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Journal articles on the topic 'IGRF [International Geomagnetic Reference Field]'

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Published: 4 June 2021

Last updated: 7 February 2022

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1

Barraclough, D. R. "International Geomagnetic Reference Field Revision 1987." GEOPHYSICS 53, no. 4 (April 1988): 576–78. http://dx.doi.org/10.1190/1.1442493.

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The International Geomagnetic Reference Field (IGRF) is a series of mathematical models of the main geomagnetic field and its secular variation, the models consisting of sets of spherical harmonic (or Gauss) coefficients. The IGRF has become a widely used means of deriving values of geomagnetic field components in, for example, studies of magnetic anomalies and investigations of charged particle motions in the ionosphere and the magnetosphere.

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2

Peddie, Norman W. "International Geomagnetic Reference Field Revision 1985." GEOPHYSICS 51, no. 4 (April 1986): 1020–23. http://dx.doi.org/10.1190/1.1442144.

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IAGA Division I, Working Group 1 deals with the topic “Analysis of the Main Field and Secular Variations.” One of the more important functions of the working group is the periodic revision of the International Geomagnetic Reference Field (IGRF). The thirteen members of the working group have professional interests covering a broad spectrum of geomagnetic science, including the theory and practice of geomagnetic analysis and modeling, the theory of the origin of the magnetic fields of the Earth and other bodies, the theory of geomagnetic secular variation, the application of field models in magnetic survey data processing, and geomagnetic charting.

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3

De Santis, A., and E. Qamili. "Shannon information of the geomagnetic field for the past 7000 years." Nonlinear Processes in Geophysics 17, no. 1 (February 12, 2010): 77–84. http://dx.doi.org/10.5194/npg-17-77-2010.

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Abstract. The present behaviour of the geomagnetic field as expressed by the International Geomagnetic Reference Field (IGRF) deserves special attention when compared with that shown over the past few thousands of years by two paleomagnetic/archeomagnetic models, CALS3K and CALS7K. The application of the Information theory in terms of Shannon Information and K-entropy to these models shows characteristics of an instable geomagnetic field. Although the result is mitigated when we correct the CALS7K model for its typical spectral damping, the present geomagnetic field as represented by IGRF is still rather distinct, at least for the past 4000 years, a result that is further confirmed by the CALS3K model. This is consistent with a significant global critical state started at around 1750, and still present, characterised by significant decays of the geomagnetic dipole, energy and Shannon information and high K-entropy. The details of how these characteristics may develop are not clear, since the present state could move toward an excursion or a geomagnetic polarity reversal, but we cannot exclude the possibility that the "critical" behaviour will become again more "normal", stopping the apparent trend of the recent geomagnetic field decay.

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4

Langel, R. A. "International Geomagnetic Reference Field, 1991 Revision: International Association of Geomagnetism and Aeronomy (IAGA) Division V, Working Group 8: Analysis of the main field and secular variation." GEOPHYSICS 57, no. 7 (July 1992): 956. http://dx.doi.org/10.1190/1.1443310.

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The International Geomagnetic Reference Field (IGRF) is a series of mathematical models of the main geomagnetic field and its secular variation. Each model consists of a set of spherical harmonic (or Gauss) coefficients, g and h in a series expansion of the geomagnetic potential [Formula: see text], where a is the mean radius of the Earth (6371.2 km); r the radial distance from the center of the Earth; ϕ the east longitude measured from Greenwich; θ the geocentric colatitude; and [Formula: see text] the associated Legendre function of degree n and order m, normalized according to the convention of Schmidt [see, e.g., Langel (1987)]. In principle, N should be ∞ but the Working Group is of the opinion that in practice the available data for most epochs do not justify N greater than 10. This value is chosen to maintain consistency between models at different epochs. The coefficients are in units of nanotesla (nT).

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5

BARRACLOUGH, David R., Larry D. WILLIAMS, and John M. QUINN. "US/UK Candidates for the Definitive Geomagnetic Reference Field Model DGRF-85 and the Predictive International Geomagnetic Reference Field Model IGRF-90." Journal of geomagnetism and geoelectricity 44, no. 9 (1992): 719–34. http://dx.doi.org/10.5636/jgg.44.719.

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6

Gaya-Piqué, Luis R., Dhananjay Ravat, Angelo De Santis, and J. Miquel Torta. "New model alternatives for improving the representation of the core magnetic field of Antarctica." Antarctic Science 18, no. 1 (March 2006): 101–9. http://dx.doi.org/10.1017/s0954102006000095.

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Use of the International Geomagnetic Reference Field Model (IGRF) to construct magnetic anomaly maps can lead to problems with the accurate determination of magnetic anomalies that are readily apparent at the edges of local or regional magnetic surveys carried out at different epochs. The situation is severe in areas like Antarctica, where ionospheric activity is intense and only a few ground magnetic observatories exist. This makes it difficult to properly separate from ionospheric variations the secular variation of the core magnetic field. We examine two alternatives to the piecewise-continuous IGRF core magnetic field in Antarctica for the last 45 years: the present global Comprehensive Model (CM4) and the new version of the Antarctic Reference Model (ARM). Both these continuous models are better at representing the secular variation in Antarctica than the IGRF. Therefore, their use is recommended for defining the crustal magnetic field of Antarctica (e.g. the next generation of the Antarctic Digital Magnetic Anomaly Map).

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7

Walker, A. D. M. "Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 2: The IGRF." Annales Geophysicae 34, no. 1 (January 19, 2016): 67–73. http://dx.doi.org/10.5194/angeo-34-67-2016.

