Magnetotelluric measurements in La Malbaie area (Quebec): the anomalous vertical magnetic field

1985 ◽  
Vol 22 (10) ◽  
pp. 1530-1536 ◽  
Author(s):  
Michel Chouteau
Keyword(s):  
Magnetic Field ◽  
Impact Crater ◽  
Transfer Functions ◽  
Vertical Magnetic Field ◽  
Magnetotelluric Soundings ◽  
Vertical Transfer ◽  
Conductive Zone ◽  
Single Station ◽  
Induction Arrows ◽  
Characteristic Features

Magnetotelluric soundings were recorded in 1980–1981 at Ste-Mathilde near La Malbaie, Quebec for periods of 0.04–200 s. The present study deals only with single-station vertical transfer functions. Those functions show very characteristic features in their responses versus period. Of particular interest is a large in-phase (P) peak corresponding to a quadrature (Q) minimum between 0.1 and 0.2 s. For those periods, induction arrows indicate no obvious correlation between the anomalous vertical magnetic field (Z) and the conductive zone of Ste-Mathilde. Rather, they point toward the Malbaie River to the southwest of the survey zone. A possible model for the source of the vertical magnetic field is a shallow N130°E vertical dyke-type conductor, the top of which is some 1400 m under the Malbaie River valley. An interpretation could well be that it is one of the major graben faults related to the meteoritic impact crater of Charlevoix.

Extremal bias coupling in magnetotellurics

Geophysics ◽  
1984 ◽  
Vol 49 (11) ◽  
pp. 1968-1978 ◽  
Author(s):  
L. B. Pedersen ◽  
M. Svennekjaer
Keyword(s):  
Magnetic Field ◽  
Linear System ◽  
Rotation Angle ◽  
Impedance Tensor ◽  
Vertical Magnetic Field ◽  
Electrical Field ◽  
Horizontal Magnetic Field ◽  
Single Station ◽  
Polarization Characteristics ◽  
Set Up

Bias effects due to uncorrelated noise on electrical and magnetic channels are cast into a quantitative framework which allows for an immediate conservative judgment of impedance tensor quality from a single station set up. The horizontal magnetic field is regarded as input to a linear system with the horizontal electrical field and the vertical magnetic field as outputs. The coherence between inputs, the predicted coherence between outputs and inputs, and the polarization characteristics of the inputs, determine the extremal bias effects. Exact expressions for impedance tensor elements and tipper elements are given. Moreover, rotation angle of principal impedance direction, skew, and ellipticity are calculated. Finally, we study some practical examples that show some of the characteristics predicted by our model.

scholarly journals Overstable rotating convection in the presence of a vertical magnetic field

2021 ◽  
Vol 33 (3) ◽  
pp. 034130
Author(s):  
Ankan Banerjee ◽  
Manojit Ghosh ◽  
Lekha Sharma ◽  
Pinaki Pal
Keyword(s):  
Magnetic Field ◽  
Vertical Magnetic Field ◽  
Rotating Convection

Effects of a Vertical Magnetic Field on Particle Confinement in a Magnetized Plasma Torus

2004 ◽  
Vol 93 (16) ◽  
Author(s):  
S. H. Müller ◽  
A. Fasoli ◽  
B. Labit ◽  
M. McGrath ◽  
M. Podestà ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetized Plasma ◽  
Vertical Magnetic Field ◽  
Plasma Torus ◽  
Particle Confinement

Effect of magnetic field on parametrically driven surface waves

2006 ◽  
Vol 463 (2079) ◽  
pp. 711-722 ◽  
Author(s):  
Supriyo Paul ◽  
Krishna Kumar
Keyword(s):  
Magnetic Field ◽  
Surface Waves ◽  
Liquid Metals ◽  
Tricritical Point ◽  
Thin Layers ◽  
Vertical Magnetic Field ◽  
Harmonic Solution ◽  
Chandrasekhar Number ◽  
The Magnetic Field ◽  
Primary Instability

Stability analysis of parametrically driven surface waves in liquid metals in the presence of a uniform vertical magnetic field is presented. Floquet analysis gives various subharmonic and harmonic instability zones. The magnetic field stabilizes the onset of parametrically excited surface waves. The minima of all the instability zones are raised by a different amount as the Chandrasekhar number is raised. The increase in the magnetic field leads to a series of bicritical points at a primary instability in thin layers of a liquid metal. The bicritical points involve one subharmonic and another harmonic solution of different wavenumbers. A tricritical point may also be triggered as a primary instability by tuning the magnetic field.

scholarly journals ELECTROMAGNETIC FIELDS OF CHARGED AND MAGNETIZED CYLINDRICAL CONDUCTORS IN NUT SPACE

2005 ◽  
Vol 14 (03n04) ◽  
pp. 687-695 ◽  
Author(s):  
B. J. AHMEDOV ◽  
A. V. KHUGAEV ◽  
N. I. RAKHMATOV
Keyword(s):  
Magnetic Field ◽  
Gravitational Field ◽  
Electromagnetic Fields ◽  
Electric Charge ◽  
Maxwell Equations ◽  
Analytic Solutions ◽  
Vertical Magnetic Field ◽  
General Relativistic ◽  
Azimuthal Current ◽  
Cylindrical Conductors

We present analytic solutions of Maxwell equations for infinitely long cylindrical conductors with nonvanishing electric charge and currents in the external background spacetime of a line gravitomagnetic monopole. It has been shown that vertical magnetic field arising around cylindrical conducting shell carrying azimuthal current will be modified by the gravitational field of NUT source. We obtain that the purely general relativistic magnetic field which has no Newtonian analog will be produced around charged gravitomagnetic monopole.

