Admittance (geophysics)

In geophysics, admittance describes the small effects of atmospheric pressure on earth gravity. Studies have also been carried out regarding the gravity of Venus.^[1] Admittance in geophysics takes atmospheric pressure as the input and measures small changes in the gravitational field as the output. Geophysics admittance is commonly measured in μGal/mbar. These units convert according to 1 Gal = 0.01 m/s² and 1 bar = 100 kPa, so in SI units the measurement would be in units of;

${\frac {\mathrm {m} /\mathrm {s} ^{2}}{\mathrm {Pa} }}$ or ${\frac {\mathrm {m} /\mathrm {s} ^{2}}{\mathrm {N} /\mathrm {m} ^{2}}}$ or ${\frac {\mathrm {m} ^{3}}{\mathrm {N} \cdot \mathrm {s} ^{2}}}$ or, in primary units ${\frac {\mathrm {m} ^{2}}{\mathrm {kg} }}$

However, the relationship is not a straightforward one of proportionality. Rather, an admittance function is described which is time and frequency dependent in a complex way.^[2]

References

↑ Hoogenboom, Trudi (2004). "Admittance survey of type 1 coronae on Venus". Journal of Geophysical Research. 109. doi:10.1029/2003JE002171.
↑ Abd El-Gelil; Pagiatakis; El-Rabbany (July 2006). "Atmospheric Air Density Admittance Function for High Precision Gravity Reduction". Elements: the newsletter of the Canadian Geophysical Union. 24 (2).

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[1] Hoogenboom, Trudi (2004). "Admittance survey of type 1 coronae on Venus". Journal of Geophysical Research. 109. doi:10.1029/2003JE002171.

[2] Abd El-Gelil; Pagiatakis; El-Rabbany (July 2006). "Atmospheric Air Density Admittance Function for High Precision Gravity Reduction". Elements: the newsletter of the Canadian Geophysical Union. 24 (2).