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Abstract. A method of mapping electric fields along geomagnetic field lines is applied to the IGRF (International Geomagnetic Reference Field) model. The method involves integrating additional sets of first order differential equations simultaneously with those for tracing a magnetic field line. These provide a measure of the rate of change of the separation of two magnetic field lines separated by an infinitesimal amount. From the results of the integration Faraday's law is used to compute the electric field as a function of position along the field line. Examples of computations from a software package developed to implement the method are presented. This is expected to be of use in conjugate studies of magnetospheric phenomena such as SuperDARN (Super Dual Auroral Radar) observations of convection in conjugate hemispheres, or comparison of satellite electric field observations with fields measured in the ionosphere.

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8

Hérnandez Quintero, E., H. Nolasco Chávez, J. O. Campos Enríquez, C. Cañon Amaro, A. Orozco Torres, J. Urrutia Fucugauchi, and G. Alvarez García. "Evaluación preliminar del campo geomagnético de referencia internacional IGRF-1990 para México y anomalías magnéticas corticales." Geofísica Internacional 33, no. 2 (April 1, 1994): 235–41. http://dx.doi.org/10.22201/igeof.00167169p.1994.33.2.472.

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Se reporta una comparación regional entre el International Geomagnetic Reference Field (IGRF) para 1990 y medidas geomagnéticas de campo obtenidas en 51 localidades del país. El modelo de IGRF provee un campo de referencia regional satisfactorio para México. Las diferencias medias entre el modelo del IGRF y las observaciones de campo parecen definir anomalías regionales. Las diferencias medias del campo total son de 10.6 nT, con una raíz media cuadrática (RMS) de 206 nT. Las diferencias medias correspondientes a la componente horizontal y a la declinación son de 24.4 nT y -0.6‘ con desviaciones RMS de 116 nT y 18.7‘ respectivamente. Algunos rasgos de longitud de onda grande en las diferencias de campo total se correlacionan con anomalías aeromagnéticas y observaciones magnéticas de satélite, lo cual sugiere una posible asociación con fuentes en la corteza.

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9

Han, Xiao, Xiao Jun Yang, and Naqvi Najam Abbas. "Design and Simulation of Attitude Determination and Control Subsystem of CubeSat Using Extended Kalman Filtering and Linear Quadratic Gain Controller." Advanced Materials Research 694-697 (May 2013): 1582–86. http://dx.doi.org/10.4028/www.scientific.net/amr.694-697.1582.

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This paper describes an integral scheme of the design and simulation of the Attitude Determination and Control Subsystem (ADCS) of CubeSat. CubeSat is an educational low-cost, cube-shaped Pico spacecraft. Attitude Determination (AD) is the problem of expressing the orientation of a spacecraft with respect to a given coordinate system. Three axis magneto-resistive digital magnetometer is selected as an attitude sensor. The International Geomagnetic Reference Field (IGRF) is used as reference for magnetometer to obtain attitude information. An enhanced orbit estimate/propagator is implemented to provide position information to IGRF model. Satellite environmental torque is modeled along with satellite kinematics and dynamics. Attitude estimation is done using Extended Kalman Filter (EKF) while the magnetic coils are used as actuators. Attitude Control is applied using Linear Quadratic Regulation (LQR) Controller. The designed ADCS is implemented in Matlab/Simulink.

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Němec, František, and Marie Kotková. "Evaluating the Accuracy of Magnetospheric Magnetic Field Models Using Cluster Spacecraft Magnetic Field Measurements." Universe 7, no. 8 (August 3, 2021): 282. http://dx.doi.org/10.3390/universe7080282.

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Magnetic fields in the inner magnetosphere can be obtained as vector sums of the Earth’s own internal magnetic field and magnetic fields stemming from currents flowing in the space plasma. While the Earth’s internal magnetic field is accurately described by the International Geomagnetic Reference Field (IGRF) model, the characterization of the external magnetic fields is significantly more complicated, as they are highly variable and dependent on the actual level of the geomagnetic activity. Tsyganenko family magnetic field models (T89, T96, T01, TA15B, TA15N), parameterized by the geomagnetic activity level and solar wind parameters, are often used by the involved community to describe these fields. In the present paper, we use a large dataset (2001–2018) of magnetospheric magnetic field measurements obtained by the four Cluster spacecraft to assess the accuracy of these models. We show that, while the newer models (T01, TA15B, TA15N) perform significantly better than the old ones (T89, T96), there remain some systematic deviations, in particular at larger latitudes. Moreover, we compare the locations of the min-B equator determined using the four-point Cluster spacecraft measurements with the locations determined using the magnetic field models. We demonstrate that, despite the newer models being comparatively slightly more accurate, an uncertainty of about one degree in the latitude of the min-B equator remains.

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11

Ariani, Novi Dwi, Thaqibul Fikri Niyartama, and Nugroho Budi Wibowo. "PEMETAAN SEBARAN BATUAN PENYUSUN PAGAR CANDI DI SITUS CANDI LOSARI DUSUN LOSARI, DESA SALAM, KECAMATAN SALAM, KABUPATEN MAGELANG BERDASARKAN METODE MAGNETIK." Berkala Arkeologi 33, no. 1 (May 31, 2013): 121–31. http://dx.doi.org/10.30883/jba.v33i1.10.

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Mapping geophysics research was conducted by geomagnetic method to know anomaly pattern of magnetic pole and to know distribution location and depth of temple gate composing stone in Losari Temple Site by using magnetic data. Data collection used Proton Precessions Magnetometer (PPM) G-856AX by area width of 88 km x 40 km and measurement space of 3 meter used looping method. Field data was corrected by daily variation and IGRF (International Geomagnetics Reference Field) correction and then reduction to pole. The slice modeling was conducted on local anomaly map on height of 6 meter. The result of the local magnetic field anomalies incision then interpolated to get an idea of the spread and depth of rocks making up the fence Losari temple. Local anomaly map shows that anomaly position lies in southwest, southeast, and northeast from main temple. Based from interpolated distribution of magnetic pole anomaly is dominated in depth of 2 meter to 4 meter.

