Long-term variations of the coronal rotation and solar activity

Abstract

Recently, Chandra and Vats have obtained the yearly period length of the solar coronal rotation cycle by analysing the daily adjusted solar radio flux at the 10.7‐cm wavelength for the years 1947–2009. In this paper, we use the time series (series I) of the yearly period length to investigate the long‐term variation of the rotation of radio emission corona, and we find a weak decreasing trend in the time series. We use the empirical mode decomposition to decompose both the yearly mean value (series II) of the solar radio flux at the 10.7‐cm wavelength and series I into different periodical components. There is a secular trend for each of the two series, and we find a negative correlation in the two trends. The decomposed 11‐yr‐cycle components of the two series show different and complicated periods and there is a phase relation between them. We investigate the cycle‐related variation of the coronal rotation length, and we find that there is no Schwable cycle of statistical significance for the long‐term variation of the rotation cycle length.

Systematic regularity of solar coronal rotation during the time interval 1939–2019

“…They found that the coronal rotation period varies with the solar cycle phase, and the rotation period is relatively longer around the minimum year of a solar cycle. Interestingly, they found the coronal rotation variation is related to the 11-year Schwabe cycle, which is disagreement with the result obtained by and Li et al (2012). In addition, the variability of fractal dimension of solar radio flux at different frequencies is also studied by Vats et al (1997) and Bhatt et al (2018), and the main conclusion is that the fractal dimension increases with increasing frequency, i.e.…”

“…According to the statistical analyses of solar radio flux at 2.8 GHz, found that the temporal variation of rotation period does not have any systematic periodicity around 11 years, and there is either not or weak correlation between coronal rotation and solar activity. Later, Li et al (2012) also studied the cycle-related variation of coronal rotation period, and they claimed that there is no 11-year periodicity for the secular variation of rotation period length. However, Xie et al (2017b) restudied the temporal variation of coronal rotation based on the continuous wavelet transform and auto-correlation analysis, they thought that the long-term variation of coronal rotation period should be related to the 11-year Schwabe cycle, because a periodicity of 10.3 years is detected from the smoothed coronal rotation period.…”

“…Using the 10.7 cm solar radio emission data for the time interval 1947-2009 found that sidereal coronal rotation period varies from 19.0 days to 29.5 days with an average of 24.3 days, and a 22-year component (which might be related to the 22-year Hale magnetic cycle or magnetic field reversal) exists in the long-term rotation variation. Based on their analysis results, Li et al (2012) investigated the long-term variation of the coronal rotation of radio emission, and found a weak decreasing trend in the coronal rotation period.…”

Rotation Rates of Coronal Holes and Their Probable Anchoring Depths

“…The rotation rate of the interior and the surface are coupled with the rotation rate of the solar atmosphere, especially the corona. Although there is a general consensus regarding the interior rotation as inferred from helioseismology (Dalsgaard & Schou 1988;Thompson et al 1996Thompson et al , 2003 and references therein; Antia et al 1998;Howe 2009;Antia & Basu 2010), surface rotation rates as derived from sunspots (Newton & Nunn 1951;Howard et al 1984;Balthasar et al 1986;Shivaraman et al 1993;Javaraiah 2003), Doppler velocity (Howard & Harvey 1970;Howard & La Bonte 1980;Ulrich et al 1988;Snodgrass & Ulrich 1990), and magnetic activity features (Wilcox & Howard 1970;Snodgrass 1983;Komm et al 1993), there is no such consensus (see also Li et al 2012) on the magnitude and form of the rotation law for features in the corona.…”

Elimination of long‐term variations from chaotic light curves

“…It is rarely applied in the field of astronomy; however, it showed up in recent studies of solar activity (e.g. Vecchio et al 2012;Li et al 2012). The decomposition is based on the local characteristic time scale of the data and results in a finite number of intrinsic mode functions (IMFs).…”