scholarly journals IDENTIFIKASI POLA SEBARAN INTRUSI BATUAN BAWAH PERMUKAAN MENGGUNAKAN METODE GEOMAGNET DI SUNGAI JENELATA KABUPATEN GOWA

2017 ◽  
Vol 1 (1) ◽  
pp. 17 ◽  
Author(s):  
Nur Hidayat Nurdin ◽  
Muh. Altin Massinai ◽  
Sabrianto Aswad
Keyword(s):  
Magnetic Field ◽  
Forward Modeling ◽  
Geological Structure ◽  
Quantitative Interpretation ◽  
Pyroclastic Rocks ◽  
South Sulawesi ◽  
Qualitative Interpretation ◽  
Upward Continuation ◽  
Magnetometer Data ◽  
Diurnal Correction

AbstrakPenelitian ini dilakukan di Sungai Jenelata, Kabupaten Gowa, Sulawesi Selatan mengunakan metode geomagnet . Tujuan dari penelitian ini yaitu mengidentifikasi struktur geologi bawah permukaan pada daerah penelitian. Jumlah titik pengukuran sebanyak 248 dengan area seluas 70 × 300 meter. Akuisisi data dilakukan dengan menggunakan satu alat magnetometer. Sementara pengolahan data menggunakan koreksi harian dan koreksi IGRF serta filter upward continuation. Pemodelan dilakukan dengan metode forward modeling dengan menggunakan perangkat lunak Mag2DC. Medan magnetik total berkisar antara 42.456 sampai 43.111,6 nT. Berdasarkan interpretasi kualitatif pada kontur anomali magnetik lokal didapatkan variasi nilai anomali antara -320 sampai 240 nT. Sedangkan interpretasi kuantitatif menunjukkan adanya batuan basalt dengan nilai suseptibilitas sampai SI, yang menerobos batuan pyroclastic dengan nilai suseptibilitas hingga SI dalam dalam bentuk dyke. Kata Kunci: Geomagnet, dyke, Suseptibilitas, Sungai Jenelata.AbstractThis research has been conducted using geomagnetic method at Jenelata River, Gowa regency, South Sulawesi. The purpose of this study is to identify subsurface geological structure of the study area. The number of measurement points as much as 248 points with area 70 × 300 meters. The process of data acquisition using a magnetometer. Data processing was carried out with the diurnal correction and IGRF correction and using filter upward continuation. Modelling conducted using forward modeling using the software Mag2DC. The total magnetic field ranges from 42,456 to 43,111.6 nT. Based on a qualitative interpretation obtain local magnetic anomaly contour variations values between -320 to 240 nT. While the quantitative interpretation indicates basalt rocks with susceptibility values  to SI, which breached pyroclastic rocks with susceptibility values to SI, in the form of dyke. Keywords: Geomagnetic, dyke, Susceptibility, Jenelata River

scholarly journals IDENTIFIKASI PATAHAN DI DESA TAMAN AYU KECAMATAN GERUNG KABUPATEN LOMBOK BARAT MENGGUNAKAN METODE GEOMAGNET

2020 ◽  
Vol 6 (2) ◽  
pp. 145-155
Author(s):  
Deni Hermansyah ◽  
Bakti Sukrisna ◽  
Suhayat Minardi
Keyword(s):  
Magnetic Field ◽  
Cross Sections ◽  
Inverse Modeling ◽  
Target Location ◽  
Continuation Method ◽  
Normal Fault ◽  
Quantitative Interpretation ◽  
Geological Structures ◽  
Qualitative Interpretation ◽  
The Magnetic Field

