Science.gov

Sample records for magnetic spreading anomalies

  1. Seafloor spreading in the eastern Gulf of Mexico: New evidence for marine magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Eskamani, Philip K.

    Possible sea-floor spreading anomalies are indentified in marine magnetic surveys conducted in the eastern Gulf of Mexico. A symmetric pattern of lineated anomalies can be correlated with the geomagnetic time scale using previously proposed opening histories for the Gulf of Mexico basin. Lineated magnetic anomalies are characterized by amplitudes of up to 30 nT and wavelengths of 45-55 km, and are correlatable across 12 different ship tracks spanning a combined distance of 6,712 km. The magnetic lineations are orientated in a NW-SE direction with 3 distinct positive lineations on either side of the inferred spreading ridge anomalies. The magnetic anomalies were forward modeled with a 2 km thick magnetic crust composed of vertically bounded blocks of normal and reverse polarity at a model source depth of 10 km. Remnant magnetization intensity and inclination are 1.6 A m-1 and 0.2° respectively, chosen to best fit the magnetic observed amplitudes and, for inclination, in accord with the nearly equatorial position of the Gulf of Mexico during Jurassic seafloor spreading. The current magnetic field is modeled with declination and inclination of and 0.65° and 20° respectively. Using a full seafloor spreading rate of 1.7 cm/yr, the anomalies correlate with magnetic chrons M21 to M10. The inferred spreading direction is consistent with previous suggestions of a North-East to South-West direction of sea-floor spreading off the west coast of Florida beginning 149 Ma (M21) and ending 134 Ma (M10). The opening direction is also consistent with the counter-clockwise rotation of Yucatan proposed in past models.

  2. Contribution of oceanic gabbros to sea-floor spreading magnetic anomalies.

    PubMed

    Kikawa, E; Ozawa, K

    1992-10-30

    The contribution of oceanic gabbros, representative rocks for layer 3 of the oceanic crust, to sea-floor spreading magnetic anomalies has been controversial because of the large variation in magnetic properties. Ocean Drilling Program (ODP) Leg 118 contains a continuous 500.7-meter section of oceanic gabbro that allows the relations between magnetization and petrologic characteristics, such as the degree of metamorphism and the magmatic evolution, to be clarified. The data suggest that oceanic gabbros, together with the effects of metamorphism and of magmatic evolution, account for a significant part of the marine magnetic anomalies.

  3. A New Seafloor Spreading Model of the Red Sea: Magnetic Anomalies and Plate Kinematics

    NASA Astrophysics Data System (ADS)

    Dyment, J.; Tapponnier, P.; Afifi, A. M.; Zinger, M. A.; Franken, D.; Muzaiyen, E.

    2013-12-01

    A high resolution aeromagnetic survey over the Saudi Arabian side of the Red Sea confirms the existence of consistent magnetic anomaly patterns, continuous from 16 to 24°N, and episodic up to 28°N, typical of slow to ultraslow spreading centers. The older Saudi-Sudanese aeromagnetic survey shows that these anomalies are symmetrical between 18 and 23°N. The strong, short-wavelength anomalies over the central trough south of 24°N have long been identified as Chrons 1 to 3 (0-5 Ma). By contrast, the weaker, longer-wavelength anomalies over adjacent sediment-covered areas do not fit standard magnetic anomaly models. The abrupt basement deepening from ~ 1.5 km in the central trough to ~ 5 km beneath the sediments partly accounts for the lower amplitude but not for the lack of short wavelengths. Other spreading centers also lack short-wavelength, high-amplitude magnetic anomalies where covered by thick sediments (Andaman Basin, Juan de Fuca Ridge). We interpret this to reflect the absence of a well-defined layer of pillow lavas, whose emplacement is hampered by rapid, abundant sedimentation. The formation of dykes and sills instead of extrusive lavas results in weaker, less coherent magnetization, generating longer-wavelength anomalies. We test this inference by removing the extrusive basalt contribution from a slow spreading center crustal magnetization model. The computed magnetic anomalies fit well with the shape and amplitude of the anomalies observed in the Red Sea. Two major long-wavelength anomalies are dated at 10-11 Ma (Chron 5) and 14-15 Ma (Chron 5B), implying seafloor spreading back to at least 15 Ma and constraining plate-kinematic reconstructions. Beyond being a key to the geological evolution of the Red Sea, these results emphasize that oceanic crust may exist without clear, short wavelength magnetic anomalies, particularly at the onset of seafloor spreading, when abundant sedimentation may preclude the formation of pillow lavas. The location of many

  4. Magnetic anomaly pattern of the Marsili Basin (southern Tyrrhenian Sea, Italy): Ultrafast oceanic spreading or not?

    NASA Astrophysics Data System (ADS)

    Speranza, F.; Nicolosi, I.; Chiappini, M.

    2011-12-01

    The Marsili Basin is a ~100x70 km flat and deep (3000-3500 m) basin located in the southern Tyrrhenian Sea, encircling the huge 16x50 km (and ~3000 m high) Marsili seamount. Though results from ODP Site 650 had proven more than twenty years ago the oceanic nature of the Marsili Basin, oceanic-type linear magnetic anomalies above the basin floor were clearly documented only in the last few years. Nicolosi et al. (2006) reported on spectral analysis of both airborne and shipborne magnetic maps from the Marsili Basin, and showed the occurrence of six magnetic anomaly stripes covering the flat basin floor, symmetrically arranged with respect to a central positive anomaly located above the Marsili seamount. By assuming that the two 17 km wide lateral normal polarity stripes formed during the Olduvai chron (1.77-1.95 Ma), Nicolosi et al. (2006) suggested that the Marsili Basin opened at the ultrafast full-spreading rate of ~19 cm/yr between 2.1 and 1.6 Ma. They also proposed that the normally magnetized Marsili seamount formed during the Brunhes chron (after 0.78 Ma), when slower spreading (coupled with huge magmatic inflation) resumed, after ~1 Myr of spreading cessation. The spreading model by Nicolosi et al. (2006) has been recently questioned by Cocchi et al. (2009), who argued that filtering had created fictitious anomaly stripes. Cocchi et al. (2009) also gathered new high-resolution shipborne magnetic anomaly data from the Marsili seamount and surrounding basin area. They found two tiny positive magnetic anomaly stripes flanking the Marsili seamount in the north, which they interpreted as due to spreading occurring during the Jaramillo subchron (0.99-1.07 Ma). Consequently, they calculated a post-1.95 Ma initial spreading rate of 3.4 cm/yr (instead of 19 cm/yr), and supported a decreasing yet continuous spreading until Present. Here we discuss the whole magnetic residual evidence from the Marsili Basin. First, we show that magnetic anomaly stripes are also

  5. Early India-Australia Spreading History Revealed by Newly Detected Magnetic Anomalies

    NASA Astrophysics Data System (ADS)

    Williams, S.; Whittaker, J. M.; Granot, R.; Müller, D.

    2013-12-01

    The seafloor within the Perth Abyssal Plain (PAP), offshore Western Australia, is the only section of crust that directly records the early spreading history between India and Australia during the Mesozoic breakup of Gondwana. However, this early spreading has been poorly constrained due to an absence of data, including marine magnetic anomalies and data constraining the crustal nature of key tectonic features. Here, we present new magnetic anomaly data from the PAP that shows that the crust in the western part of the basin was part of the Indian Plate - the conjugate flank to the oceanic crust immediately offshore the Perth margin, Australia. We identify a sequence of M2 and older anomalies in the west PAP within crust that initially moved with the Indian Plate, formed at intermediate half-spreading rates (35 mm/yr) consistent with the conjugate sequence on the Australian Plate. More speculatively, we reinterpret the youngest anomalies in the east PAP, finding that the M0-age crust initially formed on the Indian Plate was transferred to the Australian Plate by a westward jump or propagation of the spreading ridge shortly after M0 time. Samples dredged from the Gulden Draak and Batavia Knolls (at the western edge of the PAP) reveal that these bathymetric features are continental fragments rather than igneous plateaus related to Broken Ridge. These microcontinents rifted away from Australia with Greater India during initial breakup at ~130 Ma, then rifted from India following the cessation of spreading in the PAP (~101-103 Ma).

  6. Investigation of spreading center ecolution by joint inversion of seafloor magnetic anomaly and tectonic fabric data

    NASA Technical Reports Server (NTRS)

    Shoberg, Tom; Stein, Seth

    1994-01-01

    Spreading center segments that have experienced a complex tectonic history including rift propagation may have a complicated signature in bathymetric and magnetic anomaly data. To gain insight into the history of such regions, we have developed techniques in which both the magnetic anomaly patterns and seafloor fabric trends are predicted theoretically, and the combined predictions are compared numerically with the data to estimate best fitting parameters for the propagation history. Fitting functions are constructed to help determine which model best matches the digitized fabric and magnetic anomaly data. Such functions offer statistical criteria for choosing the best fit model. We use this approach to resolve the propagation history of the Cobb Offset along the Juan de Fuca ridge. In this example, the magnetic anomaly data prove more useful in defining the geometry of the propagation events, while the fabric, with its greater temporal resolution, is more useful for constraining the rate of propagation. It thus appears that joint inversion of magnetic and seafloor fabric data can be valuable in tectonic analyses.

  7. Early India-Australia spreading history revealed by newly detected Mesozoic magnetic anomalies in the Perth Abyssal Plain

    NASA Astrophysics Data System (ADS)

    Williams, Simon E.; Whittaker, Joanne M.; Granot, Roi; Müller, Dietmar R.

    2013-07-01

    seafloor within the Perth Abyssal Plain (PAP), offshore Western Australia, is the only section of crust that directly records the early spreading history between India and Australia during the Mesozoic breakup of Gondwana. However, this early spreading has been poorly constrained due to an absence of data, including marine magnetic anomalies and data constraining the crustal nature of key tectonic features. Here, we present new magnetic anomaly data from the PAP that shows that the crust in the western part of the basin was part of the Indian Plate—the conjugate flank to the oceanic crust immediately offshore the Perth margin, Australia. We identify a sequence of M2 and older anomalies in the west PAP within crust that initially moved with the Indian Plate, formed at intermediate half-spreading rates (35 mm/yr) consistent with the conjugate sequence on the Australian Plate. More speculatively, we reinterpret the youngest anomalies in the east PAP, finding that the M0-age crust initially formed on the Indian Plate was transferred to the Australian Plate by a westward jump or propagation of the spreading ridge shortly after M0 time. Samples dredged from the Gulden Draak and Batavia Knolls (at the western edge of the PAP) reveal that these bathymetric features are continental fragments rather than igneous plateaus related to Broken Ridge. These microcontinents rifted away from Australia with Greater India during initial breakup at ~130 Ma, then rifted from India following the cessation of spreading in the PAP (~101-103 Ma).

  8. Magnetic anomalies and seafloor spreading rates in the northern South Atlantic.

    PubMed

    van Andel, T H; Moore, T C

    1970-04-25

    A geomagnetic profile across the northern South Atlantic yields spreading rates for the last 70 m.y. which vary from 1.6 to 2.0 cm/year. There is evidence for three regional discontinuities in the spreading history of the South Atlantic.

  9. Magnetic anomalies. [Magsat studies

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A.

    1983-01-01

    The implications and accuracy of anomaly maps produced using Magsat data on the scalar and vector magnetic field of the earth are discussed. Comparisons have been made between the satellite maps and aeromagnetic survey maps, showing smoother data from the satellite maps and larger anomalies in the aircraft data. The maps are being applied to characterize the structure and tectonics of the underlying regions. Investigations are still needed regarding the directions of magnetization within the crust and to generate further correlations between anomaly features and large scale geological structures. Furthermore, an increased data base is recommended for the Pacific Ocean basin in order to develop a better starting model for Pacific tectonic movements. The Pacific basin was large farther backwards in time and subduction zones surround the basin, thereby causing difficulties for describing the complex break-up scenario for Gondwanaland.

  10. Marine Magnetic Anomalies, Oceanic Crust Magnetization, and Geomagnetic Time Variations

    NASA Astrophysics Data System (ADS)

    Dyment, J.; Arkani-Hamed, J.

    2005-12-01

    Since the classic paper of Vine and Matthews (Nature, 1963), marine magnetic anomalies are commonly used to date the ocean floor through comparison with the geomagnetic polarity time scale and proper identification of reversal sequences. As a consequence, the classical model of rectangular prisms bearing a normal / reversed magnetization has been dominant in the literature for more than 40 years. Although the model explains major characteristics of the sea-surface magnetic anomalies, it is contradicted by (1) recent advances on the geophysical and petrologic structure of the slow-spreading oceanic crust, and (2) the observation of short-term geomagnetic time variations, both of which are more complex than assumed in the classical model. Marine magnetic anomalies may also provide information on the magnetization of the oceanic crust as well as short-term temporal fluctuations of the geomagnetic field. The "anomalous skewness", a residual phase once the anomalies have been reduced to the pole, has been interpreted either in terms of geomagnetic field variations or crustal structure. The spreading-rate dependence of anomalous skewness rules out the geomagnetic hypothesis and supports a spreading-rate dependent magnetic structure of the oceanic crust, with a basaltic layer accounting for most of the anomalies at fast spreading rates and an increasing contribution of the deeper layers with decreasing spreading rate. The slow cooling of the lower crust and uppermost mantle and serpentinization, a low temperature alteration process which produces magnetite, are the likely cause of this contribution, also required to account for satellite magnetic anomalies over oceanic areas. Moreover, the "hook shape" of some sea-surface anomalies favors a time lag in the magnetization acquisition processes between upper and lower magnetic layers: extrusive basalt acquires a thermoremanent magnetization as soon as emplaced, whereas the underlying peridotite and olivine gabbro cool slowly

  11. Magnetic Anomalies in the Enderby Basin, the Southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Nogi, Y.; Sato, T.; Hanyu, T.

    2013-12-01

    Magnetic anomalies in the Southern indian Ocean are vital to understanding initial breakup process of Gondwana. However, seafloor age estimated from magnetic anomalies still remain less well-defined because of the sparse observations in this area. To understand the seafloor spreading history related to the initial breakup process of Gondwana, vector magnetic anomaly data as well as total intensity magnetic anomaly data obtained by the R/V Hakuho-maru and the icebreaker Shirase in the Enderby Basin, Southern Indian Ocean, are used. The strikes of magnetic structures are deduced from the vector magnetic anomalies. Magnetic anomaly signals, most likely indicating Mesozoic magnetic anomaly sequence, are obtained almost parallel to the west of WNW-ESE trending lineaments just to the south of Conrad Rise inferred from satellite gravity anomalies. Most of the strikes of magnetic structures indicate NNE-SSW trends, and are almost perpendicular to the WNW-ESE trending lineaments. Mesozoic sequence magnetic anomalies with mostly WNW-ESE strikes are also observed along the NNE-SSW trending lineaments between the south of the Conrad Rise and Gunnerus Ridge. Magnetic anomalies originated from Cretaceous normal polarity superchron are found in these profiles, although magnetic anomaly C34 has been identified just to the north of the Conrad Rise. However Mesozoic sequence magnetic anomalies are only observed in the west side of the WNW-ESE trending lineaments just to the south of Conrad Rise and not detected to the east of Cretaceous normal superchron signals. These results show that counter part of Mesozoic sequence magnetic anomalies in the south of Conrad Rise would be found in the East Enderby Basin, off East Antarctica. NNE-SSW trending magnetic structures, which are similar to those obtained just to the south of Conrad Rise, are found off East Antarctica in the East Enderby Basin. However, some of the strikes show almost E-W orientations. These suggest complicated ridge

  12. Implications for the South Atlantic early breakup and seafloor spreading from joint interpretation of magnetic anomaly maps and seaward-dipping reflector sequences (SDRS) visible in conjugated reflection seismic sections

    NASA Astrophysics Data System (ADS)

    Schreckenberger, Bernd; Koopmann, Hannes; Franke, Dieter; Schnabel, Michael

    2013-04-01

    The late history of the South Atlantic passive margin evolution is investigated in the view of interlaced magnetic anomalies related to seafloor spreading lineations and anomalies caused by seaward-dipping reflector sequences (SDRS). Our identification of previously unknown pre-M5n lineations in marine magnetic data offshore Argentina now makes the lineation pattern more complete and most importantly comparable and nearly symmetrical to the conjugated area offshore South Africa. Therefore, we can now compare several sets of published South Atlantic reconstruction poles to our new pre-M5n lineations off Argentina and their equivalents off South Africa. The analysis of the symmetry of SDRS and particularly of their along-margin extension further constrains the choice of possible reconstruction poles for the earliest opening phases. The interpretation of pre-M5n lineations also defines the exact time (M9r) of the termination of excess breakup related volcanic activity and the transition to "normal" seafloor spreading. This is compared to absolute radiometric ages from Parana/Etendeka flood basalts. The volcanic activity related to the southernmost volcanic margin segments falls approximately into the same time window as the continental flood basalt activity. Unfortunately, more detailed conclusions suffer seriously from an ongoing discussion about the absolute ages of the pre-M0r lineations in different versions of polarity timescales. New models for the magnetic response of SDRS reveal a high variability within the wedges on either side of the Atlantic and between the conjugated margins. Former identifications of anomaly M11r off Cape Town have already been questioned and can now be shown to be caused by structural or magnetization variations within SDRS.

  13. Magnetic Anomaly Lineations in the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Noguchi, Y.; Nakanishi, M.; Tamaki, K.; Fujimoto, H.; Huchon, P.; Leroy, S.; Styles, P.

    2012-12-01

    We present the magnetic anomaly lineations in the Gulf of Aden to expose the seafloor spreading history. The Gulf of Aden is a young ocean basin formed by the rifting of Arabia Plate away from Somalia Plate. The Arabian plate moves away from Somalia Plate in an NE direction, at a rate of about 2 cm/yr. The rifting started from Oligocene (Bosworth et al., 2005). Seafloor spreading started at about 20 Ma in the eastern part of the Gulf of Aden (Fournier et al., 2010) and propagated westward into the Arabia-Africa continent (Manighetti et al., 1997). It reached the Afar hotspot area about 10 Ma (Audin et al., 2001). The spreading system continues to interact with the hotspot up to the present. Tamsett and Searle (1988) exposed that strike of segmentations of the spreading centers in the Gulf of Aden is NW-SE, although the trend of the spreading system is ENE. We examined magnetic anomaly data collected in the cruises by R/V L'Atalante in 1995 and R/V Hakuho-maru from 2000 to 2001 as well as those collected in other cruises. Elongated negative magnetic anomalies, which amplitude are more than 500 nT, are observed over the spreading centers. Most of the elongated anomalies are parallel with the spreading centers. The elongated magnetic anomalies west of 46 30'E have an E-W trend around the spreading centers. Several discontinuities in the magnetic anomaly contour map illustrate the position of the fracture zones concealed by sediments. Most of magnetic anomaly lineations east of 46 30'E have an N60-65 W strike. Our identification of magnetic anomaly lineations indicates a symmetric seafloor spreading with a spreading rate of about 1.0 cm/yr, although Leroy et al. (2004) showed an asymmetric seafloor spreading of the Sheba Ridge, east of our study area. The kinematics of the Arabia plate changed about 5 Ma, but our results did not show any coeval change in spreading rates of the spreading system in the Gulf of Aden.

  14. Magnetic Anomaly Lineations in the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Noguchi, Y.; Nakanishi, M.; Tamaki, K.; Fujimoto, H.; Huchon, P.; Leroy, S. D.; Styles, P.

    2014-12-01

    We present the magnetic anomaly lineations in the Gulf of Aden. The Gulf of Aden has slow spreading ridges between the Arabia Plate and Somalia Plate. The Arabian plate moves away from Somalia Plate in an NE direction, at a rate of about 2 cm/yr. Previous works indicates that seafloor spreading started about 20 Ma in the eastern part of the Gulf of Aden and propagated westward. The spreading axis has a E-W trend west of 46 E and that east of 46 E has a N60 W trend. We examined magnetic data acquired in the cruises by R/V L'Atalante in 1995, R/V Hakuho-maru from 2000 to 2001, R/V Maurice Ewing in 2001, and Shackleton in 1975 and 1979. We also used data obtained from National Geophysical Data Center, NOAA. We calculated magnetic anomalies using the latest Internation Geomagnetic Reference Field. Elongated negative magnetic anomalies, which amplitude are more than 500 nT, observed over the spreading centers. Most of the elongated anomalies are parallel with the spreading centers. The elongated magnetic anomalies west of 46 30'E have an E-W trend around the spreading centers. Several discontinuities in the magnetic anomaly contour map illustrate the position of the fracture zones concealed by sediments. We identified magnetic lineations from 43 E to 52 E. Most of magnetic lineations west and east of 46 30'E have N-E and N60-65 W strikes, respectively. The oldest lineations are C3r (5.48~5.74 Ma) between 43 10'E and 44 E and C5Ar (12.4~12.7 Ma) east of 44 E. Our identification of magnetic anomaly lineations indicates a symmetric seafloor spreading with a spreading rate of about 1.0 cm/yr, although Leroy et al. (2004) showed an asymmetric seafloor spreading of the Sheba Ridge, east of our study area. The kinematics of the Arabia plate changed about 5 Ma, but our results did not show any coeval change in spreading rates of the spreading system in the Gulf of Aden.

  15. Satellite magnetic anomalies over subduction zones - The Aleutian Arc anomaly

    NASA Technical Reports Server (NTRS)

    Clark, S. C.; Frey, H.; Thomas, H. H.

    1985-01-01

    Positive magnetic anomalies seen in MAGSAT average scalar anomaly data overlying some subduction zones can be explained in terms of the magnetization contrast between the cold subducted oceanic slab and the surrounding hotter, nonmagnetic mantle. Three-dimensional modeling studies show that peak anomaly amplitude and location depend on slab length and dip. A model for the Aleutian Arc anomaly matches the general trend of the observed MAGSAT anomaly if a slab thickness of 7 km and a relatively high (induced plus viscous) magnetization contrast of 4 A/m are used. A second source body along the present day continental margin is required to match the observed anomaly in detail, and may be modeled as a relic slab from subduction prior to 60 m.y. ago.

  16. Spreading rate dependence of gravity anomalies along oceanic transform faults.

    PubMed

    Gregg, Patricia M; Lin, Jian; Behn, Mark D; Montési, Laurent G J

    2007-07-12

    Mid-ocean ridge morphology and crustal accretion are known to depend on the spreading rate of the ridge. Slow-spreading mid-ocean-ridge segments exhibit significant crustal thinning towards transform and non-transform offsets, which is thought to arise from a three-dimensional process of buoyant mantle upwelling and melt migration focused beneath the centres of ridge segments. In contrast, fast-spreading mid-ocean ridges are characterized by smaller, segment-scale variations in crustal thickness, which reflect more uniform mantle upwelling beneath the ridge axis. Here we present a systematic study of the residual mantle Bouguer gravity anomaly of 19 oceanic transform faults that reveals a strong correlation between gravity signature and spreading rate. Previous studies have shown that slow-slipping transform faults are marked by more positive gravity anomalies than their adjacent ridge segments, but our analysis reveals that intermediate and fast-slipping transform faults exhibit more negative gravity anomalies than their adjacent ridge segments. This finding indicates that there is a mass deficit at intermediate- and fast-slipping transform faults, which could reflect increased rock porosity, serpentinization of mantle peridotite, and/or crustal thickening. The most negative anomalies correspond to topographic highs flanking the transform faults, rather than to transform troughs (where deformation is probably focused and porosity and alteration are expected to be greatest), indicating that crustal thickening could be an important contributor to the negative gravity anomalies observed. This finding in turn suggests that three-dimensional magma accretion may occur near intermediate- and fast-slipping transform faults.

  17. Interpretation of magnetic anomalies over the Grenada Basin

    NASA Astrophysics Data System (ADS)

    Bird, Dale E.; Hall, Stuart A.; Casey, John F.; Millegan, Patrick S.

    1993-10-01

    The Grenada Basin is a back arc basin located near the eastern border of the Caribbean Plate. The basin is bounded on the west by the north-south trending Aves Ridge (a remnant island arc) and on the east by the active Lesser Antilles island arc. Although this physiography suggests that east-west extension formed the basin, magnetic anomalies over the basin exhibit predominantly east-west trends. If the observed magnetic anomalies over the basin are produced by seafloor spreading, then the orientation of extension is complex. Extension in back arc basins is roughly normal to the trench, although some basins exhibit oblique extension. Present models for the formation of the Grenada Basin vary from north-south extension through northeast-southwest extension to east-west extension. An interpretation of magnetic anomalies over the Grenada Basin supports basin development by nearly east-west extension. Low amplitude magnetic anomaly trends subparallel to the island arc magnetic anomaly trends over the southern part of the basin and the results of forward three-dimensional (3-D) magnetic modeling are consistent with this conclusion. Late Cenozoic tectonic movements may have been responsible for disrupting the magnetic signature over the northern part of the basin. On the basis of our 3-D analysis, we attribute the prominent east-west trending anomalies of the Grenada Basin to fracture zones formed during seafloor spreading at low latitude. This east-west trend is not interpreted as indicating north-south extension of the basin.

  18. Spectral Methods for Magnetic Anomalies

    NASA Astrophysics Data System (ADS)

    Parker, R. L.; Gee, J. S.

    2013-12-01

    Spectral methods, that is, those based in the Fourier transform, have long been employed in the analysis of magnetic anomalies. For example, Schouten and MaCamy's Earth filter is used extensively to map patterns to the pole, and Parker's Fourier transform series facilitates forward modeling and provides an efficient algorithm for inversion of profiles and surveys. From a different, and perhaps less familiar perspective, magnetic anomalies can be represented as the realization of a stationary stochastic process and then statistical theory can be brought to bear. It is vital to incorporate the full 2-D power spectrum, even when discussing profile data. For example, early analysis of long profiles failed to discover the small-wavenumber peak in the power spectrum predicted by one-dimensional theory. The long-wavelength excess is the result of spatial aliasing, when energy leaks into the along-track spectrum from the cross-track components of the 2-D spectrum. Spectral techniques may be used to improve interpolation and downward continuation of survey data. They can also evaluate the reliability of sub-track magnetization models both across and and along strike. Along-strike profiles turn out to be surprisingly good indicators of the magnetization directly under them; there is high coherence between the magnetic anomaly and the magnetization over a wide band. In contrast, coherence is weak at long wavelengths on across-strike lines, which is naturally the favored orientation for most studies. When vector (or multiple level) measurements are available, cross-spectral analysis can reveal the wavenumber interval where the geophysical signal resides, and where noise dominates. One powerful diagnostic is that the phase spectrum between the vertical and along-path components of the field must be constant 90 degrees. To illustrate, it was found that on some very long Project Magnetic lines, only the lowest 10% of the wavenumber band contain useful geophysical signal. In this

  19. Northern east Pacific rise: Magnetic anomaly and bathymetric framework

    SciTech Connect

    Klitgord, K.D.; Mammerickx, J.

    1982-08-10

    The oceanic crust in the eastern Pacific between 7/sup 0/N and 30/sup 0/N and east of 127/sup 0/W contains a fairly complete history of the spreading centers associated with the East Pacific Rise since 25 m.y. B.P. (late Oligocene). In this paper, we have summarized the seafloor spreading magnetic-anomaly data and the bathymetric data that reflect the record of this technique history. The well-defined magnetic lineations north of the Clarion fracture zone, in the mouth of the Gulf of California, and on the east flank of the East Pacific Rise (EPR) are carefully examined and used to provide a guide for interpreting the spreading pattern between the Clarion and Clipperton fracture zones, southward of the Rivera fracture zone over the Mathematician Ridge, and over the entire EPR east of the Mathematician Ridge between the Rivera and Siqueiros fracture zones. The bathymetric data provide a trace of the fracture zone pattern in each of the above mentioned areas. The fracture zone bathymetry and the seafloor spreading magnetc lineations on the EPR south of the Rivera fracture zone have a distinctive fanning pattern caused by close poles of rotation and plate boundary reorganizations. All these data provide a good record of the plate reorganizations in the middle Miocene at magnetic anomaly 5A time (12.5 to 11 m.y. B.P.), in the late Miocene at a magnetic anomaly 3'--4 time (6.5 m.y. B.P.), and in the Pliocene at magnetic anomaly 2'--3 time (3.5 m.y.B.P.). Several abandoned spreading centers, including the Mathematician Ridge, were left behind as a result of these reorganizations. The Mathematician Ridge is shown to be a set of ridges and trough whose origin is related to the tectonics activity associated with each of the above mentioned reorganizations since anomaly 5A.

  20. Regional magnetic anomaly constraints on continental rifting

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Radially polarized MAGSAT anomalies of North and South America, Europe, Africa, India, Australia and Antarctica demonstrate remarkably detailed correlation of regional magnetic lithospheric sources across rifted margins when plotted on a reconstruction of Pangea. These major magnetic features apparently preserve their integrity until a superimposed metamorphoric event alters the magnitude and pattern of the anomalies. The longevity of continental scale magnetic anomalies contrasts markedly with that of regional gravity anomalies which tend to reflect predominantly isostatic adjustments associated with neo-tectonism. First observed as a result of NASA's magnetic satellite programs, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans. Accordingly, satellite magnetic observations provide a further tool for investigating continental drift to compliment other lines of evidence in paleoclimatology, paleontology, paleomagnetism, and studies of the radiometric ages and geometric fit of the continents.

  1. The source of marine magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Harrison, Christopher G. A.

    1987-01-01

    The Vine-Matthews hypothesis (1963) is examined. This hypothesis suggests that oceanic rocks become polarized in the direction of the magnetic field at the time of their formation, thus recording the polarity history of the earth's magnetic field. This produces the lineated magnetic anomalies on either side of the midoceanic ridge crests. The strength of these magnetic anomalies is studied to determine the strength of magnetization. Indirect determinations of the magnetization intensity of the oceanic crust and direct observations of the oceanic crust are compared. It is found that the average magnetization of a 6-km thick oceanic crust is 1.18 A/m.

  2. Magnetic and gravity anomalies in the Americas

    NASA Technical Reports Server (NTRS)

    Braile, L. W.; Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator)

    1981-01-01

    The cleaning and magnetic tape storage of spherical Earth processing programs are reported. These programs include: NVERTSM which inverts total or vector magnetic anomaly data on a distribution of point dipoles in spherical coordinates; SMFLD which utilizes output from NVERTSM to compute total or vector magnetic anomaly fields for a distribution of point dipoles in spherical coordinates; NVERTG; and GFLD. Abstracts are presented for papers dealing with the mapping and modeling of magnetic and gravity anomalies, and with the verification of crustal components in satellite data.

  3. The magnetic anomaly of the Ivreazone

    NASA Technical Reports Server (NTRS)

    Albert, G.

    1979-01-01

    A magnetic field survey was made in the Ivreazone in 1969/70. The results were: significant anomaly of the vertical intensity is found. It follows the basic main part of the Ivrea-Verbano zone and continues to the south. The width of the anomaly is about 10 km, the maximum measures about +800 gamma. The model interpretation shows that possibly the anomaly belongs to an amphibolitic body, which in connection with the Ivrea-body was found by deep seismic sounding. Therefore, the magnetic anomaly provides further evidence for the conception that the Ivrea-body has to be regarded as a chip of earthmantle material pushed upward by tectonic processes.

  4. Marine Magnetic Anomalies and the Reconstruction of the World

    NASA Technical Reports Server (NTRS)

    Heirtzler, James R.; Smith, David E. (Technical Monitor)

    2000-01-01

    Until the middle of the 20th century little was known about magnetic anomalies in the oceans. Then it was discovered that there are relatively large anomalies in most of the oceans and they were unrelated to any geological structure known at that time. In the early 1950's large anomalies had been found over the Mid-Atlantic Ridge, and linear anomalies over the eastern continental shelf of North America and, shortly after that, off the west coast. A survey of the ridge south of Iceland showed that the anomalies were linear, parallel to the ridge axis, and symmetrical about the axis. Using the theory that the anomalies were caused by geomagnetic field reversals and seafloor spreading it was possible to greatly extend the time scale of geomagnetic reversals, to determine the velocity of seafloor spreading and estimate the time of opening of the North Atlantic. Lamont had a world-wide collection of marine magnetic profiles. These were used, systematically, to determine the positions of most of the land masses of the world since the beginnings of the world's present oceans.

  5. Reduction of satellite magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Slud, E. V.; Smith, P. J.; Langel, R. A.

    1984-01-01

    Analysis of global magnetic anomaly maps derived from satellite data is facilitated by inversion to the equivalent magnetization in a constant thickness magnetic crust or, equivalently, by reduction to the pole. Previous inversions have proven unstable near the geomagnetic equator. The instability results from magnetic moment distributions which are admissible in the inversion solution but which make only small contribution to the computed values of anomaly field. Their admissibility in the solution could result from noisy or incomplete data or from small poorly resolved anomalies. The resulting magnetic moments are unrealistically large and oscillatory. Application of the method of principal components (e.g. eigenvalue decomposition and selective elimination of less significant eigenvectors) is proposed as a way of overcoming the instability and the method is demonstrated by applying it to the region around the Bangui anomaly in Central Africa.

  6. Sources of Near Side Lunar Magnetic Anomalies

    NASA Technical Reports Server (NTRS)

    Richmond, Nicola C.; Hood, Lon L.; Halekas, J. S.; Mitchell, D. L.; Lin, R. P.; Acuna, M. H.; Binder, A.B.

    2002-01-01

    Lunar Prospector magnetometer data has been used to identify a number of nearside magnetic anomalies. Some of the features identified appear to correlate with impact ejecta, supporting a basin ejecta origin to the nearside anomalies. Additional information is contained in the original extended abstract.

  7. Understanding Magnetic Anomalies and Their Significance.

    ERIC Educational Resources Information Center

    Shea, James H.

    1988-01-01

    Describes a laboratory exercise testing the Vine-Matthews-Morley hypothesis of plate tectonics. Includes 14 questions with explanations using graphs and charts. Provides a historical account of the current plate tectonic and magnetic anomaly theory. (MVL)

  8. Interpretation of satellite elevation magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A.; Carle, H. M.; Hayling, K. L.

    1986-01-01

    The present discussion is based on a study of the magnetic field data obtained with the aid of the magnetic field satellite Magsat, deployed in October 1979, over most of the earth during a 7.5-month mission. Inversions using spherical harmonic coefficients are considered along with the inversion of residual fields. In order to perform the correct operation, it is necessary to add on to the source function produced by the inversion process a magnetization function which has no external field. Such a function is known as an annihilator. The use of the annihilator for Pacific Ocean anomalies is discussed. Attention is given to models of oceanic crustal magnetization, and continental long-wavelength anomalies. It is found that in continental regions the annihilator is also useful if induced magnetizations are thought to be responsible for the long-wavelength anomaly.

  9. The mineralogy of global magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E. (Principal Investigator)

    1984-01-01

    Experimental and analytical data on magnetic mineralogy was provided as an aid to the interpretation of magnetic anomaly maps. An integrated program, ranging from the chemistry of materials from 100 or more km depth within the Earth, to an examination of the MAGSAT anomaly maps at about 400 km above the Earth's surface, was undertaken. Within this framework, a detailed picture of the pertinent mineralogical and magnetic relationships for the region of West Africa was provided. Efforts were directed toward: (1) examining the geochemistry, mineralogy, magnetic properties, and phases relations of magnetic oxides and metal alloys in rocks demonstrated to have originated in the lower crust of upper mantle, (2) examining the assumption that these rocks portray the nature of their source regions; and (3) examining the regional geology, tectonics, gravity field and the MAGSAT anomaly maps for West Africa.

  10. Magnetic Anomalies in the South of Corad Rise, the Southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Nogi, Y.; Ikehara, M.; Nakamura, Y.; Kameo, K.; Katsuki, K.; Kawamura, S.; Kita, S.

    2008-12-01

    Seafloor age estimated from magnetic anomalies in the Southern Indian Ocean are vital to understanding the fragmentation process of the Gondwana, but the seafloor age still remain less well-defined because of the sparse observations in this area. To understand the seafloor spreading history related to the Gondwana breakup, total intensity and vector geomagnetic field measurements as well as swath bathymetry mapping were conducted during the R/V Hakuho-maru cruise KH-07-4 Leg3 in the Southern Indian Ocean between Cape Town, South Africa, and off Lützow-Holm Bay, Antarctica. Magnetic anomaly data have been collected along WNW-ESE trending structures of unknown origin inferred from satellite gravity anomalies just to the south of Conrad Rise. We have also collected magnetic anomaly data along NNE-SSW trending lineaments from satellite gravity anomaly data between the south of the Conrad Rise and off Lützow-Holm Bay. Magnetic anomalies with amplitude of about 500 nT, originating from normal and reversed magnetization of oceanic crust, are detected along the WNW-ESE trending structures just to the south of Conrad Rise. These magnetic anomalies possibly belong to Mesozoic magnetic anomaly sequence and this shows the part of the oceanic crust just to the south of the Conrad Rise formed before the long Cretaceous normal polarity superchron although magnetic anomaly C34 has been identified just to the north of the Conrad Rise. Magnetic anomalies with amplitude of about 300 nT are also observed along the NNE-SSW trending lineaments between the south of the Conrad Rise and off Lützow-Holm Bay, and most likely indicate Mesozoic magnetic anomaly sequence. These suggest the extinct spreading axes in the south of Conrad Rise and complicated seafloor spreading history in this area.

  11. Continental magnetic anomaly constraints on continental reconstruction

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Crustal magnetic anomalies mapped by the MAGSAT satellite for North and South America, Europe, Africa, India, Australia and Antarctica and adjacent marine areas were adjusted to a common elevation of 400 km and differentially reduced to the radial pole of intensity 60,000 nT. These radially polarized anomalies are normalized for differential inclination, declination and intensity effects of the geomagnetic field, so that in principle they directly reflected the geometric and magnetic polarization attributes of sources which include regional petrologic variations of the crust and upper mantle, and crustal thickness and thermal perturbations. Continental anomalies demonstrate remarkably detailed correlation of regional magnetic sources across rifted margins when plotted on a reconstruction of Pangea. Accordingly, they suggest further fundamental constraints on the geologic evolution of the continents and their reconstructions.

  12. CHAMP Magnetic Anomalies of the Antarctic Crust

    NASA Technical Reports Server (NTRS)

    Kim, Hyung Rae; Gaya-Pique, Luis R.; vonFrese, Ralph R. B.; Taylor, Patrick T.; Kim, Jeong Woo

    2003-01-01

    Regional magnetic signals of the crust are strongly masked by the core field and its secular variations components and hence difficult to isolate in the satellite measurements. In particular, the un-modeled effects of the strong auroral external fields and the complicated- behavior of the core field near the geomagnetic poles conspire to greatly reduce the crustal magnetic signal-to-noise ratio in the polar regions relative to the rest of the Earth. We can, however, use spectral correlation theory to filter the static lithospheric and core field components from the dynamic external field effects. To help isolate regional lithospheric from core field components, the correlations between CHAMP magnetic anomalies and the pseudo magnetic effects inferred from gravity-derived crustal thickness variations can also be exploited.. Employing these procedures, we processed the CHAMP magnetic observations for an improved magnetic anomaly map of the Antarctic crust. Relative to the much higher altitude Orsted and noisier Magsat observations, the CHAMP magnetic anomalies at 400 km altitude reveal new details on the effects of intracrustal magnetic features and crustal thickness variations of the Antarctic.

  13. Central anomaly magnetization high: constraints on the volcanic construction and architecture of seismic layer 2A at a fast-spreading mid-ocean ridge, the EPR at 9°30'-50'N

    NASA Astrophysics Data System (ADS)

    Schouten, Hans; Tivey, Maurice A.; Fornari, Daniel J.; Cochran, James R.

    1999-05-01

    The central anomaly magnetization high (CAMH) is a zone of high crustal magnetization centered on the axis of the East Pacific Rise (EPR) and many other segments of the global mid-ocean ridge (MOR). The CAMH is thought to reflect the presence of recently emplaced and highly magnetic lavas. Forward models show that the complicated character of the near-bottom CAMH can be successfully reproduced by the convolution of a lava deposition distribution with a lava magnetization function that describes the variation in lava magnetization intensity with age. This lava magnetization function is the product of geomagnetic paleofield intensity, which has increased by a factor of 2 over the last 40 kyr, and low-temperature alteration which decreases the remanence of lava with exposure to seawater. The success of the forward modeling justifies the inverse approach: deconvolution of the magnetic data for lava distribution and integration of that distribution for magnetic layer thickness. This approach is tested on two near-bottom magnetic profiles AL2767 and AL2771, collected using Alvin across the EPR axis at 9°31'N and 9°50'N. Our analysis of these data produces an estimate of the relative thickness of the magnetic lava layer which is remarkably consistent with existing multichannel estimates of layer 2A thickness from lines CDP31 and CDP27. The similarity between magnetic layer and seismic layer 2A at the 9°-10°N segment of the EPR crest provides independent support to the notion that seismic layer 2A in young oceanic crust represents the highly magnetic lava layer, and that the velocity gradient at the base of layer 2A is related to the increasing number of higher-velocity dikes with depth in the lava-dike transition zone. The near-bottom magnetic anomaly character of the CAMH is a powerful indicator of the emplacement history of upper crust at MORs which allows prediction of the relative thickness and architecture of the extrusive lavas independent of other constraints.

  14. An approach for estimating the magnetization direction of magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Li, Jinpeng; Zhang, Yingtang; Yin, Gang; Fan, Hongbo; Li, Zhining

    2017-02-01

    An approach for estimating the magnetization direction of magnetic anomalies in the presence of remanent magnetization through correlation between normalized source strength (NSS) and reduced-to-the-pole (RTP) is proposed. The observation region was divided into several calculation areas and the RTP field was transformed using different assumed values of the magnetization directions. Following this, the cross-correlation between NSS and RTP field was calculated, and it was found that the correct magnetization direction was that corresponding to the maximum cross-correlation value. The approach was tested on both simulated and real magnetic data. The results showed that the approach was effective in a variety of situations and considerably reduced the effect of remanent magnetization. Thus, the method using NSS and RTP is more effective compared to other methods such as using the total magnitude anomaly and RTP.

  15. Lunar magnetic anomalies and the Cayley formation

    NASA Technical Reports Server (NTRS)

    Strangway, D. W.; Gose, W. A.; Pearce, G. W.; Mcconnell, R. K.

    1973-01-01

    It is proposed that magnetic anomalies such as found at the Apollo 16 site are associated with breccia flows which cooled in place from above 770 C. The required field at the time that this process took place is a few thousand gamma. It is suggested that the surface and orbital magnetic anomalies are caused by basins filled with Cayley-like breccia flows to a thickness of the order of a kilometer. These breccia blankets settled in place from temperatures above 770 C and a thickness on the order of 1 km was welded to a level of 2 to 4 on Warner's scale. A base surge caused by impact or by a volcanic event could be the mechanism by which these breccia blankets were deposited.

  16. Band Iron Formations and Satellite Magnetic Anomalies

    NASA Astrophysics Data System (ADS)

    Nazarova, K. A.; Wasilewski, P.

    2005-05-01

    Band Iron Formations (BIF) are mainly Precambrian (2.5-1.8 Ga) sedimentary deposits and are composed of alternating layers of iron rich material and silica (chert). Precambrian BIF mark growth in the level of free oxygen in the atmosphere and the ocean which happened about 2.2 Ga. Distribution of main BIF includes Hamersley Range, Australia; Transvaal-Griquatown, South Africa; Minas Gerais, Brazil; Labrador Trough, Canada, and Kursk-Krivoi Rog (Russia). Together these five very large BIF deposits constitute about 90 percent of Earth's total estimated BIF (5.76*10 14 ). On each continent these ancient rocks usually metamorphosed and crystallized include what are variously described as hematite-quartzites, banded iron formations, banded jaspers or calico-rocks. West African, Hudson Bay and Western Australian Satellite Magnetic Anomalies coincide with distribution BIF deposits. The Kursk Satellite Magnetic Anomaly (KMA) (about 22 nT at the altitude=400km, centered at 51o N, 37o E) also was identified by ground and aeromagnetic observations and is recognized as one of the largest magnetic anomaly on the Earth. Magnetic modeling shows that immense Precambrian iron ore deposits (iron bands) of Voronezh uplift are the main source of KMA. Magnetic properties of 10000 BIF samples outcropped in the KMA area have been measured and analyzed (Krutikhovskaya et al., 1964) Rockmag BIF dataset is presented at: http://core2.gsfc.nasa.gov/MPDB/datasets.html. Mean NRM value is about 42 A/M, Qn about 1.4. Demagnetization tests suggest that hard and stable NRM component is caused by hematite occurring in BIF in different forms and grain sizes. Hematite deposits discovered on Mars in western equatorial area with layered topography of Aram Chaos and Sinus Meridiani could be of hydrothermal origin and may be formed similar to hematite precipitated in BIF on Earth.

  17. Magnetic anomalies northeast of Cape Adare, northern Victoria Land (Antarctica), and their relation to onshore structures

    USGS Publications Warehouse

    Damaske, D.; Läufer, A.L.; Goldmann, F.; Möller, H.-D.; Lisker, F.

    2007-01-01

    An aeromagnetic survey was flown over the offshore region northeast of Cape Adare and the magnetic anomalies compared to onshore structures between Pennell Coast and Tucker Glacier. The magnetic anomalies show two nearly orthogonal major trends. NNW-SSE trending anomalies northeast of Cape Adare represent seafloor spreading within the Adare Trough. A connection of these anomalies to the Northern Basin of the Ross Sea is not clear. Onshore faults are closely aligned to offshore anomalies. Main trends are NW-SE to NNW-SSE and NE-SW to NNESSW. NNW-SSE oriented dextral-transtensional to extensional faults parallel the Adare Peninsula and Adare Trough anomalies. NE-SW trending normal faults appear to segment the main Hallett volcanic bodies.

  18. Paleo-Pole Positions from Martian Magnetic Anomaly Data

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.; Frawley, James J.

    2003-01-01

    Magnetic component anomaly maps were made from five mapping cycles of the Mars Global Surveyor s magnetometer data. Our goal was to find and isolate positive and negative anomaly pairs which would indicate magnetization of a single source body. From these anomalies we could compute the direction of the magnetizing vector and subsequently the location of the magnetic pole existing at the time of magnetization. We found nine suitable anomaly pairs and from these we computed four North and 3 South poles with two at approximately 60 degrees north latitude. These results suggest that during the existence of the Martian main magnetic field it experienced several reversals.

  19. Paleo-Pole Positions from Martian Magnetic Anomaly Data

    NASA Technical Reports Server (NTRS)

    Frawley, James J.; Taylor, Patrick T.

    2004-01-01

    Magnetic component anomaly maps were made from five mapping cycles of the Mars Global Surveyor's magnetometer data. Our goal was to find and isolate positive and negative anomaly pairs which would indicate magnetization of a single source body. From these anomalies we could compute the direction of the magnetizing vector and subsequently the location of the magnetic pole existing at the time of magnetization. We found nine suitable anomaly pairs and from these we computed paleo-poles that were nearly equally divided between north, south and mid-latitudes. These results suggest that during the existence of the martian main magnetic field it experienced several reversals and excursions.

  20. Crustal Magnetic Field Anomalies and Global Tectonics

    NASA Astrophysics Data System (ADS)

    Storetvedt, Karsten

    2014-05-01

    A wide variety of evidence suggests that the ruling isochron (geomagnetic polarity versus age) hypothesis of marine magnetic lineations has no merit - undermining therefore one of the central tenets of plate tectonics. Instead, variable induction by the ambient geomagnetic field is likely to be the principal agent for mega-scale crustal magnetic features - in both oceanic and continental settings. This revitalizes the fault-controlled susceptibility-contrast model of marine magnetic lineations, originally proposed in the late 1960s. Thus, the marine magnetic 'striping' may be ascribed to tectonic shearing and related, but variable, disintegration of the original iron-oxide mineralogy, having developed primarily along one of the two pan-global sets of orthogonal fractures and faults. In this way, fault zones (having the more advanced mineral alteration) would be characterized by relatively low susceptibility, while more moderately affected crustal sections (located between principal fault zones) would be likely to have less altered oxide mineralogy and therefore higher magnetic susceptibility. On this basis, induction by the present geomagnetic field is likely to produce oscillating magnetic field anomalies with axis along the principal shear grain. The modus operandi of the alternative magneto-tectonic interpretation is inertia-driven wrenching of the global Alpine age palaeo-lithosphere - triggered by changes in Earth's rotation. Increasing sub-crustal loss to the upper mantle during the Upper Mesozoic had left the ensuing Alpine Earth in a tectonically unstable state. Thus, sub-crustal eclogitization and associated gravity-driven delamination to the upper mantle led to a certain degree of planetary acceleration which in turn gave rise to latitude-dependent, westward inertial wrenching of the global palaeo-lithosphere. During this process, 1) the thin and mechanically fragile oceanic crust were deformed into a new type of broad fold belts, and 2) the continents

  1. Mesozoic Sequence Magnetic Anomalies in the South of Corad Rise, the Southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Nogi, Y.; Ikehara, M.; Nakamura, Y.; Kameo, K.; Katsuki, K.; Kawamura, S.; Kita, S.

    2009-04-01

    The Southern Indian Ocean is key area for understanding the fragmentation process of the Gondwana. However, tectonic history in the Southern Indian Ocean still remains less well-defined because of the sparse observations in this area. The R/V Hakuho-maru cruise KH-07-4 Leg3 were conducted to understand the tectonic history related to the Gondwana breakup in the Southern Indian Ocean between Cape Town, South Africa, and off Lutzow-Holm Bay, Antarctica. Total intensity and vector geomagnetic field measurements as well as swath bathymetry mapping were collected during the cruise. Magnetic anomaly data have been collected along WNW-ESE trending inferred from satellite gravity anomalies just to the south of Conrad Rise. We have also collected magnetic anomaly data along NNE-SSW trending lineaments from satellite gravity anomaly data between the south of the Conrad Rise and off Lutzow-Holm Bay. Magnetic anomalies with amplitude of about 500 nT, originating from normal and reversed magnetization of oceanic crust are detected along the WNW-ESE trending structures just to the south of Conrad Rise. Those magnetic anomalies most likely indicate Mesozoic magnetic anomaly sequence, Mesozoic sequence magnetic anomalies with amplitude of about 300 nT are also observed along the NNE-SSW trending lineaments between the south of the Conrad Rise and off Lutzow-Holm Bay. Oceanic crusts formed during Cretaceous normal polarity superchron are found in both profiles, although magnetic anomaly C34 has been identified just to the north of the Conrad Rise. These suggest the extinct spreading axes in the south of Conrad Rise and the two different seafloor spreading systems were active around Cretaceous normal polarity superchron between the south of the Conrad Rise and off Lutzow-Holm Bay. These provide new constraints for the fragmentation process of the Gondwana.

  2. Remanent magnetization model for the broken ridge satellite magnetic anomaly

    NASA Technical Reports Server (NTRS)

    Johnson, B. D.

    1983-01-01

    A crustal model for the interpretation of the Broken Ridge satellite magnetic anomaly was constructed from bathymetric data assuming an Airy-type isostatic compensation. An average crustal magnetization of 6 A.m is required to account for the observed anomaly amplitudes provided that the whole crust is homogeneously magnetized. In contrast, a model representing only the topographic expression of the Broken Ridge, above the surrounding sea floor, requires a magnetization of the order of 40 A.m-1. Since this latter figure is much higher than is to be expected from studies of magnetic properties of oceanic rocks, it is concluded that the majority of the crustal volume of Broken Ridge is magnetized relatively uniformly. The direction of the source magnetization is consistent with an inclination shallower than the present geomagnetic field and close to that of an axial dipole. Since a more northerly source location for Broken Ridge is contrary to the paleolatitude data it is though that the magnetization represents a magnetization obtained by averaging the geomagnetic field direction over a sufficient time to remove secular variation effects. This pattern is indicative of viscous magnetization.

  3. Marine magnetic anomalies - The origin of the stripes

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A.

    1987-01-01

    The results of recent observational and theoretical investigations of lineated magnetic anomalies on the ocean floor are summarized in tables, graphs, and diagrams and analyzed. Topics addressed include early lineation models, inversions of magnetic anomalies to obtain source functions, deep-tow studies of magnetic anomalies, evidence from the long-wavelength component of the magnetic field (including Magsat observations), and direct measurements of the magnetic properties of oceanic rocks. It is concluded that the source of the lineated anomalies must reside in most of the oceanic crust, not just in the pillow lavas of layer 2A.

  4. Magnetic resonance imaging of fetal developmental anomalies.

    PubMed

    Girard, Nadine J

    2011-02-01

    Fetal developmental anomalies consist of central nervous system malformations, brain injury, and tumors. Overlap is often seen especially between malformation and injury because malformation may be genetically determined or related to external causative agent, whereas brain injury may be, on one hand, caused by malformation as with intracranial vascular malformation and, on another, can cause brain malformation when cerebral insult occurs during organogenesis and histogenesis. The goal of this review was not to describe by magnetic resonance imaging (MRI) all fetal developmental anomalies encountered in utero; it is most likely to focus on fetal brain anomalies that either are most commonly seen in fetal tertiary care facility or are extremely challenging for MRI. Consequently, the potential of advanced MR techniques such as proton MR spectroscopy and diffusion tensor imaging is also described especially when a challenge is highlighted. This review is therefore organized in subchapters as follows. The first section gives the place of MRI in prenatal development and cites the standard protocol and the advanced techniques. The rules of fetal brain MRI, the challenge and pitfalls, and the selection of MRI cases follow as 3 subchapters. Also, abnormalities are described as 3 separate subchapters entitled ventriculomegalies (hydrocephalus), malformations, and brain injury.

  5. Leveraging Somali Basin Magnetic Anomalies to Constrain Gondwana Breakup and Early Indian Ocean Formation

    NASA Astrophysics Data System (ADS)

    Davis, J. K.; Lawver, L. A.; Norton, I. O.; Gahagan, L.

    2015-12-01

    The Somali Basin, found between the Horn of Africa and Madagascar was formed during the rifting of East and West Gondwana. Understanding the evolution of the basin has historically been hindered by enigmatic seafloor fabric and an apparent paucity of magnetic anomaly data. Recent iterations of satellite gravity data have revealed nearly complete fracture zones as well as a distinct extinct spreading ridge within the basin. Through a thorough compilation of available Somali Basin shiptrack profiles, we have been able to successfully model and interpret magnetic anomalies with exceptional detail. This complication is unrivaled in completeness and provides unprecedented insight into basin formation. Using this high quality data, we have interpreted magnetic anomalies M0r (120.8 Ma) to M24Bn (152.43 Ma) about the extinct ridge. The interpreted Somali Basin spreading rate and spreading direction, through anomaly M15n (135.76 Ma), are similar to those observed in the neighboring coeval Mozambique Basin. This similarity suggests that East Gondwana separated from West Gondwana as a cohesive unit, and that the internal rifting of East Gondwana began later around 135 Ma. Our magnetic anomaly interpretations have been combined with additional magnetic interpretations from around the Indian Ocean to build a regionally consistent plate model of Gondwana breakup and early Indian Ocean formation. This plate model will be crucial for future efforts unraveling a precise history of East Gondwana fragmentation and constraining the formation of the Enderby Basin offshore East Antarctica and Bay of Bengal offshore East India.

  6. A global magnetic anomaly map. [obtained from POGO satellite data

    NASA Technical Reports Server (NTRS)

    Regan, R. D.; Davis, W. M.; Cain, J. C.

    1974-01-01

    A subset of POGO satellite magnetometer data has been formed that is suitable for analysis of crustal magnetic anomalies. Using a thirteenth order field model, fit to these data, magnetic residuals have been calculated over the world to latitude limits of plus 50 deg. These residuals averaged over one degree latitude-longitude blocks represent a detailed global magnetic anomaly map derived solely from satellite data. Preliminary analysis of the map indicates that the anomalies are real and of geological origin.

  7. Indoor waypoint navigation via magnetic anomalies.

    PubMed

    Riehle, Timothy H; Anderson, Shane M; Lichter, Patrick A; Condon, John P; Sheikh, Suneel I; Hedin, Daniel S

    2011-01-01

    A wide assortment of technologies have been proposed to construct indoor navigation services for the blind and vision impaired. Proximity-based systems and multilateration systems have been successfully demonstrated and employed. Despite the technical success of these technologies, broad adoption has been limited due to their significant infrastructure and maintenance costs. An alternative approach utilizing the indoor magnetic signatures inherent to steel-frame buildings solves the infrastructure cost problem; in effect the existing building is the location system infrastructure. Although magnetic indoor navigation does not require the installation of dedicated hardware, the dedication of resources to produce precise survey maps of magnetic anomalies represents a further barrier to adoption. In the present work an alternative leader-follower form of waypoint-navigation system has been developed that works without surveyed magnetic maps of a site. Instead the wayfarer's magnetometer readings are compared to a pre-recorded magnetic "leader" trace containing magnetic data collected along a route and annotated with waypoint information. The goal of the navigation system is to correlate the follower's magnetometer data with the leader's to trigger audio cues at precise points along the route, thus providing location-based guidance to the user. The system should also provide early indications of off-route conditions. As part of the research effort a smartphone based application was created to record and annotate leader traces with audio and numeric data at waypoints of interest, and algorithms were developed to determine (1) when the follower reaches a waypoint and (2) when the follower goes off-route. A navigation system utilizing this technology would enable a low-cost indoor navigation system capable of replaying audio annotations at precise locations along pre-recorded routes.

  8. Anomaly induced effects in a magnetic field

    NASA Astrophysics Data System (ADS)

    Antoniadis, Ignatios; Boyarsky, Alexey; Ruchayskiy, Oleg

    2008-04-01

    We consider a modification of electrodynamics by an additional light massive vector field, interacting with the photon via Chern-Simons-like coupling. This theory predicts observable effects for the experiments studying the propagation of light in an external magnetic field, very similar to those, predicted by theories of axion and axion-like particles. We discuss a possible microscopic origin of this theory from a theory with non-trivial gauge anomaly cancellation between massive and light particles (including, for example, millicharged fermions). Due to the conservation of the gauge current, the production of the new vector field is suppressed at high energies. As a result, this theory can avoid both stellar bounds (which exist for axions) and the bounds from CMB considered recently, allowing for positive results in experiments like ALPS, LIPPS, OSQAR, PVLAS-2, BMV, Q&A, etc.

  9. The mineralogy of global magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E. (Principal Investigator)

    1981-01-01

    Progress is reported in developing predictive abilities to evaluate the potential stabilities of magnetic minerals in the Earth crust and mantle by: (1) computing oxidation state profiling as a function of temperature and pressure; (2) compiling data on basalts to establish validity of the oxidation state profiles; (3) determining Fe-Ni alloys in association with magnetitie as a function of temperature and oxidation state; and (4) acquiring large chemical data banks on the mineral ilmenite which decomposes to mineral spinel in the presence of high sulfur or carbonate environments in the lower crust upper mantle. In addition to acquiring these data which are related to constraining Curie isotherm depths, an excellent correlation was found between MAGSAT anomaly data and the geology of West Africa.

  10. Strong Magnetic Anomalies on the Lunar Near Side

    NASA Technical Reports Server (NTRS)

    Halekas, J. S.; Mitchell, D. L.; Lin, R. P.; Frey, S.; Acuna, M. H.; Hood, L. L.; Binder, A.

    2000-01-01

    The near side magnetic field is dominated by the demagnetized Imbrium basin and Oceanus Procellarum regions. However, surrounding this area are a number of strong magnetic anomalies, including Rima Sirsalis and Reiner Gamma.

  11. Continental and oceanic magnetic anomalies: Enhancement through GRM

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.

    1985-01-01

    In contrast to the POGO and MAGSAT satellites, the Geopotential Research Mission (GRM) satellite system will orbit at a minimum elevation to provide significantly better resolved lithospheric magnetic anomalies for more detailed and improved geologic analysis. In addition, GRM will measure corresponding gravity anomalies to enhance our understanding of the gravity field for vast regions of the Earth which are largely inaccessible to more conventional surface mapping. Crustal studies will greatly benefit from the dual data sets as modeling has shown that lithospheric sources of long wavelength magnetic anomalies frequently involve density variations which may produce detectable gravity anomalies at satellite elevations. Furthermore, GRM will provide an important replication of lithospheric magnetic anomalies as an aid to identifying and extracting these anomalies from satellite magnetic measurements. The potential benefits to the study of the origin and characterization of the continents and oceans, that may result from the increased GRM resolution are examined.

  12. A model of ocean basin crustal magnetization appropriate for satellite elevation anomalies

    NASA Technical Reports Server (NTRS)

    Thomas, Herman H.

    1987-01-01

    A model of ocean basin crustal magnetization measured at satellite altitudes is developed which will serve both as background to which anomalous magnetizations can be contrasted and as a beginning point for studies of tectonic modification of normal ocean crust. The model is based on published data concerned with the petrology and magnetization of the ocean crust and consists of viscous magnetization and induced magnetization estimated for individual crustal layers. Thermal remanent magnetization and chemical remanent magnetization are excluded from the model because seafloor spreading anomalies are too short in wavelength to be resolved at satellite altitudes. The exception to this generalization is found at the oceanic magnetic quiet zones where thermal remanent magnetization and chemical remanent magnetization must be considered along with viscous magnetization and induced magnetization.

  13. Improving the geological interpretation of magnetic and gravity satellite anomalies

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Braile, L. W. (Principal Investigator); Vonfrese, R. R. B.

    1985-01-01

    Current limitations in the quantitative interpretation of satellite-elevation geopotential field data and magnetic anomaly data were investigated along with techniques to overcome them. A major result was the preparation of an improved scalar magnetic anomaly map of South America and adjacent marine areas directly from the original MAGSAT data. In addition, comparisons of South American and Euro-African data show a strong correlation of anomalies along the Atlantic rifted margins of the continents.

  14. Statistical analysis of the lithospheric magnetic anomaly data

    NASA Astrophysics Data System (ADS)

    Pavon-Carrasco, Fco Javier; de Santis, Angelo; Ferraccioli, Fausto; Catalán, Manuel; Ishihara, Takemi

    2013-04-01

    Different analyses carried out on the lithospheric magnetic anomaly data from GEODAS DVD v5.0.10 database (World Digital Magnetic Anomaly Map, WDMAM) show that the data distribution is not Gaussian, but Laplacian. Although this behaviour has been formerly pointed out in other works (e.g., Walker and Jackson, Geophys. J. Int, 143, 799-808, 2000), they have not given any explanation about this statistical property of the magnetic anomalies. In this work, we perform different statistical tests to confirm that the lithospheric magnetic anomaly data follow indeed a Laplacian distribution and we also give a possible interpretation of this behavior providing a model of magnetization which depends on the variation of the geomagnetic field and both induced and remanent magnetizations in the terrestrial lithosphere.

  15. Absolute Positioning Using The Earth’s Magnetic Anomaly Field

    DTIC Science & Technology

    2016-09-15

    systems do not have. Furthermore, the magnetic anomaly signal is available at all times of the day and under all weather conditions. The general...space weather effects, most magnetic surveys take steps to avoid man- made sources corrupting the measurements, and temporal variations are recorded at a...temporal variations caused by space and ionospheric weather conditions. From 54 Figure 27. World Digital Magnetic Anomaly Map [43] 55 a practical standpoint

  16. MAGSAT correlations with geoid anomalies. [magnetic anomalies in the western Gulf of Mexico

    NASA Technical Reports Server (NTRS)

    Bowin, C. O. (Principal Investigator)

    1984-01-01

    A digital data library of MAGSAT data is described and its applications and capabilities are reviewed. Polynomial trends were removed from each half-orbit in order to estimate and remove ring current effects from the data. The MAGSAT data in the Gulf of Mexico region was analyzed to define better the possible relation of the negative MAGSAT anomaly there to the negative residual geoid anomaly in the western Gulf of Mexico. Since the shape and location of the negative magnetic anomaly are variable depending upon the particular polynomial surface and curve orders used, no definitive conclusion as to the degree of correspondance between the residual geoid and MAGSAT lithosphere anomalies is offered.

  17. Study of gravity and magnetic anomalies using MAGSAT data

    NASA Technical Reports Server (NTRS)

    Braile, L. W.; Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator)

    1981-01-01

    The results of modeling satellite-elevation magnetic and gravity data using the constraints imposed by near surface data and seismic evidence shows that the magnetic minimum can be accounted for by either an intracrustal lithologic variation or by an upwarp of the Curie point isotherm. The long wavelength anomalies of the NOO's-vector magnetic survey of the conterminous U.S. were contoured and processed by various frequency filters to enhance particular characteristics. A preliminary inversion of the data was completed and the anomaly field calculated at 450 km from the equivalent magnet sources to compare with the POGO satellite data. Considerable progress was made in studing the satellite magnetic data of South America and adjacent marine areas. Preliminary versions of the 1 deg free-air gravity anomaly map (20 m gal contour interval) and the high cut (lambda approximately 8 deg) filtered anomaly maps are included.

  18. The south-central United States magnetic anomaly

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Braile, L. W. (Principal Investigator); Starich, P. J.

    1984-01-01

    The South-Central United States Magnetic Anomaly is the most prominent positive feature in the MAGSAT scalar magnetic field over North America. The anomaly correlates with increased crustal thickness, above average crustal velocity, negative free air gravity anomalies and an extensive zone of Middle Proterozoic anorogenic felsic basement rocks. Spherical dipole source inversion of the MAGSAT scalar data and subsequent calculation of reduced to pole and derivative maps provide constraints for a crustal magnetic model which corresponds geographically to the extensive Middle Proterozoic felsic rocks trending northeasterly across the United States. These felsic rocks contain insufficient magnetization or volume to produce the anomaly, but are rather indicative of a crustal zone which was disturbed during a Middle Proterozoic thermal event which enriched magnetic material deep in the crust.

  19. Magnetic anomalies and tectonic fabric of marginal basins North of New Zealand

    SciTech Connect

    Malahoff, A.; Feden, R.H.; Fleming, H.S.

    1982-05-10

    Detailed airborne magnetic studies conducted over the region of the S. W. Pacific marginal basins extending from the Solomon Islands to New Zealand suggest that three major phases of basin formation and island arc development have occurred in this region. Development of the Tasman Sea took place during the Late Cretaceous-Paleocene. Development of the basins to the east of the Tasman Sea occurred predominantly during the Oligocene as well as during the Upper Miocene to Recent. The South Fuji Basin, consisting of the Kupe and Minerva Abyssal Plains, is marked by the presence of possibly two RRR triple junction spreading centers that were active between the times of anomalies 13 to 7 (36--25.5 m.y.). The Kupe Abyssal Plain shows the presence of residual magnetic anomalies 7 to 13 of the eastern limb of the proposed spreading center. The western limb appears to have been subducted beneath the present site of the Three Kings Rise. This seafloor spreading phase (calculated half-spreading rate of 35 mm/yr) was coincident with the overthrusting phase of the New Caledonia ultramafic rocks. During that period, active volcanism along the then continuous Solomons-New Hebrides-Fiji-Lau Island arc was taking place. Magnetic anomalies from 1 to 4 (0--8 m.y. B. P.) are seen to extend along a clearly defined lineation pattern over the North Fuji Basin.

  20. Alternative explanation for intermediate--wavelength magnetic anomalies

    SciTech Connect

    Shure, L.; Parker, R.L.

    1981-12-10

    Harrison and Carle and others have examined very long profiles of the magnetic field and have calculated one-dimensional power spectra. In these they expect to see, but do not find, a minimum in power at intermediate wavelengths, between 65 and 150 km. Conventional one-dimensional models of the field predict very little power in this band, which lies between the spectral peaks arising from sources in the crust and the core. Mantle sources or high-intensity, long-wavelength magnetizations have been proposed to account for the observations. An alternative, more plausible explanation is that one-dimensional spectra of two-dimensional fields contain contributions from wavenumbers in the perpendicular (i.e., nonsampled) direction. Unless the seafloor spreading anomalies are perfectly lineated at right angles to the profile, some low-wavenumber energy must be attributed to this effect; we propose that such directional aliasing is a major factor in the power spectra. To support this idea we discuss theoretical models and analyze a large-scale marine survey.

  1. Hematite Versus Magnetite as the Signature for Planetary Magnetic Anomalies?

    NASA Technical Reports Server (NTRS)

    Kletetshka, Gunther; Taylor, Patrick T.; Wasilewski, Peter J.

    1999-01-01

    Crustal magnetic anomalies are the result of adjacent geologic units having contrasting magnetization. This magnetization arises from induction and/or remanence. In a planetary context we now know that Mars has significant crustal magnetic anomalies due to remanent magnetization, while the Earth has some anomalies where remanence can be shown to be important. This picture, however, is less clear because of the nature and the magnitude of the geomagnetic field which is responsible for superimposed induced magnetization. Induced magnetization assumes a magnetite source, because of its much greater magnetic susceptibility when compared with other magnetic minerals. We investigated the TRM (thermoremanent magnetization) acquisition of hematite, in weak magnetic fields up to 1 mT, to determine if the remanent and induced magnetization of hematite could compete with magnetite. TRM acquisition curves of magnetite and hematite show that multi-domain hematite reaches TRM saturation (0.3 - 0.4 A sq m/kg) in fields as low as 100 microT. However, multi-domain magnetite reaches only a few percent of its TRM saturation in a field of 100 microT (0.02 - 0.06 A sq m/kg). These results suggest that a mineral such as hematite and, perhaps, other minerals with significant remanence and minor induced magnetization may play an important role in providing requisite magnetization contrast. Perhaps, and especially for the Mars case, we should reevaluate where hematite and other minerals, with efficient remanence acquisition, exist in significant concentration, allowing a more comprehensive explanation of Martian anomalies and better insight into the role of remanent magnetization in terrestrial crustal magnetic anomalies.

  2. Macquarie island and the cause of oceanic linear magnetic anomalies.

    PubMed

    Varne, R; Gee, R D; Quilty, P G

    1969-10-10

    Macquarie Islands is formed of probably Pliocene oceanic crust. Intruded into pillow lavas is a belt of harzburgite and layered gabbro mnasses cut by dike swarms. Similar belt-like structures may cause the linear magnetic anomalies of the ocean.

  3. The south-central United States magnetic anomaly

    NASA Technical Reports Server (NTRS)

    Starich, P. J.; Hinze, W. J.; Braile, L. W.

    1985-01-01

    A positive magnetic anomaly, which dominates the MAGSAT scalar field over the south-central United States, results from the superposition of magnetic effects from several geologic sources and tectonic structures in the crust. The highly magnetic basement rocks of this region show good correlation with increased crustal thickness, above average crustal velocity and predominantly negative free-air gravity anomalies, all of which are useful constraints for modeling the magnetic sources. The positive anomaly is composed of two primary elements. The western-most segment is related to middle Proterozoic granite intrusions, rhyolite flows and interspersed metamorphic basement rocks in the Texas panhandle and eastern New Mexico. The anomaly and the magnetic crust are bounded to the west by the north-south striking Rio Grande Rift. The anomaly extends eastward over the Grenville age basement rocks of central Texas, and is terminated to the south and east by the buried extension of the Ouachita System. The northern segment of the anomaly extends eastward across Oklahoma and Arkansas to the Mississippi Embayment. It corresponds to a general positive magnetic region associated with the Wichita Mountains igneous complex in south-central Oklahoma and 1.2 to 1.5 Ga. felsic terrane to the north.

  4. Near-seafloor magnetic field observations at the Mariana Trough back-arc spreading center

    NASA Astrophysics Data System (ADS)

    Fujiwara, Toshiya; Asada, Miho; Umino, Susumu; Koike, Yuki; Kanamatsu, Toshiya

    2010-05-01

    We surveyed the Mariana Trough back-arc basin in the western Pacific with the Japanese submersible Shinkai 6500 to understand detailed crustal formation process at the 17° N segment [Fujiwara et al., 2008]. The 17° N segment is suggested to be in vigorous magmatic stage. Sheet lava flows, suggesting a high rate of eruption, occupy the seafloor of the segment even the slow spreading with a full-rate of ~3 cm/yr [Deschamps et al., 2005; Asada et al., 2007]. The objective of magnetic field measurements is to investigate magnetization of lava flows at the seafloor. Near-seafloor observations provide us high-resolution magnetic anomaly that is valuable for the studies of the detailed magnetization structure of ocean crust and paleointensity recorded in the ocean crust. Magnetization intensities relate to age of lava, therefore deep-sea magnetic data may provide geophysical evidence for discussion of relative age differences of the lava flows. Three submersible dives were made in the axial valley situated in the spreading center. One of the dives traversed the axial valley a distance of ~2 km from the center of the valley toward off-axis, roughly parallel to the spreading direction. We observed magnetic anomalies with large-amplitude (up to 5000 nT) and short-wavelength (several tens of meters). We evaluated fine-scale across-axis magnetic structure along the dive path from the anomalies. High magnetization intensity (up to 50 A/m) was estimated at the center of the axial valley, and therefore the lava flows in the area was likely young in age. The magnetization intensity decreased toward the off-axis. The result suggests the seafloor age increases toward the off-axis. However the detailed variation of the magnetization distribution does not show simple seafloor age increment in proportion to distance from the spreading center. It implies the complexity of the crustal formation process. There is no clear correlation between the distribution of magnetization intensity

  5. Magnetic Field Anomalies Above Large Martian Impact Structures

    NASA Astrophysics Data System (ADS)

    Langlais, B.; Ostanciaux; Thébault, E.

