Height structure

Hydrostatic and gravity equations

The atmosphere is assumed to be hydrostatically supported.

The radius at each pressure level is obtained by integrating from the surface upwards using a fourth order Runge-Kutta method [36]. This solves the coupled system:

\[\frac{dr}{dp} = -\frac{1}{\rho a}\]

\[\frac{dg}{dr} = -\frac{G M(r)}{r^2}\]

\[a = g - r ( 2 \pi \cos(\theta) / d )^2\]

where $r$ is radial distance from planet centre, $p$ is pressure, $\rho$ is density, $g$ is local gravitational acceleration, $G$ is the gravitational constant, $M(r)$ is the mass enclosed within radius $r$, $\theta$ is latitude, and $d$ is the planet's axial rotation period (day length). This includes self-gravitational attraction, and makes AGNI applicable as an atmospheric structure model.

Densities are evaluated using the scheme described in Gas densities.

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