ASTRO
In the literature: open
Where and how does the solar dynamo generate the toroidal field?
In plain words
The Sun's magnetic cycle comes from a dynamo (gas motions regenerating the magnetic field), but whether it operates near the bottom of the convection zone or throughout it is unknown.
Precise statement
Determine whether the solar cycle is a Babcock-Leighton flux-transport dynamo with toroidal (east-west) field generated and stored in the tachocline ($r \sim 0.7\,R_{\mathrm{sun}}$) or a distributed dynamo in the convection zone. Answer: a model reproducing the butterfly diagram, the 22-year magnetic cycle period, polar-field reversal and helioseismic flows.
What would settle it
Helioseismic detection of the toroidal field or its flow signatures at depth, together with a simulation reproducing the cycle at solar luminosity and rotation.