This research aimed to identify the presence of faults in Taman Ayu Village, Gerung District, West Lombok Regency by mapping the magnetic field. The fault outcrops found near this location becomes the reason to suspected the fault existence that reaching residents, farming area and access roads, so it is necessary to study the type, depth and direction of the fault. Measurements were made on 11 lines with a length of each line is 3 km. Each line of measurement is 300 m apart from each other and the distance between measurement points is 50 m, 100 m, and 200 m depending on the distance from the target location. Separation between regional anomalies and residual anomalies using the upward continuation method at an altitude of 1000 m. Qualitative interpretation of residual anomalies results in low anomalies with values from -890.9 nT to 897.3 nT. Quantitative interpretation of the five cross sections by the inverse modeling method with Oasis Montaj 6.4.2 software resulting subsurface geological structures in the form of normal fault. This normal fault is at a depth of 30 m to 480 m which is composed of layers of silt, sandy silt, sand, clay and breccia. The fault passes through Gapuk Village, Taman Ayu and Kebon Ayu and passes through the highway in Northeast – Southwest direction

ESTIMATION OF SOURCE PARAMETERS IN IBADAN, SOUTH – WESTERN NIGERIA USING DIGITIZED AEROMAGNETIC DATA

2018 ◽  
Vol 14 (2) ◽  
pp. 15-28
Author(s):  
A A ALABI ◽  
O OLOWOFELA
Keyword(s):  
Magnetic Susceptibility ◽  
Source Parameters ◽  
Granite Gneiss ◽  
Geological Structure ◽  
Magnetic Data ◽  
Susceptibility Map ◽  
Rock Types ◽  
Upward Continuation ◽  
Magnetic Basement ◽  
Local Wavenumber

Airborne magnetic data covering geographical latitudes of 7000‟N to 7030‟N and longitudes of 3 30′E to 4 00′E within Ibadan area were obtained from Nigeria Geology Survey Agency. The data were ana-lyzed to map the sub surface structure and the source parameters were deduced from the quantitative and qualitative interpretation of magnetic data. The upward continuation technique was used to de-emphasize short – wavelength anomaly while the depth to magnetic sources in the area was deter-mined using local wavenumber technique, the analytic signal was also employed to obtain the depths of the magnetic basement. Analysis involving the local wavenumber, upward continuation and appar-ent magnetic susceptibility techniques significantly improves the interpretation of magnetic data in terms of delineating the geological structure, source parameter and magnetic susceptibility within Iba-dan area.. These depth ranges from 0.607km to 2.48km. The apparent susceptibility map at the cut-off wavelength of 50 m ranges from -0.00012 to 0.00079 which agree with the susceptibility value of some rock types; granite gneiss, migmatite biotite gneiss, biotite muscovite granite, hornblende granite, quartz and schists. The result of the local wavenumber suggests variation along the profiles in the surface of magnetic basement across the study area.

scholarly journals Magnetometer in-flight offset accuracy for the BepiColombo spacecraft

2020 ◽  
Vol 38 (4) ◽  
pp. 823-832 ◽  
Author(s):  
Daniel Schmid ◽  
Ferdinand Plaschke ◽  
Yasuhito Narita ◽  
Daniel Heyner ◽  
Johannes Z. D. Mieth ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Measurements ◽  
Observation Time ◽  
Space Environment ◽  
Method Performance ◽  
Mode Method ◽  
Magnetometer Data ◽  
Mirror Mode ◽  
Fluctuation Method

Abstract. Recently the two-spacecraft mission BepiColombo launched to explore the plasma and magnetic field environment of Mercury. Both spacecraft, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO, also referred to as Mio), are equipped with fluxgate magnetometers, which have proven to be well-suited to measure the magnetic field in space with high precision. Nevertheless, accurate magnetic field measurements require proper in-flight calibration. In particular the magnetometer offset, which relates relative fluxgate readings into an absolute value, needs to be determined with high accuracy. Usually, the offsets are evaluated from observations of Alfvénic fluctuations in the pristine solar wind, if those are available. An alternative offset determination method, which is based on the observation of highly compressional fluctuations instead of incompressible Alfvénic fluctuations, is the so-called mirror mode technique. To evaluate the method performance in the Hermean environment, we analyze four years of MESSENGER (MErcury Surface, Space ENvironment, GEophysics and Ranging) magnetometer data, which are calibrated by the Alfvénic fluctuation method, and compare it with the accuracy and error of the offsets determined by the mirror mode method in different plasma environments around Mercury. We show that the mirror mode method yields the same offset estimates and thereby confirms its applicability. Furthermore, we evaluate the spacecraft observation time within different regions necessary to obtain reliable offset estimates. Although the lowest percentage of strong compressional fluctuations are observed in the solar wind, this region is most suitable for an accurate offset determination with the mirror mode method. 132 h of solar wind data are sufficient to determine the offset to within 0.5 nT, while thousands of hours are necessary to reach this accuracy in the magnetosheath or within the magnetosphere. We conclude that in the solar wind the mirror mode method might be a good complementary approach to the Alfvénic fluctuation method to determine the (spin-axis) offset of the Mio magnetometer.