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Weygand, J. M., and J. Raeder. "Cosmic ray cutoff prediction using magnetic field from global magnetosphere MHD simulations." Annales Geophysicae 23, no. 4 (June 3, 2005): 1441–53. http://dx.doi.org/10.5194/angeo-23-1441-2005.

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Abstract. Relativistic particles entering the Earth's magnetosphere, i.e. cosmic rays and solar energetic particles, are of prime space weather interest because they can affect satellite operations, communications, and the safety of astronauts and airline crews and passengers. In order to mitigate the hazards that originate from such particles one needs to predict the cutoff latitudes of such particles as a function of their energies and the state of the magnetosphere. We present results from a new particle tracing code that is used to determine the cutoff latitudes of 8-15Men-1 alpha particles during the 23/24 April, 1998 geomagnetic storm and the preceding quiet time. The calculations are based on four different geomagnetic field models and compared with SAMPEX observations of alpha particles in the same energy range. The geomagnetic field models under consideration are: (i) the International Geomagnetic Reference Field (IGRF) model, (ii) the Tsyganenko "89" model (T89c), (iii) the Tsyganenko "96" model (T96), and (iv) a global magnetohydrodynamic (MHD) model of Earth's magnetosphere. Examining 11 SAMPEX cutoff latitude observations we find that the differences between the observed and the predicted cutoff latitudes are 2.3° ± 2.0° (mean) and 7.9° (maximum difference) for the IGRF model; 3.9° ± 2.4° (mean) and 6.9° (maximum difference) for the T89c model; 4.0° ± 1.4° (mean) and 5.5° (maximum difference) for the T96 model; and 2.5° ± 1.7° (mean) and 7.0° (maximum difference) for the MHD model. All models generally predict cutoff latitudes equatorward of the SAMPEX observations. The MHD model results also show steeper cutoff energy gradients with latitude compared to the empirical models and more structure in the cutoff energy versus latitude function, presumably due to the presence of boundary layers in the MHD model.

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Xia, Linlin, Jingtong Geng, Hanrui Yang, Yunqi Wang, Zhaolong Fu, and Bo Meng. "An Optimized Two-Step Magnetic Correction Strategy by Means of a Lagrange Multiplier Estimator with an Ellipsoid Constraint." Sensors 18, no. 10 (September 29, 2018): 3284. http://dx.doi.org/10.3390/s18103284.

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The geomagnetic field is as fundamental a constituent of passive navigation as Earth’s gravity. In cases where no other external attitude reference is available, for the direct heading angle estimation by a typical magnetic compass, a two-step optimized correction algorithm is proposed to correct the model coefficients caused by hard and soft iron nearby. Specifically, in Step 1, a Levenberg-Marquardt (L-M) fitting estimator with an ellipsoid constraint is applied to solve the hard magnetic coefficients. In Step 2, a Lagrange multiplier estimator is used to deal with the soft magnetic iron circumstance. The essential attribute of “the two-step” lies in its eliminating the coupling effects of hard and soft magnetic fields, and their mutual interferences on the pure geomagnetic field. Under the conditions of non-deterministic magnetic interference sources with noise, the numerical simulation by referring to International Geomagnetic Reference Field (IGRF), and the laboratory tests based upon the turntable experiments with Honeywell HMR3000 compass (Honeywell, Morristown, NJ, USA) conducted, the experimental results indicate that, in the presence of the variation of multi-magnetic interferences, the RMSE (Root Mean Square Error) value of the estimated total magnetic flux density by the proposed two-step estimator falls to 0.125 μT from its initial 2.503 μT, and the mean values of the heading angle error estimates are less than 1°. The proposed solution therefore, exhibits ideal convergent properties, fairly meeting the accuracy requirements of non-tactical level navigation applications.

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14

Hernández-Quintero, Esteban, Gerardo Cifuentes-Nava, Enrique Cabral-Cano, Jaime Urrutia-Fucugauchi, Réne Chávez, Francisco Correa-Mora, Ricardo Becerril, and Juan José Ramírez. "A new permanent geomagnetic station at Colima volcano observatory, Mexico." Geofísica Internacional 39, no. 3 (July 1, 2000): 267–75. http://dx.doi.org/10.22201/igeof.00167169p.2000.39.3.330.

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El Instituto de Geofísica de la Universidad Nacional Autónoma de México (UNAM) y el Observatorio Volcanológico deColima de la Universidad de Colima han instrumentado la primera estación geomagnética (COV) cerca del Volcán de Colima.Esta estación mide el campo magnético escalar y pertenece a una red de monitoreo de volcanes activos en México, cuyopropósito principal es detectar anomalías volcanomagnéticas potenciales asociadas con la actividad volcánica.Se presenta la comparación entre COV y el IGRF ( International Geomagnetic Reference Field), así como con TEO(observatorio Magnético de Teoloyucan) y que presenta un coeficiente de correlación alto (R=0.994), permitiendo obtener unlugar de comparación entre observaciones geomagnéticas de alta precisión en la parte occidental de México. Un sitio en la redpuede utilizarse para consultar la información en tiempo real para la estación (http://www.igeofcu.unam.mx/geomagne/geomag.html).

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Archer, M. O., T. S. Horbury, P. Brown, J. P. Eastwood, T. M. Oddy, B. J. Whiteside, and J. G. Sample. "The MAGIC of CINEMA: first in-flight science results from a miniaturised anisotropic magnetoresistive magnetometer." Annales Geophysicae 33, no. 6 (June 12, 2015): 725–35. http://dx.doi.org/10.5194/angeo-33-725-2015.

