Distinguishing buried alluvium from till by using detailed total-magnetic-field data

1990 ◽  
Vol 27 (4) ◽  
pp. 513-519
Author(s):  
Erik J. Schwarz
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Power Spectra ◽  
Total Field ◽  
Magnetic Field Data ◽  
Glacial Sediments ◽  
Total Magnetic Field ◽  
River Terraces ◽  
Magnetic Analysis ◽  
Lateral Extent

Total-magnetic-field and vertical-magnetic-gradient profiles are characteristically different over alluvial and glacial sediments. Positive magnetic anomalies elongated in the river-valley direction but not in the structural trend of the underlying bedrock indicate the occurrence of magnetite enrichments within the alluvium. No evidence for such anomalies is found in survey data obtained in gravel pits located in tills. The logarithm of the power of the total-field profiles over the river terraces plotted against spatial frequency is structured, which is indicative of the presence of magnetic sources of certain depth and width. However, the power spectra over till may also show similar features if high-frequency bedrock anomalies are present in the data, so these spectra are not a reliable means of distinguishing between buried alluvium and till. The results show that magnetic analysis allows the discrimination between buried tills and alluvium in which magnetite concentrations of considerable lateral extent were formed.

scholarly journals Analytical Signal and Reduction to Pole Interpretation of Total Magnetic Field Data at Eppawala Phosphate Deposit

2014 ◽  
Vol 02 (03) ◽  
pp. 181-189
Author(s):  
N. D. Subasinghe ◽  
W. K. D. G. D. R. Charles ◽  
S. N. De Silva
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Analytical Signal ◽  
Magnetic Field Data ◽  
Total Magnetic Field ◽  
Phosphate Deposit

scholarly journals Application of magnetic method for mapping buried structures around archaeological site of Masjid Tuha Indrapuri

2020 ◽  
Vol 20 (2) ◽  
pp. 31-35
Author(s):  
CUT INTAN KEUMALA ◽  
TOMI AFRIZAL ◽  
MUHAMMAD SYUKRI SURBAKTI ◽  
NAZLI ISMAIL
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Archaeological Site ◽  
Magnetic Method ◽  
Buried Structures ◽  
Entire Area ◽  
Magnetic Field Data ◽  
Total Magnetic Field ◽  
Aceh Province ◽  
Reduction To The Pole

Magnetic gradiometer survey has been conducted on the yard of the archaeological site of Masjid Tuha Indrapuri, Aceh Besar Regency, Aceh Province. The site is one of the oldest mosques erected during the Aceh Sultanate period. Magnetic method was applied for mapping archaeological structures buried beneath the surface. Total magnetic field data were measured using Proton Precession Magnetometer with grid spacing of 2 meters between stations covering the entire area of the site. Diurnal and international geomagnetic reference field data were corrected to the measured data in order to calculate total magnetic field anomalies that were influenced by the buried magnetic objects. The total magnetic field anomalies distribution shows two elongated structures with U-shaped patterns surrounding the mosque. The patterns are also revealed in reduction to the pole and derivative vertical filters of the total field anomaly data. The anomaly patterns are considered a response from the rest of the buried fences that were built around the mosque in the past.

A TOTAL FIELD MAGNETOMETER FOR MOBILE OPERATION

Geophysics ◽  
1948 ◽  
Vol 13 (2) ◽  
pp. 209-214 ◽  
Author(s):  
Eugene Frowe
Keyword(s):  
Magnetic Field ◽  
High Sensitivity ◽  
Ferromagnetic Material ◽  
Magnetic Data ◽  
Recording Device ◽  
Total Field ◽  
Total Magnetic Field ◽  
Inductive Type ◽  
Continuous Field ◽  
Better Than

A magnetometer which measures the earth’s total magnetic field is described. The detector or measuring element of the magnetometer contains three mutually perpendicular elements, two of which are utilized to orient the third, which in turn operates a recording device to record the total magnetic field. The detector elements are of the inductive type and do not require ferromagnetic material to give them the high sensitivity required in geophysical work. The presence of a magnetic field in the region of the detector causes alternating currents to be generated in the detector elements. These currents are amplified to actuate motors which control the orienting and neutralizing functions of the magnetometer. A tape recorder gives continuous field readings. The accuracy of the magnetic data taken is better than five gammas.