Recording the Aurora at Seismometers across Alaska

2020 ◽  
Vol 91 (6) ◽  
pp. 3039-3053 ◽  
Author(s):  
Carl Tape ◽  
Adam T. Ringler ◽  
Don L. Hampton
Keyword(s):  
Magnetic Field ◽  
Seismic Data ◽  
Vertical Component ◽  
Seismic Array ◽  
Magnetic Shielding ◽  
Data Sets ◽  
S Waves ◽  
Auroral Activity ◽  
Seismic Sensors ◽  
Magnetometer Data

Abstract We examine three continuously recording data sets related to the aurora: all-sky camera images, three-component magnetometer data, and vertical-component, broadband seismic data as part of the EarthScope project (2014 to present). Across Alaska there are six all-sky cameras, 13 magnetometers, and >200 seismometers. The all-sky images and magnetometers have the same objective, which is to monitor space weather and improve our understanding of auroral activity, including the influence on magnetic fields in the ground. These variations in the magnetic field are also visible on seismometers, to the extent that during an auroral event, the long-period (40–800 s) waves recorded by a seismometer are magnetic field variations, not true ground motion. Although this is a problem—one that can be rectified with magnetic shielding at each seismometer site—it is also an opportunity because the present seismic array in Alaska is much broader than the coverage by magnetometers and all-sky cameras. Here we focus on three aurora events and document a direct link between aurora images in the night sky and seismometer recordings on ground. Simultaneous recordings by magnetometers provide a critical link between the sky images and the seismometer recordings. We document qualitative correlations among sky, magnetic, and seismic data. The findings suggest that the signature of auroral activity is widespread across seismometers in Alaska, implying that the seismic array could be used to enhance the spatial resolution of the existing network of all-sky cameras and magnetometers. Future efforts to improve the multisensor seismic stations in Alaska, for the purpose of monitoring seismic and auroral activity, should consider installation of all-sky cameras, installation of magnetometers, and magnetic shielding of seismic sensors.

Fast 3D forward modeling of the magnetic field and gradient tensor on an undulated surface

2018 ◽  
Vol 15 (3-4) ◽  
pp. 500-512
Author(s):  
Kun Li ◽  
Long-Wei Chen ◽  
Qing-Rui Chen ◽  
Shi-Kun Dai ◽  
Qian-Jiang Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Forward Modeling ◽  
Gradient Tensor ◽  
The Magnetic Field ◽  
3D Forward Modeling

scholarly journals Europa's Alfvén wing: shrinkage and displacement influenced by an induced magnetic field

2007 ◽  
Vol 25 (4) ◽  
pp. 905-914 ◽  
Author(s):  
M. Volwerk ◽  
K. Khurana ◽  
M. Kivelson
Keyword(s):  
Magnetic Field ◽  
Plasma Density ◽  
Geometric Modeling ◽  
Numerical Models ◽  
Background Field ◽  
Entry And Exit ◽  
Induced Magnetic Field ◽  
Background Magnetic Field ◽  
Magnetometer Data ◽  
Induced Field