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Abstract. We present the first in-flight results from a novel miniaturised anisotropic magnetoresistive space magnetometer, MAGIC (MAGnetometer from Imperial College), aboard the first CINEMA (CubeSat for Ions, Neutrals, Electrons and MAgnetic fields) spacecraft in low Earth orbit. An attitude-independent calibration technique is detailed using the International Geomagnetic Reference Field (IGRF), which is temperature dependent in the case of the outboard sensor. We show that the sensors accurately measure the expected absolute field to within 2% in attitude mode and 1% in science mode. Using a simple method we are able to estimate the spacecraft's attitude using the magnetometer only, thus characterising CINEMA's spin, precession and nutation. Finally, we show that the outboard sensor is capable of detecting transient physical signals with amplitudes of ~ 20–60 nT. These include field-aligned currents at the auroral oval, qualitatively similar to previous observations, which agree in location with measurements from the DMSP (Defense Meteorological Satellite Program) and POES (Polar-orbiting Operational Environmental Satellites) spacecraft. Thus, we demonstrate and discuss the potential science capabilities of the MAGIC instrument onboard a CubeSat platform.

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Rohyati, Eny, Catur Purwanto, Yudha Arman, and Apriansyah Apriansyah. "Interprestasi Data Anomali Medan Magnetik Total Transformasi Reduksi ke Kutub di Laut Flores." PRISMA FISIKA 7, no. 3 (January 2, 2020): 158. http://dx.doi.org/10.26418/pf.v7i3.36112.

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Penelitian dengan menggunakan metode magnetik di laut Flores telah dilakukan. Data medan magnet total diukur menggunakan Proton Precision Magnetometer (PPM) dan kapal Geomarin III dengan jumlah lintasan yaitu sebanyak 20 lintasan. Data anomali medan magnetik total selanjutnya dilakukan koreksi diurnal dan koreksi IGRF (International Geomagnetic Reference Field) untuk menghasilkan data intensitas anomali medan magnetik total. Data anomali magnetik total selanjutnya ditransformasi reduksi ke kutub. Pola kontur intensitas anomali medan magnetik total hasil reduksi ke kutub digunakan untuk mengidentifikasi struktur bawah permukaan Laut Flores. Berdasarkan peta kontur anomali medan magnetik total dilokasi penelitian secara umum terdistribusi antara -156.1 nT sampai 321.9 nT. Anomali rendah -156.1 nT sampai 0 cenderung mengikuti titik pengukuran yang berdekatan dengan adanya indikasi gunung api bawah laut di lokasi penelitian.Kata Kunci : metode magnetik, anomali medan magnet total, reduksi ke kutub, laut flores

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17

Alpiana, Fila, Catur Purwanto, Yudha Arman, and Apriansyah Apriansyah. "Identifikasi Struktur Geologi Dasar Laut Sulawesi Berdasarkan Anomali Magnetik." PRISMA FISIKA 7, no. 3 (January 2, 2020): 162. http://dx.doi.org/10.26418/pf.v7i3.36110.

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Penelitian ini bertujuan untuk mengetahui struktur geologi di Laut Sulawesi dengan menggunakan metode magnetik. Data yang diperoleh dari hasil survei yaitu data intensitas medan magnet. Pengolahan data awal dilakukan koreksi harian dan koreksi IGRF (International Geomagnetic Reference Field) pada data hasil survei untuk mendapatkan anomali medan magnet total. Kemudian di reduksi ke kutub dan selanjutnya dilakukan pemisahan anomali lokal dan regional dengan filter gaussian regional/residual untuk mendapatkan anomali lokal. Didapatkan nilai anomali magnetik pada daerah penelitian -290,0 nT hingga 335,6 nT. Berdasarkan anomali magnetik dan pola struktur daerah penelitian, diduga adanya Struktur geologi yaitu sesar. Variasi nilai intensitas medan magnet merupakan parameter dalam menentukan nilai suseptibilitas. Nilai suseptibilitas Laut Sulawesi yaitu 0,0656 SI hingga 0,0677 SI. Berdasarkan nilai suseptibilitas, struktur geologi daerah penelitian didominasi batuan jenis andesit, basaltik, dan batuan metamorf.Kata Kunci: Metode Magnetik, Struktur Geologi, Suseptibilitas, Anomali Magnetik

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18

Kataoka, Ryuho, and Shin’ya Nakano. "Auroral zone over the last 3000 years." Journal of Space Weather and Space Climate 11 (2021): 46. http://dx.doi.org/10.1051/swsc/2021030.

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We investigated the global shape of the auroral zone over the last 3000 years using paleomagnetism CALS models. A similar method of apex latitude as proposed by Oguti (1993) [J Geophys Res 98(A7): 11649–11655; J Geomag Geoelectr 45, 231–242] was adopted to draw the auroral zone. The Oguti method is examined using 50-year data from ground-based magnetometers located at high latitudes, using International Geomagnetic Reference Field (IGRF) models. The equatorward auroral limit during magnetic storms was also examined using more than 20 years of data from the Defense Meteorological Satellite Program (DMSP) satellites. The reconstructed auroral zone and the equatorward auroral limit were compared with the historical auroral witness records for 1200 AD and 1800 AD. We concluded that the 12th and 18th centuries were excellent periods for Japan and the United Kingdom, respectively, to observe auroras over the last 3000 years.

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19

Mahmudi, Dinni, Muhammad Isa, and Didik Sugiyanto. "Interpretation of Near Surface Based on the Magnetic Data at Geothermal Area, Jaboi, Sabang." Journal of Aceh Physics Society 8, no. 3 (September 25, 2019): 90–93. http://dx.doi.org/10.24815/jacps.v8i3.14550.

