#### Linear adiabatic wave equation

- Favors deep, thin cells
- Isothermal case: pressure scale height as length scale

#### Linear non-adiabatic wave equation (including radiation)

- The is a horizontal scale with maximum growth rate
- Mode with maximum growth rate smaller than granules (Böhm, 1963)
- New-born downdrafts go through linear phase (and are rather small)
- Positive effect of radiation: vertical: convective instability enhanced
- Negative effect of radiation: horizontal: temperature/density fluctuations suppressed