Solar dynamo, activity cycle and composition

5 problems

• Resolve the conflict between solar abundances and helioseismology

  Contested

  Measurements of the Sun's surface composition give less carbon, oxygen and other heavy elements than the Sun's internal sound waves imply.

• Why do simulated solar convection speeds exceed helioseismic limits?

  Contested

  Computer models of the Sun's churning outer layer predict large-scale flows much faster than sound waves inside the Sun appear to allow, and models with solar parameters tend to rotate the wrong way at the equator.

• Predict the amplitude and timing of solar cycle 26

  Open

  Space weather depends on how active the next solar cycle will be, and past forecasts have often missed.

• Where and how does the solar dynamo generate the toroidal field?

  Open

  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.

• What causes grand minima such as the Maunder Minimum?

  Open

  From about 1645 to 1715 sunspots nearly vanished, and radioactive isotopes in tree rings and ice show many such quiet spells; whether they come from random noise in the dynamo or from a deterministic switch is unknown.