Abstract. The Galileo magnetometer data are used to investigate the structure of the Alfvén wing during three flybys of Europa. The presence of an induced magnetic field is shown to shrink the cross section of the Alfvén wing and offset it along the direction radial to Jupiter. Both the shrinkage and the offset depend on the strength of the induced field. The entry and exit points of the spacecraft into and out of the Alfvén wings are modeled to determine the angle between the wings and the background magnetic field. Tracing of the Alfvén characteristics in a model magnetic field consisting of Jupiter's background field and an induced field in Europa produces an offset and shrinking of the Alfvén wing consistent with the geometric modeling. Thus we believe that the Alfvén wing properties have been determined correctly. The Alfvén wing angle is directly proportional to the local Alfvén velocity, and is thus a probe for the local plasma density. We show that the inferred plasma density can be understood in terms of the electron density measured by the plasma wave experiment. When Europa is located in the Jovian plasma sheet the derived mass-per-charge exceeds the previous estimates, which is a result of increased pickup of sputtered ions near the moon. The estimated rate of O2+ pickup agrees well with the results from numerical models.

THE USE OF POISSON’S RELATION FOR THE EXTRACTION OF PSEUDOTOTAL MAGNETIC FIELD INTENSITY FROM GRAVITY OBSERVATIONS

Geophysics ◽  
1971 ◽  
Vol 36 (3) ◽  
pp. 605-608 ◽  
Author(s):  
Edwin S. Robinson
Keyword(s):  
Magnetic Field ◽  
Gravity Field ◽  
Field Data ◽  
Field Potential ◽  
Geological Structure ◽  
Common Source ◽  
Uniform Density ◽  
Practical Applications ◽  
Uniform Magnetization ◽  
Gravity Fields

Investigation of geological structure by gravimetric and magnetic field surveys requires consideration of relationships between gravity anomaly and magnetic anomaly generating sources. The possibility of using Poisson’s Relation to examine magnetic and gravity fields related to a common source is intriguing. This relation is expressed as follows: [Formula: see text] (1) where A (x, y, z) is the magnetic field potential and U (x, y, z) is the gravity field potential at a point in space due to a source of uniform density ρ and uniform magnetization I in the direction α. This expression has been used to derive magnetic anomalies over idealized forms (Nettleton, 1940) and, by Baranov (1957), to extract pseudogravity fields from magnetic field data. The purpose of this paper is to develop an expression for extracting a pseudomagnetic field from gravity field data and to examine the practical applications of this expression.

scholarly journals Model for vortex turbulence with discontinuities in the solar wind

2003 ◽  
Vol 10 (4/5) ◽  
pp. 335-343 ◽  
Author(s):  
O. P. Verkhoglyadova ◽  
B. Dasgupta ◽  
B. T. Tsurutani
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
High Speed ◽  
Vector Fields ◽  
Field Vector ◽  
Theoretical Modelling ◽  
Occurrence Rate ◽  
Embedded Discontinuities ◽  
Magnetometer Data ◽  
Speed Solar Wind

Abstract. A model of vortex with embedded discontinuities in plasma flow is developed in the framework of ideal MHD in a low b plasma. Vortex structures are considered as a result of 2-D evolution of nonlinear shear Alfvén waves in the heliosphere. Physical properties of the solutions and vector fields are analyzed and the observational aspects of the model are discussed. The ratio of normal components to the discontinuity Br /Vr can be close to -2. The alignment between velocity and magnetic field vectors takes place. Spacecraft crossing such vortices will typically observe a pair of discontinuities, but with dissimilar properties. Occurrence rate for different discontinuity types is estimated and agrees with observations in high-speed solar wind stream. Discontinuity crossing provides a backward rotation of magnetic field vector and can be observed as part of a backward arc. The Ulysses magnetometer data obtained in the fast solar wind are compared with the results of theoretical modelling.

scholarly journals Magnetic field power spectra and magnetic radial diffusion coefficients using CRRES magnetometer data

2015 ◽  
Vol 120 (2) ◽  
pp. 973-995 ◽  
Author(s):  
Ashar F. Ali ◽  
Scot R. Elkington ◽  
Weichao Tu ◽  
Louis G. Ozeke ◽  
Anthony A. Chan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficients ◽  
Power Spectra ◽  
Radial Diffusion ◽  
Magnetometer Data
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