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

Differential Rotation of the Solar Chromosphere: A Century-long Perspective from Kodaikanal Solar Observatory Ca ii K Data

“…In addition to these, recent studies conducted by Li et al (2020) and Xu et al (2020), utilizing data in He I and Mg II lines, reported a faster rotation of the chromosphere. Subsequently, many have extended their observations to higher layers of the solar atmosphere (Brajša et al 2004;Chandra et al 2010;Li et al 2019;Sharma et al 2020;Zhang et al 2023) and employed alternative methods, including the tracing of coronal bright points (Simon & Noyes 1972;Brajša et al 2004;Hara 2009), as well as the Lomb-Scargle periodogram analysis (Li et al 2019) and autocorrelation method (Chandra et al 2010;Sharma et al 2020;Zhang et al 2023). The outcomes from these studies also suggest the faster rotation of the higher solar atmosphere compared to the photosphere.…”

The Non-Thermal Radio Emissions of the Solar Transition Region and the Proposal of an Observational Regime

“…Take the Sun as an example. Figure 1 shows that the solar transition region is a very thin layer with a thickness of only a few hundred km and a height of a few thousand km (from 0.14 Mm to 5.7 Mm, depending on observations at different wavelengths [1]); it sits above the solar photospheric surface and is accompanied by complex motions [1,2]. It separates the colder, partially ionized, and frequently collisional chromosphere from the very hot, fully ionized, and collisionless corona.…”