    2008-12-01

    The Mars Global Surveyor NASA mission revealed the complex nature of the lithospheric magnetic field of Mars. Intense anomalies are located above the southern cratered highlands, while the giant impact basins (Hellas, Argyre, Utopia) and the northern smoothed lowlands do not show significant anomalies. Here we study the magnetic signal above large impact craters, with diameters ranging between 100 and 2000 km. Magnetic measurements are carefully screened and selected to avoid non static features. Then the mean magnetic field is evaluated both inside each crater rim and in its immediate vicinity, within one crater radius. The ratio of these two quantities helps to determine which craters modified the magnetic properties of the pre-impact lithosphere. In addition, this technique allows the impacts located in the strongly magnetized Terra Sirenum and Terra Cimmeria to be studied. Results of this study, as well as comparison of the magnetic measurements to predicted ones for different pre-impact magnetization directions will be presented.

  6. A triple junction trace beneath Reunion Island? Insight from marine magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Bissessur, D.; Dyment, J.; Deplus, C.; Yatheesh, V.

    2009-04-01

    Reunion Island is the most recent expression of a hotspot which formed the Deccan Trap flood basalt, the Chagos-Laccadives Ridge, the southern part of the Mascarene Plateau, Mauritius and Reunion Islands. Both Mauritius and Reunion islands are isolated structures which have formed on the pre-existing oceanic lithosphere of the Mascarene Basin, an oceanic basin created by seafloor spreading between anomalies 34 and 27 (83-60 Ma). The location of Mauritius and Reunion islands may reflect either a preferential rise of hotspot material through pre-existing structures of the oceanic lithosphere or the discontinuous activity of a weakening hotspot. We address this question using bathymetric and magnetic data collected by R/V L'Atalante in 2006 as part of cruise FOREVER (FORmation and Evolution of the Volcanic Edifice of Reunion), complemented by other data in the area. We apply crossover error analysis to correct data from different cruises for time variations not considered by the IGRF model and build a magnetic anomaly map. This map displays coherent magnetic anomalies over most of the area. Anomalies 28 to 20 are identified in the Madagascar Basin, east of the Mascarene Islands. Conjugate sequences of anomalies 31 to 27 (on the northern flank) and 34 to 27 (on the southern flank) are recognized west of the Mascarene Islands, on the conjugate flanks of the Mascarene fossil spreading centre. In the Mascarene Island compartment, the seafloor spreading anomalies can be deciphered under most of the Reunion Island edifice (radius 100 km) with only an inner zone of radius 50 km showing shorter wavelength anomalies related to the volcanic structures of the island. The seafloor spreading lineations show two orientations, N120°E-N140°E and N90°E-N110°E in the central and eastern part of the compartment, respectively. We interpret these different orientations as reflecting the presence of the trace of the Indian Ocean Triple Junction (IOTJ, between India, Africa, and

  7. The mineralogy of global magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E. (Principal Investigator)

    1982-01-01

    The Curie Balance was brought to operational stage and is producing data of a preliminary nature. Substantial problems experienced in the assembly and initial operation of the instrument were, for the most part, rectified, but certain problems still exist. Relationships between the geology and the gravity and MAGSAT anomalies of West Africa are reexamined in the context of a partial reconstruction of Gondwanaland.

  8. A method of inversion of satellite magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Mayhew, M. A.

    1977-01-01

    A method of finding a first approximation to a crustal magnetization distribution from inversion of satellite magnetic anomaly data is described. Magnetization is expressed as a Fourier Series in a segment of spherical shell. Input to this procedure is an equivalent source representation of the observed anomaly field. Instability of the inversion occurs when high frequency noise is present in the input data, or when the series is carried to an excessively high wave number. Preliminary results are given for the United States and adjacent areas.

  9. Investigation of Marine Magnetic Vector Anomalies in the Southern Ayu Trough, Southern Philippine Sea

    NASA Astrophysics Data System (ADS)

    Kim, S.; Lee, S.

    2001-12-01

    The Ayu Trough is a divergent margin, located at the boundary of the Philippine Sea and the Caroline Plates. Previous attempts to resolve the magnetic lineations of this region using total magnetic field have not been successful because it represents a case of east-west spreading center situated near the magnetic equator. The difficulty is compounded by the fact that the Ayu Trough is an ultra-slow-spreading center, which exhibits a complex history of evolution. As an attempt to get around the inherent ambiguity of total field measurement, a shipboard three-component magnetometer was employed during our recent cruise to the Ayu Trough along with proton precession magnetometer. This study examines the vector magnetic data collected in the south part of the Ayu Trough and compares them with tectonic features identified from other geophysical measurements. First, the magnetic field due to the ship was removed from the measured field. We then subtracted the International Geomagnetic Reference Field and the diurnal variation recorded at Guam observatory from our measurement. The amplitude of the north-south component anomalies is substantially less than that of other anomalies, which suggests that the general strike of magnetic lineations in this region is north-south. The magnetic boundary and their strike were estimated by assuming that the magnetic sources are two-dimensional. On the basis of its tectonic structure and interpretation of the total field anomaly pattern, the Ayu Trough can be divided into two sections with distance from the axis: the exterior (> 100 km from the axis) which shows evidence of rifted margin and the interior (< 100 km from the axis) which exhibits the characteristics of seafloor spreading. The vector magnetic anomaly appears to be useful in determining major boundaries, such as those between the exterior and interior sections in our area. Within the interior section of the Ayu Trough, however, the discrimination of magnetic boundaries was

  10. Magnetic resonance imaging of pediatric soft-tissue vascular anomalies.

    PubMed

    Navarro, Oscar M

    2016-05-01

    Magnetic resonance (MR) imaging can be used in the management of pediatric soft-tissue vascular anomalies for diagnosing and assessing extent of lesions and for evaluating response to therapy. MR imaging studies often involve a combination of T1- and T2-weighted images in addition to MR angiography and fat-suppressed post-contrast sequences. The MR imaging features of these vascular anomalies when combined with clinical findings can aid in diagnosis. In cases of complex vascular malformations and syndromes associated with vascular anomalies, MR imaging can be used to evaluate accompanying soft-tissue and bone anomalies. This article reviews the MR imaging protocols and appearances of the most common pediatric soft-tissue vascular anomalies.

  11. Magsat magnetic anomaly contrast across Labrador Sea passive margins

    NASA Technical Reports Server (NTRS)

    Bradley, Lauren M.; Frey, Herbert

    1991-01-01

    Many passive margins not complicated by nearby anomalous crustal structure have satellite elevation crustal magnetic anomaly contrasts across them that are recognizable in reduced-to-pole versions of the Magsat and POGO data. In the Labrador Sea region this contrast is particularly well developed with strong positive anomalies overlying the continental crust of Greenland and eastern Canada and prominent negative anomalies situated over the Labrador Sea and Baffin Bay. In this work, forward modeling of the large-scale crustal bodies in this region (continental, oceanic, passive margin, several anomalous structures) was used to show that the Magsat anomaly contrast is due simply to the change in crustal susceptibility and thickness at the continental/oceanic crustal transition. Because the thickness varies more than the average susceptibility from continental to oceanic crust, the strong anomaly contrast is essentially an edge effect due mostly to the change in crustal structure.

  12. The Origin of the Jurassic Quiet Zone -new insights from Hawaiian Jurassic magnetic anomalies (Invited)

    NASA Astrophysics Data System (ADS)

    Tominaga, M.; Tivey, M.; Sager, W. W.

    2013-12-01

    Marine magnetic anomalies recorded in oceanic crust, have played a central role in documenting Earth's magnetic field history as compiled in the geomagnetic polarity timescale (GPTS). The oldest part of the marine record is the Jurassic Quiet Zone (JQZ) (pre-M29 chrons) which is known to be a period when field intensity was low, while reversal rate was high. The origin and character of the JQZ has been the subject of marine magnetic studies over past 20 years in the western Pacific where the oldest and arguably best preserved Jurassic magnetic anomalies create three Jurassic lineation sets (Japanese, Hawaiian, and Phoenix). The Japanese JQZ sequence was extensively investigated by an aeromagnetic and 2 deeptow magnetometer surveys, revealing (i) the presence of lineated anomalies older than M29; (ii) a GPTS record extending from M29 to M44 with a tie to ODP Hole 801C and (iii) remarkably fast reversals that decrease in intensity back in time until M38. Prior to M38 there is a low amplitude zone (LAZ) in anomalies lasting until M42, when both anomaly amplitude and a lineated character reappears around Hole 801C. Recently collected (2011) high quality seasurface marine magnetic anomaly data from the Hawaiian lineations show changes in magnetic anomaly shape and amplitude that are similar in to the Japanese lineations, suggesting that the anomalies record globally coherent geomagnetic field behavior for the Jurassic. Specifically, the strong similarity of anomaly patterns between the Japanese and Hawaiian sequences from M19 to M38 supports the remarkably dynamic geomagnetic field behavior of fast reversals and changing intensity, confirming a proposed record of the GPTS sequence for M29 to M38. While the LAZ in the Hawaiian sequence is not as clear as in the Japanese lineations, we believe we can correlate the earlier M42-M44 sequence between the two sets of lineations. The slower spreading rate in the Hawaiian lineations may contribute to this lack of resolution of

  13. SEISMIC DISCRIMINATION OF THERMAL AND MAGNETIC ANOMALIES IN SUNSPOT UMBRAE

    SciTech Connect

    Lindsey, C.; Cally, P. S.; Rempel, M.

    2010-08-20

    Efforts to model sunspots based on helioseismic signatures need to discriminate between the effects of (1) a strong magnetic field that introduces time-irreversible, vantage-dependent phase shifts, apparently connected to fast- and slow-mode coupling and wave absorption and (2) a thermal anomaly that includes cool gas extending an indefinite depth beneath the photosphere. Helioseismic observations of sunspots show travel times considerably reduced with respect to equivalent quiet-Sun signatures. Simulations by Moradi and Cally of waves skipping across sunspots with photospheric magnetic fields of order 3 kG show travel times that respond strongly to the magnetic field and relatively weakly to the thermal anomaly by itself. We note that waves propagating vertically in a vertical magnetic field are relatively insensitive to the magnetic field, while remaining highly responsive to the attendant thermal anomaly. Travel-time measurements for waves with large skip distances into the centers of axially symmetric sunspots are therefore a crucial resource for discrimination of the thermal anomaly beneath sunspot umbrae from the magnetic anomaly. One-dimensional models of sunspot umbrae based on compressible-radiative-magnetic-convective simulations such as by Rempel et al. can be fashioned to fit observed helioseismic travel-time spectra in the centers of sunspot umbrae. These models are based on cooling of the upper 2-4 Mm of the umbral subphotosphere with no significant anomaly beneath 4.5 Mm. The travel-time reductions characteristic of these models are primarily a consequence of a Wilson depression resulting from a strong downward buoyancy of the cooled umbral medium.

  14. Electron dynamics in the minimagnetosphere above a lunar magnetic anomaly

    NASA Astrophysics Data System (ADS)

    Usui, Hideyuki; Miyake, Yohei; Nishino, Masaki N.; Matsubara, Takuma; Wang, Joseph

    2017-02-01

    We consider a three-dimensional electromagnetic particle-in-cell simulation of the boundary layer current in a minimagnetosphere created by the interaction between a magnetized plasma flow, which models the typical solar wind, and a small-scale magnetic dipole, which represents the Reiner Gamma magnetic anomaly on the lunar surface. The size of this magnetic anomaly (measured as the distance from the dipole center to the position where the pressure of the local magnetic field equals the dynamic pressure of the solar wind) is one quarter that of the Larmor radius of the solar wind ions. In spite of the weak magnetization of the ions, a minimagnetosphere is formed above the magnetic anomaly. In the boundary layer of the minimagnetosphere, the electron current is dominant. Due to the intense electric field induced by charge separation, electrons entering the boundary layer undergo E × B drift. In each hemisphere, the electron boundary current due to the drift shows a structure where the convection reverses; these structures are symmetric with respect to the magnetic equator. Detailed analysis of the electron cyclotron motion shows that electrons at the edge of the inner boundary layer obtain maximum velocity by the electric field acceleration due to the charge separation, not due to the drift of the electron's guiding center. The maximum electron velocity is approximately 8 times that of the upstream plasma. The width of the boundary layer current becomes approximately equal to the radius of the local electron cyclotron.

  15. First high-resolution near-seafloor survey of magnetic anomalies of the South China Sea

    NASA Astrophysics Data System (ADS)

    Lin, J.; Xu, X.; Li, C.; Sun, Z.; Zhu, J.; Zhou, Z.; Qiu, N.

    2013-12-01

    -wavelength anomalies were unrecognized in sea surface measurements. (3) Preliminary results showed that the study regions might have experienced several episodes of magnetic reversal events that were not recognized in existing models. (4) We are currently investigating the geomagnetic timing of these relatively short-duration events to determine the detailed spreading history of the sub-basins of the SCS. These high-resolution near-seafloor magnetic survey lines are located close to the planned drilling sites of IODP Expedition 349 scheduled for January-March 2014.

  16. Improved determination of vector lithospheric magnetic anomalies from MAGSAT data

    NASA Technical Reports Server (NTRS)

    Ravat, Dhananjay

    1993-01-01

    Scientific contributions made in developing new methods to isolate and map vector magnetic anomalies from measurements made by Magsat are described. In addition to the objective of the proposal, the isolation and mapping of equatorial vector lithospheric Magsat anomalies, isolation of polar ionospheric fields during the period were also studied. Significant progress was also made in isolation of polar delta(Z) component and scalar anomalies as well as integration and synthesis of various techniques of removing equatorial and polar ionospheric effects. The significant contributions of this research are: (1) development of empirical/analytical techniques in modeling ionospheric fields in Magsat data and their removal from uncorrected anomalies to obtain better estimates of lithospheric anomalies (this task was accomplished for equatorial delta(X), delta(Z), and delta(B) component and polar delta(Z) and delta(B) component measurements; (2) integration of important processing techniques developed during the last decade with the newly developed technologies of ionospheric field modeling into an optimum processing scheme; and (3) implementation of the above processing scheme to map the most robust magnetic anomalies of the lithosphere (components as well as scalar).

  17. Plasma acceleration above martian magnetic anomalies.

    PubMed

    Lundin, R; Winningham, D; Barabash, S; Frahm, R; Holmström, M; Sauvaud, J-A; Fedorov, A; Asamura, K; Coates, A J; Soobiah, Y; Hsieh, K C; Grande, M; Koskinen, H; Kallio, E; Kozyra, J; Woch, J; Fraenz, M; Brain, D; Luhmann, J; McKenna-Lawler, S; Orsini, R S; Brandt, P; Wurz, P

    2006-02-17

    Auroras are caused by accelerated charged particles precipitating along magnetic field lines into a planetary atmosphere, the auroral brightness being roughly proportional to the precipitating particle energy flux. The Analyzer of Space Plasma and Energetic Atoms experiment on the Mars Express spacecraft has made a detailed study of acceleration processes on the nightside of Mars. We observed accelerated electrons and ions in the deep nightside high-altitude region of Mars that map geographically to interface/cleft regions associated with martian crustal magnetization regions. By integrating electron and ion acceleration energy down to the upper atmosphere, we saw energy fluxes in the range of 1 to 50 milliwatts per square meter per second. These conditions are similar to those producing bright discrete auroras above Earth. Discrete auroras at Mars are therefore expected to be associated with plasma acceleration in diverging magnetic flux tubes above crustal magnetization regions, the auroras being distributed geographically in a complex pattern by the many multipole magnetic field lines extending into space.

  18. The next generation Antarctic digital magnetic anomaly map

    USGS Publications Warehouse

    von Frese, R.R.B; Golynsky, A.V.; Kim, H.R.; Gaya-Piqué, L.; Thébault, E.; Chiappinii, M.; Ghidella, M.; Grunow, A.; ,

    2007-01-01

    S (Golynsky et al., 2001). This map synthesized over 7.1 million line-kms of survey data available up through 1999 from marine, airborne and Magsat satellite observations. Since the production of the initial map, a large number of new marine and airborne surveys and improved magnetic observations from the Ørsted and CHAMP satellite missions have become available. In addition, an improved core field model for the Antarctic has been developed to better isolate crustal anomalies in these data. The next generation compilation also will likely represent the magnetic survey observations of the region in terms of a high-resolution spherical cap harmonic model. In this paper, we review the progress and problems of developing an improved magnetic anomaly map to facilitate studies of the Antarctic crustal magnetic field

  19. New magnetic anomaly map of East Antarctica and surrounding regions

    USGS Publications Warehouse

    Golynsky, A.; Blankenship, D.; Chiappini, M.; Damaske, D.; Ferraccioli, F.; Finn, C.; Golynsky, D.; Goncharov, A.; Ishihara, T.; Ivanov, S.; Jokat, W.; Kim, H.R.; König, M.; Masolov, V.; Nogi, Y.; Sand, M.; Studing, M.; ,

    2007-01-01

    community over East Antarctica and surrounding regions, significantly upgrade the Antarctic Digital Magnetic Anomaly Project (ADMAP) compilation and lead to substantial improvements in magnetic anomaly pattern recognition. New data have been matched in one inverse operation by minimizing the data differences for the areas of overlap. The aeromagnetic data show many previously unknown magnetic patterns, lineaments and trends, defining the spatial extent of Ferrar volcanics and plutonic Granite Harbour Intrusives in the Transantarctic Mountains and previously unknown tectonic trends of the East Antarctic craton. Regional aeromagnetic investigations have successfully delineated Early Paleozoic inherited crustal features along the flanks of the West Antarctic Rift System and the southern boundary of the Archean Ruker Terrane in the Prince Charles Mountains. Magnetic records along the East Antarctic continental margin provide new constraints on the breakup of Gondwana.

  20. Intermediate-wavelength magnetic anomalies over the central Pacific

    NASA Technical Reports Server (NTRS)

    Labrecque, J. L.; Cande, S. C.

    1984-01-01

    A technique to extract the intermediate wavelength anomaly field from random ship tracks has been developed and is applied to extract the field from marine survey data of the central Pacific in the band pass of 4000-400 km. The technique minimizes the effects of external field sources, secular variation, and strike aliasing. The derived data field is compared to the equivalent MAGSAT data set, and it is shown that anomalies observed in both fields are correlatable to geologic features within the oceanic lithosphere but differ in amplitude by a factor of two. Likely sources for this discrepancy are identified. It is also shown that remanent magnetization of the central Pacific seamounts produces negative magnetic anomalies which are observed at satellite altitude.

  1. The possibilities of paleomagnetic and geohistorical analyses of "tiny wiggles" short-period marine magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Ivanov, S. A.; Merkuryev, S. A.

    2016-05-01

    Marine magnetic anomalies of the tiny wiggles (TW) type can be used to solve geohistorical and paleomagnetic problems. The model fields corresponding to Paleocene-Eocene anomalies in the northwestern Indian Ocean, which were formed during the fast-spreading stage, were studied. For these fields, widely used interpretation methods were compared with a method proposed previously by the authors. The testing was performed with first the classical block model and then more complex models reflecting actual processes of oceanic accretion and magnetic field variations in the past. It was shown that the proposed method has advantages for this problem; it gives an error close to the minimum possible error and can adequately be used in interpretations. Spectral and statistical methods are used to estimate the magnetic anomaly resolving power and to study some factors that can exert a distorting influence. In addition, model examples have been used to indicate how the TW determination accuracy is affected by diurnal variations in the main magnetic field (MMF) and by ancient magnetization vector determination errors.

  2. New digital magnetic anomaly database for North America

    USGS Publications Warehouse

    Finn, C.A.; Pilkington, M.; Cuevas, A.; Hernandez, I.; Urrutia, J.

    2001-01-01

    The Geological Survey of Canada (GSC), U.S. Geological Survey (USGS), and Consejo de Recursos Minerales of Mexico (CRM) are compiling an upgraded digital magnetic anomaly database and map for North America. This trinational project is expected to be completed by late 2002.

  3. Magnetic Anomaly Caused By Lightning On Archaeological Sites

    NASA Astrophysics Data System (ADS)

    Verrier, V.; Mathe, P. E.; Rochette, P.; Jones, G.

    Recent developments in archeological surveying have seen the emergence of mag- netic methods, commonly involving near surface measurements of low field magnetic susceptibility. However, these technics remain inefficient to detect either deep buried features or material which susceptibility constrast with the enclosing material is too low. An alternate way to assess site location and archeological features in these cases is provided by the mapping of total magnetic field or field gradient anomalies, due to the induced or remanent magnetizations of the material. REFERENCES : Verrier, V., Rochette, P., Richard, P. and Lojou, J.Y., Paleomagnetic expertise of ground lightning impacts, in 25th Int. Conf. Lightning Protection, Rhodos, p. 166-169, 2000. When remanence dominate, the archeological signal may be complicated by the su- perimposition of an anomaly due to lightning. Locally, the electric discharge generates a strong pulse of magnetic field. The materials around an impact acquired a lightning induced remanent magnetization (LIRM) which endures as long as the materials are not removed. In order to characterize the LIRM signature, some studies were realised on struck sites where the impact point is known. In each case, the LIRM hypothesis was tested on discrete samples collected around the impact, on which the lightning magnetic field intensity was determined (Verrier, 2000). The typical LIRM anomaly was also mapped with the G-858 MagMapper. It consists in a relatively strong dipole associated with maxima that are usually not aligned SN, clearly distinguishable from the archeological signature.

  4. Lunar magnetic anomalies detected by the Apollo substatellite magnetometers

    USGS Publications Warehouse

    Hood, L.L.; Coleman, P.J.; Russell, C.T.; Wilhelms, D.E.

    1979-01-01

    Properties of lunar crustal magnetization thus far deduced from Apollo subsatellite magnetometer data are reviewed using two of the most accurate presently available magnetic anomaly maps - one covering a portion of the lunar near side and the other a part of the far side. The largest single anomaly found within the region of coverage on the near-side map correlates exactly with a conspicuous, light-colored marking in western Oceanus Procellarum called Reiner Gamma. This feature is interpreted as an unusual deposit of ejecta from secondary craters of the large nearby primary impact crater Cavalerius. An age for Cavalerius (and, by implication, for Reiner Gamma) of 3.2 ?? 0.2 ?? 109 y is estimated. The main (30 ?? 60 km) Reiner Gamma deposit is nearly uniformly magnetized in a single direction, with a minimum mean magnetization intensity of ???7 ?? 10-2 G cm3/g (assuming a density of 3 g/cm3), or about 700 times the stable magnetization component of the most magnetic returned samples. Additional medium-amplitude anomalies exist over the Fra Mauro Formation (Imbrium basin ejecta emplaced ???3.9 ?? 109 y ago) where it has not been flooded by mare basalt flows, but are nearly absent over the maria and over the craters Copernicus, Kepler, and Reiner and their encircling ejecta mantles. The mean altitude of the far-side anomaly gap is much higher than that of the near-side map and the surface geology is more complex, so individual anomaly sources have not yet been identified. However, it is clear that a concentration of especially strong sources exists in the vicinity of the craters Van de Graaff and Aitken. Numerical modeling of the associated fields reveals that the source locations do not correspond with the larger primary impact craters of the region and, by analogy with Reiner Gamma, may be less conspicuous secondary crater ejecta deposits. The reason for a special concentration of strong sources in the Van de Graaff-Aitken region is unknown, but may be indirectly

  5. On the origin of the Bangui magnetic anomaly, central African empire

    NASA Technical Reports Server (NTRS)

    Marsh, B. D.

    1977-01-01

    A large magnetic anomaly was recognized in satellite magnetometer data over the Central African Empire in central Africa. They named this anomaly the Bangui magnetic anomaly due to its location near the capital city of Bangui, C.A.E. Because large crustal magnetic anomalies are uncommon, the origin of this anomaly has provoked some interest. The area of the anomaly was visited to make ground magnetic measurements, geologic observations, and in-situ magnetic susceptibility measurements. Some rock samples were also collected and chemically analyzed. The results of these investigations are presented.

  6. Interpretation of long- and short-wavelength magnetic anomalies

    USGS Publications Warehouse

    DeNoyer, John M.; Barringer, Anthony R.

    1980-01-01

    Magset was launched on October 30, 1979. More than a decade of examining existing data, devising appropriate models of the global magnetic field, and extending methods for interpreting long-wavelength magnetic anomalies preceded this launch Magnetic data collected by satellite can be interrupted by using a method of analysis that quantitively describes the magnetic field resulting from three-dimensional geologic structures that are bounded by an arbitrary number of polygonal faces, Each face my have any orientation and three or more sides. At each point of the external field, the component normal to each face is obtained by using an expression for the solid angle subtended by a generalized polygon. The "cross" of tangential components are relatively easy to obtain for the same polygons. No approximations have been made related to orbit height that restrict the dimensions of the polygons relative to the distance from the external field points. This permits the method to be used to model shorter wavelength anomalies obtained from aircraft or ground surveys. The magnetic fields for all the structures considered are determine in the same rectangular coordinate system. The coordinate system is in depended from the orientation of geologic trends and permits multiple structures or bodies to be included in the same magnetic field calculations. This single reference system also simplified adjustments in position and direction to account for earth curvature in regional interpretation.

  7. Manifestation of the petrogeneration zones of Northern and the Bering seas in ground magnetic anomalies and anomalies of satellite Champ

    NASA Astrophysics Data System (ADS)

    Litvinova, Tamara; Krasinsky, Egor; Petrova, Alevtina; Demina, Irina

    2010-05-01

    The purpose of this paper are showed results of studying of specificity of a deep structure of zones of petrogeneration Northern and the Bering seas on aeromagnetic and satellite magnetometric datas. Research lateral and vertical heterogeneitys an earth's crust of Northern sea is carried out on the basis of the analysis of measurements of satellite Champ at height of 100 km and the digital database created on materials of sea shooting of a geomagnetic field, executed on non-magnetic schooner "Zarya". On sea measurements in Northern sea through large oil fields and gas ( Frigg, Ekofisk, Forties trough, Leman, etc.). Geomagnetic sections for an interval of depths from 1 up to 30 km are constructed. It has allowed to study character of distribution of magnetization of breeds of a cover, horizontal lamination intracore layers of an earth's crust and to allocate in zones petrogeneration synvertical fluidoconduct zones the channels described by alternation of not magnetic and low-magnetic layers. They were showed on geomagnetic sections as permeable zones quasi- laminated structures with the lowered magnetic properties in an interval of depths from 8 up to 28 km. Comparison to a map of the magnetic anomalies measured at height of 100 km by satellite Champ, has shown, that areas of the greatest petrocongestions North Sea рифта at height of 100 km are dated for a zone of gradients and a minimum of northeast displacement of regional anomalies of western and east blocks of Northern sea. It corresponds to representations about an orientation of a fissuring zone and the increased size of a geothermal gradient North Sea rift and is corresponded position allocated on hydromagnetic structures deep fluidoconduct channels. Thus, distribution to water areas of deposits of deposits is emphasized not only low-magnetic areas in a thickness of a sedimentary cover where they are directly located, but also by not magnetic lenses in breeds of the base spreading it in intervals of

  8. Tracking pigeons in a magnetic anomaly and in magnetically "quiet" terrain

    NASA Astrophysics Data System (ADS)

    Schiffner, Ingo; Fuhrmann, Patrick; Wiltschko, Roswitha

    2011-07-01

    Pigeons were released at two sites of equal distance from the loft, one within a magnetic anomaly, the other in magnetically quiet terrain, and their tracks were recorded with the help of GPS receivers. A comparison of the beginning of the tracks revealed striking differences: within the anomaly, the initial phase lasted longer, and the distance flown was longer, with the pigeons' headings considerably farther from the home direction. During the following departure phase, the birds were well homeward oriented at the magnetically quiet site, whereas they continued to be disoriented within the anomaly. Comparing the tracks in the anomaly with the underlying magnetic contours shows considerable differences between individuals, without a common pattern emerging. The differences in magnetic intensity along the pigeons' path do not differ from a random distribution of intensity differences around the release site, indicating that the magnetic contours do not directly affect the pigeons' routes. Within the anomaly, pigeons take longer until their flights are oriented, but 5 km from the release point, the birds, still within the anomaly, are also significantly oriented in the home direction. These findings support the assumption that magnetically anomalous conditions initially interfere with the pigeons' navigational processes, with birds showing rather individual responses in their attempts to overcome these problems.

  9. Magnetically induced spreading and pattern selection in thin ferrofluid drops.

    PubMed

    Chen, Ching-Yao; Wu, W-L; Miranda, José A

    2010-11-01

    We report an experimental study of a fingering pattern formation which occurs during the spreading of an immiscible thin ferrofluid drop subjected to a radial magnetic field. Our results indicate that this ferrohydrodynamic system works as a magnetic analog of conventional spin coating, where centrifugal driving is replaced with a magnetic body force induced by the radial applied field. In this context, a magnetically tunable pattern selection mechanism is proposed in which the shape and number of the arising fingered structures can be properly controlled.

  10. Using spread spectrum for AMR magnetic sensor

    NASA Astrophysics Data System (ADS)

    Vala, David

    2016-09-01

    This contribution describe invention of Magnetometer with protection against detection by electronic counter- measure (ECM) registered by Czech patent office as patent no. 305322.1 Magnetic sensors are often part of dual use or security instruments and equipment. For this purpose is very interesting to build sensor with is hidden against electronic countermeasure. In this case is very important level and behavior of electromagnetic noise produced by sensor. And also electromagnetic compatibility of electronic devices is the area which significant grows nowadays too. As the consequence of this growth there is a continuous process of making more strict standards focused on electromagnetic radiation of electronic devices. Sensors technology begins to be a part of these issues due sensors bandwidth increasing and approaching to frequency of radio communication band. Nowadays microcontrollers and similar digital circuits are integrated into sensors devices and it brings new sources of electromagnetic radiation in modern smart sensors.

  11. Detailed study of the Mare Crisium northern magnetic anomaly

    NASA Astrophysics Data System (ADS)

    Baek, Seul-Min; Kim, Khan-Hyuk; Garrick-Bethell, Ian; Jin, Ho; Lee, Hyo-Jeong; Lee, Jung-Kyu

    2017-02-01

    Low-altitude Lunar Prospector (LP) magnetometer data for Mare Crisium show two magnetic anomalies near its inner northern and southern edges. Because these features are located inside a basin, they were likely formed by slow cooling of the basin's melt, or the partially melted mantle, instead of by any impact-related shock magnetization process. Therefore, they are important for assessing the nature of the ancient dynamo field that produced them. In this study we confine our attention to the simpler northern anomaly (CNA) and use low-altitude (˜22 km) LP data to model its source body as a dipole and magnetized disks of different radii. We infer that the source is likely located ˜20-30 km from the surface and horizontally localized within a small region (<1° or <˜30 km radius). The surface field intensity calculated from the best fit dipole is in good agreement with that obtained from LP Electron Reflectometer data. Our magnetization directions are substantially different from two previous studies, largely due to using lower altitude data to perform our inversions. We also find a surprising sensitivity to small changes in source body latitude (˜1°). The magnetic paleopoles implied by our best fit models are distant from previous estimates by up to ˜50° of great circle arc and are substantially distant from the Moon's present rotation axis. Our results demonstrate how multiple altitude data sets must be used when estimating paleopoles and other properties of even the simplest of the Moon's magnetic anomalies.

  12. Anomalies.

    ERIC Educational Resources Information Center

    Online-Offline, 1999

    1999-01-01

    This theme issue on anomalies includes Web sites, CD-ROMs and software, videos, books, and additional resources for elementary and junior high school students. Pertinent activities are suggested, and sidebars discuss UFOs, animal anomalies, and anomalies from nature; and resources covering unexplained phenonmenas like crop circles, Easter Island,…

  13. A magnetic anomaly of possible economic significance in southeastern Minnesota

    USGS Publications Warehouse

    Zietz, Isidore

    1964-01-01

    An aeromagnetic survey in southeastern Minnesota by the U. S. Geological Survey in cooperation with the State of Minnesota has revealed a high-amplitude, linear, and narrow magnetic feature that suggests a possible source of Precambrian iron-formation of economic value. For the past few years the U. S. Geological Survey has been conducting detailed geophysical studies of the midcontinent gravity anomaly--a broad, high-amplitude feature that extends from Lake Superior through the States of Minnesota, Iowa, Nebraska, and part of Kansas. As part of this study an aeromagnetic survey of the southern part of the State was made in cooperation with the State of Minnesota during the summer of 1963, in which a linear high-amplitude anomaly of the order of 4,000 gammas was discovered. Because of the high amplitude, the linearity, and the narrowness of the magnetic feature, it is believed the source may be Precambrian iron-formation of possible economic value. The anomalous area is in Fillmore County, approximately between the towns of Lanesboro and Peterson in the extreme southeastern part of the State. (See figures 1 and 2.) At the site of the anomaly, Cambrian sedimentary rocks occur in the valley of the Root River, and Ordovician rocks (nearly flat lying) mantle the upland areas. The uplands are largely covered by glacial deposits, which are relatively thin (Paul K. Sims, written communication, 1964). Depths to the Precambrian are estimated to range from 500 feet to 1,000 feet below the surface. The aeromagnetic map shown in figure 2 was compiled from continuous magnetic profiles made along east-west flight lines 1,000 feet above ground, and spaced approximately 1 mile apart. Contour intervals of 20, 100, and 500 gammas were used depending on the intensity. The instrument for the survey was a flux-gate type magnetometer (AN/ASQ-3A) which measures total-field variations. The contour map displays variations in magnetic pattern which are typical of shallow Precambrian rocks

  14. The moon: Sources of the crustal magnetic anomalies

    USGS Publications Warehouse

    Hood, L.L.; Coleman, P.J.; Wilhelms, D.E.

    1979-01-01

    Previously unmapped Apollo 16 subsatellite magnetometer data collected at low altitudes over the lunar near side are presented. Medium-amplitude magnetic anomalies exist over the Fra Mauro and Cayley Formations (primary and secondary basin ejecta emplaced 3.8 to 4.0 billion years ago) but are nearly absent over the maria and over the craters Copernicus, Kepler, and Reiner and their encircling ejecta mantles. The largest observed anomaly (radial component ??? 21 gammas at an altitude of 20 kilometers) is exactly correlated with a conspicuous light-colored deposit on western Oceanus Procellarum known as Reiner ??. Assuming that the Reiner ?? deposit is the source body and estimating its maximum average thickness as 10 meters, a minimum mean magnetization level of 5.2 ?? 2.4 ?? 10-2 electromagnetic units per gram, or ??? 500 times the stable magnetization component of the most magnetic returned sample, is calculated. An age for its emplacement of ??? 2.9 billion years is inferred from photogeologic evidence, implying that magnetization of lunar crustal materials must have continued for a period exceeding 1 billion years. Copyright ?? 1979 AAAS.

  15. Apparatus for detecting a magnetic anomaly contiguous to remote location by SQUID gradiometer and magnetometer systems

    SciTech Connect

    Overton, W.C. Jr.; Steyert, W.A. Jr.

    1984-03-13

    A superconducting quantum interference device (SQUID) magnetic detection apparatus detects magnetic fields, signals, and anomalies at remote locations. Two remotely rotatable SQUID gradiometers may be housed in a cryogenic environment to search for and locate unambiguously magnetic anomalies. The SQUID magnetic detection apparatus can be used to determine the azimuth of a hydrofracture by first flooding the hydrofracture with a ferrofluid to create an artificial magnetic anomaly therein.

  16. Apparatus for detecting a magnetic anomaly contiguous to remote location by squid gradiometer and magnetometer systems

    DOEpatents

    Overton, Jr., William C.; Steyert, Jr., William A.

    1984-01-01

    A superconducting quantum interference device (SQUID) magnetic detection apparatus detects magnetic fields, signals, and anomalies at remote locations. Two remotely rotatable SQUID gradiometers may be housed in a cryogenic environment to search for and locate unambiguously magnetic anomalies. The SQUID magnetic detection apparatus can be used to determine the azimuth of a hydrofracture by first flooding the hydrofracture with a ferrofluid to create an artificial magnetic anomaly therein.

  17. Thermal Sensitivity of MD Hematite: Implication for Magnetic Anomalies

    NASA Technical Reports Server (NTRS)

    Kletetschka, Gunther; Wasilewski, Peter J.; Taylor, Patrick T.

    1999-01-01

    Magnetic remanence of crustal rocks can reside in three common rock-forming magnetic minerals: magnetite, pyrrhotite, and hematite. Thermoremanent magnetization (TRM) of magnetite and pyrrhotite is carried mostly by single domain (SD) grains. The TRM of hematite grains, however, is carried mostly by multidomain (NM) grains. This characteristic is illustrated by TRM acquisition curves for hematite of variable grainsizes. The transition between truly NM behavior and tendency towards SD behavior his been established between hematite grainsizes of 0. 1 and 0.05 mm. Coarse grainsize of lower crustal rocks and the large sensitivity of MD hematite grains to acquire TRM indicates that hematite could be a significant contributor to long-wavelength magnetic anomalies.

  18. Can the Martian magnetic anomalies make for the ionosphere escape?

    NASA Astrophysics Data System (ADS)

    Fedorov, A.; Barabash, S.; Sauvaud, J.; Ferrier, C.

    2011-12-01

    Looking forward to the MAVEN mission, it seems very useful to return to Mars Express data to refresh an important problem of Martian atmosphere escape: what role the crustal magnetic field may play in this process? There are several publications on this topic with completely opposite conclusions. We are trying to use a new approach to this problem. On the base of a statistical study of the ion and electron distributions in the Martian magnetotail we show that the characteristic accelerated and thermalized distributions are not associated with the magnetic anomalies but only with interplanetary magnetic field clock angle. However the presence of the X-aligned crustal magnetic field provides a channel that can guide the heated plasmasheet electrons toward the ionosphere.

  19. Low energy spread ion source with a coaxial magnetic filter

    DOEpatents

    Leung, Ka-Ngo; Lee, Yung-Hee Yvette

    2000-01-01

    Multicusp ion sources are capable of producing ions with low axial energy spread which are necessary in applications such as ion projection lithography (IPL) and radioactive ion beam production. The addition of a radially extending magnetic filter consisting of a pair of permanent magnets to the multicusp source reduces the energy spread considerably due to the improvement in the uniformity of the axial plasma potential distribution in the discharge region. A coaxial multicusp ion source designed to further reduce the energy spread utilizes a cylindrical magnetic filter to achieve a more uniform axial plasma potential distribution. The coaxial magnetic filter divides the source chamber into an outer annular discharge region in which the plasma is produced and a coaxial inner ion extraction region into which the ions radially diffuse but from which ionizing electrons are excluded. The energy spread in the coaxial source has been measured to be 0.6 eV. Unlike other ion sources, the coaxial source has the capability of adjusting the radial plasma potential distribution and therefore the transverse ion temperature (or beam emittance).

  20. Petrological Explanations for the Magnetic Anomalies Detected on Mars

    NASA Technical Reports Server (NTRS)

    Weitz, C. M.; Rutherford, M. J.

    1999-01-01

    The discovery of crustal magnetization in some locations on Mars, particularly the southern highlands, has major implications for the early evolution of Mars. The east-west-trending linear features in the southern highlands with alternating polarity may be the result of an early seafloor spreading process similar to that seen on Earth today. The larger magnetization of the martian crust compared to the Earth can be attributed to its higher Fe content and the proposed minerals associated with this magnetization are multidomain hematite and pyrrhotite. In this study, we discuss the petrological evolution of basalts on Earth and Mars and suggest processes that may enhance crystallization of magnetic minerals in the martian rocks, thereby accounting for their intense magnetic properties.

  1. Magnetoresistance and magnetization anomalies in CeB{sub 6}

    SciTech Connect

    Bogach, A.V. . E-mail: alex@lt.gpi.ru; Glushkov, V.V.; Demishev, S.V.; Samarin, N.A.; Paderno, Yu.B.; Dukhnenko, A.V.; Shitsevalova, N.Yu.; Sluchanko, N.E.

    2006-09-15

    High precision magnetoresistance (MR) {delta}{rho}/{rho}(H,T) and magnetization M(H,T) measurements have been carried out for well known and typical strongly correlated electron system-cerium hexaboride. The detailed measurements have been fulfilled on single crystalline samples of CeB{sub 6} over a wide temperature range T>=1.8K in magnetic fields up to 70kOe. It was shown that the MR anomalies in the magnetic heavy fermion compound under investigation can be consistently interpreted in the frameworks of a simple relation between resistivity and magnetization-{delta}{rho}/{rho}{approx}M{sup 2} obtained by Yosida [Phys. Rev. 107(1957)396]. A local magnetic susceptibility {chi}{sub loc}(T,H)=(1/H*(d({delta}{rho}/{rho})/dH)){sup 1/2} was deduced directly from the MR {delta}{rho}(H,T) measurements and compared with the experimental data of magnetization M(H,T). The magnetic susceptibility dependences {chi}{sub loc}(T,H) and {chi}(T,H) obtained in this study for CeB{sub 6} allow us to analyze the complicated H-T magnetic phase diagram of this so-called dense Kondo-system.

  2. Evaluation of magnetic anomalies located in Lower Bayou Teche, St. Mary Parish, Louisiana

    NASA Astrophysics Data System (ADS)

    Goodwin, R. Christopher; Athens, William P.; Saltus, Allen R., Jr.

    1991-07-01

    This report presents results of testing and assessment of eleven previously recorded magnetic anomalies located in Lower Bayou Teche, St. Mary Parish, Louisiana. Maintenance dredging of Lower Bayou Teche may impact several of the eight anomalies evaluated in this study. Objectives of the study were to conduct detailed surveys and assessments of eight previously located anomalies. These were Anomalies 8, 13, 24a, 29, 30, 31, 33, and 58. Three orther anomalies, Anomaly nos. 23, 24b, and 55 were also briefly examined. Methods used during survey included relocation of each anomaly with a magnetometer; informal magnetic and fathometer survey of each anomaly and its vicinity, physical search of the river bottom at each anomaly location; use of a metal detector to assess the depth of the magnetic source of each anomaly; probing of the river bottom to locate buried structures; and limited excavation with a jet probe to document the source, nature, and research potential of each of the eight anomalies. Two of the anomalies, Anomaly nos. 30 and 58 could not be relocated. Four of the anomalies apparently are associated with modern debris: Anomaly nos. 8, 13, 29, and 31. Anomaly no. 33 appears to be an isolated object. Evidence of structure was observed 14 to 15 ft below water surface, however, it occurs below the project impact zone. One archeological site, the Anomaly no. 23/24 Complex (Site 16SMY76) was defined. It consists of two wooden barges and some twentieth century bridge remains.

  3. Improving the geological interpretation of magnetic and gravity satellite anomalies

    NASA Technical Reports Server (NTRS)

    Hinze, William J.; Braile, Lawrence W.; Vonfrese, Ralph R. B.

    1987-01-01

    Quantitative analysis of the geologic component of observed satellite magnetic and gravity fields requires accurate isolation of the geologic component of the observations, theoretically sound and viable inversion techniques, and integration of collateral, constraining geologic and geophysical data. A number of significant contributions were made which make quantitative analysis more accurate. These include procedures for: screening and processing orbital data for lithospheric signals based on signal repeatability and wavelength analysis; producing accurate gridded anomaly values at constant elevations from the orbital data by three-dimensional least squares collocation; increasing the stability of equivalent point source inversion and criteria for the selection of the optimum damping parameter; enhancing inversion techniques through an iterative procedure based on the superposition theorem of potential fields; and modeling efficiently regional-scale lithospheric sources of satellite magnetic anomalies. In addition, these techniques were utilized to investigate regional anomaly sources of North and South America and India and to provide constraints to continental reconstruction. Since the inception of this research study, eleven papers were presented with associated published abstracts, three theses were completed, four papers were published or accepted for publication, and an additional manuscript was submitted for publication.

  4. Numerical Simulations on Origin of Galilean Moons' Magnetic Anomalies

    NASA Technical Reports Server (NTRS)

    Jiao, LiQuo; Kuang, WeiJia; Ma, ShiZhuang

    2011-01-01

    Galileo mission detected the magnetic anomalies originated from Galilean moons. These anomalies are likely generated in the moons interiors, under the influence of a strong ambient Jovian field. Among various possible generation mechanisms of the anomalies, we focus on magneto-convection and dynamos in the interiors via numerical simulation. To mimic the electromagnetic environment of the moons, we introduce in our numerical model an external uniform magnetic field B(sub 0) with a fixed orientation but varying field strength. Our results show that a finite B(sub 0) can substantially alter the dynamo processes inside the core. When the ambient field strength B(sub 0) increases to approximately 40% of the field generated by the pure dynamo action, the convective state in the core changes significantly: the convective flow decreases by 80% in magnitude, but the differential rotation becomes stronger in much of the fluid layer, leading to a stronger field generated in the core. The field morphologies inside the core tend to align with the ambient field, while the flow patterns show the symmetry-breaking effect under the influence of B(sub 0). Furthermore, the generated field tends to be temporally more stable.

  5. Magnetic torque anomaly in the quantum limit of Weyl semimetals

    PubMed Central

    Moll, Philip J. W.; Potter, Andrew C.; Nair, Nityan L.; Ramshaw, B. J.; Modic, K. A.; Riggs, Scott; Zeng, Bin; Ghimire, Nirmal J.; Bauer, Eric D.; Kealhofer, Robert; Ronning, Filip; Analytis, James G.

    2016-01-01

    Electrons in materials with linear dispersion behave as massless Weyl- or Dirac-quasiparticles, and continue to intrigue due to their close resemblance to elusive ultra-relativistic particles as well as their potential for future electronics. Yet the experimental signatures of Weyl-fermions are often subtle and indirect, in particular if they coexist with conventional, massive quasiparticles. Here we show a pronounced anomaly in the magnetic torque of the Weyl semimetal NbAs upon entering the quantum limit state in high magnetic fields. The torque changes sign in the quantum limit, signalling a reversal of the magnetic anisotropy that can be directly attributed to the topological nature of the Weyl electrons. Our results establish that anomalous quantum limit torque measurements provide a direct experimental method to identify and distinguish Weyl and Dirac systems. PMID:27545105

  6. The Russian contribution in WDMAM-2011 magnetic anomalies and anomalies of satellite Champ

    NASA Astrophysics Data System (ADS)

    Livinova, Tamara; Glebovsky, Vladimir

    2010-05-01

    In VSEGEI is created the renovated digital cartographical model of an anomalous magnetic field (AMF) of territory of Russia and adjacent aquatory of scale 1:2 500000 on the basis of the available base summary digital materials prepared at various times by two organizations: VSEGEI and VNIIOkeangeologia. For this purpose uniform technological rules which have provided satisfactory synthesis of digital data files of an anomalous magnetic field in scale 1:2 500000 have been developed and realized. As a result of processing digital data file AMF the divergences reached 200 нТл, have been eliminated. For inclusion in WDMAM-2011 the Russian side the digital model counted on height 1 km on a grid 5х5км is offered. Anomalous values are designed from normal field VSEGEI of an epoch of 1965. The magnetic grid (5x5 km) within the Russian continental shelf compiled in VNIIOkeangeologia was leveled, adjusted and merged with those created in VSEGEI on shore of Russian Federation. Data processing is made by software Geosoft. Russian magnetic database in the Arctic Ocean was created as a result of adjusting of all historical and recent magnetic data sets, collected several organizations during the period about 40 years. Within the deep part of the Arctic Ocean this information was leveled, adjusted and combined with all available US magnetic data sets under cooperative project between and US Naval Research Laboratory. A result of this compilation is presented by grid of magnetic anomalies (5x5 km) that was used in the CAMP-GM project.

  7. Preliminary interpretation of satellite gravity and magnetic anomalies in the region of the Philippine Sea Plate

    NASA Astrophysics Data System (ADS)

    Chen, C.; Hu, Z.; Du, J.; Wang, Q.

    2011-12-01

    -east, but there is a trend migration to the south for the south tectonic block which may be related to the southeast rift of the Eurasian plate and the northwest spread of the Pacific plate. We find that there are faults of about south-north direction between the north block of West Philippine Basin and Urdaneta Plateau. Moreover, the tectonic is complicated in the south block of West Philippine Basin and there are no apparent tectonic trends. The Shikoku Basin and Parece Vela Basin have lower Bouguer gravity than in West Philippine Basin indicating that the West Philippine Basin has lower thickness crust and becomes thicker from north to south. The density distribution of Philippine plate is not homogeneous, which presents that it is higher in the west plate than the east and shows a low density and low magnetism at Central Basin Ridge. And there are many clear and strong striped magnetic anomalies in the West Philippine Basin having the direction of NWW-SEE, but in Shikoku Basin and Parece Vela Basin the magnetic anomaly is very weak. This study is supported by the National Science Foundation of China (Grant No.: 40730317 and 40774060 ) and International Cooperation Projection in Science and Technology (Grant No.: 2010DFA24580).

  8. Depth Estimation for Magnetic/Gravity Anomaly Using Model Correction

    NASA Astrophysics Data System (ADS)

    Liu, Pengfei; Liu, Tianyou; Zhu, Peimin; Yang, Yushan; Zhou, Qiaoli; Zhang, Henglei; Chen, Guoxiong

    2017-03-01

    The Tilt-depth method has been widely used to determinate the source depth of a magnetic anomaly. In the present study, we deduce similar Tilt-depth methods for both magnetic and gravity data based on the contact and sphere models and obtain the same equation for a gravity anomaly as that for a magnetic anomaly. The theoretical equations and the model tests show that the routine Tilt-depth method would result in unreliable depth estimation for deep sources. This is due to that the contact model is no longer valid for causative sources under the condition in which the depths of causative sources are significantly larger than their horizontal lengths. Accordingly, we suggest that the Tilt-depth derived from the contact model can be used to detect a shallow source, whereas the Tilt-depth derived from the sphere model can be used to detect a deep source. We propose a weighting method based on the estimated depths from both the contact model and the sphere model to estimate the depth for real data. The model tests suggest that the determined depths from the contact model and the sphere model are shallower and deeper, respectively, than the real depth, while the estimated depth from the proposed method is more close to the actual depth. In the application to the Weigang iron ore located in Jiangsu province, China, the routine Tilt-depth method results in -76% relative error, whereas the proposed method obtains the reliable depth estimation compared with the drill holes. In addition, the proposed method works well in the application for the Shijiaquan iron ore located in Shandong province, China. These results indicate that the proposed weighting equation is a general improvement.

  9. The Stand Locations of Ancient People Depending On The Intensity of Local Magnetic Anomalies

    NASA Astrophysics Data System (ADS)

    Shatokhin, I. T.; Khramov, A. V.; Shumilov, O. I.; Kasatkina, E. A.; Raspopov, O. M.

    For analysis 235 ancient people stands in the region of Kursk magnetic anomaly (one of the strongest anomaly all over the world) were chosen. All stands were dated by radiocarbon method and are placed in the State List of Archaeological Monuments of Belgorod Region. The oldest stands were radiocarbon dated to 70,000-50,000 years before present (kyr BP). All stands are located along the 300 km valley of Oskol river, having got a homogeneous climatic conditions. At the half of the valley the intensity of local magnetic field is rather low (0-1000 nT), so the region should be considered as the most comfort area for human occupation. The distribution of human occupation at this site looks as follows: 100% at 50-10 kyr BP, 94% at 6-4 kyr BP, 87% at 4-2 kyr BP, 83% at 3-2 kyr BP and 64% at 2-1 kyr BP. At ancient time humans preferred to occupy the sites with low magnetic field intensity. The spreading of human occupation outside of the comfort zone (more than 34%) began at Iron Age (2-1 kyr BP). Thus it may be concluded that in Palaeolithic age (50-10 kyr BP) humans avoided the area with enhanced level of local magnetic field. This seems to be connected to bad influence of the factor on human health, lower level of orientation on the surface, may be to different plant distribution features, and state of ancient people anxiety. The spreading of human occupation out of the comfort zone at rather recent time seems to be caused by social-economic activity.

  10. Spreading of Magnetic Reconnection X-lines in Three Dimensions

    NASA Astrophysics Data System (ADS)

    Cassak, Paul; Shepherd, Lucas

    2012-03-01

    Naturally occurring magnetic reconnection often begins in a spatially localized region and spreads in the out-of-plane direction in time. A number of authors have studied this problem for magnetotail applications such as substorms and bursty bulk flows, for which the out-of-plane (guide) field is typically small. However, spreading also occurs in laboratory experiments and two-ribbon solar flares (such as the Bastille Day flare), and is inferred to occur at the dayside magnetopause. The reconnection site in each of these settings is known or thought to have a significant guide field. With no guide field, it was shown that the reconnection spreading is controlled by the species that carries the current. However, laboratory experiments with a large guide field (Katz et al., Phys. Rev. Lett., 104, 255004, 2010) revealed that spreading takes place in both directions at the Alfven speed based on the guide field. This implies a qualitative change of behavior as the guide field varies. We present a scaling argument for the condition on the guide field at which the nature of the spreading switches from being caused by current carriers to Alfven waves. Further, we show results of three-dimensional two-fluid simulations that agree with the theory. We discuss applications to observations.

  11. Evolution Of The Alpha Ride, The Arctic Ocean, On The Basis Of The Geohistorical Analysis Of The Magnetic Anomalies

    NASA Astrophysics Data System (ADS)

    Gurevich, N. I.; Merkouriev, S. A.

    2004-12-01

    A new magnetic anomaly map of the Amerasian Basin has been created owing to a joint reprocessing of the Russian and American aeromagnetic data [Glebovsky, Kovacs at all., 2000]. This model produced the base for the magnetic data interpretation on the more qualitative level. As a result three series of seafloor spreading-type magnetic anomalies have been identified within the area of the Alpha Ridge and the adjacent part of the Canada Basin [Gurevich et all, 2003]. Their sources were formed from three spreading centers (SC). Two spreading centers: the western and the eastern, are situated at the axial part of the Alpha Ridge, the third one - the southern, is located on the southern slope of the Alpha Ridge and on the adjacent part of the Canada Basin. The triple junction of these SC had been located in the central part of the recent Alpha Ridge. The geohistorical analysis of these magnetic anomalies is fulfilled using an original computer programs. In consequence of this analysis: the geochronological characteristics are specified; the kinematic characteristics of the oceanic floor movement are determined and the main stages of the area evolution are found. The magnetic anomalies M16r (140 Ma), which signify the position of all three SC, and pair anomalies M20r (146.5 Ma) and M23r (151.5 Ma) are identified enough sure for all three SC and pair anomalies M30r (157.5 Ma) - fore the eastern and the southern SC. Finite and differential Euler poles of the lithospheric plates rotation were calculated for all three SC from best-fit pair magnetic anomalies. All the poles are concentrated around the Nares strait and at the northeastern part of the Ellesmere island. Angle and linear spreading rates were calculated using Euler poles. The calculation has showed that all three SC had low spreading rates. Three stages of the area evolution are found on the basis of the plate tectonic reconstruction for the periods 146.5, 151.5 and 157.5 Ma ago. The first stage, slightly earlier

  12. Comparison between the recent U.S. composite magnetic anomaly map and Magsat anomaly data

    NASA Technical Reports Server (NTRS)

    Schnetzler, C. C.; Taylor, P. T.; Langel, R. A.; Hinze, W. J.; Phillips, J. D.

    1985-01-01

    The present investigation is concerned with a comparison of Magsat data with a Composite Magnetic Anomaly Map (CMAM) of the conterminous U.S. reported by Zietz (1982). The investigation was initiated to test the validity of the satellite measurements, and to provide insights into error or problems in either data set. It is found that upward continuation of the digital CMAM data is not in qualitative agreement with the Magsat map. However, if a least squares fit polynomial surface is taken out prior to upward continuation, there is improved quantitative agreement between a residual CMAM and Magsat. Causes for the remaining differences between the residual, upward continued CMAM and the Magsat map are also considered.

  13. The last frontier? High-resolution, near-bottom measurements of the Hawaiian Jurassic magnetic anomaly sequence

    NASA Astrophysics Data System (ADS)

    Tivey, M.; Tominaga, M.; Sager, W. W.

    2012-12-01

    different spreading centers. In 2011, we undertook the next generation of near-bottom magnetic studies utilizing new autonomous underwater vehicle (AUV) technology (Sentry) and concurrent deeptow and seismic profiling surveys of the Hawaiian anomaly sequence. Preliminary results show a similar anomaly record to the Japanese sequence: an overall decrease in anomaly amplitude from M19 to M38 and a period of low amplitude, which in turn is preceded by a return to stronger amplitude anomalies. The magnetic anomaly correlations between Hawaiian and Japanese sea-surface level profiles confirm the reversal record back in time, at least, to M38. At the mid-water and near-bottom AUV levels, the magnetic data clearly show the short-wavelength anomaly character of the M29-M38 sequence, indicating that the fast reversals observed in the Japanese lineations are also present in the Hawaiian lineation set. The strong similarity of overall anomaly patterns between Japanese and Hawaiian sequences supports the preliminary conclusion that geomagnetic field behavior during the Jurassic was dynamic, with fast reversals and changing intensity, and certainly not "quiet". Finally, AUV surveys provide measurements of the marine magnetic anomaly record whose resolution is limited only by the crustal recording process and crustal magnetic architecture rather than spatial resolution.

  14. Reflected Charged Particle Populations around Dipolar Lunar Magnetic Anomalies

    NASA Astrophysics Data System (ADS)

    Deca, Jan; Divin, Andrey

    2016-10-01

    In this work we analyze and compare the reflected particle populations for both a horizontal and a vertical dipole model embedded in the lunar surface, representing the solar wind interaction with two different lunar magnetic anomaly (LMA) structures. Using the 3D full-kinetic electromagnetic code iPic3D, in combination with a test-particle approach to generate particle trajectories, we focus on the ion and electron dynamics. Whereas the vertical model electrostatically reflects ions upward under both near-parallel and near-perpendicular angles with respect to the lunar surface, the horizontal model only has a significant shallow component. Characterizing the electron dynamics, we find that the interplay of the mini-magnetosphere electric and magnetic fields is capable of temporarily trapping low-energy electrons and possibly ejecting them upstream. Our results are in agreement with recent high-resolution observations. Low- to medium-altitude ion and electron observations might be excellent indicators to complement orbital magnetic field measurements and better uncover the underlying magnetic field structure. The latter is of particular importance in defining the correlation between LMAs and lunar swirls, and further testing the solar wind shielding hypothesis for albedo markings due to space weathering. Observing more reflected ions does not necessarily point to the existence of a mini-magnetosphere.

  15. An equivalent layer magnetization model for the United States derived from satellite altitude magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Mayhew, M. A.

    1982-01-01

    Long wavelength magnetic anomalies measured by the Pogo series satellites at altitudes 400-700 km over the United States and adjacent areas are inverted to an equivalent layer magnetization model based on an equal area dipole source array at the earth's surface. Minimum source spacing giving a stable solution and a physically meaningful magnetization distribution is 300 km, and a scheme is presented for effectively sampling the distribution on a grid twice as fine. The model expresses lateral variation in the vertical integral of magnetization and is a starting point for models of lateral variation in the form of the magnetization-depth curve in the magnetic crust. The magnetization model contours correlate with large-scale tectonic features, and in the western part of the country, probably reflect Curie isotherm undulations.

  16. Lunar Compass: A Rover Mission for Exploration of a Lunar Crustal Magnetic Anomaly

    NASA Astrophysics Data System (ADS)

    Blewett, D. T.; Hurley, D. M.; Denevi, B. W.; Cahill, J. T. S.; Klima, R. L.; Plescia, J. B.; Paranicas, C. P.; Greenhagen, B. T.; Anderson, B. A.; Korth, H.; Ho, G. C.; Nunez, J. I.; Zimmerman, M. I.; Brandt, P. C.

    2016-11-01

    We suggest that a rover mission to a lunar magnetic anomaly could answer key questions in several major fields of planetary science: planetary magnetism, space plasma physics, lunar geology, and space weathering.

  17. Estimating Antarctic Near-Surface Magnetic Anomalies from Oersted and CHAMP Satellite Magnetometer Observations

    NASA Technical Reports Server (NTRS)

    vonFrese, Ralph R. B.; Kim, Hyung Rae; Gaya-Pique, Luis R.; Taylor, Patrick T.; Golynsky, Alexander V.; Kim, Jeong Woo

    2004-01-01

    Significant improvement in predicting near-surface magnetic anomalies can result from the highly accurate magnetic observations of the CHAMP satellite that is orbiting at about 400 km altitude. In general, regional magnetic signals of the crust are strongly masked by the core field and its secular variations due to wavelength coupling in the spherical harmonic representation and thus are difficult to isolate in the satellite measurements. However, efforts to isolate the regional lithospheric from core field components can exploit the correlations between the CHAMP magnetic anomalies and the pseudo magnetic effects inferred from gravity-derived crustal thickness variations. In addition, we can use spectral correlation theory to filter the static lithospheric field components from the dynamic external field effects. Employing these procedures, we processed the CHAMP magnetic conservations for an improved magnetic anomaly map of the Antarctic crust. Relative to the much higher altitude Oersted and noisier Magsat observations, CHAMP magnetic anomalies at 400 km altitude reveal new details on the effects of intra-crustal magnetic features and crustal thickness variations of the Antarctic. Moreover, these results greatly facilitate predicting magnetic anomalies in the regional coverage gaps of the ADMAP compilation of Antarctic magnetic anomalies from shipborne, airborne and ground surveys. Our analysis suggests that considerable new insights on the magnetic properties of the lithosphere may be revealed by a further order-of-magnitude improvement in the accuracy of the magnetometer.

  18. Solar Wind Interaction with Lunar Magnetic Anomalies: Reiner Gamma

    NASA Astrophysics Data System (ADS)

    Deca, Jan; Divin, Andrey; Wang, Xu; Lembège, Bertrand; Markidis, Stefano; Lapenta, Giovanni; Horányi, Mihály

    2016-04-01

    Discovered by early astronomers during the Renaissance, the Reiner Gamma formation is one of the most peculiar lunar surface features. Observations have shown that the tadpole-shaped albedo marking, the so-called swirl, found on the Oceanus Procellarum is co-located with one of the strongest magnetic anomalies (LMA) on our Moon. In previous work, using a horizontal dipole model [Deca et al. 2014, 2015], we have described the formation of a mini-magnetosphere structure surrounding the swirl pattern, locally shielding the underlying lunar surface from the impinging solar wind, and hinting at a correlation with its main surface albedo brightness marking in a distinctive concentric oval shape. Using the observed magnetic field model [Tsunakawa et al. 2015] in our full-kinetic electromagnetic framework, iPic3D, we reproduce a surface weathering pattern closely resembling the details of the Reiner Gamma swirls. This work therefore provides strong evidence that the solar wind standoff theory for lunar swirl formation is the dominant process to explain the albedo markings of the Reiner Gamma region. This work was supported by NASA's SSSERVI/IMPACT and by the Swedish National Space Board, Grant No. 136/11. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center. Test simulations utilised the Janus supercomputer, supported by NSF (CNS-0821794) and CU Boulder.

  19. Absolute Magnetization Distribution on Back-arc Spreading Axis Hosting Hydrothermal Vents; Insight from Shinkai 6500 Magnetic Survey

    NASA Astrophysics Data System (ADS)

    Fujii, M.; Okino, K.; Honsho, C.; Mochizuki, N.; Szitkar, F.; Dyment, J.

    2013-12-01

    Near-bottom magnetic profiling using submersible, deep-tow, Remotely Operated Vehicle (ROV) and Autonomous Underwater Vehicle (AUV) make possible to conduct high-resolution surveys and depict detailed magnetic features reflecting, for instance, the presence of fresh lavas or hydrothermal alteration, or geomagnetic paleo-intensity variations. We conducted near-bottom three component magnetic measurements onboard submersible Shinkai 6500 in the Southern Mariana Trough, where five active hydrothermal vent fields (Snail, Yamanaka, Archean, Pica, and Urashima sites) have been found in both on- and off-axis areas of the active back-arc spreading center, to detect signals from hydrothermally altered rock and to distinguish old and new submarine lava flows. Fourteen dives were carried out at an altitude of 1-40 m during the R/V Yokosuka YK10-10 and YK10-11 cruises in 2010. We carefully corrected the effect of the induced and permanent magnetizations of the submersible by applying the correction method for the shipboard three-component magnetometer measurement modified for deep-sea measurement, and subtracted the IGRF values from the corrected data to obtain geomagnetic vector anomalies along the dive tracks. We then calculated the synthetic magnetic vector field produced by seafloor, assumed to be uniformly magnetized, using three dimensional forward modeling. Finally, values of the absolute magnetizations were estimated by using a linear transfer function in the Fourier domain from the observed and synthetic magnetic anomalies. The distribution of estimated absolute magnetization generally shows low values around the five hydrothermal vent sites. This result is consistent with the equivalent magnetization distribution obtained from previous AUV survey data. The areas of low magnetization are also consistent with hydrothermal deposits identified in video records. These results suggest that low magnetic signals are due to hydrothermal alteration zones where host rocks are

  20. Paleomagnetic and rock magnetic characterization of magnetic anomalies in the Central Iberian Arc (Iberian Peninsula)

    NASA Astrophysics Data System (ADS)

    Villalain, J.; Ayarza, P.; Martinez-Catalan, J. R.; Álvarez-Lobato, F.; Gómez-Barreiro, J.; Suárez Barrios, M.; Torres-López, S.

    2013-12-01

    The Central Iberian Arc is one of the four oroclines delineated by the European Variscan Belt. It is located in NW and Central Iberia and characterized by a conspicuous magnetic response. The most intense magnetic anomaly within this arc is the so called Eastern Galicia Magnetic Anomaly (EGMA; Aller et al., 1994), located in the northern part of Spain and associated to the Lugo-Sanabria dome, an extensional structure in the inner part of arc. The aeromagnetic map of the Iberian Peninsula (Ardizone et al., 1989; Miranda et al., 1989) shows that the EGMA continues to Central Spain and turns back to the Atlantic Ocean, as a broad positive anomaly, delineating a tight fold at the core of the Central Iberian Arc. The source of the EGMA seems to be magnetite-bearing migmatites and inhomogeneous granites formed during an extensive late Carboniferous thermal event triggered by Variscan crustal thickening. These rocks were modeled as a lens-shaped body up to 12 km thick with magnetic susceptibility values between 0.02and 0.03 SI units, that underlie the whole dome extension and continues toward the west of it (Ayarza and Martínez Catalán, 2007). However, this body crops out only in the deepest and northernmost part of the dome, in the Xistral Tectonic Window, and there, only its upper part is accessible. Migmatites and granitoids are abundant along the rest of the anomaly, but their magnetic susceptibility is low. Thus, the source of the magnetic anomaly should be buried there and its nature is unknown. Paleomagnetic and rock magnetic studies in the outcropping rocks responsible for the EGMA have been carried out, adding new constraints to the origin of this anomaly. Rock magnetic analysis as progressive acquisition of IRM, hysteresis loops, thermomagnetic experiments and X-ray indicate that the ferromagnetic fraction is dominated by multidomain magnetite and titanohematite. It is remarkable the unusual high anisotropy of magnetic susceptibility of these rocks, showing

  1. Surface mapping of three components of the lunar magnetic anomaly field: Preliminary results

    NASA Astrophysics Data System (ADS)

    Tsunakawa, H.; Takahashi, F.; Shimizu, H.; Shibuya, H.; Matsushima, M.

    2010-12-01

    Mapping of the lunar magnetic anomaly gives a crucial constraint on the crustal magnetization structure of the Moon. High spatial resolution of the magnetic anomaly map requires low altitude mapping. We have developed a new method for mapping three components of the lunar magnetic anomaly field on the lunar surface using magnetic field observations by a satellite magnetometer. This surface mapping method was applied to the datasets of several lunar magnetic anomaly regions observed by Lunar Prospector and Kaguya. We will report their preliminary results. The radial component of the crustal magnetic field (Br) on the surface can be obtained from the satellite observations at various altitudes through the inversion of a boundary value problem (Tsunakawa et al., in press). In our method, surface Br values are mapped at almost equal interval points, called generalized spiral points. Two horizontal components are calculated at each point from Br values at the adjacent points. Thus we can map the surface values of three components and total intensity of the lunar magnetic anomaly field (Tsunakawa et al., in prep.). We have applied the method to several strong anomaly regions (e.g. Reiner Gamma) observed by Lunar Prospector and Kaguya. Since the observation altitudes are mostly 15-45 km, spatial resolutions are estimated to be 0.5-1 degree. Preliminary results show strong magnetic anomaly fields with intensity peaks of more than 500 nT on the lunar surface.

  2. Determination Gradients of the Earth's Magnetic Field from the Measurements of the Satellites and Inversion of the Kursk Magnetic Anomaly

    NASA Technical Reports Server (NTRS)

    Karoly, Kis; Taylor, Patrick T.; Geza, Wittmann

    2014-01-01

    We computed magnetic field gradients at satellite altitude, over Europe with emphasis on the Kursk Magnetic Anomaly (KMA). They were calculated using the CHAMP satellite total magnetic anomalies. Our computations were done to determine how the magnetic anomaly data from the new ESA/Swarm satellites could be utilized to determine the structure of the magnetization of the Earths crust, especially in the region of the KMA. Since the ten years of 2 CHAMP data could be used to simulate the Swarm data. An initial East magnetic anomaly gradient map of Europe was computed and subsequently the North, East and Vertical magnetic gradients for the KMA region were calculated. The vertical gradient of the KMA was determined using Hilbert transforms. Inversion of the total KMA was derived using Simplex and Simulated Annealing algorithms. Our resulting inversion depth model is a horizontal quadrangle with upper 300-329 km and lower 331-339 km boundaries.

  3. Magnetic anomaly depth and structural index estimation using different height analytic signals data

    NASA Astrophysics Data System (ADS)

    Zhou, Shuai; Huang, Danian; Su, Chao

    2016-09-01

    This paper proposes a new semi-automatic inversion method for magnetic anomaly data interpretation that uses the combination of analytic signals of the anomaly at different heights to determine the depth and the structural index N of the sources. The new method utilizes analytic signals of the original anomaly at different height to effectively suppress the noise contained in the anomaly. Compared with the other high-order derivative calculation methods based on analytic signals, our method only computes first-order derivatives of the anomaly, which can be used to obtain more stable and accurate results. Tests on synthetic noise-free and noise-corrupted magnetic data indicate that the new method can estimate the depth and N efficiently. The technique is applied to a real measured magnetic anomaly in Southern Illinois caused by a known dike, and the result is in agreement with the drilling information and inversion results within acceptable calculation error.

  4. Surveying the South Pole-Aitken basin magnetic anomaly for remnant impactor metallic iron

    USGS Publications Warehouse

    Cahill, Joshua T.S.; Hagerty, Justin J.; Lawrence, David M.; Klima, Rachel L.; Blewett, David T.

    2014-01-01

    The Moon has areas of magnetized crust ("magnetic anomalies"), the origins of which are poorly constrained. A magnetic anomaly near the northern rim of South Pole-Aitken (SPA) basin was recently postulated to originate from remnant metallic iron emplaced by the SPA basin-forming impactor. Here, we remotely examine the regolith of this SPA magnetic anomaly with a combination of Clementine and Lunar Prospector derived iron maps for any evidence of enhanced metallic iron content. We find that these data sets do not definitively detect the hypothesized remnant metallic iron within the upper tens of centimeters of the lunar regolith.

  5. Magnetic anomaly inversion using magnetic dipole reconstruction based on the pipeline section segmentation method

    NASA Astrophysics Data System (ADS)

    Pan, Qi; Liu, De-Jun; Guo, Zhi-Yong; Fang, Hua-Feng; Feng, Mu-Qun

    2016-06-01

    In the model of a horizontal straight pipeline of finite length, the segmentation of the pipeline elements is a significant factor in the accuracy and rapidity of the forward modeling and inversion processes, but the existing pipeline segmentation method is very time-consuming. This paper proposes a section segmentation method to study the characteristics of pipeline magnetic anomalies—and the effect of model parameters on these magnetic anomalies—as a way to enhance computational performance and accelerate the convergence process of the inversion. Forward models using the piece segmentation method and section segmentation method based on magnetic dipole reconstruction (MDR) are established for comparison. The results show that the magnetic anomalies calculated by these two segmentation methods are almost the same regardless of different measuring heights and variations of the inclination and declination of the pipeline. In the optimized inversion procedure the results of the simulation data calculated by these two methods agree with the synthetic data from the original model, and the inversion accuracies of the burial depths of the two methods are approximately equal. The proposed method is more computationally efficient than the piece segmentation method—in other words, the section segmentation method can meet the requirements for precision in the detection of pipelines by magnetic anomalies and reduce the computation time of the whole process.

  6. Investigating tectonic and bathymetric features of the Indian Ocean using MAGSAT magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Sailor, R. V.; Lazarewicz, A. R. (Principal Investigator)

    1982-01-01

    An equivalent source anomaly map and a map of the relative magnetization for the investigation region were produced. Gravimetry, bathymetry, and MAGSAT anomaly maps were contoured in pseudocolor displays. Finally, an autoregressive spectrum estimation technique was verified with synthetic data and shown to be capable of resolving exponential power spectra using small samples of data. Interpretations were made regarding the relationship between MAGSAT data spectra and crustal anomaly spectra.

