Does the core convective dipole align with rotation?

Jun 4, 2022 08:11 · 302 words · 2 minute read astronomy science research

I sometimes have research ideas that I think are cool, but that don’t make sense for me to pursue. I generally just make a note of them and move on. This is the ninth post in a series describing some of the ideas I’ve accumulated.

Does the core convective dipole align with rotation?

What’s the idea?

I’m struggling to find a reference, but a recent result out of convection simulations in fully spherical domains is that the dominant flow pattern is a dipole (e.g. a flow that runs right through the center of the domain). This may have an answer already, but I’d like to know if that dipole aligns with the rotation axis, and/or how the dipole flow interacts with rotation as a function of rotation rate.

Why is this interesting?

I don’t know if there’s a direct observational consequence to the dipolar flow aligning with the rotation axis (though perhaps in the distribution of g-modes observed at the surfaces of early-type stars?), but I do think it’s an intrinsically interesting fluid mechanics question.

How can I get started?

I’d start by just asking Daniel Lecoanet or Evan Anders, who I know have worked on dipolar flows. It’s entirely possible there’s a known answer here, or that they have data that can be post-processed to find an answer.

If there isn’t, the best approach is probably to just run some simulations of rotating, fully convective domains (probably in [Dedalus](Does the core convective dipole align with rotation), as that supports fully spherical domains) and see what happens.

My guess is that in the limit of rapid rotation the dipole disappears and is replaced by Taylor columns. In the limit of slow rotation I’d expect the dipole to align weakly on expectation (e.g. it drifts around, but spends more time aligned than not).

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