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We present a numerical study of turbulence and dynamo action in stratifiedshearing boxes with zero mean magnetic flux. We assume that the fluid obeys theperfect gas law and has finite (constant) thermal diffusivity. The calculationsbegin from an isothermal state spanning three scale heights above and below themid-plane. After a long transient the layers settle to a stationary state inwhich thermal losses out of the boundaries are balanced by dissipative heating.We identify two regimes. A conductive regime in which the heat is transportedmostly by conduction and the density decreases with height. In the limit oflarge thermal diffusivity this regime resembles the more familiar isothermalcase. Another, the convective regime, observed at smaller values of the thermaldiffusivity, in which the layer becomes unstable to overturning motions, theheat is carried mostly by advection and the density becomes nearly constantthroughout the layer. In this latter constant-density regime we observeevidence for large-scale dynamo action leading to a substantial increase intransport efficiency relative to the conductive cases.

Magnetorotational turbulence in stratified shearing boxes with perfect gas equation of state and finite thermal diffusivity