  7. Simultaneous observations of F2 layer stratification and spread F at postmidnight over a northern equatorial anomaly region

    NASA Astrophysics Data System (ADS)

    Jiang, Chunhua; Yang, Guobin; Deng, Chi; Zhou, Chen; Zhu, Peng; Yokoyama, Tatsuhiro; Song, Huan; Lan, Ting; Ni, Binbin; Zhao, Zhengyu; Zhang, Yuannong

    2015-12-01

    Simultaneous observations of F2 layer stratification and spread F at postmidnight (00:00 LT to 05:00 LT) were carried out on 22, 23, and 28 November 2013, using ionosondes distributed over a northern equatorial anomaly region at three specific locations, i.e., Puer (PUR, 22.7°N, 101.05°E, dip latitude 12.9°N), Chiang Mai (CMU, 18.8°N, 98.9°E, dip latitude 9.04°N), and Chumphon (CPN, 10.7°N, 99.4°E, dip latitude 0.93°N). The results show that both the PUR and CMU stations observed the F2 layer stratification at postmidnight in the Northern Hemisphere, frequently accompanied with gravity waves (the periods~30-100 min). It is reported that F2 layer stratification at postmidnight can be observed in the Northern Hemisphere for the first time. It is suggested that the thermospheric neutral wind triggered by gravity waves strongly contribute to the altitude dependence of the combined vertical plasma velocity, which consequently poses significant impacts on the occurrence of the low-latitude F2 layer stratification at postmidnight. In addition, the spread F other than F2 layer stratification was observed at the CPN station located at the geomagnetic equator, suggesting that smaller geomagnetic inclination tend to inhibit the postmidnight F2 layer stratification in the equatorial region. Furthermore, on 23 November 2013 a good correlation was identified between the F2 layer stratification at PUR and the spread F at both CMU and CPN, possibly due to that the large-scale gravity waves originating at middle latitudes contribute to the nighttime spread F observed in the low-latitude and equatorial regions.

  8. Magnetic Structure of Backarc Spreading Axis with Hydrothermal Vents; the Southern Mariana Trough

    NASA Astrophysics Data System (ADS)

    Fujii, M.; Okino, K.; Mochizuki, N.; Honsho, C.; Szitkar, F.; Dyment, J.; Nakamura, K.

    2012-12-01

    Seafloor hydrothermal systems are important in relation to global heat and chemical fluxes as well as habitat of microbial communities. The substantial variation of hydrothermal systems in various tectonic settings has important implications for the magnetic structure of oceanic crust. It has been very difficult to detect the geophysical signature of hydrothermal systems from sea-surface data because the small scale of hydrothermal systems is below the limit of resolution. The advance of near-bottom survey methods using a submersible, deep-tow, ROV and AUV has made possible high-resolution geophysical mapping around hydrothermal areas. Near-bottom magnetic surveys can provide direct information on the magnetization of the shallower oceanic crust, implying hydrothermal alteration both in active and fossil vent sites. Near-bottom three component magnetic measurements on submersible Shinkai 6500 were carried out at hydrothermal fields in the Southern Mariana Trough, a slow spreading backarc basin. Fourteen dive surveys were conducted during cruises YK11-10 and YK10-11. We investigated the magnetic structure of four hydrothermal systems located at on- and off-axis to clarify how the geophysical and geological setting controls the fluid circulation at small scale. Recent researches at slow spreading ridges showed a relationship between crustal magnetic structure and host rock around hydrothermal vents (e.g. Tivey and Dyment, 2010), but no observation at backarc spreading axis has been reported so far. We carefully corrected the effects of induced and permanent magnetizations of the submersible by applying the method of Isezaki [1986] with dumped least-square method (Honsho et al., 2009). After subtracting the IGRF from the corrected observed data, we obtained geomagnetic vector anomalies in geographical coordinate. For three transects of the axis, we applied three methods; 2D inversion technique (Parker and Huestis, 1972), 2D forward modeling technique (Honsho et al

  9. Magnetic Anomalies of the Fennoscandian Shield on a 2km resolution grid

    NASA Astrophysics Data System (ADS)

    Korhonen, Juha V.; Aaro, Sven; Reidar Skilbrei, Jan; All, Tarmo

    2010-05-01

    Joint magnetic anomaly grid of the Fennoscandian Shield was released 2002, smoothed and used as data for the WDMAM2007. In comparison with MF5 this grid showed superior characteristics to other sets. The data will be released as a 2 km resolution grid for the WDMAM2011 with eventual updates of anomaly levels.

  10. High-resolution magnetic signature of active hydrothermal systems in the back-arc spreading region of the southern Mariana Trough

    NASA Astrophysics Data System (ADS)

    Fujii, Masakazu; Okino, Kyoko; Honsho, Chie; Dyment, Jerome; Szitkar, Florent; Mochizuki, Nobutatsu; Asada, Miho

    2015-05-01

    High-resolution vector magnetic measurements were performed on five hydrothermal vent fields of the back-arc spreading region of the southern Mariana Trough using Shinkai 6500, a deep-sea manned submersible. A new 3-D forward scheme was applied that exploits the surrounding bathymetry and varying altitudes of the submersible to estimate absolute crustal magnetization. The results revealed that magnetic-anomaly-derived absolute magnetizations show a reasonable correlation with natural remanent magnetizations of rock samples collected from the seafloor of the same region. The distribution of magnetic-anomaly-derived absolute magnetization suggests that all five andesite-hosted hydrothermal fields are associated with a lack of magnetization, as is generally observed at basalt-hosted hydrothermal sites. Furthermore, both the Pika and Urashima sites were found to have their own distinct low-magnetization zones, which could not be distinguished in magnetic anomaly data collected at higher altitudes by autonomous underwater vehicle due to their limited extension. The spatial extent of the resulting low magnetization is approximately 10 times wider at off-axis sites than at on-axis sites, possibly reflecting larger accumulations of nonmagnetic sulfides, stockwork zones, and/or alteration zones at the off-axis sites.

  11. Apparatus and method for detecting a magnetic anomaly contiguous to remote location by SQUID gradiometer and magnetometer systems

    DOEpatents

    Overton, W.C. Jr.; Steyert, W.A. Jr.

    1981-05-22

    A superconducting quantum interference device (SQUID) magnetic detection apparatus detects magnetic fields, signals, and anomalies at remote locations. Two remotely rotatable SQUID gradiometers may be housed in a cryogenic environment to search for and locate unambiguously magnetic anomalies. The SQUID magnetic detection apparatus can be used to determine the azimuth of a hydrofracture by first flooding the hydrofracture with a ferrofluid to create an artificial magnetic anomaly therein.

  12. Origin of the Eastern Galicia Magnetic Anomaly (NW Spain). Implications for the Origin of Magnetic Anomalies in the Central Iberian Arc

    NASA Astrophysics Data System (ADS)

    Ayarza, P.; Martinez-Catalan, J. R.; Villalain, J. J.; Alvarez Lobato, F.; Martin Paramio, M.; Rodriguez Gómez, S.; Sanz López, M.

    2015-12-01

    The aeromagnetic map of Iberia features outstanding anomalies that have been key to define the Central Iberian Arc, a late-orogenic orocline in the western part of the Variscan belt. The most studied of them is the EGMA (Eastern Galicia Magnetic Anomaly), which follows the Lugo-Sanabria extensional dome and is probably associated with it. Among the existing models of this anomaly, those relating it with magnetite-rich inhomogeneous granites and migmatites formed during late-Variscan extension seem to be more plausible ones. However, this and other interpretations involving deep-seated mafic/ultramafic bodies lack resolution as they are based on the aeromagnetic dataset. New ground magnetic data have been acquired in the northern part of the Xistral Tectonic Window, at the core of the Lugo dome where its deepest rocks crop out. The resulting maps show that the anomaly ranges ~1000 nT (vs. 190 nT on the aeromagnetic map) and that the most important maxima lie on top of extensional detachments located on high-grade metasediments or inhomogeneous granites. 2D forward modeling indicates that the magnetization is carried by upper Neoproterozoic and early Cambrian metasediments, partially melted during late-Variscan high-T and low-P metamorphic event linked to the extensional collapse. Furthermore, the anomaly maxima are spatially related with detachments, where the metasediments were strongly sheared. Therefore, the P-T, redox and fluid pressure conditions necessary for the formation of magnetite seem related with the extensional process and the dynamics of its structures. Many magnetic anomalies of the Central Iberian Arc lie on top of Variscan extensional domes and accordingly may have a similar origin. Special attention is paid to the Gredos Magnetic Anomaly, coincident with the batholith of the same name. Preliminary magnetic mapping and modeling indicate that the anomaly is previous to the intrusion of the Jurassic Alentejo-Plasencia dyke and to the tardi

  13. Regional Mapping of the Lunar Crustal Magnetic Field: Correlation of Strong Anomalies with Curvilinear Albedo Markings

    NASA Technical Reports Server (NTRS)

    Hood, L. L.; Yingst, A.; Zakharian, A.; Lin, R. P.; Mitchell, D. L.; Halekas, J.; Acuna, M. H.; Binder, A. B.

    2000-01-01

    Using high-resolution regional Lunar Prospector magnetometer magnetic field maps, we report here a close correlation of the strongest individual crustal anomalies with unusual curvilinear albedo markings of the Reiner Gamma class.

  14. Calculation of gravity and magnetic anomalies along profiles with end corrections and inverse solutions for density and magnetization

    USGS Publications Warehouse

    Cady, John W.

    1977-01-01

    A computer program is presented which performs, for one or more bodies, along a profile perpendicular to strike, both forward calculations for the magnetic and gravity anomaly fields and independent gravity and magnetic inverse calculations for density and susceptibility or remanent magnetization.

  15. High-altitude structure of the magnetic anomalies using the gradient measurements in stratosphere

    NASA Astrophysics Data System (ADS)

    Tsvetkov, Yu.; Rotanova, N.; Belikova, M.

    2003-04-01

    HIGH-ALTITUDE STRUCTURE OF THE MAGNETIC ANOMALIES USING THE GRADIENT MEASUREMENTS IN STRATOSPHERE Yu. Tsvetkov, N. ROTANOVA, M. Belikova Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS, Troitsk, Moscow Region, 142190, Russia rotanova@izmiran.rssi.ru/FAX: +7-095-3340124 Method of the recalculation of the anomaly magnetic field over the range of the altitudes of 20-40 km is suggested. Technique is based on the experimental data of the anomaly magnetic field, its vertical gradient and the gradient increment along vertical line, obtained from the aerostat gradient magnetic surveys in stratosphere. The high-altitude structure of the magnetic anomalies, obtained for the Baikal region has been constructed. These results were used to obtain the estimations of the deep magnetic sources. The numerous values of the low boundary of the sources are 30-35 km. These estimations of the depth coincide with the ones, obtained from the results of the spectral analysis of the same magnetic anomalies.

  16. Decay of natural remanent magnetization of oceanic basalt on the back-arc spreading axis of the southern Mariana

    NASA Astrophysics Data System (ADS)

    Mochizuki, N.; Nogi, Y.; Asada, M.; Yoshikawa, S.; Okino, K.

    2012-12-01

    Magnetic anomaly high on the spreading axis is a well-known character of the magnetic anomalies in the ocean, which is possibly related to magnetization intensity reduction of oceanic basalt due to alteration (low-temperature oxidation of titanomagnetite). For a better understanding of natural remanent magnetization (NRM) of oceanic basalt, we studied rock-magnetic property of basaltic rocks in the back-arc spreading axis in the southern Mariana Trough. One to four meter cores were drilled from the seafloor using a Boring Machine System (BMS) in the cruise of TAIGA project (Taiga10M). Block samples were also collected during the dives of SHINKAI6500 in the cruise YK10-11. One-inch specimens drilled from the samples were used for rock-magnetic measurements. NRM intensities of these specimens show a clear decrease within 2 km of the ridge axis. Progressive thermal demagnetizations of NRM show that dominant blocking-temperature components are 200-300 and 500-575 °C. Specimens from the ridge axis typically show low blocking-temperature components. On the other hand, specimens collected at 2-5 km distance from the ridge axis show both low and high blocking-temperature components. Alternating field demagnetizations of NRM, anhysteresis remanent magnetization (ARM) and isothermal remanent magnetization (IRM) indicate that low blocking-temperature components have lower coercivities (<40 mT) while high blocking-temperature components possibly correspond to higher coercivities. These data suggest that high blocking-temperature component is carried by titanomaghemite (or fine magnetite). On the basis of these results, the low blocking-temperature components are considered to be primary thermoremanent magnetization (TRM). The high blocking-temperature components are chemical remanent magnetization (CRM) acquired during low-temperature alteration which had completed within 2 km of the ridge axis. The NRM intensity shows a decrease within 2 km of the ridge axis, which is

  17. Surface vector mapping of magnetic anomalies over the Moon using Kaguya and Lunar Prospector observations

    NASA Astrophysics Data System (ADS)

    Tsunakawa, Hideo; Takahashi, Futoshi; Shimizu, Hisayoshi; Shibuya, Hidetoshi; Matsushima, Masaki

    2015-06-01

    We have provided preliminary global maps of three components of the lunar magnetic anomaly on the surface applying the surface vector mapping (SVM) method. The data used in the present study consist of about 5 million observations of the lunar magnetic field at 10-45 km altitudes by Kaguya and Lunar Prospector. The lunar magnetic anomalies were mapped at 0.2° equi-distance points on the surface by the SVM method, showing the highest intensity of 718 nT in the Crisium antipodal region. Overall features on the SVM maps indicate that elongating magnetic anomalies are likely to be dominant on the Moon except for the young large basins with the impact demagnetization. Remarkable demagnetization features suggested by previous studies are also recognized at Hertzsprung and Kolorev craters on the farside. These features indicate that demagnetized areas extend to about 1-2 radii of the basins/craters. There are well-isolated central magnetic anomalies at four craters: Leibnitz, Aitken, Jules Verne, and Grimaldi craters. Their magnetic poles through the dipole source approximation suggest occurrence of the polar wander prior to 3.3-3.5 Ga. When compared with high-albedo markings at several magnetic anomalies such as the Reiner Gamma anomalies, three-dimensional structures of the magnetic field on/near the surface are well correlated with high-albedo areas. These results indicate that the global SVM maps are useful for the study of the lunar magnetic anomalies in comparison with various geological and geophysical data.

  18. Statistical averaging of marine magnetic anomalies and the aging of oceanic crust.

    USGS Publications Warehouse

    Blakely, R.J.

    1983-01-01

    Visual comparison of Mesozoic and Cenozoic magnetic anomalies in the North Pacific suggests that older anomalies contain less short-wavelength information than younger anomalies in this area. To test this observation, magnetic profiles from the North Pacific are examined from crust of three ages: 0-2.1, 29.3-33.1, and 64.9-70.3Ma. For each time period, at least nine profiles were analyzed by 1) calculating the power density spectrum of each profile, 2) averaging the spectra together, and 3) computing a 'recording filter' for each time period by assuming a hypothetical seafloor model. The model assumes that the top of the source is acoustic basement, the source thickness is 0.5km, and the time scale of geomagnetic reversals is according to Ness et al. (1980). The calculated power density spectra of the three recording filters are complex in shape but show an increase of attenuation of short-wavelength information as the crust ages. These results are interpreted using a multilayer model for marine magnetic anomalies in which the upper layer, corresponding to pillow basalt of seismic layer 2A, acts as a source of noise to the magnetic anomalies. As the ocean crust ages, this noisy contribution by the pillow basalts becomes less significant to the anomalies. Consequently, magnetic sources below layer 2A must be faithful recorders of geomagnetic reversals.-AuthorPacific power density spectrum

  19. Magnetic Anomalies Within Lunar Impact Basins: Constraints on the History of the Lunar Dynamo

    NASA Astrophysics Data System (ADS)

    Richmond, N. C.; Hood, L. L.

    2011-12-01

    Previous work has shown that lunar crustal magnetization has a combination of origins including shock remanent magnetization in transient magnetic fields and thermoremanent magnetization in a steady core dynamo magnetic field (e.g., Hood and Artemieva, Icarus, 2008; Richmond and Hood, JGR, 2008; Garrick-Bethell et al., Science, 2009; Hood, Icarus, 2011). In particular, magnetic anomalies within the interiors of lunar impact basins and large craters provide a potentially valuable means of constraining the history of the former dynamo (Halekas et al., MAPS, 2003; Hood, 2011). These anomalies likely have a thermoremanent origin owing to high subsurface temperatures reached at the time of impact and therefore require a long-lived, steady magnetic field to explain their magnetization. Central anomalies have previously been confirmed to be present using Lunar Prospector magnetometer (LP MAG) data within several Nectarian-aged basins (Moscoviense, Mendel-Rydberg, Crisium, and Humboldtianum), implying that a dynamo existed during this lunar epoch (Hood, 2011). Here, we further analyze low altitude LP MAG data for several additional basins, ranging in age from Nectarian to Imbrian. Results indicate that magnetic anomalies with a probable basin-related origin are present within at least two additional Nectarian-aged basins (Serenitatis and Humorum) and one Imbrian-aged basin (Schrodinger). No discernible anomalies are present within the largest Imbrian-aged basins, Imbrium and Orientale. While there is uncertainty regarding the age of the Schrodinger basin, it has been reported to be slightly more recent than Imbrium (Wilhelms, 1984). Our initial interpretation is therefore that a dynamo likely existed during the Imbrian epoch. The absence of anomalies within Imbrium and Orientale can be explained by insufficient conditions for acquisition of strong magnetization (e.g., inadequate concentrations of efficient remanence carriers) following these relatively large impacts.

  20. Direct Observations of Magnetic Anomalies on the Lunar Surface under Varying Solar Wind Conditions

    NASA Astrophysics Data System (ADS)

    Vorburger, A.; Wurz, P.; Barabash, S.; Wieser, M.; Futaana, Y.; Holmström, M.; Bhardwaj, A.; Dhanya, M. B.; Sridharan, R.; Asamura, K.

    2012-04-01

    In contrast to Earth, the Moon does not have a global dipolar magnetic field. Since the first lunar landing with Apollo 11, we know, though, that localised magnetic fields exist on the lunar surface. Measurements conducted by the Lunar Prospector magnetometer and electron reflectometer suggested that these localised magnetic fields are able to deflect the impinging solar wind in favourable cases (Lin et al., Science 1998). Magnetohydrodynamic simulations support the implication that mini-magnetospheres are formed above the locations of strong localised magnetic fields and can hold off the impinging solar wind (Harnett and Winglee, JGR 2002). Analysis of magnetic field data from Lunar Prospector of the Reiner Gamma anomaly region showed that the distortion of the magnetic field of this anomaly strongly depends on the impinging solar wind parameters, which was interpreted that the size and shape of the mini-magnetosphere changed with the solar wind parametes (Kurata et al., GRL 2005). Wieser et al., GRL 2010 showed that SARA, the Sub-KeV Atom Analyzer on board Chandrayaan-1, is able to detect an ENA image of the mini-magnetosphere in the measured energetic neutral atom flux. Here we analysed all orbits where CENA, the Chandrayaan-1 Energetic Neutral Analyzer, recorded data when a magnetic anomaly was in CENA's field-of-view. Our goal was to determine if 1) a signature of the magnetic anomaly is always visible in the ENA signal and if 2) there is a correlation between the solar wind dynamic pressure, the solar wind magnetic field, the local magnetic field strength and the reduction in the reflected ENA flux. Our results show that for the simplest case, i.e., the Gerasimovich anomaly, there is indeed a clear correlation between the shielding efficiency, the magnetic field strength and the solar wind dynamic pressure. For the other observed magnetic anomalies, for which the magnetic fields are not only weaker but also spatially more variable than that of the

  1. Reduced to pole long-wavelength magnetic anomalies of Africa and Europe

    NASA Technical Reports Server (NTRS)

    Olivier, R.; Hinze, W. J.; Vonfrese, R. R. B.

    1985-01-01

    To facilitate analysis of the tectonic framework for Africa, Europe and adjacent marine areas, MAGSAT scalar anomaly data are differentially reduced to the pole and compared to regional geologic information and geophysical data including surface free-air gravity anomaly data upward continued to satellite elevation (350 km) on a spherical Earth. Comparative analysis shows magnetic anomalies correspond with both ancient as well as more recent Cenozoic structural features. Anomalies associated with ancient structures are primarily caused by intra-crustal lithologic variations such as the crustal disturbance associated with the Bangui anomaly in west-central Africa. Anomalies correlative with Cenozoic tectonic elements appear to be related to Curie isotherm perturbations. A possible example of the latter is the well-defined trend of magnetic minima that characterize the Alphine orogenic belt from the Atlas mountains to Eurasia. In contrast, a well-defined magnetic satellite minimum extends across the stable craton from Finland to the Ural mountains. Prominent magnetic maxima characterize the Arabian plate, Iceland, the Kursk region of the central Russian uplift, and generally the Precambrian shields of Africa.

  2. Reduced to Pole Long-wavelength Magnetic Anomalies of Africa and Europe

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator); Olivier, R.

    1984-01-01

    To facilitate analysis of the tectonic framework for Africa, Europe and adjacent marine areas, MAGSAT scalar anomaly data are differentially reduced to the pole and compared to regional geologic information and geophysical data including surface free-air gravity anomaly data upward continued to satellite elevation (350 km) on a spherical Earth. Comparative analysis shows magnetic anomalies correspond with both ancient as well as more recent Cenozoic structural features. Anomalies associated with ancient structures are primarily caused by intra-crustal lithologic variations such as the crustal disturbance associated with the Bangui anomaly in west-central Africa. Anomalies correlative with Cenozoic tectonic elements appear to be related to Curie isotherm perturbations. A possible example of the latter is the well-defined trend of magnetic minima that characterize the Alpine orogenic belt from the Atlas mountains to Eurasia. In contrast, a well-defined magnetic satellite minimum extends across the stable craton from Finland to the Ural mountains. Prominent magnetic maxima characterize the Arabian plate, Iceland, the Kursk region of the central Russian uplift, and generally the Precambrian shields of Africa.

  3. Magnetic anomalies in east Pacific using MAGSAT data

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A. (Principal Investigator)

    1983-01-01

    Methods for solving problems encountered in separating the core field from the crustal field are summarized as well as those methods developed for inverting total magnetic field data to obtain source functions for oceanic areas. Accounting for magnetization contrasts and the magnetization values measured in rocks of marine origin are also discussed.

  4. Weak extremely-low-frequency magnetic field-induced regeneration anomalies in the planarian, Dugesia tigrina

    SciTech Connect

    Jenrow, K.A.; Smith, C.H.; Liboff, A.R.

    1996-12-31

    The authors recently reported that cephalic regeneration in the planarian Dugesia tigrina was significantly delayed in populations exposed continuously to combined parallel DC and AC magnetic fields. This effect was consistent with hypotheses suggesting an underlying resonance phenomenon. The authors report here, in a parallel series of investigations on the same model system, that the incidence of regeneration anomalies presenting as tumor-like protuberances also increases significantly (P < .001) in association with exposure to weak 60 Hz magnetic fields, with peak intensities ranging between 1.0 and 80.0 {micro}T. These anomalies often culminate in the complete disaggregation of the organism. Similar to regeneration rate effects, the incidence of regeneration anomalies is specifically dependent upon the planaria possessing a fixed orientation with respect to the applied magnetic field vectors. However, unlike the regeneration rate effects, the AC magnetic field alone, in the absence of any measurable DC field, is capable of producing these anomalies. Moreover, the incidence of regeneration anomalies follows a clear dose-response relationship as a function of AC magnetic field intensity, with the threshold for induced electric field intensity estimated at 5 {micro} V/m. The addition of either 51.1 or 78.4 {micro}T DC magnetic fields, applied in parallel combination with the AC field, enhances the appearance of anomalies relative to the 60 Hz AC field alone, but only at certain AC field intensities. Thus, whereas the previous study of regeneration rate effects appeared to involve exclusively resonance interactions, the regeneration anomalies reported here appear to result primarily from Faraday induction coupling.

  5. The mineralogy of global magnetic anomalies. [rock magnetic signatures and MAGSAT geological, and gravity correlations in West Africa

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E. (Principal Investigator)

    1982-01-01

    Problems with the Curie balance, which severely hindered the acquisition of data, were rectified. Chemical analytical activities are proceeding satisfactorily. The magnetization characteristics of metamorphic suites were analyzed and susceptibility data for a wide range of metamorphic and igneous rocks. These rock magnetic signatures are discussed as well as the relationships between geology, gravity and MAGSAT anomalies of West Africa.

  6. Spherical earth gravity and magnetic anomaly analysis by equivalent point source inversion

    NASA Technical Reports Server (NTRS)

    Von Frese, R. R. B.; Hinze, W. J.; Braile, L. W.

    1981-01-01

    To facilitate geologic interpretation of satellite elevation potential field data, analysis techniques are developed and verified in the spherical domain that are commensurate with conventional flat earth methods of potential field interpretation. A powerful approach to the spherical earth problem relates potential field anomalies to a distribution of equivalent point sources by least squares matrix inversion. Linear transformations of the equivalent source field lead to corresponding geoidal anomalies, pseudo-anomalies, vector anomaly components, spatial derivatives, continuations, and differential magnetic pole reductions. A number of examples using 1 deg-averaged surface free-air gravity anomalies of POGO satellite magnetometer data for the United States, Mexico, and Central America illustrate the capabilities of the method.

  7. Soil Magnetism and Magnetic Anomalies at the Marshall's Pen Archaeological Site, Mandeville, Jamaica

    NASA Astrophysics Data System (ADS)

    Figueroa, E.; Sternberg, R. S.; Delle, J. A.; Lawrence, N. D.; McAdoo, B. G.; Savina, M. E.

    2002-05-01

    Marshall's Pen, a 1000-acre parcel of land in Mandeville, Jamaica, underlain by limestone bedrock and bauxite soils, served as a coffee plantation in the early 19th century. Two to three hundred slaves of African descent worked the plantation from AD 1802 until slavery was abolished in Jamaica in 1838. The goal of the archaeological program at Marshall's Pen is to complement what little is known about Jamaican slave society from the historical record. Geophysical prospection was conducted at Marshall's Pen by ten undergraduate students as part of a Keck Geology Consortium project in the summer of 1999. In the slaves' village consisting of living and domestic labor areas, G858 cesium vapor magnetometer readings were taken every 0.1 seconds along 49 profiles, each 50 m long and spaced 1 meter apart, and magnetic susceptibility readings were taken at 1-meter intervals. Seven significant magnetic anomalies (up to 100 nT peak-to-peak) were detected in the village. Two of these were found to be caused by a buried machete and an iron woodworking tool. Three anomalies were associated with a large area of black, burned soil. Archaeological testing in this area produced partially carbonized seeds, charcoal, ceramics that were smudged after manufacture, and cutlery; this evidence suggests a domestic kitchen area. In situ susceptibility readings were zero on bedrock and low on the bauxite soils. Susceptibility readings generally correlated with the magnetics, to values as high as 50 (x 10-6, volume specific SI) in the ``kitchen'' area, suggesting a source in the susceptibility contrast for these magnetic anomalies. Soil samples were collected from the bauxite outside the village, and from the village area in the summer of 2001; ten village sites were sampled away from the kitchen area, and four from the kitchen area. Five samples from each site were boxed, weighed, and measured for laboratory susceptibility measurements. Eleven samples outide the village had a geometric mean

  8. Scalar magnetic anomaly maps of Earth derived from POGO and Magsat data

    NASA Technical Reports Server (NTRS)

    Arkani-Hamed, Jafar; Langel, Robert A.; Purucker, Mike

    1994-01-01

    A new Polar Orbit Geophysical Observatory (POGO) scalar magnetic anomaly map at 400 km altitude is presented which consists of spherical harmonics of degree 15-60. On the basis of the common features of this map with two new Magsat anomaly maps, dawn and dusk, two scalar magnetic anomaly maps of the Earth are presented using two selection criteria with different levels of stringency. These selection criteria suppress the noncrustal components of the original maps by different amounts. The more stringent selection criteria seek to eliminate as much contamination as possible, at the expense of suppressing some anomaly signal. This map is represented by spherical harmonics of degree 15-60. The less stringent selection criteria seek to retain as much crustal signal as possible, at the expense of also retaining some contaminating fields. This map is represented by spherical harmonics of degree 15-65. The resulting two maps are highly correlated with degree correlation coefficients greater than 0.8.

  9. Intermediate-wavelength magnetic anomaly field of the North Pacific and posible source distributions

    NASA Technical Reports Server (NTRS)

    Labrecque, J. L.; Cande, S. C.; Jarrard, R. D.

    1985-01-01

    A technique that eliminates external field sources and the effects of strike aliasing was used to extract from marine survey data the intermediate wavelength magnetic anomaly field for (B) in the North Pacific. A strong correlation exists between this field and the Magsat field although a directional sensitivity in the Magsat field can be detected. The intermediate wavelength field is correlated to tectonic features. Island arcs appear as positive anomalies of induced origin likely due to variations in crustal thickness. Seamount chains and oceanic plateaus also are manifested by strong anomalies. The primary contribution to many of these anomalies appears to be due to a remanent magnetization. The source parameters for the remainder of these features are presently unidentified ambiguous. Results indicate that the sea surface field is a valuable source of information for secular variation analysis and the resolution of intermediate wavelength source parameters.

  10. The intermediate wavelength magnetic anomaly field of the north Pacific and possible source distributions

    NASA Technical Reports Server (NTRS)

    Labrecque, J. L.; Cande, S. C.; Jarrard, R. D. (Principal Investigator)

    1983-01-01

    A technique that eliminates external field sources and the effects of strike aliasing was used to extract from marine survey data the intermediate wavelength magnetic anomaly field for (B) in the North Pacific. A strong correlation exists between this field and the MAGSAT field although a directional sensitivity in the MAGSAT field can be detected. The intermediate wavelength field is correlated to tectonic features. Island arcs appear as positive anomalies of induced origin likely due to variations in crustal thickness. Seamount chains and oceanic plateaus also are manifested by strong anomalies. The primary contribution to many of these anomalies appears to be due to a remanent magnetization. The source parameters for the remainder of these features are presently unidentified ambiguous. Results indicate that the sea surface field is a valuable source of information for secular variation analysis and the resolution of intermediate wavelength source parameters.

  11. Application of Magsat lithospheric modeling in South America. Part 1: Processing and interpretation of magnetic and gravity anomaly data

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Braile, L. W.; Vonfrese, R. R. B. (Principal Investigator); Keller, G. R.; Lidiak, E. G.

    1984-01-01

    Scalar magnetic anomaly data from MAGSAT, reduced to vertical polarization and long wavelength pass filtered free air gravity anomaly data of South America and the Caribbean are compared to major crustal features. The continental shields generally are more magnetic than adjacent basins, oceans and orogenic belts. In contrast, the major aulacogens are characterized by negative anomalies. Spherical earth magnetic modeling of the Amazon River and Takatu aulacogens in northeastern South America indicates a less magnetic crust associated with the aulacogens. Spherical earth modeling of both positive gravity and negative magnetic anomalies observed over the Mississippi Embayment indicate the presence of a nonmagnetic zone of high density material within the lower crust associated with the aulacogen. The MAGSAT scalar magnetic anomaly data and available free air gravity anomalies over Euro-Africa indicate several similar relationships.

  12. MAGSAT investigation of crustal magnetic anomalies in the eastern Indian Ocean

    NASA Technical Reports Server (NTRS)

    Sailor, R. V.; Lazarewicz, A. R.

    1983-01-01

    Crustal magnetic anomalies in a region of the eastern Indian Ocean were studied using data from NASA's MAGSAT mission. The investigation region (0 deg to 50 deg South, 75 to 125 deg East) contains several important tectonic features, including the Broken Ridge, Java Trench, Ninetyeast Ridge, and Southeast Indian Ridge. A large positive magnetic anomaly is associated with the Broken Ridge and smaller positive anomalies correlate with the Ninetyeast Ridge and western Australia. Individual profiles of scalar data (computed from vector components) were considered to determine the overall data quality and resolution capability. A set of MAGSAT ""Quiet-Time'' data was used to compute an equivalent source crustal magnetic anomaly map of the study region. Maps of crustal magnetization and magnetic susceptibility were computed from the equivalent source dipoles. Gravity data were used to help interpretation, and a map of the ratio of magnetization to density contrasts was computed using Poisson's relation. The results are consistent with the hypothesis of induced magnetization of a crustal layer having varying thickness and composition.

  13. Why are There So Few Magnetic Anomalies in Martian Lowlands and Basins?

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.; Aharonson, Oded; Banerdt, W. Bruce; Dombard, Andrew J.; Frey, Herbert V.; Golombek, Matthew P.; Hauck, Steven A., II; Head, James W., III; Johnson, Catherine L.; McGovern, Patrick J.

    2003-01-01

    The discovery of large areas of strongly magnetized crust on Mars [1,2] provides important information on the timing of both crustal and deeper interior processes on that planet. Critical to an understanding of that timing, as well as to the processes that have contributed to the magnetization and demagnetization of crustal materials, is the geographical distribution of magnetic anomalies discernible from spacecraft orbit. The paucity of resolved magnetic anomalies in the northern lowlands and within and surrounding the best-preserved major impact basins has been noted since the crustal field was first globally mapped [1], but no straightforward explanation of that full pattern has yet been offered. Here we suggest that ancient hydrothermal alteration of magnetic carriers in Martian lowlands and basins may have contributed to the magnetization distribution observed today.

  14. On the origin of magnetic a.c. susceptibility non-SRT anomalies in intermetallic compounds

    SciTech Connect

    Bartolome, J.; Garcia, L.M.; Lazaro, F.J.; Grincourt, Y.; Fuente, L.G. de la; Francisco, C. de; Munoz, J.M.; Fruchart, D.

    1994-03-01

    The anomaly detected in the magnetic a.c. susceptibility of many intermetallic compounds between 100 and 300 K, and in particular in Nd{sub 2}Fe{sub 14}B at 220 K, has been induced in a controlled manner by thermal annealing. The anomaly has been interpreted in terms of thermal activated processes of defects imposing their dynamical behavior on the domain walls coupled to them, thus solving the controversy on its origin.

  15. A review of problems and progress in studies of satellite magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Mayhew, M. A.; Johnson, B. D.; Wasilewski, P. J.

    1985-01-01

    A review is conducted of studies performed during the Magsat project. The obtained data are considered, taking into account questions of data availability, aspects of orbit attitude determination, ionospheric noise, a field model, and an anomaly field presentation. Models for interpretation are discussed, giving attention to forward modeling, and equivalent layer inverse modeling. In an evaluation of rock property constraints, the magnetic bottom is discussed along with Curie points, metamorphism and magnetization, and the direction of magnetization.

  16. Modeling the Solar Wind Plasma Interaction with Gerasimovich Magnetic Anomaly on the Moon

    NASA Astrophysics Data System (ADS)

    Fatemi, S.; Lue, C.; Holmstrom, M.; Wieser, M.; Barabash, S.

    2014-12-01

    We study the solar wind plasma interaction with Gerasimovich magnetic anomaly on the Moon. We use a three-dimensional hybrid model of plasma and an empirical model of magnetic anomalies. We examine the effects of low and high dynamic pressures on this interaction while the Gerasimovich magnetic anomaly is located at nearly 30o and 60o solar zenith angles. We find that for the low dynamic pressure the crustal fields deflect the solar wind plasma around and form a plasma void at very close distances to the Moon (below 20 km above the surface). This is while during the high dynamic pressure the plasma void disappears and the solar wind plasma is less deflected. The deflection is associated with an electrostatic potential difference of nearly 250 and 150 V on the lunar surface during the low and high dynamic pressures, respectively, which are consistent with the observations.

  17. Gravity and magnetic anomaly modeling and correlation using the SPHERE program and Magsat data

    NASA Technical Reports Server (NTRS)

    Braile, L. W.; Hinze, W. J. (Principal Investigator); Vonfrese, R. R. B.

    1980-01-01

    The spherical Earth inversion, modeling, and contouring software were tested and modified for processing data in the Southern Hemisphere. Preliminary geologic/tectonic maps and selected cross sections for South and Central America and the Caribbean region are being compiled and as well as gravity and magnetic models for the major geological features of the area. A preliminary gravity model of the Andeas Beniff Zone was constructed so that the density columns east and west of the subducted plates are in approximate isostatic equilibrium. The magnetic anomaly for the corresponding magnetic model of the zone is being computed with the SPHERE program. A test tape containing global magnetic measurements was converted to a tape compatible with Purdue's CDC system. NOO data were screened for periods of high diurnal activity and reduced to anomaly form using the IGS-75 model. Magnetic intensity anomaly profiles were plotted on the conterminous U.S. map using the track lines as the anomaly base level. The transcontinental magnetic high seen in POGO and MAGSAT data is also represented in the NOO data.

  18. Craton vs. rift uppermost mantle contributions to magnetic anomalies in the United States interior

    NASA Astrophysics Data System (ADS)

    Friedman, S. A.; Feinberg, J. M.; Ferré, E. C.; Demory, F.; Martín-Hernández, F.; Conder, J. A.; Rochette, P.

    2014-06-01

    The interpretation of satellite magnetic information (Magsat, Oersted, CHAMP, Swarm) requires the understanding of the mineralogy of crustal and mantle sources. Also, spectral analysis of magnetic data over forearcs and cratons calls for upper mantle contribution. The prospect of such a contribution contradicts the view that the mantle is too hot and its magnetism is too weak to influence magnetic anomalies. Here we examine the rock magnetic properties of fresh mantle xenoliths from four settings across the United States: phlogopite-spinel dunites from the Bearpaw Mountains, Montana, and lherzolites/harzburgites from San Carlos, Arizona; Kilbourne Hole, New Mexico; and Knippa, Texas. Paleomagnetic results show single-component natural remanent magnetizations (NRMs), which, combined with optical and secondary electron microscopy support the lack of post-eruption alteration and absence of host-rock contamination. The NRM carriers include magnetite at Bearpaw Mountain and San Carlos, and pyrrhotite at Kilbourne Hole and Knippa. These four areas show continental crust of distinct thicknesses and various geotherms. The potential mantle contribution to magnetic anomalies is forward modeled using crustal thickness, current geotherm and average magnetic properties of xenoliths. The San Carlos and Kilbourne Hole mantle, situated near the Rio Grande Rift is too hot and its magnetism is too weak to contribute to anomalies. The sulfide-dominated assemblage at Knippa does not support magnetization at mantle depths. In contrast, the Bearpaw Mountains combine a relatively cold geotherm (craton) and abundance of magnetite formed at mantle depth. This cratonic mantle, metasomatized by fluids from the Farallon plate, may contribute to long wavelength magnetic anomalies.

  19. The Smoking Gun: Remanent Magnetic Anomalies on Mars and the Formation of the Crustal Dichotomy via Giant Impact

    NASA Astrophysics Data System (ADS)

    Dombard, A. J.; Johnson, C. L.

    2011-12-01

    The formation of large-scale crustal magnetic anomalies in the Southern Highlands of Mars is equivocal. Though some are indeed elongated primarily in the east-west direction, initial map projections exacerbated their linear nature, leading to the hypothesis that the anomalies are equivalent to magnetic stripes due to spreading of Earth's sea floor and hence to the proposal of plate tectonics on Mars. This interpretation, however, is inconsistent with Martian geology. For instance, a plate-tectonics model predicts the anomalies should be formed in thin, oceanic crust at low elevation, but instead they are found in the thick crust of the Highlands, not in the thin crust of the Northern Lowlands. Indeed, the formation of this Crustal Dichotomy is also equivocal, with models ranging from a giant impact (or multiple smaller impacts) near either the current north or south poles, to plate tectonics-like processes, to mantle convection, either eroding the crust in the northern hemisphere or thickening the crust in the south. Recently, the idea of a giant impact in the north has been resurrected, with the proposal that the Dichotomy results from the formation of an elliptical basin by a giant impact very early in Martian history. While it may be tempting to suggest that the current, generally demagnetized state of the Northern Lowlands may be related to this impact, this linkage makes implicit assumptions about the timing of dynamo shut-off on Mars, and it neglects other demagnetization mechanisms possibly operating in the Lowlands after such an impact (e.g., later hydrothermal processing). More direct magnetic evidence for the giant impact hypothesis would come if the remanent magnetism in Southern Highlands were relatable in a unique way to the putative impact. Here, we show that the positions of many of the dominant elongated magnetic anomalies on Mars are consistent with the first ring of a multi-ring basin. The best match comes from an ellipse ~2200 km wider than the

  20. Processing and Analysis of Near-Seafloor Magnetic Anomalies around Futuna Island, SW Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Szitkar, F.; Dyment, J.; Fouquet, Y.; Choi, Y.

    2011-12-01

    In September 2010, cruise Futuna of R/V L'Atalante collected near-seafloor magnetic data with AUV Aster-X (70 m asf) and Deep-Sea Submersible (DSS) Nautile (2-20 m asf) on several volcanic systems around Futuna Island, SW Pacific Ocean. Here we present the data, the method of analysis, and a first geological interpretation. Unlike a ship, a submersible (or an AUV) cannot tow a magnetometer due to the close proximity of the seafloor. Instead, the magnetometer is rigidly fixed on the submersible, which magnetization affects the magnetic measurements. A vector magnetometer (i.e. three orthogonal fluxgate sensors) measures the field three components in a referential linked to the submarine, a requirement to determine and correct the magnetization of the submersible, The remanent magnetization vector (3 components) and the magnetic susceptibility tensor (9 coefficients) of the submersible are estimated by inverting magnetic data collected on calibration loops, far from both the ship and the seafloor, during the descent (ascent) of the submersible at the beginning (end) of the dives. For this estimation, the ambient field is assumed to be the IGRF, the departures from this assumption reflecting the magnetization of the submersible. The twelve coefficients are inverted from the loop data by a least square method, regularized by a dumping factor to account for the limited pitch and roll values sampled by the submersible. Once determined, these coefficients are used to reduce the magnetic data acquired during the whole dive for the magnetic effect of the submersible, the resulting three component anomalies being rotated to the geographic reference frame as well. The resulting anomalies acquired by the AUV on regularly-spaced tracks are gridded and reduced to the pole such as the resulting anomalies are located on the top of their causative sources. They are further inverted to equivalent magnetization using the high-resolution topography acquired by the AUV. The anomalies

  1. Remanent magnetization and three-dimensional density model of the Kentucky anomaly region

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Existing software was modified to handle 3-D density and magnetization models of the Kentucky body and is being tested. Gravity and magnetic anomaly data sets are ready for use. A preliminary block model is under construction using the 1:1,000,000 maps. An x-y grid to overlay the 1:2,500,000 Albers maps and keyed to the 1:1,000,000 scale block models was created. Software was developed to generate a smoothed MAGSAT data set over this grid; this is to be input to an inversion program for generating the regional magnetization map. The regional scale 1:2,500,000 map mosaic is being digitized using previous magnetization models, the U.S. magnetic anomaly map, and regional tectonic maps as a guide.

  2. Lithospheric sources of magnetic anomalies of the Aldan shield and Alpha Ridge

    NASA Astrophysics Data System (ADS)

    Litvinova, Tamara; Petrova, Alevtina

    2013-04-01

    Regional anomaly Aldan Shield is dated to ancient greenstone belt of the earth's crust. Belt is characterized by high depth forming sequences. Rocks of the upper and middle part of the section contain ferruginous quartzite. Geomagnetic and density sections allowed to estimate the power density and magnetic crustal heterogeneities. The methodology of constructing the cuts is the spectral-spatial representation of the fields, convertible into the underlying magnetic and density cuts. According to satellite data confirms the presence of regional anomalies within the Aldan shield, at an altitude of 100 km, it is about 100 nT. The presence of the Central Aldan crast-mantle fault depth of 50-80 km defines metallogenic situation of the region. The structure of the Aldan Shield detects rotational structure. Regional magnetic anomalies arc tangent frame Central Aldan region. May suggest that such behavior of anomalies is caused by of the ancient (Pre-Cambrian) fireplace mantle (the nucleus). Studies have shown that lithospheric sources Aldan shield on satellite magnetic anomalies and magnetic anomalies (ΔT) a Russia are located at depths of 30 to 35 and 40 to 70 km. They are confined to vertical zone deconsolidated at depths of about 30 and 40 - 70 km. By magnetic anomalies (ΔT) a Russian in the crust of the Aldan shield a depth of 15 - 17 km and 25 - 30 km depth revealed magnetite zone, the formation of which is due to the processes of regional metamorphism of ancient crust. Studies have shown the limits of the depth distribution of magnetite zones, mosaic developed within the crust of the Aldan shield after repeated activation of the processes of regional metamorphism.Alpha Ridge in the Arctic Ocean is one of the largest igneous provinces in the world. Tectonic history of the Arctic while not significantly deciphered. Deep structure of the Earth's crust are poorly understood Linearly elongated magnetic anomalies Alpha Ridge clearly seen at the height of the satellite

  3. Magnetic anomaly detection (MAD) of ferromagnetic pipelines using principal component analysis (PCA)

    NASA Astrophysics Data System (ADS)

    Sheinker, Arie; Moldwin, Mark B.

    2016-04-01

    The magnetic anomaly detection (MAD) method is used for detection of visually obscured ferromagnetic objects. The method exploits the magnetic field originating from the ferromagnetic object, which constitutes an anomaly in the ambient earth’s magnetic field. Traditionally, MAD is used to detect objects with a magnetic field of a dipole structure, where far from the object it can be considered as a point source. In the present work, we expand MAD to the case of a non-dipole source, i.e. a ferromagnetic pipeline. We use principal component analysis (PCA) to calculate the principal components, which are then employed to construct an effective detector. Experiments conducted in our lab with real-world data validate the above analysis. The simplicity, low computational complexity, and the high detection rate make the proposed detector attractive for real-time, low power applications.

  4. Remanent and induced magnetic anomalies over a layered intrusion: Effects from crystal fractionation and magma recharge

    NASA Astrophysics Data System (ADS)

    McEnroe, Suzanne A.; Brown, Laurie L.; Robinson, Peter

    2009-12-01

    The Bjerkreim-Sokndal (BKS) norite - quartz mangerite layered intrusion is part of the early Neoproterozoic Rogaland Anorthosite Province intruded into the Fennoscandian shield in south Norway at ~ 930 Ma. The BKS is exposed over an area of 230 km 2 with a thickness of ~ 7000 m and is of economic interest for ilmenite, magnetite and apatite deposits. From the point of view of magnetic minerals, in the course of fractional crystallization and magma evolution, the ilmenite becomes less Fe 3+-rich reflected by a change from ilmenite with hematite exsolution to nearly pure ilmenite. Magnetite starts to crystallize relatively late in the intrusive history, but its crystallization is interrupted by influxes of more primitive magma. The variations in aeromagnetic and ground-magnetic anomalies measured over the BKS can be explained in terms of the measured magnetic properties of NRM, susceptibility, and hysteresis presented here, and in terms of mineralogy. Early layers in the intrusion contain hemo-ilmenite. As the magma evolved and magnetite started to crystallize, this caused a distinct change over the layering from remanence-controlled negative anomalies to induced positive anomalies. When new, more primitive magma was injected into the system, hemo-ilmenite returned as the major oxide and the resulting magnetic anomalies are again negative. The most dramatic change in the magnetic signature is in the upper part of the intrusion in MCU IVe, where magnetite became a well established cumulate phase as indicated by susceptibility, but its induced magnetization is overcome by large NRMs associated either with hemo-ilmenite, or with hemo-ilmenite and magnetite exsolved from pyroxenes. The average natural remanent magnetizations change from ~ 3 A/m in MCU IVd, to 15 A/m in MCU IVe, and back to 2 A/m in the overlying MCU IVf, producing a strong negative remanent anomaly that has been followed along strike for at least 20 km by ground-magnetic measurements. The highly varied

  5. Lunar Ion Transport Near Magnetic Anomalies: Possible Implications for Swirl Formation

    NASA Technical Reports Server (NTRS)

    Keller, J. W.; Killen, R. M.; Stubbs, T. J.; Farrell, W. M.; Halekas, J. S.

    2011-01-01

    The bright swirling features on the lunar surface in areas around the Moon but most prominently at Reiner Gamma, have intrigued scientists for many years. After Apollo and later Lunar Prospector (LP} mapped the Lunar magnetic fields from orbit, it was observed that these features are generally associated with crustal magnetic anomalies. This led researchers to propose a number of explanations for the swirls that invoke these fields. Prominent among these include magnetic shielding in the form of a mini-magnetosphere which impedes space weathering by the solar wind, magnetically controlled dust transport, and cometary or asteroidal impacts that would result in shock magnetization with concomitant formation ofthe swirls. In this presentation, we will consider another possibility, that the ambient magnetic and electric fields can transport and channel secondary ions produced by micrometeorite or solar wind ion impacts. In this scenario, ions that are created in these impacts are under the influence of these fields and can drift for significant distances before encountering the magnetic anomalies when their trajectories are disrupted and concentrated onto nearby areas. These ions may then be responsible for chemical alteration of the surface leading either to a brightening effect or a disruption of space weathering processes. To test this hypothesis we have run ion trajectory simulations that show ions from regions about the magnetic anomalies can be channeled into very small areas near the anomalies and although questions remain as to nature of the mechanisms that could lead to brightening of the surface it appears that the channeling effect is consistent with the existence of the swirls.

  6. Hydrology in the Durius Valles Region: Evaluation of Possible Correlation with Volcanism and Magnetic Anomalies

    NASA Technical Reports Server (NTRS)

    Cabrol, Natalie A.; Marinangeli, Lucia; Grin, Edmond A.

    2000-01-01

    We envision the contribution of subglacial flows, hydrothermalism and sapping in the Durius Valles system and the consequences in term of climate on Mars in recent geological times. We evaluate the possible correlation of the hydrology with volcanism and magnetic anomalies.

  7. A tale of two anomalies: Depletion, dispersion, and the connection between the stellar lithium spread and inflated radii on the pre-main sequence

    SciTech Connect

    Somers, Garrett; Pinsonneault, Marc H. E-mail: pinsono@astronomy.ohio-state.edu

    2014-07-20

    We investigate lithium depletion in standard stellar models (SSMs) and main sequence (MS) open clusters, and explore the origin of the Li dispersion in young, cool stars of equal mass, age, and composition. We first demonstrate that SSMs accurately predict the Li abundances of solar analogs at the zero-age main sequence (ZAMS) within theoretical uncertainties. We then measure the rate of MS Li depletion by removing the [Fe/H]-dependent ZAMS Li pattern from three well-studied clusters, and comparing the detrended data. MS depletion is found to be mass-dependent, in the sense of more depletion at low mass. A dispersion in Li abundance at fixed T{sub eff} is nearly universal, and sets in by ∼200 Myr. We discuss mass and age dispersion trends, and the pattern is mixed. We argue that metallicity impacts the ZAMS Li pattern, in agreement with theoretical expectations but contrary to the findings of some previous studies, and suggest Li as a test of cluster metallicity. Finally, we argue that a radius dispersion in stars of fixed mass and age, during the epoch of pre-MS Li destruction, is responsible for the spread in Li abundances and the correlation between rotation and Li in young cool stars, most well known in the Pleiades. We calculate stellar models, inflated to match observed radius anomalies in magnetically active systems, and the resulting range of Li abundances reproduces the observed patterns of young clusters. We discuss ramifications for pre-MS evolutionary tracks and age measurements of young clusters, and suggest an observational test.

  8. Three-dimensional inverse modelling of magnetic anomaly sources based on a genetic algorithm

    NASA Astrophysics Data System (ADS)

    Montesinos, Fuensanta G.; Blanco-Montenegro, Isabel; Arnoso, José

    2016-04-01

    We present a modelling method to estimate the 3-D geometry and location of homogeneously magnetized sources from magnetic anomaly data. As input information, the procedure needs the parameters defining the magnetization vector (intensity, inclination and declination) and the Earth's magnetic field direction. When these two vectors are expected to be different in direction, we propose to estimate the magnetization direction from the magnetic map. Then, using this information, we apply an inversion approach based on a genetic algorithm which finds the geometry of the sources by seeking the optimum solution from an initial population of models in successive iterations through an evolutionary process. The evolution consists of three genetic operators (selection, crossover and mutation), which act on each generation, and a smoothing operator, which looks for the best fit to the observed data and a solution consisting of plausible compact sources. The method allows the use of non-gridded, non-planar and inaccurate anomaly data and non-regular subsurface partitions. In addition, neither constraints for the depth to the top of the sources nor an initial model are necessary, although previous models can be incorporated into the process. We show the results of a test using two complex synthetic anomalies to demonstrate the efficiency of our inversion method. The application to real data is illustrated with aeromagnetic data of the volcanic island of Gran Canaria (Canary Islands).

  9. Curie isotherm map of Scotia Arc from near surface magnetic anomaly data

    NASA Astrophysics Data System (ADS)

    Catalán, Manuel

    2016-04-01

    The opening of the Drake Passage, situated between South America and Antarctica, represents the final stage of the fragmentation of Gondwana supercontinent. It led to the Scotia Arc formation, bordering the Scotia Sea, which is surrounded by fragments of the former continental connection. It is currently composed of Scotia and Sandwich Plates. Shackleton Fracture Zone constitutes its sinistral transpressive western boundary and it is a key structure that accommodates former Phoenix and Scotia Plates' differential movement. The formation of the Drake Passage and the Scotia Sea is considered of great importance to ocean circulation, as it allows the establishment of the Antarctic Circumpolar Current that isolated the Antarctic continent, with strong implications for climate and global changes. Thermal structure of the Earth's crust is one of the main parameters controlling geodynamic processes. There is few information regarding heat flow values on Scotia arc. These values are mainly located in its westernmost, southern and easternmost part, which are not enough to extract conclusions regarding lithospheric thickness variations and asthenospheric flow. Taking advantage of the World Digital Magnetic Anomaly Map Project's compilation we have extracted magnetic anomaly data which fall inside the Scotia Arc and surrounding areas. This magnetic anomaly picture provides the best representation of magnetic properties to date. We propose to use spectral methods on this regional magnetic compilation to obtain depth to the bottom of magnetic sources as a proxy to infer Curie depth and heat flow distribution in the Scotia Sea.

  10. Comparison of Magnetic Anomalies of Lithospheric Origin Measured by Satellite and Airborne Magnetometers over Western Canada

    NASA Technical Reports Server (NTRS)

    Langel, R. A.; Coles, R. L.; Mayhew, M. A.

    1979-01-01

    Crustal magnetic anomaly data from the OGO 2, 4 and 6 (Pogo) satellites are compared with upward-continued aeromagnetic data between 50 deg -85 deg N latitude and 220 deg - 260 deg E longitude. Agreement is good both in anomaly location and in amplitude, giving confidence that it is possible to proceed with the derivation and interpretation of satellite anomaly maps in all parts of the globe. The data contain a magnetic high over the Alpha ridge suggesting continental composition and a magnetic low over the southern Canada basin and northern Canadian Arctic islands (Sverdrup basin). The low in the Sverdrup basin corresponds to a region of high heat flow, suggesting a shallow Curie isotherm. A ridge of high field, with two distinct peaks in amplitude, is found over the northern portion of the platform deposits and a relative high is located in the central portion of the Churchill province. No features are present to indicate a magnetic boundary between Slave and Bear provinces, but a trend change is evident between Slave and Churchill provinces. South of 60 deg latitude a broad magnetic low is located over very thick (40-50 km) crust, interpreted to be a region of low magnetization.

  11. Self-similar inverse cascade of magnetic helicity driven by the chiral anomaly

    NASA Astrophysics Data System (ADS)

    Hirono, Yuji; Kharzeev, Dmitri E.; Yin, Yi

    2015-12-01

    For systems with charged chiral fermions, the imbalance of chirality in the presence of magnetic field generates an electric current—this is the chiral magnetic effect (CME). We study the dynamical real-time evolution of electromagnetic fields coupled by the anomaly to the chiral charge density and the CME current by solving the Maxwell-Chern-Simons equations. We find that the CME induces the inverse cascade of magnetic helicity toward the large distances, and that at late times this cascade becomes self-similar, with universal exponents. We also find that in terms of gauge field topology the inverse cascade represents the transition from linked electric and magnetic fields (Hopfions) to the knotted configuration of magnetic field (Chandrasekhar-Kendall states). The magnetic reconnections are accompanied by the pulses of the CME current directed along the magnetic field lines. We devise an experimental signature of these phenomena in heavy ion collisions, and speculate about implications for condensed matter systems.

  12. Interaction between Solar Wind and Lunar Magnetic Anomalies observed by Kaguya MAP-PACE

    NASA Astrophysics Data System (ADS)

    Saito, Yoshifumi; Yokota, Shoichiro; Tanaka, Takaaki; Asamura, Kazushi; Nishino, Masaki; Yamamoto, Tadateru; Uemura, Kota; Tsunakawa, Hideo

    2010-05-01

    It is known that Moon has neither global intrinsic magnetic field nor thick atmosphere. Different from the Earth's case where the intrinsic global magnetic field prevents the solar wind from penetrating into the magnetosphere, solar wind directly impacts the lunar surface. Since the discovery of the lunar crustal magnetic field in 1960s, several papers have been published concerning the interaction between the solar wind and the lunar magnetic anomalies. MAG/ER on Lunar Prospector found heating of the solar wind electrons presumably due to the interaction between the solar wind and the lunar magnetic anomalies and the existence of the mini-magnetosphere was suggested. However, the detailed mechanism of the interaction has been unclear mainly due to the lack of the in-situ observed data of low energy ions. MAgnetic field and Plasma experiment - Plasma energy Angle and Composition Experiment (MAP-PACE) on Kaguya (SELENE) completed its ˜1.5-year observation of the low energy charged particles around the Moon on 10 June, 2009. Kaguya was launched on 14 September 2007 by H2A launch vehicle from Tanegashima Space Center in Japan. Kaguya was inserted into a circular lunar polar orbit of 100km altitude and continued observation for nearly 1.5 years till it impacted the Moon on 10 June 2009. During the last 5 months, the orbit was lowered to ˜50km-altitude between January 2009 and April 2009, and some orbits had further lower perilune altitude of ˜10km after April 2009. MAP-PACE consisted of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). All the sensors performed quite well as expected from the laboratory experiment carried out before launch. Since each sensor had hemispherical field of view, two electron sensors and two ion sensors that were installed on the spacecraft panels opposite to each other could cover full 3-dimensional phase space of low energy electrons and ions. One of the ion sensors IMA was

  13. Magnetization anomalies of nanosize zinc ferrite particles prepared using electrodeposition

    NASA Astrophysics Data System (ADS)

    Roy, M. K.; Verma, H. C.

    2006-11-01

    Nanosize zinc ferrite particles have been prepared for the first time using electrodeposition. Zinc and iron are deposited on the cathode from a common bath containing the salts of zinc and iron. The deposited materials were forced to undergo electrochemical oxidation in a strong alkaline solution (1 M KOH) to convert them into oxides. Crystallization in ZnFe 2O 4 structure was obtained by heating the deposited material at appropriate temperature. X-ray diffraction pattern confirmed that the procedure leads to the formation of pure phase of ZnFe 2O 4. The magnetization value for the smallest size ZnFe 2O 4 is much smaller than that for the ZnFe 2O 4 made by most of the other methods although it shows a nice hysteresis shape. The magnetization shows very little variation with size in the range studied.

  14. Ultrasonography and magnetic resonance imaging evaluation of pediatric spinal anomalies

    PubMed Central

    Dhingani, Dhaval Durlabhbhai; Boruah, Deb Kumar; Dutta, Hemonta Kumar; Gogoi, Rudra Kanta

    2016-01-01

    Context: Spinal dysraphisms are congenital abnormalities of the spine due to imperfect fusion of midline mesenchymal, bony and neural structures. Imaging plays a vital role in their evaluation as significant portion of patients may present with concurrent anomalies that need to be corrected simultaneously to avoid repeat surgeries. Aims: The aims of the study were to evaluate Spinal dysraphisms using USG and MRI and to correlate imaging findings with operative findings in patients undergoing surgery. Settings and Design: Hospital based observational study conducted over a period of year. Materials and Methods: 38 cases of both sexes and below 12 years of age with spinal dysraphism were studied. USG was performed in 29 cases where acoustic window was available for proper evaluation. MRI was performed in all cases. USG findings were compared with MRI findings and operative follow up was taken in 23 cases who underwent operative management. Statistical Analysis Used: Results were analysed using percentage and arithmetic mean. Results: 39.47 % cases were male and 60.53 % cases were female. Neonatal period was the most common presenting age group. Closed spinal dysraphism (63.16%) was more common than open (36.84%). 79.31% cases showed full agreement between spinal USG and MRI examinations and 6 out of 20.69% showed partial agreement. On operative correlation, USG findings were confirmatory in 91.30% cases and MRI findings were confirmatory in 100% cases. Conclusions: USG can be used as the initial modality for evaluation of spinal dysraphism as well as for screening of suspected cases. MRI is indicated to confirm abnormal USG findings, which shows all concurrent abnormalities and also provides additional anatomical details relevant to surgical planning. PMID:27857788

  15. Towards developing an analytical procedure of defining the equatorial electrojet for correcting satellite magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Ravat, Dhananjay; Hinze, William J.

    1991-01-01

    Analysis of the total magnetic intensity MAGSAT data has identified and characterized the variability of ionospheric current effects as reflected in the geomagnetic field as a function of longitude, elevation, and time (daily as well as monthly variations). This analysis verifies previous observations in POGO data and provides important boundary conditions for theoretical studies of ionospheric currents. Furthermore, the observations have led to a procedure to remove these temporal perturbations from lithospheric MAGSAT magnetic anomaly data based on 'along-the-dip-latitude' averages from dawn and dusk data sets grouped according to longitudes, time (months), and elevation. Using this method, high-resolution lithospheric magnetic anomaly maps have been prepared of the earth over a plus or minus 50 deg latitude band. These maps have proven useful in the study of the structures, nature, and processes of the lithosphere.

  16. Contribution of multidomain titanomagnetite to the intensity and stability of Mars crustal magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Brachfeld, Stefanie; Cuomo, David; Tatsumi-Petrochilos, Lisa; Bowles, Julie A.; Shah, Deepa; Hammer, Julia

    2014-11-01

    Two basalts with compositions relevant to the crusts of Mars and Earth were synthesized at igneous temperatures and held at 650°C for 21 to 257 days under quartz-fayalite-magnetite fO2 buffer conditions. The run products are germane to slowly cooled igneous intrusions, which might be a significant volumetric fraction of the Martian crust and carriers of magnetic anomalies in the Southern Highlands. Both basalts acquired intense thermoremanent magnetizations and intense but easily demagnetized anhysteretic remanent magnetizations carried by homogeneous multidomain titanomagnetite. Hypothetical intrusions on Mars composed of these materials would be capable of acquiring intense remanences sufficient to generate the observed anomalies. However, the remanence would be easily demagnetized by impact events after the cessation of the Mars geodynamo. Coercivity enhancement by pressure or formation of single domain regions via exsolution within the multidomain grains is necessary for long-term retention of a remanence carried exclusively by multidomain titanomagnetite grains.

  17. Magnetic Anomalies Between 35 N and 55 N in the North Atlantic: Identification and Implications

    NASA Astrophysics Data System (ADS)

    Luis, J.; Miranda, J. M.

    2005-12-01

    In this work we present a new approach to the detailed identification and interpretation of the magnetic isochrones 5, 6, 13, 18, 20, 22, 22, 23, 24, 25, 26, 28, 29, 30, 32, 33 and 33r on the Eurasian as well as on the American plate, between 55° N and 35° N in the North Atlantic. The identifications were based on a continuous reduction to the pole new technique. From the detailed reconstruction of magnetic isochrones and flow lines, we show that the East Azores Fracture Zone cannot be considered as homologous to the Pico Fracture Zone, implying that a significant amount of the Azores plateau was formed as an independent lithospheric band accreted to the Eurasian plate between the time of anomaly 22 (49 Ma) and ~5 (10 Ma). Based on magnetic anomalies and morphological constrains we reconstruct the previous configurations of the Azores plateau. In particular, we extend a previous study of the Mid-Atlantic Ridge (MAR) for the period 0-10 Ma to a wider time interval into a schematic evolution model for the Azores Triple Junction area. The new isochrones identifications and computation of Euler rotation poles have also implications in the movement of the ancient Iberia plate. Contrary to the currently accepted belief that its movement with respect to the Eurasia plate ended about the time of anomaly 6 (20 Ma), we found no evidences of any movement after the time of anomaly 18 (~38 Ma).

  18. Chemical remanent magnetization of oceanic crust

    SciTech Connect

    Verhoef, J. ); Arkani-Hamed, J. )

    1990-10-01

    The effects of chemical remanent magnetization (CRM) of oceanic crust on the anomalous skewness of sea-floor spreading magnetic anomalies are investigated. Considering a realistic constraint that the actual magnetization at anomaly M0 is reversed, the CRM of layer 2A basalts fails to explain the anomalous skewness of the magnetic anomalies. The CRM of the deeper layers does contribute to the anomalous skewness of anomalies 33/34, but the major contribution comes from thermal remanent magnetization.

  19. Complex venous anomalies: magnetic resonance imaging findings in a 5-year-old boy.

    PubMed

    Hazirolan, Tuncay; Ozkan, Efe; Haliloglu, Mithat; Celiker, Alpay; Balkanci, Ferhun

    2006-10-01

    We report magnetic resonance imaging (MRI) findings of a very unusual venous anomaly case. A 5-year-old boy who had surgical repair of coarctation of the thoracic aorta was referred to our department for evaluation of an enlarged venous structure anterior to the aorta, which had been noted during the surgery. Contrast enhanced dynamic MRI revealed partial anomalous pulmonary venous return to the left azygos vein, double inferior and superior vena cava with the left azygos continuation of the left superior vena cava. The recognition of venous anomalies allows correct planning of surgical and interventional procedures. MRI is a valuable imaging tool providing detailed anatomical information.

  20. Rock magnetic characterization of faulted sediments with associated magnetic anomalies in the Albuquerque Basin, Rio Grande rift, New Mexico

    USGS Publications Warehouse

    Hudson, M.R.; Grauch, V.J.S.; Minor, S.A.

    2008-01-01

    Variations in rock magnetic properties are responsible for the many linear, short-wavelength, low-amplitude magnetic anomalies that are spatially associated with faults that cut Neogene basin sediments in the Rio Grande rift, including the San Ysidro normal fault, which is well exposed in the northern part of the Albuquerque Basin. Magnetic-susceptibility measurements from 310 sites distributed through a 1200-m-thick composite section of rift-filling sediments of the Santa Fe Group and prerift Eocene and Cretaceous sedimentary rocks document large variations of magnetic properties juxtaposed by the San Ysidro fault. Mean volume magnetic susceptibilities generally increase upsection through eight map units: from 1.7 to 2.2E-4 in the prerift Eocene and Cretaceous rocks to 9.9E-4-1.2E-3 in three members of the Miocene Zia Formation of the Santa Fe Group to 1.5E-3-3.5E-3 in three members of the Miocene-Pleistocene Arroyo Ojito Formation of the Santa Fe Group. Rock magnetic measurements and petrography indicate that the amount of detrital magnetite and its variable oxidation to maghemite and hematite within the Santa Fe Group sediments are the predominant controls of their magnetic property variations. Magnetic susceptibility increases progressively with sediment grain size within the members of the Arroyo Ojito Formation (deposited in fluvial environments) but within members of the Zia Formation (deposited in mostly eolian environments) reaches highest values in fine to medium sands. Partial oxidation of detrital magnetite is spatially associated with calcite cementation in the Santa Fe Group. Both oxidation and cementation probably reflect past flow of groundwater through permeable zones. Magnetic models for geologic cross sections that incorporate mean magnetic susceptibilities for the different stratigraphic units mimic the aeromagnetic profiles across the San Ysidro fault and demonstrate that the stratigraphic level of dominant magnetic contrast changes with

  1. Marine Magnetic Anomalies of the Northern Part of the Gulf of Aqaba, Dead Sea Rift

    NASA Astrophysics Data System (ADS)

    Al-Zoubi, A.

    2009-04-01

    MARINE MAGNETIC ANOMALIES OF THE NORTHERN PART OF THE GULF OF AQABA, DEAD SEA RIFT Al-Zoubi (1), Z. Ben-Avraham (2), T. M. Niemi (3), E. Akawi (1), G. Tibor (4), R. Al-Rzouq (1), J.K. Hall (5), A. Abueladas (1), G. Hartman (2) (1) Surveying & Geomatics Department, Al-Balqa' Applied University, Salt, Jordan (2) Department of Geophysics & Planetary Sciences, Tel-Aviv University, Tel-Aviv, Israel (3) University of Missouri-Kansas City, USA. (4) Israel Oceanographic and Limnological Research, Haifa, Israel (5) Geological Survey of Israel, Jerusalem, Israel A high-resolution marine magnetic survey in the northern part of the Gulf of Aqaba, Dead Sea Rift was carried out during October and November 2006. The survey led by an international research group (Israel, Jordan, and USA) funded by MERC, USA and aims to provide the municipalities of Aqaba and Elat a base map of active faults for seismic hazard assessment. The total magnetic intensity at sea surface was measured by a proton precession magnetometer. Diurnal magnetic variation was corrected from the data by using the observation located in southern part of Israel during the survey period. The correction of the external field variation was carried out based on the continuous magnetic observations at a reference magnetic observatory close to the survey area. For calculations of the total intensity of magnetic anomaly, the IGRF model was used as the core field model in accordance with the recommendation of the IAGA. Geomagnetic total intensity anomaly map of the study area has been produced. The magnetic anomaly map shows that there are two major magnetic trends appear in the study area. These are the magnetic high across the northwest section of the Gulf and a magnetic low across the southeast section. These two general trends are divided by a northeast-trending boundary. The magnetic map reveals a complex faults system between the deep part of the Gulf as a pull-apart basin and the on land transform fault in the Araba

  2. Magnetic Anomalies and Rock Magnetic Properties Related to Deep Crustal Rocks of the Athabasca Granulite Terrane, Northern Canada

    NASA Astrophysics Data System (ADS)

    Brown, L. L.; Williams, M. L.

    2010-12-01

    The Athabasca granulite terrane in northernmost Saskatchewan, Canada is an exceptional exposure of lower crustal rocks having experienced several high temperature events (ca 800C) during a prolonged period of deep-crustal residence (ca 1.0 GPa) followed by uplift and exhumation. With little alteration since 1.8 Ga these rocks allow us to study ancient lower crustal lithologies. Aeromagnetic anomalies over this region are distinct and complex, and along with other geophysical measurements, define the Snowbird Tectonic zone, stretching NE-SW across northwestern Canada, separating the Churchill province into the Hearne (mid-crustal rocks, amphibolite facies) from the Rae (lower crust rocks, granulite facies). Distinct magnetic highs and lows appear to relate roughly to specific rock units, and are cut by mapped shear zones. Over fifty samples from this region, collected from the major rock types, mafic granulites, felsic granulites, granites, and dike swarms, as well as from regions of both high and low magnetic anomalies, are being used to investigate magnetic properties. The intention is to investigate what is magnetic in the lower crust and how it produces the anomalies observed from satellite measurements. The samples studied reveal a wide range of magnetic properties with natural remanent magnetization ranging from an isolated high of 38 A/m to lows of 1 mA/m. Susceptibilities also range over several orders of magnitude, from 1 to 1 x10-4 SI. Magnetite is identified in nearly all samples using both low and high temperature measurements, but concentrations are generally very low. Hysteresis properties on 41 samples reveal nearly equal numbers of samples represented by PSD and MD grains, with a few samples (N=6) plotting in or close to the SD region. Low temperature measurements indicate that most samples contain magnetite, showing a marked Verway transition around 120K. Also identified in nearly half of the samples is pyrrhotite, noted by low temperature

  3. Effects of sporadic E-layer characteristics on spread-F generation in the nighttime ionosphere near a northern equatorial anomaly crest during solar minimum

    NASA Astrophysics Data System (ADS)

    Lee, C. C.; Chen, W. S.

    2015-06-01

    This study is to know how the characteristics of sporadic E-layer (Es-layer) affect the generation of spread-F in the nighttime ionosphere near the crest of equatorial ionization anomaly during solar minimum. The data of Es-layer parameters and spread-F are obtained from the Chungli ionograms of 1996. The Es-layer parameters include foEs (critical frequency of Es-layer), fbEs (blanketing frequency of Es-layer), and Δf (≡foEs-fbEs). Results show that the nighttime variations of foEs and fbEs medians (Δf medians) are different from (similar to) that of the occurrence probabilities of spread-F. Because the total number of Es-layer events is greater than that of spread-F events, the comparison between the medians of Es-layer parameters and the occurrence probabilities of spread-F might have a shortfall. Further, we categorize the Es-layer and spread-F events into each frequency interval of Es-layer parameters. For the occurrence probabilities of spread-F versus foEs, an increasing trend is found in post-midnight of all three seasons. The increasing trend also exists in pre-midnight of the J-months and in post-midnight of all seasons, for the occurrence probabilities of spread-F versus Δf. These demonstrate that the spread-F occurrence increases with increasing foEs and/or Δf. Moreover, the increasing trends indicate that polarization electric fields generated in Es-layer assist to produce spread-F, through the electrodynamical coupling of Es-layer and F-region. Regarding the occurrence probabilities of spread-F versus fbEs, the significant trend only appears in post-midnight of the E-months. This implies that fbEs might not be a major factor for the spread-F formation.

