scholarly journals The Magnetic Signatures of the M 2 , N 2 , and O 1 Oceanic Tides Observed in Swarm and CHAMP Satellite Magnetic Data

2019 ◽  
Vol 46 (8) ◽  
pp. 4230-4238 ◽  
Author(s):  
Alexander V. Grayver ◽  
Nils Olsen
Keyword(s):  
Magnetic Data ◽  
Champ Satellite ◽  
Magnetic Signatures ◽  
Oceanic Tides

scholarly journals Improving and testing the empirical equatorial electrojet model with CHAMP satellite data

2004 ◽  
Vol 22 (9) ◽  
pp. 3323-3333 ◽  
Author(s):  
V. Doumouya ◽  
Y. Cohen
Keyword(s):  
Equatorial Electrojet ◽  
Ground Level ◽  
Longitudinal Variation ◽  
Equatorial Station ◽  
Champ Satellite ◽  
Magnetic Effects ◽  
Level Data ◽  
The Pacific ◽  
Magnetic Signatures ◽  
Data Points

Abstract. The longitudinal variation of the Equatorial Electrojet (EEJ) intensity has been revised including data from the equatorial station of Baclieu (Vietnam), where an unexpected enhancement of the EEJ magnetic effects is observed. The features of this longitudinal variation were also obtained with the CHAMP satellite, except in the Pacific and Atlantic Oceans, where no ground level data points were available.The EEJ magnetic signatures recorded on board the CHAMP satellite have been isolated for 325 passes in different longitude sectors around local noon. The results have been compared with the EEJ magnetic effects computed using the Empirical Equatorial Electrojet Model (3EM) proposed by Doumouya et al. (2003). The modeled EEJ magnetic effects are generally in good agreement with CHAMP observed EEJ magnetic signatures.

scholarly journals A model for estimating the relation between the Hall to Pedersen conductance ratio and ground magnetic data derived from CHAMP satellite statistics

2007 ◽  
Vol 25 (3) ◽  
pp. 721-736 ◽  
Author(s):  
L. Juusola ◽  
O. Amm ◽  
K. Kauristie ◽  
A. Viljanen
Keyword(s):  
Current Density ◽  
Geomagnetic Latitude ◽  
Magnetic Data ◽  
Equivalent Current ◽  
Champ Satellite ◽  
Long Time ◽  
Conductance Ratio ◽  
Ground Magnetic ◽  
Eiscat Radar ◽  
Magnetic Satellite

Abstract. The goal of this study is to find a way to statistically estimate the Hall to Pedersen conductance ratio α from ground magnetic data. We use vector magnetic data from the CHAMP satellite to derive this relation. α is attained from magnetic satellite data using the 1-D Spherical Elementary Current Systems (SECS). The ionospheric equivalent current density can either be computed from ground or satellite magnetic data. Under the required 1-D assumption, these two approaches are shown to be equal, which leads to the advantage that the statistics are not restricted to areas covered by ground data. Unlike other methods, using magnetic satellite measurements to determine α ensures reliable data over long time sequences. The statistical study, comprising over 6000 passes between 55° and 76.5° northern geomagnetic latitude during 2001 and 2002, is carried out employing data from the CHAMP satellite. The data are binned according to activity and season. In agreement with earlier studies, values between 1 and 3 are typically found for α. Good compatibility is found, when α attained from CHAMP data is compared with EISCAT radar measurements. The results make it possible to estimate α from the east-west equivalent current density Jφ; [A/km]: α=2.07/(36.54/|Jφ|+1) for Jφ<0 (westward) and α=1.73/(14.79/|Jφ+1) for Jφ0 (eastward). Using the same data, statistics of ionospheric and field-aligned current densities as a function of geomagnetic latitude and MLT are included. These are binned with respect to activity, season and IMF BZ and BY. For the first time, all three current density components are simultaneously studied this way on a comparable spatial scale. With increasing activity, the enhancement and the equatorward expansion of the electrojets and the R1 and R2 currents is observed, and in the nightside, possible indications of a Cowling channel appear. During southward IMF BZ, the electrojets and the R1 and R2 currents are stronger and clearer than during northward BZ. IMF BY affects the orientation of the pattern.

scholarly journals Exploiting Aeromagnetic and Gravity Data Interpretation to Delineate Massif Deposits of Rehamna Area (Western Meseta-Morocco)

