scholarly journals Electromagnetic induction in an irregular layer overlying the earth. The 2nd paper A semi-infinite medium of finite conductivity having an undulatory surface.

1985 ◽  
Vol 37 (6) ◽  
pp. 643-657 ◽  
Author(s):  
Naoto OHSHIMAN ◽  
Tsuneji RIKITAKE
Keyword(s):  
Electromagnetic Induction ◽  
Infinite Medium ◽  
Finite Conductivity ◽  
The Earth

A note on disturbances in a layered medium containing a magnetic field

1964 ◽  
Vol 54 (6A) ◽  
pp. 1771-1777
Author(s):  
D. K. Sinha
Keyword(s):  
Magnetic Field ◽  
Free Surface ◽  
Layered Medium ◽  
Present Note ◽  
Infinite Medium ◽  
The Other ◽  
Time Dependent ◽  
The Earth ◽  
Propagation Of Waves ◽  
Initial Magnetic Field

abstract In recent years, Kaliski has contributed a series of papers on the interaction of elastic and magnetic fields and some of them, [1], [2], [3] are concerned with the propagation of waves in a semi-infinite medium either loaded or conditioned otherwise, at its free surface. Such problems, as Kaliski [1] has remarked, may have relevance in the practical seismic problem of detecting the mechanical explosions inside the earth. Moreover, their geophysical implications have also been examined by Knopoff [4[, Cagniard [5], Banos [6], and Rikitake [7]. The present note seeks to investigate disturbances in a medium consisting of two layers (one finite and the other infinite) of elastic medium intervened by a thin layer of vacuum. The vacuum is traversed by an initial magnetic field. The disturbances in the medium are assumed to have been produced by a time-dependent load on the free surface of the medium. The method of Laplace transform has been used to facilitate the solution of the problem.

scholarly journals Eigenmode analysis of ballooning perturbations in the inner magnetosphere of the Earth

2007 ◽  
Vol 25 (6) ◽  
pp. 1391-1403 ◽  
Author(s):  
A. S. Parnowski
Keyword(s):  
Stability Criterion ◽  
Geomagnetic Field ◽  
Finite Conductivity ◽  
Nonlinear Structures ◽  
Magnetic Hydrodynamics ◽  
Longitudinal Displacement ◽  
Inner Magnetosphere ◽  
Transversal Displacement ◽  
The Earth ◽  
Eigenmode Analysis

Abstract. We analyze coupled Alfvén and slow magnetosonic eigenmodes in a dipole geomagnetic field with different ionospheric conductivities in the framework of ideal magnetic hydrodynamics (MHD) with finite pressure. We use numerical and, if possible, analytical methods to describe eigenmode frequencies, growth rates and eigenfunctions. The spectrum of Alfvén and slow magnetosonic modes is discrete and equidistant. The frequencies of the first Alfvén and slow magnetosonic eigenmodes are estimated as ~1 Hz and ~1 mHz, respectively. In the case of finite conductivity, periodic and aperiodic modes are separated and their interaction analyzed. It was shown that periodic and aperiodic perturbations can mutually transform into each other. A new flute stability criterion is derived (α~4.25), which is stricter than the Gold criterion (α=20/3). Here, as usual, α=−L/p dp/dL. For flute perturbations, the deviations of transversal displacement from a constant are calculated. An approximation for longitudinal displacement is derived. We determined the position of the main longitudinal peak, which can be responsible for nonlinear structures observed by Freja. An influence of nonlinear terms in pressure is estimated as well.

scholarly journals Special issue “Studies on electromagnetic induction in the earth: recent advances”

2018 ◽  
Vol 70 (1) ◽  
Author(s):  
Weerachai Siripunvaraporn ◽  
Paul A. Bedrosian ◽  
Yuguo Li ◽  
Prasanta K. Patro ◽  
Klaus Spitzer ◽  
...  
Keyword(s):  
Electromagnetic Induction ◽  
Special Issue ◽  
The Earth ◽  
Recent Advances
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