  4. Curie Point Depths in North China Craton Based on Spectral Analysis of Magnetic Anomalies

    NASA Astrophysics Data System (ADS)

    Xu, Ya; Hao, Tianyao; Zeyen, Hermann; Nan, Fangzhou

    2017-01-01

    Magnetic anomaly analysis is an important method to study the structure of deep crust. With the assumption of random magnetization sources, the structure of a magnetic layer can be inverted via spectral analysis. Curie point depth (CPD), the depth at which rocks lose their ferromagnetic properties, is the bottom of a magnetic layer. In this study, we estimate from the magnetic anomaly data of EMAG2 dataset the CPD and the top of the magnetic layer in North China. With a moving window of 180 km × 180 km, we calculate the average top and centroid depth of the magnetic layer in each window and determine the regional CPD distribution across North China. The CPD of North China varies from 18 to 32 km. In addition, the CPD in the western part of the North China Craton is deeper than that in the eastern part. The shallowest CPD is located near the Bohai Sea. When compared to available heat flow data, the estimated CPD values are consistent with thermal conductivity of 1.8-3.2 Wm-1 K-1 and on heat production value of 0.4-1.3 µWm-3.

  5. The satellite magnetic anomaly of Ahaggar - Evidence for African Plate motion

    NASA Technical Reports Server (NTRS)

    Phillips, R. J.; Brown, C. R.

    1985-01-01

    The Ahaggar volcanic province of North Central Africa is considered a region of excess heat flow (hot spot) and hence elevated Curie isotherm. Using a modified version of the Parker FFT potential field representation, magnetic signals were calculated at Magsat altitudes for models in which the African Plate is both fixed and moving. The moving-plate model extends the Curie isotherm anomaly in the direction of plate motion and provides a satisfactory match to vertical component anomaly data when the magnitude of plate velocity is 0.75 cm/yr. Although the signal levels are marginal for the scalar component anomalies of this region, the same model provides an adequate match to this data set and is clearly preferable to a fixed-plate model.

  6. The Effect of Dissipation Mechanism on X-line Spreading in 3D Magnetic

    NASA Astrophysics Data System (ADS)

    Shepherd, L. S.; Cassak, P.; Phan, T.; Shay, M. A.; Gosling, J. T.

    2012-12-01

    Naturally occurring magnetic reconnection generally begins in a spatially localized region and spreads in the direction perpendicular to the reconnection plane as time progresses. Reconnection spreading is associated with dawn-dusk asymmetries during substorms in the magnetotail and has been observed in two-ribbon flares (such as the Bastille Day flare) and laboratory experiments at the Versatile Toroidal Facility (VTF) and the Magnetic Reconnection eXperiment (MRX). It was suggested that X-line spreading is necessary to explain the existence of X-lines extending more than 390 Earth radii (Phan et al., Nature, 404, 848, 2006). Previous numerical studies exploring the spreading of localized magnetic reconnection exclusively addressed collisionless (Hall) reconnection. Here, we address the effect of dissipation mechanism has on X-line spreading with and without a guide field. We compare previous results with simulations using three alternate phases of reconnection - Sweet-Parker reconnection, collisional reconnection with secondary islands, and reconnection with anomalous resistivity. We present results from three-dimensional resistive magnetohydrodynamic numerical simulations to address the nature of X-line spreading. Applications to reconnection in the solar wind and corona will be discussed.

  7. Initial Mapping of Mercury's Crustal Magnetic Anomalies: Relationship to the Caloris Impact Basin

    NASA Astrophysics Data System (ADS)

    Hood, L. L.

    2015-12-01

    78 low-altitude orbit passes of MESSENGER calibrated magnetometer data from August and September of 2014 have been applied to produce approximate maps of the crustal magnetic field covering latitudes of 50-80N and longitudes of 160-320E. Only anomalies with wavelengths < 215 km were mapped and amplitudes were adjusted for differences in spacecraft altitude using an equivalent source dipole technique. Maps of the radial field component show that the strongest large-scale anomalies are located in the western part of the mapped region just north and northeast of the 1550-km diameter Caloris impact basin centered at 164E, 30N. When adjusted to a common altitude of ~ 40 km, the strongest single anomaly (~170E, 60N; > 6 nT) lies over a smooth plains unit that extends north-northeastward from Caloris. A second anomaly (185E, 53N, > 5 nT) lies on the Odin Formation, interpreted as Caloris ejecta (e.g., Guest and Greeley, USGS, 1983). As previously reported by Johnson et al. (Science, 2015), a third anomaly (~ 212E, 61N, > 5 nT) also lies over a smooth plains unit, Suisse Planitia. Most smooth plains units on Mercury may have a volcanic origin (Denevi et al., JGR, 2013). However, as discussed by the latter authors, a subset of the smooth plains occur in an annulus around Caloris and could have an impact-related origin, involving fluidized basin ejecta deposition (Wilhelms, Icarus, 1976). A similar origin is widely accepted for the lunar Cayley smooth plains, which dominate the geology near the Apollo 16 landing site where the strongest surface magnetic fields were measured and which correlate best with orbital anomalies on the lunar near side (Halekas et al., JGR, 2001). Two of the remaining three anomalies (220E, 68N, > 4 nT; 234E, 77N, > 5 nT) lie over an older intermediate plains unit with an uncertain interpretation, possibly consisting of impact basin and crater ejecta as well as volcanic materials (Grolier and Boyce, USGS, 1984). In view of the proximity of the

  8. Magsat equivalent source anomalies over the southeastern United States - Implications for crustal magnetization

    NASA Technical Reports Server (NTRS)

    Ruder, M. E.; Alexander, S. S.

    1986-01-01

    The Magsat crustal anomaly field depicts a previously-unidentified long-wavelength negative anomaly centered over southeastern Georgia. Examination of Magsat ascending and descending passes clearly identifies the anomalous region, despite the high-frequency noise present in the data. Using ancillary seismic, electrical conductivity, Bouguer gravity, and aeromagnetic data, a preliminary model of crustal magnetization for the southern Appalachian region is presented. A lower crust characterized by a pervasive negative magnetization contrast extends from the New York-Alabama lineament southeast to the Fall Line. In southern Georgia and eastern Alabama (coincident with the Brunswick Terrane), the model calls for lower crustal magnetization contrast of -2.4 A/m; northern Georgia and the Carolinas are modeled with contrasts of -1.5 A/m. Large-scale blocks in the upper crust which correspond to the Blue Ridge, Charlotte belt, and Carolina Slate belt, are modeled with magnetization contrasts of -1.2 A/m, 1.2 A/m, and 1.2 A/m respectively. The model accurately reproduces the amplitude of the observed low in the equivalent source Magsat anomaly field calculated at 325 km altitude and is spatially consistent with the 400 km lowpass-filtered aeromagnetic map of the region.

  9. Correlations Between Magnetic Anomalies and Surface Geology Antipodal to Lunar Impact Basins

    NASA Astrophysics Data System (ADS)

    Richmond, N. C.; Hood, L. L.

    2004-12-01

    Previous work has shown that the strongest concentrations of lunar crustal magnetic anomalies are located antipodal to four large, similarly aged impact basins (Orientale, Serenitatis, Imbrium and Crisium). Here, we report results of a correlation study between magnetic anomaly clusters and geology in areas antipodal to Imbrium and Orientale. Only these areas have been selected due to a) limited Lunar Prospector magnetometer data coverage of the area antipodal to Serenitatis, and b) the location of the Crisium antipode, which is dominated by ejecta deposits from the more recent Orientale impact. Unusual geologic terranes have been mapped antipodal to both Orientale (furrowed and pitted terrane) and Imbrium (material of grooves and mounds). These units have been interpreted to be of seismic or ejecta origin associated with the basin forming impacts. Both regions have many high albedo swirl markings, which have been shown to correlate closely with regions of high crustal magnetisation at other locations. Results indicate a strong correlation between the swirl markings and regions of high magnetisation for both the Imbrium and Orientale antipodes. In addition, the furrowed and pitted terrane, material of grooves and mounds and Mare Ingenii (antipodal to Imbrium) show a correlation with high magnitude crustal magnetic anomalies. Mare Ingenii is on the south west edge of the material of grooves and mounds and may overlay that unit, with the anomaly sources beneath the mare materials. This is supported by an observed lack of demagnetisation associated with the 61 km Copernican-aged O'Day crater at the edge of Mare Ingenii, which suggests a deep source for the anomalies. Possible source materials and the origin of the magnetisation will be discussed at the conference.

  10. Magnetic anomalies concentrated near and within Mercury's impact basins: Early mapping and interpretation

    NASA Astrophysics Data System (ADS)

    Hood, L. L.

    2016-06-01

    Ninety-five low-altitude passes of MErcury Surface, Space ENvironment, GEochemistry, and Ranging magnetometer data from February, March, and April of 2015 have been applied to produce an approximate map of the crustal magnetic field at a constant altitude of 40 km covering latitudes of 35°-75°N and longitudes of 90°-270°E. Anomalies are concentrated near and within the Caloris impact basin. A smaller concentration occurs over and around Sobkou Planitia and an associated older large impact basin. The strongest anomalies are found within Caloris and are distributed in a semicircular arc that is roughly concentric with the basin rim. They imply the existence of a core dynamo at the time when Caloris formed (˜3.9 Gyr ago). Anomalies over high-reflectance volcanic plains are relatively weak while anomalies over low-reflectance material that has been reworked by impact processes are relatively strong. The latter characteristics are qualitatively consistent with the ejecta deposit model for anomaly sources.

  11. The North West African Margin Magnetic Anomaly revisited : implications for the initial evolution of the Central Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Sahabi, M.; Olivet, J.-L.; Aslanian, D.; Patriat, M.; Géli, L.; Matias, L.; Réhault, J.-P.; Malod, J.; Bouabdelli, M.

    2003-04-01

    Due to the lack of data from the North West African margin, the Mesozïc evolution of the Central Atlantic is still controversial. Existing plate kinematics (Le Pichon et al, 1977), Wissmann and Roger (1982), Olivet et al, 1984, Klitgord and Schouten, 1986) reconstructions do not explain the characteristics of the S1 Magnetic Anomaly, nor the the presence and geometry of salt basins on the margins off NW Marocco and off Mauritania. We present a new magnetic compilation detailing the correspondance between the different conjugated magnetic anomalies that exist on each side of the Central Atlantic : the East Coast (ECMA), Brunswick (BMA) and Blake Spur (BSMA) Magnetic Anomalies on the American side, and the S1 and West African Coast (WACMA) magnetic anomalies on the African side. In addition, using all available, academic, seismic data, we mapped the ocenawards extension of the salt province of the 200 Ma old Seine Abyssal Plain basin, off Marocco, which is considered as autochtonous.

  12. 3D non-linear inversion of magnetic anomalies caused by prismatic bodies using differential evolution algorithm

    NASA Astrophysics Data System (ADS)

    Balkaya, Çağlayan; Ekinci, Yunus Levent; Göktürkler, Gökhan; Turan, Seçil

    2017-01-01

    3D non-linear inversion of total field magnetic anomalies caused by vertical-sided prismatic bodies has been achieved by differential evolution (DE), which is one of the population-based evolutionary algorithms. We have demonstrated the efficiency of the algorithm on both synthetic and field magnetic anomalies by estimating horizontal distances from the origin in both north and east directions, depths to the top and bottom of the bodies, inclination and declination angles of the magnetization, and intensity of magnetization of the causative bodies. In the synthetic anomaly case, we have considered both noise-free and noisy data sets due to two vertical-sided prismatic bodies in a non-magnetic medium. For the field case, airborne magnetic anomalies originated from intrusive granitoids at the eastern part of the Biga Peninsula (NW Turkey) which is composed of various kinds of sedimentary, metamorphic and igneous rocks, have been inverted and interpreted. Since the granitoids are the outcropped rocks in the field, the estimations for the top depths of two prisms representing the magnetic bodies were excluded during inversion studies. Estimated bottom depths are in good agreement with the ones obtained by a different approach based on 3D modelling of pseudogravity anomalies. Accuracy of the estimated parameters from both cases has been also investigated via probability density functions. Based on the tests in the present study, it can be concluded that DE is a useful tool for the parameter estimation of source bodies using magnetic anomalies.

  13. Bangui Anomaly

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.

    2004-01-01

    Bangui anomaly is the name given to one of the Earth s largest crustal magnetic anomalies and the largest over the African continent. It covers two-thirds of the Central African Republic and therefore the name derives from the capitol city-Bangui that is also near the center of this feature. From surface magnetic survey data Godivier and Le Donche (1962) were the first to describe this anomaly. Subsequently high-altitude world magnetic surveying by the U.S. Naval Oceanographic Office (Project Magnet) recorded a greater than 1000 nT dipolar, peak-to-trough anomaly with the major portion being negative (figure 1). Satellite observations (Cosmos 49) were first reported in 1964, these revealed a 40nT anomaly at 350 km altitude. Subsequently the higher altitude (417-499km) POGO (Polar Orbiting Geomagnetic Observatory) satellite data recorded peak-to-trough anomalies of 20 nT these data were added to Cosmos 49 measurements by Regan et al. (1975) for a regional satellite altitude map. In October 1979, with the launch of Magsat, a satellite designed to measure crustal magnetic anomalies, a more uniform satellite altitude magnetic map was obtained. These data, computed at 375 km altitude recorded a -22 nT anomaly (figure 2). This elliptically shaped anomaly is approximately 760 by 1000 km and is centered at 6%, 18%. The Bangui anomaly is composed of three segments; there are two positive anomalies lobes north and south of a large central negative field. This displays the classic pattern of a magnetic anomalous body being magnetized by induction in a zero inclination field. This is not surprising since the magnetic equator passes near the center of this body.

  14. Remanent magnetization and 3-dimensional density model of the Kentucky anomaly region

    NASA Technical Reports Server (NTRS)

    Mayhew, M. A.; Estes, R. H.; Myers, D. M.

    1984-01-01

    A three-dimensional model of the Kentucky body was developed to fit surface gravity and long wavelength aeromagnetic data. Magnetization and density parameters for the model are much like those of Mayhew et al (1982). The magnetic anomaly due to the model at satellite altitude is shown to be much too small by itself to account for the anomaly measured by Magsat. It is demonstrated that the source region for the satellite anomaly is considerably more extensive than the Kentucky body sensu stricto. The extended source region is modeled first using prismatic model sources and then using dipole array sources. Magnetization directions for the source region found by inversion of various combinations of scalar and vector data are found to be close to the main field direction, implying the lack of a strong remanent component. It is shown by simulation that in a case (such as this) where the geometry of the source is known, if a strong remanent component is present its direction is readily detectable, but by scalar data as readily as vector data.

  15. Interaction between solar wind and lunar magnetic anomalies observed by MAP-PACE on Kaguya

    NASA Astrophysics Data System (ADS)

    Saito, Yoshifumi; Yokota, Shoichiro; Tanaka, Takaaki; Asamura, Kazushi; Nishino, Masaki N.; Yamamoto, Tadateru I.; Tsunakawa, Hideo

    It is well known that the Moon has neither global intrinsic magnetic field nor thick atmosphere. Different from the Earth's case where the intrinsic global magnetic field prevents the solar wind from penetrating into the magnetosphere, solar wind directly impacts the lunar surface. MAgnetic field and Plasma experiment -Plasma energy Angle and Composition Experiment (MAP-PACE) on Kaguya (SELENE) completed its 1.5-year observation of the low energy charged particles around the Moon on 10 June 2009. Kaguya was launched on 14 September 2007 by H2A launch vehicle from Tanegashima Space Center in Japan. Kaguya was inserted into a circular lunar polar orbit of 100km altitude and continued observation for nearly 1.5 years till it impacted the Moon on 10 June 2009. During the last 5 months, the orbit was lowered to 50km-altitude between January 2009 and April 2009, and some orbits had further lower perilune altitude of 10km after April 2009. MAP-PACE consisted of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). Since each sensor had hemispherical field of view, two electron sensors and two ion sensors that were installed on the spacecraft panels opposite to each other could cover full 3-dimensional phase space of low energy electrons and ions. One of the ion sensors IMA was an energy mass spectrometer. IMA measured mass identified ion energy spectra that had never been obtained at 100km altitude polar orbit around the Moon. When Kaguya flew over South Pole Aitken region, where strong magnetic anomalies exist, solar wind ions reflected by magnetic anomalies were observed. These ions had much higher flux than the solar wind protons scattered at the lunar surface. The magnetically reflected ions had nearly the same energy as the incident solar wind ions while the solar wind protons scattered at the lunar surface had slightly lower energy than the incident solar wind ions. At 100km altitude, when the reflected ions

  16. Considerations of variations in ionospheric field effects in mapping equatorial lithospheric Magsat magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Ravat, D.; Hinze, W. J.

    1993-01-01

    The longitudinal, seasonal, and altitude-dependent variability of the magnetic field in equatorial latitudes is investigated to determine the effect of these variabilities on the isolation of lithospheric Magsat magnetic anomalies. It was found that the amplitudes of the dawn dip-latitude averages were small compared to the dusk averages, and that they were of the opposite sign. The longitudinal variation in the equatorial amplitudes of the dawn dip-latitude averages was not entirely consistent with the present knowledge of the electrojet field. Based on the results, a procedure is implemented for reducing the equatorial ionospheric effects from the Magsat data on the lithospheric component.

  17. Effects of edge magnetism on the Kohn anomalies of zigzag graphene nanoribbons.

    PubMed

    Culchac, F J; Capaz, Rodrigo B

    2016-02-12

    The effects of edge magnetism on the Kohn anomaly (KA) of the G-band phonons of zigzag graphene nanoribbons (ZGNRs) are studied using a combination of the tight-binding and mean-field Hubbard models. We show that the opening of an energy gap, induced by magnetic ordering, significantly changes the KA effects, particularly for narrow ribbons in which the gap is larger than the phonon energy. Therefore, the G-band phonon frequency and lifetime are altered for a magnetically-ordered edge state with respect to an unpolarized edge state. The effects of temperature, ZGNR width, doping and transverse electric fields are systematically investigated. We propose using this effect to probe the magnetic order of edge states in graphene nanoribbons using Raman spectroscopy.

  18. Chapter 3: Circum-Arctic mapping project: New magnetic and gravity anomaly maps of the Arctic

    USGS Publications Warehouse

    Gaina, C.; Werner, S.C.; Saltus, R.; Maus, S.; Aaro, S.; Damaske, D.; Forsberg, R.; Glebovsky, V.; Johnson, K.; Jonberger, J.; Koren, T.; Korhonen, J.; Litvinova, T.; Oakey, G.; Olesen, O.; Petrov, O.; Pilkington, M.; Rasmussen, T.; Schreckenberger, B.; Smelror, M.

    2011-01-01

    New Circum-Arctic maps of magnetic and gravity anomalies have been produced by merging regional gridded data. Satellite magnetic and gravity data were used for quality control of the long wavelengths of the new compilations. The new Circum-Arctic digital compilations of magnetic, gravity and some of their derivatives have been analyzed together with other freely available regional and global data and models in order to provide a consistent view of the tectonically complex Arctic basins and surrounding continents. Sharp, linear contrasts between deeply buried basement blocks with different magnetic properties and densities that can be identified on these maps can be used, together with other geological and geophysical information, to refine the tectonic boundaries of the Arctic domain. ?? 2011 The Geological Society of London.

  19. Spherical Earth analysis and modeling of lithospheric gravity and magnetic anomalies. Ph.D. Thesis - Purdue Univ.

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.

    1980-01-01

    A comprehensive approach to the lithospheric analysis of potential field anomalies in the spherical domain is provided. It has widespread application in the analysis and design of satellite gravity and magnetic surveys for geological investigation.

  20. Origin of Strong Lunar Magnetic Anomalies: More Detailed Mapping in Regions Antipodal to Young Large Basins

    NASA Astrophysics Data System (ADS)

    Hood, L. L.; Richmond, N.; Spudis, P.

    2012-12-01

    Previous work has found evidence that the largest concentrations of strong lunar crustal magnetic fields are in regions antipodal to four young large lunar basins: Orientale, Imbrium, Crisium, and Serenitatis (Mitchell et al., Icarus, 2008; and references therein). A preliminary model for the production of lunar basin antipodal magnetic signatures has been developed (Hood and Artemieva, Icarus, 2008; Gattacceca et al., EPSL, 2010). The model involves shock magnetization of crustal materials in the presence of a transient magnetic field amplified by the expanding ionized vapor-melt cloud as it converges in the antipodal region. The model does not exclude a core dynamo; any ambient magnetic field (external solar wind or internal core dynamo) can be amplified in the antipodal zone. In this paper, we report further efforts to map in more detail Lunar Prospector magnetometer data in regions antipodal to young lunar basins. In addition to the four basins identified above, we also consider the polar Schrodinger basin, which is one of the three youngest lunar basins and which has not been previously considered in this context. We apply a direct mapping method (see Hood, Icarus, 2011 for details) to produce more complete maps of lunar magnetic anomalies at low altitudes over the central far side and over the north polar region. We also consider geologic data and spacecraft imagery to identify unusual modified terrain, which may be indicative of shock modification in the same basin antipodal zones. Previous work indicates the existence of such terrain antipodal to Imbrium, Orientale, and Serenitatis, as well as antipodal to the Caloris basin on Mercury. Results first confirm the concentrations of anomalies antipodal to Orientale, Imbrium, Crisium, and Orientale, and the occurrence of modified terrain in three of the four basin antipode zones (see, e.g., Richmond et al., JGR, 2005). In addition, we report here evidence for a large concentration of anomalies that is centered

  1. EMAG2: A 2-arc min resolution Earth Magnetic Anomaly Grid compiled from satellite, airborne, and marine magnetic measurements

    USGS Publications Warehouse

    Maus, S.; Barckhausen, U.; Berkenbosch, H.; Bournas, N.; Brozena, J.; Childers, V.; Dostaler, F.; Fairhead, J.D.; Finn, C.; von Frese, R.R.B; Gaina, C.; Golynsky, S.; Kucks, R.; Lu, Hai; Milligan, P.; Mogren, S.; Muller, R.D.; Olesen, O.; Pilkington, M.; Saltus, R.; Schreckenberger, B.; Thebault, E.; Tontini, F.C.

    2009-01-01

    A global Earth Magnetic Anomaly Grid (EMAG2) has been compiled from satellite, ship, and airborne magnetic measurements. EMAG2 is a significant update of our previous candidate grid for the World Digital Magnetic Anomaly Map. The resolution has been improved from 3 arc min to 2 arc min, and the altitude has been reduced from 5 km to 4 km above the geoid. Additional grid and track line data have been included, both over land and the oceans. Wherever available, the original shipborne and airborne data were used instead of precompiled oceanic magnetic grids. Interpolation between sparse track lines in the oceans was improved by directional gridding and extrapolation, based on an oceanic crustal age model. The longest wavelengths (>330 km) were replaced with the latest CHAMP satellite magnetic field model MF6. EMAG2 is available at http://geomag.org/models/EMAG2 and for permanent archive at http://earthref.org/ cgi-bin/er.cgi?s=erda.cgi?n=970. ?? 2009 by the American Geophysical Union.

  2. True Polar Wander and Hotspot Fixity: A Paleomagnetic Investigation of the Skewness of Magnetic Anomaly 12r (32 Ma B.P.) on the Pacific Plate

    NASA Astrophysics Data System (ADS)

    Gordon, R. G.; Horner-Johnson, B. C.

    2010-12-01

    Prior studies have shown that Pacific hotspots and Indo-Atlantic hotspots have moved in approximate unison relative to the spin axis since 65 Ma B.P. [Morgan, 1981; Gordon and Cape, 1981; Gordon, 1982] and since 56 Ma B.P. [Petronotis et al., 1994], which is most simply interpreted as true polar wander. In contrast, Pacific hotspots and Indo-Atlantic hotspots give conflicting results for 72 Ma B.P. and for 81 Ma B.P., which may indicate motion between Pacific hotspots and Indo-Atlantic hotspots [Tarduno and Cottrell, 1997; Petronotis et al., 1999; Tarduno et al., 2003]. Thus it is important to estimate Pacific plate apparent polar wander (APW) for more time intervals. From such estimates the APW of Pacific hotspots can be inferred and compared with that of Indo-Atlantic hotspots [e.g., Besse and Courtillot 2002]. Here we present a study of the skewness of anomaly 12r between the Galapagos and Clipperton and between the Clipperton and Clarion fracture zones. We chose this region for several reasons: First, numerical experiments, like those conducted by Acton and Gordon [1991], indicate that magnetic profiles between the Galapagos and Clarion fracture zones should contain the most information about the Pacific plate paleomagnetic pole for chron C12r (32 Ma B.P.). Second, in these two spreading rate corridors, spreading half rates range from 72 to 86 mm/a and therefore have negligible anomalous skewness, given that they exceed ≈50 mm/a [Roest et al., 1992; Dyment et al. 1994]. Third, vector aeromagnetic profiles are available for analysis. One of the challenges to interpreting magnetic anomalies in low latitudes where the anomalies strike nearly north-south is the very low amplitude of the signal relative to the noise, the latter of which can be especially intense near the present magnetic equator due to the amplification of diurnal variation by the equatorial electrojet. Previously we showed that vector aeromagnetic profiles record low-latitude Pacific plate

  3. Magnetic storm associated enhanced particle precipitation in the South Atlantic anomaly: Evidence from VLF phase measurements

    SciTech Connect

    Abdu, M.A.; Batista, I.S.; Piazza, L.R.; Massambani, O.

    1981-09-01

    Phase recordings at Atibaia, Brazil (23 /sup 0/S, 46 /sup 0/W), of 13.6 -kHz signal transmitted from Golfo Nuevo, Argentian (43 /sup 0/S, 65 /sup 0/W), a trajectory confined almost completely within the South Atlantic anomaly region, show significant perturbations, indicative of the lowering of the VLF reflection level, following the onset of magnetic disturbances. Simultaneous measurements of the E/sub s/ layer parameters f/sub t/E/sub s/ and f/sub b/E/sub s/ over Cachoeira Paulista (22 /sup 0/S, 45 /sup 0/W) also show enhancements, with some delay with respect to the magnetic disturbance onset, as was found in our earlier work (Batista and Abdu, 1977). These results show magnetic storm associated ionization enhancements taking place in a height region from approximately 110 km down to 70 km, which we interpret as having been produced by precipitation of high-energy charged particles in the South Atlantic magnetic anomaly. The results also suggest some degree of day to day variability in the abundance of metallic species and/or in the dynamics of the E region over this region.

  4. Correlation between the Palaeozoic structures from West Iberian and Grand Banks margins using inversion of magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Silva, Elsa A.; Miranda, J. M.; Luis, J. F.; Galdeano, A.

    2000-05-01

    The Ibero-Armorican Arc (IAA) is a huge geological structure of Pre-Cambrian origin, tightened during hercynian times and deeply affected by the opening of the Atlantic Ocean and the Bay of Biscay. Its remnants now lie in Iberia, north-western France and the Canadian Grand Banks margins. The qualitative correlation between these three blocks has been attempted by several authors (e.g. Lefort, J.P., 1980. Un 'Fit' structural de l'Atlantique Nord: arguments geologiques pour correler les marqueurs geophysiques reconnus sur les deux marges. Mar. Geol. 37, 355-369; Lefort, J.P., 1983. A new geophysical criterion to correlate the Acadian and Hercynian orogenies of Western Europe and Eastern America. Mem. Geol. Soc. Am. 158, 3-18; Galdeano, A., Miranda, J.M., Matte, P., Mouge, P., Rossignol, C., 1990. Aeromagnetic data: A tool for studying the Variscan arc of Western Europe and its correlation with transatlantic structures. Tectonophysics 177, 293-305) using magnetic anomalies, mainly because they seem to preserve the hercynian zonation, in spite of the strong thermal and mechanical processes that took place during rifting and ocean spreading. In this paper, we present a new contribution to the study of the IAA structure based on the processing of a compilation of magnetic data from Iberia and Grand Banks margins. To interpret the magnetic signature, a Fourier-domain-based inversion technique was applied, considering a layer with a constant thickness of 10 km, and taking into account only the induced field. The digital terrain model was derived from ETOPO5 (ETOPO5, 1986. Relief map of the earth's surface. EOS 67, 121) and TerrainBase (TerrainBase, 1995. In: Row III, L.W., Hastings, D.A., Dunbar, P.K. (Eds.), Worldwide Digital Terrain Data, Documentation Manual, CD-ROM Release 1.0. GEODAS-NGDC Key to Geophysical Records. Documentation N. 30, April) databases. The pseudo-susceptibility distribution obtained was repositioned for the 156.5 Ma epoch, using the Srivastava and

  5. Congenital Variants and Anomalies of the Pancreas and Pancreatic Duct: Imaging by Magnetic Resonance Cholangiopancreaticography and Multidetector Computed Tomography

    PubMed Central

    Erden, Ayşe; Türkoğlu, Mehmet Akif; Yener, Özlem

    2013-01-01

    Though congenital anomalies of the pancreas and pancreatic duct are relatively uncommon and they are often discovered as an incidental finding in asymptomatic patients, some of these anomalies may lead to various clinical symptoms such as recurrent abdominal pain, nausea and vomiting. Recognition of these anomalies is important because these anomalies may be a surgically correctable cause of recurrent pancreatitis or the cause of gastric outlet obstruction. An awareness of these anomalies may help in surgical planning and prevent inadvertent ductal injury. The purpose of this article is to review normal pancreatic embryology, the appearance of ductal anatomic variants and developmental anomalies of the pancreas, with emphasis on magnetic resonance cholangiopancreaticography and multidetector computed tomography. PMID:24265565

  6. Interpretation of gravity and magnetic anomalies at Lake Rotomahana: Geological and hydrothermal implications

    NASA Astrophysics Data System (ADS)

    Caratori Tontini, F.; de Ronde, C. E. J.; Scott, B. J.; Soengkono, S.; Stagpoole, V.; Timm, C.; Tivey, M.

    2016-03-01

    We investigate the geological and hydrothermal setting at Lake Rotomahana, using recently collected potential-field data, integrated with pre-existing regional gravity and aeromagnetic compilations. The lake is located on the southwest margin of the Okataina Volcanic Center (Haroharo caldera) and had well-known, pre-1886 Tarawera eruption hydrothermal manifestations (the famous Pink and White Terraces). Its present physiography was set by the caldera collapse during the 1886 eruption, together with the appearance of surface activities at the Waimangu Valley. Gravity models suggest that subsidence associated with the Haroharo caldera is wider than the previously mapped extent of the caldera margins. Magnetic anomalies closely correlate with heat-flux data and surface hydrothermal manifestations and indicate that the west and northwestern shore of Lake Rotomahana are characterized by a large, well-developed hydrothermal field. The field extends beyond the lake area with deep connections to the Waimangu area to the south. On the south, the contact between hydrothermally demagnetized and magnetized rocks strikes along a structural lineament with high heat-flux and bubble plumes which suggest hydrothermal activity occurring west of Patiti Island. The absence of a well-defined demagnetization anomaly at this location suggests a very young age for the underlying geothermal system which was likely generated by the 1886 Tarawera eruption. Locally confined intense magnetic anomalies on the north shore of Lake Rotomahana are interpreted as basalt dikes with high magnetization. Some appear to have been emplaced before the 1886 Tarawera eruption. A dike located in proximity of the southwest lake shore may be related to the structural lineament controlling the development of the Patiti geothermal system, and could have been originated from the 1886 Tarawera eruption.

  7. Spread F occurrence and drift under the crest of the equatorial ionization anomaly from continuous Doppler sounding and FORMOSAT-3/COSMIC scintillation data

    NASA Astrophysics Data System (ADS)

    Chum, Jaroslav; Liu, Jann-Yenq; Chen, Shih-Ping; Cabrera, Miguel Angel; Laštovička, Jan; Baše, Jiří; Burešová, Dalia; Fišer, Jiří; Hruška, František; Ezquer, Rodolfo

    2016-04-01

    A relatively new method based on measurements by multipoint continuous Doppler sounding is applied to study the occurrence rate, propagation velocities, and directions of spread F structures over Tucumán, Northern Argentina, and Taiwan, both of which were under the crest of the equatorial ionization anomaly in 2014. In addition, spread F is studied globally over the same time period from the S4 scintillation index measured onboard FORMOSAT-3/COSMIC (F3/C) satellite. It is shown that the continuous Doppler sounding gives results that are consistent with S4 data and with previous optical, global positioning system (GPS), and satellite measurements. Most of the spread F events were observed from September to March, i.e., during the local summer half of the year in Tucumán, whereas in Taiwan, the highest occurrence rate was observed around equinoxes. The occurrence rate in Tucumán was about four times higher than that in Taiwan. The propagation velocities and directions were estimated from the Doppler shift spectrograms. The spread structures related to spread F propagated roughly eastward at velocities from ~70 to ~200 m s-1 during nighttime hours. The mean observed horizontal velocity was 140 m s-1 over Tucumán and 107 m s-1 over Taiwan. The local times at which the highest velocities were observed roughly correspond to local times with highest values of scintillation index S4, at ~20 to 23 LT. In addition, a comparison of measured drift velocities with neutral wind velocities predicted by models is provided. The observed velocities usually exceeded the horizontal neutral wind velocities predicted by the HWM14 model for the locations and times of observations.

  8. Anisotropic Solar Wind Sputtering of the Lunar Surface Induced by Crustal Magnetic Anomalies

    NASA Technical Reports Server (NTRS)

    Poppe, A. R.; Sarantos, M.; Halekas, J. S.; Delory, G. T.; Saito, Y.; Nishino, M.

    2014-01-01

    The lunar exosphere is generated by several processes each of which generates neutral distributions with different spatial and temporal variability. Solar wind sputtering of the lunar surface is a major process for many regolith-derived species and typically generates neutral distributions with a cosine dependence on solar zenith angle. Complicating this picture are remanent crustal magnetic anomalies on the lunar surface, which decelerate and partially reflect the solar wind before it strikes the surface. We use Kaguya maps of solar wind reflection efficiencies, Lunar Prospector maps of crustal field strengths, and published neutral sputtering yields to calculate anisotropic solar wind sputtering maps. We feed these maps to a Monte Carlo neutral exospheric model to explore three-dimensional exospheric anisotropies and find that significant anisotropies should be present in the neutral exosphere depending on selenographic location and solar wind conditions. Better understanding of solar wind/crustal anomaly interactions could potentially improve our results.

  9. Magnetic anomaly map of North America south of 50 degrees north from Pogo data

    NASA Technical Reports Server (NTRS)

    Mayhew, M. A.

    1976-01-01

    A magnetic anomaly map produced from Pogo data for North America and adjacent ocean areas is presented. At satellite elevations anomalies have wavelengths measured in hundreds of kilometers, and reflect regional structures on a large scale. Prominent features of the map are: (1) a large east-west high through the mid-continent, breached at the Mississippi Embayment; (2) a broad low over the Gulf of Mexico; (3) a strong gradient separating these features, which follows the Southern Appalachian-Ouachita curvature; and (4) a high over the Antilles-Bahamas Platform which extends to northern Florida. A possible relationship between the high of the mid-continent and the 38th parallel lineament is noted.

  10. An attempt to obtain a detailed declination chart from the United States magnetic anomaly map

    USGS Publications Warehouse

    Alldredge, L.R.

    1989-01-01

    Modern declination charts of the United States show almost no details. It was hoped that declination details could be derived from the information contained in the existing magnetic anomaly map of the United States. This could be realized only if all of the survey data were corrected to a common epoch, at which time a main-field vector model was known, before the anomaly values were computed. Because this was not done, accurate declination values cannot be determined. In spite of this conclusion, declination values were computed using a common main-field model for the entire United States to see how well they compared with observed values. The computed detailed declination values were found to compare less favourably with observed values of declination than declination values computed from the IGRF 1985 model itself. -from Author

  11. Self-similar inverse cascade of magnetic helicity driven by the chiral anomaly

    DOE PAGES

    Hirono, Yuji; Kharzeev, Dmitri E.; Yin, Yi

    2015-12-28

    For systems with charged chiral fermions, the imbalance of chirality in the presence of magnetic field generates an electric current—this is the chiral magnetic effect (CME). We study the dynamical real-time evolution of electromagnetic fields coupled by the anomaly to the chiral charge density and the CME current by solving the Maxwell-Chern-Simons equations. We find that the CME induces the inverse cascade of magnetic helicity toward the large distances, and that at late times this cascade becomes self-similar, with universal exponents. We also find that in terms of gauge field topology the inverse cascade represents the transition from linked electricmore » and magnetic fields (Hopfions) to the knotted configuration of magnetic field (Chandrasekhar-Kendall states). The magnetic reconnections are accompanied by the pulses of the CME current directed along the magnetic field lines. In conclusion, we devise an experimental signature of these phenomena in heavy ion collisions, and speculate about implications for condensed matter systems.« less

  12. Self-similar inverse cascade of magnetic helicity driven by the chiral anomaly

    SciTech Connect

    Hirono, Yuji; Kharzeev, Dmitri E.; Yin, Yi

    2015-12-28

    For systems with charged chiral fermions, the imbalance of chirality in the presence of magnetic field generates an electric current—this is the chiral magnetic effect (CME). We study the dynamical real-time evolution of electromagnetic fields coupled by the anomaly to the chiral charge density and the CME current by solving the Maxwell-Chern-Simons equations. We find that the CME induces the inverse cascade of magnetic helicity toward the large distances, and that at late times this cascade becomes self-similar, with universal exponents. We also find that in terms of gauge field topology the inverse cascade represents the transition from linked electric and magnetic fields (Hopfions) to the knotted configuration of magnetic field (Chandrasekhar-Kendall states). The magnetic reconnections are accompanied by the pulses of the CME current directed along the magnetic field lines. In conclusion, we devise an experimental signature of these phenomena in heavy ion collisions, and speculate about implications for condensed matter systems.

  13. Magnetic Anomaly Modeling of Volcanic Structure and Stratigraphy - Socorro Island, Eastern Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Urrutia-Fucugauchi, Jaime; Escorza-Reyes, Marisol; Pavon-Moreno, Julio; Perez-Cruz, Ligia; Sanchez-Zamora, Osvaldo

    2013-04-01

    Results of a magnetic survey of the volcanic structure of Socorro Island in the Revillagigedo Archipielago are presented. Socorro is part of a group of seamounts and oceanic islands built by volcanic activity at the northern end of the Mathematician ridge and intersection with the Clarion and Rivera fracture zones. Subaerial volcanic activity is characterized by alkaline and peralkaline compositions, marked by pre-, syn- and post-caldera phases of the Evermann volcano, and the Holocene mafic activity of the Lomas Coloradas. The magnetic survey conducted in the central-southern sector of the island permits to investigate the volcanic structure and subsurface stratigraphy. Regional fields for second- and third-degree polynomials show a magnetic low over the caldera, positive anomalies above the pre-caldera deposits and intermediate amplitude anomalies over Lomas Coloradas. Residual fields delineate the structural rim of the caldera, anomaly trends for the pre- and post-caldera deposits and a broad anomaly over Lomas Coloradas. Regional-residual anomalies, first vertical derivative, analytical upward and downward continuations, and forward four-layer modeling are used to construct the geophysical models. Rock magnetic properties were analyzed on samples collected at 24 different sites. Magnetic susceptibility showed wide range of variation from ~10 to ~500 10-3 SI, corresponding to the different lithologies from trachytes and glass-rich tuffs to alkali basalts. Data have been divided into groups with low, intermediate and high values. Rock magnetic analyses indicate that magnetite and titanomagnetites are the main magnetization carriers. Magnetic hysteresis loops indicate low coercivity minerals, with high saturation and remanent magnetizations and PSD domain states. Magnetic susceptibility versus temperature curves show irreversible behavior with Curie temperatures around 560-575 C, suggesting magnetite and Ti-poor titanomagnetites. Paleomagnetic directions

  14. Magnetic anomalies in Bahia Esperanza: A window of magmatic arc intrusions and glacier erosion over the northeastern Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Galindo-Zaldívar, Jesús; Ruiz-Constán, Ana; Pedrera, Antonio; Ghidella, Marta; Montes, Manuel; Nozal, Francisco; Rodríguez-Fernandez, Luis Roberto

    2013-02-01

    Bahia Esperanza, constituting the NE tip of the Antarctic Peninsula, is made up of Paleozoic clastic sedimentary rocks overlain by a Jurassic volcano-sedimentary series and intruded by Cretaceous gabbros and diorites. The area is located along the southern part of the Pacific Margin magnetic anomaly belt. Field magnetic researches during February 2010 contribute to determining the deep geometry of the intermediate and basic intrusive rocks. Moreover, the new field data help constrain the regional Pacific Margin Anomaly, characterized up to now only by aeromagnetic and marine data. Field magnetic susceptibility measurements of intrusive intermediate and basic rocks, responsible for magnetic anomalies, ranges from 0.5 × 10- 3 SI in diorites to values between 0.75 × 10- 3 SI and 1.3 × 10- 3 SI in gabbros. In addition, a significant remanent magnetism should also have contributed to the anomalies. The regional magnetic anomaly is characterized by a westward increase from 100 nT up to 750 nT, associated with large intrusive diorite bodies. They probably underlie most of the western slopes of Mount Flora. Gabbros in the Nobby Nunatak determine local residual rough anomalies that extend northwards and westwards, pointing to the irregular geometry of the top of the basic rocks bodies below the Pirámide Peak Glacier. However, the southern and eastern boundaries with the Buenos Aires Glacier are sharp related to deep glacier incision. As a result of the glacier dynamics, magnetic anomalies are also detected north of the Nobby Nunatak due to the extension of the anomalous body and the presence of gabbro blocks in the moraines. The Bahia Esperanza region is a key area where onshore field geological and magnetic research allows us to constrain the shape of the crustal igneous intrusions and the basement glacier geometry, providing accurate data that complete regional aeromagnetic research.

  15. Fetal Central Nervous System Anomalies Detected by Magnetic Resonance Imaging: A Two-Year Experience

    PubMed Central

    Sefidbakht, Sepideh; Dehghani, Sakineh; Safari, Maryam; Vafaei, Homeira; Kasraeian, Maryam

    2016-01-01

    Background Magnetic resonance imaging (MRI) is gradually becoming more common for thorough visualization of the fetus than ultrasound (US), especially for neurological anomalies, which are the most common indications for fetal MRI and are a matter of concern for both families and society. Objectives We investigated fetal MRIs carried out in our center for frequency of central nervous system anomalies. This is the first such report in southern Iran. Materials and Methods One hundred and seven (107) pregnant women with suspicious fetal anomalies in prenatal ultrasound entered a cross-sectional retrospective study from 2011 to 2013. A 1.5 T Siemens Avanto scanner was employed for sequences, including T2 HASTE and Trufisp images in axial, coronal, and sagittal planes to mother’s body, T2 HASTE and Trufisp relative to the specific fetal body part being evaluated, and T1 flash images in at least one plane based on clinical indication. We investigated any abnormality in the central nervous system and performed descriptive analysis to achieve index of frequency. Results Mean gestational age ± standard deviation (SD) for fetuses was 25.54 ± 5.22 weeks, and mean maternal age ± SD was 28.38 ± 5.80 years Eighty out of 107 (74.7%) patients who were referred with initial impression of borderline ventriculomegaly. A total of 18 out of 107 (16.82%) patients were found to have fetuses with CNS anomalies and the remainder were neurologically normal. Detected anomalies were as follow: 3 (16.6%) fetuses each had the Dandy-Walker variant and Arnold-Chiari II (with myelomeningocele). Complete agenesis of corpus callosum, partial agenesis of corpus callosum, and aqueductal stenosis were each seen in 2 (11.1%) fetuses. Arnold-Chiari II without myelomeningocele, anterior spina bifida associated with neurenteric cyst, arachnoid cyst, lissencephaly, and isolated enlarged cisterna magna each presented in one (5.5%) fetus. One fetus had concomitant schizencephaly and complete agenesis of

  16. Three-dimensional correlation imaging for total amplitude magnetic anomaly and normalized source strength in the presence of strong remanent magnetization

    NASA Astrophysics Data System (ADS)

    Guo, Lianghui; Meng, Xiaohong; Zhang, Guoli

    2014-12-01

    We present the 3D correlation imaging approach for the total magnitude magnetic anomaly and the normalized source strength data for reducing effects of strong remanent magnetization. We divide the subsurface space into a 3D regular grid and then calculate the cross correlation between the observed total magnitude magnetic anomaly or normalized source strength and the theoretical total magnitude magnetic anomaly or normalized source strength at each grid node due to a magnetic dipole. The resultant correlation coefficients are used to describe the equivalent magnetic dipole distribution underground in a probabilistic sense. The two approaches were tested both on the synthetic magnetic data and the real magnetic data from a metallic deposit area in the middle-lower reaches of the Yangtze River, China. The results show that the two approaches can considerably reduce effects of remanent magnetization and delineate magnetic sources in the subsurface, and that the approach for the normalized source strength is less sensitive to strong remanent magnetization than that of the total magnitude magnetic anomaly.

  17. Investigations of medium wavelength magnetic anomalies in the eastern Pacific using Magsat data

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A. (Principal Investigator)

    1980-01-01

    The author has identified the following significant results. Three long total magnetic field profiles taken over ocean basins were analyzed. It is found that there is a significant signal in the wavelength range of 1500 to 150 km. This is too short a wavelength to be caused by the core field, which becomes insignificant at about a wavelength of 1500 km; this intermediate wavelength signal is not caused by a typical sea floor spreading process, which should give maximum power in the wavelength region about 50 km. It is shown that the external magnetic field contributes very little to this intermediate wavelength signal. Efforts to explain the cause of this signal have failed.

  18. Building the second version of the World Digital Magnetic Anomaly Map (WDMAM)

    NASA Astrophysics Data System (ADS)

    Lesur, Vincent; Hamoudi, Mohamed; Choi, Yujin; Dyment, Jérôme; Thébault, Erwan

    2016-02-01

    The World Digital Anomaly Map (WDMAM) is a worldwide compilation of near-surface magnetic data. We present here a candidate for the second version of the WDMAM and its characteristics. This candidate has been evaluated by a group of independent reviewers and has been adopted as the official second version of the WDMAM during the 26th general assembly of the International Union of Geodesy and Geomagnetism (IUGG). The way this compilation has been built is described with some details. A global magnetic field model of the lithosphere contribution, parameterised by spherical harmonics, has been derived up to degree and order 800. The model information content has been evaluated by computing local spectra. Further, the compatibility of the anomaly field displayed by the WDMAM with a pure induced magnetisation is tested by comparison with the main field strength. These studies allowed an analysis of the compilation in terms of strength and wavelength content. They confirm the extremely smooth and weak contribution of the magnetic field generated in the lithosphere over Western Europe. This apparent weakness possibly extends to the Northern African continent. However, a global analysis remains difficult to achieve given the sparseness of good quality data over very large area of oceans and continents. The WDMAM and related information can be downloaded at http://www.wdmam.org/.

  19. Release of the World Digital Magnetic Anomaly Map version 2 (WDMAM v2) scheduled

    NASA Astrophysics Data System (ADS)

    Dyment, Jérôme; Lesur, Vincent; Choi, Yujin; Hamoudi, Mohamed; Thébault, Erwan; Catalan, Manuel

    2015-04-01

    The World Digital Magnetic Anomaly Map is an international initiative carried out under the auspices of the International Association of Geomagnetism and Aeronomy (IAGA) and the Commission for the Geological Map of the World (CGMW). A first version of the map has been published and distributed eight years ago (WDMAM v1; Korhonen et al., 2007). After a call for an improved second version of the map in 2011, the slow process of data compilation, map preparation, evaluation and finalization is near completion, and the WDMAM v2 will be released at the International Union of Geophysics and Geodesy (IUGG) meeting to be held in Prag in June-July 2015. In this presentation we display several shortcomings of the WDMAM v1, both on continental and oceanic areas, that are hopefully alleviated in the WDMAM v2, and discuss the process leading to the new map. We reiterate a long-standing call for aeromagnetic and marine magnetic data contribution, and explore future directions to pursue the effort toward a more complete, higher resolution magnetic anomaly map of the World.

  20. Investigation of source location determination from Magsat magnetic anomalies: The Euler method approach

    NASA Technical Reports Server (NTRS)

    Ravat, Dhananjay

    1996-01-01

    The applicability of the Euler method of source location determination was investigated on several model situations pertinent to satellite-data scale situations as well as Magsat data of Europe. Our investigations enabled us to understand the end-member cases for which the Euler method will work with the present satellite magnetic data and also the cases for which the assumptions implicit in the Euler method will not be met by the present satellite magnetic data. These results have been presented in one invited lecture at the Indo-US workshop on Geomagnetism in Studies of the Earth's Interior in August 1994 in Pune, India, and at one presentation at the 21st General Assembly of the IUGG in July 1995 in Boulder, CO. A new method, called Anomaly Attenuation Rate (AAR) Method (based on the Euler method), was developed during this study. This method is scale-independent and is appropriate to locate centroids of semi-compact three dimensional sources of gravity and magnetic anomalies. The method was presented during 1996 Spring AGU meeting and a manuscript describing this method is being prepared for its submission to a high-ranking journal. The grant has resulted in 3 papers and presentations at national and international meetings and one manuscript of a paper (to be submitted shortly to a reputable journal).

  1. Monitoring the evolution of Deception Island volcano from magnetic anomaly data (South Shetland Islands, Antarctica)

    NASA Astrophysics Data System (ADS)

    Catalán, Manuel; Martos, Yasmina M.; Galindo-Zaldívar, Jesús; Funaki, Minoru

    2014-12-01

    Deception Island is a young and active volcano located in the south-western part of Bransfield back-arc basin. During the last twenty years the Royal Observatory of the Spanish Navy has carried out geophysical surveys in the area. In addition, an unmanned aerial vehicle flight was conducted in 2011 at 800 m height on the northern half of Deception Island. Analysing and comparing magnetic grids obtained in different periods and tie point readings allow us to detect temporal changes and isolate signals of volcanic origin. Magnetic survey cruises performed in Deception Island's inner bay (1988, 1999 and 2008), and the study of its outer area's magnetic anomaly changes, point to a period of high variations concentrated between December 1989 and December 1999 that may be related to the two main recent periods of seismic activity (1992 and January 1999). From December 1999 to December 2008, there were no significant changes in seismic activity; nevertheless, our data show some magnetic alterations, which might signal the slow progress of a volcanic environment towards equilibrium. Interpreting these magnetic changes called for the construction of several forward models. Additionally, we put forth this kind of study as a suitable, economical and easy method for monitoring an active volcanic system whenever it is possible to measure the magnetic field with accurate positioning, and if the external field components are removed correctly.

  2. Polar Wander on the Moon Inferred from its Shape and Magnetic Anomalies

    NASA Astrophysics Data System (ADS)

    Garrick-Bethell, I.

    2015-12-01

    The lunar shape can inform us about the Moon's early spin pole location, or history of true polar wander. This history is important for understanding the stability of polar ice deposits [1], and possible relationships between large-scale lunar features and the lunar orbit. Recently, Garrick-Bethell et al. [2] showed that when the effects of large basins are ignored, the Moon's early spin pole could be inferred from a tidal-rotational deformation that froze-in when the Moon was closer to the Earth. They also showed that the lunar shape is consistent with early tidal heating in the crust during the magma ocean epoch [3]. Here we will present some updates to this work, and discuss how the lunar spin pole may have evolved in time, as inferred from the progressive formation of large basins and components of the degree-2 gravity field that are not associated with basins. Separately, magnetic anomalies can address the problem of lunar polar wander, assuming the ancient dynamo that magnetized them was dominantly dipolar and aligned with the spin axis. However, recent surveys of magnetic anomalies reveal paleopole distributions that are quite complicated and inconsistent across different studies [4, 5]. Some reported paleopoles are consistent with the early spin pole inferred from the lunar shape [2], while others are not. These paleopoles imply either very large amounts of polar wander, or that the dynamo evolved with a complex field geometry. Some possible resolutions to these problems will be discussed, including secular variation of the magnetic field and difficulties with inversions for magnetic sources. References 1. Siegler, M. A. et al., 46th Lunar and Planetary Science Conference, LPI Contribution No. 1832, p. 2675 (2015). 2. Garrick-Bethell, I., et al., Nature 512, 181 (2014). 3. Garrick-Bethell, I., et al., Science 330, 949 (2010). 4. Arkani-Hamed, J. and Boutin, D., Icarus 237, 262 (2014). 5. Takahashi, F., et al., Nature Geoscience 7, 409 (2014).

  3. Magnetically Tuning Tether Mobility of Integrin Ligand Regulates Adhesion, Spreading, and Differentiation of Stem Cells.

    PubMed

    Wong, Dexter S H; Li, Jinming; Yan, Xiaohui; Wang, Ben; Li, Rui; Zhang, Li; Bian, Liming

    2017-03-08

    Cells sense and respond to the surrounding microenvironment through binding of membranous integrin to ligands such as the Arg-Gly-Asp (RGD) peptide. Previous studies show that the RGD tether properties on substrate influence cell adhesion and spreading, but few studies have reported strategies to control the tether mobility of RGD on substrate via a physical and noncontact approach. Herein, we demonstrate a novel strategy to tune the tether mobility of RGD on substrate via magnetic force. We conjugate a monolayer of RGD-bearing magnetic nanoparticles (MNPs) on a glass substrate via the flexible and coiled poly(ethylene glycol) linker of large molecular weight (PEG, average MW: 2000), and this increases the RGD tether mobility, which can be significantly reduced by applying magnetic attraction on MNPs. Our data show that high RGD tether mobility delays the early adhesion and spreading of human mesenchymal stem cells (hMSCs), leading to compromised osteogenic differentiation at later stage. In contrast, hMSCs cultured on substrate with restricted RGD tether mobility, achieved either via a shorter PEG linker (MW: 200) or magnetic force, show significantly better adhesion, spreading, and osteogenic differentiation. The control utilizing RGD-bearing nonmagnetic nanoparticles shows no such enhancing effect of magnetic field on cellular events, further supporting our conjecture of magnetic tuning of RGD tether mobility. We hypothesize that high tether mobility of RGD entails additional time and effort by the cells to fully develop traction force and mechanical feedback, thereby delaying the maturation of FAs and activation of subsequent mechanotransduction signaling. Our staining results of vinculin, a critical component of FAs, and Yes-associated protein (YAP), an important mechanosensitive transcriptional factor, support our hypothesis. We believe that our work not only sheds light on the impact of dynamic presentation of cell adhesive ligands on cellular behaviors

  4. The Spreading of X-lines in Three Dimensions during Magnetic Reconnection with a Guide Field

    NASA Astrophysics Data System (ADS)

    Shepherd, L. S.; Cassak, P.

    2011-12-01

    Naturally occurring magnetic reconnection often begins in a spatially localized region and spreads in the out-of-plane direction as time progresses. This has been studied by a number of authors for magnetotail applications such as substorms and bursty bulk flows, for which the out-of-plane (guide) field is typically small. However, this same behavior has been observed in laboratory experiments, in two-ribbon solar flares (such as the Bastille Day flare), and at the dayside of the magnetopause. In each of these settings, a significant guide field is present. Without a guide field, it was shown that the reconnection spreading is controlled by the species that carries the current. However, laboratory experiments with a large guide field (Katz et al., Phys. Rev. Lett., 104, 255004, 2010) revealed that the spreading takes place in both directions at the Alfven speed based on the guide magnetic field. We present three-dimensional two-fluid numerical simulations to address the condition on the guide field at which the nature of the spreading switches from being caused by the current carriers to being caused by Alfven waves. Applications for the corona will be discussed.

  5. Calculation of the magnetic gradient tensor from total magnetic anomaly field based on regularized method in frequency domain

    NASA Astrophysics Data System (ADS)

    Yin, Gang; Zhang, Yingtang; Mi, Songlin; Fan, Hongbo; Li, Zhining

    2016-11-01

    To obtain accurate magnetic gradient tensor data, a fast and robust calculation method based on regularized method in frequency domain was proposed. Using the potential field theory, the transform formula in frequency domain was deduced in order to calculate the magnetic gradient tensor from the pre-existing total magnetic anomaly data. By analyzing the filter characteristics of the Vertical vector transform operator (VVTO) and Gradient tensor transform operator (GTTO), we proved that the conventional transform process was unstable which would zoom in the high-frequency part of the data in which measuring noise locate. Due to the existing unstable problem that led to a low signal-to-noise (SNR) for the calculated result, we introduced regularized method in this paper. By selecting the optimum regularization parameters of different transform phases using the C-norm approach, the high frequency noise was restrained and the SNR was improved effectively. Numerical analysis demonstrates that most value and characteristics of the calculated data by the proposed method compare favorably with reference magnetic gradient tensor data. In addition, calculated magnetic gradient tensor components form real aeromagnetic survey provided better resolution of the magnetic sources and original profile.

  6. A least-squares minimization approach for model parameters estimate by using a new magnetic anomaly formula

    NASA Astrophysics Data System (ADS)

    Abo-Ezz, E. R.; Essa, K. S.

    2016-04-01

    A new linear least-squares approach is proposed to interpret magnetic anomalies of the buried structures by using a new magnetic anomaly formula. This approach depends on solving different sets of algebraic linear equations in order to invert the depth ( z), amplitude coefficient ( K), and magnetization angle ( θ) of buried structures using magnetic data. The utility and validity of the new proposed approach has been demonstrated through various reliable synthetic data sets with and without noise. In addition, the method has been applied to field data sets from USA and India. The best-fitted anomaly has been delineated by estimating the root-mean squared (rms). Judging satisfaction of this approach is done by comparing the obtained results with other available geological or geophysical information.

  7. Modeling of Magnetic Anomalies Associated with Magmatic Intrusions Away from the Guaymas Basin Rift, Gulf of California

    NASA Astrophysics Data System (ADS)

    Isunza, I.

    2015-12-01

    It is well known that continental breakup can be defined by the detection of magnetic anomalies caused by magma from a recently formed ridge. However in transitional continental-oceanic crust zones, special attention must be paid. These zones commonly present weak magnetic anomalies whose interpretation is debated, and the use of geophysical techniques is necessary. Guaymas basin in Gulf of California is one of the few known places in the world in which magmatic intrusions are intruding in rich-organic sediments. This is thought to cause the observed magnetic anomalies within the zone. In this work, magnetic and seismic data acquired during the GUAYMAS14 cruise, on board RV El Puma, are used to create a 2D forward model which describes structure geometry of the intrusions and their distribution outside the rift grabens.

  8. Cardiac magnetic resonance imaging and the assessment of ebstein anomaly in adults.

    PubMed

    Yalonetsky, Sergey; Tobler, Daniel; Greutmann, Matthias; Crean, Andrew M; Wintersperger, Bernd J; Nguyen, Elsie T; Oechslin, Erwin N; Silversides, Candice K; Wald, Rachel M

    2011-03-01

    No published studies have evaluated the role of cardiac magnetic resonance (CMR) imaging for the assessment of Ebstein anomaly. Our objective was to evaluate the right heart characteristics in adults with unrepaired Ebstein anomaly using contemporary CMR imaging techniques. Consecutive patients with unrepaired Ebstein anomaly and complete CMR studies from 2004 to 2009 were identified (n = 32). Volumetric measurements were obtained from the short-axis and axial views, including assessment of the functional right ventricular (RV) end-diastolic volume (EDV) and end-systolic volume. The volume of the atrialized portion of the right ventricle in end-diastole was calculated as the difference between the total RVEDV and the functional RVEDV. The reproducibility of the measurements in the axial and short-axis views was determined within and between observers. The median value derived from the short-axis and axial views was 136 ml/m(2) (range 59 to 347) and 136 ml/m(2) (range 63 to 342) for the functional RVEDV, 153 ml/m(2) (range 64 to 441) and 154 ml/m(2) (range 67 to 436) for the total RVEDV, 49% (range 32% to 46%) and 50% (range 40% to 64%) for the functional RV ejection fraction, respectively. The axial measurements demonstrated lower intraobserver and interobserver variability than the short-axis approach for all values, with the exception of the intraobserver functional RVEDV and interobserver total RVEDV for which the limits of agreement and variance were not significantly different between the 2 views. In conclusion, measurements of right heart size and systolic function in patients with Ebstein anomaly can be reliably achieved using CMR imaging. Axial imaging appeared to provide more reproducible data than that obtained from the short-axis views.

  9. Magnetic anomalies in East Antarctica: a window on major tectonic provinces and their boundaries

    USGS Publications Warehouse

    Golynsky, A.V.

    2007-01-01

    An analysis of aeromagnetic data compiled within the Antarctic Digital Magnetic Anomaly Project (ADMAP) yields significant new insight into major tectonic provinces of East Antarctica. Several previously unknown crustal blocks are imaged in the deep interior of the continent, which are interpreted as cratonic nuclei. These cratons are fringed by a large and continuous orogenic belt between Coats Land and Princess Elizabeth Land, with possible branches in the deeper interior of East Antarctica. Most of the crustal provinces and boundaries identified in this study are only in part exposed. More detailed analyses of these crustal provinces and their tectonic boundaries would require systematic acquisition of additional high-resolution magnetic data, because at present the ADMAP database is largely inadequate to address many remaining questions regarding Antarctica’s tectonic evolution.

  10. Energy Detection Based on Undecimated Discrete Wavelet Transform and Its Application in Magnetic Anomaly Detection

    PubMed Central

    Nie, Xinhua; Pan, Zhongming; Zhang, Dasha; Zhou, Han; Chen, Min; Zhang, Wenna

    2014-01-01

    Magnetic anomaly detection (MAD) is a passive approach for detection of a ferromagnetic target, and its performance is often limited by external noises. In consideration of one major noise source is the fractal noise (or called 1/f noise) with a power spectral density of 1/fa (0magnetic anomaly detection and UDWT are introduced in brief, while a possible detection system based on giant magneto-impedance (GMI) magnetic sensor is also given out. Then our proposed energy detection based on UDWT is described in detail, and the probabilities of false alarm and detection for given the detection threshold in theory are presented. It is noticeable that no a priori assumptions regarding the ferromagnetic target or the magnetic noise probability are necessary for our method, and different from the discrete wavelet transform (DWT), the UDWT is shift invariant. Finally, some simulations are performed and the results show that the detection performance of our proposed detector is better than that of the conventional energy detector even utilized in the Gaussian white noise, especially when the spectral parameter α is less than 1.0. In addition, a real-world experiment was done to demonstrate the advantages of the proposed method. PMID:25343484

  11. A Review of Magnetic Anomaly Field Data for the Arctic Region: Geological Implications

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.; vonFrese, Ralph; Roman, Daniel; Frawley, James J.

    1999-01-01

    Due to its inaccessibility and hostile physical environment remote sensing data, both airborne and satellite measurements, has been the main source of geopotential data over the entire Arctic region. Ubiquitous and significant external fields, however, hinder crustal magnetic field studies These potential field data have been used to derive tectonic models for the two major tectonic sectors of this region, the Amerasian and Eurasian Basins. The latter is dominated by the Nansen-Gakkel or Mid-Arctic Ocean Ridge and is relatively well known. The origin and nature of the Alpha and Mendeleev Ridges, Chukchi Borderland and Canada Basin of the former are less well known and a subject of controversy. The Lomonosov Ridge divides these large provinces. In this report we will present a summary of the Arctic geopotential anomaly data derived from various sources by various groups in North America and Europe and show how these data help us unravel the last remaining major puzzle of the global plate tectonic framework. While magnetic anomaly data represent the main focus of this study recently derived satellite gravity data are playing a major role in Arctic studies.

  12. A Review of Magnetic Anomaly Field Data for the Arctic Region: Geological Implications

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.; vonFrese, Ralph; Roman, Daniel; Frawley, James J.

    1999-01-01

    Due to its inaccessibility and hostile physical environment remote sensing data, both airborne and satellite measurements, has been the main source of geopotential data over the entire Arctic region. Ubiquitous and significant external fields, however, hinder crustal magnetic field studies. These potential field data have been used to derive tectonic models for the two major tectonic sectors of this region, the Amerasian and Eurasian Basins. The latter is dominated by the Nansen-Gakkel or Mid-Arctic Ocean Ridge and is relatively well known. The origin and nature of the Alpha and Mendeleev Ridges, Chukchi Borderland and Canada Basin of the former are less well known and a subject of controversy. The Lomonosov Ridge divides these large provinces. In this report we will present a summary of the Arctic geopotential anomaly data derived from various sources by various groups in North America and Europe and show how these data help us unravel the last remaining major puzzle of the global plate tectonic framework. While Magnetic anomaly data represent the main focus of this study recently derived satellite gravity data (Laxon and McAdoo, 1998) are playing a major role in Arctic studies.

  13. Spherical cap harmonic analysis of regional magnetic anomalies based on CHAMP satellite data

    NASA Astrophysics Data System (ADS)

    Feng, Yan; Jiang, Yong; Jiang, Yi; Liu, Bao-Jia; Jiang, Jin; Liu, Zhong-Wei; Ye, Mei-Chen; Wang, Hong-Shen; Li, Xiu-Ming

    2016-09-01

    We used CHAMP satellite vector data and the latest IGRF12 model to investigate the regional magnetic anomalies over mainland China. We assumed satellite points on the same surface (307.69 km) and constructed a spherical cap harmonic model of the satellite magnetic anomalies for elements X, Y, Z, and F over Chinese mainland for 2010.0 (SCH2010) based on selected 498 points. We removed the external field by using the CM4 model. The pole of the spherical cap is 36N° and 104°E, and its half-angle is 30°. After checking and comparing the root mean square (RMS) error of Δ X, Δ Y, and Δ Z and X, Y, and Z, we established the truncation level at K max = 9. The results suggest that the created China Geomagnetic Referenced Field at the satellite level (CGRF2010) is consistent with the CM4 model. We compared the SCH2010 with other models and found that the intensities and distributions are consistent. In view of the variation of F at different altitudes, the SCH2010 model results obey the basics of the geomagnetic field. Moreover, the change rate of X, Y, and Z for SCH2010 and CM4 are consistent. The proposed model can successfully reproduce the geomagnetic data, as other data-fitting models, but the inherent sources of error have to be considered as well.

  14. World Digital Magnetic Anomaly Map version 2 (WDMAM v.2) - released for research and education

    NASA Astrophysics Data System (ADS)

    CHOI-Dyment, Y.; Lesur, V.; Dyment, J.; Hamoudi, M.; Thebault, E.; Catalan, M.

    2015-12-01

    The World Digital Magnetic Anomaly Map is an international initiative carried out under the auspices of the International Association of Geomagnetism and Aeronomy (IAGA) and the Commission for the Geological Map of the World (CGMW). A first version of the map has been published and distributed eight years ago (WDMAM v1; Korhonen et al., 2007). We have produced a candidate which has been accepted as the second version of this map (WDMAM v2) at the International Union of Geophysics and Geodesy in Prag, in June 2015. On land, we adopted an alternative approach avoiding any unnecessary processing on existing aeromagnetic compilations. When available, we used the original aeromagnetic data. As a result the final compilation remains an acceptable representation of the national and international data grids. Over oceanic areas the marine data have been extended. In areas of insufficient data coverage, a model has been computed based on a modified digital grid of the oceanic lithosphere age, considering plate motions in the determination of magnetization vector directions. This model has been further adjusted to the available data, resulting in a better representation of the anomalies. The final grid will be periodically upgraded. Version 2.0 has been released and is available at wdmam.org to support both research and education projects. Colleagues willing to contribute data for future releases (and become a co-author of the map) should contact any of the authors or Jerome Dyment (chair of the WDMAM Task Force) at jdy@ipgp.fr .

  15. Magnetic and tectonic studies of the dueling propagating spreading centers at 20 deg 40 min S on the East Pacific Rise - Evidence for crustal rotations

    NASA Astrophysics Data System (ADS)

    Perram, Laura J.; Cormier, Marie-Helene; MacDonald, Ken C.

    1993-08-01

    We present the results of a magnetic study of a 225-km by 240-km area centered on the dueling propagating spreading centers located at 20 deg 40 min S on the East Pacific Rise. A majority of the data used were collected during a cruise aboard the Moana Wave research vessel during which continuous SeaMARC II coverage was obtained. These data were combined with additional data to produce an anomaly map which extends to anomaly-2-aged crust. A three-dimensional inversion in the presence of bathymetry was carried out for the area. The resulting magnetization distribution was interpreted and compared to side scan sonar and bathymetry data sets in order to determine the recent history of the discontinuity. The results indicate consistent asymmetric spreading faster to the east, discontinuous high magnetizations in the discordant zone associated with the discontinuity, and southward migration of the feature at a rate of 90-100 mm/yr between Jaramillo and Brunhes time (0.95 to 0.73 Ma) with slowing during the Brunhes to less than 10 mm/yr. An occurrence of an overlapping Jaramillo isochron on the west flank and a gap in that isochron on the east flank indicates a transfer of crust during this time period from the Nazca to the Pacific plate. Areas of oblique lineations possibly representing rotated crust were modeled using an inverse method which enables the specification of a nonuniform magnetization unit vector. Results suggest the occurrence of at least two episodes of crustal transfer from the Nazca plate to the Pacific plate.

  16. Spatial Correlation of Airborne Magnetic Anomalies with Reservoir Temperatures of Geothermal Fields, Western Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Ertekin, Can; Ekinci, Yunus Levent

    2013-04-01

    Geothermal areas in Western Anatolia are remarkably located throughout Büyük Menderes Graben (BMG) and Gediz Graben (GG). These E-W trending grabens have been subjected to N-E stretching since Miocene. Except for these major outcomes of the extensional forces, NE-SW oriented and relatively short grabens take place in Western Anatolia as well. Among them, BMG and GG are remarkable with topographic escarpments that reveal footwall of steeply-dipping active normal faults. They manifest themselves via numerous earthquakes and geothermal activity (fluid discharges from springs and wells). Geothermal discharges are aligned along the rims of E-W trending normal faults trending over detachment faults. Concerning BMG, geothermal manifestations extend along the northern sector of the graben. Geothermal reservoirs inside BMG are the limestone and conglomerate units within Neogene sediments and the marble-quartzite units within The Menderes Massif rocks. The main high and low enthalpy geothermal fields along BMG and their reservoir temperatures are as follows: Kızıldere (242°C), Germencik (232°C), Aydın-Ilıcabası (101°C), Yılmazköy (142°C), Salavatlı (171°C), Söke (26°C), Pamukkale (36°C), Karahayıt (59°C), Gölemezli (101°C) and Yenice (70°C). Through GG, reservoir temperatures decrease from east to west. Geothermal reservoirs inside GG are metamorphics and granodiorite of the Menderes Massif rocks. The Neogene sediments act as cap rock of the geothermal reservoirs. Geothermal fields inside the graben and their reservoir temperatures are as follows: Alaşehir (215°C), Salihli (155°C), Urganlı (85°C), Kurşunlu (135°C), Caferbey (150°C), Sart (100°C). In order to investigate the spatial correlation of magnetic anomalies and the reservoir temperatures of geothermal fields in the region, we analysed airborne magnetic data which were collected by General Directorate of Mineral Research and Exploration (MTA) of Turkey. Airborne magnetic data were taken

  17. Magnetic anomaly analysis of the Ionian Sea: Is it the oldest in-situ ocean fragment of the world?

    NASA Astrophysics Data System (ADS)

    Speranza, F.; Minelli, L.; Pignatelli, A.; Chiappini, M.

    2013-12-01

    It is well known that the Ionian Sea is characterized by thin (8-11 km) crystalline crust, thick (5-7 km) sedimentary cover, and low heat flow, typical for a Mesozoic (at least) basin. Yet seismic data have not yielded univocal interpretations, and a debate has developed on the oceanic vs. 'thinned continental' nature of the Ionian basin. Here we analyze the magnetic anomaly pattern of the Ionian Sea, and compare it to synthetic fields produced by a geopotential field generator, considering realistic crust geometry. The Ionian basin is mostly characterized by slightly negative magnetic residuals, and by a prominent positive (150 nT at sea level) 'B' anomaly at the northwestern basin margin. We first test continental crust models, considering a homogeneous crystalline crust with K=1x10-3, then a 5 km thick deep crustal layer of serpentinite (K=1x10-1). First model yields insignificant anomalies, while the second gives an anomaly pattern anti-correlated with the observed residuals. We subsequently test oceanic crust models, considering a 2 km thick 2A basaltic layer with K=5x10-3, magnetic remanence of 5 A/m, and a unique magnetic polarity (no typical oceanic magnetic anomaly stripes are apparent in the observed data set). Magnetic remanence directions were derived from Pangean-African paleopoles in the 290-190 Ma age window. Only reverse-polarity models reproduce the B anomaly, and among them the 220-230 Ma models best approximate magnetic features observed on the abyssal plain and at the western basin boundary. The Ionian Sea turns out to be the oldest preserved oceanic floor known so far. Reference Speranza, F., L. Minelli, A. Pignatelli, and M. Chiappini (2012), The Ionian Sea: The oldest in situ ocean fragment of the world?, J. Geophys. Res., 117, B12101, doi:10.1029/2012JB009475.

  18. High-temperature magnetic anomalies in Sr-doped La manganite structures

    SciTech Connect

    Potter, C.D.; Swiatek, M.; Mitchell, J.F.; Hinks, D.G.; Jorgensen, J.D.; Bader, S.D.; Argyriou, D.N.

    1996-12-31

    The temperature dependence of the magnetization M, susceptibility {chi}, and magnetoresistance MR for 3 perovskite-variant manganite structures were studied: monoclinic (x=0.075) and orthorhombic (x=0. 125) La{sub 1-x}Sr{sub x}MnO{sub 3}, and tetragonal layered La{sub 2- 2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} (x=0.4) with x also indicating the nominal fraction of Mn{sup 4+}. In each case, evidence is found for unusual magnetic states at temperatures T above their primary magnetic transitions. In the first case, the high-T {chi} deviates from Curie-Weiss expectations, in the second case the MR extends to high T, and in the last, M and {chi} exhibit short-range anomalies at high T. This suggests that a key feature of these systems is the existence of multiple magnetic energy scales, independent of structure, dimensionality, or doping levels.

