scholarly journals Determination of upper mantle conductivity using quiet day lonospheric current

2009 ◽  
Vol 20 (1) ◽  
Author(s):  
SO Agha ◽  
FN Okeke
Keyword(s):  
Upper Mantle ◽  
Mantle Conductivity ◽  
Quiet Day

Sea Bottom EM Field of M2 Tidal to Probe Upper Mantle Conductivity

2013 ◽  
Vol 683 ◽  
pp. 828-831
Author(s):  
Yan Xu ◽  
Jun Xu ◽  
Wen Hu Zhang
Keyword(s):  
Upper Mantle ◽  
Period Range ◽  
Partial Melt ◽  
The Earth ◽  
Ionospheric Source ◽  
Sea Bottom ◽  
Mantle Conductivity ◽  
Em Field ◽  
Recent Laboratory

Recent laboratory experiments demonstrate that electrical conductivity of upper mantle (UM) minerals is greatly increased by small amounts of water or by partial melt. Determination of deep conductivity using electromagnetic (EM) methods can thus provide constraints on the presence of volatiles and melting processes in UM. Probing conductivity at UM depths requires EM data with periods of a few to one cycle per day. This is a challenging period range for EM studies due to the spatially complex ionospheric source that dominates at these periods. The idea of exploiting tidal signals for EM studies of the Earth is not new, but so far it was used only for interpretation of inland and transoceanic electric field data due to M2. Emphasis in this work is made on a discussion of sea bottom magnetic field of the same origin.

scholarly journals Quiet-day ionospheric currents and their application to upper mantle conductivity in Australia

1998 ◽  
Vol 50 (4) ◽  
pp. 347-360 ◽  
Author(s):  
W. H. Campbell ◽  
C. E. Barton ◽  
F. H. Chamalaun ◽  
W. Welsh
Keyword(s):  
Upper Mantle ◽  
Ionospheric Currents ◽  
Mantle Conductivity ◽  
Quiet Day

Magneto-telluric determination of upper mantle conductivity structure at Victoria, British Columbia

1968 ◽  
Vol 5 (5) ◽  
pp. 1209-1220 ◽  
Author(s):  
B. Caner ◽  
D. R. Auld
Keyword(s):  
Spectral Analysis ◽  
Upper Mantle ◽  
High Resistivity ◽  
Conducting Layer ◽  
Frequency Range ◽  
Tidal Effects ◽  
Conductivity Structure ◽  
Wide Range ◽  
Mantle Conductivity

Magneto-telluric data were obtained at Victoria over a very wide range of periods (2 s to 86 400 s). Only the data up to 15 000 s periods were used for interpretation of conductivity structure, since telluric data at longer periods were dominated by ocean-tidal effects; spectral analysis of one year's data was used to demonstrate the tidal effects. The telluric signals are strongly polarized in the whole frequency range, indicating an anisotropy in surface conductivity.The data indicate the existence of a finite conducting layer 10 ± 3 km thick and resistivity 100–125 ohm-meters, at a depth of 65 ± 5 km. A high resistivity zone (of the order of 4000–5000 ohm-meters) lies below this layer. There is no evidence for any further conducting zones down to a depth of at least 750 km.

Inversion of the satellite observations of the tidally induced magnetic field in terms of 3-D upper-mantle electrical conductivity: Method and synthetic tests

2021 ◽  
Author(s):  
Libor Šachl ◽  
Jakub Velímský ◽  
Javier Fullea
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Upper Mantle ◽  
Spherical Harmonic ◽  
Model Space ◽  
Conductivity Method ◽  
Satellite Gravity ◽  
Compositional Model ◽  
Mantle Conductivity ◽  
The Impact

