Temporal Variation of the Rotation in the Solar Transition Region

Abstract The temporal variations of solar rotation in the photosphere, chromosphere, and corona have been widely investigated, whereas transition region is rarely studied. Here, we perform a primary study about long-term variation using Ly α irradiance from 1947 February 14 to 2023 20. Correlation techniques are used, main results as follows. (1) sidereal period varies between 22.24 31.49 days, mean 25.50 days for studied time interval 1947–2022. (2) exhibits clear downward trend during 1947–2022, which might be caused by reduced heliospheric pressure weaker global magnetic fields. (3) Significant periodic signal quasi-Schwabe cycle found periods region. (4) cross-correlation sunspot activity corroborates strong correlation with Schwabe cycle. Possible mechanisms responsible these discussed.