  19. Preparation of magnetic anomaly profile and contour maps from DOE-NURE aerial survey data. Volume I. Processing procedures

    SciTech Connect

    Tinnel, E.P.; Hinze, W.J.

    1981-09-01

    Total intensity magnetic anomaly data acquired as a supplement to radiometric data in the DOE National Uranium Resource Evaluation (NURE) Program are useful in preparing regional profile and contour maps. Survey-contractor-supplied magnetic anomaly data are subjected to a multiprocess, computer-based procedure which prepares these data for presentation. This procedure is used to produce the following machine plotted maps of National Topographic Map Series quadrangle units at a 1:250,000 scale: (1) profile map of contractor-supplied magnetic anomaly data, (2) profile map of high-cut filtered data with contour levels of each profile marked and annotated on the associated flight track, (3) profile map of critical-point data with contour levels indicated, and (4) contour map of filtered and selected data. These quadrangle maps are supplemented with a range of statistical measures of the data which are useful in quality evaluation.

  20. Deciphering tectonic phases of the Amundsen Sea Embayment shelf, West Antarctica, from a magnetic anomaly grid

    NASA Astrophysics Data System (ADS)

    Gohl, Karsten; Denk, Astrid; Eagles, Graeme; Wobbe, Florian

    2013-02-01

    The Amundsen Sea Embayment (ASE), with Pine Island Bay (PIB) in the eastern embayment, is a key location to understanding tectonic processes of the Pacific margin of West Antarctica. PIB has for a long time been suggested to contain the crustal boundary between the Thurston Island block and the Marie Byrd Land block. Plate tectonic reconstructions have shown that the initial rifting and breakup of New Zealand from West Antarctica occurred between Chatham Rise and the eastern Marie Byrd Land at the ASE. Recent concepts have discussed the possibility of PIB being the site of one of the eastern branches of the West Antarctic Rift System (WARS). About 30,000 km of aeromagnetic data - collected opportunistically by ship-based helicopter flights - and tracks of ship-borne magnetics were recorded over the ASE shelf during two RV Polarstern expeditions in 2006 and 2010. Grid processing, Euler deconvolution and 2D modelling were applied for the analysis of magnetic anomaly patterns, identification of structural lineaments and characterisation of magnetic source bodies. The grid clearly outlines the boundary zone between the inner shelf with outcropping basement rocks and the sedimentary basins of the middle to outer shelf. Distinct zones of anomaly patterns and lineaments can be associated with at least three tectonic phases from (1) magmatic emplacement zones of Cretaceous rifting and breakup (100-85 Ma), to (2) a southern distributed plate boundary zone of the Bellingshausen Plate (80-61 Ma) and (3) activities of the WARS indicated by NNE-SSW trending lineaments (55-30 Ma?). The analysis and interpretation are also used for constraining the directions of some of the flow paths of past grounded ice streams across the shelf.

  1. Insights into magmatic processes and hydrothermal alteration of in situ superfast spreading ocean crust at ODP/IODP site 1256 from a cluster analysis of rock magnetic properties

    NASA Astrophysics Data System (ADS)

    Dekkers, Mark J.; Heslop, David; Herrero-Bervera, Emilio; Acton, Gary; Krasa, David

    2014-08-01

    analyze magnetic properties from Ocean Drilling Program (ODP)/Integrated ODP (IODP) Hole 1256D (6°44.1' N, 91°56.1' W) on the Cocos Plate in ˜15.2 Ma oceanic crust generated by superfast seafloor spreading, the only drill hole that has sampled all three oceanic crust layers in a tectonically undisturbed setting. Fuzzy c-means cluster analysis and nonlinear mapping are utilized to study down-hole trends in the ratio of the saturation remanent magnetization and the saturation magnetization, the coercive force, the ratio of the remanent coercive force and coercive force, the low-field magnetic susceptibility, and the Curie temperature, to evaluate the effects of magmatic and hydrothermal processes on magnetic properties. A statistically robust five cluster solution separates the data predominantly into three clusters that express increasing hydrothermal alteration of the lavas, which differ from two distinct clusters mainly representing the dikes and gabbros. Extensive alteration can obliterate magnetic property differences between lavas, dikes, and gabbros. The imprint of thermochemical alteration on the iron-titanium oxides is only partially related to the porosity of the rocks. Thus, the analysis complements interpretation based on electrofacies analysis. All clusters display rock magnetic characteristics compatible with an ability to retain a stable natural remanent magnetization suggesting that the entire sampled sequence of ocean crust can contribute to marine magnetic anomalies. Paleointensity determination is difficult because of the propensity of oxyexsolution during laboratory heating and/or the presence of intergrowths. The upper part of the extrusive sequence, the granoblastic dikes, and moderately altered gabbros may contain a comparatively uncontaminated thermoremanent magnetization.

  2. Investigation of the Crust of the Pannonian Basin, Hungary Using Low-Altitude CHAMP Horizontal Gradient Magnetic Anomalies

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.; Kis, Karoly I.; Puszta, Sandor; Wittmann, Geza; Kim, Hyung Rae; Toronyi, B.

    2011-01-01

    The Pannonian Basin is a deep intra-continental basin that formed as part of the Alpine orogeny. It is some 600 by 500 km in area and centered on Hungary. This area was chosen since it has one of the thinnest continental crusts in Europe and is the region of complex tectonic structures. In order to study the nature of the crustal basement we used the long-wavelength magnetic anomalies acquired by the CHAMP satellite. The SWARM constellation, scheduled to be launched next year, will have two lower altitude satellites flying abreast, with a separation of between ca. 150 to 200 km. to record the horizontal magnetic gradient. Since the CHAMP satellite has been in orbit for eight years and has obtained an extensive range of data, both vertically and horizontally there is a large enough data base to compute the horizontal magnetic gradients over the Pannonian Basin region using these many CHAMP orbits. We recomputed a satellite magnetic anomaly map, using the spherical-cap method of Haines (1985), the technique of Alsdorf et al. (1994) and from spherical harmonic coefficients of MF6 (Maus et aI., 2008) employing the latest and lowest altitude CHAMP data. We then computed the horizontal magnetic anomaly gradients (Kis and Puszta, 2006) in order to determine how these component data will improve our interpretation and to preview what the SW ARM mission will reveal with reference to the horizontal gradient anomalies. The gradient amplitude of an 1000 km northeast-southwest profile through our horizontal component anomaly map varied from 0 to 0.025 nT/km with twin positive anomalies (0.025 and 0.023 nT/km) separated by a sharp anomaly negative at o nT/km. Horizontal gradient indicate major magnetization boundaries in the crust (Dole and Jordan, 1978 and Cordell and Grauch, 1985). Our gradient anomaly was modeled with a twodimensional body and the anomaly, of some 200 km, correlates with a 200 km area of crustal thinning in the southwestern Pannonian Basin.

  3. GRM crustal magnetic anomalies: Separating the Lord Howe Rise and Norfolk Ridge submarine structures

    NASA Technical Reports Server (NTRS)

    Frey, H.

    1985-01-01

    Multiple source bodies often lie within the resolution element of the MAGSAT and POGO data. Small weak sources lying near larger stronger sources will tend to be missed, although they do contribute to the total observed anomaly. Lower elevation magnetic anomaly surveys such as GRM alleviate this problem through the combined effects of significantly greater resolution and stronger signal amplitude. This permits the detection of smaller source bodies, and analysis of their structure and nature. The improvement a GRM will provide is demonstrated in the Lord Howe Rise/Norfolk Ridge area east of Australia, between the Tasman Sea and south Fiji Basin. The submarine features origin have important plate tectonic implications. The Lord Howe Rise (LHR) is a continental fragment broken off from Australia by the opening of the Tasman Sea. It is a wide, shallow structure lying between 160 and 165 deg longitude at 23 to 37 deg S latitude. Seismic refraction data show the LHR crust extending to depths in excess of 20 km.

  4. Electromagnetic particle-in-cell simulations of the solar wind interaction with lunar magnetic anomalies.

    PubMed

    Deca, J; Divin, A; Lapenta, G; Lembège, B; Markidis, S; Horányi, M

    2014-04-18

    We present the first three-dimensional fully kinetic and electromagnetic simulations of the solar wind interaction with lunar crustal magnetic anomalies (LMAs). Using the implicit particle-in-cell code iPic3D, we confirm that LMAs may indeed be strong enough to stand off the solar wind from directly impacting the lunar surface forming a mini-magnetosphere, as suggested by spacecraft observations and theory. In contrast to earlier magnetohydrodynamics and hybrid simulations, the fully kinetic nature of iPic3D allows us to investigate the space charge effects and in particular the electron dynamics dominating the near-surface lunar plasma environment. We describe for the first time the interaction of a dipole model centered just below the lunar surface under plasma conditions such that only the electron population is magnetized. The fully kinetic treatment identifies electromagnetic modes that alter the magnetic field at scales determined by the electron physics. Driven by strong pressure anisotropies, the mini-magnetosphere is unstable over time, leading to only temporal shielding of the surface underneath. Future human exploration as well as lunar science in general therefore hinges on a better understanding of LMAs.

  5. High-temperature magnetization anomaly in Co/Ag/Si(1 1 1) ultrathin films

    NASA Astrophysics Data System (ADS)

    Lin, J. Y.; Tsay, J. S.; Liou, Y.; Yao, Y. D.; Lee, S. F.; Yang, C. S.

    2000-01-01

    High-temperature magnetic properties of ultrathin Co/Ag/Si(1 1 1) films were studied by surface magneto-optic Kerr effect (SMOKE) in an ultra-high vacuum (UHV) chamber with a background pressure less than 1×10 -10 Torr. A 6 mono-layer (ML) Co layer was deposited on Si(1 1 1) surface with Ag as a buffer layer with the thickness being varied between 0 and 5.6 ML. Both polar and longitudinal MOKE (P- and LMOKE) were studied as a function of temperature between 300 and 550 K. It is interesting to note that the Kerr intensity of LMOKE for Co/Ag/Si(1 1 1) thin film with Ag thickness of 2.8 and 5.6 ML decreases with increasing temperature and vanishes near 475 K; it shows up again in the opposite direction above 475 K before vanishing again at 550 K. This was not observed for samples with Ag thickness less than 2.8 ML. This indicates that the Ag buffer layer is playing an important role in the variation of magnetization of Co at high temperature; in other words, stress or small Co/Co-Ag clusters formed by the diffusion between Ag and Co layer at high temperature may cause the magnetization anomaly.

  6. Magnetic investigation and 2½ D gravity profile modelling across the Beattie magnetic anomaly in the southeastern Karoo Basin, South Africa

    NASA Astrophysics Data System (ADS)

    Baiyegunhi, Christopher; Gwavava, Oswald

    2017-02-01

    The southeastern Karoo Basin is considered to be one of the most prospective areas for shale gas exploration in South Africa. An interesting magnetic anomaly, the Beattie magnetic anomaly (BMA), and geologic intrusions are seen on the magnetic map. To date, the source of the BMA and interconnectivity of the igneous intrusions are not well understood. In this study, we investigate the interconnectivity of the igneous intrusions and possible location of the source of the BMA using gravity and magnetic methods. The gravity model results showed that igneous intrusions are interconnected at depth, which probably pose threat by increasing the risk of fracking the Karoo for shale gas exploration. The magnetic results revealed that the BMA becomes stronger with depth. The average depths to the top of the shallow and deep magnetic sources were estimated to be approximately 0.6 and 15 km, respectively.

  7. Study of the nanosiderite from ferruginous quartzites of Kursk magnetic anomaly by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Zhukhlistov, A. P.; Novikov, V. M.

    2016-11-01

    Biogenic siderite consisting of equally crystallographically oriented disklike nanoparticles 5-20 nm in size has been found (using transmission electron microscopy) in oxidized ferruginous quartzites (jaspilites) of the Lebedinsky field of the Kursk magnetic anomaly. Based on microdiffraction data and highresolution images, lowering of the siderite structure symmetry from Roverline 3 c to Roverline 3 has been established for the first time. A siderite structure model is proposed to explain this fact. Within this model, vacancies formed as a result of oxidation of some part of Fe2+ cations to the Fe3+ state are ordered in one of two nonequivalent octahedral sites. Identical crystallographic orientation and nanoparticle morphology have been established for coexisting siderite and hematite. It is suggested that the revealed specific features of nanosiderite are related to its biogenic origin.

  8. Investigating tectonic and bathymetric features of the Indian Ocean using MAGSAT magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Lazarewicz, A. R.; Sailor, R. V. (Principal Investigator)

    1982-01-01

    MAGSAT Investigator-B tapes were preprocessed by (1) removing all data points with obvious erroneous values and location errors; (2) removing smaller spikes (typically 15 nT or more), and deleting data tracks with fewer than 20 points; and (3) removing a linear trend from each track. The remaining data were recorded on tape for use by the equivalent source mapping (ESMAP) program which uses a least squares algorithm to fit the magnetization parameter of the grid of equivalent source dipoles in the crust to satellite data acquired at different times and locations. ESMAP was implemented on the TASC computing system and modified to read preprocessed MAGSAT tapes and interface with TASC plotting software. Some verification of the software was accomplished. Gridded 1-degree mean values of gravity anomaly and sea surface undulation computed from SEASAT radar altimeter were obtained and brought on line.

  9. Remanent and Induced Magnetic Anomalies over the Bjerkreim-Sokndal Layered Intrusion: Effects from Crystal Fractionation and Magma Recharge

    NASA Astrophysics Data System (ADS)

    McEnroe, S. A.; Brown, L. L.; Robinson, P.

    2013-12-01

    The Bjerkreim-Sokndal (BKS) norite-quartz mangerite layered intrusion is part of the early Neoproterozoic Rogaland Anorthosite Province intruded into the Fennoscandian shield in south Norway at ~930 Ma. The BKS is exposed over an area of 230 km2 with a thickness of ~7000m and is of economic interest for hemo-ilmenite, magnetite and apatite deposits. From the point of view of magnetic minerals, in the course of fractional crystallization and magma evolution, the ilmenite becomes less Fe3+-rich reflected by a change from ilmenite with hematite exsolution to nearly pure ilmenite. Magnetite starts to crystallize relatively late in the intrusive history, but its crystallization is interrupted by influxes of more primitive magma containing hemo-ilmenite. The variations in aeromagnetic and ground-magnetic anomalies measured over the BKS can be explained in terms of the magnetic properties of NRM, susceptibility, and hysteresis. Magnetic properties are correlated with the oxide mineralogy and mineral chemistry. Early layers in the intrusion contain hemo-ilmenite. As the magma evolved and magnetite started to crystallize, this caused a distinct change over the layering from remanence-controlled negative anomalies to induced positive anomalies. When new, more primitive magma was injected into the system, hemo-ilmenite returned as the major oxide and the resulting magnetic anomalies are again negative. The most dramatic change in the magnetic signature is in the upper part of the intrusion in MCU IVe, where magnetite became a well established cumulate phase as indicated by susceptibility, but its induced magnetization is overcome by large NRM's associated either with hemo-ilmenite or with hemo-ilmenite and magnetite exsolved from pyroxenes. The average natural remanent magnetizations change from ~3 A/m in MCU IVd, to 15 A/m in MCU IVe, and back to 2 A/m in the overlying MCU IVf, producing a strong negative remanent anomaly that has been followed along strike for at least 20

  10. Geophysical Surveying of Shallow Magnetic Anomalies Using the iPhone Magnetometer

    NASA Astrophysics Data System (ADS)

    Opdyke, P.; Dudley, C.; Louie, J. N.

    2012-12-01

    This investigation examined whether the 3-axis Hall-effect magnetometer in the Apple iPhone 3GS can function as an effective shallow magnetic survey instrument. The xSensor Pro app from Crossbow Systems allows recoding of all three sensor components along with the GPS location, at a frequency of 1.0, 4.0, 16.0, and 32.0 Hz. If the iPhone proves successful in collecting useful magnetic data, then geophysicists and especially educators would have a new tool for high-density geophysical mapping. No-contract iPhones that can connect with WiFi can be obtained for about $400, allowing deployment of large numbers of instruments. iPhones with the xSensor Pro app surveyed in parallel with an Overhauser GEM system magnetometer (1 nT sensitivity) to test this idea. Anderson Bay, located on the Pyramid Lake Paiute Reservation, provided a rural survey location free from cultural interference. xSensor Pro, logged each component's intensity and the GPS location at a frequency of four measurements per second. Two Overhauser units functioned as a base unit and a roving unit. The roving unit collected total field at set points located with a handheld GPS. Comparing the total field computed from the iPhone components against that collected by the Overhauser establishes the level of anomalies that the iPhone can detect. iPhone total-field measurements commonly vary by 200 nT from point to point, so a spatial-temporal average over 25 seconds produces a smoothed signal for comparison. Preliminary analysis of the iPhone results show that the data do not accurately correlate to the total field collected by the Overhauser for any anomaly of less than 200 nT.

  11. Controls on Martian Hydrothermal Systems: Application to Valley Network and Magnetic Anomaly Formation

    NASA Technical Reports Server (NTRS)

    Harrison, Keith P.; Grimm, Robert E.

    2002-01-01

    Models of hydrothermal groundwater circulation can quantify limits to the role of hydrothermal activity in Martian crustal processes. We present here the results of numerical simulations of convection in a porous medium due to the presence of a hot intruded magma chamber. The parameter space includes magma chamber depth, volume, aspect ratio, and host rock permeability and porosity. A primary goal of the models is the computation of surface discharge. Discharge increases approximately linearly with chamber volume, decreases weakly with depth (at low geothermal gradients), and is maximized for equant-shaped chambers. Discharge increases linearly with permeability until limited by the energy available from the intrusion. Changes in the average porosity are balanced by changes in flow velocity and therefore have little effect. Water/rock ratios of approximately 0.1, obtained by other workers from models based on the mineralogy of the Shergotty meteorite, imply minimum permeabilities of 10(exp -16) sq m2 during hydrothermal alteration. If substantial vapor volumes are required for soil alteration, the permeability must exceed 10(exp -15) sq m. The principal application of our model is to test the viability of hydrothermal circulation as the primary process responsible for the broad spatial correlation of Martian valley networks with magnetic anomalies. For host rock permeabilities as low as 10(exp -17) sq m and intrusion volumes as low as 50 cu km, the total discharge due to intrusions building that part of the southern highlands crust associated with magnetic anomalies spans a comparable range as the inferred discharge from the overlying valley networks.

  12. The Effect of Dissipation Mechanism and Guide Field Strength on X-line Spreading in 3D Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Shepherd, Lucas; Cassak, P.; Drake, J.; Gosling, J.; Phan, T.; Shay, M. A.

    2013-07-01

    In two-ribbon flares, the fact that the ribbons separate in time is considered evidence of magnetic reconnection. However, in addition to the ribbons separating, they can also elongate (as seen in animations of, for example, the Bastille Day flare). The elongation is undoubtedly related to the reconnection spreading in the out-of-plane direction. Indeed, naturally occurring magnetic reconnection generally begins in a spatially localized region and spreads in the direction perpendicular to the reconnection plane as time progresses. For example, it was suggested that X-line spreading is necessary to explain the observation of X-lines extending more than 390 Earth radii (Phan et al., Nature, 404, 848, 2006), and has been seen in reconnection experiments. A sizeable out-of-plane (guide) magnetic field is present at flare sites and in the solar wind. Here, we study the effect of dissipation mechanism and the strength of the guide field has on X-line spreading. We present results from three-dimensional numerical simulations of magnetic reconnection, comparing spreading with the Hall term to spreading with anomalous resistivity. Applications to solar flares and magnetic reconnection in the solar wind will be discussed.

  13. NMR investigation of the Knight shift anomaly in CeIrIn5 at high magnetic fields

    NASA Astrophysics Data System (ADS)

    Shockley, A. C.; apRoberts-Warren, N.; Nisson, D. M.; Kuhns, P. L.; Reyes, A. P.; Yuan, S.; Curro, N. J.

    2013-08-01

    We report nuclear magnetic resonance Knight shift data in the heavy-fermion material CeIrIn5 at fields up to 30 T. The Knight shift of the In displays a strong anomaly, and we analyze the results using two interpretations. We find that the Kondo lattice coherence temperature and the effective mass of the heavy electrons remain largely unaffected by the magnetic field, despite the fact that the Zeeman energy is of the order of the coherence temperature.

  14. Characterization of Lunar Swirls at Mare Ingenii: A Model for Space Weathering at Magnetic Anomalies

    NASA Technical Reports Server (NTRS)

    Kramer, Georgianna Y.; Combe, Jean-Philippe; Harnett, Erika M.; Hawke, Bernard Ray; Noble, Sarah K.; Blewett, David T.; McCord, Thomas B.; Giguere, Thomas A.

    2011-01-01

    Analysis of spectra from the Clementine ultraviolet-visible and near-infrared cameras of small, immature craters and surface soils both on and adjacent to the lunar swirls at Marc Ingenii has yielded the following conclusions about space weathering at a magnetic anomaly. (l) Despite having spectral characteristics of immaturity, the lunar swirls arc not freshly exposed surfaces. (2) The swirl surfaces arc regions of retarded weathering, while immediately adjacent regions experience accelerated weathering, (3) Weathering in the off-swirl regions darkens and flattens the spectrum with little to no reddening, which suggests that the production of larger (greater than 40 nm) nanophase iron dominates in these locations as a result of charged particle sorting by the magnetic field. Preliminaty analysis of two other lunar swirl regions, Reiner Gamma and Mare Marginis, is consistent with our observations at Mare Ingenii. Our results indicate that sputtering/vapor deposition, implanted solar wind hydrogen, and agglutination share responsibility for creating the range in npFe(sup 0) particle sizes responsible for the spectral effects of space weathering.

  15. Geomagnetic intensity variations over the past 780 kyr obtained from near-seafloor magnetic anomalies.

    PubMed

    Gee, J S; Cande, S C; Hildebrand, J A; Donnelly, K; Parker, R L

    2000-12-14

    Knowledge of past variations in the intensity of the Earth's magnetic field provides an important constraint on models of the geodynamo. A record of absolute palaeointensity for the past 50 kyr has been compiled from archaeomagnetic and volcanic materials, and relative palaeointensities over the past 800 kyr have been obtained from sedimentary sequences. But a long-term record of geomagnetic intensity should also be carried by the thermoremanence of the oceanic crust Here we show that near-seafloor magnetic anomalies recorded over the southern East Pacific Rise are well correlated with independent estimates of geomagnetic intensity during the past 780 kyr. Moreover, the pattern of absolute palaeointensity of seafloor glass samples from the same area agrees with the well-documented dipole intensity pattern for the past 50 kyr. A comparison of palaeointensities derived from seafloor glass samples with global intensity variations thus allows us to estimate the ages of surficial lava flows in this region. The record of geomagnetic intensity preserved in the oceanic crust should provide a higher-time-resolution record of crustal accretion processes at mid-ocean ridges than has previously been obtainable.

  16. Modelling the gravity and magnetic field anomalies of the Chicxulub crater

    NASA Technical Reports Server (NTRS)

    Aleman, C. Ortiz; Pilkington, M.; Hildebrand, A. R.; Roest, W. R.; Grieve, R. A. F.; Keating, P.

    1993-01-01

    The approximately 180-km-diameter Chicxulub crater lies buried by approximately 1 km of sediment on the northwestern corner of the Yucatan Peninsula, Mexico. Geophysical, stratigraphic and petrologic evidence support an impact origin for the structure and biostratigraphy suggests that a K/T age is possible for the impact. The crater's location is in agreement with constraints derived from proximal K/T impact-wave and ejecta deposits and its melt-rock is similar in composition to the K/T tektites. Radiometric dating of the melt rock reveals an age identical to that of the K/T tektites. The impact which produced the Chicxulub crater probably produced the K/T extinctions and understanding the now-buried crater will provide constraints on the impact's lethal effects. The outstanding preservation of the crater, the availability of detailed gravity and magnetic data sets, and the two-component target of carbonate/evaporites overlying silicate basement allow application of geophysical modeling techniques to explore the crater under most favorable circumstances. We have found that the main features of the gravity and magnetic field anomalies may be produced by the crater lithologies.

  17. Subsurface faults detection based on magnetic anomalies investigation: A field example at Taba protectorate, South Sinai

    NASA Astrophysics Data System (ADS)

    Khalil, Mohamed H.

    2016-08-01

    Quantitative interpretation of the magnetic data particularly in a complex dissected structure necessitates using of filtering techniques. In Taba protectorate, Sinai synthesis of different filtering algorithms was carried out to distinct and verifies the subsurface structure and estimates the depth of the causative magnetic sources. In order to separate the shallow-seated structure, filters of the vertical derivatives (VDR), Butterworth high-pass (BWHP), analytic signal (AS) amplitude, and total horizontal derivative of the tilt derivative (TDR_THDR) were conducted. While, filters of the apparent susceptibility and Butterworth low-pass (BWLP) were conducted to identify the deep-seated structure. The depths of the geological contacts and faults were calculated by the 3D Euler deconvolution. Noteworthy, TDR_THDR was independent of geomagnetic inclination, significantly less susceptible to noise, and more sensitive to the details of the shallow superimposed structures. Whereas, the BWLP proved high resolution capabilities in attenuating the shorter wavelength of the near surface anomalies and emphasizing the longer wavelength derived from deeper causative structure. 3D Euler deconvolution (SI = 0) was quite amenable to estimate the depths of superimposed subsurface structure. The pattern, location, and trend of the deduced shallow and deep faults were conformed remarkably to the addressed fault system.

  18. The Bowser and Sustut Basins, Northern British Columbia, Canada: Insights From Analysis of Magnetic Anomaly Data.

    NASA Astrophysics Data System (ADS)

    Baker, J.; Lowe, C.

    2005-12-01

    The Bowser and Sustut basins occupy an area of more than 60,000 km2 in northern British Columbia, Canada. They comprise three, dominantly sedimentary, stratigraphic successions, in part overlapping in age: the Bowser Lake Group, the Skeena Group, and the Sustut Group. These three successions overlie arc volcanic and volcaniclastic strata of Stikinia, an allochtonous island arc terrane that accreted to the western margin of North America in the Early Jurassic to early Middle Jurassic. All three basin successions and underlying Stikinia were deformed during development of a thin-skinned fold and thrust belt (the Skeena Fold and Thrust Belt) in Cretaceous and possibly into earliest Tertiary time. Recently, the basins have been the focus of intense geological studies which have resulted in major revisions to the stratigraphic and structural framework of the basins and demonstrated that they have significantly higher petroleum potential than had been previously recognized. To advance these new findings further requires better imaging of the three-dimensional geometry and architecture of the basins. In this study we harness existing magnetic anomaly data to provide the first quantitative estimates of sedimentary thickness across the entire extents of both basins. Our results, which are in general in accord with geological interpretations, indicate that basin-fill is relatively thin and fairly uniform in the Sustut Basin (2.5-3 km), but highly variable in the Bowser Basin, ranging from less than 2 km to more than 6 km. Overall, sedimentary fill is thicker in the northern half of Bowser Basin compared to the south and is typically less than 2 km near the basins northern, western and southern margins. In addition, we demonstrate how a large, buried intrusion beneath the northeast part of Bowser Basin can account for an observed magnetic anomaly and explain the high coalification gradients and localized high maturation levels of the overlying sedimentary rocks. Neither of

  19. Magnetic Resonance Imaging Analysis of Caudal Regression Syndrome and Concomitant Anomalies in Pediatric Patients

    PubMed Central

    Boruah, Deb K; Dhingani, Dhaval D; Achar, Sashidhar; Prakash, Arjun; Augustine, Antony; Sanyal, Shantiranjan; Gogoi, Manoj; Mahanta, Kangkana

    2016-01-01

    Objective: The aim of this study was to evaluate the magnetic resonance imaging (MRI) findings of caudal regression syndrome (CRS) and concomitant anomalies in pediatric patients. Materials and Methods: A hospital-based cross-sectional retrospective study was conducted. The study group comprised 21 pediatric patients presenting to the Departments of Radiodiagnosis and Pediatric Surgery in a tertiary care hospital from May 2011 to April 2016. All patients were initially evaluated clinically followed by MRI. Results: In our study, 21 pediatric patients were diagnosed with sacral agenesis/dysgenesis related to CRS. According to the Pang's classification, 2 (9.5%) patients were Type I, 5 (23.8%) patients were Type III, 7 (33.3%) patients were Type IV, and 7 (33.3%) patients were of Type V CRS. Clinically, 17 (81%) patients presented with urinary incontinence, 6 (28.6%) with fecal incontinence, 9 patients (42.9%) had poor gluteal musculatures and shallow intergluteal cleft, 7 (33.3%) patients had associated subcutaneous mass over spine, and 6 (28.6%) patients presented with distal leg muscle atrophy. MRI showed wedge-shaped conus termination in 5 (23.8%) patients and bulbous conus termination in 3 (14.3%) patients above the L1 vertebral level falling into Group 1 CRS while 7 (33.3%) patients had tethered cord and 6 (28.6%) patients had stretched conus falling into Group 2 CRS. Conclusion: MRI is the ideal modality for detailed evaluation of the status of the vertebra, spinal cord, intra- and extra-dural lesions and helps in early diagnosis, detailed preoperative MRI evaluation and assessing concomitant anomalies and guiding further management with early institution of treatment to maximize recovery. PMID:27833778

  20. 3D Electromagnetic Particle-in-Cell simulations of the solar wind interaction with lunar magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Deca, J.; Lapenta, G.; Divin, A. V.; Lembege, B.; Markidis, S.

    2013-12-01

    Unlike the Earth and Mercury, our Moon has no global magnetic field and is therefore not shielded from the impinging solar wind by a magnetosphere. However, lunar magnetic field measurements made by the Apollo missions provided direct evidence that the Moon has regions of small-scale crustal magnetic fields, ranging up to a few 100km in scale size with surface magnetic field strengths up to hundreds of nanoTeslas. More recently, the Lunar Prospector spacecraft has provided high-resolution observations allowing to construct magnetic field maps of the entire Moon, confirming the earlier results from Apollo, but also showing that the lunar plasma environment is much richer than earlier believed. Typically the small-scale magnetic fields are non-dipolar and rather tiny compared to the lunar radius and mainly clustered on the far side of the moon. Using iPic3D we present the first 3D fully kinetic and electromagnetic Particle-in-Cell simulations of the solar wind interaction with lunar magnetic anomalies. We study the behaviour of a dipole model with variable surface magnetic field strength under changing solar wind conditions and confirm that lunar crustal magnetic fields may indeed be strong enough to stand off the solar wind and form a mini-magnetosphere, as suggested by MHD and hybrid simulations and spacecraft observations. 3D-PIC simulations reveal to be very helpful to analyze the diversion/braking of the particle flux and the characteristics of the resulting particles accumulation. The particle flux to the surface is significantly reduced at the magnetic anomaly, surrounded by a region of enhanced density due to the magnetic mirror effect. Second, the ability of iPic3D to resolve all plasma components (heavy ions, protons and electrons) allows to discuss in detail the electron physics leading to the highly non-adiabatic interactions expected as well as the implications for solar wind shielding of the lunar surface, depending on the scale size (solar wind protons

  1. Calibration of Pre-M25 Marine Magnetic Anomalies: Magnetic Polarity Composite of ýLate Callovian Through Kimmeridgian

    NASA Astrophysics Data System (ADS)

    Przybylski, P. A.; Ogg, J. G.

    2007-12-01

    Ammonite-zoned successions have yielded a composite magnetic polarity pattern ýspanning latest Callovian (lamberti ammonite Zone) through Late Kimmeridgian ýý(acanthicum Zone) that confirms marine magnetic anomalies M37 through to M24 ýinterpreted by deep-tow and other magnetic surveys in the western Pacific. This pattern ýwas constructed after thermal demagnetization of over 1000 samples from over 30 ýsections in Poland, British Isles, France and Spain. Polish sections include thick ýammonite-zoned limestone formations of the Krakow-Czestochowa-Wielun Upland and ýHoly-Cross Mountains. British limestone and clay formations were investigated in ýEngland (Dorset and Yorkshire) and in Scotland (the Isle of Skye). The sections include ýcandidates for the global stratotypes for the Callovian-Oxfordian and Oxfordian-ýKimmeridgian stage boundaries. All British and most of the Polish-French-Spanish ýsections are calibrated to ammonite biostratigraphy at the subzone level (Boreal-ýSubboreal realm and Sub-Mediterranean realm, respectively) and to regional sequence ýstratigraphy. The independent Boreal-Subboreal and Sub-Mediterranean composites of ýmagnetic polarity are consistent, and the main features of the modeled pre-M25 marine ýmagnetics can be calibrated. ý The Callovian-Oxfordian boundary (base of Quenstedtoceras mariae Zone) occurs in a ýnarrow normal-polarity subzone correlated to polarity subchron M36a of the western ýPacific magnetic polarity pattern. The beginning of the Middle and the Late Oxfordian ýsubstages as defined in the Sub-Mediterranean province in Poland correspond ýapproximately to M33 and M29 of the Pacific M-sequence. The placement of the ýOxfordian- Kimmeridgian boundary in the Sub-Boreal ammonite zonation (base of ýPictonia baylei Zone) is at the beginning of the M27r polarity zone. This is significantly ýolder than the traditional placement of the Oxfordian-Kimmeridgian boundary in the ýSub-Mediterranean zonation (base of

  2. Magnetic anomalies associated with abundant production of pyrrhotite in a sulfide deposit in the Okinawa Trough, Japan

    NASA Astrophysics Data System (ADS)

    Honsho, Chie; Yamazaki, Toshitsugu; Ura, Tamaki; Okino, Kyoko; Morozumi, Haruhisa; Ueda, Satoshi

    2016-11-01

    We report here results from a deep-sea magnetic survey using an autonomous underwater vehicle over the Hakurei hydrothermal site, in the middle Okinawa Trough. Magnetic inversion revealed that the Hakurei site is associated with well-defined high-magnetization zones distributed within a broad low-magnetization zone. Results from rock magnetic measurements, performed on sulfide ore samples obtained by drilling, showed that some samples possessed extremely high natural remanent magnetization (NRM) (as much as 6.8-953.0 A/m), although most of the measured samples had much lower NRM. These high-NRM samples were characterized by high Königsberger ratios (101-103), indicating much larger NRM than induced magnetization, and contained pyrrhotite as the only magnetic mineral. This suggests that NRM carried by pyrrhotite is the source of the observed magnetic anomalies. The wide range of NRM intensity was considered to be due to a highly heterogeneous distribution of pyrrhotite, because pyrrhotite was commonly identified in both the high-NRM and low-NRM samples. Pyrrhotite production may have been occasionally drastically increased, with highly magnetic ores formed as a result. Rapid burial of active vents may result in the creation of an extensive reducing environment under the seafloor, which is favorable to pyrrhotite production, and may also prevent oxidation of pyrrhotite by isolating it from seawater. Because the magnetization intensity of sulfide ores was highly variable, it would not be straightforward to estimate the quantity of ore deposits from the magnetic anomalies. Nevertheless, this study demonstrates the usefulness of magnetic surveys in detecting hydrothermal deposits.

  3. An earthquake from space: detection of precursory magnetic anomalies from Swarm satellites before the 2015 M8 Nepal Earthquake

    NASA Astrophysics Data System (ADS)

    De Santis, A.; Balasis, G.; Pavón-Carrasco, F. J.; Cianchini, G.; Mandea, M.

    2015-12-01

    A large earthquake of around 8 magnitude occurred on 25 April 2015, 06:26 UTC, with epicenter in Nepal, causing more than 9000 fatalities and devastating destruction. The contemporary orbiting in the topside ionosphere of the three Swarm satellites by ESA makes it possible to look for possible pre-earthquake magnetic anomalous signals, likely due to some lithosphere-atmosphere-ionosphere (LAI) coupling. First, a wavelet analysis has been performed during the same day of the earthquake (from the external magnetic point of view, an exceptionally quiet day) with the result that a ULF anomalous and persisting signal (from around 3 to 6 UTC), is clearly detected before the earthquake. After this single-spot analysis, we performed a more extensive analysis for two months around the earthquake occurrence, to confirm or refute the cause-effect relationship. From the series of the detected magnetic anomalies (during night and magnetically quiet times) from Swarm satellites, we show that the cumulative numbers of anomalies follows the same typical power-law behavior of a critical system approaching its critical time, in our case, the large seismic event of 25 April, 2015, and then it recovers as the typical recovery phase after a large earthquake. The impressive similarity of this behavior with the analogous of seismic data analysis, provides strong support to the lithospheric origin of the satellite magnetic anomalies, as due to the LAI coupling during the preparation phase of the Nepal earthquake.

  4. Current disruption and its spreading in collision-less magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Jain, Neeraj; Buechner, Joerg; Dorfman, Seth; Ji, Hantao; Sharma, A. Surjalal; Max-Planck/Princeton CenterPlasma Physics Collaboration

    2013-10-01

    Recent magnetic reconnection experiments (MRX) [Dorfman et al., Geophys. Res. Lett. 40, 233 (2012)] have disclosed current disruption in the absence of guide field. During current disruption in MRX, current density and total out-of-reconnection-plane current drop simultaneous with a rise in out-of-reconnection-plane electric field. Here we show that current disruption is an intrinsic property of dynamic formation of X-point configuration of magnetic field in magnetic reconnection, independent of the model used for plasma description and of dimensionality (2-D or 3-D) of reconnection. An analytic expression for the current drop is derived from Ampere's equation and its predictions are verified by 2-D and 3-D electron-magnetohydrodynamic (EMHD) simulations. Three dimensional EMHD simulations show that the current disruption due to localized reconnection spreads along the direction of electron flow with a speed which depends on the wave number of the perturbation. The implications of these results for MRX and other reconnection experiments will be presented. This work was partially funded by the Max-Planck/Princeton Center for Plasma Physics.

  5. Negative magnetic anomaly over Mt. Resnik, a subaerially erupted volcanic peak beneath the West Antarctic Ice Sheet

    USGS Publications Warehouse

    Behrendt, John C.; Finn, C.; Morse, D.L.; Blankenship, D.D.

    2006-01-01

    Mt. Resnik is one of the previously reported 18 subaerially erupted volcanoes (in the West Antarctic rift system), which have high elevation and high bed relief beneath the WAIS in the Central West Antarctica (CWA) aerogeophysical survey. Mt. Resnik lies 300 m below the surface of the West Antarctic Ice Sheet (WAIS); it has 1.6 km topographic relief, and a conical form defined by radar ice-sounding of bed topography. It has an associated complex negative magnetic anomaly revealed by the CWA survey. We calculated and interpreted magnetic models fit to the Mt. Resnik anomaly as a volcanic source comprising both reversely and normally magnetized (in the present field direction) volcanic flows, 0.5-2.5-km thick, erupted subaerially during a time of magnetic field reversal. The Mt. Resnik 305-nT anomaly is part of an approximately 50- by 40-km positive anomaly complex extending about 30 km to the west of the Mt. Resnik peak, associated with an underlying source complex of about the same area, whose top is at the bed of the WAIS. The bed relief of this shallow source complex has a maximum of only about 400 m, whereas the modeled source is >3 km thick. From the spatial relationship we interpret that this source and Mt Resnik are approximately contemporaneous. Any subglacially (older?) erupted edifices comprising hyaloclastite or other volcanic debris, which formerly overlaid the source to the west, were removed by the moving WAIS into which they were injected as is the general case for the ???1000 volcanic centers at the base of the WAIS. The presence of the magnetic field reversal modeled for Mt. Resnik may represent the Bruhnes-Matayama reversal at 780 ka (or an earlier reversal). There are ???100 short-wavelength, steep-gradient, negative magnetic anomalies observed over the West Antarctic Ice Sheet (WAIS), or about 10% of the approximately 1000 short-wavelength, shallow-source, high-amplitude (50- >1000 nT) "volcanic" magnetic anomalies in the CWA survey. These

  6. Rock Magnetic and Remanence Properties of Synthetic Martian Basaltic Intrusions: Implications for Mars crustal anomalies

    NASA Astrophysics Data System (ADS)

    Cuomo, D. M.; Petrochilos, L.; Brachfeld, S. A.; Bowles, J. A.; Hammer, J. E.

    2009-12-01

    Two basalts deemed relevant to the crust of Mars were synthesized to examine contrasts in rock magnetic and remanence properties following identical thermal histories and oxygen fugacity conditions. The composition denoted T-type is rich in Al and poor in Fe, reflecting constraints provided by thermal emission spectroscopy that the Martian crust is somewhat terrestrial in character. The M-type composition is poor in Al and rich in Fe, reflecting the composition of basaltic liquid in equilibrium with Martian meteorite phase assemblages. The two compositions are identical with respect to MgO, SiO2, and TiO2. Batches of each composition were cooled from > 1200 °C to 1070 °C at 4 °C/h and annealed at 1070°C for 100 h, then quenched. Samples were then held at 650°C for periods ranging from 21 to 158 days under quartz-fayalite-magnetite (QFM) fO2 buffer conditions, then quenched. The experimental conditions are germane to shallow igneous intrusions, which might be a significant volumetric fraction of the Martian crust and potential carriers of crustal magnetic anomalies, and provide an important contrast to a previous set of fast-cooled (3-230 °C/h) basalts our group performed on the same two compositions. M-type samples contain Fe-Ti-Al-Mg oxide grains 40-50 μm in diameter with skeletal morphologies. T-type samples contain equant euhedral Fe-Ti-Al-Mg oxides with grain diameters ranging from 15-30 μm as well as elongated anhedral ilmenite grains. For M-type samples both the starting material and the samples annealed at 650 °C have narrow multidomain hysteresis loops and similar hysteresis parameters. T-type starting materials and samples annealed at 650 °C have pseudo single domain (PSD) hysteresis loops, but the annealed samples plot lower and to the right within the PSD field on a Day plot, indicating coarser magnetic grains. Alternating field demagnetization of anhysteretic remanent magnetization (ARM) shows median destructive fields < 10 mT. M-type samples

  7. Regional magnetic anomalies, crustal strength, and the location of the northern Cordilleran fold-and-thrust belt

    USGS Publications Warehouse

    Saltus, R.W.; Hudson, T.L.

    2007-01-01

    The northern Cordilleran fold-and-thrust belt in Canada and Alaska is at the boundary between the broad continental margin mobile belt and the stable North American craton. The fold-and-thrust belt is marked by several significant changes in geometry: cratonward extensions in the central Yukon Territory and northeastern Alaska are separated by marginward re-entrants. These geometric features of the Cordilleran mobile belt are controlled by relations between lithospheric strength and compressional tectonic forces developed along the continental margin. Regional magnetic anomalies indicate deep thermal and compositional characteristics that contribute to variations in crustal strength. Our detailed analysis of one such anomaly, the North Slope deep magnetic high, helps to explain the geometry of the fold-and-thrust front in northern Alaska. This large magnetic anomaly is inferred to reflect voluminous mafic magmatism in an old (Devonian?) extensional domain. The presence of massive amounts of malic material in the lower crust implies geochemical depletion of the underlying upper mantle, which serves to strengthen the lithosphere against thermal erosion by upper mantle convection. We infer that deep-source magnetic highs are an important indicator of strong lower crust and upper mantle. This stronger lithosphere forms buttresses that play an important role in the structural development of the northern Cordilleran fold-and-thrust belt. ?? 2007 The Geological Society of America.

  8. Middle atmospheric electrodynamic modification by particle precipitation at the South Atlantic magnetic anomaly

    NASA Technical Reports Server (NTRS)

    Gonzalez, W. D.; Dutra, S. L. G.; Pinto, O., Jr.

    1987-01-01

    Evidence for a localized middle atmospheric electrodynamic modification at low latitudes (southern Brazilian coast) of the South Atlantic Magnetic Anomaly (SAMA), in association with enhanced geomagnetic activity, are presented in a unified way combining recent observational efforts and related numerical studies. They involve a distortion effect in the fair weather electric field at balloon altitudes. This effect is attributed to a local intensification of energetic electron precipitation through a related middle atmospheric ionization enhancement and is elucidated by numeric simulation. From the electric field measurements and the numeric simulation, the intensification of precipitation is considered to occur in fairly narrow regions at the observed low L values (around L = 1.13) of the SAMA, with horizontal extensions of the order of a few hundred kilometers. A physical mechanism that could be responsible for this sort of intensification is suggested. Furthermore, a comparison of the phenomenon of middle atmospheric electrodynamic modification at the SAMA with a similar one at auroral latitudes, in response to enhanced solar and geomagnetic activity, is also given.

  9. Analysis of the Nuevo Leon magnetic anomaly and its possible relation to the Cerro Prieto magmatic-hydrothermal system

    SciTech Connect

    Goldstein, N.E.; Wilt, M.J.; Corrigan, D.J.

    1982-10-01

    The broad dipolar magnetic anomaly whose positive peak is centered near Ejido Nuevo Leon, some 5 km east of the Cerro Prieto I Power Plant, has long been suspected to have a genetic relationship to the thermal source of the Cerro Prieto geothermal system. This suspicion was reinforced after several deep geothermal wells, drilled to depths of 3 to 3.5 km over the anomaly, intersected an apparent dike-sill complex consisting mainly of diabase but with minor rhyodacite. A detailed fit of the observed magnetic field to a computer model indicates that the source may be approximated by a tabular block 4 by 6 km in area, 3.7 km in depth, 2.3 km thick, and dipping slightly to the north. Mafic dike chips from one well, NL-1, were analyzed by means of electron microprobe analyses which showed tham to contain a titanomagnetite that is paramagnetic at in-situ temperature conditions. As the dike mineralogy does not account for the magnetic anomaly, the magnetic source is believed to be a deeper, magnetite-rich assemblage of peridotite-gabbro plutons. the suite of igneous rocks was probably passively emplaced at a shallow depth in response to crustal extension and thinning brought on by strike-slip faulting. The bottom of the magnetic source body, at an estimated depth of 6 km, is presumed to be at or near that of the Curie isotherm (575/sup 0/C) for magnetite, the principal ferromagnetic mineral in peridotitic-gabbroic rocks. The geological model derived from the magnetic study is generally supported by other geophysical data. In particular, earthquake data suggest dike injection is occurring at depths of 6 to 11 km in an area beneath the magnetic source. Thus, it is possible that heat for the geothermal field is being maintained by continuing crustal extension and magmatic activity.

  10. Analysis of the Nuevo Leon Magnetic Anomaly and its possible relation to the Cerro Prieto magmatic-hydrothermal system

    SciTech Connect

    Goldstein, N.E.; Corrigan, D.J.; Wilt, M.J.

    1984-01-01

    The broad dipolar magnetic anomaly whose positive peak is centered near Ejido Nuevo Leon, some 5 km east of the Cerro Prieto I power plant, has long been suspected to have a genetic relationship to the thermal source of the Cerro Prieto geothermal system. This suspicion was reinforced after several deep geothermal wells, drilled to depths of 3-3.5 km over the anomaly, intersected an apparent dike-sill complex consisting mainly of diabase but with minor rhyodacite. A detailed fit of the observed magnetic field to a computer model indicates that the source may be approximated by a tabular block 4 x 6 km in area, 3.7 km in depth, 2.3 km thick, and dipping slightly to the north. Mafic dike chips from one well, NL-1, were analysed by means of electron microprobe analyses which showed them to contain a titanomagnetite that is paramagnetic at in situ temperature conditions. As the dike mineralogy does not account for the magnetic anomaly, the magnetic source is believed to be a deeper, magnetite-rich assemblage of peridotite-gabbro plutons. The suite of igneous rocks was probably emplaced at a shallow depth in response to crustal extension and thinning brought on by en echelon strike-slip faulting. The bottom of the magnetic source body, at an estimated depth of 6 km, is presumed to be at or near that of the Curie isotherm (575/sup 0/C) for magnetite, the principal ferromagnetic mineral in peridotiticgabbroic rocks. The geological model derived from the magnetic study is generally supported by other geophysical data. In particular, earthquake data suggest dike injection is occurring at depths of 6-11 km in an area beneath the magnetic source. Thus, it is possible that heat for the geothermal field is being maintained by continuing crustal extension and magmatic activity.

  11. Regional gravity and magnetic anomalies related to a Proterozoic carbonatite terrane in the eastern Mojave Desert, California

    NASA Astrophysics Data System (ADS)

    Denton, K. M.; Ponce, D. A.; Miller, D. M.; Jernigan, C. T.

    2014-12-01

    One of the world's largest rare earth element carbonatite deposits is located at Mountain Pass in the eastern Mojave Desert, California. The 1.4 Ga carbonatite deposit is hosted by and intruded into 1.7 Ga gneiss and schist that occurs in a narrow north-northwest trending belt along the eastern parts of Clark Mountain Range, Mescal Range, and Ivanpah Mountains. The carbonatite is associated with an ultrapotassic intrusive suite that ranges from shonkinite through syenite and granite. Regional geophysical data reveal that the eastern Mojave carbonatite terrane occurs along the northeast edge of a prominent magnetic high and the western margin of a gravity high along the eastern Clark Mountain Range. To improve our understanding of the geophysical and structural framework of the eastern Mojave carbonatite terrane, we collected over 1900 gravity stations and over 600 physical rock property samples to augment existing geophysical data. Carbonatite intrusions typically have distinct gravity, magnetic, and radiometric signatures because these deposits are relatively dense, contain magnetite, and are enriched in thorium or uranium. However, our results show that the carbonatite is essentially nonmagnetic with an average susceptibility of 0.18 x 10-3 SI (n=31) and the associated ultrapotassic intrusive suite is very weakly magnetic with an average susceptibility of 2.0 x 10-3 SI (n=36). Although the carbonatite body is nonmagnetic, it occurs along a steep gradient of a prominent aeromagnetic anomaly. This anomaly may reflect moderately magnetic mafic intrusive rocks at depth. East of the ultrapotassic intrusive rocks, a prominent north trending magnetic anomaly occurs in the central part of Ivanpah Valley. Based on geologic mapping in the Ivanpah Mountains, this magnetic anomaly may reflect Paleoproterozoic mafic intrusive rocks related to the 1.7 Ga Ivanpah Orogeny. Physical property measurements indicate that exposed amphibolite along the eastern Ivanpah Mountains are

  12. Temporal High-Resolution Computed Tomography and Magnetic Resonance Imaging of Congenital Inner Ear Anomalies in Children.

    PubMed

    Palabiyik, Figen Bakirtas; Hacikurt, Kadir

    2016-10-01

    Imaging plays an important role in determining indications of cochlear implantation and choosing candidates for the procedure in children. Temporal high-resolution computed tomography (HRCT) and magnetic resonance imaging (MRI) can display precisely the complex anatomic structure of inner ear. Although HRCT permits detailed imaging of bony structures, MRI gives valuable information about membranous labyrinth, internal acoustic canal, and vestibulocochlear nerve. Magnetic resonance imaging examination of the brain should be performed at the same time to evaluate any coexistent brain parenchymal abnormality. These imaging modalities are complementary methods in evaluating congenital inner ear anomalies. The aim of this pictorial essay is to reviewing temporal HRCT and MRI findings of congenital inner ear anomalies.

  13. Spreading of the ocean floor: new evidence.

    PubMed

    Vine, F J

    1966-12-16

    It is suggested that the entire history of the ocean basins, in terms of oceanfloor spreading,is contained frozen in the oceanic crust. Variations in the intensity and polarity of Earth's magnetic field are considered to be recorded in the remanent magnetism of the igneous rocks as they solidified and cooled through the Curie temperature at the crest of an oceanic ridge, and subsequently spread away from it at a steady rate. The hypothesis is supported by the extreme linearity and continuity of oceanic magnetic anomalies and their symmetry about the axes of ridges. If the proposed reversal time scale for the last 4 million years is combined with the model, computed anomaly profiles show remarkably good agreement with those observed, and one can deduce rates of spreading for all active parts of the midoceanic ridge system for which magnetic profilesor surveys are available. The rates obtained are in exact agreement with those needed to account for continental drift. An exceptionally high rate of spreading (approximately 4.5 cm/year) in the South Pacific enables one to deduce by extrapolation considerable details of the reversal time scale back to 11.5 million years ago. Again, this scale can be applied to other parts of the ridge system. Thus one isled to the suggestion that the crest of the East Pacific Rise in the northeast Pacific has been overridden and modified by the westward drift of North America, with the production of the anomalous width and unique features of the American cordillera in the western United States. The oceanicmagnetic anomalies also indicate that there was a change in derection of crustal spreading in this region during Pliocene time from eastwest to southeast-northwest. A profile from the crest to the boundary of the East Pacific Rise, and the difference between axial-zone and flank anomalies over ridges, suggest increase in the frequency of reversal of Earth's magnetic field, together, possibly, with decrease in its intensity

  14. Magnetic resonance imaging of retropharyngeal lymph node metastasis in nasopharyngeal carcinoma: Patterns of spread

    SciTech Connect

    Liu Lizhi; Zhang Guoyi; Xie Chuangmiao; Liu Xuewen; Cui Chunyan; Li Li . E-mail: lililixj@hotmail.com

    2006-11-01

    Purpose: To investigate the incidence, distribution, and spread pattern of retropharyngeal lymph node (RLN) involvement in patients with nasopharyngeal carcinoma (NPC) by using magnetic resonance imaging (MRI). Methods and Materials: The MR images of 275 patients with newly diagnosed NPC were reviewed retrospectively. Nodes were classified as metastatic based on size criteria, the presence of nodal necrosis, and extracapsular spread. Results: Retropharyngeal lymph node involvement was detected in 175 (63.6%) patients. Metastatic RLNs were seen at the following levels: occipital bone, 24 (9.6%) nodes; C1, 157 (62.5%) nodes; C1/2, 40 (15.9%) nodes; C2, 27 (10.8%) nodes; C2/3, 1 (0.4%) node; and C3, 2 (0.8%) nodes. The incidence of RLN involvement was equal to the incidence of cervical lymph node involvement (81.4% vs. 81.4%) in 215 patients with nodal metastases. A significantly higher incidence of metastatic RLNs was observed in the presence of oropharynx, prestyloid parapharyngeal space, post-styloid parapharyngeal space, longus colli muscle, medial pterygoid muscle, levator muscle of velum palatini, tensor muscle of velum palatini, Level II node, Level III node, and Level V node involvement. A significantly lower incidence of metastatic RLNs was found in T1, N0, and Stage I disease. Conversely, no significant difference in the incidence of metastatic RLNs was observed between T1, 2, and, 3; N2 and N3; or Stage II, III, and IV disease. Conclusions: There is an orderly decrease in the incidence of metastatic lateral RLNs from the C1 to C3 level. Metastatic RLNs associate well with involvement of certain structures in early stage primary tumors and lymph node metastases of the upper jugular chain (Level II, Level III nodes) and the posterior triangle (Level V nodes). Both RLNs and cervical Level II nodes appear to be the first-echelon nodes in NPC.

  15. Curie point depth in the SW Caribbean using the radially averaged spectra of magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Salazar, Juan M.; Vargas, Carlos A.; Leon, Hermann

    2017-01-01

    We have estimated the Curie Point Depth (CPD) using the average radial power spectrum in a tectonically complex area located in the SW Caribbean basin. Data analyzed came from the World Digital Magnetic Anomaly Map, and three methods have been used to compare results and evaluate uncertainties: Centroid, Spectral Peak, and Forward Modeling. Results show a match along the three methods, suggesting that the CPD values in the area ranging between 6 km and 50 km. The results share the following characteristics: A) High values (> 30 km) are in continental regions; B) There is a trend of maximum CPD values along the SW-NE direction, starting from the Central Cordillera in Colombia to the Maracaibo Lake in Venezuela; C) There is a maximum CPD at the Sierra Nevada de Santa Marta (Colombia) as well as between Costa Rica - Nicaragua and Nicaragua - Honduras borders. The lowest CPD values (< 20 km) are associated with the coastal regions and offshore. We also tested results by estimating the geothermal gradient and comparing measured observations of the study area. Our results suggest at least five thermal terrains in the SW Caribbean Basin: A) The area that is comprising the Venezuela Basin, the Beata Ridge and the Colombia Basin up to longitude parallel to the Providencia Throat. B) The area that includes zones to the north of the Cocos Ridge and Panam Basin up to the trench. C) The orogenic region of the northern Andes and including areas of the Santa Marta Massif. D) The continental sector that encompasses Nicaragua, northern Costa Rica and eastern of Honduras. E) Corresponds to areas of the northern Venezuela and Colombia, NW of Colombia, the Panamanian territory and the transition zones between the Upper and Lower Nicaragua Rise.

  16. The effect of remnant magnetization in the Eastern Galicia Magnetic Anomaly: constraints on the source of the remanence and implications for the geological model

    NASA Astrophysics Data System (ADS)

    Ayarza, P.; Martínez Catalán, J. R.; Alvarez Lobato, F.; Villalaín, J. J.; Reguilón, R.

    2009-04-01

    The Eastern Galicia Magnetic Anomaly (EGMA) spans over an area of ~10000 km2 and with a maximum of 190 nT, is one of the highest amplitude magnetic anomalies of the Iberian Peninsula. From a geological point of view, it occupies the centre of the Lugo-Sanabria Gneiss Dome, an antiformal structure developed during the Late Carboniferous extension that affected the Variscan fold and thrust belt of NW Iberia. The EGMA reaches its maximum values along the Viveiro Fault, a normal fault located at the western boundary of the Lugo-Sanabria Dome, coinciding with a relative low of the Bouguer gravity anomaly. Magnetite-bearing migmatites and inhomogeneous granites outcropping in the northern part of the gneiss dome seem to be the main source of the anomaly. Magnetite grains are heterogeneously distributed, can reach up to 1 cm, and may appear also in the metamorphic country rocks, paragneisses and quartzites, adjacent to the granitoids. These findings led Ayarza and Martínez Catalán (2007) to conclude that the EGMA is caused by the products of partial melting formed during the late Variscan extensional collapse. 2D gravity and magnetic modelling allowed them to interpret the EGMA as the magnetic response of a N-S to NW-SE elongated body, 200 km long and roughly 90 km wide, lens-shaped in cross section and up to 10 km thick, formed by migmatites, inhomogeneous granites and their country rocks, and located at depths between 0 and 20 km. The size of the magnetite grains suggested that magnetic remanence was unlikely and modelling was carried out assuming that the magnetic response of this lens-shaped body was mostly induced by the present-day magnetic field. However, recent NRM and demagnetization studies on a variety of samples have shown that remanence is common and even might get to be important, with Königsberger ratios (Qn) normally below 0.5 but exceptionally exceeding 1. Remanence is mostly produced by high coercitivity minerals (>120 mT) and seem to be post

  17. Spatial association analysis between hydrocarbon fields and sedimentary residual magnetic anomalies using Weights of Evidence: An example from the Triassic Province of Algeria

    NASA Astrophysics Data System (ADS)

    Allek, Karim; Boubaya, Djamel; Bouguern, Abderrahmane; Hamoudi, Mohamed

    2016-12-01

    The presence of near-surface magnetic anomalies over oil and gas accumulations and their contribution to exploration remain somewhat controversial despite encouraging results and an improved understanding of genetic links between hydrocarbon seepage-induced alterations and near-surface magnetic minerals. This controversy is likely to remain since the cause of shallow-sourced sedimentary magnetic anomalies may well be microseepage related, but could also result from other sources such as cultural features and detrital magnetite. The definite way of discriminating between them remains a challenge. In this paper we examine means to deal with this particular purpose using a Bayesian technique known as 'Weights-of-Evidence'. The technique is implemented in GIS to explore spatial associations between known hydrocarbon fields within the central Triassic province of Algeria and sedimentary residual magnetic anomalies. We use the results to show possible application of the method to the recognition of some characteristics (amplitude and width) of anomalies assumed to be induced by hydrocarbon microseepages. Our results reveal strong spatial association with certain typical class of anomalies, confirming therefore hypothesis that hydrocarbon microseepages may result in detectable magnetic anomalies. It is possible to use the anomalies occurring outside the known gas and oil fields to make informed decisions in the selection of new targets for more detailed hydrocarbon exploration.

  18. Interpretation of the Total Magnetic Field Anomalies Measured by the CHAMP Satellite Over a Part of Europe and the Pannonian Basin

    NASA Technical Reports Server (NTRS)

    Kis, K. I.; Taylor, Patrick T.; Wittmann, G.; Toronyi, B.; Puszta, S.

    2012-01-01

    In this study we interpret the magnetic anomalies at satellite altitude over a part of Europe and the Pannonian Basin. These anomalies are derived from the total magnetic measurements from the CHAMP satellite. The anomalies reduced to an elevation of 324 km. An inversion method is used to interpret the total magnetic anomalies over the Pannonian Basin. A three dimensional triangular model is used in the inversion. Two parameter distributions: Laplacian and Gaussian are investigated. The regularized inversion is numerically calculated with the Simplex and Simulated Annealing methods and the anomalous source is located in the upper crust. A probable source of the magnetization is due to the exsolution of the hematite-ilmenite minerals.

  19. Airborne gamma-ray and magnetic anomaly signatures of serpentinite in relation to soil geochemistry, northern California

    USGS Publications Warehouse

    McCafferty, A.E.; Van Gosen, B. S.

    2009-01-01

    Serpentinized ultramafic rocks and associated soils in northern California are characterized by high concentrations of Cr and Ni, low levels of radioelements (K, Th, and U) and high amounts of ferrimagnetic minerals (primarily magnetite). Geophysical attributes over ultramafic rocks, which include airborne gamma-ray and magnetic anomaly data, are quantified and provide indirect measurements on the relative abundance of radioelements and magnetic minerals, respectively. Attributes are defined through a statistical modeling approach and the results are portrayed as probabilities in chart and map form. Two predictive models are presented, including one derived from the aeromagnetic anomaly data and one from a combination of the airborne K, Th and U gamma-ray data. Both models distinguish preferential values within the aerogeophysical data that coincide with mapped and potentially unmapped ultramafic rocks. The magnetic predictive model shows positive probabilities associated with magnetic anomaly highs and, to a lesser degree, anomaly lows, which accurately locate many known ultramafic outcrops, but more interestingly, locate potentially unmapped ultramafic rocks, possible extensions of ultramafic bodies that dip into the shallow subsurface, as well as prospective buried ultramafic rocks. The airborne radiometric model shows positive probabilities in association with anomalously low gamma radiation measurements over ultramafic rock, which is similar to that produced by gabbro, metavolcanic rock, and water bodies. All of these features share the characteristic of being depleted in K, Th and U. Gabbro is the only rock type in the study area that shares similar magnetic properties with the ultramafic rock. The aerogeophysical model results are compared to the distribution of ultramafic outcrops and to Cr, Ni, K, Th and U concentrations and magnetic susceptibility measurements from soil samples. Analysis of the soil data indicates high positive correlation between

  20. Magnetic induction tomography: evaluation of the point spread function and analysis of resolution and image distortion.

    PubMed

    Merwa, Robert; Scharfetter, Hermann

    2007-07-01

    Magnetic induction tomography (MIT) is a low-resolution imaging modality used for reconstructing the changes of the passive electrical properties in a target object. For an imaging system, it is very important to give forecasts about the image quality. Both the maximum resolution and the correctness of the location of the inhomogeneities are of major interest. Furthermore, the smallest object which can be detected for a certain noise level is a criterion for the diagnostic value of an image. The properties of an MIT image are dependent on the position inside the object, the conductivity distribution and of course on the location and the number of excitation coils and receiving coils. Quantitative statements cannot be made in general but it is feasible to predict the image quality for a selected problem. For electrical impedance tomography (EIT), the theoretical limits of image quality have been studied carefully and a comprehensive analysis for MIT is necessary. Thus, a simplified analysis on resolution, dimensions and location of an inhomogeneity was carried out by means of an evaluation of the point spread function (PSF). In analogy to EIT the PSF depends strongly on the location, showing the broadest distribution in the centre of the object. Increasing the amount of regularization according to increasing measurement noise, the PSF broadens and its centre is shifted towards the borders of the object. The resolution is indirectly proportional to the width of the PSF and increases when moving from the centre towards the border of the object and decreases with increasing noise.

  1. Anomalies in the applied magnetic fields in DIII-D and their implications for the understanding of stability experiments

    SciTech Connect

    Luxon, J. L.; Schaffer, M. J.; Jackson, G. L.; Leuer, J. A.; Nagy, A.; Scoville, J. T.; Strait, E. J.

    2003-12-01

    Small non-axisymmetric magnetic fields are known to cause serious loss of stability in tokamaks leading to loss of confinement and abrupt termination of plasma current (disruptions). The best known examples are the locked mode and the resistive wall mode. Understanding of the underlying field anomalies (departures in the hardware-related fields from ideal toroidal and poloidal fields on a single axis) and the interaction of the plasma with them is crucial to tokamak development. Results of both locked mode experiments and resistive wall mode experiments done in DIII-D tokamak plasmas have been interpreted to indicate the presence of a significant anomalous field. New measurements of the magnetic field anomalies of the hardware systems have been made on DIII-D. The measured field anomalies due to the plasma shaping coils in DIII-D are smaller than previously reported. Additional evaluations of systematic errors have been made. New measurements of the anomalous fields of the ohmic heating and toroidal coils have been added. Such detailed in situ measurements of the fields of a tokamak are unique. The anomalous fields from all of the coils are one third of the values indicated from the stability experiments. These results indicate limitations in the understanding of the interaction of the plasma with the external field. They indicate that it may not be possible to deduce the anomalous fields in a tokamak from plasma experiments and that we may not have the basis needed to project the error field requirements of future tokamaks.

  2. Analysis of the nature of excessive cosmic radiation in the area of the Brazilian magnetic anomaly at altitudes 250-500km, from Kosmos-225 satellite data

    NASA Technical Reports Server (NTRS)

    Raychenko, L. V.

    1974-01-01

    Results are presented from a study of the region of anomalous cosmic radiation in the area of the Brazilian magnetic anomaly at the altitudes 250-500 km, using data measurements taken on the Kosmos-225 satellite (14-29 June 1968). The existence of a stable intensity anomaly discovered in the experiments on the second and third Soviet spacecraft-satellites is confirmed. The total vector of the geomagnetic field at different altitudes was compared with isoline maps. An altitude profile of the South Atlantic anomaly of radiation intensity was obtained, using data from the same instrument. The nature of the anomalies in cosmic radiation intensity over the regions of negative magnetic anomalies is discussed.

  3. Anomalies in Giant Quantum Attenuation of Sound Waves in Bismuth at High Magnetic Fields. I. Temperature and Frequency Dependences

    NASA Astrophysics Data System (ADS)

    Mase, Shoichi; Fukami, Takeshi; Mori, Masatoshi; Akinaga, Masahiro; Yamaguchi, Toshinobu; Shiraishi, Naotaka

    1980-04-01

    A reinvestigation has been made of an anomaly in the temperature dependence of the ultrasonic attenuation in bismuth, which is observed when an electron Landau level and a hole Landau level approach simultaneously to the Fermi level at high magnetic fields and at low temperatures. It has been found that in the most anomalous case the anomaly in the temperature dependence accompanies an anomalous frequency dependence and these are quite sensitive to physical imperfections in bismuth. On the basis if Kuramoto’s theory of sound attenuation which is taking account of the short-range electron-hole correlation, the experimental results are analyzed, and it is suggested that one more additional term is required to explain the present anomalous data.

  4. Elastic, Magnetic, and Electrical Properties of Exhumed Fault Mylonites: Exploring the Geophysical Anomalies Adjacent to the Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Kluge, K. E.; Toy, V.; Ohneiser, C.; Adam, L.

    2015-12-01

    Geophysical measurements made during the South Island Geophysical Transect (SIGHT) and the Southern Alps Passive Seismic Experiment (SAPSE) identified a region of anomalously low elastic wave velocity at depth adjacent to New Zealand's Alpine Fault. In the same area there is an anomaly of increased electrical conductivity, identified in magnetotelluric surveys across the Southern Alps. These anomalies have been assumed to relate to the presence of fluids. In particular, enhanced resistivity may result from interconnected fluid or graphite on the grain scale within ductilely shearing rock. These fluids were released from the lower crust as it metamorphosed during burial into the base of the thickened crust beneath New Zealand's Southern Alps. Graphite, observed in the Alpine Schist and exhumed hanging wall mylonites, is hypothesized to be remobilized by and precipitated from these fluids in trace amounts to contribute to the high conductivity. Pore decorated grain boundaries, which impart dynamic permeability during shear, could allow upward migration of over pressured fluids and potentially graphite, until they reach an array of near vertical backshears adjacent to the Alpine Fault. Outcrops along the hanging wall of the Alpine Fault expose rock exhumed from subsurface regions. To identify the causes of the large scale geophysical anomalies, we investigated static rock elastic, magnetic and electrical properties of the exhumed rocks on a hand sample scale. We will present measurements of phase anisotropy with respect to foliation to verify the anomaly is present at hand sample scale. We consider how geophysical measurements vary with mineralogical content and distribution, determined by both XRD derived bulk mineralogy and thin section observations. We aim to identify the microscale source of the geophysical anomaly and determine the relative contribution of different mineral phases.

  5. Analysis of EM dataset with several sensor configurations obtained by the loop-loop EM survey on magnetic anomalies

    NASA Astrophysics Data System (ADS)

    CHOI, J.; Yi, M. J.; Sasaki, Y.; Son, J.; Nam, M. J.

    2015-12-01

    Most of mineral mines in Korea are located in rugged mountain area embedding small-scale anomalies. Loop-loop EM survey system can be a better choice for exploring those mines because no ground contact is required and portable loops are freely positioned. Survey design is very important for detecting small amount of mineral deposits efficiently and spatial limits of survey lines should be considered. Along a same survey line, surveys with different separations between a transmitter and a receiver are applicable. EM responses are calculated in a layered-earth model embedding magnetic anomalies and analyses considering electric conductivity and magnetic permeability are made for the loop-loop EM survey data. Combining EM dataset with multi-frequency and multi-separation slightly enhanced a reconstructed image. Loop-loop EM survey using PROMOIS system was conducted on a small magnetite mine. Inversion with and without considering magnetic permeability was conducted for EM data with multi-frequency and multi-separation between a transmitter and a receiver.

  6. Middle proterozoic tectonic activity in west Texas and eastern New Mexico and analysis of gravity and magnetic anomalies

    SciTech Connect

    Adams, D.C.; Keller, G.R. )

    1994-03-01

    The Precambrian history of west Texas and eastern New Mexico is complex, consisting of four events: Early Proterozoic orogenic activity (16309-1800 Ma), formation of the western granite-rhyolite province (WGRP) (1340-1410 Ma), Grenville age tectonics (1116-1232 Ma), and middle Proterozoic extension possibly related to mid-continent rifting (1086-1109 Ma). Pre-Grenville tectonics, Grenville tectonics, and mid-continent rifting are represented in this area by the Abilene gravity minimum (AGM) and bimodal igneous rocks, which are probably younger. We have used gravity modeling and the comparison of gravity and magnetic anomalies with rock types reported from wells penetrating Precambrian basement to study the AGM and middle Proterozoic extension in this area. The AGM is an east-northeast-trending, 600 km long, gravity low, which extends from the Texas-Oklahoma border through the central basin platform (CBP) to the Delaware basin. This feature appears to predate formation of the mafic body in the CBP (1163 Ma) and is most likely related to Pre-Grenville tectonics, possibly representing a continental margin arc batholith. Evidence of middle Proterozoic extension is found in the form of igneous bodies in the CBP, the Van Horn uplift, the Franklin Mountains, and the Sacramento Mountains. Analysis of gravity and magnetic anomalies shows that paired gravity and magnetic highs are related to mafic intrusions in the upper crust. Mapping of middle Proterozoic igneous rocks and the paired anomalies outlines a 530 km diameter area of distributed east-west-oriented extension. The Debaca-Swisher terrain of shallow marine and clastic sedimentary rocks is age correlative with middle Proterozoic extension. These rocks may represent the lithology of possible Proterozoic exploration targets. Proterozoic structures were reactivated during the Paleozoic, affecting both the structure and deposition in the Permian basin.

  7. High-resolution near-bottom vector magnetic anomalies over Raven Hydrothermal Field, Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Tivey, Maurice A.; Johnson, H. Paul; Salmi, Marie S.; Hutnak, Michael

    2014-10-01

    High-resolution, near-bottom vector magnetic data were collected by remotely operated vehicle Jason over the Raven hydrothermal vent field (47°57.3'N 129°5.75'W) located north of Main Endeavour vent field on the Endeavour segment of the Juan de Fuca Ridge. The survey was part of a comprehensive heat flow study of the Raven site using innovative thermal blanket technology to map the heat flux and crustal fluid pathways around a solitary hydrothermal vent field. Raven hydrothermal activity is presently located along the western axial valley wall, while additional inactive hydrothermal deposits are found to the NW on the upper rift valley wall. Magnetic inversion results show discrete areas of reduced magnetization associated with both active and inactive hydrothermal vent deposits that also show high conductive heat flow. Higher spatial variability in the heat flow patterns compared to the magnetization is consistent with the heat flow reflecting the currently active but ephemeral thermal environment of fluid flow, while crustal magnetization is representative of the static time-averaged effect of hydrothermal alteration. A general NW to SE trend in reduced magnetization across the Raven area correlates closely with the distribution of hydrothermal deposits and heat flux patterns and suggests that the fluid circulation system at depth is likely controlled by local crustal structure and magma chamber geometry. Magnetic gradient tensor components computed from vector magnetic data improve the resolution of the magnetic anomaly source and indicate that the hydrothermally altered zone directly beneath the Raven site is approximately 15 × 106 m3 in volume.