AN AUTOMATIC METHOD OF DIRECT INTERPRETATION OF MAGNETIC PROFILES

Geophysics ◽  
1976 ◽  
Vol 41 (3) ◽  
pp. 531-541 ◽  
Author(s):  
Sudhir Jain
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Thin Sheet ◽  
Thin Sheets ◽  
Automatic Method ◽  
Field Profile ◽  
Total Magnetic Field ◽  
Magnetic Field Profile ◽  
Direct Interpretation ◽  
Susceptibility Contrast

The well‐known equations for the total magnetic field due to thin sheets and the edges of a thick body (Werner, 1953) can be programmed to compute automatically the depth to the top, susceptibility contrast, and the dip of these features from a given total magnetic field profile. The synthetic anomalies show that in ideal cases the depths can be determined to the accuracy of 10 percent or better, provided the source of the anomaly can be identified as a bounding edge or the thin sheet. It has also been found that the anomalies due to edges approximately one depth unit apart in horizontal direction can be resolved. Vertically, the interpretation of shallow bodies is not affected by the presence of deeper bodies. However, the deeper bodies can be located only when they cause anomalies much stronger than those associated with shallow bodies, or when the shallow bodies are displaced from the deep edges horizontally by a distance equal to or greater than the depth to the top of deep edges. The shallow high‐frequency anomalies tend to mask the interpretation of deeper anomalies rather than cause erroneous estimates. Susceptibility contrasts can be estimated reasonably accurately only when the dips are about 40 degrees or greater. The dip estimates are accurate to within 10 percent.

scholarly journals Statistical dependence of auroral ionospheric currents on solar wind and geomagnetic parameters from 5 years of CHAMP satellite data

2009 ◽  
Vol 27 (3) ◽  
pp. 1005-1017 ◽  
Author(s):  
L. Juusola ◽  
K. Kauristie ◽  
O. Amm ◽  
P. Ritter
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Data ◽  
Dynamic Pressure ◽  
Auroral Oval ◽  
Solar Wind Dynamic Pressure ◽  
Total Field ◽  
Magnetic Field Data ◽  
Champ Satellite ◽  
Field Aligned Current

Abstract. The effects of the solar wind dynamic pressure (P), the z component of the solar wind magnetic field (Bz), the merging electric field (Em), season and the Kp index on R1 and R2 field-aligned currents are studied statistically using magnetic field data from the CHAMP satellite during 2001–2005. The ionospheric and field-aligned currents are determined from the magnetic field data by the recently developed 1-D Spherical Elementary Current System (SECS) method. During southward IMF, increasing |Bz| is observed to clearly increase the total field-aligned current, while during northward IMF, the amount of field-aligned current remains fairly constant regardless of |Bz|. The dependence of the field-aligned current on Bz is given by |Ir[MA]|=0.054·Bz[nT]2−0.34·Bz[nT]+2.4. With increasing P, the intensity of the field-aligned current is also found to increase according to |Ir[MA]|=0.62·P[nPa]+1.6, and the auroral oval is observed to move equatorward. Increasing Em produces similar behaviour, described by |Ir[MA]|=1.41·Em[mV/m]+1.4. While the absolute intensity of the ionospheric current is stronger during negative than during positive Bz, the relative change in the intensity of the currents produced by a more intense solar wind dynamic pressure is observed to be approximately the same regardless of the Bz direction. Increasing Kp from 0 to ≥5 widens the auroral oval and moves it equatorward from between 66°–74° AACGM latitude to 59°–71° latitude. The total field aligned current as a function of Kp is given by |Ir[MA]|=1.1·Kp+0.6. In agreement with previous studies, total field-aligned current in the summer is found to be 1.4 times stronger than in the winter.

scholarly journals Identification of magnetosheath mirror modes in Equator-S magnetic field data

1999 ◽  
Vol 17 (12) ◽  
pp. 1560-1573 ◽  
Author(s):  
E. A. Lucek ◽  
M. W. Dunlop ◽  
A. Balogh ◽  
P. Cargill ◽  
W. Baumjohann ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Boundary Layers ◽  
Field Data ◽  
Power Spectra ◽  
Plasma Waves ◽  
Local Times ◽  
Magnetic Shear ◽  
Magnetic Field Data ◽  
Mirror Mode ◽  
Plasma Depletion