<p><span><span>We have developed and tested a new frequency-domain, spherical harmonic-finite element approach to the inverse problem of global electromagnetic (EM) induction. It is based on the quasi-Newton minimization of data misfit and regularization, and uses the adjoint approach for fast calculation of misfit gradients in the model space. Thus, it allows for an effective inversion of satellite-observed magnetic field induced by tidally driven flows in the Earth's oceans in terms of 3-D structure of the electrical conductivity in the upper mantle.</span></span><span><span> Before proceeding to the inversion of Swarm-derived models of tidal magnetic signatures, we have performed a series of </span></span><span><span>parametric studies</span></span><span><span>, using a 3-D conductivity model WINTERC-e as a testbed.</span></span></p><p><span>The WINTERC-e model has been derived using state-of-the-art laboratory conductivity measurements of mantle minerals, and thermal and compositional model of the lithosphere and upper mantle WINTERC-grav. The latter model is based on the inversion of global surface waveforms, satellite gravity and gradiometry measurements, surface elevation, and heat flow data </span><span><span>in a thermodynamically self-consistent framework. </span></span><span><span>Therefore, the WINTERC-e model, independent of any EM data, represents an ideal target for synthetic tests of the 3-D EM inversion.</span></span><span> </span></p><p><span><span>We tested the impact of </span></span><span><span>the </span></span><span><span>satellite </span></span><span><span>altitude</span></span><span><span>, </span></span><span><span>the truncation degree of the </span></span><span><span>spherical-harmonic </span></span><span><span>expansion of the tidal signals, the random</span></span><span><span> noise in data</span></span><span><span>,</span></span><span> </span><span><span>and </span></span><span><span>of the </span></span><span><span>sub-</span></span><span><span>continental conductivity</span></span><span> </span><span><span>on the </span></span><span><span>ability to recover the sub-oceanic upper-mantle conductivity structure.</span></span><span><span> We </span></span><span><span>demonstrate </span></span><span><span>that </span></span><span><span>with </span></span><span><span>suitable regularization </span></span><span><span>we</span></span><span> </span><span><span>can successfully reconstruct the 3D upper-mantle conductivity below world oceans.</span></span></p>

scholarly journals Experimental determination of the viscosity of Na2CO3 melt between 1.7 and 4.6 GPa at 1200–1700 °C: Implications for the rheology of carbonatite magmas in the Earth's upper mantle

2018 ◽  
Vol 501 ◽  
pp. 19-25 ◽  
Author(s):  
Vincenzo Stagno ◽  
Veronica Stopponi ◽  
Yoshio Kono ◽  
Craig E. Manning ◽  
Tetsuo Irifune
Keyword(s):  
Experimental Determination ◽  
Upper Mantle

scholarly journals MODELING CRITICAL FREQUENCY OF IONOSPHERE D-LAYER AT MINIMUM AND MAXIMUM OF THE SOLAR CYCLE 22WITH IRI-2016

2021 ◽  
Vol 9 (08) ◽  
pp. 960-965
Author(s):  
Nakolemda Roger ◽  
◽  
Nanema Emmanuel ◽  
Sawadogo Gedeon ◽  
◽  
...  
Keyword(s):  
Solar Cycle ◽  
Temporal Variability ◽  
Critical Frequency ◽  
Temporal Variations ◽  
Minimum Phase ◽  
Radio Waves ◽  
Iri Model ◽  
Geographical Position ◽  
Quiet Day

One of the interests of the study of the ionosphere lies in its importance for the transmission of radio waves in telecommunications. The ionospherebehaves as an obstacle to the passage of waves. Thus, the signals of short wavelengths are reflected by the F layer or the upper part of the sublayer E, while theD-layeris the seat of the reflection of low-frequencywaves. The presentstudyinvestigates the temporal variability of the criticalfrequency of the D-layer (for) using the 2016 version of the International Reference Ionosphere (IRI) model under quiet day conditions during at maximum and minimum phase of solar cycle 22. The workisconductedat the Ouagadougou station, located in West Africa. The methodology of the workadopted for the determination of the parameter foDisbased on the calculation of the monthlyhourlyaverages of this variable obtainedwith the help of the model during the monthsthatcharacterize the seasons. The resultsobtained for the parameter for as a function of time during the minimum and maximum of the solar cycle 22 have been presented. The seasonal and temporal variations of the criticalfrequency of the ionosphereD-layer show that the foD values are lower during a minimum of the solar cycle and present maximum values at the Zenith (1200 TL) at a minimum and maximum. Theseresultsalsorevealthatthisparameter varies with time, season, and geographical position. The results of thisstudy show a criticalfrequencybelow 1 MHz during both phases of the solar cycle.

scholarly journals Upper mantle conductivity structure of the back-arc region beneath northeastern China

2001 ◽  
Vol 28 (19) ◽  
pp. 3773-3776 ◽  
Author(s):  
Masahiro Ichiki ◽  
Makoto Uyeshima ◽  
Hisashi Utada ◽  
Zhao Guoze ◽  
Tang Ji ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Northeastern China ◽  
Conductivity Structure ◽  
Mantle Conductivity ◽  
Back Arc
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