  8. Pacific-North American plate motion from very long baseline interferometry compared with motion inferred from magnetic anomalies, transform faults, and earthquake slip vectors

    NASA Technical Reports Server (NTRS)

    Argus, Donald F.; Gordon, Richard G.

    1990-01-01

    Geodetic VLBI measurements were used to test whether the Pacific-North American plate velocity averaged over several years of direct observation (1984-1987) equals that averaged over millions of years. It was also tested whether this velocity parallels the San Andreas fault, transform faults and earthquake slip vectors in the Gulf of California, and earthquake slip vectors along the Queen Charlotte fault, along the Alaskan peninsula, and along the Kamchatkan peninsula. The VLBI data provide an estimate of the direction of plate motion that is independent of estimates from fault azimuths and earthquake slip vectors. The Euler vector determined from VLBI was found to be nearly identical to the Euler vector of plate motion model NUVEL-1, which is based on the trends of transform faults, earthquake slip vectors, and spreading rates from marine magnetic anomalies that average motion since 3 Ma. The velocity between the Pacific and North American plates averaged over the past several years equals or nearly equals its velocity averaged over the past several million years, the difference along their boundary nowhere exceeding 4 + or - 7 mm/yr.

  9. Petrologic and geophysical study of the source of long wavelength crustal magnetic anomalies

    NASA Technical Reports Server (NTRS)

    Marsch, B.; Schlinger, C. M.

    1983-01-01

    The magnetic mineralogy and magnetic signature of banded ion formations, diagenetic (unmetamorphosed) and low grade banded iron formations, high-grade mineralogy, and phase equilibria of magnetite inorogenic magmers are discussed.

  10. Three-dimensional full-kinetic simulation of the solar wind interaction with a vertical dipolar lunar magnetic anomaly

    NASA Astrophysics Data System (ADS)

    Deca, Jan; Divin, Andrey; Wang, Xu; Lembège, Bertrand; Markidis, Stefano; Horányi, Mihály; Lapenta, Giovanni

    2016-05-01

    A detailed understanding of the solar wind interaction with lunar magnetic anomalies (LMAs) is essential to identify its implications for lunar exploration and to enhance our physical understanding of the particle dynamics in a magnetized plasma. We present the first three-dimensional full-kinetic electromagnetic simulation case study of the solar wind interaction with a vertical dipole, resembling a medium-size LMA. In contrast to a horizontal dipole, we show that a vertical dipole twists its field lines and cannot form a minimagnetosphere. Instead, it creates a ring-shaped weathering pattern and reflects up to 21% (four times more as compared to the horizontal case) of the incoming solar wind ions electrostatically through the normal electric field formed above the electron shielding region surrounding the cusp. This work delivers a vital piece to fully comprehend and interpret lunar observations, as we find the amount of reflected ions to be a tracer for the underlying field structure.

  11. Additions to Magnetic Trackline Archive For Improvements to Earth Magnetic Anomaly Grid (EMAG2) and Improvements to Data Dissemination at NGDC

    NASA Astrophysics Data System (ADS)

    Meyer, B.; Jencks, J.; Barckhausen, U.; Ishihara, T.; Campagnoli, J.

    2014-12-01

    The National Geophysical Data Center (NGDC) is the primary archive of marine geophysical data worldwide. However, it has been challenging for scientist to discover and access data due to variable data formats, non-digital data holdings, and transitioning data discovery portals. In 2014, NGDC made a concerted effort to identify, ingest, and archive all publicly available magnetic trackline data for access via a new Trackline Geophysical Data web-based interface. Non-digital data were digitized and added to the Global Geophysical Database and are now available for download in a common MGD77 format. All ancillary and analog data are accessible via the same interface, without having to navigate through multiple directories or prompts. The result is over 16.5 million miles of magnetic trackline data are now available, both through NGDC's improved user interface and as a web service for incorporation into other portals. This allows the geoscience community unprecedented access to global geophysical magnetic trackline data from a secure long-term archive. The addition of 6.5 million miles of magnetic trackline data to the database, since the previous release of the Earth Magnetic Anomaly Grid (EMAG2), will give NGDC the ability to improve the model coverage, especially in areas of low coverage, such as around the Eltanin Fracture Zone in the South Pacific. This poster will focus on some key data additions and how they will help us validate the accuracy of the ocean age model/directional gridding algorithm and improve the Earth Magnetic Anomaly Grid going forward.

  12. Detailed bathymetry and magnetic anomaly inthe Central Ryukyu Arc, Japan: implications for a westward shift of the volcanic front after ~2.1 Ma

    NASA Astrophysics Data System (ADS)

    Sato, T.; Oda, H.; Ishizuka, O.; Arai, K.

    2014-12-01

    Detailed bathymetry and magnetic anomalies in the southern part of the Central Ryukyu Arc reveal recent volcanic structures in a southwestward extension of the active volcanic front of the Ryukyu Arc. A line of bathymetric highs running subparallel to this recent volcanic front was observed ~20 km to the east. A set of small, sharply defined magnetic anomalies extends southward from this line of bathymetric highs to the islands Kume-jima and Aguni-jima, suggesting the former existence of an ancient volcanic front. The ages of volcanic rocks from these islands indicate that magmatic activity along the ancient volcanic front continued until at least ~2.1 Ma. The presence of magnetic anomalies between the two volcanic fronts suggests that the volcanic front has moved gradually westward. This shift can be explained by the termination of asthenospheric upwelling and/or the rapid retreat of the Ryukyu Trench after its change in subduction direction.

  13. Detailed bathymetry and magnetic anomaly in the Central Ryukyu Arc, Japan: implications for a westward shift of the volcanic front after approximately 2.1 Ma

    NASA Astrophysics Data System (ADS)

    Sato, Taichi; Oda, Hirokuni; Ishizuka, Osamu; Arai, Kohsaku

    2014-12-01

    Detailed bathymetry and magnetic anomalies in the southern part of the Central Ryukyu Arc reveal recent volcanic structures in a southwestward extension of the active volcanic front of the Ryukyu Arc. A line of bathymetric highs running subparallel to this recent volcanic front was observed approximately 20 km to the east. A set of small, sharply defined magnetic anomalies extends southward from this line of bathymetric highs to the islands Kume-jima and Aguni-jima, suggesting the former existence of an ancient volcanic front. The ages of volcanic rocks from these islands indicate that magmatic activity along the ancient volcanic front continued until at least approximately 2.1 Ma. The presence of magnetic anomalies between the two volcanic fronts suggests that the volcanic front has moved gradually westward. This shift can be explained by the termination of asthenospheric upwelling and/or the rapid retreat of the Ryukyu Trench after its change in subduction direction.

  14. Phase equilibria at alkali-rich early proterozoic banded iron formation, Kursk magnetic anomaly, Russia

    NASA Astrophysics Data System (ADS)

    Sayko, K. A.; Gerasimov, V. Yu.; Poskryakova, M. V.

    2003-04-01

    Banded iron formation (BIF) rocks of Kursk Magnetic anomaly (KMA) are distinguished from well known Precambrian BIF by the alkali enrichment and aluminum depletion and as a total absence of the aluminum bearing minerals. From layered silicates the maximum saturated potassium phases seladonite and tetraferribiotite are of widespread occurrence instead stilpnomelane, minnesotaite and greenalite commonplace for low grade BIF. It has been widely distribution of the seladonite with the assemblage of tetraferribiotite, magnetite, hematite, and quartz distinguish ferruginous quartzites Mikhailovsk iron deposit (KMA) from well known Precambrian BIF of the ancient shields. From Fe-Mg silicates the aegirine, ribeckite and aluminum-less chlorite are present. The hematite and magnetite stability in the ferruginous quartzites assemblages suggest the high values of the oxygen fugacity near magnetite-hematite buffer. This is confirmed by somewhat increasing XMg values for seladonite, tetraferribiotite, chlorite, and ribeckite. The minerals producing with large amounts of ferric iron (seladonite, tetraferribiotite) in the ferruginous quartzites of Mikhailovsk iron deposit is caused by the oxygen fugacity high values. For example the ferrichamosite (Fe_5Fe3+(Fe3+Si_3)O10(OH)_8) is produced in place of the commonplace for the low-grade BIF greenalite (Fe_6Si_4O10(OH)_8). As a whole chlorites are a rarity in BIFs (Laird, 1989) through low rocks aluminum content and represent by chamosite (Gole, 1981), clinochlore and ripidolite (Miyano, Beukes, 1997). Chlorite in studied ferruginous quartzites has a uncommon aluminumless composition with high Fe3+ content and corresponds hypothetical end-member of chamosite - "ferrichamosite" and "ferriclinochlore" - "ferrichamosite" series (Burt, 1989). Uncommon aluminumless chlorite composition assumes that it appears during low-grade metamorphism and possible catagenesis: Mag + Hem + Qtz rightarrow H_2O rightarrow Fe-Chm + O_2 Sid + Qtz + Mag

  15. Investigations of medium wavelength magnetic anomalies in the Eastern Pacific using MAGSAT data

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A. (Principal Investigator)

    1982-01-01

    A paper which discusses a problem in representing the core magnetic field of the Earth using spherical harmonics was revised and accepted for publications. Page proofs of a second paper concerning off center dipole modelling of the Earth's magnetic field are presented.

  16. Magnetic resonance imaging of cerebral anomalies in subjects with resistance to thyroid hormone

    SciTech Connect

    Leonard, C.M.; Hauser, P.; Weintraub, B.D. |

    1995-06-19

    Resistance to thyroid hormone (RTH) is an autosomal dominant disease caused by mutations in the human thyroid receptor beta gene on chromosome 3. Individuals with RTH have an increased incidence of attention deficit hyperactivity disorder (ADHD). The purpose of this study was to search for developmental brain malformations associated with RTH. Forty-three subjects (20 affected males [AM], 23 affected females [AF]) with resistance to thyroid hormone and 32 unaffected first degree relatives (18 unaffected males [UM], 14 unaffected females [UF]) underwent MRI brain scans with a volumetric acquisition that provided 90 contiguous 2 mm thick sagittal images. Films of six contiguous images beginning at a standard sagittal position lateral to the insula were analyzed by an investigator who was blind with respect to subject characteristics. The presence of extra or missing gyri in the parietal bank of the Sylvian fissure (multimodal association cortex) and multiple Heschl`s transverse gyri (primary auditory cortex) were noted. There was a significantly increased frequency of anomalous Sylvian fissures in the left hemisphere in males with RTH (AM: 70%; AF: 30%; UM: 28% UF: 28%). Also, there was an increased frequency of anomalous Sylvian fissures on the left combined with multiple Heschl`s gyri in either hemisphere in males with RTH (AM: 50%; AF: 9%; UM: 6%; UF: 0%). However, RTH subjects with anomalies did not have an increased frequency of ADHD as compared with RTH subjects with no anomalies. Abnormal thyroid hormone action in the male fetus early during brain development may be associated with grossly observable cerebral anomalies of the left hemisphere. The effects of mutations in the thyroid receptor beta gene provide a model system for studying the complex interaction of genetic and non-genetic factors on brain and behavioral development. 19 refs., 2 figs., 2 tabs.

  17. Transrectal ultrasound and magnetic resonance imaging measurement of extramural tumor spread in rectal cancer

    PubMed Central

    Rafaelsen, Søren R; Vagn-Hansen, Chris; Sørensen, Torben; Pløen, John; Jakobsen, Anders

    2012-01-01

    AIM: To evaluate the agreement between transrectal ultrasound (TRUS) and magnetic resonance imaging (MRI) in classification of ≥ T3 rectal tumors. METHODS: From January 2010 to January 2012, 86 consecutive patients with ≥ T3 tumors were included in this study. The mean age of the patients was 66.4 years (range: 26-91 years). The tumors were all ≥ T3 on TRUS. The sub-classification was defined by the penetration of the rectal wall: a: 0 to 1 mm; b: 1-5 mm; c: 6-15; d: > 15 mm. Early tumors as ab (≤ 5 mm) and advanced tumors as cd (> 5 mm). All patients underwent TRUS using a 6.5 MHz transrectal transducer. The MRI was performed with a 1.5 T Philips unit. The TRUS findings were blinded to the radiologist performing the interpretation of the MRI images and measuring the depth of extramural tumor spread. RESULTS: TRUS found 51 patients to have an early ≥ T3 tumors and 35 to have an advanced tumor, whereas MRI categorized 48 as early ≥ T3 tumors and 38 as advanced tumors. No patients with tumors classified as advanced by TRUS were found to be early on MRI. The kappa value in classifying early versus advanced T3 rectal tumors was 0.93 (95% CI: 0.85-1.00). We found a kappa value of 0.74 (95% CI: 0.63-0.86) for the total sub-classification between the two methods. The mean maximal tumor outgrowth measured by TRUS, 5.5 mm ± 5.63 mm and on MRI, 6.3 mm ± 6.18 mm, P = 0.004. In 19 of the 86 patients the following CT scan or surgery revealed distant metastases; of the 51 patients in the ultrasound ab group three (5.9%) had metastases, whereas 16 (45.7%) of 35 in the cd group harbored distant metastases, P = 0.00002. The odds ratio of having distant metastases in the ultrasound cd group compared to the ab group was 13.5 (95% CI: 3.5-51.6), P = 0.00002. The mean maximal ultrasound measured outgrowth was 4.3 mm (95% CI: 3.2-5.5 mm) in patients without distant metastases, while the mean maximal outgrowth was 9.5 mm (95% CI: 6.2-12.8 mm) in the patients with metastases

  18. Relationship between characteristics of gravity and magnetic anomalies and the earthquakes in the Longmenshan range and adjacent areas

    NASA Astrophysics Data System (ADS)

    Zhang, Jisheng; Gao, Rui; Zeng, Lingsen; Li, Qiusheng; Guan, Ye; He, Rizheng; Wang, Haiyan; Lu, Zhanwu

    2010-08-01

    , which corresponds to the location of the horizontal gradient belt of the residual gravity. But in the Guanxian-Beichuan segment in the northern Longmenshan fault zone, the push is oblique to the location of this gradient belt. Such a relationship could lead to nearly equal amounts of thrust and right-lateral slip along the Beichuan-Qingchuan segment, and in contrast to nearly pure thrust along the Guanxian-Beichuan segment. An unusually large negative magnetic anomaly occurs around Qingchuan-Wenchuan-Guanxian. The computed magnetic model shows that some crystalline complexes with reversal magnetization might exist in the crust, which might be related to extrusion of the metamorphic basement rocks in the lower to middle crust.

  19. Interpretation of Magnetic Anomalies in Salihli (Turkey) Geothermal Area Using 3-D Inversion and Edge Detection Techniques

    NASA Astrophysics Data System (ADS)

    Timur, Emre

    2016-04-01

    There are numerous geophysical methods used to investigate geothermal areas. The major purpose of this magnetic survey is to locate the boudaries of active hydrothermal system in the South of Gediz Graben in Salihli (Manisa/Turkey). The presence of the hydrothermal system had already been inferred from surface evidence of hydrothermal activity and drillings. Firstly, 3-D prismatic models were theoretically investigated and edge detection methods were utilized with an iterative inversion method to define the boundaries and the parameters of the structure. In the first step of the application, it was necessary to convert the total field anomaly into a pseudo-gravity anomaly map. Then the geometric boudaries of the structures were determined by applying a MATLAB based software with 3 different edge detection algorithms. The exact location of the structures were obtained by using these boundary coordinates as initial geometric parameters in the inversion process. In addition to these methods, reduction to pole and horizontal gradient methods were applied to the data to achieve more information about the location and shape of the possible reservoir. As a result, the edge detection methods were found to be successful, both in the field and as theoretical data sets for delineating the boundaries of the possible geothermal reservoir structure. The depth of the geothermal reservoir was determined as 2,4 km from 3-D inversion and 2,1 km from power spectrum methods.

  20. Earth's magnetic field anomalies that precede the M6+ global seismic activity

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2014-05-01

    In this work has been analyzed the Earth's magnetic field variations and the M6+ global seismic activity to verify if M6+ earthquakes are preceded by a change of the Earth's magnetic field. The data of Earth's magnetic field used to conduct the study of correlation are provided by the induction magnetometer of Radio Emissions Project's station (Lat: 41°41'4.27"N, Long: 12°38'33,60"E, Albano Laziale, Rome, Italy), equipped with a ELF receiver prototype (with a vertically aligned coil antenna) capable to detect the variations of the intensity of the Earth's magnetic field on Z magnetic component. The M6+ global seismic activity data are provided in real-time by USGS, INGV and CSEM. The sample of data used to conduct the study refers to the period between 1 January 2012 and 31 December 2012. The Earth's magnetic field variations data set has been marked with the times (time markers) of M6+ earthquakes occurred on a global scale and has been verified the existence of disturbances of the Earth's geomagnetic field in the time interval that preceded the M6+ global seismic activity. The correlation study showed that all M6+ earthquakes recorded on 2012 were preceded by an increase of the Earth's magnetic field, detected in the Z magnetic component. The authors measured the time lag elapsed between the maximum increment of the Earth's magnetic field recorded before an earthquake M6+ and the date and time at which this occurred, and has been verified that the minimum time lag recorded between the Earth's magnetic field increase and the earthquake M6+ has been 1 minute (9 October 2012, Balleny Islands, M6,4); while, the maximum time lag recorded has been 3600 minutes (26 June 2012, China, M6,3). The average time lag has been 629.47 minutes. In addition, the average time lag is deflected in relation to the magnitude increase. Key words: Seismic Geomagnetic Precursor (SGP), Interplanetary Seismic Precursor (ISP), Earth's magnetic field variations, earthquakes, prevision.

  1. 3D PIC Simulations of Collisionless Shocks at Lunar Magnetic Anomalies and Their Role in Forming Lunar Swirls

    NASA Astrophysics Data System (ADS)

    Bamford, R. A.; Alves, E. P.; Cruz, F.; Kellett, B. J.; Fonseca, R. A.; Silva, L. O.; Trines, R. M. G. M.; Halekas, J. S.; Kramer, G.; Harnett, E.; Cairns, R. A.; Bingham, R.

    2016-10-01

    Investigation of the lunar crustal magnetic anomalies offers a comprehensive long-term data set of observations of small-scale magnetic fields and their interaction with the solar wind. In this paper a review of the observations of lunar mini-magnetospheres is compared quantifiably with theoretical kinetic-scale plasma physics and 3D particle-in-cell simulations. The aim of this paper is to provide a complete picture of all the aspects of the phenomena and to show how the observations from all the different and international missions interrelate. The analysis shows that the simulations are consistent with the formation of miniature (smaller than the ion Larmor orbit) collisionless shocks and miniature magnetospheric cavities, which has not been demonstrated previously. The simulations reproduce the finesse and form of the differential proton patterns that are believed to be responsible for the creation of both the “lunar swirls” and “dark lanes.” Using a mature plasma physics code like OSIRIS allows us, for the first time, to make a side-by-side comparison between model and space observations. This is shown for all of the key plasma parameters observed to date by spacecraft, including the spectral imaging data of the lunar swirls. The analysis of miniature magnetic structures offers insight into multi-scale mechanisms and kinetic-scale aspects of planetary magnetospheres.

  2. The statistical mechanics of solar wind hydroxylation at the Moon, within lunar magnetic anomalies, and at Phobos

    NASA Astrophysics Data System (ADS)

    Farrell, W. M.; Hurley, D. M.; Esposito, V. J.; McLain, J. L.; Zimmerman, M. I.

    2017-01-01

    We present a new formalism to describe the outgassing of hydrogen initially implanted by the solar wind protons into exposed soils on airless bodies. The formalism applies a statistical mechanics approach similar to that applied recently to molecular adsorption onto activated surfaces. The key element enabling this formalism is the recognition that the interatomic potential between the implanted H and regolith-residing oxides is not of singular value but possess a distribution of trapped energy values at a given temperature, F(U,T). All subsequent derivations of the outward diffusion and H retention rely on the specific properties of this distribution. We find that solar wind hydrogen can be retained if there are sites in the implantation layer with activation energy values exceeding 0.5 eV. We especially examine the dependence of H retention applying characteristic energy values found previously for irradiated silica and mature lunar samples. We also apply the formalism to two cases that differ from the typical solar wind implantation at the Moon. First, we test for a case of implantation in magnetic anomaly regions where significantly lower-energy ions of solar wind origin are expected to be incident with the surface. In magnetic anomalies, H retention is found to be reduced due to the reduced ion flux and shallower depth of implantation. Second, we also apply the model to Phobos where the surface temperature range is not as extreme as the Moon. We find the H atom retention in this second case is higher than the lunar case due to the reduced thermal extremes (that reduces outgassing).

  3. Thermal and magnetic anomalies of α-iron: an exploration by extended x-ray absorption fine structure spectroscopy and synchrotron x-ray diffraction.

    PubMed

    Boccato, Silvia; Sanson, Andrea; Kantor, Innokenty; Mathon, Olivier; Dyadkin, Vadim; Chernyshov, Dmitry; Carnera, Alberto; Pascarelli, Sakura

    2016-09-07

    The local structure and dynamics of α-iron have been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray diffraction (XRD) in order to shed light on some thermal and magnetic anomalies observed in the last decades. The quantitative EXAFS analysis of the first two coordination shells reveals a peculiar local vibrational dynamics of α-iron: the second neighbor distance exhibits anharmonicity and vibrational anisotropy larger than the first neighbor distance. We search for possible distortions of the bcc structure to justify the unexplained magnetostriction anomalies of α-iron and provide a value for the maximum dislocation of the central Fe atom. No thermal anomalies have been detected from the current XRD data. On the contrary, an intriguing thermal anomaly at about 150 K, ascribed to a stiffening of the Fe-Fe bonds, was found by EXAFS.

  4. Thermal and magnetic anomalies of α-iron: an exploration by extended x-ray absorption fine structure spectroscopy and synchrotron x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Boccato, Silvia; Sanson, Andrea; Kantor, Innokenty; Mathon, Olivier; Dyadkin, Vadim; Chernyshov, Dmitry; Carnera, Alberto; Pascarelli, Sakura

    2016-09-01

    The local structure and dynamics of α-iron have been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray diffraction (XRD) in order to shed light on some thermal and magnetic anomalies observed in the last decades. The quantitative EXAFS analysis of the first two coordination shells reveals a peculiar local vibrational dynamics of α-iron: the second neighbor distance exhibits anharmonicity and vibrational anisotropy larger than the first neighbor distance. We search for possible distortions of the bcc structure to justify the unexplained magnetostriction anomalies of α-iron and provide a value for the maximum dislocation of the central Fe atom. No thermal anomalies have been detected from the current XRD data. On the contrary, an intriguing thermal anomaly at about 150 K, ascribed to a stiffening of the Fe-Fe bonds, was found by EXAFS.

  5. The Wallula fault and tectonic framework of south-central Washington, as interpreted from magnetic and gravity anomalies

    NASA Astrophysics Data System (ADS)

    Blakely, Richard J.; Sherrod, Brian L.; Weaver, Craig S.; Wells, Ray E.; Rohay, Alan C.

    2014-06-01

    The Yakima fold and thrust belt (YFTB) in central Washington has accommodated regional, mostly north-directed, deformation of the Cascadia backarc since prior to emplacement of Miocene flood basalt of the Columbia River Basalt Group (CRBG). The YFTB consists of two structural domains. Northern folds of the YFTB strike eastward and terminate at the western margin of a 20-mGal negative gravity anomaly, the Pasco gravity low, straddling the North American continental margin. Southern folds of the YFTB strike southeastward, form part of the Olympic-Wallowa lineament (OWL), and pass south of the Pasco gravity low as the Wallula fault zone. An upper crustal model based on gravity and magnetic anomalies suggests that the Pasco gravity low is caused in part by an 8-km-deep Tertiary basin, the Pasco sub-basin, abutting the continental margin and concealed beneath CRBG. The Pasco sub-basin is crossed by north-northwest-striking magnetic anomalies caused by dikes of the 8.5 Ma Ice Harbor Member of the CRBG. At their northern end, dikes connect with the eastern terminus of the Saddle Mountains thrust of the YFTB. At their southern end, dikes are disrupted by the Wallula fault zone. The episode of NE-SW extension that promoted Ice Harbor dike injection apparently involved strike-slip displacement on the Saddle Mountains and Wallula faults. The amount of lateral shear on the OWL impacts the level of seismic hazard in the Cascadia region. Ice Harbor dikes, as mapped with aeromagnetic data, are dextrally offset by the Wallula fault zone a total of 6.9 km. Assuming that dike offsets are tectonic in origin, the Wallula fault zone has experienced an average dextral shear of 0.8 mm/y since dike emplacement 8.5 Ma, consistent with right-lateral stream offsets observed at other locations along the OWL. Southeastward, the Wallula fault transfers strain to the north-striking Hite fault, the possible location of the M 5.7 Milton-Freewater earthquake in 1936.

  6. Spherical-earth gravity and magnetic anomaly modeling by Gauss-Legendre quadrature integration

    NASA Technical Reports Server (NTRS)

    Von Frese, R. R. B.; Hinze, W. J.; Braile, L. W.; Luca, A. J.

    1981-01-01

    Gauss-Legendre quadrature integration is used to calculate the anomalous potential of gravity and magnetic fields and their spatial derivatives on a spherical earth. The procedure involves representation of the anomalous source as a distribution of equivalent point gravity poles or point magnetic dipoles. The distribution of equivalent point sources is determined directly from the volume limits of the anomalous body. The variable limits of integration for an arbitrarily shaped body are obtained from interpolations performed on a set of body points which approximate the body's surface envelope. The versatility of the method is shown by its ability to treat physical property variations within the source volume as well as variable magnetic fields over the source and observation surface. Examples are provided which illustrate the capabilities of the technique, including a preliminary modeling of potential field signatures for the Mississippi embayment crustal structure at 450 km.

  7. Spherical-earth Gravity and Magnetic Anomaly Modeling by Gauss-legendre Quadrature Integration

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.; Luca, A. J. (Principal Investigator)

    1981-01-01

    The anomalous potential of gravity and magnetic fields and their spatial derivatives on a spherical Earth for an arbitrary body represented by an equivalent point source distribution of gravity poles or magnetic dipoles were calculated. The distribution of equivalent point sources was determined directly from the coordinate limits of the source volume. Variable integration limits for an arbitrarily shaped body are derived from interpolation of points which approximate the body's surface envelope. The versatility of the method is enhanced by the ability to treat physical property variations within the source volume and to consider variable magnetic fields over the source and observation surface. A number of examples verify and illustrate the capabilities of the technique, including preliminary modeling of potential field signatures for Mississippi embayment crustal structure at satellite elevations.

  8. True polar wander since 32 Ma B.P.: A paleomagnetic investigation of the skewness of magnetic anomaly 12r on the Pacific plate

    NASA Astrophysics Data System (ADS)

    Horner-Johnson, Benjamin C.; Gordon, Richard G.

    2010-09-01

    We test the fixed hot spot and fixed spin axis hypotheses through a paleomagnetic investigation of the skewness of crossings of magnetic anomaly 12r (32 Ma B.P.) between the Galapagos and Clarion fracture zones on the Pacific plate. We focus on this region for three reasons. First, numerical experiments show that these crossings, of all those available from the Pacific plate, should contain the most information about the location of the 32 Ma B.P. paleomagnetic pole for the Pacific plate. Second, many of the available crossings are from vector aeromagnetic profiles, which have superior signal-to-noise ratios. Third, the rate of seafloor spreading recorded in these crossings exceeds the threshold (half rate of 50 mm a-1) above which anomalous skewness is negligible. The new pole (83.5°N, 44.6°E) has compact 95% confidence limits (ellipse with major semiaxis length of 3.1° toward 84° clockwise from north and minor semiaxis length of 1.2°) and is not subject to the biases inherent in other methods for estimating Pacific plate paleomagnetic poles. The pole differs significantly by ≈5° from the pole predicted if the Pacific hot spots have been fixed with respect to the spin axis, thus demonstrating, for the first time from paleomagnetic data, that Pacific hot spots have moved relative to the spin axis since the formation of the elbow in the Hawaiian-Emperor chain. The pole is consistent, however, with previously published paleomagnetic poles in a reference frame fixed relative to Indo-Atlantic hot spots. Thus, the new results require no motion between Pacific and Indo-Atlantic hot spots since 32 Ma B.P. Instead, superimposed on whatever motion occurs between hot spots, as expected for true polar wander.

  9. An annular high-current electron beam with an energy spread in a coaxial magnetically insulated diode

    SciTech Connect

    Grishkov, A. A. Pegel, I. V.

    2013-11-15

    An elementary theory of an annular high-current electron beam in a uniform transport channel and a coaxial magnetically insulated diode is generalized to the case of counterpropagating electron beams with a spread over kinetic energies. Expressions for the sum of the absolute values of the forward and backward currents in a uniform transport channel and for the flux of the longitudinal component of the generalized momentum in a coaxial magnetically insulated diode as functions of the maximum electron kinetic energy are derived for different values of the relative width of the energy distribution function. It is shown that, in a diode with an expanding transport channel and a virtual cathode limiting the extracted current, counterpropagating particle flows are established between the cathode and the virtual cathode within a certain time interval after the beginning of electron emission. The accumulation of electrons in these flows is accompanied by an increase in their spread over kinetic energies and the simultaneous decrease in the maximum kinetic energy. The developed model agrees with the results of particle-in-cell simulations performed using the KARAT and OOPIC-Pro codes.

  10. Particle-In-Cell Simulations of the Solar Wind Interaction with Lunar Crustal Magnetic Anomalies: Magnetic Cusp Regions

    NASA Technical Reports Server (NTRS)

    Poppe, A. R.; Halekas, J. S.; Delory, G. T.; Farrell, W. M.

    2012-01-01

    As the solar wind is incident upon the lunar surface, it will occasionally encounter lunar crustal remanent magnetic fields. These magnetic fields are small-scale, highly non-dipolar, have strengths up to hundreds of nanotesla, and typically interact with the solar wind in a kinetic fashion. Simulations, theoretical analyses, and spacecraft observations have shown that crustal fields can reflect solar wind protons via a combination of magnetic and electrostatic reflection; however, analyses of surface properties have suggested that protons may still access the lunar surface in the cusp regions of crustal magnetic fields. In this first report from a planned series of studies, we use a 1 1/2-dimensional, electrostatic particle-in-cell code to model the self-consistent interaction between the solar wind, the cusp regions of lunar crustal remanent magnetic fields, and the lunar surface. We describe the self-consistent electrostatic environment within crustal cusp regions and discuss the implications of this work for the role that crustal fields may play regulating space weathering of the lunar surface via proton bombardment.

  11. An Exercise on Magnetic-Anomaly Profiles and the Geomagnetic Polar-Reversal Time Scale.

    ERIC Educational Resources Information Center

    Shea, James Herbert

    1988-01-01

    Develops an exercise in which students use magnetic-profile data gathered in the South Pacific to test the Vine-Matthews-Morley hypothesis. Uses the Eltanin 19N and 20N profiles. Relates the exercise to 20 current geology texts. (MVL)

  12. The Mackenzie River magnetic anomaly, Yukon and Northwest Territories, Canada-Evidence for Early Proterozoic magmatic arc crust at the edge of the North American craton

    USGS Publications Warehouse

    Pilkington, M.; Saltus, R.W.

    2009-01-01

    We characterize the nature of the source of the high-amplitude, long-wavelength, Mackenzie River magnetic anomaly (MRA), Yukon and Northwest Territories, Canada, based on magnetic field data collected at three different altitudes: 300??m, 3.5??km and 400??km. The MRA is the largest amplitude (13??nT) satellite magnetic anomaly over Canada. Within the extent of the MRA, source depth estimates (8-12??km) from Euler deconvolution of low-altitude aeromagnetic data show coincidence with basement depths interpreted from reflection seismic data. Inversion of high-altitude (3.5??km) aeromagnetic data produces an average magnetization of 2.5??A/m within a 15- to 35-km deep layer, a value typical of magmatic arc complexes. Early Proterozoic magmatic arc rocks have been sampled to the southeast of the MRA, within the Fort Simpson magnetic anomaly. The MRA is one of several broad-scale magnetic highs that occur along the inboard margin of the Cordillera in Canada and Alaska, which are coincident with geometric changes in the thrust front transition from the mobile belt to stable cratonic North America. The inferred early Proterozoic magmatic arc complex along the western edge of the North American craton likely influenced later tectonic evolution, by acting as a buttress along the inboard margin of the Cordilleran fold-and-thrust belt. Crown Copyright ?? 2008.

  13. Geomagnetic modulation of clouds effects in the Southern Hemisphere Magnetic Anomaly through lower atmosphere cosmic ray effects

    NASA Astrophysics Data System (ADS)

    Vieira, Luis Eduardo Antunes; da Silva, Ligia Alves

    2006-07-01

    The study of the physical processes that drive the variability of the Earth's climate system is one of the most fascinating and challenging topics of research today. Perhaps the largest uncertainties in our ability to predict climate change are the cloud formation process and the interaction of clouds with radiation. Here we show that in the southern Pacific Ocean cloud effects on the net radiative flux in the atmosphere are related to the intensity of the Earth's magnetic field through lower atmosphere cosmic ray effects. In the inner region of the Southern Hemisphere Magnetic Anomaly (SHMA) it is observed a cooling effect of approximately 18 W/m2 while in the outer region it is observed a heating effect of approximately 20 W/m2. The variability in the inner region of the SHMA of the net radiative flux is correlated to galactic cosmic rays (GCRs) flux observed in Huancayo, Peru (r = 0.73). It is also observed in the correlation map that the correlation increases in the inner region of the SHMA. The geomagnetic modulation of cloud effects in the net radiative flux in the atmosphere in the SHMA is, therefore, unambiguously due to GCRs and/or highly energetic solar proton particles effects.

  14. Comparison of the dynamics and structure of Saturn and Jupiter magnetospheres: camshaft, magnetic anomalies and corotating convection models compared.

    NASA Astrophysics Data System (ADS)

    Southwood, D. J.; Kivelson, M. G.

    Scenarios are presented for the overall flux and mass circulation in the jovian and saturnian magnetospheres It is argued that similar fundamanetal processes underly the dynamical processes at both planets However the differences in parameter regime for the two systems leads to substantial resulting differences in morphology Transport is accomplished from the inner magnetosphere by interchange motion which then feeds into the outer magnetosphere where ballooning driven by centrifugal stress leads to field reconnection and plasma loss It seems likely that Jupiter loses much more material per rotation cycle than Saturn and is possibly much more symmetrically loaded in respect of planetary longitude Material loss and flux return at Jupiter have fixed orientations in local time early evening and morning sector respectively and newly returned flux is probably responsible for the morningside cushion region in the outer magnetosphere At Jupiter the dawn-dusk asymmetry in the current sheet thin in morning thick in afternoon is also a dominant feature At Saturn there seems no evidence of a cushion region flux return is thought to take place sporadically over much of the nightside Although definitive statements about the dusk plasma sheet await the orbit evolution of Cassini a fundamental observational feature in the Saturnian context is a planetary rotation induced magnetic field asymmetry which argues against major dawn-dusk asymmetry We propose the rotational feature could originate from a localized ionospheric magnetic anomaly The

  15. Gorringe Ridge gravity and magnetic anomalies are compatible with thrusting at a crustal scale

    NASA Astrophysics Data System (ADS)

    Galindo-Zaldívar, J.; Maldonado, A.; Schreider, A. A.

    2003-06-01

    The main features of the deep structure of the Gorringe Ridge are analysed on the basis of gravity and magnetic measurements, as well as seismic profiles, drill holes, rock dredges, submersible observations and seismicity data. The gravity and magnetic models of the Gettysburg and Ormonde seamounts, which form the Gorringe Ridge, suggest that the Moho is approximately flat and the upper part of the ridge corresponds to a northwestwards vergent fold. This structure is the result of a northwestward vergent thrust that deformed the oceanic crust, with a minimum slip of approximately 20 km. The activity of the thrust probably started 20 Myr, and produced the recent stages of seamount uplift. The seamount is mainly composed of gabbros of the oceanic crust, serpentinized rocks and alkaline basalts. The large antiform, located in the hangingwall of the thrust, is probably deformed by minor faults. This oceanic ridge is a consequence of the oblique convergence between the African Plate and the overlapping Eurasian Plate.

  16. Positive holes in magnesium oxide - Correlation between magnetic, electric, and dielectric anomalies

    NASA Technical Reports Server (NTRS)

    Batllo, F.; Leroy, R. C.; Parvin, K.; Freund, F.; Freund, M. M.

    1991-01-01

    The present magnetic susceptibility investigation of high purity MgO single crystals notes an anomally at 800 K which is associated with increasing electrical conductivity, a rise in static dielectric constant from 9 to 150, and the appearance of a pronounced positive surface charge. These phenomena can be accounted for in terms of peroxy defects which represent self-trapped, spin-paired positive holes at Mg(2+) vacancy sites. The holes begin to decouple their spins above 600 K.

  17. Study of the magnetic structure of multilayers and of an ultracold neutron storage anomaly

    NASA Astrophysics Data System (ADS)

    Sarkisov, Dmitry

    This thesis describes the results of polarized neutron reflectometry experiments with spin-valve samples performed at the National Institute of Standards and Technology (Gaithersburg, MD). The study was motivated by the strong technological interest in spin-valve structures exhibiting the effect of giant magnetoresistance. This phenomenon has been widely utilized in a new generation of magnetoresistive memory, reading heads for magnetic disk drives, and field sensors. The study showed that the interfacial roughness strongly depends on the conditions of sample preparation. We have also observed a non-collinear coupling of magnetization between the ferromagnetic layers of the spin-valve samples. The signs of the coupling constants were determined from the neutron reflectometry data using a minimum energy model for the relative orientations of magnetization. The results are consistent with the theoretical values obtained from the RKKY model of oscillatory exchange coupling. We also present the results of specific ultracold neutron (UCN) storage experiments performed at the Institut Laue-Langevin (Grenoble, France). We investigated certain anomalous features of UCN storage. The UCN were filled into a container whose walls were coated by a good neutron reflector (Fomblin grease). Then the neutrons were quickly removed by an absorber, until their residual density in the trap was measured to be negligible. Nevertheless, when the absorber was withdrawn, a measurable number of neutrons emerged from the trap. We have also found that application of a magnetic field gradient at the trap bottom as well as replacement of some Fomblin grease by liquid Fornblin oil gave rise to alterations of UCN count rate. These surprising phenomena are not well understood so far and require further experimental study.

  18. Seeded growth of ferrite nanoparticles from Mn oxides: observation of anomalies in magnetic transitions.

    PubMed

    Song, Hyon-Min; Zink, Jeffrey I; Khashab, Niveen M

    2015-07-28

    A series of magnetically active ferrite nanoparticles (NPs) are prepared by using Mn oxide NPs as seeds. A Verwey transition is identified in Fe3O4 NPs with an average diameter of 14.5 nm at 96 K, where a sharp drop of magnetic susceptibility occurs. In MnFe2O4 NPs, a spin glass-like state is observed with the decrease in magnetization below the blocking temperature due to the disordered spins during the freezing process. From these MnFe2O4 NPs, MnFe2O4@Mn(x)Fe(1-x)O core-shell NPs are prepared by seeded growth. The structure of the core is cubic spinel (Fd3¯m), and the shell is composed of iron-manganese oxide (Mn(x)Fe(1-x)O) with a rock salt structure (Fm3¯m). Moiré fringes appear perpendicular to the 〈110〉 directions on the cubic shape NPs through the plane-matched epitaxial growth. These fringes are due to the difference in the lattice spacings between MnFe2O4 and Mn(x)Fe(1-x)O. Exchange bias is observed in these MnFe2O4@Mn(x)Fe(1-x)O core-shell NPs with an enhanced coercivity, as well as the shift of hysteresis along the field direction.

  19. Magnetic anomalies in the Imbrium and Schrödinger impact basins: Orbital evidence for persistence of the lunar core dynamo into the Imbrian epoch

    NASA Astrophysics Data System (ADS)

    Hood, L. L.; Spudis, P. D.

    2016-11-01

    Approximate maps of the lunar crustal magnetic field at low altitudes in the vicinities of the three Imbrian-aged impact basins, Orientale, Schrödinger, and Imbrium, have been constructed using Lunar Prospector and Kaguya orbital magnetometer data. Detectable anomalies are confirmed to be present well within the rims of Imbrium and Schrödinger. Anomalies in Schrödinger are asymmetrically distributed about the basin center, while a single isolated anomaly is most clearly detected within Imbrium northwest of Timocharis crater. The subsurface within these basins was heated to high temperatures at the time of impact and required long time periods (up to 1 Myr) to cool below the Curie temperature for metallic iron remanence carriers (1043 K). Therefore, consistent with laboratory analyses of returned samples, a steady, long-lived magnetizing field, i.e., a former core dynamo, is inferred to have existed when these basins formed. The asymmetrical distribution within Schrödinger suggests partial demagnetization by later volcanic activity when the dynamo field was much weaker or nonexistent. However, it remains true that anomalies within Imbrian-aged basins are much weaker than those within most Nectarian-aged basins. The virtual absence of anomalies within Orientale where impact melt rocks (the Maunder Formation) are exposed at the surface is difficult to explain unless the dynamo field was much weaker during the Imbrian period.

  20. Identification des anomalies magnétiques sur les dorsales à faible taux d'expansion: Méthode des taux fictifs

    NASA Astrophysics Data System (ADS)

    Tisseau, J.; Patriat, Ph.

    1981-02-01

    The fit between calculated and observed magnetic anomalies from slow-spreading centers is improved when allowing for a transition zone between two inversely magnetized blocks. In this paper it is shown that these models are very easily computed by choosing a fictitious spreading rate which is slower than the real spreading rate and by changing the distance scale appropriately. With these slow fictitious spreading rates, the models are very sensitive to the relative position of the successive inversions and could be used to adjust these positions in the magnetic time scales.

  1. Aeromagnetic anomalies and discordant lineations beneath the Niger Delta: Implications for new fracture zones and multiple sea-floor spreading directions in the meso-Atlantic' Gulf of Guinea cul-de-sac

    SciTech Connect

    Babalola, O.O.; Gipson, M. Jr. )

    1991-06-01

    An aeromagnetic contour map compiled over shallow water and onshore portions of the Nigerian continental margin, shows several elongate, long-wavelength anomaly closures with some alternating polarity, separated by steep gradient, NE lineations. The lineations are interpreted as new fracture zones or extensions of previously mapped ones. The NE trend in the western delta region is concordant with the fracture zone trends of the deeper Gulf of Guinea. Aeromagnetic lineations of the SE Niger Delta Basin however, discordantly trend ENE. Their termination against the former, is interpreted as evidence of early sea-floor spreading in a ENE-WSW direction in addition to the well documented NE-SW spreading of the Gulf of Guinea and the rest of the meso-Atlantic sea-floor; The geophysical crustal structure indicate the existence of two Early Cretaceous triple junctions beneath the Niger Delta Basin. The two triple-junctions further support the hypothesis that the African continent was a multi-plate system (in the Niger Delta region) during the early opening of the Atlantic.

  2. About the Las Acacias, Trelew and Vassouras Magnetic Observatories Monitoring the South Atlantic Magnetic Anomaly Region Response to an Interplanetary Coronal Mass Ejection

    NASA Astrophysics Data System (ADS)

    Gianibelli, J. C.; Quaglino, N. M.

    2007-05-01

    The South Atlantic Magnetic Anomaly (SAMA) Region presents evolutive characteristics very important as were observed by a variety of satelital sensors. Important Magnetic Observatories with digital record monitor the effects of the Sun-Earth interaction, such as San Juan de Puerto Rico (SJG), Kourou (KOU), Vassouras (VSS), Las Acacias (LAS), Trelew (TRW), Vernadsky (AIA), Hermanus (HER) and Huancayo (HUA). In the present work we present the features registered during the geomagnetic storm in January 21, 2005, produced by a geoeffective Coronal Mass Ejection (CME) whose Interplanetary Coronal Mass Ejection (ICME) was detected by the instrumental onboard the Advanced Composition Explorer (ACE) Sonde. We analize how the Magnetic Total Intensity records at VSS, TRW and LAS Observatories shows the effect of the entering particles to ionospherical dephts producing a field enhancement following the first Interplanetary Shock (IP) arrival of the ICME. This process manifest in the digital record as an increment over the magnetospheric Ring Current field effect and superinpossed effects over the Antarctic Auroral Electrojet. The analysis and comparison of the records demonstrate that the Ring Current effects are important in SJG and KOU but not in VSS, LAS and TRW observatories, concluding that SAMA region shows a enhancement of the ionospherical currents oposed to those generated at magnetospheric heighs. Moreover in TRW, 5 hours after the ICME shock arrival, shows the effect of the Antarctic Auroral Electrojet counteracting to fields generated by the Ring Current.

  3. Cosmic rays modulation of the cloud effects on the radiative flux in the Southern Hemisphere Magnetic Anomaly region

    NASA Astrophysics Data System (ADS)

    Vieira, L. E.; Silva, L.

    Aerosols are thought to cool the planet s surface through increase scattering and cloud cover and re-radiation of solar energy to space Clouds play an important role in the Earth s radiation budget through trapping outgoing radiation and reflecting incoming radiation Climate models have some representation of direct aerosol effects in them but none have yet fully included the indirect effects A correlation between a global average of low cloud cover and the flux of Galactic Cosmic Rays GCRs incident in the atmosphere has been observed recently The ionizing potential of Earth bound cosmic ray is modulated by the state of the heliosphere which depends on the solar activity 5 Here we show that in the southern Pacific Ocean the cloud effects on the net radiative flux in the atmosphere depends on the intensity of the Earth s magnetic field In the inner region of the Southern Hemisphere Magnetic Anomaly SHMA it is observed a cooling effect of approximately 18 W m 2 while in the outer region it is observed a heating effect of approximately 20 W m 2 The variability in the inner region of SHMA of the net radiative flux is correlated to GCRs flux observed in Huancayo Peru r 0 73 It is observed that correlation decrease as the intensity of the Earth s magnetic field intensity increase The observations are in agreement with the robust mechanism proposed by Brian Tinsley to explain the cloud formation due to GCRs atmospheric ionization The representation of GCRs induced cloud formation process in Coupled Atmosphere-Ocean General

  4. A New Best-Estimate Methodology for Determining Magnetic Parameters Related to Field Anomalies Produced by Buried Thin Dikes and Horizontal Cylinder-like Structures

    NASA Astrophysics Data System (ADS)

    Tlas, M.; Asfahani, J.

    2011-05-01

    A new best estimate methodology is proposed and oriented towards the determination of parameters related to a magnetic field anomaly produced by a simple geometric-shaped model or body such as a thin dike and horizontal cylinder. This approach is mainly based on solving a system of algebraic linear equations for estimating the three model parameters, e.g., the depth to the top (center) of the body ( z), the index parameter or the effective magnetization angle ( θ) and the amplitude coefficient or the effective magnetization intensity ( k). The utility and validity of this method is demonstrated by analyzing two synthetic magnetic anomalies, using simulated data generated from a known model with different random errors components and a known statistical distribution. This approach was also examined and applied to two real field magnetic anomalies from the United States and Brazil. The agreement between the results obtained by the proposed method and those obtained by other interpretation methods is good and comparable. Moreover, the depth obtained by such an approach is found to be in high accordance with that obtained from drilling information. The advantages of such a proposed method over other existing interpretative techniques are clarified, where it can be generalized to be automatically applicable for interpreting other geological structures described by mathematical formulations.

  5. Curie isotherm surfaces inferred from high-altitude magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Mayhew, M. A.

    1985-01-01

    Two-dimensional Curie depth models along two sections across the western United States are derived using an equivalent layer magnetization model derived from Magsat data, and the results are used to constrain finite element thermal models developed by Mayhew and Majer (1980). Regional heat flow variations predicted by the models compare favorably with those inferred from direct measurements. The methodology is applied to upward-continued aeromagnetic data, and the results are found to be in good agreement with previous Curie depth estimates and average measured heat flow.

  6. Enhanced magnetic anomaly detection using a nitrogen-cooled superconducting gradiometer

    NASA Astrophysics Data System (ADS)

    Clem, Ted R.; Overway, David J.; Purpura, John W.; Bono, John T.; Carroll, Paul J.; Koch, Roger H.; Rozen, James R.; Keefe, George A.; Willen, Scott; Mohling, Robert A.

    2000-07-01

    During the 1980's the Superconducting Gradiometer/Magnetometer Sensor was demonstrated in the Magnetic and Acoustic Detection of Mines Advanced Technology Demonstration to provide effective mine detection, localization, and classification capabilities, especially against buried mines, and to reduce significantly acoustic false alarms arising from bottom clutter. This sensor utilized Superconducting Quantum Interference Devices manufactured using the low critical temperature (low Tc) superconductor niobium and liquid helium for sensor cooling. This sensor has most recently bee integrated into the Mobile Underwater Debris Survey System and has been demonstrated successfully in a survey to locate unexploded ordnance in coastal waters.

  7. Influence of the equatorial irregularities and precipitations in the South Atlantic magnetic anomaly on the generation of auroral-type plasma instabilities

    SciTech Connect

    Prange, R.; Bruston, P.

    1980-08-01

    Observational evidence of upward field-aligned beams in the keV range has been obtained in the sub-equatorial ionosphere above South America. These events can be related to coupled magnetic and ionospheric activity (magnetic storm, ionospheric irregularities). This result is in opposition with the current theory of the low-latitude ionosphere. Its interpretation must assume that conditions exist for the growth of plasma instabilities. This implies a low plasma density, a close coupling between the ionosphere and the magnetosphere, and field-aligned currents. Such suitable conditions have independently been observed in ionospheric irregularities (density, currents) or during magnetic storms (energetic particle precipitation) or they are deduced from the structure of the Anomaly (field-aligned currents). This allows us to suggest that the South Atlantic Anomaly sometimes compares to the auroral oval and may develop some current-driven plasma instabilities.

  8. Acoustic anomalies in UPt{3} at high magnetic fields and low temperatures.

    SciTech Connect

    Feller, J. R.; Ketterson, J. B.; Hinks, D. G.; Dasgupta, D.; Sarma, B. K.; Materials Science Division; Northwestern Univ.; Univ. of Wisconsin at Milwaukee

    2000-11-01

    Ultrasound velocity and attenuation measurements were performed on single crystals of the heavy fermion compound UPt{sub 3} in magnetic fields up to 33 T and at temperatures ranging from 2.4 K to below 0.1 K. With longitudinal sound propagated in the crystallographic basal plane, parallel to the applied field, the familiar elastic softening is observed at the metamagnetic transition field H-20.2 T. More complicated structure emerges at low temperatures, including quantum acoustic oscillations and a second velocity minimum at -21.6 T. A weak frequency dependence (dispersion) is observed in the velocity. The ultrasonic data are analyzed using the Landau-Khalatnikov formalism, from which temperature- and field-dependent relaxation times are deduced.

  9. Gulf of california: a result of ocean-floor spreading and transform faulting.

    PubMed

    Larson, R L; Menard, H W; Smith, S M

    1968-08-23

    Ocean-floor spreading tore southern Baja California from mainland Mexico 4 million years ago and has subsequently rafted it 260 kilometers to the northwest along the Tamayo Fracture Zone. Magnetic-anomaly profiles indicate spreading at the mouth of the gulf at 3.0 centimeters per year and a rise-crest offset of 75 kilometers inside the gulf across the Tamayo Fracture Zone.

  10. Phonon Drag and Magnetic Anomalies, of Thermopower, in RB12 (R = Ho, Er, Tm, Lu)

    NASA Astrophysics Data System (ADS)

    Glushkov, V.; Demishev, S.; Ignatov, M.; Khayrullin, E.; Sluchanko, N.; Shitsevalov, N.; Levchenko, A.; Filipov, V.; Flachbart, K.; Siemensmeyer, K.

    2008-01-01

    High precision measurements of the Seebeck coefficient S(T) were carried out on the single crystals of RB12 (R = Ho, Er, Tm, Lu) at temperatures 2-300 K. It was shown that the effects of phonon drag result from vibrations of rare earth ions (ℏ ωE≈10-33 meV) in the rigid framework structure of the B12 clusters and determine the main contribution to thermopower at intermediate temperatures (30-300 K). The correlated behavior of transport parameters favors the appreciable enhancement of spin fluctuations in the sequence of magnetic compounds (HoB12-TmB12) when approaching to the valence instability state in YbB12. The giant increase in S(T) detected in the vicinity of the Néel temperature TN for HoB12, ErB12, and TmB12 seems to result from the density of states renormalization caused by antiferromagnetic ordering.

  11. Bahía de Banderas, Mexico: Morphology, Magnetic Anomalies and Shallow Structure

    NASA Astrophysics Data System (ADS)

    Mortera Gutiérrez, Carlos A.; Bandy, William L.; Ponce Núñez, Francisco; Pérez Calderón, Daniel A.

    2016-10-01

    The Bahía de Banderas lies within a tectonically complex area at the northern end of the Middle America Trench. The structure, morphology, subsurface geology and tectonic history of the bay are essential for unraveling the complex tectonic processes occurring in this area. With this focus, marine geophysical data (multi-beam bathymetry, high resolution seismic reflection and total field magnetic data) were collected within the bay and adjacent areas during four campaigns aboard the B.O. EL PUMA conducted in 2006 and 2009. These data image the detailed morphology of, and sedimentation patterns within, the Banderas Canyon (a prominent submarine canyon situated on the south side of the bay) as well as the shallow subsurface structure of the northern part of the bay and the submarine Marietas Ridge, which bounds the bay to the west. We find that the Marietas Ridge is presently a transtensional feature; the course of the Banderas Canyon is controlled by extensive turbidite fan sedimentation in its eastern extremity and by structural lineaments to the west; the canyon floor is filled by sediments and exhibits almost no evidence for recent tectonic movements; the southern canyon wall is quite steep and a few sediments are deposited as submarine fans at the base of the southern wall; and extensive turbidite fans form the lower part of the northern canyon wall, producing a gently sloping lower northern wall. We find no evidence for a regional east-west striking lineament between the bay and the Middle America Trench, which casts doubts on the previous assertion that the Banderas Canyon is unequivocally related to the presence of a regional half-graben. Finally, a N71°E oriented normal fault offsets the seafloor reflector by 15 m within the central part of the bay, suggesting that the bay is currently being subjected to NNW-SSE extension.

  12. The sea-floor spreading history of the eastern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Powell, Thomas S.; Luyendyk, Bruce P.

    1982-09-01

    The geologic history of the eastern Indian Ocean between northwest Australia and the Java Trench is known to involve two separate events of rifting and sea-floor spreading. Late Jurassic spreading in the Argo Abyssal Plain off northwest Australia was followed by Early Cretaceous spreading in the Cuvier and Perth Abyssal Plains off west Australia. However, the evolution and interaction of these events has not been clear. Mesozoic sea-floor spreading anomalies have been identified throughout the Argo Abyssal Plain that define a rifting event and subsequent northward spreading on the northwestern Australian margin at 155 m.y.b.p. Magnetic anomalies northwest of the Argo Abyssal Plain indicate a ridge jump to the south at about 130 m.y.b.p. that is approximately synchronous with east-west rifting along the southwestern Australian margin. The Joey Rise in the Argo Plain was probably formed by volcanism at the intersection of this new rift and the spreading ridge to the north. The southern and northern spreading systems were connected through the Exmouth Plateau which was stretched and faulted as spreading progressed. The RRR triple junction was formed at the intersection of the two spreading systems and appears to have migrated west along the northern edge of the Gascoyne Abyssal Plain. Spreading off northwest Australia cannot be easily related to simultaneous spreading in the west central Pacific via any simple tectonic scheme.

  13. Magnetic Resonance Imaging (MRI) Depiction of Robert’s Uterus: A Rare Müllerian Duct Anomaly Presenting with Cyclical Pain in Young Menstruating Woman

    PubMed Central

    Mittal, Puneet; Gupta, Ranjana; Mittal, Amit; Taneja, Arpit; Sekhon, Preetparkash Singh; Gupta, Sharad

    2017-01-01

    Summary Background Robert’s uterus is a very rare müllerian duct anomaly which is characterised by septate uterus with obstruction of a one-sided cavity and formation of hematometra. Therefore, patients present with cyclical abdominal pain during menstruation along with normal menstrual flow. Case Report We present magnetic resonance imaging (MRI) findings in a case of Robert’s uterus in a young woman. Conclusions Robert’s uterus is a very rare anomaly which can be very well characterized by magnetic resonance imaging (MRI). MRI can also show any associated hematometra and endometriomas complicating this condition and aid in the institution of appropriate management in such cases. PMID:28348653

  14. Gravity and magnetic anomalies used to delineate geologic features associated with earthquakes and aftershocks in the central Virginia seismic zone

    NASA Astrophysics Data System (ADS)

    Shah, A. K.; Horton, J.; McNamara, D. E.; Spears, D.; Burton, W. C.

    2013-12-01

    Estimating seismic hazard in intraplate environments can be challenging partly because events are relatively rare and associated data thus limited. Additionally, in areas such as the central Virginia seismic zone, numerous pre-existing faults may or may not be candidates for modern tectonic activity, and other faults may not have been mapped. It is thus important to determine whether or not specific geologic features are associated with seismic events. Geophysical and geologic data collected in response to the Mw5.8 August 23, 2011 central Virginia earthquake provide excellent tools for this purpose. Portable seismographs deployed within days of the main shock showed a series of aftershocks mostly occurring at depths of 3-8 km along a southeast-dipping tabular zone ~10 km long, interpreted as the causative fault or fault zone. These instruments also recorded shallow (< 4 km) aftershocks clustered in several areas at distances of ~2-15 km from the main fault zone. We use new airborne geophysical surveys (gravity, magnetics, radiometrics, and LiDAR) to delineate the distribution of various surface and subsurface geologic features of interest in areas where the earthquake and aftershocks took place. The main (causative fault) aftershock cluster coincides with a linear, NE-trending gravity gradient (~ 2 mgal/km) that extends over 20 km in either direction from the Mw5.8 epicenter. Gravity modeling incorporating seismic estimates of Moho variations suggests the presence of a shallow low-density body overlying the main aftershock cluster, placing it within the upper 2-4 km of the main-fault hanging wall. The gravity, magnetic, and radiometric data also show a bend in generally NE-SW orientation of anomalies close to the Mw5.8 epicenter. Most shallow aftershock clusters occur near weaker short-wavelength gravity gradients of one to several km length. In several cases these gradients correspond to geologic contacts mapped at the surface. Along the gravity gradients, the

  15. Non-magnetic Anomaly at 1K Arising in Ferromagnetic Ce2.15(Pd1-xAgx)1.95In0.9

    NASA Astrophysics Data System (ADS)

    Sereni, J. G.; Giovannini, M.; Berisso, M. Ǵomez; Gastaldo, F.

    Magnetic and thermal properties of Ferromagnetic (FM) Ce2.15(Pd1-xAgx)1.95In0.9 alloys were studied in order to determine the Quantum Critical Point (QCP) at TC → 0. The in- crease of band electrons produced by Pd/Ag substitution depresses TC (x) from 4.1K down to TC (x = 0.5)=1.1K, with a QCP extrapolated to xQCP ≥ 0.5. Magnetic susceptibility from T > 30K indicates an effective moment slightly decreasing from μeff =2.56μB to 2.4μB at x=0.5. These values and the paramagnetic temperature θP ≈ -10K exclude significant Kondo screening effects. The TC (x) reduction is accompanied by a weakening of the FM magnetization and the emergence of a specific heat Cm(T) anomaly at T* ≈ 1K, without signs of magnetism detected from AC-susceptibility. The magnetic entropy collected around 4K (i.e. the TC of the x = 0 sample) practically does not change with Ag concentration: Sm(4K) ≈ 0.8 Rln2, suggesting a progressive transfer of FM degrees of freedom to the non-magnetic (NM) compo- nent. No antecedent was found concerning any NM anomaly emerging from a FM system at such temperature. The origin of this anomaly is attributed to an entropy bottleneck originated in the nearly divergent power law dependence for T >T*

  16. Long periods (1 -10 mHz) geomagnetic pulsations variation with solar cycle in South Atlantic Magnetic Anomaly

    NASA Astrophysics Data System (ADS)

    Rigon Silva, Willian; Schuch, Nelson Jorge; Guimarães Dutra, Severino Luiz; Babulal Trivedi, Nalin; Claudir da Silva, Andirlei; Souza Savian, Fernando; Ronan Coelho Stekel, Tardelli; de Siqueira, Josemar; Espindola Antunes, Cassio

    The occurrence and intensity of the geomagnetic pulsations Pc-5 (2-7 mHz) and its relationship with the solar cycle in the South Atlantic Magnetic Anomaly -SAMA is presented. The study of geomagnetic pulsations is important to help the understanding of the physical processes that occurs in the magnetosphere region and help to predict geomagnetic storms. The fluxgate mag-netometers H, D and Z, three axis geomagnetic field data from the Southern Space Observatory -SSO/CRS/INPE -MCT, São Martinho da Serra (29.42° S, 53.87° W, 480m a.s.l.), RS, Brasil, a were analyzed and correlated with the solar wind parameters (speed, density and temperature) from the ACE and SOHO satellites. A digital filtering to enhance the 2-7 mHz geomagnetic pulsations was used. Five quiet days and five perturbed days in the solar minimum and in the solar maximum were selected for this analysis. The days were chosen based on the IAGA definition and on the Bartels Musical Diagrams (Kp index) for 2001 (solar maximum) and 2008 (solar minimum). The biggest Pc-5 amplitude averages differences between the H-component is 78,35 nT for the perturbed days and 1,60nT for the quiet days during the solar maximum. For perturbed days the average amplitude during the solar minimum is 8,32 nT, confirming a direct solar cycle influence in the geomagnetic pulsations intensity for long periods.

  17. THEOS-2 Orbit Design: Formation Flying in Equatorial Orbit and Damage Prevention Technique for the South Atlantic Magnetic Anomaly (SAMA)

    NASA Astrophysics Data System (ADS)

    Pimnoo, Ammarin

    2016-07-01

    Geo-Informatics and Space Technology Development Agency (GISTDA) has initiative THEOS-2 project after the THEOS-1 has been operated for more than 7 years which is over the lifetime already. THEOS-2 project requires not only the development of earth observation satellite(s), but also the development of the area-based decision making solution platform comprising of data, application systems, data processing and production system, IT infrastructure improvement and capacity building through development of satellites, engineering model, and infrastructures capable of supporting research in related fields. The developing satellites in THEOS-2 project are THAICHOTE-2 and THAICHOTE-3. This paper focuses the orbit design of THAICHOTE-2 & 3. It discusses the satellite orbit design for the second and third EOS of Thailand. In this paper, both THAICHOTE will be simulated in an equatorial orbit as a formation flying which will be compared the productive to THAICHOTE-1 (THEOS-1). We also consider a serious issue in equatorial orbit design, namely the issue of the geomagnetic field in the area of the eastern coast of South America, called the South Atlantic Magnetic Anomaly (SAMA). The high-energy particles of SAMA comprise a radiation environment which can travel through THAICHOTE-2 & 3 material and deposit kinetic energy. This process causes atomic displacement or leaves a stream of charged atoms in the incident particles' wake. It can cause damage to the satellite including reduction of power generated by solar arrays, failure of sensitive electronics, increased background noise in sensors, and exposure of the satellite devices to radiation. This paper demonstrates the loss of ionizing radiation damage and presents a technique to prevent damage from high-energy particles in the SAMA.

  18. MAGSAT anomaly map and continental drift

    NASA Technical Reports Server (NTRS)

    Lemouel, J. L. (Principal Investigator); Galdeano, A.; Ducruix, J.

    1981-01-01

    Anomaly maps of high quality are needed to display unambiguously the so called long wave length anomalies. The anomalies were analyzed in terms of continental drift and the nature of their sources is discussed. The map presented confirms the thinness of the oceanic magnetized layer. Continental magnetic anomalies are characterized by elongated structures generally of east-west trend. Paleomagnetic reconstruction shows that the anomalies found in India, Australia, and Antarctic exhibit a fair consistency with the African anomalies. It is also shown that anomalies are locked under the continents and have a fixed geometry.

  19. Crustal thickness and Vp/Vs estimates near the Brunswick magnetic anomaly using receiver functions from the SESAME array

    NASA Astrophysics Data System (ADS)

    Parker, E. H.; Hawman, R. B.; Fischer, K. M.; Wagner, L. S.

    2012-12-01

    The Southeastern Suture of the Appalachian Margin Experiment (SESAME) is designed to investigate lithospheric dynamics associated with the Paleozoic collision between the Suwanee terrane and Laurentia as well as subsequent Mesozoic rifting and passive margin formation. So far, we have deployed 63 broadband instruments along two N-S trending profiles across Georgia and northern Florida. A third NW-trending profile consisting of 19 stations extends across accreted terranes of the southern Appalachians from Augusta, GA to eastern TN. The N-S profiles are intended to provide constraints on variations in crustal structure across the Brunswick magnetic anomaly (BMA), a prominent magnetic low coinciding with south-dipping crustal-scale seismic reflectors evident on COCORP profiles in south Georgia. The seismic reflectivity is likely a consequence of suturing, but the BMA has been interpreted as an edge effect related to collision as well as an effect of mafic magmatism south of the suture zone. H-k stacking using 10 teleseismic receiver functions from station W27, located ~50-km north of the suture on the western N-S profile, suggests a crustal thickness (H) of 42-44 km and average crustal Vp/Vs (k) of 1.73-1.80. These estimates are in agreement with previous well-constrained stacking results from USNSN station GOGA, located ~70-km to the northeast, that suggest a crustal thickness of 41-43 km and average Vp/Vs 1.72-1.76. The proposed suture zone itself lies beneath sediments of the Atlantic Coastal Plain, and receiver functions from stations in this region appear to be strongly affected by high-amplitude reverberations within the sedimentary column. Therefore, preliminary H-k stacking results from stations directly over the BMA may be unreliable. However, receiver functions from station W23 near the Inner Piedmont-Coastal Plain boundary (near the north, up-dip end of the suture zone) display variations in Ps delay time and amplitude with event back-azimuth. Receiver

  20. Negative Magnetic Anomalies Observed in the Central West Antarctica (CWA) Aerogeophysical Survey Over the West Antarctic Ice Sheet (WAIS), Whose Sources are Volcanic Centers (e.g. Mt Resnik) at the Base of the ice >780 Ka

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.; Finn, C. A.; Morse, D. L.; Blankenship, D. D.

    2005-12-01

    Analysis of a block of coincident aeromagnetic and radar ice-sounding data (from the CWA aerogeophysical survey) over the WAIS reveals ~1000 50->1000-nT, shallow -source, ``volcanic" magnetic anomalies, interpreted as caused by late Cenozoic alkaline magmatism associated with the West Antarctic rift system (WR). About 400 of these anomalies (conservatively selected) have topographic expression at the bed of the WAIS; >80% of these topographic features have <200 m bed relief. There are ~100 short-wavelength, steep-gradient, negative magnetic anomalies observed in the CWA survey, or ~10% of the ~1000 ``volcanic" anomalies. These negative anomalies indicate volcanic activity during a time of magnetic field reversal from normal to reversed polarity at least as old as 780 Ka (the Brunes-Matuyama reversal). The sources of ~18 of the anomalies, half concentrated in the area of the WAIS divide, have high bed-elevation (above sea level after ice removal and glacial rebound), very magnetic topography of high bed relief, up to 2 km. Five of these peaks have associated negative magnetic anomalies. One of the high topographic features, Mt. Resnik, marked by a complex negative anomaly, is a conical peak 300 m below the surface of the WAIS, and has ~2 km topographic relief. We interpret a magnetic model fit to this anomaly as comprising reversely magnetized (in the present field direction), 0.5-2.5-km thick volcanic flows at the summit overlying normally magnetized flows. Published models (1996) reported for the Hut Point anomaly, at Ross Island, Antarctica, a similar anomaly to Mt. Resnik, also required both normal and reversed magnetizations correlated with drill holes into dated volcanic flows (also part of the late Cenozoic WR) crossing the Brunhes-Matuyama boundary (780 Ka). Because of their form similar to exposed volcanoes in the WAIS area with edifices primarily comprising subaerially-erupted, very magnetic volcanic flows, which have resisted glacial erosion, Behrendt et

  1. Earth analog for Martian magnetic anomalies: remanence properties of hemo-ilmenite norites in the Bjerkreim-Sokndal intrusion, Rogaland, Norway

    NASA Astrophysics Data System (ADS)

    McEnroe, S. A.; Brown, L. L.; Robinson, Peter

    2004-10-01

    To explain the very large remanent magnetic anomalies on Mars, which no longer has a global magnetic field, it is important to evaluate rocks on Earth with the necessary properties of high natural remanent magnetization (NRM) and coercivity. Here, we describe a possible analog from the 230-km 2 930 Ma Bjerkreim-Sokndal layered intrusion (BKS) in Rogaland, Norway. In the layered series of the BKS, fractional crystallization of jotunitic magma was punctuated by influx and mixing of more primitive magmas, producing six megacyclic units, each typically with early plagioclase-rich norites, intermediate hemo-ilmenite-rich norites and late magnetite norites with subordinate near end-member ilmenite. Following each influx, the magma resumed normal crystallization and, following the last, near the base of Megacyclic Unit IV, crystallization continued until norites gave way to massive fayalite-magnetite mangerites and quartz mangerites in the upper part of the intrusion. The Megacycles are marked on a regional aeromagnetic map by remanent-controlled negative anomalies over ilmenite norites and induced positive anomalies over magnetite norites and mangerites. A prominent negative anomaly (with amplitude -13,000 nT in a high-resolution helicopter survey, down to -27,000 nT below background in ground magnetic profiles) occurs over the central part of Megacyclic Unit IV. The anomaly is centered on ilmenite norite Unit IVe and is most intense where cumulate layering is near vertical at the southeast edge of the Bjerkreim Lobe of the intrusion at Heskestad. Here, Unit IVe is flanked to the east by magnetite norite of Unit IVc and country-rock gneisses (group E) and to the west by Unit IVf magnetite norite and mangerites (group W). Magnetic properties were measured on 128 oriented samples. Susceptibilities are similar for all three sample groups at ˜8×10 -2, but Koenigsberger ratios are very different, with average values of 7.7 for IVe, and <1 for groups E and W. The IVe samples

  2. 3-D Full-kinetic Simulations of the Solar Wind Interaction with Lunar Magnetic Anomalies: Particle Behaviour

    NASA Astrophysics Data System (ADS)

    Deca, J.; Divin, A. V.; Wang, X.; Lembege, B.; Markidis, S.; Lapenta, G.; Horanyi, M.

    2015-12-01

    We present three-dimensional full-kinetic electromagnetic simulations of the solar wind interaction with lunar crustal magnetic anomalies (LMAs). Using the implicit particle-in-cell code iPic3D, we confirm that LMAs may indeed be strong enough to stand off the solar wind from directly impacting the lunar surface forming a mini-magnetosphere, as suggested by spacecraft observations and theory. In contrast to earlier MHD and hybrid simulations, the full-kinetic nature of iPic3D allows to self-consistently investigate space charge effects, and in particular the electron dynamics dominating the near-surface lunar plasma environment. We describe the general mechanism of the interaction of both a horizontal and vertical dipole model embedded just below the lunar surface focussing on the ion and electron kinetic behaviour of the system. It is shown that the configurations are largely dominated by electron motion, because the LMA scale size is small with respect to the gyro-radius of the solar wind ions. The formation of mini-magnetospheres is an electrostatic effect. Additionally, we discuss typical particle trajectories as well as complete particle distribution functions covering thermal and suprathermal energies, within the interaction region and on viable spacecraft altitudes. Our work opens new frontiers of research toward a deeper understanding of LMAs and is ideally suited to be compared with field or particle observations from spacecraft such as Kaguya (SELENE), Lunar Prospector or ARTEMIS. The ability to evaluate the implications for future lunar exploration as well as lunar science in general hinges on a better understanding of LMAs.This research has received funding from the European Commission's FP7 Program with the grant agreement EHEROES (project 284461, www.eheroes.eu). The simulations were conducted on the computational resources provided by the PRACE Tier-0 project 2013091928 (SuperMUC). This research was supported by the Swedish National Space Board

  3. M3 spectral analysis of lunar swirls and the link between optical maturation and surface hydroxyl formation at magnetic anomalies

    USGS Publications Warehouse

    Kramer, G.Y.; Besse, S.; Dhingra, D.; Nettles, J.; Klima, R.; Garrick-Bethell, I.; Clark, R.N.; Combe, J.-P.; Head, J. W.; Taylor, L.A.; Pieters, C.M.; Boardman, J.; McCord, T.B.

    2011-01-01

    all three focus regions support the hypothesis that the magnetic anomalies deflect solar wind ions away from the swirls and onto off-swirl surfaces. Nanophase iron (npFe0) is largely responsible for the spectral characteristics we attribute to space weathering and maturation, and is created by vaporization/deposition by micrometeorite impacts and sputtering/reduction by solar wind ions. On the swirls, the decreased proton flux slows the spectral effects of space weathering (relative to nonswirl regions) by limiting the npFe0 production mechanism almost exclusively to micrometeoroid impact vaporization/deposition. Immediately adjacent to the swirls, maturation is accelerated by the increased flux of protons deflected from the swirls. Copyright 2011 by the American Geophysical Union.

