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We use local stratified shearing-box simulations with magnetic field-alignedthermal conduction to study an idealized model of the coupling between a cold,radiatively efficient accretion disc, and an overlying, hot, two-temperaturecorona. Evaporation of a cold disc by conduction from the hot corona has beenproposed as a means of mediating the soft-to-hard state transitions observed inX-ray binary systems. We model the coronal plasma in our local disc patch as anMHD fluid subject to both free-streaming ion conduction and a parameterizedcooling function that captures the collisional transfer of energy from hot ionsto colder, rapidly cooling leptons. In all of our models, independent of theinitial net vertical magnetic flux (NF) threading the disc, we find no evidenceof disc evaporation. The ion heat flux into the disc is radiated away beforeconduction can heat the disc's surface layers. When an initial NF is present,steady-state temperature, density, and outflow velocities in our model coronaeare unaffected by conduction. Instead of facilitating disc evaporation, thermalconduction is more likely to feed the disc with plasma condensing out of thecorona, particularly in flows without NF. Our work indicates that uncertaintiesin the amount of NF threading the disc hold far greater influence over whetheror not the disc will evaporate into a radiatively inefficient accretion flowcompared to thermal conduction. We speculate that a change in net flux mediatesdisc truncation/evaporation.

Local models of two-temperature accretion disc coronae. II. Ion thermal conduction and the absence of disc evaporation