The global rotation of solar activity structuresD. Heristchi and Z. Mouradian
Observatoire de Paris, LESIA, 92195 Meudon, France
Received 15 February 2008 / Accepted 16 January 2009
Aims. This paper investigates the rotation rate of solar activity from a global point of view, considering daily index or flux, instead of individual structures. It determines the rotation rate variations inside the cycle by two-year sequences and the comprehensive study of the cycle.
Methods. The method consists of harmonic analysis of series of daily monitoring of solar activity. One is the sunspot number covering cycles 9 to 23 (over 157 years) and the second the flux of the corona at 2800 MHz from cycle 19 to 25 (over 53 years). These long series were analysed by the maximum entropy method for the measurement of rotation frequency.
Results. The findings displayed in this paper are: i) sunspots and coronal flux show the same global rotation rates; ii) the solar rotation unfolding during the cycle is complex, without any systematic pattern; iii) the analysis of cyclic solar activity rotation leads to variation of the rotation rate with a period of 52.4 years; iv) the present result supports the existence of high-level cycles made of five eleven-year cycles; the global rotation rate also has this periodicity; v) no asymmetry was found in the northern and southern hemisphere rotation rates.
Key words: Sun: rotation -- Sun: sunspots -- Sun: corona -- Sun: activity
© ESO 2009