The 154 day periodicity in the Sun was first reported on gamma-ray flares (Rieger et al., 1984). Later the same periodicity has been found in many other paremeters related to Sun and solar wind/IMF, although it does not seem to be a persistent periodicity, and the exact period varies between 140 and 170 days. For example, Cane et al. (1998) found a 153 day periodicity in IMF strength for solar maximum years 1978-1982, but not for the preceding or subsequent solar cycles. Variables showing ~154 day periodicity:

Variable

Reference

Flare related

Rieger et al., 1984; Bai and Cliver, 1990; Bai and Sturrock, 1993

Active region parameters (sunspots areas etc.)

Lean and Brueckner, 1989; Lean, 1990

Solar F10.7 flux

Lean and Brueckner, 1989

IMF strength and solar wind velocity

Cane et al., 1998

References