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ancklo / ChaosMagPy

ChaosMagPy is a simple Python package for evaluating the CHAOS geomagnetic field model and other models of Earth's magnetic field.
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Earth conductivity model #3

Open agrayver opened 5 years ago

agrayver commented 5 years ago

Hi Clemens!

I wonder in your /lib/Earth_conductivity.dat depth starts from 1 km and not from 0. Any reason for this?

ancklo commented 5 years ago

Hi Alexander,

Thanks for pointing this out. We are looking into this and I'll let you know as soon as possible.

Regards. Clemens

ancklo commented 5 years ago

Dear Alexander,

sorry for the late response.

We decided to update the conductivity model in chaosmagpy together with the next release of the CHAOS model. The new conductivity profile is your joint model:

Grayver, A. V., Munch, F. D., Kuvshinov, A. V., Khan, A., Sabaka, T. J., and Tøffner‐Clausen, L. ( 2017), Joint inversion of satellite‐detected tidal and magnetospheric signals constrains electrical conductivity and water content of the upper mantle and transition zone, Geophys. Res. Lett., 44, 6074– 6081, doi:10.1002/2017GL073446.

It will also include a top layer (conductance of 7kS) to approximate the effect of the oceans.

For more information on how we treat induction, see

Stefan Maus, Hermann Lühr, Signature of the quiet-time magnetospheric magnetic field and its electromagnetic induction in the rotating Earth, Geophysical Journal International, Volume 162, Issue 3, September 2005, Pages 755–763, https://doi.org/10.1111/j.1365-246X.2005.02691.x

We use coefficients to transform the SH expansion from GSM/SM to GEO, which we store in frequency domain. By multiplying with the Q-response that follows from the conductivity profile we approximate the inductive effect.

Clemens

agrayver commented 5 years ago

Hi Clemens, no problem. I'm glad our model is useful. Since the model goes to CMB, my recommendation is to also augment it with a finitely conducting core (e.g. 1e6 S/m). Othwerise, Weidelt's algorithm will assume a perfectly conducting layer from CMB on, which will give an unrealistic transient response at long periods (>~ 1 year).