content 19-July-2018 19:08:25

Solar Orbiter top science questions: #4 How does the solar dynamo work and drive connections between the Sun and the heliosphere?

The Sun's magnetic field dominates the solar atmosphere. It produces all the observed energetic phenomena, and displays an 11-year activity cycle. Despite notable advances in our knowledge and understanding of solar magnetism using observations from the Ulysses, SOHO, and Hinode missions - and recent theoretical models and numerical simulations – the details of the so-called "solar dynamo" processes that power the Sun's magnetic activity cycle are not yet fully understood.

The Sun's global magnetic field is generated by a dynamo generally believed to be seated in the tachocline, the shear layer at the base of the convection zone. According to flux-transport dynamo models, meridional circulation and other near-surface flows transport magnetic flux from decaying active regions to the poles. There subduction carries it to the tachocline to be reprocessed for the next cycle.

A key objective of the Solar Orbiter mission is to measure and characterize the flows that transport the solar magnetic fields: complex near-surface flows, the meridional flow, and the differential rotation at all latitudes and radii. We need detailed knowledge of magnetic flux transport near the poles to understand the solar dynamo and the regular polarity reversal of the global magnetic field. Solar Orbiter's imaging of the properties and dynamics of the polar region during the out-of-the-ecliptic phase of the mission (reaching heliographic latitudes of 25° during the nominal mission and as high as 34° during the extended mission) will provide vital new constraints for models of the solar dynamo.

Last Update: 10 December 2012

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