2021 ◽  
Vol 54 (2C) ◽  
pp. 13-28
Author(s):  
Kawtar Benyas
Keyword(s):  
Gravity Data ◽  
Precious Metals ◽  
Data Interpretation ◽  
Structural Features ◽  
Magnetic Data ◽  
Gravity Gradient ◽  
Horizontal Gradient ◽  
Geological Structures ◽  
Magnetic Signatures ◽  
First Vertical Derivative

The analysis of the magnetic signatures and gravity gradient values of the Rehamna Massif south of the Moroccan Western Meseta by using Geosoft Oasis Montaj 7.0.1 software, allowed us to detect several useful anomalies to be exploited and which are related to magmatic bodies and structural features within the study area. These data were analyzed by applying several techniques, including the horizontal gradient filters combined with the first vertical derivative. Subsurface structures; such as geological boundaries, faults, dykes and folds, were visualized as lineaments on geophysical maps, then results were compared with structural features provided by previous studies in the region. Thus, the Rehamna Massif structural map shows sets of linear features which may represent faults or boundaries of geological structures, which can be either faults or boundaries of geological structures, and they are mostly oriented in the directions: N-S, NNE-SSW, NE-SW, E-W with the predominance of the NNE-SSW to NE-SW directions. In addition, the super position of the minerals bearing beds or formations were distinguished from gravity and magnetic data processing results. Some of the recognized anomalies are related to the existence of precious metals which belong to the granitic bodies within the study area.

The magnetic signatures of oceanic tides in satellite data: A virtual-observatory approach

2020 ◽  
Author(s):  
Jakub Velímský ◽  
Magnus D. Hammer ◽  
Christopher C. Finlay
Keyword(s):  
Harmonic Polynomial ◽  
Local Error ◽  
Virtual Observatory ◽  
Quiet Time ◽  
Local Approach ◽  
Initial Report ◽  
Polynomial Coefficients ◽  
Magnetic Signatures ◽  
Scalar Magnetic Potential ◽  
Oceanic Tides

&lt;p&gt;The magnetic signatures of the M&lt;sub&gt;2&lt;/sub&gt;, and more recently also the N&lt;sub&gt;2&lt;/sub&gt;, and O&lt;sub&gt;1&lt;/sub&gt; oceanic tides have been successfully extracted from satellite observations (Grayver &amp; Olsen, 2019). The traditional method uses the spatial representation of the tidal signals by spherical harmonics. Here we present an alternative approach based on the concept of virtual observatories, motivated by similar development in the analysis of the core field (Mandea &amp; Olsen 2006). All quiet-time, night-side vector magnetic field values observed by the satellite(s) in the proximity of a selected virtual observatory are parameterized by a scalar magnetic potential represented by a cubic harmonic polynomial in a local Cartesian coordinate system. The time-dependence of the polynomial coefficients is constrained by selected tidal frequency, taking into account also the phase and amplitude corrections. The local approach offers several advantages over the use of the global spherical-harmonic base. The disturbances from external field in the polar areas have no impact on the inversion at lower latitudes, and local error estimates can be also provided. In this initial report, we will explore the possibilities of the new technique in terms of resolution, the combination of datasets from multiple satellites and the use of NS and EW field differences from the Swarm A-C pair.&lt;/p&gt;

scholarly journals Regular daily variations in satellite magnetic total intensity data

2007 ◽  
Vol 25 (10) ◽  
pp. 2167-2174 ◽  
Author(s):  
J. P. R. Turner ◽  
D. E. Winch ◽  
D. J. Ivers ◽  
R. J. Stening
Keyword(s):  
Local Time ◽  
Field Measurements ◽  
Mean Value ◽  
Low Earth Orbit ◽  
Magnetic Data ◽  
Spherical Harmonic Analysis ◽  
Quiet Time ◽  
Champ Satellite ◽  
Daily Variations ◽  
Low Earth Orbit Satellites

Abstract. Regular magnetic daily quiet time (Sq) variations in total intensity of about 30 nT amplitude are determined in Universal Time (UT) from satellite magnetic field measurements. The CHAMP satellite traverses all hours of local time in 132 days and the Sq variations in total intensity are therefore calculated as an average over the 132 days for each hour of UT. Results are compared with the Sq daily variations in total intensity for the region above the ionosphere calculated from Malin's (1973) spherical harmonic analysis of the Sq Fourier coefficients for hourly mean value magnetic data from a global distribution of ground-based magnetic observatories. From the reasonable agreement between the two calculations, we conclude that low-Earth orbit satellites that traverse all hours of local time can determine Sq variations in total intensity above the ionosphere.

