The atmospheres of hot Jupiters and other strongly-forced exoplanets are susceptible to a thermal instability in the presence of ohmic dissipation , weak magnetic drag and strong winds .
The instability occurs in radiatively-dominated atmospheric regions when the ohmic dissipation rate increases with temperature faster than the radiative ( cooling ) rate .
The instability domain covers a specific range of atmospheric pressures and temperatures , typically P \sim 3 – 300 mbar and T \sim 1500 - 2500 K for hot Jupiters , which makes it a candidate mechanism to explain the dayside thermal “ inversions ” inferred for a number of such exoplanets .
The instability is suppressed by high levels of non-thermal photoionization , in possible agreement with a recently established observational trend .
We highlight several shortcomings of the instability treatment presented here .
Understanding the emergence and outcome of the instability , which should result in locally hotter atmospheres with stronger levels of drag , will require global non-linear atmospheric models with adequate MHD prescriptions .