Dear all, let me share these ideas.

1) The concept of gravitational admittance is a concept associate with the term isostasy “equal standing”: the lighter crus is floating on the dense underlying mantle. Following the book "Isostasy and flexure of the lithosphere" (A.B: Watts, Cambridge University Press, 2001):

2) Isostasy is a concept that is fundamental to the Earth Sciences. It is based on the idea that the light curst is floating on the denser underlying mantle. Isostasy is an ideal state: a condition of rest that the crust and mantle would tend to in the absence of disturbing forces. The waxing and waning of ice sheets, erosion, sedimentation, and extrusive volcanism are some of the Earth´s surface processes that disturb isostasy. The way that the crust and mantle respond to these disturbances constrains the long-term physical properties of the lithosphere and helps us understand more complex geodynamical phenomena such as mountain building, sedimentary basin formation, and the break-up of continents and the formation of new ocean basins.

3) Gravitational Admittance

Admittance is the set of coefficients (as a function of wavenumber or wavelength of the topographic load) to scale topography, H(k) to gravity anomaly, Δg(k).

Admittance: Z(k)=Δg(k)/Η(k)

Z(k) depends on the isostatic or flexural model selected (see figure below, from Watts, 2001), so it requires certain assumptions about the state of loads on, in, and at the base of the lithosphere [Forsyth, 1985].

4) For example, a solution for the free air admittance of surface loading that is flexurally compensated: Z(k) = Δg (k)/Η(k) Δg(k) = 2π Gρc e-kε(1-Φ(k) e-kt) H(k) Z(k) = 2πG ρc e-k ε(1-Φ(k) e-kt) Where: Z(k) is the Gravitational Admittance; ε is the elevation of the observation (i.e. the surface elevation or the altitude of an airborne observation) and where t is the mean crustal thickness; and where Φ(k)=[ Dk4/(rm-rc)g+1 ] -1.

Therefore, if Mr. Rana Day is study his PhD in Planetary Geophysics, you must to understand that the Gravitational Admittance is a critical concept and play a dramatical role in the concept of flexural rigidity, or effective elastic thickness. 5) The flexural rigidity, D, is hidden in the scaling of topographic signals to gravity signals but is also obscured by assumptions regarding crustal thickness and crust and mantle densities.

And D provides information on the way that geological loads are supported not only by the Earth´s crust and mantle, but also on the Moon, Mercury, Mars and Venus, the Interior Planets, that will help you to understand better its geodynamical evolution (Planetary Geophysics).

Best wishes, Mario E. Sigismondi

Actually It's not the definition, I know and understand both of the definitions used in those two fields. I was basically searching for an analogy between those two definitions, whether such an analogy exists or just it's an academic jargon reserved particularly for both the fields.

Gravitational admittance may be the increase in density of gravitational flux lines per "thing that causes gravitational flux" (material), so may have the same underlying meaning as the increase in current density (charge flux) per electric field (thing that causes charge flux).

The term admittance called the reverse of impedance in alternative current or reverse of resistance in direct current.

You can search what means resistance for understanding all.

That's a very interesting question about the definition of the admittance with the respect of another field. I am familiar with the electrical definition of admittance of materials but i am not familiar with the physics definition. but dam interested to know

In the field of electrical quantities, and pursuing the ease a conductor will allow Current through it when applied with potentials of different values at its various point, depends on it's admittance and conductivity, but with regards to the admittance in geophysics, the same scenario can be considered, on how much altitude of a land form could could affect, increasingly or decreasingly the gravitational pull. This same parameter at different fields of study, have the same explanatory point of behavior, but different dimensional quantities

Yes, that is true,I am agree with Samuel for his approach in term of admittance definition.

I'm agree with Prof.Biliksuun, and I assert that in electric domains: the real part of Admittance is Conductance, where Susceptance is the imaginary part. Its reciprocal is Impedance.

Biliksuun Samuel I. A. Ethman Moaad Aboumalik I would like to draw your attention to my previous post, which you appear not to have read.

Gravitational admittance may be the increase in density of gravitational flux lines per "thing that causes gravitational flux" (material), so may have the same underlying meaning as the increase in current density (charge flux) per electric field (thing that causes charge flux).

Dear Prof. Malcolm, very interesting what you posted.. and according to the different explanation about the term of "Admittance", including your vision, we can say it depends on domain of application, and we consider it as a generic term required for the acquisition of charges (thermal, electrical, fluidic, magnetic).

Dear all, let me share these ideas.

1) The concept of gravitational admittance is a concept associate with the term isostasy “equal standing”: the lighter crus is floating on the dense underlying mantle. Following the book "Isostasy and flexure of the lithosphere" (A.B: Watts, Cambridge University Press, 2001):

2) Isostasy is a concept that is fundamental to the Earth Sciences. It is based on the idea that the light curst is floating on the denser underlying mantle. Isostasy is an ideal state: a condition of rest that the crust and mantle would tend to in the absence of disturbing forces. The waxing and waning of ice sheets, erosion, sedimentation, and extrusive volcanism are some of the Earth´s surface processes that disturb isostasy. The way that the crust and mantle respond to these disturbances constrains the long-term physical properties of the lithosphere and helps us understand more complex geodynamical phenomena such as mountain building, sedimentary basin formation, and the break-up of continents and the formation of new ocean basins.

3) Gravitational Admittance

Admittance is the set of coefficients (as a function of wavenumber or wavelength of the topographic load) to scale topography, H(k) to gravity anomaly, Δg(k).

Admittance: Z(k)=Δg(k)/Η(k)

Z(k) depends on the isostatic or flexural model selected (see figure below, from Watts, 2001), so it requires certain assumptions about the state of loads on, in, and at the base of the lithosphere [Forsyth, 1985].

4) For example, a solution for the free air admittance of surface loading that is flexurally compensated: Z(k) = Δg (k)/Η(k) Δg(k) = 2π Gρc e-kε(1-Φ(k) e-kt) H(k) Z(k) = 2πG ρc e-k ε(1-Φ(k) e-kt) Where: Z(k) is the Gravitational Admittance; ε is the elevation of the observation (i.e. the surface elevation or the altitude of an airborne observation) and where t is the mean crustal thickness; and where Φ(k)=[ Dk4/(rm-rc)g+1 ] -1.

Therefore, if Mr. Rana Day is study his PhD in Planetary Geophysics, you must to understand that the Gravitational Admittance is a critical concept and play a dramatical role in the concept of flexural rigidity, or effective elastic thickness. 5) The flexural rigidity, D, is hidden in the scaling of topographic signals to gravity signals but is also obscured by assumptions regarding crustal thickness and crust and mantle densities.

And D provides information on the way that geological loads are supported not only by the Earth´s crust and mantle, but also on the Moon, Mercury, Mars and Venus, the Interior Planets, that will help you to understand better its geodynamical evolution (Planetary Geophysics).

Best wishes, Mario E. Sigismondi

Thanks Mr. Mario E. Sigismondi. That's a more elaborate and accurate description of gravitational admittance. Much appreciated.