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Telah dilakukan penelitian geofisika menggunakan metode magnetik untuk mendapatkan struktur bawah permukaan di daerah prospek panas bumi Jaboi, Sukajaya, Kota Sabang. Pengukuran medan magnetik total dilakukan pada 40 titik menggunakan Proton Precession Magnetometer (PPM). Daerah Jaboi memiliki sudut inkinasi -4.416 dan deklinasi -0.875 dengan nilai medan magnetik total berkisar antara 41550 hingga 42600 nT. Untuk mendapatkan nilai anomali magnetik dilakukan koreksi diurnal dan koreksi IGRF (International Geomagnetic Reference Field). Setelah koreksi dilakukan diperoleh nilai anomali magnetik daerah panas bumi Jaboi antara -200 nT sampai dengan -950 nT. Selanjutnya hasil anomali magnetik ini digunakan dalam memodelkan struktur bawah permukaan dengan panjang lintasan 1800 m dari Tenggara-Barat Laut. Berdasarkan interpretasi data anomali magnetik menunjukkan daerah penelitian didominasi oleh anomali rendah yang berarti daerah manifestasi panas bumi. Interpretasi anomali tinggi dan rendah menunjukkan adanya patahan yang diduga sebagai patahan Ceuneuhot. Dari hasil pemodelan 2D menggunakan software Mag2DC, menunjukkan bahwa terdapat 5 lapisan dengan kedalaman 0 - 1000 m. Lapisan-lapisan ini adalah soil ( = 0,00 x 10-6 SI), andesit terubah ( = 13,408 x 10-6 SI), breksi tufa terubah ( = 12,686 x 10-6 SI), andesit terubah ( = 13,423 x 10-6 SI) dan breksi andesit ( = 13,535 x 10-6 SI). Melalui pemodelan ini diyakini zona patahan adalah patahan Ceuneuhot. Geophysical reasearch by using magnetic method was done in order to obtain subsurface structure of geothermal prospect area Jaboi, Sukajaya, Sabang City. The measurement of total magnetic field was taken at 40 points using Proton Precession Magnetometer (PPM). Jaboi area has an inklination angle -4.416 and declination angle -0.875 which has total magnetic field range between 41550 to 42600 nT. Diurnal Correction and IGRF (International Geomagnetic Reference Field) correction was used to obtain magnetic anomalies. The values of magnetic anomalies in Jaboi Geothermal Area is -200 to -950 nT. The result of magnetic anomalies was used to modelled the subsurface structure with profile distance is about 1800 m from Southeast to Northwest. Based on the magnetic anomalies data, the reaserch area dominated by low anomalies that indicated geothermal manifestation area. High and low magnetic anomalies indicated a fault that estimated as Ceuneuhot fault. From the result of 2D modelling using software Mag2DC, showed that the research area consist of 5 subsurface structure from 0 – 1000 m depth. The layers are soil ( = 0.00 × 10-6 SI), altered andesite ( = 13.408 × 10-6 SI), altered breccia-tuff ( = 12.686 × 10-6 SI), altered andesite ( = 13.423 × 10-6 SI), and breccia-andesite ( = 13.535 × 10-6 SI). Also from the model was obtained the Ceuneuhot fault zone. Keywords: Magnetik, Anomali Magnetik, Struktur Bawah Permukaan, Panas Bumi

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Melo, Felipe F., and Valéria C. F. Barbosa. "Correct structural index in Euler deconvolution via base-level estimates." GEOPHYSICS 83, no. 6 (November 1, 2018): J87—J98. http://dx.doi.org/10.1190/geo2017-0774.1.

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In most applications, the Euler deconvolution aims to define the nature (type) of the geologic source (i.e., the structural index [SI]) and its depth position. However, Euler deconvolution also estimates the horizontal positions of the sources and the base level of the magnetic anomaly. To determine the correct SI, most authors take advantage of the clustering of depth estimates. We have analyzed Euler’s equation to indicate that random variables contaminating the magnetic observations and its gradients affect the base-level estimates if, and only if, the SI is not assumed correctly. Grounded on this theoretical analysis and assuming a set of tentative SIs, we have developed a new criterion for determining the correct SI by means of the minimum standard deviation of base-level estimates. We performed synthetic tests simulating multiple magnetic sources with different SIs. To produce mid and strongly interfering synthetic magnetic anomalies, we added constant and nonlinear backgrounds to the anomalies and approximated the simulated sources laterally. If the magnetic anomalies are weakly interfering, the minima standard deviations either of the depth or base-level estimates can be used to determine the correct SI. However, if the magnetic anomalies are strongly interfering, only the minimum standard deviation of the base-level estimates can determine the SI correctly. These tests also show that Euler deconvolution does not require that the magnetic data be corrected for the regional fields (e.g., International Geomagnetic Reference Field [IGRF]). Tests on real data from part of the Goiás Alkaline Province, Brazil, confirm the potential of the minimum standard deviation of base-level estimates in determining the SIs of the sources by applying Euler deconvolution either to total-field measurements or to total-field anomaly (corrected for IGRF). Our result suggests three plug intrusions giving rise to the Diorama anomaly and dipole-like sources yielding Arenópolis and Montes Claros de Goiás anomalies.

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21

Tsokas, Gregory N., Alexandros Stampolidis, Antonis D. Angelopoulos, and Stefanos Kilias. "Analysis of potential field anomalies in Lavrion mining area, Greece." GEOPHYSICS 63, no. 6 (November 1998): 1965–70. http://dx.doi.org/10.1190/1.1444490.