  4. Holonomy anomalies

    SciTech Connect

    Bagger, J.; Nemeschansky, D.; Yankielowicz, S.

    1985-05-01

    A new type of anomaly is discussed that afflicts certain non-linear sigma models with fermions. This anomaly is similar to the ordinary gauge and gravitational anomalies since it reflects a topological obstruction to the reparametrization invariance of the quantum effective action. Nonlinear sigma models are constructed based on homogeneous spaces G/H. Anomalies arising when the fermions are chiral are shown to be cancelled sometimes by Chern-Simons terms. Nonlinear sigma models are considered based on general Riemannian manifolds. 9 refs. (LEW)

  5. MATLAB-based algorithm to estimate depths of isolated thin dike-like sources using higher-order horizontal derivatives of magnetic anomalies.

    PubMed

    Ekinci, Yunus Levent

    2016-01-01

    This paper presents an easy-to-use open source computer algorithm (code) for estimating the depths of isolated single thin dike-like source bodies by using numerical second-, third-, and fourth-order horizontal derivatives computed from observed magnetic anomalies. The approach does not require a priori information and uses some filters of successive graticule spacings. The computed higher-order horizontal derivative datasets are used to solve nonlinear equations for depth determination. The solutions are independent from the magnetization and ambient field directions. The practical usability of the developed code, designed in MATLAB R2012b (MathWorks Inc.), was successfully examined using some synthetic simulations with and without noise. The algorithm was then used to estimate the depths of some ore bodies buried in different regions (USA, Sweden, and Canada). Real data tests clearly indicated that the obtained depths are in good agreement with those of previous studies and drilling information. Additionally, a state-of-the-art inversion scheme based on particle swarm optimization produced comparable results to those of the higher-order horizontal derivative analyses in both synthetic and real anomaly cases. Accordingly, the proposed code is verified to be useful in interpreting isolated single thin dike-like magnetized bodies and may be an alternative processing technique. The open source code can be easily modified and adapted to suit the benefits of other researchers.

  6. The Emerson Lake Body: A link between the Landers and Hector Mine earthquakes, southern California, as inferred from gravity and magnetic anomalies

    USGS Publications Warehouse

    Langenheim, V.E.; Jachens, R.C.

    2002-01-01

    Gravity and magnetic data indicate a mafic crustal heterogeneity that lies between the Hector Mine 16 October 1999 (Mw 7.1) and Landers 28 June 1992 (Mw 7.3) epicenters. The aftershocks and ruptures of these two events avoided the interior of the body. Two- and three-dimensional modeling of the potential-field anomalies shows that the source, here named the Emerson Lake body (ELB), extends to a depth of approximately 15 km. The source of the gravity and magnetic anomaly is most likely Jurassic diorite because exposures of these rocks coincide with both gravity and magnetic highs west of Emerson Lake. Seismic tomography also shows higher velocities within the region of the ELB. We propose that the ELB was an important influence on the rupture geometry of the Landers and Hector Mine ruptures and that the ELB may have played a role in transferring of stress from the Landers earthquake to the Hector Mine hypocenter. Seismicity before the Landers earthquake also tended to avoid the ELB, suggesting that the ELB affects how strain is distributed in this part of the Mojave Desert. Thus, faults within the body should have limited rupture sizes and lower seismic hazard than faults bounding or outside this mafic crustal heterogeneity.

  7. Manipulating Ce Valence in RE2Fe14B Tetragonal Compounds by La-Ce Co-doping: Resultant Crystallographic and Magnetic Anomaly.

    PubMed

    Jin, Jiaying; Zhang, Yujing; Bai, Guohua; Qian, Zeyu; Wu, Chen; Ma, Tianyu; Shen, Baogen; Yan, Mi

    2016-07-26

    Abundant and low-cost Ce has attracted considerable interest as a prospective alternative for those critically relied Nd/Pr/Dy/Tb in the 2:14:1-type permanent magnets. The (Nd, Ce)2Fe14B compound with inferior intrinsic magnetic properties to Nd2Fe14B, however, cannot provide an equivalent magnetic performance. Since Ce valence is sensitive to local steric environment, manipulating it towards the favorable trivalent state provides a way to enhance the magnetic properties. Here we report that such a desirable Ce valence can be induced by La-Ce co-doping into [(Pr, Nd)1-x(La, Ce)x]2.14Fe14B (0 ≤ x ≤ 0.5) compounds via strip casting. As verified by X-ray photoelectron spectroscopy results, Ce valence shifts towards the magnetically favorable Ce(3+) state in the composition range of x > 0.3, owing to the co-doping of large radius La(3+) into 2:14:1 phase lattice. As a result, both crystallographic and magnetic anomalies are observed in the same vicinity of x = 0.3, above which lattice parameters a and c, and saturation magnetization Ms increase simultaneously. Over the whole doping range, 2:14:1 tetragonal structure forms and keeps stable even at 1250 K. This finding may shed light on obtaining a favorable Ce valence via La-Ce co-doping, thus maintaining the intrinsic magnetic properties of 2:14:1-type permanent magnets.

  8. Manipulating Ce Valence in RE2Fe14B Tetragonal Compounds by La-Ce Co-doping: Resultant Crystallographic and Magnetic Anomaly

    PubMed Central

    Jin, Jiaying; Zhang, Yujing; Bai, Guohua; Qian, Zeyu; Wu, Chen; Ma, Tianyu; Shen, Baogen; Yan, Mi

    2016-01-01

    Abundant and low-cost Ce has attracted considerable interest as a prospective alternative for those critically relied Nd/Pr/Dy/Tb in the 2:14:1-type permanent magnets. The (Nd, Ce)2Fe14B compound with inferior intrinsic magnetic properties to Nd2Fe14B, however, cannot provide an equivalent magnetic performance. Since Ce valence is sensitive to local steric environment, manipulating it towards the favorable trivalent state provides a way to enhance the magnetic properties. Here we report that such a desirable Ce valence can be induced by La-Ce co-doping into [(Pr, Nd)1−x(La, Ce)x]2.14Fe14B (0 ≤ x ≤ 0.5) compounds via strip casting. As verified by X-ray photoelectron spectroscopy results, Ce valence shifts towards the magnetically favorable Ce3+ state in the composition range of x > 0.3, owing to the co-doping of large radius La3+ into 2:14:1 phase lattice. As a result, both crystallographic and magnetic anomalies are observed in the same vicinity of x = 0.3, above which lattice parameters a and c, and saturation magnetization Ms increase simultaneously. Over the whole doping range, 2:14:1 tetragonal structure forms and keeps stable even at 1250 K. This finding may shed light on obtaining a favorable Ce valence via La-Ce co-doping, thus maintaining the intrinsic magnetic properties of 2:14:1-type permanent magnets. PMID:27457408

  9. The reduction, verification and interpretation of MAGSAT magnetic data over Canada

    NASA Technical Reports Server (NTRS)

    Coles, R. L. (Principal Investigator); Haines, G. V.; Vanbeek, G. J.; Walker, J. K.; Newitt, L. R.; Nandi, A.

    1982-01-01

    Correlations between the MAGSAT scalar anomaly map produced at the Earth Physics ranch and other geophysical and geological data reveal relationships between high magnetic field and some metamorphic grade shields, as well as between low magnetic field and shield regions of lower metamorphic grade. An intriguing contrast exists between the broad low anomaly field over the Nasen-Gakkel Ridge (a spreading plate margin) and the high anomaly field over Iceland (part of a spreading margin). Both regions have high heat flow, and presumably thin magnetic crust. This indicates that Iceland is quite anomalous in its magnetic character, and possible similarities with the Alpha Ridge are suggested. Interesting correlations exist between MAGSAT anomalies around the North Atlantic, after reconstructing the fit of continents into a prerifting configuration. These correlations suggest that several orogenies in that region have not completely destroyed an ancient magnetization formed in high grade Precambrian rocks.

  10. A Preliminary, Full Spectrum, Magnetic Anomaly Grid of the United States with Improved Long Wavelengths for Studying Continental Dynamics: A Website for Distribution of Data

    USGS Publications Warehouse

    Ravat, D.; Finn, C.; Hill, P.; Kucks, R.; Phillips, J.; Blakely, R.; Bouligand, C.; Sabaka, T.; Elshayat, A.; Aref, A.; Elawadi, E.

    2009-01-01

    Under an initiative started by Thomas G. Hildenbrand of the U.S. Geological Survey, we have improved the long-wavelength (50-2,500 km) content of the regional magnetic anomaly compilation for the conterminous United States by utilizing a nearly homogeneous set of National Uranium Resource Evaluation (NURE) magnetic surveys flown from 1975 to 1981. The surveys were flown in quadrangles of 2 deg of longitude by 1 deg of latitude with east-west flight lines spaced 4.8 to 9.6 km apart, north-south tie lines variably spaced, and a nominal terrain clearance of 122 m. Many of the surveys used base-station magnetometers to remove external field variations.

  11. Untangling Magmatic Processes and Hydrothermal Alteration of in situ Superfast Spreading Ocean Crust at ODP/IODP Site 1256 with Fuzzy c-means Cluster Analysis of Rock Magnetic Properties

    NASA Astrophysics Data System (ADS)

    Dekkers, M. J.; Heslop, D.; Herrero-Bervera, E.; Acton, G.; Krasa, D.

    2014-12-01

    Ocean Drilling Program (ODP)/Integrated ODP (IODP) Hole 1256D (6.44.1' N, 91.56.1' W) on the Cocos Plate occurs in 15.2 Ma oceanic crust generated by superfast seafloor spreading. Presently, it is the only drill hole that has sampled all three oceanic crust layers in a tectonically undisturbed setting. Here we interpret down-hole trends in several rock-magnetic parameters with fuzzy c-means cluster analysis, a multivariate statistical technique. The parameters include the magnetization ratio, the coercivity ratio, the coercive force, the low-field susceptibility, and the Curie temperature. By their combined, multivariate, analysis the effects of magmatic and hydrothermal processes can be evaluated. The optimal number of clusters - a key point in the analysis because there is no a priori information on this - was determined through a combination of approaches: by calculation of several cluster validity indices, by testing for coherent cluster distributions on non-linear-map plots, and importantly by testing for stability of the cluster solution from all possible starting points. Here, we consider a solution robust if the cluster allocation is independent of the starting configuration. The five-cluster solution appeared to be robust. Three clusters are distinguished in the extrusive segment of the Hole that express increasing hydrothermal alteration of the lavas. The sheeted dike and gabbro portions are characterized by two clusters, both with higher coercivities than in lava samples. Extensive alteration, however, can obliterate magnetic property differences between lavas, dikes, and gabbros. The imprint of thermochemical alteration on the iron-titanium oxides is only partially related to the porosity of the rocks. All clusters display rock magnetic characteristics in line with a stable NRM. This implies that the entire sampled sequence of ocean crust can contribute to marine magnetic anomalies. Determination of the absolute paleointensity with thermal techniques is

  12. Origin of anomalies and phase competitions around magnetic transition temperature in Pr0.7Ca0.3MnO3

    NASA Astrophysics Data System (ADS)

    Shah, Matiullah; Nadeem, M.; Atif, M.

    2013-03-01

    A polycrystalline sample of Pr0.7Ca0.3MnO3 is synthesized by the conventional solid-state reaction method and the phase formation is confirmed by x-ray diffraction. In this work, we addressed the phase competition issues in the vicinity of magnetic transition temperature and also established its correlation with oxygen contents of domains, disorder effects and heterogeneity in the material. The appearance and disappearance of anomaly in the vicinity of TC (128 K) with magnetic field is discussed in terms of establishment of short- and long-range networks between Mn3+ and Mn4+. Switching behaviour of two competing phases is analysed qualitatively and quantitatively, using an equivalent circuit model and magnetization analysis. The issue of coexisting phases is further substantiated using a simple depression angle approach of impedance plane plots. variable range hopping is found to be a better model than polaronic for explaining the transport properties of both competing phases below the magnetic transition temperature, 128 K.

  13. Reliability of CHAMP Anomaly Continuations

    NASA Technical Reports Server (NTRS)

    vonFrese, Ralph R. B.; Kim, Hyung Rae; Taylor, Patrick T.; Asgharzadeh, Mohammad F.

    2003-01-01

    CHAMP is recording state-of-the-art magnetic and gravity field observations at altitudes ranging over roughly 300 - 550 km. However, anomaly continuation is severely limited by the non-uniqueness of the process and satellite anomaly errors. Indeed, our numerical anomaly simulations from satellite to airborne altitudes show that effective downward continuations of the CHAMP data are restricted to within approximately 50 km of the observation altitudes while upward continuations can be effective over a somewhat larger altitude range. The great unreliability of downward continuation requires that the satellite geopotential observations must be analyzed at satellite altitudes if the anomaly details are to be exploited most fully. Given current anomaly error levels, joint inversion of satellite and near- surface anomalies is the best approach for implementing satellite geopotential observations for subsurface studies. We demonstrate the power of this approach using a crustal model constrained by joint inversions of near-surface and satellite magnetic and gravity observations for Maude Rise, Antarctica, in the southwestern Indian Ocean. Our modeling suggests that the dominant satellite altitude magnetic anomalies are produced by crustal thickness variations and remanent magnetization of the normal polarity Cretaceous Quiet Zone.

  14. Anomalies in thermal expansion and heat capacity of TmB50 at low temperatures: magnetic phase transition and crystal electric field effect.

    PubMed

    Novikov, V V; Zhemoedov, N A; Mitroshenkov, N V; Matovnikov, A V

    2016-11-01

    We experimentally study the heat capacity and thermal expansion of thulium boride (TmB50) at temperatures of 2-300 K. The wide temperature range (2-180 K) of boride negative expansion was revealed. We found the anomalies in C(T) heat capacity temperature dependence, attributed to the Schottky contribution (i.e. the influence of the crystal electric field: CEF), as well as the magnetic phase transition. CEF-splitting of the f-levels of the Tm(3+) ion was described by the Schottky function of heat capacity with a quasi-quartet in the ground state. Excited multiplets are separated from the ground state by energy gaps δ1 = 100 K, and δ2 ≈ 350 K. The heat capacity maximum at Tmax ≈ 2.4 K may be attributed to the possible magnetic transition in TmB50. Other possible causes of the low-temperature maximum of C(T) dependence are the nonspherical surroundings of rare earth atoms due to the boron atoms in the crystal lattice of the boride and the emergence of two-level systems, as well as the splitting of the ground multiplet due to local magnetic fields of the neighboring ions of thulium. Anomalies in heat capacity are mapped with the thermal expansion features of boride. It is found that the TmB50 thermal expansion characteristic features are due to the influence of the CEF, as well as the asymmetry of the spatial arrangement of boron atoms around the rare earth atoms in the crystal lattice of RB50. The Grüneisen parameters, corresponding to the excitation of different multiplets of CEF-splitting, were determined. A satisfactory accordance between the experimental and estimated temperature dependencies of the boride thermal expansion coefficient was achieved.

  15. Congenital pancreatic anomalies, variants, and conditions.

    PubMed

    Alexander, Lauren F

    2012-05-01

    Understanding pancreatic development and the congenital anomalies and variants that result from alterations in normal development allows for better recognition of these anomalies at diagnostic imaging. This article reviews normal pancreatic embryology and anatomy, and the appearance of the more common developmental anomalies and ductal variants, with emphasis on computed tomography and magnetic resonance imaging. Common mimics of masses are also covered.

  16. Magnetic and magnetodielectric coupling anomalies in the Haldane spin-chain system Nd{sub 2}BaNiO{sub 5}

    SciTech Connect

    Basu, Tathamay Sampathkumaran, E. V.; Mohapatra, Niharika; Singh, Kiran

    2015-03-15

    We report the magnetic, heat-capacity, dielectric and magnetodielectric (MDE) behaviour of a Haldane spin-chain compound containing light rare-earth ion, Nd{sub 2}BaNiO{sub 5}, in detail, as a function of temperature (T) and magnetic field (H) down to 2 K. In addition to the well-known long range antiferromagnetic order setting in at (T{sub N} = ) 48 K as indicated in dc magnetization (M), we have observed another magnetic transition near 10 K; this transition appears to be of a glassy-type which vanishes with a marginal application of external magnetic field (even H = 100 Oe). There are corresponding anomalies in dielectric constant (ε′) as well with variation of T. The isothermal M(H) curves at 2 and 5 K reveal the existence of a magnetic-field induced transition around 90 kOe; the isothermal ε′(H) also tracks such a metamagnetic transition. These results illustrate the MDE coupling in this compound. Additionally, we observe a strong frequency dependence of a step in ε′(T) with this feature appearing around 25-30 K for the lowest frequency of 1 kHz, far below T{sub N}. This is attributed to interplay between crystal-field effect and exchange interaction between Nd and Ni, which establishes the sensitivity of dielectric measurements to detect such effects. Interestingly enough, the observed dispersions of the ε′(T) curves is essentially H-independent in the entire T-range of measurement, despite the existence of MDE coupling, which is in sharp contrast with other heavy rare-earth members in this series.

  17. Multiprobe in-situ measurement of magnetic field in a minefield via a distributed network of miniaturized low-power integrated sensor systems for detection of magnetic field anomalies

    NASA Astrophysics Data System (ADS)

    Javadi, Hamid H. S.; Bendrihem, David; Blaes, B.; Boykins, Kobe; Cardone, John; Cruzan, C.; Gibbs, J.; Goodman, W.; Lieneweg, U.; Michalik, H.; Narvaez, P.; Perrone, D.; Rademacher, Joel D.; Snare, R.; Spencer, Howard; Sue, Miles; Weese, J.

    1998-09-01

    Based on technologies developed for the Jet Propulsion Laboratory (JPL) Free-Flying-Magnetometer (FFM) concept, we propose to modify the present design of FFMs for detection of mines and arsenals with large magnetic signature. The result will be an integrated miniature sensor system capable of identifying local magnetic field anomaly caused by a magnetic dipole moment. Proposed integrated sensor system is in line with the JPL technology road-map for development of autonomous, intelligent, networked, integrated systems with a broad range of applications. In addition, advanced sensitive magnetic sensors (e.g., silicon micromachined magnetometer, laser pumped helium magnetometer) are being developed for future NASA space plasma probes. It is envisioned that a fleet of these Integrated Sensor Systems (ISS) units will be dispersed on a mine-field via an aerial vehicle (a low-flying airplane or helicopter). The number of such sensor systems in each fleet and the corresponding in-situ probe-grid cell size is based on the strength of magnetic anomaly of the target and ISS measurement resolution of magnetic field vector. After a specified time, ISS units will transmit the measured magnetic field and attitude data to an air-borne platform for further data processing. The cycle of data acquisition and transmission will be continued until batteries run out. Data analysis will allow a local deformation of the Earth's magnetic field vector by a magnetic dipole moment to be detected. Each ISS unit consists of miniaturized sensitive 3- axis magnetometer, high resolution analog-to-digital converter (ADC), Field Programmable Gate Array (FPGA)-based data subsystem, Li-batteries and power regulation circuitry, memory, S-band transmitter, single-patch antenna, and a sun angle sensor. ISS unit is packaged with non-magnetic components and the electronic design implements low-magnetic signature circuits. Care is undertaken to guarantee no corruption of magnetometer sensitivity as a result

  18. General mechanism and dynamics of the solar wind interaction with lunar magnetic anomalies from 3-D particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Deca, Jan; Divin, Andrey; Lembège, Bertrand; Horányi, Mihály; Markidis, Stefano; Lapenta, Giovanni

    2015-08-01

    We present a general model of the solar wind interaction with a dipolar lunar crustal magnetic anomaly (LMA) using three-dimensional full-kinetic and electromagnetic simulations. We confirm that LMAs may indeed be strong enough to stand off the solar wind from directly impacting the lunar surface, forming a so-called "minimagnetosphere," as suggested by spacecraft observations and theory. We show that the LMA configuration is driven by electron motion because its scale size is small with respect to the gyroradius of the solar wind ions. We identify a population of back-streaming ions, the deflection of magnetized electrons via the E × B drift motion, and the subsequent formation of a halo region of elevated density around the dipole source. Finally, it is shown that the presence and efficiency of the processes are heavily impacted by the upstream plasma conditions and, on their turn, influence the overall structure and evolution of the LMA system. Understanding the detailed physics of the solar wind interaction with LMAs, including magnetic shielding, particle dynamics and surface charging is vital to evaluate its implications for lunar exploration.

  19. Ocean floor spreading: olduvai and gilsa events in the matuyama epoch.

    PubMed

    Emilia, D A; Heinrichs, D F

    1969-12-05

    The magnetic anomaly usually associated with the Olduvai geomagnetic event (1.96 million years) should probably be associated with the Gilsa event (~ 1.65 million years). The Oldu-vai event can be correlated with a con-sistently appearing minor anomalycalled W. This reassignment gives near-ly uniform spreading rates for sections of the mid-ocean ridge system consid-ere( l here.

  20. Anomalous origin of the left circumflex coronary artery from the pulmonary artery. A very rare congenital anomaly in an adult patient diagnosed by cardiovascular magnetic resonance.

    PubMed

    Korosoglou, Grigorios; Ringwald, Gerd; Giannitsis, Evangelos; Katus, Hugo A

    2008-01-21

    Here we report for the first time on the diagnostic potential of cardiovascular magnetic resonance (CMR) to delineate the proximal course of an anomalous left circumflex coronary artery (LCX) originating from the right pulmonary artery in an adult patient with no other form of congenital heart disease. The patient was referred to our institution due to exertional chest discomfort. X-Ray coronary angiography showed a normal left anterior descending coronary artery (LAD) and right coronary artery (RCA), while the LCX was filled retrograde by collateral flow through the LAD and the RCA. The origin of the LCX was postulated to be the pulmonary artery, but the exact origin of the anomalous artery could not be depicted on conventional angiograms. CMR provided the unambiguous depiction of the origin of the anomalous LCX from the right pulmonary artery and the delineation of its proximal course in this case of a very rare coronary anomaly in adults.

  1. DOWN'S ANOMALY.

    ERIC Educational Resources Information Center

    PENROSE, L.S.; SMITH, G.F.

    BOTH CLINICAL AND PATHOLOGICAL ASPECTS AND MATHEMATICAL ELABORATIONS OF DOWN'S ANOMALY, KNOWN ALSO AS MONGOLISM, ARE PRESENTED IN THIS REFERENCE MANUAL FOR PROFESSIONAL PERSONNEL. INFORMATION PROVIDED CONCERNS (1) HISTORICAL STUDIES, (2) PHYSICAL SIGNS, (3) BONES AND MUSCLES, (4) MENTAL DEVELOPMENT, (5) DERMATOGLYPHS, (6) HEMATOLOGY, (7)…

  2. Evidence for True Polar Wander since mid-Cenozoic time: A Paleomagnetic Investigation of the Skewness of Magnetic Anomaly 12r (32 Ma) Between the Galapagos and Clarion Fracture Zones on the Pacific Plate

    NASA Astrophysics Data System (ADS)

    Horner-Johnson, B. C.; Gordon, R. G.

    2007-12-01

    In recent years, some researchers have asserted that there has been no motion of the Pacific hotspots relative to the spin axis since the age (ca. 47 Ma) of the elbow in the Hawaiian-Emperor chain (e.g., Tarduno et al. 2003). In contrast, the apparent polar wander of the Indo-Atlantic hotspots shows distinct motion of the hotspots relative to the spin axis over the same time interval (e.g., Morgan 1981; Besse and Courtillot 2002). If this latter shift is due to true polar wander, one would expect to see a similar shift of Pacific hotspots relative to the spin axis. Here we present critical new data and analyses to test these distinctly different hypotheses. Specifically, we present results of an investigation of the skewness of magnetic anomaly crossings of anomaly 12r between the Galapagos and Clipperton and between the Clipperton and Clarion fracture zones on the Pacific plate. We chose to focus on these adjacent regions for three reasons. First, numerical experiments showed that these crossings, of all those available from the Pacific plate, should contain the most information about the location of the 32 Ma paleomagnetic pole for the Pacific plate. Second, many of the available crossings are from vector aeromagnetic profiles, which have superior signal to noise ratios (Horner-Johnson and Gordon, 2003). Third, the rate of seafloor spreading recorded in these crossings exceeds the threshold (half rate of 50 mm/yr) above which no anomalous skewness occurs. Moreover, for the first time, we combine uncertainties in plate- hotspot rotations (Andrews et al. 2005) with paleomagnetic uncertainties to obtain the total uncertainties of our new paleomagnetic pole reconstructed into the Pacific hotspot frame of reference. The results show significant and unambiguous motion of Pacific hotspots relative to the spin axis since 32 Ma. Moreover, when the 32 Ma Pacific plate paleomagnetic pole is reconstructed into the Pacific hotspot reference frame, it is consistent with the

  3. The Wallula fault and tectonic framework of south-central Washington, as interpreted from magnetic and gravity anomalies

    SciTech Connect

    Blakely, Richard J.; Sherrod, Brian; Weaver, Craig; Wells, Ray E.; Rohay, Alan C.

    2013-11-13

    Magnetic and gravity data, collected in south-central Washington near the Yakima Fold and Thrust Belt (YFTB) are used to model upper crustal structure, the extent of the late Columbia River Basalt flow named the Ice Harbor member, the vertical conduits (dikes) that the Ice Harbor erupted from, and whether the dikes are offset or affected by faulting on the Wallula Fault zone.

  4. Seafloor spreading and microcontinent formation during Mesozoic breakup between Australia and Greater India

    NASA Astrophysics Data System (ADS)

    Williams, S.; Whittaker, J.; Müller, R.

    2012-12-01

    The Perth Abyssal Plain (PAP) formed at the nexus of rifting and breakup between three major continents within Gondwana - India, Australia and Antarctica. Oceanic crust within the PAP records the history of Mesozoic seafloor spreading as India moved away from Australia. However, despite the clear importance of the seafloor spreading history of the PAP in constraining the relative motions of these continents during the early stages of breakup, little attention has been paid to the PAP, and particularly its western flank largely due to a lack of new data in collected in this region. We present new observations to constrain the evolution of the PAP, collected during voyage ss2011/v06 of the Southern Surveyor in late 2011. The new data comprise magnetic anomaly profile data, swath bathymetry, and dredge samples collected from 7 sites. The most significant dredge results were obtained from the Batavia Knoll (BK) and Gulden Draak Knoll (GDK), two prominent bathymetric features located >1000 km west of the Australian continental margin. Previous tectonic reconstructions typically treat these bathymetric features as igneous plateaus emplaced on older oceanic crust. However, dredges carried out on the western flanks of each of these knolls recovered continental basement rocks, revealing that both knolls are continental fragments. Estimates of the depths to magnetic sources for shiptrack profiles across the knolls provide evidence for variations in sediment thickness within the knolls. We use forward modeling of shiptrack magnetic profiles combined with gravity anomalies derived from satellite altimetry to make first-order estimates of the extent and spatial variation in thickness of the continental crust. New magnetic anomaly profiles provide evidence for previously unidentified M-series anomalies in the western part of the Perth Abyssal Plain, east of the BK and GDK. These observations both support a reconstruction model in which the microcontinents rifted away from

  5. Aeromagnetic anomalies over faulted strata

    USGS Publications Warehouse

    Grauch, V.J.S.; Hudson, Mark R.

    2011-01-01

    High-resolution aeromagnetic surveys are now an industry standard and they commonly detect anomalies that are attributed to faults within sedimentary basins. However, detailed studies identifying geologic sources of magnetic anomalies in sedimentary environments are rare in the literature. Opportunities to study these sources have come from well-exposed sedimentary basins of the Rio Grande rift in New Mexico and Colorado. High-resolution aeromagnetic data from these areas reveal numerous, curvilinear, low-amplitude (2–15 nT at 100-m terrain clearance) anomalies that consistently correspond to intrasedimentary normal faults (Figure 1). Detailed geophysical and rock-property studies provide evidence for the magnetic sources at several exposures of these faults in the central Rio Grande rift (summarized in Grauch and Hudson, 2007, and Hudson et al., 2008). A key result is that the aeromagnetic anomalies arise from the juxtaposition of magnetically differing strata at the faults as opposed to chemical processes acting at the fault zone. The studies also provide (1) guidelines for understanding and estimating the geophysical parameters controlling aeromagnetic anomalies at faulted strata (Grauch and Hudson), and (2) observations on key geologic factors that are favorable for developing similar sedimentary sources of aeromagnetic anomalies elsewhere (Hudson et al.).

  6. Breakup and early seafloor spreading between India and Antarctica

    NASA Astrophysics Data System (ADS)

    Gaina, Carmen; Müller, R. Dietmar; Brown, Belinda; Ishihara, Takemi; Ivanov, Sergey

    2007-07-01

    We present a tectonic interpretation of the breakup and early seafloor spreading between India and Antarctica based on improved coverage of potential field and seismic data off the east Antarctic margin between the Gunnerus Ridge and the Bruce Rise. We have identified a series of ENE trending Mesozoic magnetic anomalies from chron M9o (~130.2 Ma) to M2o (~124.1 Ma) in the Enderby Basin, and M9o to M4o (~126.7 Ma) in the Princess Elizabeth Trough and Davis Sea Basin, indicating that India-Antarctica and India-Australia breakups were roughly contemporaneous. We present evidence for an abandoned spreading centre south of the Elan Bank microcontinent; the estimated timing of its extinction corresponds to the early surface expression of the Kerguelen Plume at the Southern Kerguelen Plateau around 120 Ma. We observe an increase in spreading rate from west to east, between chron M9 and M4 (38-54 mm yr-1), along the Antarctic margin and suggest the tectono-magmatic segmentation of oceanic crust has been influenced by inherited crustal structure, the kinematics of Gondwanaland breakup and the proximity to the Kerguelen hotspot. A high-amplitude, E-W oriented magnetic lineation named the Mac Robertson Coast Anomaly (MCA), coinciding with a landwards step-down in basement observed in seismic reflection data, is tentatively interpreted as the boundary between continental/transitional zone and oceanic crust. The exposure of lower crustal rocks along the coast suggests that this margin formed in a metamorphic core complex extension mode with a high strength ratio between upper and lower crust, which typically occurs above anomalously hot mantle. Together with the existence of the MCA zone this observation suggests that a mantle temperature anomaly predated the early surface outpouring/steady state magmatic production of the Kerguelen LIP. An alternative model suggests that the northward ridge jump was limited to the Elan Bank region, whereas seafloor spreading continued in the

  7. Molar volume, thermal expansion, and bulk modulus in liquid Fe-Ni alloys at 1 bar: Evidence for magnetic anomalies?

    NASA Astrophysics Data System (ADS)

    Nasch, P. M.; Manghnani, M. H.

    New experimental data on the molar volume Ω, thermal expansion coefficient α, and ultrasonic sound velocity vp in liquid Fe-Ni systems at temperatures between melting and 1975 K are reported. The molar volume and thermal expansion data were acquired using a penetrating γ radiation method; the sound velocity data were obtained by ultrasonic interferometry. In the temperature range of this study, the molar volume Ω increases and the sound velocity vp decreases, both linearly with temperature. The adiabatic bulk modulus KS ∝ v2p/Ωp of liquid Fe-Ni alloys is nearly independent of composition at Fe content greater than 65 wt%. The temperature derivative ∂K/∂T of both adiabatic and isothermal bulk modulus of pure liquid Fe decreases by approximately 50% upon being alloyed with 15 wt% Ni. The mixing behavior of thermodynamic and cohesive properties of liquid Fe-Ni is interpreted as resulting from the existence of disordered and localized magnetic states and correlations in the liquid state, i.e., well above the Curie temperature and extending from pure Fe into the Fe-Ni stability field. These magnetic contributions have strong mechanical effects on the structure in modifying the volume and elastic modulus by as much as 13% and 31%, respectively, in the case of pure liquid Fe. It is believed that the magnetic contribution, which is likely to be absent at core temperatures, should be removed from the measured 1-bar values of density and elastic moduli if these latter were to be used as precise anchoring points in high pressure-temperature EOS.

  8. Interpretation of CHAMP Magnetic Anomaly Data over the Pannonian Basin Region Using Lower Altitude Horizontal Gradient Data

    NASA Technical Reports Server (NTRS)

    Taylor, P. T.; Kis, K. I.; Wittmann, G.

    2013-01-01

    The ESA SWARM mission will have three earth orbiting magnetometer bearing satellites one in a high orbit and two side-by-side in lower orbits. These latter satellites will record a horizontal magnetic gradient. In order to determine how we can use these gradient measurements for interpretation of large geologic units we used ten years of CHAMP data to compute a horizontal gradient map over a section of southeastern Europe with our goal to interpret these data over the Pannonian Basin of Hungary.

  9. Preliminary aeromagnetic anomaly map of California

    USGS Publications Warehouse

    Roberts, Carter W.; Jachens, Rober C.

    1999-01-01

    The magnetization in crustal rocks is the vector sum of induced in minerals by the Earth’s present main field and the remanent magnetization of minerals susceptible to magnetization (chiefly magnetite) (Blakely, 1995). The direction of remanent magnetization acquired during the rock’s history can be highly variable. Crystalline rocks generally contain sufficient magnetic minerals to cause variations in the Earth’s magnetic field that can be mapped by aeromagnetic surveys. Sedimentary rocks are generally weakly magnetized and consequently have a small effect on the magnetic field: thus a magnetic anomaly map can be used to “see through” the sedimentary rock cover and can convey information on lithologic contrasts and structural trends related to the underlying crystalline basement (see Nettleton,1971; Blakely, 1995). The magnetic anomaly map (fig. 2) provides a synoptic view of major anomalies and contributes to our understanding of the tectonic development of California. Reference fields, that approximate the Earth’s main (core) field, have been subtracted from the recorded magnetic data. The resulting map of the total magnetic anomalies exhibits anomaly patterns related to the distribution of magnetized crustal rocks at depths shallower than the Curie point isotherm (the surface within the Earth beneath which temperatures are so high that rocks lose their magnetic properties). The magnetic anomaly map has been compiled from existing digital data. Data obtained from aeromagnetic surveys that were made at different times, spacings and elevations, were merged by analytical continuation of each set onto a common surface 305 m (1000 ft) above terrain. Digital data in this compatible form allows application of analytical techniques (Blakley, 1995) that can be used to enhance anomaly characteristics (e.g., wavelength and trends) and provide new interpretive information.

  10. Creating chiral anomalies

    NASA Astrophysics Data System (ADS)

    Bradlyn, Barry; Cano, Jennifer; Wang, Zhijun; Hirschberger, Max; Ong, N. Phuan; Bernevig, B. Andrei

    Materials with intrinsic Weyl points should present exotic magnetotransport phenomena due to spectral flow between Weyl nodes of opposite chirality - the so-called ``chiral anomaly''. However, to date, the most definitive transport data showing the presence of a chiral anomaly comes from Dirac (not Weyl) materials. These semimetals develop Weyl fermions only in the presence of an externally applied magnetic field, when the four-fold degeneracy is lifted. In this talk we examine Berry phase effects on transport due to the emergence of these field-induced Weyl point and (in some cases) line nodes. We pay particular attention to the differences between intrinsic and field-induced Weyl fermions, from the point of view of kinetic theory. Finally, we apply our analysis to a particular material relevant to current experiments performed at Princeton.

  11. Phanerozoic stratigraphy of Northwind Ridge, magnetic anomalies in the Canada Basin, and the geometry and timing of rifting in the Amerasia Basin, Arctic Ocean

    USGS Publications Warehouse

    Grantz, A.; Clark, D.L.; Phillips, R.L.; Srivastava, S.P.; Blome, C.D.; Gray, L.-B.; Haga, H.; Mamet, B.L.; McIntyre, D.J.; McNeil, D.H.; Mickey, M.B.; Mullen, M.W.; Murchey, B.I.; Ross, C.A.; Stevens, C.H.; Silberling, Norman J.; Wall, J.H.; Willard, D.A.

    1998-01-01

    Cores from Northwind Ridge, a high-standing continental fragment in the Chukchi borderland of the oceanic Amerasia basin, Arctic Ocean, contain representatives of every Phanerozoic system except the Silurian and Devonian systems. Cambrian and Ordovician shallow-water marine carbonates in Northwind Ridge are similar to basement rocks beneath the Sverdrup basin of the Canadian Arctic Archipelago. Upper Mississippian(?) to Permian shelf carbonate and spicularite and Triassic turbidite and shelf lutite resemble coeval strata in the Sverdrup basin and the western Arctic Alaska basin (Hanna trough). These resemblances indicate that Triassic and older strata in southern Northwind Ridge were attached to both Arctic Canada and Arctic Alaska prior to the rifting that created the Amerasia basin. Late Jurassic marine lutite in Northwind Ridge was structurally isolated from coeval strata in the Sverdrup and Arctic Alaska basins by rift shoulder and grabens, and is interpreted to be a riftogenic deposit. This lutite may be the oldest deposit in the Canada basin. A cape of late Cenomanian or Turonian rhyodacite air-fall ash that lacks terrigenous material shows that Northwind Ridge was structurally isolated from the adjacent continental margins by earliest Late Cretaceous time. Closing Amerasia basin by conjoining seafloor magnetic anomalies beneath the Canada basin or by uniting the pre-Jurassic strata of Northwind Ridge with kindred sections in the Sverdrup basin and Hanna trough yield simular tectonic reconstructions. Together with the orientation and age of rift-marine structures, these data suggest that: 1) prior to opening of the Amerasia basin, both northern Alaska and continental ridges of the Chukchi borderland were part of North America, 2) the extension that created the Amerasia basin formed rift-margin graben beginning in Early Jurassic time and new oceanic crust probably beginning in Late Jurassic or early Neocomian time. Reconstruction of the Amerasia basin on the

  12. Congenital anomalies

    PubMed Central

    Kunisaki, Shaun M.

    2012-01-01

    Over the past decade, amniotic fluid-derived stem cells have emerged as a novel, experimental approach for the treatment of a wide variety of congenital anomalies diagnosed either in utero or postnatally. There are a number of unique properties of amniotic fluid stem cells that have allowed it to become a major research focus. These include the relative ease of accessing amniotic fluid cells in a minimally invasive fashion by amniocentesis as well as the relatively rich population of progenitor cells obtained from a small aliquot of fluid. Mesenchymal stem cells, c-kit positive stem cells, as well as induced pluripotent stem cells have all been derived from human amniotic fluid in recent years. This article gives a pediatric surgeon’s perspective on amniotic fluid stem cell therapy for the management of congenital anomalies. The current status in the use of amniotic fluid-derived stem cells, particularly as they relate as substrates in tissue engineering-based applications, is described in various animal models. A roadmap for further study and eventual clinical application is also proposed. PMID:22986340

  13. Quantum Mechanical Simulation and X-Ray Scattering Applied to Pressure-Induced Invar Anomaly in Magnetic Iron Alloy

    NASA Astrophysics Data System (ADS)

    Winterrose, Michael L.

    The Invar effect has remained at the forefront of materials research since Charles-Edouard Guillaume discovered the vanishing thermal expansion of Fe-Ni alloys in 1897. More recently, a pressure-induced Invar effect was discovered in Fe-Ni alloys, and the relationship between classical and pressure-induced Invar phenomena has added complexity to the century-old struggle to comprehend the microscopic origins of Invar behavior. In this thesis I present our recent discovery of pressure-induced Invar behavior in Pd3Fe with the ordered L12 structure. Nuclear forward scattering measurements show that the ferromagnetic ground state in Pd3Fe is destabilized with pressure, collapsing around 10GPa (V/V 0=0.96) to a low-spin magnetic state. From high-pressure synchrotron x-ray diffraction measurements we find a large volume collapse at ambient temperature to accompany the collapse of ferromagnetism. After the volume collapse there is a significant increase in the bulk modulus. Using nuclear resonant inelastic x-ray scattering to study the 57Fe phonon partial density of states (PDOS) at high pressures, we find the pressure-induced magnetic transition to cause an anomalous relative softening of the average phonon frequency. Heating our sample to 650K in a furnace at a pressure of 7GPa, synchrotron x-ray diffraction measurements reveal negligible thermal expansion from 300 to 523 K, demonstrating pressure-induced Invar behavior in Pd3Fe. Density functional theory calculations identify a ferromagnetic ground state in Pd3Fe with large moments at the Fe sites. These calculations show that the application of pressure counteracts the band-filling effect of Pd. By tuning the position of the top of the 3d band with respect to the Fermi level, pressure-induced Invar behavior resembles classical Invar behavior that is controlled by chemical composition. This insight marks the first step towards a unification of our understanding of classical and pressure-induced Invar behavior. Pressure

  14. Curie-point depths estimated from fractal spectral analyses of magnetic anomalies in the western United States and northeast Pacific Oecan

    NASA Astrophysics Data System (ADS)

    Wang, J.; Li, C.

    2011-12-01

    We estimate Curie-point depths (Zb) of the western United States and northeast Pacific Ocean by analyzing radially averaged amplitude spectra of magnetic anomalies based on a fractal magnetization model. The amplitude spectrum of source magnetization is proportional to the wavenumber (k) raised to a fractal exponent (-β). We first test whether long-wavelength components are captured appropriately by using variable overlapping windows ranging in sizes from 75 × 75 km2 to 200 × 200 km2. For each sliding window, the amplitude spectrum is pre-multiplied with the factor k-β prior to computation. We then use the centroid method (Tanaka et al., 1999) to calculate Zb. We find that when the window size approaches 200 × 200 km2 the resolution of estimated Zb is too low to reveal important geological features. For our study, fractal exponents larger than 0.6 will result in overcorrection. Considering the difficulty of simultaneous inversion of the depths to the top and centroid of magnetic sources (Zt and Z0 respectively) and β, we fix β = 0.5 for the whole study area. Note that β here is defined for amplitude spectrum, which is equivalent to 1 for power spectrum of 2D magnetic sources. Our results show that the estimated Curie depths range from 4 km to 40 km. The average Zb in the northern part of the northeast Pacific Ocean is about 14 km below the sea level, and almost the same depths are found in the junction of the active and ancient Cascade arcs and remanent track of Yellowstone hotspot. Subduction beneath the North American plate and consequent magmatism can account for small Zb in the above mentioned volcanic arc regions. The Mendocino Triple Junction separates the northeast Pacific into northern (mainly consisting of the Explorer, Juan de Fuca and Gorda plates) and southern parts. Both the Zb and the thickness of magnetic layer in the southern part are larger than those in the northern part. This contrast is due to the fact that the Pacific plate to the south

  15. Mexican-American Cooperative Program at the Cerro Prieto geothermal field: Analysis of the Nuevo Leon magnetic anomaly and its possible relation to the Cerro Prieto magmatic-hydrothermal system

    NASA Astrophysics Data System (ADS)

    Goldstein, N. E.; Wilt, M. J.; Corrigan, D. J.

    1982-10-01

    The broad dipolar magnetic anomaly whose positive peak is centered near Ejido Nuevo Leon, some 5 km east of the Cerro Prieto I Power Plant, has long been suspended to have a genetic relationship to the thermal source of the Cerro Prieto geothermal system. This suspicion was reinforced after several deep geothermal wells, drilled to depths of 3 to 3.5 km over the anomaly, intersected an apparent dike-sill complex consisting mainly of diabase but with minor rhyodacite. A detailed fit of the observed magnetic field to a computer model indicates that the source may be approximated by a tabular block 4 by 6 km in area, 3.7 km in depth, 2.3 km thick, and dipping slightly to the north. Mafic dike chips from one well, NL-1, were analyzed by means of electron microprobe analyses which showed them to contain a titanomagnetite that is paramagnetic at in-situ temperature conditions. As the dike mineralogy does not account for the magnetic anomaly, the magnetic source is believed to be a deeper, magnetite-rich assemblage of periodotite-gabbro plutons.

  16. Magnetization of the oceanic crust - Thermoremanent magnetization of chemical remanent magnetization?

    NASA Technical Reports Server (NTRS)

    Raymond, C. A.; Labrecque, J. L.

    1987-01-01

    A model was proposed in which chemical remanent magnetization (CRM) acquired within the first 20 Ma of crustal evolution may account for 80 percent of the bulk natural remanent magnetization (NRM) of older basalts. The CRM of the crust is acquired as the original thermoremanent magnetization (TRM) is lost through low temperature alteration. The CRM intensity and direction are controlled by the post-emplacement polarity history. This model explains several independent observations concerning the magnetization of the oceanic crust. The model accounts for amplitude and skewness dicrepancies observed in both the intermediate wavelength satellite field and the short wavelength sea surface magnetic anomaly pattern. It also explains the decay of magnetization away from the spreading axis, and the enhanced magnetization of the Cretaceous Quiet Zones while predicting other systematic variations with age in the bulk magnetization of the oceanic crust. The model also explains discrepancies in the anomaly skewness parameter observed for anomalies of Cretaceous age. Further studies indicate varying rates of TRM decay in very young crust which depicts the advance of low temperature alteration through the magnetized layer.

  17. Extensive air shower Monte Carlo modeling at the ground and aircraft flight altitude in the South Atlantic Magnetic Anomaly and comparison with neutron measurements

    NASA Astrophysics Data System (ADS)

    Pazianotto, M. T.; Cortés-Giraldo, M. A.; Federico, C. A.; Hubert, G.; Gonçalez, O. L.; Quesada, J. M.; Carlson, B. V.

    2017-02-01

    Modeling cosmic-ray-induced particle fluxes in the atmosphere is very important for developing many applications in aeronautics, space weather and on ground experimental arrangements. There is a lack of measurements and modeling at flight altitude and on ground in the South Atlantic Magnetic Anomaly. In this work we have developed an application based on the Geant4 toolkit called gPartAt that is aimed at the analysis of extensive air shower particle spectra. Another application has been developed using the MCNPX code with the same approach in order to evaluate the models and nuclear data libraries used in each application. Moreover, measurements were performed to determine the ambient dose equivalent rate of neutrons at flight altitude in different regions and dates in the Brazilian airspace; these results were also compared with the simulations. The results from simulations of the neutron spectra at ground level were also compared to data from a neutron spectrometer in operation since February 2015 at the Pico dos Dias Observatory in Brazil, at 1864 m above sea level, as part of a collaboration between the Institute for Advanced Studies (IEAv) and the French Aerospace Lab (ONERA). This measuring station is being operated with support from the National Astrophysics Laboratory (LNA). The modeling approaches were also compared to the AtmoRad computational platform, QARM, EXPACS codes and with measurements of the neutron spectrum taken in 2009 at the Pico dos Dias Observatory.

  18. Analyzing the Broken Ridge area of the Indian Ocean using magnetic and gravity anomaly maps and geoid undulation and bathymetry data

    NASA Technical Reports Server (NTRS)

    Lazarewicz, A. R.; Sailor, R. V. (Principal Investigator)

    1982-01-01

    A higher resolution anomaly map of the Broken Ridge area (2 degree dipole spacing) was produced and reduced to the pole using quiet time data for this area. The map was compared with equally scaled maps of gravity anomaly, geoid undulation, and bathymetry. The ESMAP results were compared with a NASA MAGSAT map derived by averaging data in two-degree bins. A survey simulation was developed to model the accuracy of MAGSAT anomaly maps as a function of satellite altitude, instrument noise level, external noise model, and crustal anomaly field model. A preliminary analysis of the geophysical structure of Broken Ridge is presented and unresolved questions are listed.

  19. Ages and magnetic structures of the South China Sea constrained by deep tow magnetic surveys and IODP Expedition 349

    NASA Astrophysics Data System (ADS)

    Li, Chun-Feng; Xu, Xing; Lin, Jian; Sun, Zhen; Zhu, Jian; Yao, Yongjian; Zhao, Xixi; Liu, Qingsong; Kulhanek, Denise K.; Wang, Jian; Song, Taoran; Zhao, Junfeng; Qiu, Ning; Guan, Yongxian; Zhou, Zhiyuan; Williams, Trevor; Bao, Rui; Briais, Anne; Brown, Elizabeth A.; Chen, Yifeng; Clift, Peter D.; Colwell, Frederick S.; Dadd, Kelsie A.; Ding, Weiwei; Almeida, Iván. Hernández; Huang, Xiao-Long; Hyun, Sangmin; Jiang, Tao; Koppers, Anthony A. P.; Li, Qianyu; Liu, Chuanlian; Liu, Zhifei; Nagai, Renata H.; Peleo-Alampay, Alyssa; Su, Xin; Tejada, Maria Luisa G.; Trinh, Hai Son; Yeh, Yi-Ching; Zhang, Chuanlun; Zhang, Fan; Zhang, Guo-Liang

    2014-12-01

    analyses of deep tow magnetic anomalies and International Ocean Discovery Program Expedition 349 cores show that initial seafloor spreading started around 33 Ma in the northeastern South China Sea (SCS), but varied slightly by 1-2 Myr along the northern continent-ocean boundary (COB). A southward ridge jump of ˜20 km occurred around 23.6 Ma in the East Subbasin; this timing also slightly varied along the ridge and was coeval to the onset of seafloor spreading in the Southwest Subbasin, which propagated for about 400 km southwestward from ˜23.6 to ˜21.5 Ma. The terminal age of seafloor spreading is ˜15 Ma in the East Subbasin and ˜16 Ma in the Southwest Subbasin. The full spreading rate in the East Subbasin varied largely from ˜20 to ˜80 km/Myr, but mostly decreased with time except for the period between ˜26.0 Ma and the ridge jump (˜23.6 Ma), within which the rate was the fastest at ˜70 km/Myr on average. The spreading rates are not correlated, in most cases, to magnetic anomaly amplitudes that reflect basement magnetization contrasts. Shipboard magnetic measurements reveal at least one magnetic reversal in the top 100 m of basaltic layers, in addition to large vertical intensity variations. These complexities are caused by late-stage lava flows that are magnetized in a different polarity from the primary basaltic layer emplaced during the main phase of crustal accretion. Deep tow magnetic modeling also reveals this smearing in basement magnetizations by incorporating a contamination coefficient of 0.5, which partly alleviates the problem of assuming a magnetic blocking model of constant thickness and uniform magnetization. The primary contribution to magnetic anomalies of the SCS is not in the top 100 m of the igneous basement.

  20. Unique Aeromagnetic-radar Ice-sounding Survey over the West Antarctic Ice Sheet Allows Three Dimensional Definition of Sources of Magnetic Anomalies Caused by Subglacial Volcanic Sources at the Bed of the Ice

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.; Casertz; Soar Teams

    2011-12-01

    The West Antarctic Ice Sheet (WAIS) flows through the volcanically active West Antarctic Rift System (WARS). The aeromagnetic method has proven the most useful geophysical tool for studying subglacial volcanic rocks beneath the WAIS since early surveys in the 1950s. The Central West Antarctica (CWA) aerogeophysical survey covering ~354,000 km2 (about the area of Nevada and California combined) over the WAIS, consisting of a 5-km line-spaced, orthogonal set of aeromagnetic, radar ice-sounding and aerogravity measurements, is a unique Antarctic data set. This 1990-97 survey (CASERTZ and SOAR), still provides invaluable information on subglacial volcanic rocks, particularly when combined with widely spaced older aeromagnetic flight lines over a much greater area. These combined survey data indicate numerous high-amplitude (100->1000 nT), 5-50 km width, shallow-source, magnetic anomalies over a very extensive area (>1.2 x 106 km2) mostly resulting from subglacial volcanic eruptions. I interpreted the anomalies sampled in the CWA survey as defining ~1000 "volcanic centers" requiring high remanent normal magnetizations in the present field direction. About 400 of these anomaly sources (conservatively selected) are correlated with bed topography. The tops of >80% of these anomaly sources have <200 m relief at the bed of the WAIS. They appear modified by moving ice, requiring a younger age than the WAIS (~25 Ma). The 5 km by 5 km orthogonal flight line survey obviated aliasing of the magnetic and radar ice sounding data, because it is approximately equivalent to the flight elevation above the ice (1 km) surface plus the ice thickness (2-3 km); it reveals the magnetic anomalies and the tops of volcanic sources at its bed in three dimensions. Models (2 1/2 D) fit to a number of the magnetic anomalies, whose sources are at the bed of the ice sheet are constrained by topography measured by the radar ice sounding. Volcanoes in the WARS are <34 Ma, but at least four are active

  1. Normal-state magnetic properties and their correlation with Tc suppression and the resistivity anomalies in the (La1-xPrx)1.85Sr0.15CuO4 series

    NASA Astrophysics Data System (ADS)

    Musa, J. E.; García, S.; Rothier de Amaral, M.; Salim de Amorim, H.; Giordanengo, B.; Baggio-Saitovitch, E. M.; Pagliuso, P. J. G.; Rettori, C.; Yelon, W. B.; Malik, S. K.

    1999-04-01

    We have investigated the normal-state anomalies observed in the magnetic and transport properties of the (La1-xPrx)1.85Sr0.15CuO4 system with 0⩽x⩽0.5. The resistivity curves showed an increasing deviation from linearity below ˜100 K. This behavior is properly accounted by a logarithmic term, whose coefficient C linearly increases with x. The normal-state magnetic susceptibility measurements evidenced a departure from the Pr3+ Curie-Weiss dependence in the same temperature range for which the resistivity anomaly occurs. A comprehensive picture of the conduction mechanism is presented in terms of a Kondo-like scattering of the mobile holes by the spin fluctuations.

  2. Concurrent observations at the magnetic equator of small-scale irregularities and large-scale depletions associated with equatorial spread F

    NASA Astrophysics Data System (ADS)

    Hickey, Dustin A.; Martinis, Carlos R.; Rodrigues, Fabiano S.; Varney, Roger H.; Milla, Marco A.; Nicolls, Michael J.; Strømme, Anja; Arratia, Juan F.

    2015-12-01

    In 2014 an all-sky imager (ASI) and an Advanced Modular Incoherent Scatter Radar consisting of 14 panels (AMISR-14) system were installed at the Jicamarca Radio Observatory. The ASI measures airglow depletions associated with large-scale equatorial spread F irregularities (10-500 km), while AMISR-14 detects small-scale irregularities (0.34 m). This study presents simultaneous observations of equatorial spread F (ESF) irregularities at 50-200 km scale sizes using the all-sky imager, at 3 m scale sizes using the JULIA (Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere) radar, and at 0.34 m scales using the AMISR-14 radar. We compare data from the three instruments on the night of 20-21 August 2014 by locating the radar scattering volume in the optical images. During this night no topside plumes were observed, and we only compare with bottomside ESF. AMISR-14 had five beams perpendicular to the magnetic field covering ~200 km in the east-west direction at 250 km altitude. Comparing the radar data with zenith ASI measurements, we found that most of the echoes occur on the western wall of the depletions with fewer echoes observed the eastern wall and center, contrary to previous comparisons of topside plumes that showed most of the echoes in the center of depleted regions. We attribute these differences to the occurrence of irregularities produced at submeter scales by the lower hybrid drift instability. Comparisons of the ASI observations with JULIA images show similar results to those found in the AMISR-14 and ASI comparison.

  3. Gauge anomalies, gravitational anomalies, and superstrings

    SciTech Connect

    Bardeen, W.A.

    1985-08-01

    The structure of gauge and gravitational anomalies will be reviewed. The impact of these anomalies on the construction, consistency, and application of the new superstring theories will be discussed. 25 refs.

  4. Interaction between the nascent Reunion hotspot and the dying Mascarene spreading centre

    NASA Astrophysics Data System (ADS)

    Bissessur, P. D.; Dyment, J.; Deplus, C.; Patriat, P.

    2010-12-01

    The Reunion hotspot is one of the best examples of a classical mantle plume which reached the lithosphere and formed continental flood basalt, the Deccan trapps, around 65 Ma, and then made an almost continuous trail as the Indian and African plates moved northward, building the Laccadives, Maldives, and Chagos Ridges between 60 Ma and 35 Ma on the fast Indian plate, then the Nazareth Bank after 35 Ma, Mauritius Island between 10 Ma and 8 Ma, and La Reunion Island since 2 Ma on the slower African plate (e.g. Duncan, 1988). Conversely, the Mascarene Basin is characterized by conjugate magnetic anomalies 34 to 27 separated by an extinct spreading centre. Seafloor spreading was therefore active between about 85 Ma, when Africa (including Madagascar) and India (including Seychelles) separated, up to 59 Ma, when the Carlsberg Ridge was fully open between Africa (including Madagascar and Seychelles) and India. The coincidence between the inception of the Reunion hotspot in the Indian lithosphere and the transfer of seafloor spreading from the Mascarene basin to the Carlsberg Ridge suggests that the latter is a consequence of the former. Recent cruises, including cruise Forever of R/V L’Atalante in 2006, have focused on the south-eastern part of the basin, around Reunion Island. Swath bathymetric data and dredges have revealed that the five gravity undulations located south of Reunion Island toward the fossil ridge are volcanic ridges lying on oceanic lithosphere dated 68-64 Ma by magnetic anomalies 30 and 29. The satellite gravity data reveal possible other similar undulations further south, on the north-eastern flank of a fossil spreading centre dated by anomaly 28 (64-62 Ma). Conversely, no such undulation is observed on the intermediate area, where a more recent fossil spreading centre is dated by anomaly 27 (62-60 Ma). If validated by future swath bathymetric data, this observation means that the volcanic ridges were built before anomaly 27, possibly between 65 Ma

  5. Method of Mapping Anomalies in Homogenous Material

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

    2016-01-01

    An electrical conductor and antenna are positioned in a fixed relationship to one another. Relative lateral movement is generated between the electrical conductor and a homogenous material while maintaining the electrical conductor at a fixed distance from the homogenous material. The antenna supplies a time-varying magnetic field that causes the electrical conductor to resonate and generate harmonic electric and magnetic field responses. Disruptions in at least one of the electric and magnetic field responses during this lateral movement are indicative of a lateral location of a subsurface anomaly. Next, relative out-of-plane movement is generated between the electrical conductor and the homogenous material in the vicinity of the anomaly's lateral location. Disruptions in at least one of the electric and magnetic field responses during this out-of-plane movement are indicative of a depth location of the subsurface anomaly. A recording of the disruptions provides a mapping of the anomaly.

  6. The elliptic anomaly

    NASA Technical Reports Server (NTRS)

    Janin, G.; Bond, V. R.

    1980-01-01

    An independent variable different from the time for elliptic orbit integration is used. Such a time transformation provides an analytical step-size regulation along the orbit. An intermediate anomaly (an anomaly intermediate between the eccentric and the true anomaly) is suggested for optimum performances. A particular case of an intermediate anomaly (the elliptic anomaly) is defined, and its relation with the other anomalies is developed.

  7. Electromagnetic Particle-in-Cell Simulations of the Solar Wind Interaction with Lunar Magnetic Anomalies: Interaction Mechanisms Under Varying Solar Wind Conditions.

    NASA Astrophysics Data System (ADS)

    Deca, Jan; Divin, Andrey; Lapenta, Giovanni; Lembège, Bertrand; Markidis, Stefano; Horányi, Mihály

    2015-04-01

    We present three-dimensional fully kinetic and electromagnetic simulations of the solar wind interaction with lunar crustal magnetic anomalies (LMAs). Using the implicit particle-in-cell code iPic3D, we confirm that LMAs may indeed be strong enough to stand off the solar wind from directly impacting the lunar surface forming a mini-magnetosphere, as suggested by spacecraft observations and theory. In contrast to earlier MHD and hybrid simulations, the fully kinetic nature of iPic3D allows to investigate the space charge effects and in particular the electron dynamics dominating the near-surface lunar plasma environment. We describe the general picture of the interaction of a dipole model centered just below the lunar surface under various solar wind and plasma conditions, and focus afterwards on the ion and electron kinetic behavior of the system. It is shown that the configuration is dominated by electron motion, because the LMA scale size is small with respect to the gyroradius of the solar wind ions. We identify a population of backstreaming ions, the deflection of magnetized electrons via the ExB-drift motion and the subsequent formation of a halo region of elevated density around the dipole source. Finally, it is shown that the presence and efficiency of the latter mechanisms are heavily impacted by the upstream plasma conditions and, on their turn, influence the overall structure and evolution of the LMA system. Our work opens new frontiers of research toward a deeper understanding of LMAs and is ideally suited to be compared with field or particle observations from spacecraft such as Kaguya (SELENE), Lunar Prospector or ARTEMIS. The ability to evaluate the implications for future lunar exploration as well as lunar science in general hinges on a better understanding of LMAs. This research has received funding from the European Commission's FP7 Program with the grant agreement SWIFF (project 2633430, swiff.eu) and EHEROES (project 284461, www.eheroes.eu). The

  8. Equivalent magnetization over the World's Ocean

    NASA Astrophysics Data System (ADS)

    Dyment, J.; Choi, Y.; Hamoudi, M.; Erwan, T.; Lesur, V.

    2014-12-01

    As a by-product of our recent work to build a candidate model over the oceans for the World Digital Magnetic Anomaly Map (WDMAM) version 2, we derived global distributions of the equivalent magnetization in oceanic domains. In a first step, we use classic point source forward modeling on a spherical Earth to build a forward model of the marine magnetic anomalies at sea-surface. We estimate magnetization vectors using the age map of the ocean floor, the relative plate motions, the apparent polar wander path for Africa, and a geomagnetic reversal time scale. As magnetized source geometry, we assume 1 km-thick layer bearing a 10 A/m magnetization following the topography of the oceanic basement as defined by the bathymetry and sedimentary thickness. Adding a present-day geomagnetic field model allows the computation of our initial magnetic anomaly model. In a second step, we adjust this model to the existing marine magnetic anomaly data, in order to make it consistent with these data. To do so, we extract synthetic magnetic along the ship tracks for which real data are available and we compare quantitatively the measured and computed anomalies on 100, 200 or 400 km-long sliding windows (depending the spreading rate). Among the possible comparison criteria, we discard the maximal range - too dependent on local values - and the correlation and coherency - the geographical adjustment between model and data being not accurate enough - to favor the standard deviation around the mean value. The ratio between the standard deviations of data and model on each sliding window represent an estimate of the magnetization ratio causing the anomalies, which we interpolate to adjust the initial magnetic anomaly model to the data and therefore compute a final model to be included in our WDMAM candidate over the oceanic regions lacking data. The above ratio, after division by the magnetization of 10 A/m used in the model, represents an estimate of the equivalent magnetization under the

  9. Four Decades of Hyperfine Anomalies

    NASA Astrophysics Data System (ADS)

    Gustavsson, Martin G. H.; Mårtensson-Pendrill, Ann-Marie

    Isotopic differences in the distribution of nuclear charge and magnetization give rise to "hyperfine structure anomalies" which were observed already in the 1950s. More recently, the distribution of nuclear magnetization has been found to complicate the interpretation of the measured hyperfine splittings in highly charged hydrogen-like ions. In this paper, results of numerical calculations for a few hydrogen-like systems (133Cs, 165Ho, 185,187Re and 209Bi) of current experimental interest are presented in terms of moments of the nuclear charge and magnetization distribution, thereby displaying directly the sensitivity and emphasizing the need for a better understanding of nuclear wavefunctions. In addition, we also present results of many-body perturbation theory calculations for Cs hyperfine anomalies, in connection with experiments planned at ISOLDE.

  10. Magnetic Anomalies of the Ocean

    DTIC Science & Technology

    1983-10-01

    contract N0014.82-AK-099 9 L This document hdl en cpE’ for publi lele ime cud a1"l distribution i$ Unliitd This research was sponsored by ihe Earth ... Sciences branch of the Office or Naval Research. gflC FILE COPY 84 03 13 293 Octohebr 1981 * * s’j Table of Contents Page Introduction...where ZZ is the E mode impedance of the Earth , a co,’.’.-x functiun of frequency that is dependent in ideal circumstances only on the distribution of

  11. Structure of the Hat Creek graben region: Implications for the structure of the Hat Creek graben and transfer of right-lateral shear from the Walker Lane north of Lassen Peak, northern California, from gravity and magnetic anomalies

    USGS Publications Warehouse

    Langenheim, Victoria; Jachens, Robert C.; Clynne, Michael A.; Muffler, L. J. Patrick

    2016-01-01

    Interpretation of magnetic and new gravity data provides constraints on the geometry of the Hat Creek Fault, the amount of right-lateral offset in the area between Mt. Shasta and Lassen Peak, and confirmation of the influence of pre-existing structure on Quaternary faulting. Neogene volcanic rocks coincide with short-wavelength magnetic anomalies of both normal and reversed polarity, whereas a markedly smoother magnetic field occurs over the Klamath Mountains and its Paleogene cover. Although the magnetic field over the Neogene volcanic rocks is complex, the Hat Creek Fault, which is one of the most prominent normal faults in the region and forms the eastern margin of the Hat Creek Valley, is marked by the eastern edge of a north-trending magnetic and gravity high 20-30 km long. Modeling of these anomalies indicates that the fault is a steeply dipping (~75-85°) structure. The spatial relationship of the fault as modeled by the potential-field data, the youngest strand of the fault, and relocated seismicity suggests that deformation continues to step westward across the valley, consistent with a component of right-lateral slip in an extensional environment. Filtered aeromagnetic data highlight a concealed magnetic body of Mesozoic or older age north of Hat Creek Valley. The body’s northwest margin strikes northeast and is linear over a distance of ~40 km. Within the resolution of the aeromagnetic data (1-2 km), we discern no right-lateral offset of this body. Furthermore, Quaternary faults change strike or appear to end, as if to avoid this concealed magnetic body and to pass along its southeast edge, suggesting that pre-existing crustal structure influenced younger faulting, as previously proposed based on gravity data.

  12. Estimation of hydrothermal deposits location from magnetization distribution and magnetic properties in the North Fiji Basin

    NASA Astrophysics Data System (ADS)

    Choi, S.; Kim, C.; Park, C.; Kim, H.

    2013-12-01

    The North Fiji Basin is belong to one of the youngest basins of back-arc basins in the southwest Pacific (from 12 Ma ago). We performed the marine magnetic and the bathymetry survey in the North Fiji Basin for finding the submarine hydrothermal deposits in April 2012. We acquired magnetic and bathymetry datasets by using Multi-Beam Echo Sounder EM120 (Kongsberg Co.) and Overhouser Proton Magnetometer SeaSPY (Marine Magnetics Co.). We conducted the data processing to obtain detailed seabed topography, magnetic anomaly, reduce to the pole(RTP), analytic signal and magnetization. The study areas composed of the two areas(KF-1(longitude : 173.5 ~ 173.7 and latitude : -16.2 ~ -16.5) and KF-3(longitude : 173.4 ~ 173.6 and latitude : -18.7 ~ -19.1)) in Central Spreading Ridge(CSR) and one area(KF-2(longitude : 173.7 ~ 174 and latitude : -16.8 ~ -17.2)) in Triple Junction(TJ). The seabed topography of KF-1 existed thin horst in two grabens that trends NW-SE direction. The magnetic properties of KF-1 showed high magnetic anomalies in center part and magnetic lineament structure of trending E-W direction. In the magnetization distribution of KF-1, the low magnetization zone matches well with a strong analytic signal in the northeastern part. KF-2 area has TJ. The seabed topography formed like Y-shape and showed a high feature in the center of TJ. The magnetic properties of KF-2 displayed high magnetic anomalies in N-S spreading ridge center and northwestern part. In the magnetization distribution of KF-2, the low magnetization zone matches well with a strong analytic signal in the northeastern part. The seabed topography of KF-3 presented a flat and high topography like dome structure at center axis and some seamounts scattered around the axis. The magnetic properties of KF-3 showed high magnetic anomalies in N-S spreading ridge center part. In the magnetization of KF-2, the low magnetization zone mismatches to strong analytic signal in this area. The difference of KF-3

  13. Geopotential field anomalies and regional tectonic features

    NASA Astrophysics Data System (ADS)

    Mandea, Mioara; Korte, Monika

    2016-07-01

    Maps of both gravity and magnetic field anomalies offer crucial information about physical properties of the Earth's crust and upper mantle, required in understanding geological settings and tectonic structures. Density and magnetization represent independent rock properties and thus provide complementary information on compositional and structural changes. Two regions are considered: southern Africa (encompassing South Africa, Namibia and Botswana) and Germany. This twofold choice is motivated firstly by the fact that these regions represent rather diverse geological and geophysical conditions (old Archean crust with strong magnetic anomalies in southern Africa, and much younger, weakly magnetized crust in central Europe) and secondly by our intimate knowledge of the magnetic vector ground data from these two regions. We take also advantage of the recently developed satellite potential field models and compare magnetic and gravity gradient anomalies of some 200 km resolution. Comparing short and long wavelength anomalies and the correlation of rather large scale magnetic and gravity anomalies, and relating them to known lithospheric structures, we generally find a better agreement over the southern African region than the German territory. This probably indicates a stronger concordance between near-surface and deeper structures in the former area, which can be perceived to agree with a thicker lithosphere.

  14. Chiral anomalies and differential geometry

    SciTech Connect

    Zumino, B.

    1983-10-01

    Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references. (WHK)

  15. Tuning magnetofluidic spreading in microchannels

    NASA Astrophysics Data System (ADS)

    Wang, Zhaomeng; Varma, V. B.; Wang, Z. P.; Ramanujan, R. V.

    2015-12-01

    Magnetofluidic spreading (MFS) is a phenomenon in which a uniform magnetic field is used to induce spreading of a ferrofluid core cladded by diamagnetic fluidic streams in a three-stream channel. Applications of MFS include micromixing, cell sorting and novel microfluidic lab-on-a-chip design. However, the relative importance of the parameters which govern MFS is still unclear, leading to non-optimal control of MFS. Hence, in this work, the effect of various key parameters on MFS was experimentally and numerically studied. Our multi-physics model, which combines magnetic and fluidic analysis, showed excellent agreement between theory and experiment. It was found that spreading was mainly due to cross-sectional convection induced by magnetic forces, and can be enhanced by tuning various parameters. Smaller flow rate ratio, higher magnetic field, higher core stream or lower cladding stream dynamic viscosity, and larger magnetic particle size can increase MFS. These results can be used to tune magnetofluidic spreading in microchannels.

  16. Lymphatic Anomalies Registry

    ClinicalTrials.gov

    2016-07-26

    Lymphatic Malformation; Generalized Lymphatic Anomaly (GLA); Central Conducting Lymphatic Anomaly; CLOVES Syndrome; Gorham-Stout Disease ("Disappearing Bone Disease"); Blue Rubber Bleb Nevus Syndrome; Kaposiform Lymphangiomatosis; Kaposiform Hemangioendothelioma/Tufted Angioma; Klippel-Trenaunay Syndrome; Lymphangiomatosis

  17. Ebstein anomaly: a review.

    PubMed

    Galea, Joseph; Ellul, Sarah; Schembri, Aaron; Schembri-Wismayer, Pierre; Calleja-Agius, Jean

    2014-01-01

    Cardiac congenital abnormalities are a leading cause in neonatal mortality occurring in up to 1 in 200 of live births. Ebstein anomaly, also known as Kassamali anomaly, accounts for 1 percent of all congenital cardiac anomalies. This congenital abnormality involves malformation of the tricuspid valve and of the right ventricle. In this review, the causes of the anomaly are outlined and the pathophysiology is discussed, with a focus on the symptoms, management, and treatments available to date.

  18. High Occurrence of Aberrant Lymph Node Spread on Magnetic Resonance Lymphography in Prostate Cancer Patients With a Biochemical Recurrence After Radical Prostatectomy

    SciTech Connect

    Meijer, Hanneke J.M.; Lin, Emile N. van; Debats, Oscar A.; Witjes, J. Alfred; Span, Paul N.; Kaanders, Johannes H.A.M.; Barentsz, Jelle O.

    2012-03-15

    Purpose: To investigate the pattern of lymph node spread in prostate cancer patients with a biochemical recurrence after radical prostatectomy, eligible for salvage radiotherapy; and to determine whether the clinical target volume (CTV) for elective pelvic irradiation in the primary setting can be applied in the salvage setting for patients with (a high risk of) lymph node metastases. Methods and Materials: The charts of 47 prostate cancer patients with PSA recurrence after prostatectomy who had positive lymph nodes on magnetic resonance lymphography (MRL) were reviewed. Positive lymph nodes were assigned to a lymph node region according to the guidelines of the Radiation Therapy Oncology Group (RTOG) for delineation of the CTV for pelvic irradiation (RTOG-CTV). We defined four lymph node regions for positive nodes outside this RTOG-CTV: the para-aortal, proximal common iliac, pararectal, and paravesical regions. They were referred to as aberrant lymph node regions. For each patient, clinical and pathologic features were recorded, and their association with aberrant lymph drainage was investigated. The distribution of positive lymph nodes was analyzed separately for patients with a prostate-specific antigen (PSA) <1.0 ng/mL. Results: MRL detected positive aberrant lymph nodes in 37 patients (79%). In 20 patients (43%) a positive lymph node was found in the pararectal region. Higher PSA at the time of MRL was associated with the presence of positive lymph nodes in the para-aortic region (2.49 vs. 0.82 ng/mL; p = 0.007) and in the proximal common iliac region (1.95 vs. 0.59 ng/mL; p = 0.009). There were 18 patients with a PSA <1.0 ng/mL. Ten of these patients (61%) had at least one aberrant positive lymph node. Conclusion: Seventy-nine percent of the PSA-recurrent patients had at least one aberrant positive lymph node. Application of the standard RTOG-CTV for pelvic irradiation in the salvage setting therefore seems to be inappropriate.