The Thermal-Convective Instability in a Stellar Atmosphere with Rotation and Hall Effects

1974 ◽  
Vol 29 (6) ◽  
pp. 867-869 ◽  
Author(s):  
R. C. Sharma
Keyword(s):  
Magnetic Field ◽  
Convective Instability ◽  
Stellar Atmosphere ◽  
Vertical Magnetic Field ◽  
Hall Effects ◽  
Monotonic Instability

The problem of thermal-convective instability of a stellar atmosphere is considered to include the effects due to rotation and Hall currents in the presence of a uniform vertical magnetic field The criterion for monotonic instability is found to be unchanged by the presence of rotation and Hall effects.

scholarly journals Properties of the inner penumbral boundary and temporal evolution of a decaying sunspot

2018 ◽  
Vol 620 ◽  
pp. A191 ◽  
Author(s):  
M. Benko ◽  
S. J. González Manrique ◽  
H. Balthasar ◽  
P. Gömöry ◽  
C. Kuckein ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Temporal Evolution ◽  
Vertical Component ◽  
Field Vector ◽  
Linear Increase ◽  
Vertical Magnetic Field ◽  
Magnetic Diffusion ◽  
The Magnetic Field ◽  
Linear Decay

Context. It has been empirically determined that the umbra-penumbra boundaries of stable sunspots are characterized by a constant value of the vertical magnetic field. Aims. We analyzed the evolution of the photospheric magnetic field properties of a decaying sunspot belonging to NOAA 11277 between August 28–September 3, 2011. The observations were acquired with the spectropolarimeter on-board of the Hinode satellite. We aim to prove the validity of the constant vertical magnetic-field boundary between the umbra and penumbra in decaying sunspots. Methods. A spectral-line inversion technique was used to infer the magnetic field vector from the full-Stokes profiles. In total, eight maps were inverted and the variation of the magnetic properties in time were quantified using linear or quadratic fits. Results. We find a linear decay of the umbral vertical magnetic field, magnetic flux, and area. The penumbra showed a linear increase of the vertical magnetic field and a sharp decay of the magnetic flux. In addition, the penumbral area quadratically decayed. The vertical component of the magnetic field is weaker on the umbra-penumbra boundary of the studied decaying sunspot compared to stable sunspots. Its value seem to be steadily decreasing during the decay phase. Moreover, at any time of the sunspot decay shown, the inner penumbra boundary does not match with a constant value of the vertical magnetic field, contrary to what is seen in stable sunspots. Conclusions. During the decaying phase of the studied sunspot, the umbra does not have a sufficiently strong vertical component of the magnetic field and is thus unstable and prone to be disintegrated by convection or magnetic diffusion. No constant value of the vertical magnetic field is found for the inner penumbral boundary.

Instability and transition of a vertical ascension or fall of a free sphere affected by a vertical magnetic field

2018 ◽  
Vol 859 ◽  
pp. 33-48 ◽  
Author(s):  
Jun-Hua Pan ◽  
Nian-Mei Zhang ◽  
Ming-Jiu Ni
Keyword(s):  
Magnetic Field ◽  
Interaction Parameter ◽  
Scaling Law ◽  
Density Ratio ◽  
Vertical Magnetic Field ◽  
Streamwise Vorticity ◽  
Close Relationship ◽  
Wake Patterns ◽  
The Magnetic Field ◽  
Solid System

When the Galileo number is below the first bifurcation, the instability and transition of a vertical ascension or the fall of a free sphere affected by a vertical magnetic field are investigated numerically. A compact model is used to explain that the magnetic field can destabilize the fluid–solid system. When the interaction parameter exceeds a critical value, the sphere trajectory is transitioned from a steady vertical trajectory to a steady oblique one. Furthermore, the trajectory will remain vertical at a sufficiently large magnetic field because of a double effect of the magnetic field on the fluid–solid system. Under the influence of an external vertical magnetic field, four wake patterns at the rear of the sphere are found and the physical behaviour of the free sphere is independent of the density ratio. The wake or trajectory of the free sphere is only determined by the Galileo number $G$ and the interaction parameter $N$. A close relationship between the streamwise vorticity and the sphere motion is found. An interesting ‘agglomeration phenomenon’ is also found, which shows that the vertical velocities are agglomerated into a point for a certain magnetic field regardless of the Galileo number and satisfy a scaling law $V_{z}\sim N^{-1/4}$, when $N>1$. The principal results of the present work are summarized in a map of regimes in the $\{G,N\}$ plane.

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