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Mining activities in Lavrion began during the first millennium B.C. after the decline of ancient Athens and then restarted more deliberately during the nineteenth century. Aeromagnetic data from a 1967 survey of the mining area was recompiled, processed, and interpreted for the present study. The original flight lines were digitized and leveled, and the international geomagnetic reference field (IGRF) was removed. The data were inverted by means of a terracing technique that defines separate domains of uniform distribution of physical properties that cause the magnetic anomalies. The log power spectrum was computed; along with the results of terracing, it suggested the existence of two sources of the magnetic anomaly. The long‐wavelength anomaly reflects a large, concealed body that is most probably a granitic intrusion, consistent with local geological evidence. The source of the short‐wavelength anomaly is a strongly magnetized body attributed to the net effect of various thin, magnetite‐bearing sulfide zones. The anomalies were then separated in the wavenumber domain. Magnetic susceptibility measurements were made in situ on the exposed parts of the local formations. Three‐dimensional models whose effect simulates the observed anomalies were calculated. Results of the modeling show that the large magnetic body is buried at 0.68 km depth. The small, relatively shallow body is about 0.035 km thick and buried at 0.6 km depth. The bodies do not show any corresponding gravity anomaly on the regional Bouguer gravity anomaly map.

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Heningtyas, Heningtyas, Nugroho Budi Wibowo, and Denny Darmawan. "Pemodelan 2D dan 3D Metode Geomagnet untuk Interpretasi Litologi dan Analisis Patahan di Jalur Sesar Oyo." Jurnal Lingkungan dan Bencana Geologi 10, no. 3 (January 3, 2020): 115. http://dx.doi.org/10.34126/jlbg.v10i3.157.

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Gempa susulan setelah gempabumi Yogyakarta Tahun 2006 memiliki hiposenter bukan di sepanjang Sesar Opak tapi cenderung di sekitar unidentified fault yang berjarak 10 – 15 km sebelah timur pegunungan Gunung Kidul. Unidentified fault tersebut berkorelasi dengan keberadaan jalur Sesar Oyo. Metode geofisika yang dapat diterapkan untuk mengidentifikasi keberadaan jalur sesar adalah metode geomagnet. Penelitian ini bertujuan untuk mengetahui pola sebaran anomali medan magnet di sekitar jalur Sesar Oyo, mengetahui susunan formasi dan jalur Sesar Oyo berdasarkan pemodelan geomagnet. Pengambilan data dilakukan menggunakan PPM dengan 35 titik pengamatan dan spasi antar titik pengamatan 1,5 km. Pengolahan data dilakukan dengan koreksi variasi harian, koreksi IGRF(International Geomagnetics Reference Field), RTP (Reduction to Pole) dan Upward Continuation. Pemodelan dilakukan dengan menganalisis anomali medan magnet yang telah direduksi ke kutub dan kontinuasi ke atas dengan ketinggian 2500 m. Hasil analisa menunjukkan rentang nilai anomali medan magnet di kawasan penelitian adalah 180 nT – 660 nT, yang menunjukkan kontras keberadaan blok sesar. Hasil pemodelan 2D menunjukkan kawasan penelitian didominasi oleh 3 formasi batuan utama yaitu batubasalt-andesitik Formasi Nglanggran, batupasir Formasi Sambipitu, dan batugamping Formasi Wonosari. Hasil pemodelan 3D menunjukkan Sesar Oyo merupakan sesar geser dengan kedalaman 150 – 300 m, jalur sesar tersebut terbagi menjadi 2 segmen yaitu dengan arah N120°E sepanjang 5,8 km dan N160°E dengan panjang 2,5 km.

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23

Ibraheem, Ismael M., Menna Haggag, and Bülent Tezkan. "Edge Detectors as Structural Imaging Tools Using Aeromagnetic Data: A Case Study of Sohag Area, Egypt." Geosciences 9, no. 5 (May 10, 2019): 211. http://dx.doi.org/10.3390/geosciences9050211.

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The present study was designed to give a clear and comprehensive understanding of the structural situation in the Sohag region and surrounding area by applying several edge detectors to aeromagnetic data. In this research, the International Geomagnetic Reference Field (IGRF) values were removed from the aeromagnetic data and the data obtained were then reduced to the north magnetic pole (RTP). A combination of different edge detectors was applied to determine the boundaries of the magnetic sources. A good correlation was noticed between these techniques, indicating that their integration can contribute to delineating the structural framework of the area. Consequently, a detailed structural map based on the results was constructed. Generally, E-W, N45-60E, and N15-30W directions represent the main tectonic trends in the survey area. The structural map shows the existence of two main basins constituting the most probable places for hydrocarbon accumulation. The results of this study provide structural information that can constitute an invaluable contribution to the gas and oil exploration process in this promising area. They show also that the decision in choosing the location of the drilled boreholes (Balyana-1 and Gerga) was incorrect, as they were drilled in localities within an area of a thin sedimentary cover.

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Prasetyawan, Indra Budi. "The Origin of Back-Arc Spreading in The Eastern Edge of Scotia Plate." BULETIN OSEANOGRAFI MARINA 5, no. 1 (April 3, 2016): 21. http://dx.doi.org/10.14710/buloma.v5i1.11292.