  19. Spacecraft Environmental Anomalies Handbook

    DTIC Science & Technology

    1989-08-01

    engineering solutions for mitigating the effects of environmental anomalies have been developed. Among the causes o, spacecraft anomalies are surface...have been discovered after years of investig!:tion, and engineering solutions for mitigating the effccts of environmental anomalies have been developed...23 * 6.4.3 Fauth Tolerant Solutions .............................................................................. 23 6.4.4. Methods

  20. South Atlantic Anomaly

    Atmospheric Science Data Center

    2013-04-19

    article title:  The South Atlantic Anomaly     View larger GIF image The South Atlantic Anomaly (SAA) . Even before the cover opened, the Multi-angle Imaging ... Atlantic Anomaly location:  Atlantic Ocean Global Images First Light Images region:  Before the ...

  1. Examination of Global Seismic Tomography Images and Sea-Surface Magnetic Field Anomaly Profiles in the West Philippine Basin for the Large Clockwise Rotation of the Philippine Sea Plate during the Last 55 Million Years

    NASA Astrophysics Data System (ADS)

    Choe, H.; Lee, S. M.

    2014-12-01

    The Philippine Sea Plate is thought to have undergone a 90° clockwise rotation during the last 55 million years. However, evidences for such an argument are rather circumstantial. For instance, paleomagnetic measurements for the large rotation are derived largely from Halmahera, Indonesia which is quite close to the plate boundary. It is thus possible that this region may have undergone local deformation separate from the main parts of the Philippine Sea Plate. In this study, we examine the global seismic tomography images of the mantle beneath the Philippine Sea Plate and the marine magnetic field anomaly data at the sea surface from the West Philippine Basin to see whether they agree with the presumed motion of the Philippine Sea Plate. Our comparison between the plate reconstruction and global tomography suggests that the rotation of Philippine Sea Plate may not have been continuous but instead experienced a temporal break at around 32 Ma. The exact nature of this pause is uncertain, but it may be related to a sudden change in the configuration of subduction systems. A detail comparison with recent results from IODP Legs 350 and 351 is therefore necessary, including a search for a change in the depositional style of basin sediment. We also examined the detailed the shape of magnetic anomalies (such as skewness) and compare them with the previous model by allowing the magnetization to have direction corresponding to that during the opening of the West Philippine Basin. At this moment, it is too early to tell if the sudden change at around 32 Ma or other inferred breaks can be seen in the magnetic profiles as well.

  2. Crustal Magnetization and Magnetic Petrology in Basalts - What Can We Learn from Scientific Drillings?

    NASA Astrophysics Data System (ADS)

    Kontny, A. M.

    2014-12-01

    Rock magnetic and magneto-mineralogical data from scientific drillings contribute to our understanding of the growth history and tectonic evolution of volcanic structures and allows for an improved interpretation of magnetic anomaly data. Such data are not only important for the magnetic structure of volcanic buildings and spreading ridges on Earth but may also provide basic data for the interpretation of extraterrestrial magnetic anomalies like on Mars. Crustal magnetization of basalts is well studied since decades and in general, the amplitude of magnetic anomalies is mainly related to the induced and remanent magnetization. Direct measurements of the magnetic field and measurements of magnetic properties of oceanic and continental crust have indicated that the crustal magnetization is very complex and depends on different factors like e.g. magma composition, cooling rate, age and hydrothermal alteration. Generally a high oxygen fugacity (above the NNO buffer) and a low Ti/(Ti+Fe) ratio of the basaltic melt are suggested as a precondition for high concentration of magnetic minerals and therefore high primary TRM. High temperature subsolidus reactions and hydrothermal alteration as e.g. observed in the strongly magnetic basalts from the Stardalur drill core, Iceland, seems to increase NRM intensity and magnetic susceptibility due to creation of small, secondary magnetite (Vahle et al. 2007). Probably the increase occurred after the extinction of the hydrothermal system because active high-temperature (>150 °C) geothermal areas like the Krafla caldera, NE-Iceland, often show distinct magnetic lows in aeromagnetic anomaly maps suggesting a destruction of magnetic minerals by hydrothermal activity (Oliva-Urcia et al. 2011). The destruction explains the significant magnetization loss, which is seen in many local magnetic anomaly lows within the oceanic crust and volcanic islands like Iceland or Hawaii. Borehole and core magnetic susceptibility measurements in

  3. Nolen-Schiffer anomaly

    SciTech Connect

    Pieper, S.C.; Wiringa, R.B.

    1995-08-01

    The Argonne v{sub 18} potential contains a detailed treatment of the pp, pn and nn electromagnetic potential, including Coulomb, vacuum polarization, Darwin Foldy and magnetic moment terms, all with suitable form factors and was fit to pp and pn data using the appropriate nuclear masses. In addition, it contains a nuclear charge-symmetry breaking (CSB) term adjusted to reproduce the difference in the experimental pp and nn scattering lengths. We have used these potential terms to compute differences in the binding energies of mirror isospin-1/2 nuclei (Nolen-Schiffer [NS] anomaly). Variational Monte Carlo calculations for the {sup 3}He-{sup 3}H system and cluster variational Monte Carlo for the {sup 15}O-{sup 15}N and {sup 17}F-{sup 17}O systems were made. In the first case, the best variational wave function for the A = 3 nuclei was used. However, because our {sup 16}O wave function does not reproduce accurately the {sup 16}O rms radius, to which the NS anomaly is very sensitive, we adjusted the A = 15 and A = 17 wave functions to reproduce the experimental density profiles. Our computed energy differences for these three systems are 0.757 {plus_minus} .001, 3.544 {plus_minus} .018 and 3.458 {plus_minus} .040 MeV respectively, which are to be compared with the experimental differences of 0.764, 3.537, and 3.544 MeV. Most of the theoretical uncertainties are due to uncertainties in the experimental rms radii. The nuclear CSB potential contributes 0.066, 0.188, and 0.090 MeV to these totals. We also attempted calculations for A = 39 and A = 41. However, in these cases, the experimental uncertainties in the rms radius make it impossible to extract useful information about the contribution of the nuclear CSB potential.

  4. Spreading behaviour of the Pacific-Farallon ridge system since 83 Ma

    NASA Astrophysics Data System (ADS)

    Rowan, Christopher J.; Rowley, David B.

    2014-06-01

    We present improved rotations, complete with uncertainties, for the Pacific-Farallon Ridge (PFR) between geomagnetic chrons 34y (83 Ma) and 10y (28.28 Ma). Despite substantial shortening since ˜55 Ma, this ridge system and its remnants (e.g. the East Pacific Rise) have produced as much as 45 per cent of all oceanic lithosphere created since the Late Cretaceous, but reconstructions face the twin challenges of extensive subduction of Farallon crust-which precludes reconstruction by fitting conjugate magnetic anomaly and fracture zone (FZ) traces-and asymmetric spreading behaviour for at least the past 51 Myr. We have calculated best-fit `half'-angle stage rotations between nine geomagnetic chron boundaries (34y, 33y, 29o, 24.3o, 20o, 18.2o, 17.1y, 13y and 10y) using combined anomaly and FZ data from both the northern and southern Pacific Plate. For rotations younger than chron 24.3o, estimates for spreading asymmetry, derived using anomaly picks from yet-to-be subducted Farallon/Nazca crust in the south Pacific, allow full stage rotations to be calculated. Between 50 and 83 Ma, where no direct constraints on spreading asymmetry are possible, a `best-fit' full stage rotation was calculated based on the net Nazca:Pacific spreading asymmetry (Pacific spreading fraction fPAC = 0.44) over the past 50 Myr, with conservative lower and upper bounds, based on variability in the degree of spreading asymmetry over periods of <15 Myr, assuming fPACs of 0.5 and 0.36, respectively. Synthetic flowlines generated from our new stage rotation produce a better match to Pacific FZ trends than previously published rotations. With the exception of the chron 18o-20o rotation, the six stage poles for rotations between chrons 33y and 13y (74-33 Ma) all cluster tightly at 60-75°E, 60-68°N, consistent with the relatively constant trend of the major Pacific FZs. This stability spans at least one episode of Farallon Plate fragmentation caused by subduction of PFR segments beneath the Americas

  5. Spreading Rate versus Magma Supply in the Region of Mid-Atlantic Ridge at 16.5° N

    NASA Astrophysics Data System (ADS)

    Palmiotto, C.; Schouten, H.; Smith, D. K.; Cann, J. R.; Dick, H. J.; Parnell-Turner, R. E.

    2013-12-01

    The region of Mid-Atlantic Ridge (MAR) at 16.5° N is a slow spreading center characterized by several detachment faults and oceanic core complexes. This area is ideal to study the relationship between the formation and the evolution of detachment faults, the role of magma supply during detachment faulting, and its effect on the magnetization of the crust at a slow-spreading center. In May-June 2013, during cruise KN210-05 on RV Knorr, we acquired multibeam bathymetry and sea surface magnetic anomaly data to understand the spreading history of a section of the MAR near 16.5° N. Multibeam data acquired using a SeaBeam 3012 system show that the ridge axis can be divided into a northern segment, characterized by a 4500-m deep axial valley, and a southern segment, which is characterized by a robust and continuous axial volcanic ridge which reaches to 3200 m water depth. Both segments are bordered to the west by active detachment faults. Magnetic data were acquired with a Marine Magnetics SeaSPY system, and inverted for crustal magnetization. The inversion assumes a constant thickness source layer of 0.5 km whose upper bound is bathymetry. Isochrons were identified from the magnetization map. We found that spreading rate is symmetric, and have calculated a total spreading rate in this area of ~24 km/Ma for the last 4 Ma. The central anomaly (Brunhes, 0-0.78 Ma) in the southern segment, however, has only half the predicted width of ~ 20 km and is located exclusively east of the axis. No Brunhes normal magnetization is recorded in the rift valley floor west of the axis, which is the hanging wall of the detachment. This observation confirms predictions from ';asymmetric' spreading at oceanic core complexes where slip along long-lived detachment faults take up extension on one (western) side and magmatic accretion occurs exclusively to the other (eastern) of the axis; the hanging wall, bounded by detachment fault and axis, should be as old as the core complex and its

  6. Analysis of spacecraft anomalies

    NASA Technical Reports Server (NTRS)

    Bloomquist, C. E.; Graham, W. C.

    1976-01-01

    The anomalies from 316 spacecraft covering the entire U.S. space program were analyzed to determine if there were any experimental or technological programs which could be implemented to remove the anomalies from future space activity. Thirty specific categories of anomalies were found to cover nearly 85 percent of all observed anomalies. Thirteen experiments were defined to deal with 17 of these categories; nine additional experiments were identified to deal with other classes of observed and anticipated anomalies. Preliminary analyses indicate that all 22 experimental programs are both technically feasible and economically viable.

  7. Magnetization of the oceanic crust: TRM or CRM?

    NASA Technical Reports Server (NTRS)

    Raymond, C. A.; Labrecque, J. L.

    1987-01-01

    A model was proposed in which chemical remanent magnetization (CRM) acquired within the first 20 Ma of crustal evolution may account for 80% of the bulk natural remanent magnetization (NRM) of older basalts. The CRM of the crust is acquired as the original thermoremanent magnetization (TRM) is lost through low temperature alteration. The CRM intensity and direction are controlled by the post-emplacement polarity history. This model explains several independent observations concerning the magnetization of the oceanic crust. The model accounts for amplitude and skewness discrepancies observed in both the intermediate wavelength satellite field and the short wavelength sea surface magnetic anomaly pattern. It also explains the decay of magnetization away from the spreading axis, and the enhanced magnetization of the Cretaceous Quiet Zones while predicting other systematic variations with age in the bulk magnetization of the oceanic crust. The model also explains discrepancies in the anomaly skewness parameter observed for anomalies of Cretaceous age. Further studies indicate varying rates of TRM decay in very young crust which depicts the advance of low temperature alteration through the magnetized layer.

  8. Magnetic investigations

    SciTech Connect

    Bath, G.D.; Jahren, C.E.; Rosenbaum, J.G.; Baldwin, M.J.

    1983-12-31

    Air and ground magnetic anomalies in the Climax stock area of the NTS help define the gross configuration of the stock and detailed configuration of magnetized rocks at the Boundary and Tippinip faults that border the stock. Magnetizations of geologic units were evaluated by measurements of magnetic properties of drill core, minimum estimates of magnetizations from ground magnetic anomalies for near surface rocks, and comparisons of measured anomalies with anomalies computed by a three-dimensional forward program. Alluvial deposits and most sedimentary rocks are nonmagnetic, but drill core measurements reveal large and irregular changes in magnetization for some quartzites and marbles. The magnetizations of quartz monzonite and granodiorite near the stock surface are weak, about 0.15 A/m, and increase at a rate of 0.00196 A/m/m to 1.55 A/m, at depths greater than 700 m (2300 ft). The volcanic rocks of the area are weakly magnetized. Aeromagnetic anomalies 850 m (2800 ft) above the stock are explained by a model consisting of five vertical prisms. Prisms 1, 2, and 3 represent the near surface outline of the stock, prism 4 is one of the models developed by Whitehill (1973), and prism 5 is modified from the model developed by Allingham and Zietz (1962). Most of the anomaly comes from unsampled and strongly-magnetized deep sources that could be either granite or metamorphosed sedimentary rocks. 48 refs., 23 figs., 3 tabs.

  9. Tectonics and magmatism of ultraslow spreading ridges

    NASA Astrophysics Data System (ADS)

    Dubinin, E. P.; Kokhan, A. V.; Sushchevskaya, N. M.

    2013-05-01

    The tectonics, structure-forming processes, and magmatism in rift zones of ultraslow spreading ridges are exemplified in the Reykjanes, Kolbeinsey, Mohns, Knipovich, Gakkel, and Southwest Indian ridges. The thermal state of the mantle, the thickness of the brittle lithospheric layer, and spreading obliquety are the most important factors that control the structural pattern of rift zones. For the Reykjanes and Kolbeinsey ridges, the following are crucial factors: variations in the crust thickness; relationships between the thicknesses of its brittle and ductile layers; width of the rift zone; increase in intensity of magma supply approaching the Iceland thermal anomaly; and spreading obliquety. For the Knipovich Ridge, these are its localization in the transitional zone between the Gakkel and Mohns ridges under conditions of shear and tensile stresses and multiple rearrangements of spreading; nonorthogonal spreading; and structural and compositional barrier of thick continental lithosphere at the Barents Sea shelf and Spitsbergen. The Mohns Ridge is characterized by oblique spreading under conditions of a thick cold lithosphere and narrow stable rift zone. The Gakkel and the Southwest Indian ridges are distinguished by the lowest spreading rate under the settings of the along-strike variations in heating of the mantle and of a variable spreading geometry. The intensity of endogenic structure-forming varies along the strike of the ridges. In addition to the prevalence of tectonic factors in the formation of the topography, magmatism and metamorphism locally play an important role.

  10. Taussig-Bing Anomaly

    PubMed Central

    Konstantinov, Igor E.

    2009-01-01

    Taussig-Bing anomaly is a rare congenital heart malformation that was first described in 1949 by Helen B. Taussig (1898–1986) and Richard J. Bing (1909–). Although substantial improvement has since been achieved in surgical results of the repair of the anomaly, management of the Taussig-Bing anomaly remains challenging. A history of the original description of the anomaly, the life stories of the individuals who first described it, and the current outcomes of its surgical management are reviewed herein. PMID:20069085

  11. Characterization of potential sources of magnetic anomalies within the crust in a tectonically active region: Amphibolites and migmatites from Potrillo Maar, New Mexico

    NASA Technical Reports Server (NTRS)

    Spear, F. S.; Padovanni, E.

    1985-01-01

    The purpose was to characterize the oxide mineralogy and petrology of samples collected from Potrillo Maar, New Mexico with the goal of explaining the magnetic anamoly that is observed over this region from remote sensing. Potrillo Maar is a diatreme that has brought rocks from all depths in the crust to the surface almost instantaneously. The samples are therefore thought to be representative of the crust as it exists today below this portion of the Rio Grande Rift. It is generally believed that oxide minerals (magnetite, hematite, etc.) are responsible for the magnetic signature of the crust. The samples from Portillo Maar therefore offer a unique opportunity to examine the magnetic mineralogy of the entire crust. The results indicate that the magnetic anamoly observed over Rio Grande Rift may be consequence of the tectonic activity that caused mylonitization of the rocks and allowed the infiltration of oxidizing fluids.

  12. Hot Flow Anomalies at Venus

    NASA Technical Reports Server (NTRS)

    Collinson, G. A.; Sibeck, David Gary; Boardsen, Scott A.; Moore, Tom; Barabash, S.; Masters, A.; Shane, N.; Slavin, J.A.; Coates, A.J.; Zhang, T. L.; Sarantos, M.

    2012-01-01

    We present a multi-instrument study of a hot flow anomaly (HFA) observed by the Venus Express spacecraft in the Venusian foreshock, on 22 March 2008, incorporating both Venus Express Magnetometer and Analyzer of Space Plasmas and Energetic Atoms (ASPERA) plasma observations. Centered on an interplanetary magnetic field discontinuity with inward convective motional electric fields on both sides, with a decreased core field strength, ion observations consistent with a flow deflection, and bounded by compressive heated edges, the properties of this event are consistent with those of HFAs observed at other planets within the solar system.

  13. Competing Orders and Anomalies

    PubMed Central

    Moon, Eun-Gook

    2016-01-01

    A conservation law is one of the most fundamental properties in nature, but a certain class of conservation “laws” could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the ’t Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed. PMID:27499184

  14. Competing Orders and Anomalies

    NASA Astrophysics Data System (ADS)

    Moon, Eun-Gook

    2016-08-01

    A conservation law is one of the most fundamental properties in nature, but a certain class of conservation “laws” could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the ’t Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed.

  15. Competing Orders and Anomalies.

    PubMed

    Moon, Eun-Gook

    2016-08-08

    A conservation law is one of the most fundamental properties in nature, but a certain class of conservation "laws" could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the 't Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed.

  16. Characterization of the in situ magnetic architecture of oceanic crust (Hess Deep) using near-source vector magnetic data

    NASA Astrophysics Data System (ADS)

    Tominaga, Masako; Tivey, Maurice A.; MacLeod, Christopher J.; Morris, Antony; Lissenberg, C. Johan; Shillington, Donna J.; Ferrini, Vicki

    2016-06-01

    Marine magnetic anomalies are a powerful tool for detecting geomagnetic polarity reversals, lithological boundaries, topographic contrasts, and alteration fronts in the oceanic lithosphere. Our aim here is to detect lithological contacts in fast-spreading lower crust and shallow mantle by characterizing magnetic anomalies and investigating their origins. We conducted a high-resolution, near-bottom, vector magnetic survey of crust exposed in the Hess Deep "tectonic window" using the remotely operated vehicle (ROV) Isis during RRS James Cook cruise JC21 in 2008. Hess Deep is located at the western tip of the propagating rift of the Cocos-Nazca plate boundary near the East Pacific Rise (EPR) (2°15'N, 101°30'W). ROV Isis collected high-resolution bathymetry and near-bottom magnetic data as well as seafloor samples to determine the in situ lithostratigraphy and internal structure of a section of EPR lower crust and mantle exposed on the steep (~20°dipping) south facing slope just north of the Hess Deep nadir. Ten magnetic profiles were collected up the slope using a three-axis fluxgate magnetometer mounted on ROV Isis. We develop and extend the vertical magnetic profile (VMP) approach of Tivey (1996) by incorporating, for the first time, a three-dimensional vector analysis, leading to what we here termed as "vector vertical magnetic profiling" approach. We calculate the source magnetization distribution, the deviation from two dimensionality, and the strike of magnetic boundaries using both the total field Fourier-transform inversion approach and a modified differential vector magnetic analysis. Overall, coherent, long-wavelength total field anomalies are present with a strong magnetization contrast between the upper and lower parts of the slope. The total field anomalies indicate a coherently magnetized source at depth. The upper part of the slope is weakly magnetized and magnetic structure follows the underlying slope morphology, including a "bench" and lobe

  17. Low-temperature anomaly of the magnetization in alloys (Pr,Dy, M)2(Fe,Co)14B ( M = Gd, Sm, Nd)

    NASA Astrophysics Data System (ADS)

    Kablov, E. N.; Ospennikova, O. G.; Rezchikova, I. I.; Valeev, R. A.; Cherednichenko, I. V.; Kunitsyna, E. I.; Morgunov, R. B.; Piskorskii, V. P.

    2016-03-01

    It has been found that temperature dependences of the saturation magnetization of sintered hard magnetic (Pr,Dy, M)2(Fe,Co)14B ( M = Gd, Sm, Nd) alloys demonstrate an increase at a temperature lower than a critical temperature (150 K for Sm and Nd and 70 K for Gd). An additive of copper does not influence the critical temperature. It has been assumed that there is a low-temperature phase in which cobalt is replaced with boron that diffuses from the (Pr,Dy,Gd)(Fe,Co)4B phase to the near-surface region of grains of the main magnetic (Pr,Dy,Gd)2(Fe,Co)14B phase.

  18. The anomaly data base of screwworm information

    NASA Technical Reports Server (NTRS)

    Giddings, L. E.

    1976-01-01

    Standard statistical processing of anomaly data in the screwworm eradication data system is possible from data compiled on magnetic tapes with the Univac 1108 computer. The format and organization of the data in the data base, which is also available on dedicated disc storage, are described.

  19. Magnetization of lower oceanic crust and upper mantle

    NASA Astrophysics Data System (ADS)

    Kikawa, E.

    2004-05-01

    The location of the magnetized rocks of the oceanic crust that are responsible for sea-floor spreading magnetic anomalies has been a long-standing problem in geophysics. The recognition of these anomalies was a key stone in the development of the theory of plate tectonics. Our present concept of oceanic crustal magnetization is much more complex than the original, uniformly magnetized model of Vine-Matthews-Morley Hypothesis. Magnetic inversion studies indicated that the upper oceanic extrusive layer (Layer 2A of 0.5km thick) was the only magnetic layer and that it was not necessary to postulate any contribution from deeper parts of oceanic crust. Direct measurements of the magnetic properties of the rocks recovered from the sea floor, however, have shown that the magnetization of Layer 2A, together with the observations that this layer could record geomagnetic field reversals within a vertical section, is insufficient to give the required size of observed magnetic anomalies and that some contribution from lower intrusive rocks is necessary. Magnetization of oceanic intrusive rocks were observed to be reasonably high enough to contribute to sea-floor spreading magnetic anomalies, but were considered somewhat equivocal until late 1980Os, in part because studies had been conducted on unoriented dredged and ophiolite samples and on intermittent DSDP/ODP cores. Since ODP Leg 118 that cored and recovered continuous 500m of oceanic intrusive layer at Site 735B, Southwest Indian Ridge with an extremely high recovery of 87 percent, there have been several ODP Legs (legs 147, 153, 176, 179 and 209) that were devoted to drilling gabbroic rocks and peridotites. In terms of the magnetization intensities, all of the results obtained from these ODP Legs were supportive of the model that a significant contribution must come from gabbros and peridotites and the source of the lineated magnetic anomalies must reside in most of the oceanic crust as well as crust-mantle boundary

  20. Tuning magnetic and electronic properties of (La1-xPrx)0.67 Ca0.33MnO3 thin films by composition spread deposition and electrolyte gating

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaohang; Liang, Y. G.; Fackler, S.; Shin, J.-M.; Takeuchi, Ichiro; N'diaye, A. T.; Arenholz, E.

    2015-03-01

    The magnetic and electronic properties of mixed-valence manganites are known to be sensitive not only to chemical doping but also to oxygen concentration. However, it is difficult to consistently attain exactly the same set of deposition conditions and treatment history for samples that are fabricated individually. In order to perform systematic studies on each of the two effects, we fabricated epitaxial (La1-xPrx)0.67 Ca0.33MnO3 (LPCMO) composition spread thin films with the Pr concentration changing continuously across 1 cm to ensure that all the sample segments of interest experience the same processing history. X-ray magnetic circular dichroism (XMCD) and electronic transport measurements indicated that the Curie temperatures and the metal-insulator transition temperatures change continuously from ~ 260 K to ~ 120 K as the Pr concentration is varied from 0 to 0.33. Systematic comparison between experimental data obtained on as-grown and post-annealed samples reveals the role of oxygen in the observed magnetic and electronic transitions. Moreover, changes in the magnetic and electronic properties of LPCMO films under electrolyte-gating have also been observed. A proposed mechanism to explain the effect will be discussed.

  1. Structural development of the Jurassic Magnetic Quiet Zone off Morocco and identification of Middle Jurassic magnetic lineations

    NASA Astrophysics Data System (ADS)

    Roeser, H. A.; Steiner, C.; Schreckenberger, B.; Block, M.

    2002-10-01

    Geophysical investigations carried out during two Meteor cruises have revealed weak linear magnetic anomalies in those parts of the Jurassic Magnetic Quiet Zone (JMQZ) off Morocco that are not affected by Cenozoic igneous activity. The linear magnetic anomalies are not correlated with variations in relief or structure of oceanic crust. Using the reversal sequence M25-M41, the anomalies of the JMQZ can be modeled with a half spreading rate of 2.2 cm/yr. Extrapolation of the weak lineations back to the slope anomaly S1 results in a breakup age of 170 Ma. According to this interpretation the crust of the JMQZ off Morocco has formed during the time 170-155 Ma (Bajocian to Oxfordian). However, much lower spreading rates (around 1 cm/yr) cannot be excluded. S1 coincides with a poorly developed "seaward dipping reflector sequence" (SDRS), which is most likely its source. The SDRS corroborates the earlier claim that S1 marks the ocean-continent transition. Seaward of S1 is a 70-km-wide strip of horizontal reflectors that become landward dipping to the west in the uppermost part of the basement; it parallels S1 over a distance of 200 km and may indicate excessive magma supply within the first 2 m.y. of seafloor spreading. Similar landward dipping reflectors are observed also in the conjugate Sohm Abyssal Plain off Nova Scotia. The average magnetization of the landward dipping reflectors is much lower than that of the SDRS. A lower crustal body with a seismic velocity of ˜7.3 km/s, which formed during the Neogene beneath the eastern part of the Essaouira Rise, has only a weak magnetization (<0.5 A/m).

  2. Vascular anomalies in children.

    PubMed

    Weibel, L

    2011-11-01

    Vascular anomalies are divided in two major categories: tumours (such as infantile hemangiomas) and malformations. Hemangiomas are common benign neoplasms that undergo a proliferative phase followed by stabilization and eventual spontaneous involution, whereas vascular malformations are rare structural anomalies representing morphogenetic errors of developing blood vessels and lymphatics. It is important to properly diagnose vascular anomalies early in childhood because of their distinct differences in morbidity, prognosis and need for a multidisciplinary management. We discuss a number of characteristic clinical features as clues for early diagnosis and identification of associated syndromes.

  3. Dual diaphragmatic anomalies

    PubMed Central

    Padmanabhan, Arjun; Thomas, Abin Varghese

    2016-01-01

    Although diaphragmatic anomalies such as an eventration and hiatus hernia are commonly encountered in incidental chest X-ray imaging, the presence of concomitant multiple anomalies is extremely rare. This is all the more true in adults. Herein, we present the case of a 75-year-old female, while undergoing a routine chest X-ray imaging, was found to have eventration of right hemidiaphragm along with a hiatus hernia as well. PMID:27625457

  4. Seafloor Spreading Reorganization South of Iceland

    NASA Astrophysics Data System (ADS)

    Hey, R. N.; Martinez, F.; Benediktsdottir, A.; Hoskuldsson, A.

    2011-12-01

    excellent magnetic anomaly fits can only be achieved if some rift propagation toward Iceland has also occurred. These newly identified propagators toward Iceland can't be driven by plume pulses even if the ones propagating away from Iceland are. Rift propagation is an alternative way to produce V-shaped wakes of thin crust & grabens, e.g. Earth's deepest axial valley is at the tip of the Pito propagator which has created the transient Easter microplate. (Hey had the great pleasure of sailing on the Nautile expedition Jean Francheteau led to Pito Deep, & after that advised his students to sail on French ships every chance they got). The involvement of rift propagation in VSR formation suggests this is also a possible explanation for the ongoing major transform-fault eliminating reorganization. If so, the tip of the reorganization would presently be near the first transform fault south of Iceland, the Bight transform near 56.8N, rather than in the extensively surveyed area 200 km farther north where the thermal reorganization model predicted the reorganization tip should be.

  5. Z_{2} and Chiral Anomalies in Topological Dirac Semimetals.

    PubMed

    Burkov, Anton A; Kim, Yong Baek

    2016-09-23

    We demonstrate that topological Dirac semimetals, which possess two Dirac nodes, separated in momentum space along a rotation axis and protected by rotational symmetry, exhibit an additional quantum anomaly, distinct from the chiral anomaly. This anomaly, which we call the Z_{2} anomaly, is a consequence of the fact that the Dirac nodes in topological Dirac semimetals carry a Z_{2} topological charge. The Z_{2} anomaly refers to nonconservation of this charge in the presence of external fields due to quantum effects and has observable consequences due to its interplay with the chiral anomaly. We discuss possible implications of this for the interpretation of magnetotransport experiments on topological Dirac semimetals. We also provide a possible explanation for the magnetic field dependent angular narrowing of the negative longitudinal magnetoresistance, observed in a recent experiment on Na_{3}Bi.

  6. Elastic anomalies in a La 1.85Sr 0.15CuO 4 single crystal under high magnetic fields

    NASA Astrophysics Data System (ADS)

    Hanaguri, Tetsuo; Fukase, Tetsuo; Suzuki, Takao; Tanaka, Isao; Kojima, Hironao

    1994-02-01

    Temperature dependence of the sound velocity Vs in a La 1.85Sr 0.15CuO 4 single crystal has been measured in the ( c11 - c12)/2 mode and in the c33 mode under high magnetic fields up to 23T. In the field above 6T, Vs in the ( c11 - c12)/2 mode anomalously decreases with decreasing temperature, followed by the increase below about 10K. In the c33 mode, similar behavior of Vs can be observed above 20T. Such a temperature dependence of Vs may suggest the existence of a strain sensitive narrow band near the Fermi level or a phase transition related to the flux line lattice.

  7. How Leaky Are Seafloor Spreading Center Axes?

    NASA Astrophysics Data System (ADS)

    Baker, E. T.; Resing, J. A.; Martinez, F.; Haymon, R. M.; Nakamura, K.; Walker, S. L.; Ferrini, V.

    2013-12-01

    Some 500 active vent sites, both focused and diffuse, have now been located along spreading centers by either visual confirmation or instrumental detection of the discharging plume. Discovery of the large majority of these sites was made easier by high-volume discharge of particle-laden plumes. These observations led to estimates (as can be derived from the InterRidge Vents Database) of site frequency from ~0.5-5/100 km, generally increasing with spreading rate. Over the last decade, however, the increasing use of oxidation-reduction potential (ORP (mV)) (aka Eh) sensors capable of detecting minute concentrations of reduced hydrothermal chemicals (e.g., Fe+2, sulfides, Mn+2, H2, and others) suggests that these frequency estimates may be far too conservative. This hypothesis is consistent with earlier results from a few large-scale, high-resolution camera tows on some EPR segments. ORP data provide two important advantages for site identification not available with other commonly used continuously recording sensors: (1) detection of low-temperature, particle-scarce plumes, and (2) detection of reduced chemical species with very short residence times, thus increasing the location specificity of the discharge source. Here, we present high-resolution distributions of ORP anomalies observed in past plume surveys along the Eastern Lau Spreading Center (19.5°-22.5°S) in 2004 and 2008, the Galápagos Spreading Center (94.6°-86°W) in 2005/6 and 2011, as well as new data (2011) from the East Pacific Rise (9°-10°N). Except for the 2011 GSC data (a standard CTD tow-yo), all data were collected during continuous horizontal tows of ORP sensors at various depths <~120 m above the seafloor. We used two approaches to verify that ORP anomalies were authentic hydrothermal signals and not (especially in the case of small anomalies) produced by some other transient chemical anomaly. First, on the 2008 ELSC and 2011 EPR tows we compared temperature (ΔT) and ORP (ΔORP) data from

  8. Astrometric solar system anomalies

    SciTech Connect

    Nieto, Michael Martin; Anderson, John D

    2009-01-01

    There are at least four unexplained anomalies connected with astrometric data. perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it often experiences a change in total orbital energy per unit mass. next, a secular change in the astronomical unit AU is definitely a concern. It is increasing by about 15 cm yr{sup -1}. The other two anomalies are perhaps less disturbing because of known sources of nongravitational acceleration. The first is an apparent slowing of the two Pioneer spacecraft as they exit the solar system in opposite directions. Some astronomers and physicists are convinced this effect is of concern, but many others are convinced it is produced by a nearly identical thermal emission from both spacecraft, in a direction away from the Sun, thereby producing acceleration toward the Sun. The fourth anomaly is a measured increase in the eccentricity of the Moon's orbit. Here again, an increase is expected from tidal friction in both the Earth and Moon. However, there is a reported unexplained increase that is significant at the three-sigma level. It is produent to suspect that all four anomalies have mundane explanations, or that one or more anomalies are a result of systematic error. Yet they might eventually be explained by new physics. For example, a slightly modified theory of gravitation is not ruled out, perhaps analogous to Einstein's 1916 explanation for the excess precession of Mercury's perihelion.

  9. Conductivity Anomalies in Central Europe

    NASA Astrophysics Data System (ADS)

    Neska, Anne

    2016-01-01

    This paper is a review of studies which, by applying the magnetotelluric, geomagnetic deep sounding, and magnetovariational sounding methods (the latter refers to usage of the horizontal magnetic tensor), investigate Central Europe for zones of enhanced electrical conductivity. The study areas comprise the region of the Trans-European Suture Zone (i.e. the south Baltic region and Poland), the North German Basin, the German and Czech Variscides, the Pannonian Basin (Hungary), and the Polish, Slovakian, Ukrainian, and Romanian Carpathians. This part of the world is well investigated in terms of data coverage and of the density of published studies, whereas the certainty that the results lead to comprehensive interpretations varies within the reviewed literature. A comparison of spatially coincident or adjacent studies reveals the important role that the data coverage of a distinct conductivity anomaly plays for the consistency of results. The encountered conductivity anomalies are understood as linked to basin sediments, asthenospheric upwelling, large differences in lithospheric age, and—this concerns most of them, which all concentrate in the middle crust—tectonic boundaries that developed during all mountain building phases that have taken place on the continent.

  10. Statistical Anomaly Detection for Monitoring of Human Dynamics

    NASA Astrophysics Data System (ADS)

    Kamiya, K.; Fuse, T.

    2015-05-01

    Understanding of human dynamics has drawn attention to various areas. Due to the wide spread of positioning technologies that use GPS or public Wi-Fi, location information can be obtained with high spatial-temporal resolution as well as at low cost. By collecting set of individual location information in real time, monitoring of human dynamics is recently considered possible and is expected to lead to dynamic traffic control in the future. Although this monitoring focuses on detecting anomalous states of human dynamics, anomaly detection methods are developed ad hoc and not fully systematized. This research aims to define an anomaly detection problem of the human dynamics monitoring with gridded population data and develop an anomaly detection method based on the definition. According to the result of a review we have comprehensively conducted, we discussed the characteristics of the anomaly detection of human dynamics monitoring and categorized our problem to a semi-supervised anomaly detection problem that detects contextual anomalies behind time-series data. We developed an anomaly detection method based on a sticky HDP-HMM, which is able to estimate the number of hidden states according to input data. Results of the experiment with synthetic data showed that our proposed method has good fundamental performance with respect to the detection rate. Through the experiment with real gridded population data, an anomaly was detected when and where an actual social event had occurred.

  11. A review of magnetic stratigraphy investigations in Cretaceous pelagic carbonate rocks

    NASA Astrophysics Data System (ADS)

    Lowrie, W.; Channell, J. E. T.; Alvarez, W.

    1980-07-01

    Pelagic carbonate rocks possess many suitable characteristics for paleomagnetic and magnetostratigraphic studies. Paleomagnetic results are summarized for seven lengthy sections of pelagic limestones and marls from Umbria and the southern Alps in Italy. Differences in apparent polar wander paths from these two regions are interpreted in terms of tectonic rotation of allochthonous Umbria. The magnetic stratigraphies of the paleontologically dated sections are independent of their tectonic differences and are combined to form a continuous record of geomagnetic polarity for the Barremian through Maastrichtian stages of the Cretaceous. All but one of the reversals in these sections are confirmed by duplication in at least one other section. Additional Cretaceous reversals have been reported in other land sections and in DSDP (Deep Sea Drilling Project) and IPOD (International Program of Ocean Drilling) cores. Some of these reversals are not defined well magnetically, and confirmation of others is clouded by imprecise paleontological dates. If real, they are probably of short duration. The confirmed reversal sequence correlates well with the Cretaceous oceanic magnetic anomaly sequence. The ages of certain key anomalies are altered: Late Cretaceous anomalies 29-34 are younger, and Early Cretaceous anomalies M0 and M1 are older than previously thought. The longer duration of the Cretaceous magnetic quiet interval of normal polarity results in a reduction of corresponding sea floor spreading rates to about 70% of earlier values, but they are still appreciably higher than during formation of the preceding M sequence anomalies.

  12. The spreading of disorder.

    PubMed

    Keizer, Kees; Lindenberg, Siegwart; Steg, Linda

    2008-12-12

    Imagine that the neighborhood you are living in is covered with graffiti, litter, and unreturned shopping carts. Would this reality cause you to litter more, trespass, or even steal? A thesis known as the broken windows theory suggests that signs of disorderly and petty criminal behavior trigger more disorderly and petty criminal behavior, thus causing the behavior to spread. This may cause neighborhoods to decay and the quality of life of its inhabitants to deteriorate. For a city government, this may be a vital policy issue. But does disorder really spread in neighborhoods? So far there has not been strong empirical support, and it is not clear what constitutes disorder and what may make it spread. We generated hypotheses about the spread of disorder and tested them in six field experiments. We found that, when people observe that others violated a certain social norm or legitimate rule, they are more likely to violate other norms or rules, which causes disorder to spread.

  13. Flame spread across liquids

    NASA Technical Reports Server (NTRS)

    Ross, Howard D.; Miller, Fletcher; Schiller, David; Sirignano, William

    1995-01-01

    Recent reviews of our understanding of flame spread across liquids show that there are many unresolved issues regarding the phenomenology and causal mechanisms affecting ignition susceptibility, flame spread characteristics, and flame spread rates. One area of discrepancy is the effect of buoyancy in both the uniform and pulsating spread regimes. The approach we have taken to resolving the importance of buoyancy for these flames is: (1) normal gravity (1g) and microgravity (micro g) experiments; and (2) numerical modeling at different gravitational levels. Of special interest to this work, as discussed at the previous workshop, is the determination of whether, and under what conditions, pulsating spread occurs in micro g. Microgravity offers a unique ability to modify and control the gas-phase flow pattern by utilizing a forced air flow over the pool surface.

  14. Clinical features and associated abnormalities in children and adolescents with corpus callosal anomalies.

    PubMed

    Kim, Young Uhk; Park, Eun Sook; Jung, Soojin; Suh, Miri; Choi, Hyo Seon; Rha, Dong-Wook

    2014-02-01

    Callosal anomalies are frequently associated with other central nervous system (CNS) and/or somatic anomalies. We retrospectively analyzed the clinical features of corpus callosal agenesis/hypoplasia accompanying other CNS and/or somatic anomalies. We reviewed the imaging and clinical information of patients who underwent brain magnetic resonance imaging in our hospital, between 2005 and 2012. Callosal anomalies were isolated in 13 patients, accompanied by other CNS anomalies in 10 patients, associated with only non-CNS somatic anomalies in four patients, and with both CNS and non-CNS abnormalities in four patients. Out of 31 patients, four developed normally, without impairments in motor or cognitive functions. Five of nine patients with cerebral palsy were accompanied by other CNS and/or somatic anomalies, and showed worse Gross Motor Function Classification System scores, compared with the other four patients with isolated callosal anomaly. In addition, patients with other CNS anomalies also had a higher seizure risk.

  15. Euro-African MAGSAT anomaly-tectonic observations

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Olivier, R.; Vonfrese, R. R. B.

    1985-01-01

    Preliminary satellite (MAGSAT) scalar magnetic anomaly data are compiled and differentially reduced to radial polarization by equivalent point source inversion for comparison with tectonic data of Africa, Europe and adjacent marine areas. A number of associations are evident to constrain analyses of the tectonic features and history of the region. The Precambrian shields of Africa and Europe exhibit varied magnetic signatures. All shields are not magnetic highs and, in fact, the Baltic shield is a marked minimum. The reduced-to-the-pole magnetic map shows a marked tendency for northeasterly striking anomalies in the eastern Atlantic and adjacent Africa, which is coincident to the track of several hot spots for the past 100 million years. However, there is little consistency in the sign of the magnetic anomalies and the track of the hot spots. Comparison of the radially polarized anomalies of Africa and Europe with other reduced-to-the-pole magnetic satellite anomaly maps of the Western Hemisphere support the reconstruction of the continents prior to the origin of the present-day Atlantic Ocean in the Mesozoic Era.

  16. Euro-african MAGSAT Anomaly-tectonic Observations

    NASA Technical Reports Server (NTRS)

    Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator); Olivier, R.

    1984-01-01

    Preliminary satellite (MAGSAT) scalar magnetic anomaly data are compiled and differentially reduced to radial polarization by equivalent point source inversion for comparison with tectonic data of Africa, Europe and adjacent marine areas. A number of associations are evident to constrain analyses of the tectonic features and history of the region. The Precambrian shields of Africa and Europe exhibit varied magnetic signatures. All shields are not magnetic highs and, in fact, the Baltic shield is a marked minimum. The reduced-to-the-pole magnetic map shows a marked tendency for northeasterly striking anomalies in the eastern Atlantic and adjacent Africa, which is coincident to the track of several hot spots for the past 100 million years. However, there is little consistency in the sign of the magnetic anomalies and the track of the hot spots. Comparison of the radially polarized anomalies of Africa and Europe with other reduced-to-the-pole magnetic satellite anomaly maps of the Western Hemisphere support the reconstruction of the continents prior to the origin of the present-day Atlantic Ocean in the Mesozoic Era.

  17. Electromagnetic Duality Anomaly in Curved Spacetimes

    NASA Astrophysics Data System (ADS)

    Agullo, Ivan; del Rio, Adrian; Navarro-Salas, Jose

    2017-03-01

    The source-free Maxwell action is invariant under electric-magnetic duality rotations in arbitrary spacetimes. This leads to a conserved classical Noether charge. We show that this conservation law is broken at the quantum level in the presence of a background classical gravitational field with a nontrivial Chern-Pontryagin invariant, in parallel with the chiral anomaly for massless Dirac fermions. Among the physical consequences, the net polarization of the quantum electromagnetic field is not conserved.

  18. MAGSAT anomaly field data of the crustal properties of Australia

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Progress is reported in producing maps of Australia showing; crustal magnetic anomalies at constant elevation; bulk surface magnetization; and the geomagnetic field intensity, inclination and declination for the Australian region from global models of the geomagnetic field derived from MAGSAT data. The development of a data base management system is also considered.

  19. Comparative analysis of spread-F signature and GPS scintillation occurrences at Tucumán, Argentina

    NASA Astrophysics Data System (ADS)

    Alfonsi, L.; Spogli, L.; Pezzopane, M.; Romano, V.; Zuccheretti, E.; de Franceschi, G.; Cabrera, M. A.; Ezquer, R. G.

    2013-07-01

    analyze data recorded from October 2010 to September 2011, during the ascending phase of the 24th solar cycle, from an Advanced Ionospheric Sounder-Istituto Nazionale di Geofisica e Vulcanologia ionosonde and a GPS Ionospheric Scintillation and total electron content (TEC) monitor scintillation receiver, colocated at low latitude in the Southern American longitudinal sector (Tucumán, 26.9°S, 294.6°E, magnetic latitude 15.5°S, Argentina). The site offers the opportunity to perform spread-F and GPS scintillation statistics of occurrence under the southern crest of the equatorial ionospheric anomaly. Spread-F signatures, classified into four types (strong range spread-F (SSF), range spread-F, frequency spread-F (FSF), and mixed spread-F), the phase and amplitude scintillation index (σΦ and S4, respectively), the TEC, and the rate of TEC parameter, marker of the TEC gradients, that can cause scintillations, are considered. The seasonal behavior results as follows: the occurrence of all four types of spread-F is higher in summer and lower in winter, while the occurrence of scintillations peaks at equinoxes in the postsunset sector and shows a minimum in winter. The correspondence between SSF and scintillations seems to be systematic, and a possible correlation between S4 and FSF peaks is envisaged at the terminator. The investigation focused also on two particular periods, from 12 to 16 March 2011 and from 23 to 29 September 2011, both characterized by the simultaneous presence of SSF signatures and scintillation phenomena, allowing to discuss the role of traveling ionospheric disturbances as a strong candidate causing ionospheric irregularities.

  20. Flame Spread Across Liquids

    NASA Technical Reports Server (NTRS)

    Ross, Howard D.; Miller, Fletcher J.; Sirignano, William A.; Schiller, David

    1997-01-01

    The principal goal of our recent research on flame spread across liquid pools is the detailed identification of the mechanisms that control the rate and nature of flame spread when the liquid pool is initially at an isothermal bulk temperature that is below the fuel's flash point temperature. In our project, we specialize the subject to highlight the roles of buoyancy-related processes regarding the mechanisms of flame spread, an area of research cited recently by Linan and Williams as one that needs further attention and which microgravity (micro-g) experiments could help to resolve. Toward resolving the effects of buoyancy on this flame spread problem, comparisons - between 1-g and micro-g experimental observations, and between model predictions and experimental data at each of these gravitational levels - are extensively utilized. The present experimental and computational foundation is presented to support identification of the mechanisms that control flame spread in the pulsating flame spread regime for which long-duration, micro-g flame spread experiments have been conducted aboard a sounding rocket.

  1. Deep crustal structure of the northeastern Gulf of Mexico: Implications for rift evolution and seafloor spreading

    NASA Astrophysics Data System (ADS)

    Eddy, Drew R.; Van Avendonk, Harm J. A.; Christeson, Gail L.; Norton, Ian O.; Karner, Garry D.; Johnson, Christopher A.; Snedden, John W.

    2014-09-01

    We image deep crustal structure using marine seismic refraction data recorded by a linear array of ocean-bottom seismometers in the Gulf of Mexico Basin Opening project (GUMBO Line 3) in order to provide new constraints on the nature of continental and oceanic crust in the northeastern Gulf of Mexico. GUMBO Line 3 extends ~524 km from the continental shelf offshore Pensacola, Florida, across the De Soto Canyon and into the central Gulf basin. Travel times from long offset, wide angle reflections and refractions resolve compressional seismic velocities and layer boundaries for sediment, crystalline crust, and upper mantle. We compare our results with coincident multichannel seismic reflection data. Our velocity model recovers shallow seismic velocities (~2.0-4.5 km/s) that we interpret as evaporites and clastic sediments. A Cretaceous carbonate platform is interpreted beneath the De Soto Canyon with seismic velocities >5.0 km/s. Crystalline continental crust thins seaward along GUMBO Line 3 from 23-10 km across the De Soto Canyon. High seismic velocity lower crust (>7.2 km/s) is interpreted as extensive syn-rift magmatism and possibly mafic underplating, common features at volcanic rift margins with high mantle potential temperatures. In the central Gulf basin we interpret thick oceanic crust (>8 km) emplaced at a slow full-spreading rate (~24 mm/yr). We suggest a sustained thermal anomaly during slow seafloor-spreading conditions led to voluminous basalt flows from a spreading ridge that overprinted seafloor magnetic anomalies in the northeastern Gulf of Mexico.

  2. Orbital studies of lunar magnetism

    NASA Technical Reports Server (NTRS)

    Mcleod, M. G.; Coleman, P. J., Jr.

    1982-01-01

    Limitations of present lunar magnetic maps are considered. Optimal processing of satellite derived magnetic anomaly data is also considered. Studies of coastal and core geomagnetism are discussed. Lunar remanent and induced lunar magnetization are included.

  3. Normal-state anomalies in the transport and magnetic properties in the (La1-xPrx)1.85Sr0.15CuO4 system and their correlation with Tc suppression: A signature of the effects of orthorhombic distortions

    NASA Astrophysics Data System (ADS)

    Musa, J. E.; García, S.; Rothier de Amaral, M., Jr.; Salim de Amorim, H.; Giordanengo, B.; Baggio-Saitovitch, E. M.; Pagliuso, P. J. G.; Rettori, C.; Yelon, W. B.; Malik, S. K.

    1999-03-01

    The correlation between the normal-state anomalies observed in the magnetic and transport properties of the (La1-xPrx)1.85Sr0.15CuO4 system with 0<=x<=0.5 was studied. The x-ray-diffraction patterns revealed a linear increase of the (a-b) orthorhombic parameter with the Pr content. The resistivity curves showed an increasing deviation from linearity below ~100 K. This anomaly was properly accounted by a logarithmic term, whose coefficient C linearly increases with x. Superconducting quantum interference device measurements of the normal-state magnetic susceptibility evidenced a deviation from the Pr3+ Curie-Weiss behavior in the same temperature range for which the resistivity anomaly occurs. This behavior is explained in terms of an induced magnetic moment at the CuO2 layers under strain. A Dzialoshinsky-Moriya interaction, associated to the orthorhombic distortions, is proposed to be the source of a weak canted ferromagnetic component, which develops in conjunction with an enhancement of the antiferromagnetic correlations. A comprehensive picture of the conduction mechanism for the whole system is presented in terms of a Kondo-like scattering of the mobile holes by the spin fluctuations at the conduction planes. Tc suppression was found to correlate with C, suggesting that the excitation which interacts with the carriers in the normal state is relevant for superconductivity.

  4. Hawking radiation and covariant anomalies

    SciTech Connect

    Banerjee, Rabin; Kulkarni, Shailesh

    2008-01-15

    Generalizing the method of Wilczek and collaborators we provide a derivation of Hawking radiation from charged black holes using only covariant gauge and gravitational anomalies. The reliability and universality of the anomaly cancellation approach to Hawking radiation is also discussed.

  5. XYY chromosome anomaly and schizophrenia.

    PubMed

    Rajagopalan, M; MacBeth, R; Varma, S L

    1998-02-07

    Sex chromosome anomalies have been associated with psychoses, and most of the evidence is linked to the presence of an additional X chromosome. We report a patient with XYY chromosome anomaly who developed schizophrenia.

  6. Quantum Spread Spectrum Communication

    SciTech Connect

    Humble, Travis S

    2010-01-01

    We demonstrate that spectral teleportation can coherently dilate the spectral probability amplitude of a single photon. In preserving the encoded quantum information, this variant of teleportation subsequently enables a form of quantum spread spectrum communication.

  7. Analysis and interpretation of MAGSAT anomalies over north Africa

    NASA Technical Reports Server (NTRS)

    Phillips, R. J.

    1985-01-01

    Crustal anomaly detection with MAGSAT data is frustrated by inherent resolving power of the data and by contamination from external and core fields. Quality of the data might be tested by modeling specific tectonic features which produce anomalies that fall within proposed resolution and crustal amplitude capabilities of MAGSAT fields. To test this hypothesis, north African hotspots associated with Ahaggar, Tibesti and Darfur were modeled as magnetic induction anomalies. MAGSAT data were reduced by subtracting external and core fields to isolate scalar and vertical component crustal signals. Of the three volcanic areas, only the Ahaggar region had an associated anomaly of magnitude above error limits of the data. Hotspot hypothesis was tested for Ahaggar by seeing if predicted magnetic signal matched MAGSAT anomaly. Predicted model magnetic signal arising from surface topography of the uplift and the Curie isothermal surface was calculated at MAGSAT altitudes by Fourier transform technique modified to allow for variable magnetization. Curie isotherm surface was calculated using a method for temperature distribution in a moving plate above a fixed hotspot. Magnetic signal was calculated for a fixed plate as well as a number of plate velocities and directions.

  8. Ebstein Anomaly in Pregnancy.

    PubMed

    Rusdi, Lusiani; Azizi, Syahrir; Suwita, Christopher; Karina, Astrid; Nasution, Sally A

    2016-10-01

    A 27-year-old primiparous woman with 28 weeks gestational age was admitted to our hospital with worsening shortness of breath. She was diagnosed with Ebstein's anomaly three years ago, but preferred to be left untreated. The patient was not cyanotic and her vital signs were stable. Her ECG showed incomplete RBBB and prolonged PR-interval. Blood tests revealed mild anemia. Observation of two-dimensional echo with color flow Doppler study showed Ebstein's anomaly with PFO as additional defects, EF of 57%, LV and LA dilatation, RV atrialization, severe TR, and moderate PH with RVSP of 44.3 mmHg. The patient then underwent elective sectio caesaria at 30 weeks of gestational age; both the mother and her baby were alive and were in good conditions.

  9. Pathogenesis of Vascular Anomalies

    PubMed Central

    Boon, Laurence M.; Ballieux, Fanny; Vikkula, Miikka

    2010-01-01

    Vascular anomalies are localized defects of vascular development. Most of them occur sporadically, i.e. there is no familial history of lesions, yet in a few cases clear inheritance is observed. These inherited forms are often characterized by multifocal lesions that are mainly small in size and increase in number with patient’s age. On the basis of these inherited forms, molecular genetic studies have unraveled a number of inherited mutations giving direct insight into the pathophysiological cause and the molecular pathways that are implicated. Genetic defects have been identified for hereditary haemorrhagic telangiectasia (HHT), inherited cutaneomucosal venous malformation (VMCM), glomuvenous malformation (GVM), capillary malformation - arteriovenous malformation (CM-AVM), cerebral cavernous malformation (CCM) and some isolated and syndromic forms of primary lymphedema. We focus on these disorders, the implicated mutated genes and the underlying pathogenic mechanisms. We also call attention to the concept of Knudson’s double-hit mechanism to explain incomplete penetrance and the large clinical variation in expressivity of inherited vascular anomalies. This variability renders the making of correct diagnosis of the rare inherited forms difficult. Yet, the identification of the pathophysiological causes and pathways involved in them has had an unprecedented impact on our thinking of their etiopathogenesis, and has opened the doors towards a more refined classification of vascular anomalies. It has also made it possible to develop animal models that can be tested for specific molecular therapies, aimed at alleviating the dysfunctions caused by the aberrant genes and proteins. PMID:21095468

  10. Ebstein's Anomaly, Left Ventricular Noncompaction, and Sudden Cardiac Death

    PubMed Central

    McGee, Michael; Warner, Luke; Collins, Nicholas

    2015-01-01

    Ebstein's anomaly is a congenital disorder characterized by apical displacement of the septal leaflet of the tricuspid valve. Ebstein's anomaly may be seen in association with other cardiac conditions, including patent foramen ovale, atrial septal defect, and left ventricular noncompaction (LVNC). LVNC is characterized by increased trabeculation within the left ventricular apex. Echocardiography is often used to diagnose LVNC; however, magnetic resonance (MR) imaging offers superior characterization of the myocardium. We report a case of sudden cardiac death in a patient with Ebstein's anomaly with unrecognized LVNC noted on post mortem examination with screening documenting the presence of LVNC in one of the patient's twin sons. PMID:26240764

  11. Sediment stratigraphy of the Nansen Basin, Arctic Ocean and characterization of the ultraslow-spreading oceanic crust

    NASA Astrophysics Data System (ADS)

    Lutz, R.; Franke, D.; Berglar, K.; Schnabel, M.

    2015-12-01

    The Nansen Basin is the southern part of the Eurasia Basin in the Arctic Ocean. Opening of the Eurasia Basin started here with the tear-off of the continental Lomonossov ridge. Here we present a couple of multichannel reflection seismic lines, covering an area from the Barents Shelf to 83.2 deg N. The profiles extend for about 275 km and 170 km, respectively from the Barents Sea margin (Hinlopen margin) into northern direction and cover together ~300 km of oceanic crust on two parallel lines. One connecting profile was acquired on oceanic crust crossing anomaly C23 (~50-52 Ma). The data were acquired during ice-free conditions and reveal for the first time the architecture of the oldest sediments deposited on the oceanic crust. We discuss the seismic facies of the oldest sediments on the oceanic crust and determine their age by correlation of onlap contacts onto oceanic crust with well defined magnetic anomalies. The lowermost sedimentary unit can be subdivided by at least one more prominent seismic reflector in the distal part of the Nansen Basin and two more seismic reflectors in the proximal part. Furthermore we present images and interpretations of oceanic crust formed at the ultraslow-spreading Gakkel ridge (< 20 mm yr-1 full rate). We discuss the basement morphology, volcanic cones and major faults, bounding horsts and grabens in the light of our present understanding of melt-poor ultraslow-spreading ridges.

  12. Equatorial spread-F (ESF) and vertical winds

    NASA Astrophysics Data System (ADS)

    Raghavarao, R.; Suhasini, R.; Mayr, H. G.; Hoegy, W. R.; Wharton, L. E.

    1999-05-01

    The Equatorial Spread-F (ESF) phenomenon is recorded in ionograms as a hierarchy of plasma instabilities in the F-layer of the equatorial ionosphere. The ESF is characterized by irregularities in the plasma (electron and ion) density and electric field distributions perpendicular to the Earth's magnetic field. Large scale irregularities are generated by a primary plasma instability that develops in electric fields and plasma densities. Other secondary instabilities then develop and generate irregularities at several scale sizes that often produce a plasma `hole' or `bubble' that rises up with high E×B velocities. The ESF/plasma bubble phenomenon has been studied extensively with experimental techniques and modeling, which revealed important features. In the bottom side F-layer, near sunset, when the vertical density gradient steepens as the layer is supported by the horizontal (North-South) Earth's magnetic field lines against the omnipresent Earth's gravitational acceleration (g), the plasma conditions can give rise to Rayleigh-Taylor (RT) type instability. But the observed day to day variability of the ESF occurrence suggested that other agencies may also be involved in generating the instability. Sekar and Raghavarao (1987) with linear theory, and Raghavarao, Sekar and Suhasini (1992), with non-linear numerical modeling, suggested that vertical downward (upward) winds in the ambient gas have the potential to cause (inhibit) the ESF/bubble phenomenon. The presence of downward winds near the equator was reported earlier. In this paper, we show evidence for the presence of downward winds collocated with irregularities in electric fields and plasma densities as revealed by an unique combination of highly accurate measurements with instruments onboard the DE-2 satellite. The observations reported here are also consistent with the notion that the build-up of the equatorial ionization anomaly (EIA) prior to local sunset is important for the ESF instability.

  13. Crustal structure and magnetic lineation along two geo-traverses from western continental margin of India to Eastern Somali Basin, NW Indian Ocean

    NASA Astrophysics Data System (ADS)

    Chaubey, A. K.; Anshu, A.; Sreejith, K.; Pandey, A.

    2012-12-01

    Shipborne gravity and magnetic data along two parallel geo-traverses spanning from western continental margin of India to off Seychelles are used to delineate crustal structure and magnetic pattern of major structural features - western continental margin of India, Laxmi Basin, Laxmi Ridge, Arabian Basin, slow spreading Carlsberg Ridge and Eastern Somali Basin. The seismically constrained gravity models along the geo-traverses suggest considerable variation in crustal thickness - about 38 km on continental shelf of western India to about 4 km of the Eastern Somali Basin. The Eastern Somali Basin is characterized by thin oceanic crustal thickness (~3 to 4 km) as compared to its conjugate Arabian Basin where thickness varies from 5 to 6 km. The magnetic anomalies along the geo-traverse reveal three distinct zones: (i) a zone of relative high frequency short wavelength younger anomalies over the axial parts of the Carlsberg Ridge, (ii) a zone of well developed Early Tertiary magnetic anomalies in both the Arabian and Eastern Somali basins, and (iii) relative magnetic quiet zone, between the above two zones, representing a hiatus in spreading. Based on the results, we present a comparative analysis of crustal configuration and magnetic pattern of major structural features of the study area and discuss its tectonic evolution.

  14. Physicochemical isotope anomalies

    SciTech Connect

    Esat, T.M.

    1988-06-01

    Isotopic composition of refractory elements can be modified, by physical processes such as distillation and sputtering, in unexpected patterns. Distillation enriches the heavy isotopes in the residue and the light isotopes in the vapor. However, current models appear to be inadequate to describe the detailed mass dependence, in particular for large fractionations. Coarse- and fine-grained inclusions from the Allende meteorite exhibit correlated isotope effects in Mg both as mass-dependent fractionation and residual anomalies. This isotope pattern can be duplicated by high temperature distillation in the laboratory. A ubiquitous property of meteoritic inclusions for Mg as well as for most of the other elements, where measurements exist, is mass-dependent fractionation. In contrast, terrestrial materials such as microtektites, tektite buttons as well as lunar orange and green glass spheres have normal Mg isotopic composition. A subset of interplanetary dust particles labelled as chondritic aggregates exhibit excesses in {sup 26}Mg and deuterium anomalies. Sputtering is expected to be a dominant mechanism in the destruction of grains within interstellar dust clouds. An active proto-sun as well as the present solar-wind and solar-flare flux are of sufficient intensity to sputter significant amounts of material. Laboratory experiments in Mg show widespread isotope effects including residual {sup 26}Mg excesses and mass dependent fractionation. It is possible that the {sup 26}Mg excesses in interplanetary dust is related to sputtering by energetic solar-wind particles. The implication if the laboratory distillation and sputtering effects are discussed and contrasted with the anomalies in meteoritic inclusions the other extraterrestrial materials the authors have access to.

  15. Mars Crustal Remanent Magnetism: An Extinct Dynamo Leaves a Record of Field Reversals in the Heavily Cratered Highlands

    NASA Technical Reports Server (NTRS)

    Connerney, John E.; Acuna, Mario H.; Ness, Norman F.; Wasilewski, Peter J.

    1999-01-01

    The Mars Global Surveyor spacecraft, in a highly elliptical polar orbit about Mars, obtained vector magnetic field measurements just above the surface of Mars (altitudes > 100 kilometers). Crustal magnetization, largely confined to the most ancient, heavily cratered Mars highlands, is frequently organized in east-west trending linear features, the largest of which extends over 2000 km. A representative set of survey passes are modeled using uniformly magnetized thin plates and a generalized inverse methodology. Crustal remanent magnetization exceeds that deduced for the largest terrestrial magnetic anomalies by more than an order of magnitude. Groups of quasi-parallel linear features of alternating magnetic polarity are found. They are reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on Earth but with a much larger spatial scale.

  16. Topography driven spreading.

    PubMed

    McHale, G; Shirtcliffe, N J; Aqil, S; Perry, C C; Newton, M I

    2004-07-16

    Roughening a hydrophobic surface enhances its nonwetting properties into superhydrophobicity. For liquids other than water, roughness can induce a complete rollup of a droplet. However, topographic effects can also enhance partial wetting by a given liquid into complete wetting to create superwetting. In this work, a model system of spreading droplets of a nonvolatile liquid on surfaces having lithographically produced pillars is used to show that superwetting also modifies the dynamics of spreading. The edge speed-dynamic contact angle relation is shown to obey a simple power law, and such power laws are shown to apply to naturally occurring surfaces.

  17. Detecting Patterns of Anomalies

    DTIC Science & Technology

    2009-03-01

    ct)P (bt|ct) , where A,B and C are mutually exclusive subsets of attributes with at most k elements . This ratio is similar to the previous formula , but...AND SUBTITLE Detecting Patterns of Anomalies 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e...to be dependent if, µ(A,B) ≥ βµ (2.1) where, βµ is a threshold parameter, set to a low value of 0.1 ( empirically ) in our experi- ments. Thus, for a

  18. Einstein, Entropy and Anomalies

    NASA Astrophysics Data System (ADS)

    Sirtes, Daniel; Oberheim, Eric

    2006-11-01

    This paper strengthens and defends the pluralistic implications of Einstein's successful, quantitative predictions of Brownian motion for a philosophical dispute about the nature of scientific advance that began between two prominent philosophers of science in the second half of the twentieth century (Thomas Kuhn and Paul Feyerabend). Kuhn promoted a monistic phase-model of scientific advance, according to which a paradigm driven `normal science' gives rise to its own anomalies, which then lead to a crisis and eventually a scientific revolution. Feyerabend stressed the importance of pluralism for scientific progress. He rejected Kuhn's model arguing that it fails to recognize the role that alternative theories can play in identifying exactly which phenomena are anomalous in the first place. On Feyerabend's account, Einstein's predictions allow for a crucial experiment between two incommensurable theories, and are an example of an anomaly that could refute the reigning paradigm only after the development of a competitor. Using Kuhn's specification of a disciplinary matrix to illustrate the incommensurability between the two paradigms, we examine the different research strategies available in this peculiar case. On the basis of our reconstruction, we conclude by rebutting some critics of Feyerabend's argument.

  19. The XXXXY Chromosome Anomaly

    PubMed Central

    Zaleski, Witold A.; Houston, C. Stuart; Pozsonyi, J.; Ying, K. L.

    1966-01-01

    The majority of abnormal sex chromosome complexes in the male have been considered to be variants of Klinefelter's syndrome but an exception should probably be made in the case of the XXXXY individual who has distinctive phenotypic features. Clinical, radiological and cytological data on three new cases of XXXXY syndrome are presented and 30 cases from the literature are reviewed. In many cases the published clinical and radiological data were supplemented and re-evaluated. Mental retardation, usually severe, was present in all cases. Typical facies was observed in many; clinodactyly of the fifth finger was seen in nearly all. Radiological examination revealed abnormalities in the elbows and wrists in all the 19 personally evaluated cases, and other skeletal anomalies were very frequent. Cryptorchism is very common and absence of Leydig's cells may differentiate the XXXXY chromosome anomaly from polysomic variants of Klinefelter's syndrome. The relationship of this syndrome to Klinefelter's syndrome and to Down's syndrome is discussed. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 5Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10Fig. 11Fig. 12Fig. 13Fig. 14Fig. 15 PMID:4222822

  20. Spreading of miscible liquids

    NASA Astrophysics Data System (ADS)

    Walls, Daniel J.; Haward, Simon J.; Shen, Amy Q.; Fuller, Gerald G.

    2016-05-01

    Miscible liquids commonly contact one another in natural and technological situations, often in the proximity of a solid substrate. In the scenario where a drop of one liquid finds itself on a solid surface and immersed within a second, miscible liquid, it will spread spontaneously across the surface. We show experimental findings of the spreading of sessile drops in miscible environments that have distinctly different shape evolution and power-law dynamics from sessile drops that spread in immiscible environments, which have been reported previously. We develop a characteristic time to scale radial data of the spreading sessile drops based on a drainage flow due to gravity. This time scale is effective for a homologous subset of the liquids studied. However, it has limitations when applied to significantly chemically different, yet miscible, liquid pairings; we postulate that the surface energies between each liquid and the solid surface becomes important for this other subset of the liquids studied. Initial experiments performed with pendant drops in miscible environments support the drainage flow observed in the sessile drop systems.

  1. Survey and Interpretation Geophysical of Magnetic Isochrones 4n.2 a 2A.3 (7.9 3.6 Ma) in the Central Part of the Rivera Plate

    NASA Astrophysics Data System (ADS)

    Perez, D. A.; Mortera-Gutierrez, C. A.; Bandy, W. L.; Valle, S.

    2013-05-01

    This study shows the results of six campaigns marine geophysics BABRIP06 in 2006, MAMRIV07 in 2007, MAMRIV08 in 2008, GUAYRIV10 in 2010, BATIBAJA11 in 2011 and MAMRIV12 in 2012, in the abyssal plain in the East Pacific Rise (EPR), on board the UNAM vessel, B/O El Puma. The oceanographic campaigns single beam bathymetric data collected and marine magnetic data. The results allow analyze and study the magnetic texture in the central north of the Rivera plate associated with geological structures and behavior of the seafloor to the isochronous 5A. The systematic survey of the magnetic data provided high resolution on the guidelines of the magnetic anomalies associated with cortical spreading between 7.9 and 3.6 Ma, generated by the northern segment of the East Pacific Rise (EPR), between the Rivera and Tamayo Oceanic Transformants. Multibeam bathymetry data and the acoustic reflectivity of the six campaigns are correlated with the geometry of the magnetic anomalies and seismic reflection profiles to understand the processes that formed the highlight recreational ocean in this area. The main results in this study is the identification of continuous magnetic isochrones 4n.2 to 2A.3, magnetic anomalies associated with seamounts, the geometry of the isochrones associated with a propagator and magnetic anomaly identification of isochronous 3n.3 had not been demonstrated by other oceanographic surveys. Possibly oceanic spreading rate was slower during these epochs and the identification of a cross anomaly was due to a fracture zone that generated the propagator.

  2. The extent of oceanization of the Egyptian northern Red Sea crust indicated by gravity and magnetic data

    NASA Astrophysics Data System (ADS)

    Khattab, M. M.

    1992-05-01

    A 50 mGal gravity minimum and a 200 nT total magnetic intensity anomaly in the northern Red Sea shelf near the port of Safaga and a 250 nT total intensity anomaly across the Brothers Island indicate a more advanced degree of oceanization of the Red Sea crust than proposed from the results of the latest seismic studies in the same area. The interpretation of this gravity and magnetic anomalies reveals and extremely thinned continental crust which transforms to a mixed continental-oceanic crust some 50 km from the coast line. This mixed crust is found to contain segregated basaltic bodies, normally and reversely magnetized by the ambient Earth's magnetic field. The magnetic anomaly over the Brothers Island is interpreted as related to a short 4 Ma old spreading axis. A review of the results of this investigation together with previous studies suggests three modes for the emplacement of the oceanic part of the Red Sea crust in the Egyptian Red Sea shelf. The calculated crustal model at the offshore Safaga is compared with refraction based models across Saudi Arabia and the western Atlantic.

  3. MAGSAT anomaly field inversion and interpretation for the US

    NASA Technical Reports Server (NTRS)

    Mayhew, M. A. (Principal Investigator)

    1982-01-01

    Long wavelength anomalies in the total magnetic field measured by MAGSAT over the United States and adjacent areas are inverted to an equivalent layer crustal magnetization distribution. The model is based on an equal area dipole grid at the Earth's surface. Model resolution, defined as the closest dipole spacing giving a solution having physical significance, is about 220 km for MAGSAT data in the elevation range 300-500 km. The magnetization contours correlate well with large scale tectonic provinces. A higher resolution (200 km) model based on relatively noise free synthetic "pseudodata" is also presented. Magnetic anomaly component data measured by MAGSAT is compared with synthetic anomaly component fields arising from an equivalent source dipole array at the Earth's surface generated from total field anomaly data alone. An excellent inverse correlation between apparent magnetization and heat flow in the western U.S. is demonstrated. A regional heat flow map which is presented and compared with published maps, predicts high heat flow in Nebraska and the Dakotas, suggesting the presence of a "blind" geothermal area of regional extent.

  4. Genetics of lymphatic anomalies

    PubMed Central

    Brouillard, Pascal; Boon, Laurence; Vikkula, Miikka

    2014-01-01

    Lymphatic anomalies include a variety of developmental and/or functional defects affecting the lymphatic vessels: sporadic and familial forms of primary lymphedema, secondary lymphedema, chylothorax and chylous ascites, lymphatic malformations, and overgrowth syndromes with a lymphatic component. Germline mutations have been identified in at least 20 genes that encode proteins acting around VEGFR-3 signaling but also downstream of other tyrosine kinase receptors. These mutations exert their effects via the RAS/MAPK and the PI3K/AKT pathways and explain more than a quarter of the incidence of primary lymphedema, mostly of inherited forms. More common forms may also result from multigenic effects or post-zygotic mutations. Most of the corresponding murine knockouts are homozygous lethal, while heterozygotes are healthy, which suggests differences in human and murine physiology and the influence of other factors. PMID:24590274

  5. Brain anomalies in velo-cardio-facial syndrome

    SciTech Connect

    Mitnick, R.J.; Bello, J.A.; Shprintzen, R.J.

    1994-06-15

    Magnetic resonance imaging of the brain in 11 consecutively referred patients with velo-cardio-facial syndrome (VCF) showed anomalies in nine cases including small vermis, cysts adjacent to the frontal horns, and small posterior fossa. Focal signal hyperintensities in the white matter on long TR images were also noted. The nine patients showed a variety of behavioral abnormalities including mild development delay, learning disabilities, and characteristic personality traits typical of this common multiple anomaly syndrome which has been related to a microdeletion at 22q11. Analysis of the behavorial findings showed no specific pattern related to the brain anomalies, and the patients with VCF who did not have detectable brain lesions also had behavioral abnormalities consistent with VCF. The significance of the lesions is not yet known, but the high prevalence of anomalies in this sample suggests that structural brain abnormalities are probably common in VCF. 25 refs.

  6. Geopotential field anomalies and regional tectonic features - two case studies: southern Africa and Germany

    NASA Astrophysics Data System (ADS)

    Korte, Monika; Mandea, Mioara

    2016-05-01

    Maps of magnetic and gravity field anomalies provide information about physical properties of the Earth's crust and upper mantle, helpful in understanding geological conditions and tectonic structures. Depending on data availability, whether from the ground, airborne, or from satellites, potential field anomaly maps contain information on different ranges of spatial wavelengths, roughly corresponding to sources at different depths. Focussing on magnetic data, we compare am