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geoscixyz / em

Electromagnetic methods in geophysics - open educational resources.
http://em.geosci.xyz
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Update skindepth.rst #563

Open PAULGOYES opened 3 years ago

PAULGOYES commented 3 years ago

add minus to beta in A(z)

PAULGOYES commented 3 years ago

please, maybe it will be more clear if we add some comment like "in this derivation is used the "z positive is up" convention". Something like this: For a downgoing planewave, where is used the "z positive is up" convention, the attenuation formula is given by: ...

PAULGOYES commented 3 years ago

Hello @thast, I spoke with my students and I found why they are confused. This is because in Fig. 44 the convention is "depth is negative in the subsurface" so, it does not need the minus in the attenuation equation. However, if you check the first experiment in "Response of a layered Earth to a plane wave" you can see this: In the subsurface the depth is positive, and "in the air media" has depth-negative. In addition, the attenuation equation on the same page (see eq 422) has the minus.