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The origin and evolution of back-arc spreading in the eastern edge of Scotia Plate will be discussed in this paper. The Scotia Plate is a tectonicplate on the edge of the South Atlantic and Southern Ocean, located between the South American and Antartic plates. The East Scotia Ridge (ESR) in the eastern edge of Scotia Plate, forned due to subduction of the South American plate beneath the South Sandwich plate along the South Sandwich Island arc. The methods and techniques of data acquisition used were data from absolution motions and data from magnetic anomalies and bathymetric data. Magnetic anomalies and bathymetric data that used in this paper consist of two sets data. First, magnetic anomalies and bathymetric data which were obtained by aboard HMS Endurance in the 1969-70 austral summer, and the second, magnetic anomalies and bathymetric data which were obtained after removal of the International Geomagnetic Reference Field (IGRF). Absolution motion analyses in the subduction zones of Sandwich plate results that form back-arc spreading in East Scotia Ridge showing high deformation for slow moving upper plates. Where back-arc spreading is associated with upper plate retreat that reaches 26.9 mm/year and have back-arc deformation style consistent with upper plate absolute. Key Words: Geological oceanography, Scotia plate, back-arc spreading

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25

Mukazairo, Delia Septi Evani, Refrizon Refrizon, and Nanang Sugianto. "Peta Anomali Magnetik Daerah Mineralisasi Emas Di Desa Tambang Sawah Kecamatan Lebong Utara Berdasarkan Pengukuran Magnetik." Newton-Maxwell Journal of Physics 1, no. 1 (December 26, 2020): 19–24. http://dx.doi.org/10.33369/nmj.v1i1.14292.

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Sebaran zona mineralisasi emas menjadi permasalahan yang serius bagi penambang tradisional emas di Desa Tambang Sawah Kabupaten Lebong. Penelitian ini bertujuan untuk memetakan pola sebaran zona mineralisasi emas di Desa Tambang Sawah Kecamatan Lebong Utara yang didasarkan pada anomali magnetik yang memiliki hubungan fisis terhadap mineralisasi emas. Pengambilan data dilakukan dengan menggunakan Proton Precession Magnetometer (PPM) yang terdiri dari 165 titik pengukuran. Koreksi IGRF (International Geomagnetics Reference Field) dan koreksi variasi harian dilakukan untuk mendapatkan anomali medan magnet total. Hasil penelitian menunjukkan bahwa anomali magnetik tinggi berada pada nilai 238,4 nT sampai 533,3 nT. Anomali magnetik tinggi teridentifikasi pada bagian barat laut dan timur daerah penelitian. Anomali rendah menyebar dari arah barat hingga arah timur dengan rentang nilai anomali magnetik -503 nT hingga -19 nT. Nilai intensitas anomali magnetik rendah yang bernilai -503,2 nT hingga 102,4 nT diduga sebagai zona pembentukan mineral emas. Berdasarkan sebaran nilai anomali magnetik, zona mineralisasi emas di daerah Tambang Sawah merupakan mineralisasi emas sulfidasi rendah yang berhubungan dengan geothermal yang ada disekitarnya.

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26

Gianibelli, Julio C., Jacqueline Köhn, and Marta E. Ghidella. "Testing Geomagnetic Reference Field models for 1990-2000 with data from the Trelew Geomagnetic Observatory, Argentina." Geofísica Internacional 42, no. 4 (October 1, 2003): 635–39. http://dx.doi.org/10.22201/igeof.00167169p.2003.42.4.317.

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En los relevamientos magnéticos realizados sobre la superficie de la Tierra se utiliza el Campo Geomagnético Internacional de Referencia (IGRF) para sustraer la contribución del campo principal de la Tierra. Cada cinco años se publica un nuevo modelo de IGRF y la variación secular del período previo debe ser actualizada, generándose el denominado modelo DGRF. Una vez que el DGRF es publicado, las anomalías magnéticas calculadas previamente deben ser recalculadas. La actualización de las anomalías podría ser particularmente importante para relevamientos magnéticos regionales o para compilaciones de datos magnéticos adquiridos en diferentes épocas. En este trabajo se muestra la importancia de esta corrección, particularmente para el periodo 1995-2000, en el cual la diferencia DGRF-IGRF es llamativamente apreciable. Se documenta la validez de la corrección utilizando datos del Observatorio Geomagnético Permanente de Trelew, Argentina.

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27

Showstack, Randy. "Updated International Geomagnetic Reference Field." Eos, Transactions American Geophysical Union 91, no. 16 (April 20, 2010): 142. http://dx.doi.org/10.1029/2010eo160003.

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28

Mandea, Mioara, Susan Macmillan, Tatiana Bondar, Vadim Golovkov, Benoit Langlais, Frank Lowes, Nils Olsen, John Quinn, and Terry Sabaka. "International geomagnetic reference field — 2000." Physics of the Earth and Planetary Interiors 120, no. 1-2 (June 2000): 39–42. http://dx.doi.org/10.1016/s0031-9201(00)00153-9.

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29

Mandea, M. "International Geomagnetic Reference Field—2000." Pure and Applied Geophysics 157, no. 10 (October 2000): 1797–802. http://dx.doi.org/10.1007/pl00001062.

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30

INTERNATIONAL ASSOCIATION OF GEOMAG. "International Geomagnetic Reference Field, 1991 Revision." Journal of geomagnetism and geoelectricity 43, no. 12 (1991): 1007–12. http://dx.doi.org/10.5636/jgg.43.1007.

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31

Maus, Stefan, and Susan MacMillan. "10th Generation International Geomagnetic Reference Field." Eos, Transactions American Geophysical Union 86, no. 16 (2005): 159. http://dx.doi.org/10.1029/2005eo160006.

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32

Barraclough, D. R. "International Geomagnetic Reference Field Revision 1987." Geophysical Journal International 93, no. 1 (April 1, 1988): 187–89. http://dx.doi.org/10.1111/j.1365-246x.1988.tb01397.x.

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33

Barraclough, David R. "Geophysics: International Geomagnetic Reference Field revision." Nature 318, no. 6044 (November 1985): 316. http://dx.doi.org/10.1038/318316a0.