Abstract. Between December 1997 and March 1998 Equator-S made a number of excursions into the dawn-side magnetosheath, over a range of local times between 6:00 and 10:40 LT. Clear mirror-like structures, characterised by compressive fluctuations in |B| on occasion lasting for up to 5 h, were observed during a significant fraction of these orbits. During most of these passes the satellite appeared to remain close to the magnetopause (within 1–2 Re), during sustained compressions of the magnetosphere, and so the characteristics of the mirror structures are used as a diagnostic of magnetosheath structure close to the magnetopause during these orbits. It is found that in the majority of cases mirror-like activity persists, undamped, to within a few minutes of the magnetopause, with no observable ramp in |B|, irrespective of the magnetic shear across the boundary. This suggests that any plasma depletion layer is typically of narrow extent or absent at the location of the satellite, at least during the subset of orbits containing strong magnetosheath mirror-mode signatures. Power spectra for the mirror signatures show predominately field aligned power, a well defined shoulder at around 3–10 x 10 –2 Hz and decreasing power at higher frequencies. On occasions the fluctuations are more sinusoidal, leading to peaked spectra instead of a shoulder. In all cases mirror structures are found to lie approximately parallel to the observed magnetopause boundary. There is some indication that the amplitude of the compressional fluctuations tends to be greater closer to the magnetopause. This has not been previously reported in the Earth's magnetosphere, but has been suggested in the case of other planets.Key words. Magnetospheric physics (magnetosheath; plasma waves and instabilities; magnetopause, cusp and boundary layers)

scholarly journals Solar Orbiter/Radio and Plasma Wave observations during the first Venus flyby

2021 ◽  
Author(s):  
Niklas J. T. Edberg ◽  
Lina Hadid ◽  
Milan Maksimovic ◽  
Stuart D. Bale ◽  
Thomas Chust ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Plasma Wave ◽  
Electric Fields ◽  
High Frequency ◽  
Dynamic Environment ◽  
Power Spectra ◽  
Bow Shock ◽  
Double Layers ◽  
Tail Region ◽  
Electric And Magnetic Field

<p>We present measurements from the Radio and Plasma Wave (RPW) instrument suite onboard the Solar Orbiter mission during the first Venus encounter. RPW consists of several units and is capable of measuring both the electric and magnetic field fluctuations with three electric antennas and a search-coil magnetometer: The Low Frequency Receiver (LFR) cover the range from DC up to 10kHz when measuring the electric and magnetic waveform and spectra; the Thermal Noise and High Frequency Receiver (TNR-HFR) determines the electric power spectra and magnetic power spectra from 4kHz-20MHz, and 4kHz to 500kHz, respectively, to determine properties of the electron population; the Time Domain Sampler (TDS) measures and digitizes onboard the electric and magnetic field waveforms from 100 Hz to 250 kHz. The BIAS subunit measures DC and LF electric fields as well as the spacecraft potential, which gives a high cadence measure of the local plasma density when calibrated to the low-cadence tracking of the plasma peak from the TNR. Solar Orbiter approached Venus from the induced magnetotail and had its closest approach at an altitude of 7500 km over the north pole of Venus on 27 Dec 2020. The RPW instruments observed a tail region that extended several 10’s of Venus radii downstream of the planet. The induced magnetosphere was characterized to be a highly dynamic environment as Solar Orbiter traversed the downstream tail and magnetosheath before it crossed the Bow Shock outbound at ~12:40 UT. Polarized whistler waves, high frequency electrostatic waves, narrow-banded emissions, possible electron double layers were observed. The fine structure of the bow shock could also be investigated in detail. Solar Orbiter could hence enhance the knowledge of the structure of the solar wind-Venus interaction.</p>

3-D Analytic Signal in the Interpretation of Total Magnetic Field Data at Low Magnetic Latitudes

1993 ◽  
Vol 24 (3-4) ◽  
pp. 679-687 ◽  
Author(s):  
Ian N. MacLeod ◽  
Keith Jones ◽  
Ting Fan Dai
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Analytic Signal ◽  
Magnetic Field Data ◽  
Total Magnetic Field
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