Events

COFFIES is supporting the Heliophysics Big Year! NASA’s Heliophysics Big Year (HBY) is a global celebration of solar science and the Sun’s influence on Earth and the entire solar system. The HBY began in October 2023 with the annular eclipse and lasts until December 2024 with the PSP Perihelion! Each month of the big year has a particular outreach theme, which you can find listed in this article.

The theme for September is “Bonus Science”! The Heliophysics Big Year isn’t over yet, and this month will explore unexpected heliophysics discoveries and connections to other scientific divisions.

The tachocline is the most easily detected shear layer inside the Sun. Many dynamo theories rely on this layer to generate and strengthen magnetic fields that are the root of the solar cycle. If indeed the tachocline is responsible for the changing magnetic fields in the Sun, one could expect that the tachocline varies on solar-cycle timescales. In fact, changes in the tachocline properties could distinguish between dynamo models of the Sun.

We characterize the tachocline with three properties, the difference in the rotation rate between either side of the tachocline (the “jump”), the position corresponding to the mid-point of the change in rotation (the “position”) and the extent in radius (the “width”) over which the transition occurs. The change with time of the jump has been seen earlier.

We have used solar oscillation frequency splittings obtained over solar cycles 23, 24, and the rising phase of solar cycle 25 to investigate whether the tachocline properties, in particular the position and the width show any time variation. Using splittings obtained with time series of different lengths, we show that there is indeed a change in the position and width of the tachocline with time.

In this talk, I will walk the audience through the tachocline model that we used, how we determined the tachocline properties and the results that we obtained.

Watch the recording.