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34

Langel, R. A. "International Geomagnetic Reference Field revision 1987." Eos, Transactions American Geophysical Union 69, no. 17 (1988): 557. http://dx.doi.org/10.1029/88eo00146.

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35

Langel, R. A. "International Geomagnetic Reference Field, 1991 revision." Pure and Applied Geophysics PAGEOPH 137, no. 3 (1991): 301–8. http://dx.doi.org/10.1007/bf00876994.

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36

NEWITT, L. R., and G. V. HAINES. "Comparison of IGRF Candidate Models with the Canadian Geomagnetic Reference Field for 1985-1995." Journal of geomagnetism and geoelectricity 44, no. 9 (1992): 871–80. http://dx.doi.org/10.5636/jgg.44.871.

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37

Metodiev, Metodi, and Petya Trifonova. "Bulgarian Geomagnetic Reference Field (BulGRF) for 2015.0 and secular variation prediction model up to 2020." Annales Geophysicae 35, no. 5 (September 12, 2017): 1085–92. http://dx.doi.org/10.5194/angeo-35-1085-2017.

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Abstract. The Bulgarian Geomagnetic Reference Field (BulGRF) for 2015.0 epoch and its secular variation model prediction up to 2020.0 is produced and presented in this paper. The main field model is based on the well-known polynomial approximation in latitude and longitude of the geomagnetic field elements. The challenge in our modelling strategy was to update the absolute field geomagnetic data from 1980.0 up to 2015.0 using secular measurements unevenly distributed in time and space. As a result, our model gives a set of six coefficients for the horizontal H, vertical Z, total field F, and declination D elements of the geomagnetic field. The extrapolation of BulGRF to 2020 is based on an autoregressive forecasting of the Panagyurishte observatory annual means. Comparison of the field values predicted by the model with Panagyurishte (PAG) observatory annual mean data and two vector field measurements performed in 2015 shows a close match with IGRF-12 values and some difference with the real (measured) values, which is probably due to the influence of crustal sources. BulGRF proves to be a reliable alternative to the global geomagnetic field models which together with its simplicity makes it a useful tool for reducing magnetic surveys to a common epoch carried out over the Bulgarian territory up to 2020.

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38

LANGEL, R. A. "International Geomagnetic Reference Field: The Sixth Generation." Journal of geomagnetism and geoelectricity 44, no. 9 (1992): 679–707. http://dx.doi.org/10.5636/jgg.44.679.

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39

Barton, C. E. "International Geomagnetic Reference Field: The Seventh Generation." Journal of geomagnetism and geoelectricity 49, no. 2 (1997): 123–48. http://dx.doi.org/10.5636/jgg.49.123.

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40

Maus, S., S. Macmillan, T. Chernova, S. Choi, D. Dater, V. Golovkov, V. Lesur, et al. "The 10th generation international geomagnetic reference field." Physics of the Earth and Planetary Interiors 151, no. 3-4 (August 2005): 320–22. http://dx.doi.org/10.1016/j.pepi.2005.03.006.

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41

Macmillan, S. "The 9th Generation International Geomagnetic Reference Field." Earth, Planets and Space 55, no. 8 (August 2003): i—ii. http://dx.doi.org/10.1186/bf03351778.

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42

Macmillan, Susan, and Stefan Maus. "International Geomagnetic Reference Field—the tenth generation." Earth, Planets and Space 57, no. 12 (December 2005): 1135–40. http://dx.doi.org/10.1186/bf03351896.

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43

Mandea, Mioara, and Susan Macmillan. "International Geomagnetic Reference Field—the eighth generation." Earth, Planets and Space 52, no. 12 (December 2000): 1119–24. http://dx.doi.org/10.1186/bf03352342.

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44

Finlay, C. C., S. Maus, C. D. Beggan, T. N. Bondar, A. Chambodut, T. A. Chernova, A. Chulliat, et al. "International Geomagnetic Reference Field: the eleventh generation." Geophysical Journal International 183, no. 3 (October 12, 2010): 1216–30. http://dx.doi.org/10.1111/j.1365-246x.2010.04804.x.

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45

Macmillan, S., S. Maus, T. Bondar, A. Chambodut, V. Golovkov, R. Holme, B. Langlais, et al. "The 9th-Generation International Geomagnetic Reference Field." Geophysical Journal International 155, no. 3 (December 2003): 1051–56. http://dx.doi.org/10.1111/j.1365-246x.2003.02102.x.

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46

Macmillan, S., S. Maus, T. Bondar, A. Chambodut, V. Golovkov, R. Holme, B. Langlais, et al. "Ninth generation international geomagnetic reference field released." Eos, Transactions American Geophysical Union 84, no. 46 (November 18, 2003): 503. http://dx.doi.org/10.1029/2003eo460004.

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47

Barraclough, David R. "International geomagnetic reference field: the fourth generation." Physics of the Earth and Planetary Interiors 48, no. 3-4 (October 1987): 279–92. http://dx.doi.org/10.1016/0031-9201(87)90150-6.

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48

Barraclough, David R. "Scientific note International Geomagnetic Reference Field revision 1985." Pure and Applied Geophysics PAGEOPH 123, no. 4 (1985): 641–45. http://dx.doi.org/10.1007/bf00877460.

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49

Barraclough, David R. "Scientific note International Geomagnetic Reference Field revision 1987." Pure and Applied Geophysics PAGEOPH 127, no. 1 (1988): 155–60. http://dx.doi.org/10.1007/bf00878696.

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50

Barton, C. E. "Candidate models sought for international geomagnetic reference field 2000." Eos, Transactions American Geophysical Union 79, no. 51 (1998): 627. http://dx.doi.org/10.1029/98eo00447.

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