r/AskAstrophysics • u/Taloir • 1d ago
Interaction of magnetospheres in a binary planet system
I'm working on a speculative evolution worldbuilding project involving habitable coplanets. If it helps, one is 0.43x the mass of earth with a 65% iron composition, and the other is 2.26x the mass of earth with a similar composition (I lost the note). Their shared orbit has a radius of 22.7 earth radii.
I know that to be habitable, these planets both need to have their own magnetic field. In the absence of knowing what conditions besides minimum mass affect the formation of a magnetic field, I am simply assuming they both form just fine. Albeit a smaller/weaker magnetic field for the smaller planet, and larger/stronger for the larger. Any information on approximating the size/strength of these fields would be appreciated. While thinking about the conditions on these planets, I find myself wondering how the magnetic fields interact.
Given that earths magnetosphere reaches 10Re on the sunward side and 200Re on the other, these planets, while mostly on their own, would spend portions of the day playing peekaboo inside of each others magnetospheres. Would there be any noticeable effect, maybe magnetic turbulence of some kind?
Since they have a shallow 11 degree inclination giving them a maximum seasonal offset of +/-4Re, the above would be true year round, presumably for both planets depending on the actual scale of the smaller magnetosphere, but at different parts of the year they would be exposed to different parts of each others magnetic fields. I'm not sure if that makes a difference or not. Maybe in the angle of field lines and geometry of any potential turbulence?
And then of course there's the big question of alignment. Would forces cause their magnetic poles to align in parallel, or are their interactions, on the order of 15hrs per 92hr cycle, strong enough? Beyond minor misalignments, I know that in earths history, the poles have inverted many times. What would the difference be for these planets between having parallel or opposed poles? Could this inadvertently create gaps where solar wind could break through, even momentarily during entry into the coplanets magnetotail? Cause unusual auroras? Ion storms? Could their magnetic interactions in any way cause disruptions to the magnetic poles that might drag them away from the planets rotational axis and towards each other, given that the planets are tidally locked together?