Proxima d

The inner planet of the closest stellar system to ours now has more evidence behind it. Kyplanet reports: interactions, with the chromosphere (above the photosphere which is the visible disc). Elsewhere reported: YZ Ceti, and the aging Sol-like HIP 67522.

Besides pretty-much proving that Prox d even exists, which I didn't rate obvious three/four years ago, we get some constraints on what d is. At M sin i of 0.26 M_⊕ it is rocky, with a magnetic field. The field isn't well constrained except that it's enormous. The sucker's enough to raise flares on a red dwarf. It's much greater than ours on Earth and might even be superJovian although Kyplanet doubts this.

Among the constraints we don't got, besides planetary inclination, would be a map of Prox' magnetic field. Zeeman Doppler Imaging has mapped such field for YZ Ceti - at 3.6pc: a sun's flares coincide with exoplanet crossings of the Alfvén surface as the planet orbit approaches the stellar magnetic equator. I suspect we can measure, by this, both the inclination of the stellar rotation relative to us; and that of the planet's orbit relative to the star.

Prox is closer us at 1.302pc. So that's a tool I'd suggest for the Prox team.

In addition: if some better-constrained nearby planets, like, oh, TRAPPIST-1 b, are not raising flares: is this because they are insufficiently inclined against their stars? I think resonant systems like this one might not be.

As for Prox b, this may have a magnetic field too. It's too small and far to be inducing flares itself but the d-induced flares seem modulated by... something. The planet b is bigger than d so if d held onto a dynamo, why not b. Kyplanet is careful here to note that some of the outside interference might not come from b but from an "e" between d and b, or a retrograde capture inward of d (I find this unlikely).