Proxima Centauri b

[radtech497]

For Proxima b (the real one) to be resonance-locked, a'la Mercury, it would need to be influenced gravitationally by a Jovian-sized planet orbiting farther out in the Proxima system. Such a planet would likely have been detected by now, so in its absence, Proxima b is tidally locked to its star. Insofar as the planet's magnetic field is concerned, it probably has an internally-generated field perhaps 1% as strong as the one generated by Earth; however, the magnetic field generated by convection within and throughout Proxima Centauri is probably several orders of magnitude stronger and may even envelop the planet as it orbits the star. In such a case, rather than deflecting flares, there may be occasions when flares are directed to the planet by magnetic field lines. Which tends to ionize and remove whatever atmosphere may be present.

All in all, my vote is for an airless (or very nearly so) analogue of Twilight.

Radtech497