Schmucker-Weidelt Lecture Notes, Aarhus, 1975 - MTNet

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below can neither enter nor leave this body.
The inducing field is the normal field HA between zl and z 2 3
regarded as uniform. For simplicity it is assumed that the nor-
mal structure between z=0 and z represents a "thin sheet" of the
1
conductance T ~ . Then the attenuation of H1 with respect to the
n
normal field H at the surface zz0 is given by
n
as thin-sheet induction parameter (Sect.9'3 . . and Appendix to 7.3).
Three aspects of the arising inductiorl probl.em have -to be con-
sidered: (i) the local induction by H' within the body, (ii) the
n
elec-tromagnetic coupling of this body with the normal subst~uc-Lure
below z (iii) the coupling of the body with the surface ccveri;bove
2'
In order to make problem (i) solvable in a straightforrgard manner
uniform bodies of simple shape such as spheres and horizon1:al.
cylinders of infinite length have -to be selected, The anomalous
field due to -the induc-tion in these bodies is of fr,equ.ency.-indepen-
dent geometry. This fact permits si.lnple solutions of The inverse
prohl.em as seen below.
Consider the case of a horizontal cylinder of infi,nite length, the
radius R and -the conductivity u its axis is parallel to x and
z;
intersects the (y, z)-plane at the point (0, zo). The normal horizon-
tal field is. parallel to y and produces hy i.nduction curren-ts which
flow parall.el to x in .the upper halve and anti-parallel to x in "ilie
lower halve of the cylinder. Their magnetic field outside the cy-
linder is -the field of a central 2-dimenstonal di.pole of the monient