scholarly journals Magnetic signatures and conjugate features of low-latitude plasma blobs as observed by the CHAMP satellite

2008 ◽  
Vol 113 (A9) ◽  
pp. n/a-n/a ◽  
Author(s):  
Jaeheung Park ◽  
Claudia Stolle ◽  
Hermann Lühr ◽  
Martin Rother ◽  
Shin-Yi Su ◽  
...  
Keyword(s):  
Low Latitude ◽  
Champ Satellite ◽  
Magnetic Signatures ◽  
Plasma Blobs

scholarly journals Wavelet characterization of external magnetic sources as observed by CHAMP satellite: evidence for unmodelled signals in geomagnetic field models

2013 ◽  
Vol 192 (3) ◽  
pp. 946-950 ◽  
Author(s):  
Praveen Kunagu ◽  
Georgios Balasis ◽  
Vincent Lesur ◽  
E. Chandrasekhar ◽  
C. Papadimitriou
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Induction ◽  
External Source ◽  
Source Model ◽  
Magnetic Data ◽  
Satellite Mission ◽  
Champ Satellite ◽  
Geomagnetic Field Models ◽  
Source Signals

Abstract We apply continuous wavelet transform technique to the full decade (2001–2010) of CHAMP vector magnetic data from 55417 tracks, to search for evidences of external source field signatures that are either misunderstood or ignored in modern magnetic field models. We show that satellite magnetic time-series, after subtracting the main and lithospheric field contributions, exhibit several external source signals. Other than the diurnal, 27-day, and annual periodicities, we also have observed the 210-day periodicity, in the external magnetic field. Central to these observations is the local time dependency of 27-day variations, which suggests that the purely zonal source model, generally considered for the estimation of electromagnetic induction response is inadequate. We discuss the origin and characteristics of 210-day periodicity, although its geophysical significance needs to be fully ascertained. A better understanding of the external fields as seen at satellite altitude is a prerequisite for an optimum exploitation of Swarm multi-satellite mission, which is scheduled for launch in 2013.

scholarly journals High-Resolution Late Devonian Magnetostratigraphy From the Canning Basin, Western Australia: A Re-Evaluation

2021 ◽  
Vol 9 ◽  
Author(s):  
Theodore Green ◽  
Sarah P. Slotznick ◽  
Plinio Jaqueto ◽  
Timothy D. Raub ◽  
Eric Tohver ◽  
...  
Keyword(s):  
Western Australia ◽  
Mass Extinction ◽  
Critical Time ◽  
Paleomagnetic Data ◽  
Magnetic Data ◽  
Late Devonian ◽  
Sea Level Changes ◽  
Canning Basin ◽  
Time Period ◽  
Magnetic Signatures

Late Devonian time was a period of rapid upheaval in the Earth system, including climate change, sea level changes, widespread ocean anoxia, and the Frasnian-Famennian mass extinction; the cause(s) of these changes remain(s) uncertain. The Lennard Shelf of the Canning Basin in Western Australia contains carbonate reef sections spanning much of the Late Devonian Epoch and has been sampled for paleomagnetic analysis with studies by Hansma and colleagues in 2015 and Playton and colleagues in 2016. However, previous paleomagnetic directions were scattered and their use for magnetostratigraphy has been questioned. Here, rock magnetic data and magnetostratigraphy for a late Devonian drill-core from the Lennard Shelf were analyzed. Three magnetostratigraphic interpretations were made using different paleopoles that showed good correlation with each other and the earlier interpretations by Playton and colleagues in 2016. Additionally, the rock magnetic data revealed the samples contain various mixtures of detrital and diagenetic minerals, the former of which should be viable recorders of primary magnetic signatures. Even in samples with these detrital phases, paleomagnetic data were often noisy and produced ambiguous polarity assignments, likely due to the anomalously weak Devonian field. Because of this ambiguity and the absence of a robust paleopole, broader correlations for this critical time-period will be difficult without additional paleomagnetic data from the late Devonian Period. Expanded data for this interval could eventually shed light on the timing, causes, and rates of the Frasnian-Famennian mass extinction and other environmental shifts in the late Devonian Epoch.

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