOs. The supervisions in Ukrainian GOs use for the decision different geomagnetic, geological and ecological tasks.
[en] Complete text of publication follows. On December 16th, 2008 an earthquake of magnitude 4.2 MW occurred in Southern Sweden - a rare occurrence in this geographical region. The tremor of the ground was large enough that magnetometers at the Brorfelde observatory about 140 km away from the epicentre registered the event. Even at DMI's variometer station on R?m? at a distance of 340 km, the earthquake influenced the magnetic measurements. The earthquake is clearly visible in the 1 Hz data from both the observatory and the variometer station, whereas nothing is seen in the minute means, which is generated as average values of the second data. The earthquake has given us an opportunity to investigate how the DMI FGE pendulum fluxgate magnetometer reacts to high-frequent vibrations of the base. At the Brorfelde observatory where two identical magnetometers are placed next to each other we see very different amplitudes of the signal: the amplitude of the earthquake signal on the east component of the primary instrument is about twice the amplitude of the same component on the secondary instrument for most of the earthquake signal. Looking for additional examples of magnetometer registrations of earthquakes we discovered amongst others signals from an earthquake in the Disko bay on March 30th, 2005 on data from the Godhavn (Qeqertarsuaq) Observatory in Greenland.
[en] Complete text of publication follows. The U. S. Geological Survey Geomagnetism Program is now collecting one-second triaxial fluxgate magnetometer data at its observatories. Extensive testing is being done to validate the data and document its resolution and timing accuracy. Magnetometer resolution is evaluated by examining the second-to-second differences of each individual component to estimate the noise level. The noise level is determined for the data acquisition system itself and then at each observatory site. Timing accuracy is tested by using the one pulse per second (PPS) output from a GPS clock to trigger a pulse generator with delay. Through this test we are able to quantify the delay introduced by each component of our data acquisition system, including the fluxgate magnetometer and A/D converter. As a second test of timing accuracy, a sine wave is used to examine the delay in the analog output from the fluxgate. The results of these tests are compared with the standards of 0.01 nT resolution and 10 millisecond time accuracy as proposed by Intermagnet in 2008.
[en] Complete text of publication follows. The South Atlantic Magnetic Anomaly (SAMA) region is extensive over a very large South America area, where is observed the smallest intensity of the Earth's Geomagnetic Field on the Global surface. To monitor and study the geomagnetic phenomena in the SAMA's region with a magnetometer network in a reliable and autonomy way, it has been developed concepts to construct low cost three axis fluxgate magnetometers with programmable logic controller. The concepts are been developed at the Southern Regional Space Research Center - CRS/INPE-MCT in collaboration with the Federal University of Santa Maria - UFSM, Santa Maria, RS, in South of Brazil, through a undergraduate Capacity Building Integrated Program (CBIP). The operation of fluxgate magnetometer is based on the magnetic properties of the high permeability core sensor. Varying the sensor core magnetic permeability through superposing a high frequency excitation signal, it is possible to obtain a change in the core hysteresis loop (BxH). The sensor pickup coil detects the external field magnetic density variation, in this case the Earth's Geomagnetic Field. Therefore, it is possible to determinate the external field intensity. The use of programmable logic controllers may reduce the size of usual analog circuits used in magnetometers manufacturing. It also may reduce the power consumption and provides a direct connection to a data record system without the necessity of a PC and an external AD converter to save the detected geomagnetic data. This paper has the intention to show, as a result of the INPE-UFSM's CBIP, the development of a low cost magnetometer circuit, sensor concepts and its implementation. It also aims to present the preliminary results and conclusions of the Earth's Geomagnetic Field data acquisition at the Southern Space Observatory - SSO/CRS/INPE-MCT, (29.4degS, 53.8degW, 480 m a.s.l.), in the SAMA's region, South of Brazil.
[en] The state-of-art and general features of instruments for measuring weak magnetic fields (such as the non-directional magnetometer, induced coil magnetometer, proton magnetometer, optical pumping magnetometer, flux-gate magnetometer and superconducting quantum magnetometer) are briefly described. Emphasis is laid on the development of a novel technique used in the flux-gate magnetometer and the liquid nitrogen SQUID. Typical applications of the measuring techniques for weak magnetic fields are given
[en] Complete text of publication follows. Recently, a Geomagnetic Observatory in Cheongyang (GOC) has been established by the Korea Meteorological Administration(KMA) to measure geomagnetic field precisely and to study the possibility of forecasting of earthquake activity. The GOC consisted of 4 huts is located in a mountainous area and about 5 km away from the main traffic road, which will reduce the artificial magnetic noise. The total magnetic field strength on the site including the magnetic field by rocks and soils was measured by using a mobile gradient Cs optical pumping magnetometer(G-858, Geometrics) equipped with a GPS receiver to find an ideal site for the GOC. The vertical gradient of the geomagnetic field around the 3-axial fluxgate sensor hut and the Overhauser sensor hut for the GOC was measured. In addition, the magnetic properties of all the materials used for the GOC such as sands, marble, gravels and brass were controlled to avoid the improper use of ferromagnetic components. The equipments of the GOC are a 3-axis fluxgate magnetometer (DMI), an Overhauser effect proton magnetometer (GEM), and a data logger (MinGeo). A D/I magnetometer is prepared for the absolute measurement. The Cs-He optical pumping magnetometer was used to correct the measured data by the proton magnetometer for absolute measurement of the geomagnetic field more accurately . Furthermore, the magnetic standard system was used for calibration of all the measurement equipment used . The test measurement results indicate that the measurement conditions meet the INTERMAG requirements. Therefore, we will participate in the INTERMAG and share our geomagnetic field data with the other national geomagnetic observatories.